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NNadir

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Evaluating the Performance of Micro-Encapsulated CO2 Sorbents during CO2 Absorption and Regeneration

The paper I'll discuss in this text is this one: Evaluating the Performance of Micro-Encapsulated CO2 Sorbents during CO2 Absorption and Regeneration Cycling (Joshuah K. Stolaroff et al Environ. Sci. Technol., 2019, 53 (5), pp 2926–2936)

One of the co-authors of this paper is Dr. Joan Brennecke, of the University of Notre Dame. Over a year back, I posted a link to one of her lectures at Princeton University on the subject of phase change ionic liquids for the capture of carbon dioxide:

On the Solubility of Carbon Dioxide in Ionic Liquids.

More recently, I discussed a class of "ionic liquids," these are salts that are liquids at room temperature, most often composed of organic cations and anions, although sometimes one of the ions is inorganic in nature - a common example being the hexafluorophosphonium anion, that was being utilized for the recovery of precious metals from spent automotive catalytic converters:

Ionic Liquid Based Separation of Precious Metals from Spent Automotive Catalytic Converters.

It is a remarkable reflection on the flexibility of ionic liquids that the cation used to recover palladium and rhodium from automotive catalysts is similar to that utilized to capture carbon dioxide. The carbon dioxide capture phase change ionic liquids are designated IL NDIL0309, and IL NDIL0230. The cations in these species are tetralkyl phosphonium ions, as they are in the catalytic metal capturing, although the anions differ, in the later case being chloride ion, and in the former, imide type anions of aromatic species.

There is also a discussion of CO2-BOLs (CO2 Binding Organic Liquids) and a cyclic organic tetramine known as "cyclen" (1,4,7,10-tetraazacyclododecane).

The idea in the paper is to encapsulate these agents to improve their performance.

From the introduction to the paper:

Global carbon dioxide emissions are projected to continue increasing in the near term, with coal-consuming countries such as China and India contributing to the expected growth over the next several years.(1) The rate of increase in anthropogenic CO2 emissions more than doubled in the period from 2000–2014, to 2.5–2.7% per annum, relative to the 1.1% per annum increase in the 1990–1999 period.(2,3) The concentration of CO2 in the atmosphere now exceeds 400 ppm, the highest it has been in 670 000 years.(4) The increasing global anthropogenic CO2 emissions present a challenge to meet the international target of <2 °C increase in global temperature relative to preindustrial levels. Thus, investigating carbon capture, storage, and utilization strategies is critical to mitigating CO2 emissions and maintaining <2 °C global temperature increase.

Globally, the combustion of fossil fuels accounts for 75% of anthropogenic CO2 emissions.(2) In 2016, 35% of the U.S. energy-related CO2 emissions came from the electric power sector fed by fossil fuels.(5) One strategy for CO2 emission mitigation is postcombustion capture of CO2 from point-sources such as power plants. The conventional approach to CO2 capture from flue gas is amine-scrubbing using aqueous solutions of amines such as monoethanolamine (MEA) or diethanolamine (DEA), which is already used in a number of plants but suffers from high energy demand, mostly to regenerate the amine solvent, as well as degradation of the amine solvent and the formation corrosive degradation products.(6,7) These challenges limit the economic feasibility of postcombustion CO2 capture from powers plants. Therefore, developing novel CO2 sorbents and processes that reduce the energy requirement and/or increase the CO2 absorption rate is a vital area of research to meet CO2 emissions and global temperature goals...


Nothing I say in this post, said with the deepest respect for Dr. Brennecke, should be construed as indicating that I find carbon capture from the "flue gas" of dangerous fossil fuel power plants acceptable. This said, I do regard capture of carbon dioxide from oxyfuel closed combustion of biomass as to be one option to remove carbon dioxide from the atmosphere. Thus the basic technology attracts me, with the expectation that it can be utilized for something else besides putting lipstick on the fossil fuel pig.

I don't believe in "flues" exposing combustion products to the air we breath, but believe strongly that closed combustion is technologically feasible, particularly in light of developments in materials science. This is only possible if we can quantitatively capture carbon dioxide and chemically modify it in useful ways with the effective removal of the gas from our current modern favorite waste dump, the planetary atmosphere.

Anyway, another excerpt from the introduction:

Micro-Encapsulated CO2 Sorbents (MECS) are a recently developed CO2 capture technology that may be an effective strategy for enabling the use and recyclability of advanced solvents, but they have not been rigorously evaluated for practical use within an absorption/regeneration process until now. MECS consist of a CO2-absorbing solvent or slurry encased in spherical, CO2-permeable polymer shells.(15,16) We have demonstrated this technology with carbonates, CO2BOLs, and ionic liquids to achieve increased surface area, resulting in an enhancement of CO2 absorption rates by an order of magnitude relative to a thin film of the solvent.(16) CO2 promoters such as carbonic anhydrase,(17) sarcosine,(18) or zinc(II) cyclen complexes(19,20) may be combined with carbonate solutions in MECS to further increase the rate of CO2 absorption. We have previously explored the addition of zinc(II) cyclen, a mimic of the enzyme carbonic anhydrase that catalyzes CO2 absorption into aqueous solution, to carbonate MECS to enhance the rate of CO2 absorption and found that the capsules reached CO2 saturation 2–3 times faster than carbonate MECS without cyclen.(15) Here, we rigorously demonstrate successful encapsulation, compare absorption rates and capacities of CO2 at low partial pressure, and evaluate stability of six advanced liquid CO2 solvents within polymer shells: Na2CO3 solution (uncatalyzed, with sarcosine, with cyclen); ionic liquids (task specific ionic liquid NDIL0230, and phase-changing ionic liquid NDIL0309), and a CO2BOL (Koechanol). We build upon our previous encapsulation tests to characterize MECS performance over a wider range of temperatures, CO2 loadings, and absorption/regeneration cycles.


The preparation of MECS is described here:

Encapsulated liquid sorbents for carbon dioxide capture (Jennifer Lewis et al, Nature Communications volume 6, Article number: 6124 (2015))

The experiments herein did not involve actual flue gases, but rather carbon dioxide in the presence of water. The apparatus utilized is shown here:



The caption:

Figure 1. Process diagram of the pressure drop apparatus used to measure CO2 absorption rates as a function of time for all six MECS types.


Pressure drop was followed using the following equation to determine the mass uptake over an hour in this apparatus:



This is obviously derived from the "ideal gas law." Dr. Brennecke is the editor of the Journal of Chemical and Engineering Data where she has set a high (and appropriate) standard for precision and accuracy in data. The ideal gas law is very imprecise, but this can be forgiven here, since probably the paper is intended for qualitative analysis.

Many higher accuracy equations of state for gases exist, either for generalized gases with fitting parameters such as acentric factors for individual gases, the Peng-Robinson equation for example.

Carbon dioxide itself has a very highly precise equation of state known as the Span-Wagner equation:

A New Equation of State for Carbon Dioxide Covering the Fluid Region from the Triple‐Point Temperature to 1100 K at Pressures up to 800 MPa (Roland Span and Wolfgang Wagner Journal of Physical and Chemical Reference Data 25, 1509 (1996); https://doi.org/10.1063/1.555991)

Although modern computers can certainly address the use of cubic equations like Peng Robinson and more complex formulations like Span-Wagner, again, it's probably overkill here.

Using these microencapsulating systems, these carbon dioxide capture agents were evaluated through a number of capture and release cycles. The release, of course, requires heat, one can imagine circumstances where this heat might come from very high temperature devices in a kind of "combined cycle" approach during cool down phases, reducing exergy losses to entropy.

The regenerating device is shown here:




The caption:


Figure 2. Process diagram of regeneration in a tube furnace (A), where CO2 was stripped from all six MECS types during preliminary testing. (B) Process diagram of the regeneration apparatus used to strip CO2 using a dry stream of N2 at ∼90 °C during the 10-cycle experiments (MFC = mass flow controller, TC = temperature controller, TI = temperature indicator, CO2 = CO2 sensor, RH = relative humidity sensor, and MFI = mass flow indicator).


Upon the conclusion of these experiments, they were repeated using "simulated coal flue gas"

...We have previously measured the gas permeability of the MECS shell materials to nitrogen and CO2 separately, shown in Table 1, but had not investigated the effect of a mixed gas stream on the gas absorption rate of the MECS until now. The selectivity of a membrane between a pair of gases is given by the following:

(3)

in which PA is the permeability of the more permeable gas, and PB is the permeability of the less permeable gas.(22) In the case of both types of silicone shells used in the MECS, the selectivity for pure CO2 over pure N2 is ∼11, which is on the low end compared to other materials reported in literature.(23,24)Previous research suggests that the presence of nitrogen can reduce CO2 permeability in silicones that have similar molecular structure to the MECS shell materials,(25) which would be detrimental to the rate of CO2 absorption from coal flue gas in which nitrogen makes up ∼75% of the gas stream. In fact, Scholes et al. reported that the CO2/N2 selectivity in PDMS decreased from ∼11 with pure gases to ∼3–4 with a blend of 10% CO2, 90% N2.(26) This indicates that the CO2 absorption rate may be limited by mass transfer of CO2 to the solvent since the selectivity for CO2 is decreased in the presence of N2.


Permeability is related to molar flux, J, by the following:

(4)

where d is the thickness of the membrane, or in this case the shell thickness, and Δp is the pressure difference across the membrane. Combining eq 4 with eq 3, the ratio of fluxes is proportional to the partial pressure gradient across the shell, given by eq 5:

(5)

In order to test whether the CO2 absorption rate was affected by the presence of air, CO2 absorption tests were performed in the pressure drop chamber with 0.1 bar of injected CO2 in both cases and an additional 0.9 bar of ambient atmosphere (79% N2) injected in the case with air. The resulting total gas absorption for these two cases are compared in Figure 3 over the first 10 min. It should be noted that in the case of the experiment with air, the gas absorption includes both air (predominantly N2) and CO2 across the shell material...


The authors expected some variation with air but didn't see it:



The caption:

Figure 3. (A) Gas absorption versus time for uncatalyzed Na2CO3 MECS exposed to 0.1 bar CO2 with and without 0.9 bar air in the pressure drop apparatus at 25 °C. The loading was practically the same in pure CO2 as in CO2 with air. (B) Model calculation of CO2 mole ratio (including CO2(aq) and HCO3– ions) of CO2 and N2 in MECS (shell and core) in 0.1 bar CO2 and 0.9 bar N2 condition as a function of CO2 loading capacity. The ratio quickly approaches 100%, meaning N2 contribution to the flux and loading may be assumed to be negligible.


There is some discussion of the reasons for this.

Some of the CO2-BOLs did not stay encapsulated. This was the case for a rather interesting material known as koechanol (1-((1,3-dimethylimidazolidin-2-ylidene)amin)propan-2-ol) the synthesis of which is described here:

Low viscosity alkanolguanidine and alkanolamidine liquids for CO2 capture (David J. Heldebrant et al, RSC Adv., 2013, 3, 566-572)

Here's a photograph of the leaking koecheanol along with the effect of the leaking on cycling the microcapsules through capture and regeneration cycles:



The caption:

Figure 4. Microscope images of Koechanol CO2BOL MECS after exposure to desiccant for 4 days before cycling, with visible droplets on the shell surface. The mass of Koechanol MECS decreases dramatically with each absorption/regeneration cycle (right).


The MECS were tested with some test solutions, "promoters" without the ionic liquids or CO2-BOLs.




The caption:

Figure 5. Comparison of CO2 absorption vs time for the three types of Na2CO3 MECS: uncatalyzed MECS, MECS with sarcosine promoter, and MECS with cyclen promoter. All of these MECS contained 17 wt % Na2CO3 and were soaked in 17 wt % Na2CO3 solution prior to testing. All data were collected in the pressure drop at room temperature (25 °C). (A) CO2 absorption rate normalized by MECS mass and initial pressure, (B) CO2 loading normalized by MECS mass.


Sarcosine, which is the N-methylated analogue of the natural (and simplest) amino acid glycine, leaked from the capsules and was not pursued.

The comparison for the sodium carbonate and cyclen systems was then made with the ionic liquids:



The caption:

Figure 6. Comparison of CO2 absorption rate over the first 10 min by MECS with (A) Na2CO3-cyclen, (B) NDIL0309, and (C) NDIL0230, and at 25, 40, and 60 °C. (D) The bar graph displays CO2 loading after 30 min (left axis), and the markers represent the percent of stoichiometric capacity (right axis) of each solvent.


Not only do the ionic liquids capture more carbon dioxide per unit mass (stoichiometric capacity), but they capture it faster:




The caption:

Figure 7. Comparison of CO2 loading vs time for three MECS (NDIL0230, NDIL0309 and Na2CO3-cyclen) during Cycle 0 at 25 °C and 0.1 bar CO2. CO2 loading is presented in terms of mol/kg solvent (left) and as a percentage of total stoichiometric capacity (right).


They hold up well through multiple cycles, a very, very, very, very important issue for these types of systems.



The caption:

Figure 8. Comparison of CO2 absorbed by three MECS types (NDIL0230, NDIL0309 and Na2CO3 w/cyclen) across 10 cycles. CO2 loading capacities are the cumulative CO2 absorbed (per kg solvent and initial pressure) after the MECS have been exposed to CO2 in the pressure drop apparatus for 30 min. (A) CO2 loading is presented in terms of mol/kg. (B) The mass of the MECS is shown over 10 cycles (bars, left axis) and CO2 loading is shown as a percentage of total stoichiometric capacity (lines, right axis).


Some microscope photographs of the microcapsules, before and after:




The caption:

Figure 9. Microscope images of the three final candidate capsules taken before (top) and after (bottom) ten absorption/desorption cycles: (A) Na2CO3 before cycling; (B) NDIL0309 before cycling; (C) NDIL0230 before cycling; (D) Na2CO3 after ten cycles; (E) NDIL0309 after ten cycles; and (F) NDIL0230 after ten cycles. The scale bar for each image is 500 μm.


The authors conclude:

Overall, across the characteristics tested here—absorption rate, capacity, and cyclic stability—the ionic liquid MECS appear to be a potential competitor to aqueous amines. The major challenge to these MECS are common to solid sorbents: the need for a process configuration that is similar in capital cost and energy efficiency to aqueous solvent systems. Further work is needed on material fabrication and testing at larger scale to establish the viability of IL MECS.



While I do not believe the paper under discussion here is open sourced, there are two excellent government reports related to her DOE grants that are. They are here:

Hybrid Encapsulated Ionic Liquids for Post-Combustion Carbon Dioxide (CO 2) Capture 1337563

Hybrid Encapsulated Ionic Liquids for Post-Combustion Carbon Dioxide (CO 2) Capture 1406897

Again, I am against coal combustion, petroleum combustion and gas combustion, but I believe that biomass combustion and/or supercritical water or supercritical carbon dioxide oxidation does represent a path forward for capturing carbon dioxide from the atmosphere, and should not be overlooked, even if the combustion of biomass, as practiced now, is responsible for slightly less than half of the seven million air pollution deaths now taking place while many of us whine about Fukushima.

This kind of technology is potentially of huge importance.

I wish you a very pleasant Sunday evening.








Integrated Pest Management to Boost Dragon Fruit Production in Viet Nam

I am on the International Atomic Energy Agency's mailing list, and this note was in my email this morning:

Integrated Pest Management to Boost Dragon Fruit Production in Viet Nam

Some excerpts from the open sourced link:

There is a reason why dragon fruit is considered a rich and famous fruit in Viet Nam: it is exported to 40 countries and return from dragon fruit production is several times higher than from rice production.

In Binh Thuan province, around 29 500 hectares are dedicated to growing the fruit, with a production of nearly 600 000 tonnes last year, and its Department of Agriculture and Rural Development plans to increase that by 2020. However, this plan may be hindered by formidable pests capable of decimating dragon fruit crops: fruit flies.

“Dragon fruit is a favourite crop in Viet Nam because farmers are aware of its potential to earn them a steady income,” said Hien Thanh Thi Nguyen, Deputy Head of the Entomology Division at Viet Nam's Plant Protection Research Institute. “Unlike many other fruits that are seasonal, dragon fruit can be cultivated all year round and each crop season lasts only two and a half months, so it has great economic importance. The fruit is very important for the province’s economy, but the fruit flies are a big problem for this area.”

Therefore, the Plant Protection Research Institute, along with staff from the Agriculture and Rural Development Department of Binh Thuan province, teamed up with the IAEA and the Food and Agriculture Organization of the United Nations (FAO) in a pilot project to test the effectiveness of implementing an integrated pest management approach, including a form of insect pest control known as the Sterile Insect Technique (SIT). Using this technique, fruit flies are mass-produced and then sterilized using ionizing radiation before being released into the environment to mate with wild flies, producing no offspring.


The technique is designed to reduce the fruit fly population by releasing sterilized animals into the area where they mate with fertile animals (who mate only once) resulting in a failure to reproduce.

The technique can be utilized either to eliminate or greatly reduce dependence on pesticides.

The program met resistance, until authorities were able to educate the farmers:

Getting to the point of SIT implementation has not been easy, due to limited knowledge of the technique within the local offices and resistance from dragon fruit farmers, who did not at first understand how releasing more flies into the fields would ultimately reduce the population.

“They didn’t understand that the fruit fly would be sterilized,” said Hien. “They would say, ‘We have so many flies already, how can we combat this by bringing in more flies?’ So, we had to change the way we approached farmers about this with a series of trainings, leaflets and television advertisements, and it took about two years before they started thinking that maybe this could help. It’s important because getting the programme to work depends on the farmers in the entire area actively participating in the pest management.”


It appears that the farmers were able to overcome their initial ignorance; I kind of, sorta, after a fashion, wish American anti-nukes were willing to address their ignorance, but that's not likely to happen. (We have a "Nuclear Free" group here at DU, but not a "Fossil Fuel Free" group.) Anti-nukes are very cult like, in the sense that no amount of information can cause them to change their minds.

It is interesting to note that Agent Orange, a persistent chlorinated aromatic compound routinely dumped on Vietnam for defoliation, can be dechlorinated by irradiation, as can many historical chlorinated pesticides, of which DDT is the most famous example.

In many cases there are no other techniques that can or will work.

Sigh...

I wish you a pleasant Sunday afternoon.

A nice little open sourced paper on "Sloshing."

I always like to hear about things at which I never spent much time - or any time - thinking, and to learn more about them.

Recently my son - on his spring break - visited one of the last independent bookstores of which I am aware, and came across a book in the Engineering section called "Sloshing." He found the title amusing and told me about it.

He didn't buy it, but its appearance in an engineering section led me to realize that, "Of course, there is a physics of sloshing."

Late in life, I've become more and more interested in fluid dynamics owing to a growing interest in the behavior of liquid metal nuclear fuels, eutectics of the low melting metals plutonium and neptunium, generally are very dense liquids.

Anyone who has ever handled a large flask of mercury or elemental bromine, can get a quick feel for the potential of forces involved in sloshing. Liquid plutonium is more dense than liquid mercury. The density of mercury is about 13.5 grams/ml; liquid plutonium, depending on temperature, as a density of between 16.0 and 16.7 grams/ml. (cf. L. J. WITTENBERG, D. OFTE, and W. G. ROHR, Properties of Liquid Plutonium (Nuclear Applications Volume 3, 1967 - Issue 9 pp 550-555.)

In addition, I favor liquid metal reactor coolants consisting largely - or entirely - of lead, a very dense metal.

The physics of these liquid metal materials have implications for the strength of materials with which they interact, in particular in events like earthquakes, so it's a very important topic.

Anyway, it's a topic into which I will look further, and a quick Google Scholar search - the way I always begin exposure to a new topic led me to this link to an open sourced paper: Sloshing (Faltensen, O.M. FFALTINSEN. Sloshing. Advances in Mechanics, 2017, 47: 201701)

(There's Japanese text but the paper is in English.)

It has interesting little bits like considering what liquids do in outer space where there is no gravity.

Cool, I think.

If interested, enjoy.

I hope you're having a pleasant Weekend.







A nice map of the areas likely to be most affected by weather extremes.

The rise of weather extreme events can readily documented now that the predicted effects of climate change are now being experienced on a larger and larger scale. It's not going to stop.

I subscribe to the "Carbon Brief" email list. A link therein in recent days pointed to the "Mapping How Climate Change Affects Extreme Weather Around the World."

While some portion of what remains of a putative "Environmental Movement" is devoted to the worship of Elon Musk's cars and other things having no effect whatsoever on climate change, climate change is still real, and the rise of extreme events is also real.

This link may of interest to look at reality, as opposed to religiously repeating mantras about what was popularly predicted by pop environmentalists to work in the 1970's, didn't work, isn't working and won't work.


Mapped: How climate change affects extreme weather around the world

Of course, the destruction caused by these events will never match Fukushima as a tragedy, but still, it might be slightly important. I don't know, you tell me.

Have a nice weekend.

Ionic Liquid Based Separation of Precious Metals from Spent Automotive Catalytic Converters.

The paper I'll discuss in this post is this one: Application of a Novel Phosphonium-Based Ionic Liquid to the Separation of Platinum Group Metals from Automobile Catalyst Leach Liquor (Goto et al, Ind. Eng. Chem. Res., 2019, 58 (9), pp 3845–3852).

Certain elements are considered to be in critical supply. How dire this state of affairs for any particular element is not entirely clear, but it is very clear that most of the world's best ores for some metals have already been mined.

Many periodic tables showing the elements of highest concern are available; my personal favorite is the featuring the logo the scientific organization for which I am a long time proud member, the American Chemical Society. Here it is:



There are some variances in this data, and some means of address for some of the shortages. Some can be recovered from extreme low grade ores. Uranium, for example, can, at a higher price, but not one that precludes its use, recovered from the extremely low grade ore seawater.

I note that the period at most risk, in terms of the percentage of elements at risk is the 5th period. Fourteen of the 18 elements face risks to their supply. One of the elements, technetium, does not occur naturally; all of its isotopes are radioactive. I note that because of the lanthanide contraction, a quantum mechanical physical chemical effect, technetium is a suitable replacement for rhenium.

Rhenium does not appear in this particular version of the periodic table as "endangered" but probably should; it is an extremely rare element, so rare that it was the last non-radioactive natural element to be discovered, in 1923, by Ida Noddack and her husband. The chief use for rhenium is a component of "superalloys," (generally) nickel based alloys that exhibit extreme strength at high temperatures, essential to the operation of jet aircraft and high temperature combined cycle power plants.

All of the elements in period 5 are fission products found in used nuclear fuels, where they are found at various concentrations. Some of these contain significant quantities of radioactive isotopes; the degree to which this is true has to do with the timing of their isolation. It is possible to obtain non-radioactive palladium from used nuclear fuel if one isolates ruthenium promptly after irradiation. In this case the radioactive isotope Ru-106 will decay to non-radioactive (isotopically pure) palladium-106, with a half life of slightly over one year. After 20 years, the ruthenium remaining, a mixture of isotopes 100, 101, 102, 104, and 105 will be essentially non-radioactive and available for use.

Because of the high energy density of nuclear fuels, it is, however, except in special cases, unlikely that fission products can ever approximate major supplies for all of these elements, depending on their demand.

It has been argued that the supplies of the element rhodium in used nuclear fuel will be greater than the supply of the metal in ores within a few decades. (Srinivasan et al, Electrochimica Acta 53 (2008) 2794–2801)

That paper was about a class of solvents that are capturing huge attention, ionic liquids, which are salts that are liquid at temperatures approaching room temperature. In general, with some exceptions, they have organic cations and anions.

So is the paper cited at the outset of this post, although the paper just cited was about nuclear fuels and the one cited at the outset was about recovering metals from automotive catalysts, that is recycling.

In the particular case here, the ionic liquids are tetraalkyl phosphonium based salts.

From the introductory paragraphs:

Platinum group metals (PGMs), which occur naturally along with nickel and copper in minerals such as sperrylite or copperite,1 are of significant technological importance. The worldwide demand for PGMs is also steadily increasing owing to the widespread use of these materials in various applications. Presently, 70% of PGMs are consumed by the automobile industry, primarily as components of autocatalytic converters intended to reduce exhaust pollution.2 However, such catalysts are eventually deactivated, either because of surface coke formation or the loss of active components, and simply become waste materials.3 Spent catalysts are potentially harmful to the environment because of the presence of soluble/leachable organic and inorganic compounds, and so their disposal in landfills is restricted.3−5 In addition, as a result of the scarcity and high value of PGMs, there is an increasing interest in recycling spent catalysts.


The recycling and recovery of spent automobile catalysts has become a growing secondary source of PGMs, and various methods have been developed for this purpose, such as hydrometallurgical or pyrometallurgical processes.4 However, the physical and chemical properties of these metals are very similar and thus they are difficult to separate. Traditional PGM recovery methods involve physical treatments, including acid dissolution, chemical separation and refining,6,7 but have several disadvantages, such as poor selectivity, a high degree of complexity, and numerous recycling streams and refining steps. In contrast, hydrometallurgical leaching followed by solvent extraction offers greater selectivity, a scrubbing step that increases the product purity, and complete removal of metals via multistage extraction steps.8

Ionic liquids (ILs) are salts composed of organic cations and inorganic anions that are liquid at room temperature, and these substances have potential applications to metal extraction due to their unique properties. ILs also tend to have negligible vapor pressure relative to more common organic solvents and their properties can be tuned by varying the cation and anion.10 Hydrophobic ILs are also able to solvate species with a net charge, such as metal complexes,11 and thus can be suitable alternatives to organic solvents in extractions...


For this work, automotive catalysts were crushed, milled with alumina balls, and dissolved in refluxing aqueous hydrochloric acid.

The ionic liquid explored here has the following structure:



The caption:

Figure 1. Molecular structure of P8,8,8,12Cl.


It was used to extract the "leach liquor," the hydrochloric acid solution. Essentially all of the elements in the next graphic are present in solution at this point.



The caption:

Figure 2. Data for the extraction of a model leach liquor with P8,8,8,12Cl. Conditions: Vaq/VIL = 2, time = 8 h, T = 298 K. Concentrations in the model leach liquor (mg L^(−1)) were Pd, 300; Rh, 26.5; Ce, 88; La, 32.1; Pr, 63.4; Ba, 309.5; Al, 3181; Zr, 43.17; Mg, 453.3; and Fe, 26.3.


This shows the effectiveness of the extraction as a function of the concentration of hydrochloric acid used for dissolution.

The next graphic shows the effect of contact time. The speed of contact time can be shortened by multiple extractions over shorter periods, but as this is research, and not production, it is useful to understand this effect purely in terms of time:



The caption:

Figure 3. Effect of contact time on the extraction of metals from the model leach liquor. Conditions: Vaq/VIL = 2, [HCl]aq = 5 mol L−1, T = 298 K. The metal concentrations in the aqueous phase were the same as those provided in the caption to Figure 2.


What is notable here is that palladium has been effectively separated from all the elements except iron and zirconium.

The removal of iron and zirconium from the ionic liquid solution is accomplished by "scrubbing" the solvent with aqueous solutions of salts:



The caption:

Figure 4. Fe scrubbing from loaded P8,8,8,12Cl: (A) results obtained using 0.1 mol L−1 HCl, 0.5 mol L−1 HNO3 and H2SO4, water, and 1.0 mol L−1 Na2SO3 at 323 K; (B) effect of Na2SO3 concentration at 323 K and 30 min; (C) effect of temperature using 1 mol L−1 Na2SO3 at 30 min and Vaq/ VIL = 2.


The spectra show the separation.



Figure 5. UV−visible spectra of (A) iron(III)−chlorocomplexes in P8,8,8,12Cl before and after scrubbing with Na2SO3. Conditions: [HCl]aq = 5 mol L^(−1), Vaq/VIL = 2. Spectra were acquired in ethanol. (B) Iron(II)−phenanthroline complexes from scrubbing solution. Conditions: 1,10- phenanthroline = 0.01 mol L^(−1).

The palladium is stripped from the ionic liquid by extraction with an aqueous solution of thiourea:




The caption:

Figure 6. Stripping of Pd(II) from loaded P8,8,8,12Cl using CS(NH2)2. Conditions: Vaq/VIL = 2 and T = 298 K.


By adjusting the HCl concentration, utilizing the effect shown in figure two, where rhodium is more soluble in the ionic liquid if the acid concentration is 1M, it is possible to recover the rhodium:



The caption:

Figure 7. Extraction of Rh(III) from the raffinate (1 mol L−1 HCl) and stripping of Rh(III) using 5 mol L−1 HCl. Conditions: Vaq/VIL = 2, T = 298 K, time = 5 h.


Overall, the flow chart for the process is here:



Figure 8. Flowchart summarizing the separation and recovery of Pd(II) and Rh(III) from an automobile catalyst leach liquor.


The caption:

Figure 8. Flowchart summarizing the separation and recovery of Pd(II) and Rh(III) from an automobile catalyst leach liquor.


All of the above was based on a simulated acid leachate.

The data below shows the results using real automotive catalysts:



The caption:

Figure 9. Data for the processing of an automobile catalyst leach liquor. (A) Pd extraction from [HCl]aq: 5 mol L−1; time, 10 min. (B) First Fe(III) scrubbing using Na2SO3: 1.2 mol L−1; T, 323 K; time, 30 min. (C) Pd stripping using CS(NH2)2: 1 mol L−1. (D) Rh extraction using [HCl]aq: 1 mol L−1; time, 5 h. (E) Second Fe(III) scrubbing using Na2SO3: 1.2 mol L−1; T, 323 K; time, 30 min. (F) Rh(III) stripping using HCl: 5 mol L−1. Vaq/VIL = 2, T = 298 K.


Hydrophobic ionic liquids are extremely interesting me, particularly as I am interested in the pyroprocessing of used nuclear fuels followed by electrorefining, an area in which ionic liquids hold great potential.

I note that with the exception of magnesium, aluminum and iron, all of the elements found in these automotive catalysts are also found extensively in used nuclear fuels. Aluminum is a constituent of some legacy "nuclear wastes" such as those found at the Hanford reservation, and my own preference for future nuclear fuels might well include plutonium/iron eutectic liquid fuels, which, in use, will accumulate these fission products. Magnesium is found in historic "Magnox" fuels utilized in British nuclear reactors.

I personally would prefer a world in which, to the extent that self propelled vehicles are acceptable - they are not acceptable tools of mass distribution in my view inasmuch as no bandaids can make them sustainable - they would not actually need much in the way of catalysts, something that is possible with certain kinds of fuels, in particular simple liquifiable gases like dimethyl ether.

However, it would be useful for our greatly screwed children, grandchildren and great^(n) grandchildren when they are forced to pick through our garbage, as we have left them very little, to recover valuable elements from our dead automotive catalysts.

It's an interesting paper.

Have a nice day tomorrow.

Climate Induced Risks of Hydrological Failure of Major California Dams.

The paper I'll discuss in this post is this one: Climate‐Induced Changes in the Risk of Hydrological Failure of Major Dams in California (Mallakpour, I., AghaKouchak, A., & Sadegh, M. (2019).
Geophysical Research Letters, 46. https://doi.org/10.1029/2018GL081888)

Air pollution is the greatest energy disaster of all time: an ongoing, continuous disaster, one completely accepted, but clearly the worst of all time. In the last twenty years it has led to the deaths of approximately 140 million people, not that this is remotely as interesting as say, Fukushima, where 20,000 people died from seawater, and perhaps a few people from radiation exposure.

Probably the second worst energy disaster of all time is the Banqiao dam disaster in 1975. Depending on who you ask, it killed between 170,000 and 250,000 people; the exact numbers are not known and probably never will be known.

The Forgotten Legacy of the Banqiao Dam Collapse

Similar dam collapses in the United States have been narrowly avoided; in 1983 the Glen Canyon Dam was saved when engineers went out to a local hardware store to hold back the collapse by buying plywood. I'm serious.

I wrote about that here: A Tale of Two Centimeters: The Near Collapse of the Colorado River Dam System in 1983.

Apparently a book on the subject has been written: How 4 Feet of Plywood Saved the Grand Canyon.

Recently there was a television show on Engineering Failures that I watched on the Oroville Dam, which came close to collapse in 2017, when a concrete spillway collapsed forcing the use of a secondary dirt spillway that was severely eroded and in danger of failure.

Thankfully, the worst didn't happen.

The paper cited at the outset of this post indicates that climate change may be overwhelming the design parameters on which dams were historically based.

From the introductory text:

In February 2017, a series of extreme precipitation events generated floods that led to evacuation of about 200,000 residents, economic damages of around $1.5 billion, and five fatalities over northern and central California (National Climate Data Center, 2017; Vahedifard et al., 2017). One of the notable impacts of this incident, which occurred after 5 years of an unduly prolonged drought (e.g., AghaKouchak et al., 2014), was the Oroville Dam spillway failure. The structural failure was triggered by extreme flows released through the spillway that eroded the concrete lining and created a hole in the main spillway (Vahedifard et al., 2017). Dams are constructed to manage the temporal and spatial variation in the natural regime of water resources (e.g., Ehsani et al., 2017; Ho et al., 2017) and provide several societal benefits (e.g., flood control, hydropower energy, water for irrigation, livestock, and drinking; Federal Emergency Management Agency, 2016). The American Society of Civil Engineers' report card in 2017, however, estimated that the average age of dams in the United States is about 59 years with an overall score of “D,” which suggests many dams are in a poor to fair state (American Society of Civil Engineers, 2017). Majority of these dams were constructed in the previous century with limited observation data and with flood hazard assessments based on the natural water regime at the time (Ho et al., 2017). Therefore, their construction did not incorporate the current and possible future changes in the hydrological condition. Consequently, the original dam design does not reliably account for changes in potential exposure of these important infrastructure assets to flood hazards in the future (Willis et al., 2016).

Several studies have forewarned of intensification of hydrological cycle under the projected warming climate (e.g., Voss et al., 2002; Wang et al., 2017), which promotes more frequent extreme events, such as heavy precipitation and flood events (e.g., Intergovernmental Panel on Climate Change, 2012; Milly et al., 2005, 2002), and prompts cascading hazards such as wildfire‐precipitation‐flooding (AghaKouchak et al., 2018). In general, air holds higher water vapor capacity in a warmer climate, which in turn can intensify precipitation events and increase flood risk (Allen & Ingram, 2002). Response of streamflow to precipitation depends on different factors, such as spatial distribution of precipitation event, temperature, catchment size, and land use land cover change (Li et al., 2018; Sharma et al., 2018; Wasko & Sharma, 2017). However, potential changes in the intensity and frequency of precipitation events will change flooding hazard (Moftakhari et al., 2017; Sadegh et al., 2018a). Different studies have projected an increasing trend in river flood hazard under a warmer climate condition (Arnell & Gosling, 2016; Dankers et al., 2014; Hirabayashi et al., 2013; Kundzewicz et al., 2014; Mallakpour & Villarini, 2015; Slater & Wilby, 2017; Winsemius et al., 2016), which is anticipated to change failure risks of water infrastructure systems...


The authors look at models for rainfall patterns in California under the effects of climate change. The models are designed to not look at overall rainfall, but rather include a temporal component, that is the number of extreme events, large amounts of rainfall over a short period.

(The Banqaio dam system was destroyed by just such an event, a typhoon that struck China.)

In this study, we use the annual block maximum sampling method to extract the maximum daily value in each year for the simulated routed inflows and gridded runoff. We calculate the annual maximum flow for each of the 10 models and two RCPs for two periods: the historical period (1950–2005) and the projected period (2020–2099). Then, for each of the routed inflows and gridded runoff pixels, we fit the generalized extreme value (GEV) distribution to estimate the flood frequency distribution. The GEV distribution has been extensively used in the hydroclimatological studies as a statistical model to describe the behavior of extreme events (Coles, 2001; Gilleland & Katz, 2016; Katz et al., 2002; Villarini et al., 2009). We also analyze the best fit, according to maximum likelihood, to the inflows to all major dams using 15 different probability distributions and show that GEV is selected as the superior model for an absolute majority of the cases (Tables S5–S16).


As was recently reviewed by a speaker at a lecture I recently attended, the intensity of extreme events is rising; one can calculate this by taking the average rainfall (or snow fall) of the top 1% of events in a single year, and comparing the same figure in earlier years.

I think most of us have a qualitative sense of this just looking out the window. I know I do.

This is what the authors model:

Finally, we use the “failure probability” concept as a proxy to measure the impacts of future possible changes in hazardous climatic conditions on different dams. The failure probability concept, which quantifies the likelihood of experiencing a flood with a given magnitude at least once within a given design lifetime of a structure, is of interest to the engineering design of hydrological infrastructures (Moftakhari et al., 2017; Read & Vogel, 2015). The failure probability for a specified design lifetime N is given by



where T is return period and FP signifies the probability of exceeding a designed event (xT) at least once in N years. The failure probability of the projected period is compared with that of the historical period in order to provide an indication of the impacts of expected changes in the future flood hazard. Note that hydrological failure probability is related to the flood hazard component of the risk. Physical failure analysis requires additional mechanistic modeling typically used in structural and geotechnical engineering with forcings from hydrological analysis.


The projections for the relative increase and decrease of "100 year floods" in California are shown in the following graphic:



The caption:

Percentage changes between multimodel median of gridded simulated runoff associated with a projected 100‐year flood level under (a) RCP4.5 and (b) RCP8.5 relative to the historical period (1950–2005) over northern and central California. The blue (red) color reveals locations that magnitude of the 100‐year flood projected to increase (decrease) in the future. The color bar shows the percentage difference (%) in the 100‐year flood level in the projection period relative to the historical period.


The "hundred year" flood is a flood with a probability of occurring within one hundred years; however what used to be a hundred year flood could be now a "twenty year" flood: What is called the "return period" represents the new figure in time for what used to be considered a "hundred year" flood at the time the dams were built, nearly half a century ago.

This figure refers to that feature:



The caption:

Projected return periods (year) under (a) RCP4.5 and (b) RCP8.5 corresponding to a 100‐year flood event in the historical period for 13 major dams over California (TR = Trinity; LE = Lewiston; SH = Shasta; BL = Black Butte; OR = Oroville; FO = Folsom; HO = New Hogan; ME = New Melones; DO = New Don Pedro; EX = New Exchequer; BU = Buchanan; HI = Hidden; FR = Friant). The black horizontal dashed line represents the 100‐year flood level. The dark red dots represent the projected multimodel median return periods corresponding to a 100‐year flood event in the historical record. The heights of the black vertical bars represent the interquartile range (between the 75th and 25th percentiles) as an indicator of uncertainties associated with the use of different climate models.


Note that many of the "hundred year" floods will now return in considerably less than 100 years.

Oh well...

Failure probabilities:



The caption:

The projected hydrological failure probability corresponding to the historically 100‐year flood over different design lifetimes (i.e., 10, 20, 30, …, 100) for each of the dams under (a) RCP4.5 and (b) RCP8.5. The dashed black curve represents the baseline historical failure probability. Curves are color coded to represent different dams (TR = Trinity; LE = Lewiston; SH = Shasta; BL = Black Butte; OR = Oroville; FO = Folsom; HO = New Hogan; ME = New Melones; DO = New Don Pedro; EX = New Exchequer; BU = Buchanan; HI = Hidden; FR = Friant). Locations of these dams are demonstrated in Figure S1.


An excerpt from the conclusion:

We investigate possible impacts of climate change on future flooding hazard for several major dams over central and northern California. We use routed daily inflow data into 13 major dams from 10 GCMs under RCP4.5 and RCP8.5. We compute historical and projected return periods to quantify changes in the hydrological failure probability of dams in a warming climate. Our results point to amplification of flood hazard in the future that can be attributed to increases in the frequency of extreme flows in a warming climate. Indeed, our results reveal that the historical 100‐year flood event is 5 times more likely in the future under the “business as usual” RCP (RCP8.5). We argue that in a warming climate, the risk of hydrological failure of major dams in California is likely to increase. Moreover, uncertainty associated with shorter return period events imposed by climate models is high, which postures a major uncertainty for short‐term operations and long‐term planning of major dams in California.


"RCP" refers to "representative concentration" pathways, features in the lexicon of climate modeling for various carbon dioxide accumulation scenarios. We are living "business as usual" and there has been no serious effort to step away from "business as usual." Sneaking under the cover of popular enthusiasm for solar and wind energy, the use of dangerous fossil fuels is actually increasing, dramatically.

Speaking of wind and solar, we had a "happy talk" post here that I personally found very amusing, which was a prediction that wind turbines and solar cells will work just as well as climate degradation increases, which I took to be a statement that they will continue to work when they don't work.

I would call "working" being doing something meaningful to address climate change. I may be nearly alone in that; but it's what I think.

The wind and solar industries have taken on an inertia of their own - meaning that they are no longer attached to the goal described as the motivation for their creation. These industries now divorced from the issue of climate change, which is just as well, since they haven't worked, aren't working and won't work to address the tragedy of climate change.

I hope you'll have a nice evening.

I haven't vomited since 1973...until this morning.

The last time I threw up I was in Ensenada, Mexico, shooting back 25 cent Tequila Sunrises. I certainly deserved it then; I was a very stupid kid.

I haven't had a tequila sunrise in probably 30 years.

I didn't do anything other than eat dinner.

I had nasty diarrhea all night.

This morning I threw up.

It's appropriate, I think, that it happened again during the Trump administration.

The irony is that over in the E&E section last night I completed a post involving (partially) the chemistry of bismuth.

A Battery Which Desalinates Water In Charging and Discharging.

This morning, it appears, according to my wife who knows all about vomiting - she's married to me after all - I should drink a bismuth suspension; Pepto-Bismol.

She's very sympathetic, and nicely brought medicine and water.

I'm actually feeling better since throwing up.

A Battery Which Desalinates Water In Charging and Discharging.

The paper I'll discuss in this post is this one: A Desalination Battery Combining Cu3(Fe(CN)6)2 as a Na-Storage Electrode and Bi as a Cl-Storage Electrode Enabling Membrane-Free Desalination (Do-Hwan Nam , Margaret A. Lumley, and Kyoung-Shin Choi,* Chem. Mater., 2019, 31 (4), pp 1460–1468)

The graphic in the abstract also appears in the paper's text:



In the text the caption reads as follows:

Figure 7. Scheme showing the operation of the CuHCF/Bi desalination battery; the desalination process is equivalent to discharging and the salination process is equivalent to charging.


According to a lecture I attended last weekend, sea level rise has been measured as rising at the fastest rate ever observed in recorded history, said history extending back to the 18th century in the form of tidal gauges.

Science on Saturday: Managing Coastal Risk in an Age of Sea-level Rise



I have often wondered about the effect of the release of fossil water, such as the water being mined from the stressed Ogallala Aquifer in the Central United States to irrigate corn and wheat crops, on sea level rise.

According to the speaker, Dr. Robert Kopp , the proportion of sea level rise owing to the mining of fossil water represents about 10%.

It follows, in a speculative if not practical sense, that recharging these fossil reservoirs with fresh water produced by desalination might serve to help drain rising seas, at least in the "percent terms" that the people who have cheered the failed policy of betting the planetary atmosphere on solar and wind energy so love.

Of course the requirement for doing this, for desalinating seawater and putting in in fossil aquifers involves huge amounts of energy since desalination is an energy intensive process, both in the sense of desalination itself and in the sense of shipping the water to the aquifers themselves.

A battery is a device that wastes energy, as I often remind those silly - but effectively dangerous inasmuch as humanity has lost the bet they made - people who bet the planetary atmosphere on solar and wind energy. They think a metal based band aid will fix the useless and trivial solar and wind industries biggest problem, at least in their minds, its intermittent nature. This is a bit of a distraction. The biggest problem of the trivial solar and wind industry is that it has not worked, is not working and will not work to address climate change. All of the solar and wind energy provided each year as of 2019, after decades of wild cheering produces a fraction over 10 exajoules - 10.63 exajoules to be exact - of the nearly 585 exajoules - 584.95 exajoules to be exact - humanity was consuming as of the last full report, referring to 2017. In this century energy demand rose by 163.84 exajoules.

2018 Edition of the World Energy Outlook Table 1.1 Page 38 (I have converted MTOE in the original table to the SI unit exajoules in this text.)

I'm sorry to kick over the milk from this much worshiped sacred cow, but our ethical responsibility to all future generations must be the statement that "reality matters."

The fact that a battery wastes energy is a consequence of the 2nd law of thermodynamics, which is a law of physics. Physics doesn't care about people's energy fantasies; the laws of physics are not subject to repeal by any legislature or change because of any "New Deal" or any linguistic exercise attempting to define what is and is not "green."

Nevertheless, the battery described in this paper is interesting because it does something that I believe, despite Jevon's Paradox, which it increases the efficiency of energy use, inasmuch as it captures energy that would otherwise be wasted, not all of it course - the 2nd law prevents that - but more of it.

From the introductory text of the paper:

Lack of access to fresh water is one of the most serious issues currently facing our society,1−4 and seawater desalination is considered the most feasible approach to produce an adequate supply of fresh water.5−8 Currently, thermal distillation and reverse osmosis (RO) are the two most established seawater desalination methods.6−10 While RO is less energy intensive than thermal distillation, it still requires significant electrical energy input for the operation of high-pressure pumps. In addition, processes related to the prevention of membrane fouling (i.e., pre-treatments and post-treatments of water) keep the cost of seawater RO high.8−12

Recently, various electrochemical desalination methods have been reported.13−34 The operating principles of these electrochemical desalination methods are fundamentally different from those of RO and thus provide diverse opportunities to advance desalination technologies. Among these systems, desalination batteries are particularly attractive because they couple desalination with energy storage.29−34 Like other conventional batteries (e.g., Li-ion batteries), desalination batteries store and release energy during the charging and discharging processes. However, through combination of a Na storage electrode and a Cl-storage electrode, the energy storage and release are coupled with the removal and release of Na+ and Cl−. Because the energy consumed during the charging process is at least partially recovered during the discharging process, desalination batteries can potentially achieve costefficient desalination with a much lower energy requirement than conventional desalination systems. Furthermore, as Na+ and Cl− are stored in the bulk of the Na-storage and Cl-storage electrodes, not just in the electrical double layer of the electrodes as in the case of capacitive deionization, a high capacity for salt removal can be achieved.29−33 As a result, desalination batteries may be used for seawater desalination as well as brackish water desalination. Another distinct advantage of desalination batteries is the possibility to achieve membranefree desalination.


Previous efforts, according to the paper, to make a chloride storing electrode involved the use of insoluble silver chloride, but was considered impractical owing to the cost of silver and the poor electrical conductivity of AgCl. In a previous paper, the authors described a new kind of storage electrode based on bismuth, mostly known to consumers as a constituent the pink anti-diarrheal OTC medication PeptoBismol, and to nuclear engineers as a constituent of the LBE eutectic metal used in certain types of fast nuclear reactors.

In an earlier paper, the authors' group described the discovery of this electrode:

Bismuth as a New Chloride-Storage Electrode Enabling the Construction of a Practical High Capacity Desalination Battery (Do-Hwan Nam and Kyoung-Shin Choi, J. Am. Chem. Soc., 2017, 139 (32), pp 11055–11063)

This new type of electrode during charging undergoes the following electrochemically driven reaction:



In this case the chloride ion is oxidized to the hypochlorite ion which is the common constituent of bleach, water purification chemicals and the "chlorine" in swimming pools. However it is stored in the electrode as the insoluble bismuth salt.

The update that this paper describes involves the other electrode, which is a copper ferricyanide based electrode.

If the presence of cyanide worries you in a water desalination electrode, don't worry, be happy. Ferricyanide is very insoluble, and a form of it, known as "Prussian Blue" is actually used as an antidote to heavy metal poisoning given its strong ability to complex monovalent species, notably as an antidote should you happen to eat the rat poison thallium or Cs-137, the radioactive fission product. (People have a kind of fetish about the possibility of being exposed to Cs-137, even though the isotope has been ubiquitous since the era of open air nuclear testing; they are less concerned with air pollutants, even though air pollutants kill seven million people every year and cesium-137, um, doesn't. Go figure.) People deliberately eat ferricyanides.

Another advance the authors have made involves the physical form of the bismuth electrode; it is described herein as a "foam."

Similarly the copper ferricyanide electrode is also a foam, as shown in the following graphic from the paper:



The caption:

Figure 1. (a) XRD pattern and (b, c) SEM images of as-synthesized Cu3[Fe(CN)6]2·nH2O (CuHCF) powder.


The cupric ferricyanide compound is referred to as "CuHCF" throughout the rest of the paper. (I'm not sure why.)

The overall structure of this system is also shown:



The caption:

Figure 2. Unit cell of a Prussian blue analogue with an ABX3 perovskite-type structure, where B sites are occupied by alternating Cu(II) and Fe(III) ions and X sites are occupied by CN groups. The degree of occupancy of the A site varies depending on the Cu(II)/ Fe(III) ratio and the Fe(II)/Fe(III) ratio.


This structure is, more or less, best described as the perovskite structure. Lead based perovskites, in particular those containing cesium, have generated lots and lots and lots of papers connected with the scheme of making solar energy work, which, if you actually take efforts to address climate change seriously, as opposed to having an entirely dogmatic fondness for solar energy, has not worked in any meaningful sense, is not working in any meaningful sense and will not work in any meaningful sense. Believing that solar electricity is a path to addressing climate change is no different, at least in my book, then outright climate change denial. The scheme to make cesium lead based perovskite solar cells is even worse than the distribution of cadmium based solar cells, because lead is a very toxic metal and distributing it widely is a very bad idea. (Prussian Blue will not effectively treat lead poisoning.)

I wish people would think and if they can't do that, at least observe.

Anyway...

The redox element in the copper ferricyanide electrode is the iron, which is reduced from the ferric, (Fe(III)) ion to the ferrous (Fe(II)) ion and back again in the charge/discharge cycle:



Here is a graphic demonstrating the performance of the system as a battery:



The caption:

Figure 3. (a) Potential−capacity plots and (b) cycle performance of the CuHCF electrode tested at a current density of 60 mA g−1 in an acidic 0.6 M NaCl solution (pH 1.2). (c) Potential−capacity plots and (d) cycle performance of the CuHCF electrode tested at a current density of 60 mA g−1 in a neutral 0.6 M NaCl solution (pH 6.2).


From this diagram it's clear that the performance of the system in terms of cycling is a little less effective in neutral solution than in acid. This could be a real problem for the water quality the system puts out, but let's continue anyway.

This problem is demonstrated by looking at the color aspect of the desalinated water.



The caption:

Figure 4. (a) Photographs showing the colors of the solutions after the cycling tests and chemical stability tests. The yellow color is due to the dissolution of Fe(CN)6 3−. XRD patterns of the CuHCF electrode after 40 cycles of sodiation/desodiation in (b) an acidic 0.6 M NaCl solution and (c) a neutral 0.6 M NaCl solution. The XRD patterns of Cu3[Fe(CN)6]2·nH2O and Cu2Cl(OH)3 are shown for reference.


The problem seems to lie with the nature of the CuHCF electrode.

The authors investigate in some detail how it behaves over a range of pH values:

To elucidate the cause of the instability of CuHCF, we first examined the solubility of CuHCF in a neutral 0.6 M NaCl solution but found no change in composition even after 1 week of immersion. However, when we increased the pH of the solution to 11, we visually observed the dissolution of Fe(CN)6 3− from CuHCF (Figure 4a and Figure S1) and saw the formation of Cu2Cl(OH)3 by XRD. Indeed, CuHCF is known to decompose to Na3Fe(CN)6 and CuO in the presence of NaOH through the following reaction:



In the presence of Cl−, however, Cu2Cl(OH)3, rather than CuO, will form as one of the decomposition products (eq 4). We confirmed the thermodynamic feasibility of the formation of Cu2Cl(OH)3 in 0.6 M NaCl solution by constructing a Pourbaix diagram for Cu in an aqueous solution containing 0.6 M Cl− (Figure S2). Based on these results, the degradation of CuHCF accompanied by the dissolution of Fe(CN)6 3− that occurred during the cycling test in neutral saline water can be expressed as follows:




After elucidating that the instability of CuHCF was related to the reaction between CuHCF and OH−, we realized that the instability of CuHCF during the cycling test in neutral solution was caused by OH− generated from the Pt CE used in the three-electrode cell. The major reaction that can occur at the Pt CE in an aqueous solution during desodiation of the CuHCF electrode is water reduction (eq 5), which generates OH−.



Because the CuHCF and Pt electrodes were kept very close (<0.5 cm) to minimize the IR drop from the solution, the local pH experienced by the CuHCF electrode could have increased significantly during water reduction at the Pt CE, resulting in the formation of Cu2Cl(OH)3 and dissolution of Fe(CN)6 3−. This also means that the capacity fading of the CuHCF electrode observed during the half-cell test in a neutral solution is not an intrinsic limitation of operating CuHCF in a neutral solution. Rather, it is a problem that arises from the alkaline pH generated from water reduction by the Pt CE that will not be used in a real device.


That's good news, I guess, but perhaps at the end of this questionable post - questionable since it goes against the popular perception and we all know that what is popular is always right, right? - it might be useful to question what a "real device" is or might be.

The preparation of the Bi electrode is not described in detail in the paper, but the reference containing the detailed description is given; it is the same one referenced above by the authors in the same group.

This schematic gives the general idea, however, and the result is shown in SEM:




The caption:

Figure 5. (a) Schematic illustration of the deposition of a Bi foam electrode using in situ generated H2 bubbles as a template and SEM images of a Bi foam electrode showing the (b) foam structure and (c) nanocrystalline Bi forming the foam wall.


And now the fun part, reflecting the thermodynamics to which I refer whenever the "magic" of batteries is evoked to show how so called "renewable energy" "could" work, except it hasn't worked, isn't working and won't work. We've gone up 23 ppm in carbon dioxide measurements in the last 10 years at the Mauna Loa atmospheric carbon dioxide observatory, this while sinking trillions of dollars into solar and wind.

The thermodynamics, graphically displayed:



The caption:

Figure 6. Potential–capacity plots for the CuHCF and Bi electrodes measured vs Ag/AgCl at a rate of ±1 mA cm–2 during (a) the desalination process in a neutral 0.6 M NaCl solution (pH 6.2), (b) the salination process in a neutral 0.6 M NaCl solution (pH 6.2), and (c) the salination process in 65 mM HCl (pH 1.2). Corresponding cell voltage–capacity plots (d) during discharging (desalination) in 0.6 M NaCl (pH 6.2) and charging (salination) in 0.6 M NaCl (pH 6.2) and (e) during discharging (desalination) in 0.6 M NaCl (pH 6.2) and charging (salination) in 65 mM HCl (pH 1.


Again, a battery is a device that wastes energy, as the preceding diagram for this battery clearly shows.

The Coulombic efficiency, or Faradaic efficiency, is shown in the final graphic to be included in this post:



The caption:

Figure 8. Cycling test of the CuHCF/Bi cell for desalination/salination. The discharging process (desalination) was performed in0.6 M NaCl (pH 6.2), and the charging process (salination) was performed in 65 mM HCl (pH 1.2).


Faradaic efficiency is a different matter than thermodynamic efficiency; the faradaic efficiency may be thought of as a loss to chemical side reactions that degrade the battery over time. By contract thermodynamic efficiency involves a number of other factors such as the internal resistance of a battery, which itself is a function of the concentration - or more precisely the activity - of ions which conduct the current within the battery. In this case, the ions are salts, and a reduction of the concentration of salts, which the battery is designed to accomplish, raises the internal resistance, and therefore the thermodyanmic efficiency is reduced. This is why the battery works better in an acid solution than in a neutral solution. The practical import of this would mean that the system would probably not be very viable to generate tap water, although it might prove acceptable for use to make agricultural water, particularly in the case where the acid is neutralized with ammonia, and then subject to ion exchange whereby the chloride is replaced by nitrate, or, if it works, where nitric acid is used in lieu of hydrochloric - although I'm not personally familiar with the chemical stability of bismuth metal in nitric acid as opposed to hydrochloric acid.

Despite the high “columbic efficiency” the authors make the point that the batteries do have a long term cycling problem, a materials science problem involving repeated expansion and contraction. (This is a feature of many situations involving batteries: They are thought of as electrochemical devices, but they most assuredly have a mechanical feature, which is sometimes utilized to measure their remaining capacity during discharge.) In describing the problem, they discuss an approach to addressing it:

We note that the slight capacity fading observed during the cycling test is not due to the decomposition of CuHCF, which was easy to confirm as the solution did not change color, unlike what was observed during the half-cell test. We believe that this was caused by the pulverization of the Bi electrode due to the volume change involved during the conversion between Bi and BiOCl (158%). There are several effective strategies that can be used to improve the cycle performance of Bi, which include the addition of a carbon or polymer coating on Bi or making composites of Bi with Cl-inactive materials to buffer the volume change of Bi during chlorination/dechlorination. These strategies have been proven to work for the stabilization of other electrodes that suffer from this pulverization problem.45,46


Now we need to turn to the issue of what this paper implies. Very often, particularly in blogging kinds of situations, people look at some small laboratory scale results to assume that they are ready for prime time, to immediate scale up to industrial scale. This is almost never the case; indeed, it's extremely rare for a laboratory result to be transferred to an industrial scale. I've known many tens of thousands of scientists in my career, and can count on the fingers of one hand those I met who experienced such a thing; I am one such person, not because I'm good, but because I'm lucky to have participated in a discovery and had the opportunity to work in a place where the need for it appeared.

As impressed as I am with this very interesting paper; I'm not sure at the end of the day it will mean very much at all.

Batteries generate lots of enthusiasm among those people who have bet trillions of dollars, and worse, the planetary atmosphere, on the idea that solar and wind energy will save the day, even though solar and wind energy won't do any such thing. These people claim, in defiance of data, that a "problem" with so called "renewable energy" is that it's intermittent, and thus if we had batteries or hydrogen, or some other such thing, everything would be wonderful and dangerous fossil fuels would magically disappear. This is nonsense. After more than half a century of world wide cheering - beginning with the invention of the solar cell in 1954 (there are Bell Labs Magazine ads from the early 50's available on the internet showing this history) - all the world's tidal, geothermal, solar and wind energy combined produced as of 2017, 10.83 exajoules of energy, increasing at by 1.21 exajoules in a year that world energy demand increased by 8.88 exajoules. By contrast the use of dangerous natural gas grew in 2017 by 4.19 exajoules, and petroleum by 1.97 exajoules. (Coal fell by 0.21 exajoules, trivial in a century where overall, it grew by more than 60 exajoules (60.25 to be exact) - so the often stated nonsense that it is falling because of so call "renewable energy" is a Trumpian scale lie.) So called “renewable energy” other than biomass and hydroelectricity – and we’re running out of rivers to completely destroy – produces less than 2% of the world energy supply, and now we want to start wasting the trivial quantities there are. Even adding the two forms of energy also described as "renewable energy," biomass and hydroelectricity, so called renewable energy produces less than 15% of the world's energy supply. The reason that so called “renewable energy” isn’t working, hasn’t worked and won’t work is physics, specifically the extremely low energy to mass ratio.

Even if the solar and wind industries were as magic as these gamblers hoped they would be - whether or not we engage in the "gambler's fallacy" and throw even more good money after bad money for this unworkable scheme, it’s clear that humanity as a whole has already lost the bet - it is unlikely that these desalination batteries would really produce significant amounts of water, since for one thing, it's not likely that charging and discharging even on a grid scale, would produce all that much water. Secondly it's not clear that there is enough bismuth available for isolation to produce hundreds of millions of these devices, which is what obviously is required.

Bismuth supplies are not generally considered to threatened, but they are of long term concern; said concern being tied to current demand. If the demand rises however, a different calculation may be obtained. One possible way to increase demand would be of course to make millions upon millions of desalination batteries. (This won't happen; it's a thought experiment.)

A brief point: I am often - appropriately, I think - called out on my hypocrisy; for one example I drive a car even as I call for an end to the car CULTure.

In the case of bismuth supplies, someone might note that I favor high temperature nuclear breeder reactors minus the traditional liquid sodium coolant, and that I've expressed admiration for LBE cooled reactors wherein "LBE" refers to "lead bismuth eutectic" alloys. However, if we drop the bismuth and stick with pure lead, I also note than in a neutron flux lead would be transmuted into less toxic bismuth, creating such a eutectic in a reactor that starts out cooled by pure molten lead. (No matter: No one cares what I think about nuclear reactors anyway.) It is possible to synthetically make bismuth from lead, although in truth, the high energy density of nuclear power means that the amounts of bismuth that could be so synthesized is very small; this high energy density also makes nuclear power environmentally superior to all other forms of energy even as it presents some engineering problems. In any case, the same energy density means that the requirement for bismuth is very much smaller in the nuclear case than it would be in the battery case.

The issue is not really about bismuth as it is about critical thinking.

Not long ago in this space, there was a post entitled - excuse me if I paraphrase - "Scientists discover a way to make carbon dioxide back into coal."

It was linked to a university press release about the wonderful generic scientists who accomplished this wonderful feat. I personally was a little surprised that this was a big announcement. We have known for over a century how to accomplish this feat: It's called the "Boudouard reaction" and its discoverer, Octave Boudouard died in 1923, twenty-three years after discovering the reaction that bears his name.

The breathless post contained some commentary, including some sarcastic remarks from me (which happily resulted in no response), in which the original poster said that this miracle "could" maybe, possibly, after a fashion, be performed using solar energy (which he or she declared to be "the best option" or maybe we could wait around for those magic nuclear fusion reactors to appear at a commercial scale.

Now here's the terrible thing: Curious at why this recapitulation of something the Boudouard reaction has been known to do for over a century, I opened the link to the news release.

Here's the news release in question, from scientists in that coal burning hellhole in Australia: Climate rewind: Scientists turn carbon dioxide back into coal.

I never read any of these news releases picked up by the popular press and reported elsewhere without investing some critical thinking. If the issue strikes me as odd - and this one does since I think about the Boudouard reaction all the time - I'll look for the original source and look into it to understand what, precisely, the big deal is.

The news release refers to a paper published in Nature Communications. I am very fortunate, because I pretty much, with some minor exceptions, have access to all the world's primary scientific literature. I fully realize that many people are not so privileged, but in this case, such access is not necessary, because the paper is open sourced; anyone with access to the internet can read it.

Here it is: Room temperature CO2 reduction to solid carbon species on liquid metals featuring atomically thin ceria interfaces (Dorna Esrafilzadeh et al, Nature Communications Volume 10, Article number: 865 (2019))

Here's a brief description from the paper of the experiment:

Synthesis of different weight fractions of metallic cerium (0.5, 1.0 and 3.0 wt%) into liquid galinstan was performed using a mechanical alloying approach (see Methods). Cerium containing LM was created, since cerium oxides are known to reduce CO2 to CO via the Ce3+–Ce4+ cycle4,5. Cerium’s solubility in liquid gallium and its alloys is expected to be between 0.1 and 0.5 wt%, while Ce2O3 is expected to dominate the LM surface, as a 2D layer, under ambient atmospheric conditions due to the high reactivity of cerium when compared to the constituents of galinstan, and the known oxidation mechanism of metallic cerium that leads to the initial formation Ce2O3 at the metal–air interface15,21,22.


The bold is mine.

Here, also from the paper, are the constituents of "galistan":

Common low-melting point gallium alloys, such as the eutectic mixture of Ga, In and Sn, referred to herein as galinstan...


Here is the periodic table of "endangered elements," elements whose supply generate concern among chemical and economic professionals:



Of the three elements in "Gallistan" two, indium and gallium are identified as facing "serious threats," the third, tin, faces long term supply issues.

(I have discussed the availability of cerium elsewhere in this space: Cerium Requirements to Split One Billion Tons of Carbon Dioxide, the Nuclear v Solar Thermal cases. )

As of last year, anthropomorphic activities are estimated to have resulted in the release of 41.5 +/- 0.3 billion tons of carbon dioxide: Global Carbon Budget 2018

The same publication (see the internal spreadsheets) estimates that since 1750, human activities (including deforestation) have resulted in 430 billion tons of carbon (+/- 20 billion tons), which equates roughly to 1.5 trillion tons of carbon dioxide.

We are never going to have enough gallium based alloys to significantly reduce carbon dioxide.

As for "solar being the best way," in 2017, coal burning was responsible for 157 exajoules of energy, solar and wind combined less than 11. If one can't think critically about what these numbers imply, one can't think critically at all.

The time for credulous wishful thinking is done.

Critical thinking is best done when one looks at sources; but one can also do it on the fly - to a first approximation - simply by inspection.

As for desalination, for many reasons, including but not limited to sea levels, we need to do it. Like removal of carbon dioxide from the atmosphere, it is an energy intensive process and a huge engineering challenge. My own expectation is that the best route to it is one that has never been industrialized, the use of the fact that salts are insoluble in supercritical water. I note that an added benefit of this approach will be the supercritical oxidation of biomass in seawater, as well as the serious pollutants represented by microplastics in seawater. In the right array, one can imagine many types of systems whereby the energy can be recovered, water can be recovered, carbon dioxide can be captured and valuable elements in seawater, notably uranium, can be captured.

That's all for a later long winded rant into the void.

I wish you a pleasant Saturday evening and a wonderful Sunday.

Ionic Liquid Polymeric Membranes for the Separation of Carbon Dioxide From Nitrogen Streams.

The paper I'll discuss in this post is: Imidazolium-Based Copoly(Ionic Liquid) Membranes for CO2/N2 Separation ( Isabel M. Marrucho et al Ind. Eng. Chem. Res., 2019, 58 (5), pp 2017–2026)

I believe that it is extremely urgent to phase out fossil fuels, not in some far off "by 2050" or "by 2100" putative so called "renewable energy" nirvana that will never come, but now. It is not ethical or just to expect our children, grandchildren and great grandchildren will be able to do what we ourselves cannot do or are too cheap to do, this after we have seriously destroyed most of the world's resources by surrendering them to entropy.

The technology to do this exists, but we must surrender our stupidity in order to use it. It's called "nuclear energy."

Early this week, several daily readings at the Mauna Loa carbon dioxide observatory recorded (momentarily) readings greater than 414 ppm. The weekly average, was 412.40 ppm, just shy (by 10 parts per billion) of the weekly average record set two weeks ago, 412.01 ppm. The unfortunate thing about this reading is that the consequences of the reading today will have effects years later, since the ocean is warming rapidly and because it also displays thermal inertia, it can only cool slowly.

Therefore it is urgent not only to stop dumping carbon dioxide and other dangerous fossil fuel wastes into the atmosphere will they kill directly as poisons as well as slowly as climate agents, but to begin, as quickly as possible to remove them from the air.

One avenue for capturing carbon dioxide is via the combustion of biomass, and capture of the exhaust.

This is best done by closed combustion in oxygen enriched atmospheres, a subject I discussed recently: On the combustion of biomass in oxygen enriched carbon dioxide atmospheres. (Well, it was interesting to write, in any case, even if it may have been unreadable.)

However, the production of oxyfuels requires a pure oxygen source, and energetically sustainable oxygen sources currently do not exist, since air separation is driven by electricity and in this country more and more electricity is being obtained by the combustion of dangerous fossil fuels than at any time in history. Oxygen cannot be made in a sustainable fashion unless it is made from the thermochemical splitting of water or carbon dioxide, and our ignorance has prevented us from moving forward with that, although the technology has been demonstrated at least on pilot scales.

The next best option is to capture carbon dioxide from the combustion of biomass in such a way as the serious pollutants, including but not limited to carbon dioxide are captured and put to use by reduction.

Hence my interest in the cited paper above, since a combustion stream is largely a mixture of carbon dioxide and nitrogen.

The paper concerns a class of materials that has been an intense area of research, "ionic liquids" which are salts of organic cations with organic anions (and sometimes inorganic ions) that can be liquid at room temperature but exhibit essentially no vapor pressure, and thus do not release fumes or easily catch fire.

In this case, materials featuring structures common to many ionic liquids are incorporated into polymers, this for the purpose of separating carbon dioxide.

From the introductory text of the paper:

The development of new materials for carbon dioxide (CO2) capture is becoming of vital importance as concerns about the growing concentration of anthropogenic CO2, associated with global warming and unpredictable climate changes, are being widely expressed. In particular, considerable attention has been paid to ionic liquids (ILs), due to the unique tunability of their properties1,2 and superior CO2 affinity in comparison with light gases, such as N2 and CH4.3,4 Several approaches have been proposed: from mixtures of ILs with other solvents, such as amines5 and glycols,6 to functionalization of ILs with diverse chemical groups,7−12 to other more sophisticated methodologies, as for instance ILs impregnation on different porous supports, such as polymeric membranes,13,14 zeolites,15 silica gel,16 and metal−organic frameworks.17

In what concerns the use of ILs in membranes, two strategies deserve special attention: the use of an inert porous membrane to support ILs and the incorporation of ILs in a polymeric matrix. Supported ionic liquid membranes (SILMs) have been widely studied for CO2 separation as they offer a facile preparation methodology.18 Results using a large number of ILs show that SILMs is a very promising strategy, since high CO2 permeabilities and attractive permselectivities can be obtained. However, SILMs present a major drawback: their low stability under high trans-membrane pressures and high temperatures, due to the weak capillary forces that hold ILs within the pores. On the other hand, the incorporation of ILs in polymeric membranes, in which the IL is entrapped in the tight spaces between the polymer chains, has proven to be a successful approach, providing membranes with increased mechanical strength compared to SILMs. A large variety of polymers has been used to prepare polymer−IL composites, 19−21 but the most successful approach lays on the use of poly(ionic liquid)s (PILs),22,23 since they allow the incorporation of higher amounts of ILs, due to the large degree of strong ionic interactions between the IL and the PIL components. On top of that, neat PIL membranes possess higher CO2 sorption capacities than their corresponding IL monomers24 and present CO2/CH4 and CO2/N2 similar or greater than those observed for SILMs.


What is under discussion are "PILS."

Here are some PILS referenced in the paper:




The caption:

Figure 1. Different PIL copolymers structures which have been used to develop CO2 separation membranes.(42−44)


The authors here make a new series of PILS

Here is some of the interesting organic chemistry by which the "PILS" in question are made:



The caption:

Scheme 1. Synthesis of CTA


"CTA" here refers to "Chain Transfer Agent," an agent designed to control the size of polymers by trapping the reactive mechanistic intermediate during the polymerization reaction. Here the potassium salt of of ethyl xanathate is reacted with ethyl 2-bromopropionate to give 2-ethoxythiocarbonylsulfanyl-propionic acid ethyl ester.

The use of chain transfer agents in polymerization reactions is called "reversible addition−fragmentation chain transfer" (RAFT) polymerization.

Here is the synthesis of the "ionic liquid" portion of the polymer:



The caption:

Scheme 2. Synthesis of Vinylimidazolium Monomers


The RAFT polymerization:



The caption:

Scheme 3. RAFT Polymerization of Vinylimidazolium Monomers


Assembly of the final co-polymers:



The caption:

Scheme 4. Synthesis of the Copoly(Ionic Liquid)s [ViRIm](Sty)X


Note that several different polymers are described in this graphic, not just a single polymer.

The differing polymers were then cast into membranes by dissolving them in a mixture of acetone and a commercially available ionic liquid called [C2mim][NTf2], and then spread into petri dishes, where, upon drying they gave membranes.

Not all of the polymers could form membranes however. Some were brittle and broke; others simply would not spread properly:



The caption:

Figure 2. Pictures of the PIL–IL membranes: (A) poly(ViPenIm)(Sty)NTf2 with 10 wt % IL, (B) poly(ViBenIm)(Sty)NTf2 with 25 wt % IL, (C) poly(ViPenIm)(Sty)NTf2 with 30 wt % IL, (D) poly(ViBenIm) NTf2 with 20 wt % IL, (E) poly(ViNapIm) NTf2 with 20 wt % IL.


The authors write:

Our attempts to prepare free-standing membranes with the two synthesized pure homo PILs, namely poly(ViBenIm)NTf2 and poly- (ViNapIm)NTf2, were unsuccessful, since they became very brittle and broke even before being peeled out of the Petri dishes. Although the prepared poly(vinylimidazolium)-polystyrene copolymers showed better film forming ability than the homo PILs, the obtained co-PIL membranes were not flexible enough to be peeled out of the Petri dishes and handled without breaking. Therefore, the incorporation of different amounts of free [C2mim][NTf2] IL was tested as a strategy to enhance the film forming ability of the homo and poly(vinylimidazolium)- polystyrene copolymers. Also, it is well documented in the literature that a large amount of IL incorporated into the PIL leads to higher CO2 permeability and diffusivity through the PIL−IL membrane.


Some of the physical chemistry of measuring the properties of gas diffusion:

Gas transport through the prepared PIL−IL dense membranes was assumed to follow a solution-diffusion mass transfer mechanism,48 where the permeability (P) is related to diffusivity (D) and solubility (S) as follows:

P = D × S (1)

The permeate flux of each gas (Ji) was determined experimentally using eq 2,49 where Vp is the permeate volume, Δpd is the variation of downstream pressure, A is the effective membrane surface area, t is the experimental time, R is the gas constant, and T is the temperature.

(2)


Ideal gas permeability (Pi) was then determined from the steady-state gas flux (Ji), the membrane thickness (l), and the trans-membrane pressure difference (Δpi), as shown in eq 3.50

(3)


Gas diffusivity (Di) was determined according eq 4. The time lag parameter (θ ) was calculated by extrapolating the slope of the linear portion of the pd vs t curve back to the time axis, where the intercept is equal to θ.50

(4)


After Pi and Di were known, the gas solubility (Si) was calculated using the relationship shown in eq 1. The ideal permeability selectivity (or permselectivity), αi/j, was obtained by dividing the permeability of the more permeable specie i to the permeability of the less permeable species j. As shown in eq 5, the permselectivity can also be expressed as the product of the diffusivity selectivity and the solubility selectivity:

(5)



The unit for gas permeability is the "Barrer" which is incorporates units of mass transfer, area and pressure.

Here are some results represented graphically:




The caption:

Figure 3. Gas permeabilities (A), diffusivities (B), and solubilities (C) through the prepared imidazolium-based co-PIL–IL membranes. Error bars represent standard deviations based on three experimental replicas


The results of their membranes is compared with some literature values for other PILS



The caption:

Figure 4. CO2/N2 separation performance of the co-PIL–IL composite membranes obtained in this work. Data is plotted on a log–log scale, and the upper bound is adapted from the work of Robeson.(53) Literature values of other PIL–IL composite membranes previously reported are also illustrated for comparison.(23,30,32,38,40,47,54)


Some comments from the conclusion of the paper on the overall results:

RAFT derived imidazolium-based homo- and copoly(ionic liquid)s were successfully synthesized and anion metathesis reactions were performed. The prepared polymers were characterized by nuclear magnetic resonance (NMR), differential scanning calorimetry (DSC), and thermogravimetric analysis (TGA). The results showed that the synthesized poly(vinylimidazolium)-polystyrene copolymers have high thermal stabilities (up to 300 °C) and are thus suitable for postcombustion CO2 separation. The membrane forming ability of the prepared imidazolium-based homo- and copoly- (ionic liquid)s was evaluated using the solvent casting technique. It was found that the synthesized homo- and poly(vinylimidazolium)-polystyrene copolymers were unable to be processed into mechanically stable flat form membranes due to their brittle nature. Consequently, the homo- and poly(vinylimidazolium)-polystyrene copolymers were blended with different amounts (10, 20, 25, 30, 40, and 60 wt %) of free [C2mim][NTf2] IL. Only the random copolymers poly- (ViPIm)(Sty)NTf2, poly(ViBenIm)(Sty)NTf2, and poly- (ViNapIm)(Sty)NTf2, combined with 10, 25, and 30 wt % of [C2mim][NTf2], respectively, resulted in stable and homogeneous free-standing solid membranes. The membranes exhibited CO2 permeabilities ranging from 16.5 to 24.5 and CO2/N2 permselectivities from 31.7 to 34.4, thus falling in a region of the Robeson plot below the 2008 upper bound, where other PILs bearing similar amounts of IL also are. Curiously, and due to the small amount of IL incorporated in the co-PIL−IL composites, the effect of the polymer backbone structure in the gas diffusion and solubility can be observed.


Often, while daydreaming, I think of all sorts of Rube Goldberg approaches to carbon capture (involving biomass combustion or heat driven reformation with either water or captured carbon dioxide). One approach that might be available in the short term, given the immediate emergency before thermochemically produced oxygen is available, is the use of compressed air in Brayton type cycles, assuming one can overcome the corrosive properties of sulfur, nitrogen and volatilized alkali metals. (I can imagine these things, but they're Rube Goldberg approaches to be sure.) In the substitution of compressed air for pure oxygen or oxygen/carbon dioxide atmospheres for combustion, the separation of nitrogen from carbon dioxide might prove useful, and one can imagine it indeed being driven by pressure gradients also utilized to turn turbines.

Just some random thoughts, some speculations...

But we're as a race of beings running out of time, even faster than I am running out of time, and I am out of time.

I hope you had a wonderful weekend. I did.

Star Dancer



1987 Harry Fonseca (1946-2006): Maidu-American

At the Eiteljorg Museum, Indianapolis, Indiana.

https://eiteljorg.org/exhibitions/fonseca/



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