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NNadir

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Highly sensitive, uranium based UV detectors.

I am fascinated by the remarkable chemistry of the actinide elements because of the interesting chemistry of the 5f orbitals.

(One of the "actinides," thorium, strictly has limited or no 5f chemistry, although its considered an actinide nonetheless, for convenience.)

One of the interesting things about the actinides, all of which are radioactive, is that they are excellent shielding materials for high energy radiation, owing to the fact that they have so many electrons - uranium, for example has 92 - making it possible for them to have many electronic transitions, and because they are massive, their inner electrons can absorb very high energy radiation to emit "Auger electrons."

Thus I was fascinated by a paper published recently in the wonderful - if overly dense - journal ACS Appl. Mater. Interfaces, specifically, this one: Highly Sensitive Detection of UV Radiation Using a Uranium Coordination Polymer, published by scientists at the Key State Laboratory of Radiation Medicine and Protection and the School for Radiological and Interdisciplinary Sciences and a few other institutions in Sozhou, China. (Wang et al, ACS Appl. Mater. Interfaces, 2018, 10 (5), pp 4844–4850)

(The Chinese government doesn't hate science quite as much as our government hates it, which is why they are going to eat us alive in the 21st century.)

Here's the introductory text from the paper:

Ultraviolet radiation is widely used in chemical industries, such as curing and photolithography, sterilization, surface modification technique, and so forth,1−3 but can exhibit either positive or negative impacts on human health. For instance, UV radiation is crucial for assisting human skin to produce vitamin D that is necessary in physiological processes.4 Excessive doses of UV radiation, however, impose great damage on the human body and may result in the development of cutaneous malignant melanoma (CMM) and non-melanoma skin cancer (NMSC),5 leading to premature skin-aging and eye disorders. 6,7 Besides these physical impacts, developing efficient UV photodetectors is also highly desirable in automotive, aerospace, environmental, and biological researches.7 Currently, various techniques have been developed to detect UV radiation both qualitatively and quantitatively. The most developed semiconductor photodetectors, including metal−semiconductor− metal (MSM) detectors,8 PIN photodiodes detectors,9 p− n junction diodes,10 and Schottky barrier detectors,11 often suffer from several disadvantages, such as sophisticated synthesis and manufacturing procedure, not being able to measure the accumulated UV dosage as well as high defect density in the material. The latter greatly lowers the detection sensitivity and efficiency.12


The authors propose a uranium based detector for the following reasons:

Uranium, the most critical 5f element in the nuclear fuel cycle, is chosen in this work as the metal center based on the following considerations. First, depleted uranium is an abundant long-half-life radioactive byproduct of the nuclear power industry that receives limited studies in luminescent coordination polymer systems compared with other metals. Second, uranyl luminescence originating from the HOMO− LUMO transition of hybridized molecular orbitals often exhibits brighter emission and more efficient absorption of UV light than trivalent lanthanides owing to the non Laporte forbidden nature which greatly extends the detection limit.34 Third, given the 5f/6d orbitals of uranyl are deeply involved in coordination, the luminescence is highly sensitive to the coordination environment, which affords more opportunities for developing detection ability (i.e., more efficient energy transfer).35


LUMO here refers to the "lowest unoccupied molecular orbital" and HOMO to the "lowest occupied molecular orbital." Transitions between molecular orbitals (or in some cases atomic orbitals), defined by quantum mechanics, determine the properties of radiation absorption and emission, not only at high energy levels such as those observed for UV, X-rays, and gamma radiation, but also in the visible range: Color is a function of these effects.

The authors synthesize a "MOF" - a "metal organic framework" - a class of materials that has been the subject of vast amounts of research in recent years. This particular framework is built from uranium atoms, nitroisophtalic acid and dimethylformamide.

Here's a graphic describing the structure of this framework:



The caption:

Figure 1. Crystal structure depictions of 1, where hydrogen atoms are omitted for clarity: (a) coordination environment of uranium(VI); (b) asymmetric unit of [UO2(L)(DMF)]; (c) 1D metal–organic chain of 1 composed of 5-nitroisophthalic acid linked asymmetric units; (d) pseudolayered structure comprising 1D chains coalescing due to π···π interactions. Atom colors: U = green, O = red, C = black, N = blue


Although the molecules luminescence nicely, after long term irradiation, the intensity of the luminescence fades:



The caption:

Figure 2. (a) UV dosage dependent luminescence spectra of 1 performed on a single crystal to show the quenching effect under 365 nm UV light. (b) Correlation between the quenching ratio and radiation dosage. Inset is the correlation between D/[(I0 – I)/I0 %] and the UV dosage. (c) is the corresponding luminescence photographs of a single crystal after receiving continuous UV radiation.


Surprisingly however, this effect seems not to relate to structural degradation of the molecular organic framework, which demonstrates remarkable structural integrity even upon irradiation with higher energy wavelengths, to wit, x-rays and gamma rays, as is shown in the XRD (X-ray diffraction pattern) graphics shown:



The caption:

Figure 3. (a) PXRD patterns for samples irradiated with UV, 100 Gy X-ray and 100 kGy γ-ray radiation. (b) EPR spectra of 1 before and after UV, 100 Gy X-ray, 100 kGy γ-ray radiations.


The EPR (Electron Paramagnetic Resonance) spectra clearly shows the persistence of free radicals, thought to reside on the dimethylformamide ligand:



The caption:

Figure 4. (a) Optimized geometry structure and bond parameters of ground state DMF molecule. (b) Optimized geometry structure, bond parameters (left), and net spin density (right) of triplet DMF· radical. (c, d) Simulated radical-free and radical-bearing coordination structures of the fragment, named as uranyl-5-NIPA-DMF and uranyl-5-NIPA-DMF·, respectively. Bond parameters are labeled below each structure.


I love this last graphic, because one doesn't get to look at electron density diagrams of molecular orbitals resulting from the mixing of f orbitals all that much:



The caption:

Figure 5. Density of states (DOS) of (a) the isolated uranyl molecule, (b) the uranyl-5-NIPA-DMF complex, and (c) the uranyl-5-NIPA-DMF· complex. The gray-filled and empty areas below DOS curves indicate the occupied and unoccupied states, respectively. For each DOS, the lowest unoccupied U(5f) orbital is normalized at 0 eV for convenience.


The authors thus conclude:

In summary, a highly stable uranium coordination polymer was successfully synthesized through solvothermal method that exhibits superior sensing property. The intrinsic luminescence of 1 could be quenched by UV which makes it suitable for monitoring UV radiation. The radical-induced quenching mechanism confirmed by EPR, X-ray crystallography, and DFT calculations studies corroborates this property of 1...

... This work provides us new opportunity for searching powerful UV responsive materials by taking advantage of efficient UV light asbsorber (uranyl) as metal center. We further noticed that many other uranyl hybrid materials constructed from different types of ligands and solvents may exhibit similar properties, which can be therefore fine-tuned by varying uranyl coordiation enviorments, crystal structures, and chemical constituents (e.g., light sensitizer), and the systematic investigations are in progress. We also believe this work offers new insight into methods in which depleted uranium may be reused for beneficial purposes.


It's a fine paper, but I will note that my preferred use for depleted uranium is as a precursor to plutonium as a nuclear fuel.

The interesting thing for me about this paper is the stability of this framework in a high radiation field. This suggests it's use as a "breathable" nuclear fuel, albeit one that would operate in a thermal spectrum, thus of use in thorium derived U-233 systems as opposed to plutonium breeding systems.

An interesting paper I think.

Have a nice weekend.

Can we eliminate the emissions of the greenhouse and ozone depleting gas N2O from nylon manufacture?

Nitrous oxide, N2O, aka "laughing gas" is no laughing matter.

Other than carbon dioxide, it is the atmospheric pollutant that most troubles me, not just because it is a profound greenhouse gas with a climate forcing potential 120 times as large as carbon dioxide, but also because it is an ozone depleting agent.

There is no really great way to eliminate human emissions - like carbon dioxide it has always been a natural component of the atmosphere, but anthrogenic emissions have swamped natural emissions - because the emission of nitrous oxide is an inevitable consequence of fertilizing soil for agriculture, without which a huge fraction of the planet's population would literally need to starve to death.

However, going through some scientific literature I collected a few years back but never properly filed in my computer's filing system, I was surprised to learn that between 5 to 8% of nitrous oxide emissions are an industrial side product of nylon manufacture.

The paper to which I refer is here: One-pot room-temperature conversion of cyclohexane to adipic acid by ozone and UV light (Kuo Chu Hwang*, Arunachalam Sagadevan, Science 19 Dec 2014:
Vol. 346, Issue 6216, pp. 1495-1498)

A key intermediate in the manufacture of the nylon polymer is the diacid adipic acid which has the following structure:



Nylon 66 has this structure:



Adipic acid is made from a constituent of the dangerous fossil fuel petroleum, cyclohexane, by oxidation with pressurized oxygen at 125C over a manganese and cobalt catalyst to give a mixture of cyclohexanol and cyclohexanone. These are passed over ammonium vanadate and cupric catalysts in the presence of 65% nitric acid (itself made by oxidation of ammonia prepared using dangerous natural gas) to give adipic acid.

During this process, the reductant is nitric acid, which is converted to N2O, which is then dumped into our favorite waste dump, the planetary atmosphere.

World production of adipic acid is on the order of a billion kg.

Some brief excerpts from the text:

Adipic acid is a precursor for the synthesis of the nylon-6,6 polymer and, as such, is one of the most important industrial chemical intermediates. More than 3.5 million metric tons of adipic acid were produced in 2013, reflecting a ~5% growth rate per year over the past 5 years (1, 2). Nearly 95% of the worldwide industrial production of adipic acid employed the nitric acid oxidation method (3). The first step is air oxidation of cyclohexane under high temperatures (125° to 165°C) and high pressure (8 to 15 atm) to produce KA oil (i.e., a mixture of cyclohexanone and cyclohexanol) with 4 to 11% conversion and ~85% selectivity (4, 5). In the second step, nitric acid is applied as an oxidant: the conversion is ~100%, and the selectivity for adipic acid is 93 to 95% with some other short-chain acids as side products (see Fig. 1A). The process requires the nitric acid–to–KA oil ratio to be maintained at 40:1. Disadvantages of the current industrial process include low overall product yield; corrosion of reaction vessels by nitric acid; emission of the ozone-depleting greenhouse gas N2O; and high energy consumption. It was estimated that ~0.3 kg of N2O gas is formed per kilogram of adipic acid produced (6, 7)...

...Inspired by literature reports that ozone and ultraviolet (UV) irradiation are primarily responsible for oxidative degradation of most hydrocarbons in the atmosphere, we sought to investigate whether both treatments in combination could oxidize cyclohexane, which exclusively contains unactivated sp3 C-H bonds. In a simple experiment, ozone gas was bubbled through neat cyclohexane with concurrent UV irradiation at room temperature. No metal catalyst or solvent was used. After 2 to 8 hours, a solid product gradually precipitated to the bottom of the reaction vessel (see Fig. 1B and fig. S1 for reaction scheme and pictures, respectively). A portion of the liquid cyclohexane evaporated due to the O3 gas bubbling. The solid oxidation product of cyclohexane was subjected to 1H nuclear magnetic resonance (NMR) and 13C NMR analysis (in deuterated chloroform) for structure characterization and proven to be adipic acid.


UV radiation can be continuously supplied by exposing BaF2, barium fluoride, to a gamma emitting radioactive substance, these being available in large quantities from used nuclear fuel. There are many ways to generate ozone, although the usual method is to generate it electrochemically.

I have no idea if there has been any effort to industrialize this most interesting bench chemistry, but this is a beautiful, if esoteric environmental idea.

I can't believe I overlooked this very beautiful paper for a couple of years.

Have a very pleasant weekend.











Lead Free Perovskite Solar Cells Predicted.

The paper to which the title of this post refers is this one: Predicted Lead-Free Perovskites for Solar Cells (Roshan Ali, Guo-Jiao Hou, Zhen-Gang Zhu, Qing-Bo Yan, Qing-Rong Zheng, and Gang Su,*Chem. Mater., 2018, 30 (3), pp 718–728) Excerpts and graphics from the paper "predicting" lead free perovskite solar cells will be below.

First though, I love the title, "...Predicted."

During my whole adult life - I'm not young - I've heard wonderful predictions about solar energy.

This one, from 1976 is my favorite:

In June 1976 the Institute considered that with a conservation program far more modest than that contemplated in this article, the likely range of U.S. primary energy demand in the year 2000 would be about 100-126 quads, with the lower end of the range more probable and end-use energy being about 60-65 quads. And, at the further end of the spectrum, projections for 2000 being considered by the "Demand Panel" of a major U.S. National Research Council study, as of mid-1976, ranged as low as about 54 quads of fuels (plus 16 of solar energy)


(Source: Amory Lovins, Energy Strategy, The Road Not Taken? Foreign Affairs,, October, 1976 pp. 65-95, excerpt on page 76.)

It's my favorite because there is no reference to the report of "The Institute," they are merely evoked. (The Institute in question was the "Institute of Energy Analysis," which I believe was headed by Alvin Weinberg, the chief developer of the Pressurized Water Nuclear Reactor that Amory Lovins has spent a career despising. Lovins has since had a wonderful career "consulting" for companies like SunCor, which is not a solar company but is rather a Canadian Oil Sands company, which (since it pays Lovins) can tout itself as a "sutainable" oil sands company and which is only one of the greasy fossil fuel companies for which the "green" anti-nuke Lovins consults.

The age of doublespeak is hardly limited to that other asshole Trump.

Lovins also predicted in 1980 that nuclear energy would die by 2000 (or else there would be a nuclear war) but that's another story.

Anyway, a "Quad" is quite nearly an exajoule (EJ) - there's 1.055 EJ to a Quad. Lovins was, without citation, claiming that a little birdie told him that he was free to imply that "by 2000" the US would be consuming 54 quads plus, 16 of solar energy, a total of 70 exajoules.

Current US energy consumption is near his predicted lower end in his first unreferenced assertion, roughly 100 exajoules. However the world as a whole, added another 126 exajoules of consumption since 2000 (it's now widely reported to be 2018) to reach a total of 576 exajoules (as of 2016, the last year for which data's been compiled by the International Energy Agency.)

On the entire planet, as of 2016, the commercial solar industry was not producing 10 exajoules of solar energy, never mind 16 in the United States. In fact, solar and wind combined did not, as of 2016 produce 10 exajoules.

The fastest growing source of energy worldwide from 2000 to 2016 was coal, which increased by more than 60 exajoules to 157 exajoules total.

As a result, the concentration of the dangerous fossil fuel waste carbon dioxide has averaged annual increases of just under 2.2 ppm all through the 21st century, after averaging less than roughly 1.3 ppm in the 20th century, beginning with measurements in 1958.

In 1976, when Lovins wrote this appalling garbage, mean carbon dioxide concentrations were 332.04 ppm; in 2017 they were 406.53 ppm.

A prediction: No one now living will ever see a value for the concentration of the dangerous fossil fuel waste carbon dioxide below 400 ppm, and the reason is that there is little hope that any of us will stop lying to ourselves.

Solar energy is the predicted future, and, regrettably, the future will be the same as the past.

So much for "predictions."

Solar energy is also "clean" and "green," except when it's not.

The most efficient solar materials - generating just tons of excitement in the primary scientific literature - is the "perovskite" structured materials.



Let's turn to the cited paper about the latest "solar breakthrough" du jour, and I'm speaking as an old man who used to get excited by "solar breakthroughs" day after day, going back to the time I was thin and had hair, back in the days when Amory Lovins was declared "a genius." - a long time ago

The authors write in the introduction:

The discovery of organic–inorganic halide perovskites, especially, methylammonium lead triiodide, CH3NH3PbI3 (MAPbI3), and formamidinium lead triiodide, HC(NH2)2PbI3 (FAPbI3), as light absorbers has brought a rapid development in photovoltaics (PV) technology.(1-11) These perovskites contain earth-abundant essential elements, making them highly promising for low-cost and large-scale PV applications. In 2009, Kojima et al.(1) for the first time investigated a MAPbI3-based solar cell with power conversion efficiency of 3.8%. Later, Lee et al.(12) and Kim et al.(3) improved the efficiencies remarkably up to 10.9% and 9.7%, respectively. These works arouse a great passion of studying these materials and the techniques to promote the performance and efficiency. The record efficiency for perovskite solar cells now stands at 22.1%,(13) which is somehow comparable to the crystalline silicon, today’s leading PV technology (25.3%)...

...MAPbI3 is a direct-gap semiconductor, with experimental bandgap of 1.55 eV.(18) It has strong and very sharp absorption, almost 25 times higher than that of Si yet better than GaAs.(19-21) They have long-lived photogenerated electrons and holes and have long charge diffusion length.(22-25) Due to the small electron–hole effective masses, the ambipolar transport is high.(26) In MAPbI3, dissipationless absorption and emission of photons were observed, which enable photons to recycle, leading to utilization of photons within the active layer.(27)


We're saved.

Or maybe not. In solar papers it's rare (though less and less unknown) to wonder about how "green" this technology really is. The authors continue:

Another important and serious issue is the presence of lead in these solar cell materials. As PV panels are normally placed in open field or on the roof of houses, their exposure to rainfall is unavoidable. In the presence of rain and moisture, PbI2 degrades as a substance that may cause severe health problems, i.e., from cardiovascular and developmental diseases to neurological and reproductive damages, increasing oxidative stress.(35) Furthermore, lead pollution has serious impacts on soil and water resources, greenhouse gas emissions, and abundance of material inputs.(36-38) To remove the toxicity of Pb in solar cells, one may either develop an effective method of encapsulation and recycling all components of the PV panels at the end of their lifetime or replace Pb by other nontoxic elements in halide perovskites. For the latter one, the Pb-free perovskites should have excellent absorption, having suitable and direct band gaps comparable to MAPbI3. Also the alternative Pb-free perovskite must exist in the range of tolerance factor (0.81–1.11)(39, 40) to ensure the structural stability of the perovskite solar cell.


The authors begin then to evaluate cogeners and other materials that might replace lead.

This is a computational paper utilizing computer modeling to predict what might replace lead, which is proposed to replace among others, the toxic element cadmium, now in use (as a compound with the toxic elements selenium or tellurium) is some "green" and "distributed" solar cells.

Some pretty pictures from the paper, beginning with the evocative opening "eye catcher" graphic:




The lead perovskite structure along with the structures of some computationally evaluated putative perovskite structures:




The caption:

Figure 1. Supercell structure of MAPbI3 is shown from a front view in (a) and a side view in (b). Supercells are shown for MA(Ca0.125Si0.875)I3 in (c), for MA(Ca0.375Si0.625)I3 in (d), and MA(Ca0.5Si0.5)I3 in (e).


One of the issue with these wonderful perovskite solar cells that will save the world someday (we predict) is that they are structurally unstable, as alluded to in the previous text. One of the powerful things that computational chemistry can do is to predict structure, based on thermodynamic parameters such as the enthalpy or free energy. This kind of data has been incorporated into a factor denoted as the "tolerance factor."

It's plotted here:




The caption:

Figure 2. Tolerance factor (t), black in color, represents the perovskite phase stability for all mono- and mixed-replaced materials. The two dotted black lines represent the tolerance factor range. The red curve represents our calculated formation enthalpy. The blue and magenta color triangles represent the previous calculated enthalpy formation values, while the green square represents the experimental formation enthalpy for MAPbI3. Materials below the horizontal red-dotted line show thermodynamic stability.


Next we have a periodic table talking about the elements in the "predicted" solar cells.



The caption:


Figure 3. Pb-replaced (12 in total), unreplaced (due to smaller ionic radii; 17 in total), metallic (30 in total), highly toxic (12 in total), and mixed (Ca/Si, Zn/Si) Pb-replaced elements are tabulated in the periodic table.


A note on this periodic table. Two of the elements identified here as "toxic" are already found in commercial solar cells; they are cadmium and arsenic. Two of the "replacement" elements are also found in solar cells, gallium (Ga) and germanium (Ge). Both of these latter elements are considered "critical elements" meaning that their long term supply is not guaranteed for future generations.

This calls into question the use of the term "renewable" to describe this stuff.

Another element included in solar cells is probably the most threatened element in the periodic table, indium.

Indium, which is an impurity in zinc (and a few other) ores is a constituent of a semiceramic material known as ITO (Indium Tin Oxide) which has the unique property of being both an electric conductor and being transparent. It is widely utilized in all touch screen devices, including (the major use, since the solar industry remains trivial) cell phones.

The following graphic shows that the perovskite solar cells as designed (and modeled here) contain ITO. So much for "renewable," at least so far as these cells are concerned.



The caption:

Figure 4. (a) Schematic structure of the simulated device, with a single layer perovskite. (b) The dielectric function ϵ2 and (c) the absorption efficiency of the simulated device with the active Pb-free perovskite layer of MAPbI3, MAGeI3, and MASnI3.


Some technical stuff, the bandgap width:



Figure 5. Bandgap values of our mixed study MA(Ca/Si)X3 and MA(Zn/Si)X3(where X= I, Br, Cl). The red dotted line (1.3 eV) shows the ideal band gap for a single-junction solar cell according to the Shockley-Queisser theory. The blue dash-dot line (1.8 eV) shows the ideal band gap for the top-cell in tandem solar cells.


Schockley, for a little bit of history, holds the record for being the most racist Nobel Laureate ever, although he is in a three way tie with Phillip Lennard and Johannes Stark for this dubious distinction, with the (dis)honorable runner up being James Watson.

Now the punchline, the "imaginary" part of the diaelectric function:



The caption:

Figure 6. (a) Imaginary part of dielectric function (ε2) and (b) Total device absorption efficiencies (single layer) for methylammonium Pb-free triiodides, MACa0.125Si0.875I3, MACa0.375Si0.625I3, MACa0.5Si0.5I3, and MAZn0.5Si0.5I3 in comparison to MAPbI3. The device architecture of solar cell is the same as in Figure 3a.


The imaginary part...

This "imaginary" of course refers to the fact that the function is a complex function, a type of function that appears quite a bit in mathematical physics and mathematical physical chemistry, most notably in quantum mechanics but also in places like cubic equations of state, like for example, the very widely utilized Peng-Robinson equation for real gases. "Imaginary" here refers of course to the square root of -1, which does not exist except that it does exist as an essential mathematical construct for understanding the universe.

But in the solar case, I also insist - although this is not what people want to hear, although I think it is what they should here if they actually give a rat's ass about climate change, not that anyone, right or left actually does - the imaginary part has a deeper meaning.

The solar industry did not work to arrest climate change; it is not working; and it will not work, and the reason is energy to mass ratios.

And these ratios, the requirement for distribution in what will surely prove an irretrievable way is why so called "renewable energy" will never be as clean, as safe nor as sustainable as nuclear energy. There is not enough matter on the planet, and in particular non-toxic matter to make the solar scheme work, and I haven't even touched the other magic touchstone so often evoked with it, the chemistry of chemical batteries.

I suppose on Valentine's day evening, one should expect to hear what one wants to hear, but I'm not a good guy.

I hope you had a pleasant evening nonetheless.

Mass Spectrometry of DNA Adducts: Resolving the Mechanism of How Air Pollution Induces Cancer.

Leafing through my files today, I came across a review article that I'm sure I read, or partially read, in the past, but which is a pleasure to read again.

It is here: Mass Spectrometry of Structurally Modified DNA (Natalia Tretyakova, Peter W. Villalta, and Srikanth Kotapati, Chem. Rev., 2013, 113 (4), pp 2395–2436)

Although this is basically a scientific post, it is on a political website and it is therefore worth noting that all three authors of this paper then (and perhaps still) working at the University of Minnesota are immigrants, one from Canada, one from India, and one from Russia.

This is worth noting in the time of Hair Fuhrer, the uneducated nepotist criminal unintelligent moronic nativist bankruptcy king who lounges in the White House trying to destroy his country with the help his Spokesperson Paul Ryan working in the House, and his equally stupid bigoted apologist in the Senate, Mitch McConnell. All three of these puerile, horrible fools are far worse traitors to both the spirit, promise, and legal structures of this country than these three fine scientists could ever be. The self declared "Real Genius" in the White House would be barely qualified to wash glassware in these people's lab, not that stupid people should be allowed in labs at all in any capacity.

Sorry, I couldn't resist.

The science:

As an advocate of the rapid expansion of nuclear power, I am often confronted with people who want to prattle on about Fukushima (or Chernobyl) as if they were the worst energy disasters of all time. I point out that this is absurd since, for example, the Banqiao dam disaster killed close to 200,000 people, possibly even more in 1976 in a matter of days, not that anyone gives a shit about these deaths. (The death toll varies depending on where you read about it, and the real number will almost certainly never be known.) But the Banqiao dam disaster, is still not the greatest energy disaster of all time, not at least in my book.

The greatest energy disaster of all time is the on going and continuous disaster of air pollution, which as I often point out using the following link, kills approximately 7 million people a year, every year:

A comparative risk assessment of burden of disease and injury attributable to 67 risk factors and risk factor clusters in 21 regions, 1990–2010: a systematic analysis for the Global Burden of Disease Study 2010 (Lancet 2012, 380, 2224–60: For air pollution mortality figures see Table 3, page 2238 and the text on page 2240.)

This does not include deaths owing to the other effect of air pollution, climate change.

Air pollution kills in a variety of ways: A large fraction of the deaths take place in children under the age of 5, because of their poorly developed respiratory systems coupled with other environmental insults to their physiology, but the DALY (disability adjusted lost years) of life also involves lung cancer among the adult lives lost to air pollution, which develops over a number of years, and before killing its victims, seriously disables them and leaves them in great pain.

The scientific review article cited above explains how air pollutants cause cancer, that it, it explores the analytical chemistry elucidating the mechanism by which air pollutants are carcinogenic.

The mechanism is basically this: Many air pollutants are fairly flat molecules that fit into the grooves (minor and major) that characterize the famous helical structure of DNA. Once there, they are in a position to chemically bond directly to the functional groups associated with DNA molecules. This is in contrast to the epigenetic modification of DNA (and RNA) which is the natural biochemical modification of the 5 nucleobases that make up these molecules for purposes of affecting cellular biology.

In their introduction the authors briefly describe epigenetic modifications:

Epigenetic DNA modifications such as 5-methylcytosine (MeC) are important regulators of cell function that influence chromatin structure and control the levels of gene expression. DNA methyltransferases (DMTs) catalyze the addition of the C-5 methyl group to cytosine nucleobases.(1) DMTs preferentially recognize hypomethylated 5′-CG-3′ sequences, producing epigenetic modifications which preserve DNA methylation patterns. C-5 cytosine methylation controls gene expression by mediating the binding of specific proteins (methyl-CpG binding proteins) to MeCG sites, followed by the recruitment of histone-modifying enzymes that promote chromatin remodeling.(2) Recent studies have discovered additional cytosine modifications, e.g., 5-hydroxymethyl-C, 5-formyl-C, and 5-carboxyl-C; these modifications have been hypothesized to be demethylation intermediates or they may have their own unique epigenetic functions within cells.(3-5)


Continuing they then describe the difference between normal epigenetic modifications of nucleobases to describe the odious effects of air pollution:

In contrast to epigenetic modifications, chemical DNA damage including nucleobase alkylation, oxidation, deamination, and cross-linking occurs at a variety of sites, including the N-7, O-6, C-8, and N-2 of guanine; the N-1, N-3, and N-7 of adenine; the O-2 and O-4 of thymine; and the O-2 and N-4 of cytosine (Scheme 1 and Chart 1).(6) Some carcinogens are inherently reactive toward DNA, while others must first be metabolically activated to electrophilic intermediates (e.g., epoxides, quinone methides, diazonium ions, and nitrenium ions), which subsequently bind to DNA, producing nucleobase adducts (Figure 1).(6) All living cells contain extensive DNA repair systems responsible for removing nucleobase lesions. If structurally modified DNA bases escape repair, they may induce base mispairing during DNA replication; in this case, the chemical damage is converted into permanent genetic damage (mutations).(6) Accumulation of mutations in genes controlling cell growth, proliferation, programmed cell death, and cell differentiation is likely to cause cancer.(7-10)


The bold is mine.

Here, from the paper, is a graphic describing sites where the nucleobases are subject to modification.



(Uracil, desmethyl cytosine, associated with RNA is not shown here.)


They immediately show some of the adducts they will discuss in the paper:



Chart 1. Structures of Representative DNA Adductsa
a1,N6-etheno-2′-deoxyadenosine (εAdo); 3,N4-etheno-2′-deoxycytosine (εdCyd); O6-methyl-2′-deoxyguanosine (O6-Me-dG); N7-methylguanine (N7-Me-G); 8-oxo-7,8-dihydro-2′deoxyguanosine (8-oxo-dG); 8-oxo-7,8-dihydro-2′deoxyadenosine (8-oxo-dA); N7-ethylguanine (N7-ethyl-G); 1, 1,N6-(1-hydroxymethyl-2-hydroxypropan-1,3-diyl)-2′-deoxyadenosine (1,N6 -αHMHP-dA); 1,N6-(2-hydroxy-3-hydroxymethyl-propan-1,3-diyl)-2′-deoxyadenosine (1,N6 -γHMHP-dA).


Then there's a little cartoon about how this all works:



The caption:

Figure 1. Central role of DNA adducts in chemical carcinogenesis. Adapted with permission from Reference 55. Copyright 2011 American Chemical Society.


The point made here is that sometimes, probably most of the time cells with damaged DNA either repair the DNA or die, which is a usually a good thing. However sometimes the cells survive, and, particularly if the damaged DNA is involved in the regulation of cell division, mutate into cancer cells. Reference 55 is here: Quantitation of DNA Adducts by Stable Isotope Dilution Mass Spectrometry (Natalia Tretyakova, Melissa Goggin, Dewakar Sangaraju, and Gregory Janis, Chem. Res. Toxicol., 2012, 25 (10), pp 2007–2035)

Further down they give an even broader picture of DNA modified by air pollutants, a picture that is rather scary actually:



The caption:

Chart 4. Structures of DNA Adducts Highlighted in Section 5.5a
aN7-(2′-Hydroxyethyl)guanine (N7-HEG); 5-hydroxymethyl-2′-deoxyuridine (HmdU); 3,N4-ethenocytosine (εCyt); 7-(1′,2′-dihydroxyheptyl)-3H-imidozo(2,1-i)purine (DHH- εAde); 1,N6-ethenoadenine (εAde); N2,3-ethenoguanine (N2,3-εGua); 1,N2-ethenoguanine (1,N2- εGua); 4-hydroxyestrogen-1-N3-adenine (4-OH-E-1-N3Ade); 1,N6-etheno-2′-deoxyadenosine (εdAdo); 3,N4-etheno-2′-deoxycytidine (εdCyt); 1,N2- etheno-2′-deoxyguanosine (1,N2- εdGuo); O2-ethylthymidine (O2-edT); O4-ethylthymidine (O4-edT); 1-(guan-7-yl)-4-(aden-1-yl)-2,3-butanediol (N7G-N1A-BD); 1,4-bis-(guan-7-yl)-2,3-butanediol (bis-N7G-BD); N2-hydroxymethyl-2′-deoxyguanosine (N2-HOMe-dG); N7-ethylguanine (N7-Ethyl-G); N-(deoxyguanosin-8-yl)-PhIP (C8-dG-PhIP); 10-(deoxyguanosin-N2-yl)-7,8,9-trihydroxy-7,8,9,10-tetrahydrobenzo[a]pyrene (dG-N2-B[a]P); 7-(deoxyadenosin-N6-yl)aristolactam I (dA-AL-I); 7-deoxyguanosin-N2-yl aristolactam I (dG-AL-I).


To be fair to people who don't give a shit about the worst energy disaster of all time, air pollution, but would rather engage in the use of electricity that almost certainly involves the combustion of dangerous fossil fuels to go on their computers to whine about Fukushima and Chernobyl, it does seem to me that a few of these adducts probably derive from pollutants other than air pollutants. For example, dG-C8–4-ABP probably derives from a water pollutant like a partially dehalogenated PCB. Others are almost certainly derived from air pollutants, for example dG-AI-I looks like it comes from a lignin derived combustion product of that wonderful "renewable" fuel wood, which is a large participant (along with straw) in about half of the 7 million air pollution deaths that take place each year, mostly among poor people, although wood burning is very popular, and, as Valentine's day approaches, considered very "romantic" in the first world.

Cigarette smoking is the combustion of biomass, just saying...

The review article is of interest to the analytical chemist, and there's a very nice overview of various types of mass spectrometry instruments, triple quads, orbitraps, Q-traps, TOF instruments etc, etc, as well as wonderful descriptions of sample preparation.

The mass spectrometer is clearly one of the most important tools ever invented for investigating the world, whether the topic is carcinogenisis, therapeutics, air and water pollution, extraterrestrial chemistry, what have you. It is very unlikely that J.J. Thompson, genius that he was, could imagine where the discovery of the electron would take science.

Unbelievable.

In any case, this paper should represent a subtle warning to anyone who actually cares about environmental science about what is clearly - if not to everyone else, at least to me - the worst energy disaster of all time, air pollution. This disaster has been taking place for a long time, and it will not stop until we clear our minds and think anew, until we pay attention..

Not so long I had an unpleasant discussion on the internet with one of those "FUKUSHIMA!!! FUKUSHIMA!!! FUKUSHIMA!!!" assholes who insist on contemplating their navels while the planet dies.

This person, who informed me that he or she was a "heavy ion physicist" (as opposed to a nuclear physicist, since "nuclear" is apparently a bad word) said that Fukushima was the worst disaster of the 21st century because, to paraphrase, "one could calculate the excess cancers from it."

He or she felt qualified to inform me of this fact because he or she claimed to have a Ph.D. As someone who has met thousands of Ph.D's, if not tens of thousands, over a long life, I have a perspective on what that degree qualifies one to say or do on any variety of subjects, but no matter, famously:



Happily for me, I will never interact with this person again.

Nevertheless, I, for example, could be a greeter at a Walmart who never graduated from elementary school, but it has no bearing whatsoever on the truth or falsity of any of the above.

To Wit: Donald Trump was awarded an MBA from the Wharton School of Business, but apparently that only qualifies him to drive businesses, and apparently whole countries into bankruptcy.

Having a Ph.D. doesn't prevent you from being an asshole, even an ignorant asshole.

Some simple arithmetic with some very basic assumptions:

If Fukushima were to cause 10,000 "eventual" cancers - it won't but if it did - and if only 10% of the 7 million air pollution deaths involved lung (or other) cancer, then the total cancer loss from Fukushima would be on the order of about 5 or 6 days worth of air pollution cancer deaths.

Fukushima is the result of a massive earthquake which by the way also killed 20,000 people, not from radiation, but because they happened to live in a coastal city not that anyone is interested in banning coastal cities.

Air pollution, by contrast to the reactor failures at Fukushima, does not require an earthquake to kill people. It kills people when its primary source, dangerous fossil fuel and biomass combustion operates normally.

This bears repeating. If we pay only selective attention to energy disasters as opposed to full attention involving risk/benefit calculations - because no decision of any kind will ever lead to risk free situations - we subject ourselves to the greater risk doing great harm to the future of humanity, and not just humanity, but to the very beautiful world to which we have had the good fortune to see.

I wish you a pleasant Sunday afternoon.



Radiolytic degradation of CFCs.

In one of the rare successes of an environmental treaty, the CFC's, chlorofluorocarbons, were banned internationally by the 1987 protocol because of their potential for depleting ozone.

However these species, which are also greenhouse gases, are long lived in the atmosphere, and many remain in old refrigerators, air conditioners and even spray cans. Thus they are still present in the atmosphere.

They degrade by termination of chain reactions, induced in the upper atmosphere, primarily by interaction with UV, X-ray, and gamma radiation associated with outer space and the high ionosphere.

High energy radiation is of course, available in the lower atmosphere either by the use of accelerators - from a radiochemical perspective the most often utilized energy consuming tool in this regard is the electron beam - or from the decay of radioactive materials, most commonly in the lab either Co-60 made by bombarding natural cobalt with neutrons in a nuclear reactor, or by use of the fission product cesium-137, which is available on a macroscopic scale.

Most often when I look for literature on this subject, I am mostly concerned with halogenated species in water, for example the famous PCB's which continue to pollute the Hudson River, but while going through such literature today, I came across a study on the degradation of CFC's.

The paper is here: Chain reaction on de-halogenation of 1,2-dibromotetrafluoroethane and 1,1,2-trichlorotrifluoroethane induced by irradiation in alcohols (Nakagawa, Radiation Physics and Chemistry Volume 108, March 2015, Pages 29-32

It's a brief but interesting paper.

Some brief excerpts:

Chloro-fluoro aliphatic carbons (CFC) and bromo-fluoro aliphatic carbons (Halon) are considered environmental pollutants. Some techniques have been studied to decompose halogenated carbons. Irradiation with gamma-rays or high-energy electrons in alkaline 2-propanol solution seems to be one of the effective methods for degradation of chlorinated carbons, not only CFCs but also polychlorinated aromatic carbons, such as polychlorinated dibenzo-p-dioxins (PCDD), polychlorinated biphenyls (PCB), polychlorinated phenols (PCP), polychlorinated benzenes (PCBz), and so on. There are many reports on the degradation of chlorinated carbons, and the reaction mechanisms have been well studied (Mucka et al., 1997; Schmid et al., 1997; Schmelling et al., 1998; Yamamoto and Tagawa, 1999; Hirota et al., 2000; Nakagawa and Shimokawa, 2002). On the contrary, few studies on the decomposition of brominated carbons exist. Though also investigated the degradation of 1,2-dibromotetrafluoroethane (Halon2402) in alkaline 2-propanol solution, they could not observe the product Halon2401, produced from the substitution of one of the bromine atoms in Halon2402 with a hydrogen atom. It is suspected that the mechanism for decomposition of Halon2402 in 2-propanol solution is entirely the same as that of chlorinated carbons.

In this report, the degradation of Halon2402 induced by irradiation in 2-propanol and methanol was studied in detail with careful de-oxygenation, and the charge transfer from an alcohol radical to Halon2402 was found to be the trigger of the chain reaction in pure alcohol


In this paper both Co-60 and Cs-137 were utilized.

It was found that in both methanol and isopropanol (rubbing alcohol) both bromo and chloro fluorocarbons were dechlorinated and or debrominated. However methanol was less efficient and detectable amounts of the probably inert (but still a greenhouse gas) tetrafluoroethylene was formed from the halon 2402 gave measurable yields (by Gas Chromatography) tetrafluoroethylene aka 1,1,2,2-tetrafluoroethene.

The halides formed were measured by old fashioned chemistry, a Mohr's titration, and so it is not clear the extent to which defluorination took place, since Mohr's titrations do not really distinguish between halides, if I recall their chemistry well.

Defluorination is a tougher not than dechlorination or debromination, but not actually impossible, at least with gamma radiation, particularly where gaseous or liquid water is available.

These reactions were conducted in alcoholic solvents in the absence of catalysts like titanium dioxide.

Thus as a practical matter, they are only applicable to the destruction of isolated CFC's.

Of course, the same chemistry as takes place in the upper atmosphere would also work at ground level. Ozone is essential in the upper atmosphere, but at ground level it is a serious air pollutant with huge health consequences. Irradiation of air, therefore, containing CFC's - as all air now does - would therefore destroy ozone. Further, owing to the Maxwell-Boltzmann distribution, CFC's, being relatively heavy molecules in comparison to air - which has a density very close to that of pure nitrogen - is far more concentrated at ground level than in the upper atmosphere.

The storage of radioactive materials in highly polluted cities would therefore mitigate these health issues significantly. However, realistically, there is too much fear and ignorance surrounding nuclear materials for that wise decision ever to happen, but well, the supposition that ignorance is not good for health is not a new concept and is well established and regrettably, widely observed.

I wish you a pleasant Sunday.

Electrolytic reduction of carbon dioxide to formate using low over-voltages.

Here's a fun paper: Highly Selective Reduction of CO2 to Formate at Low Overpotentials Achieved by a Mesoporous Tin Oxide Electrocatalyst (Rahman Daiyan, Xunyu Lu*, Wibawa Hendra Saputera, Yun Hau Ng , and Rose Amal* ACS Sustainable Chem. Eng., 2018, 6 (2), pp 1670–1679)

Let me tell you something: Anyone with a name like Wibawa Hendra Saputera is definitely cooler than I will ever be, probably cooler than you'll ever be too.

Here's the introduction to the paper, what it's about:

Rising level of CO2 accumulation in the atmosphere has attracted considerable research interest in technologies capable of CO2 capture, storage, and conversion.(1-3) The electrochemical reduction of CO2 into high-value liquid organic products could be of vital importance to mitigate this issue.(4, 5) The direct conversion of CO2 to liquid fuel using renewable energy, which can readily be integrated with the current infrastructure, will help realize the creation of a sustainable cycle of carbon-based fuel that will promote zero net CO2 emissions.(6-10) Despite initial promising findings, significant progress is required in improving the production rate, efficiency, stability, and cost to make this technology realistic for large-scale utilization.(7, 11)

The current benchmarking electrocatalysts for CO2RR to formate (HCOO–) are sp group metals, notably, Pb, In, and Sn.(12-19) Among the high-performing materials, Sn-based catalysts are especially favored due to their relative low cost, abundance, and nontoxic properties, compared to Pb and In catalysts.(20) Sn catalysts however exhibit certain characteristics, for instance, the local chemical structure of Sn is shown to play a major role in CO2RR, as the bulk Sn foils are reported to have inconsistent formate Faradaic efficiency (FEHCOO–) at a wide range of potentials.(16, 21) To address such discrepancy in catalytic performances, numerous studies on the effect of electrolyte, pH, morphology, and catalyst deactivation for CO2RR with Sn-foil-based catalysts have been undertaken.(22-25) In spite of the insights and understanding into the mechanisms obtained by such studies, Sn-foil-based catalysts still require large overpotentials to attain high values of FEHCOO–. For example, three-dimensional Sn foam grown on Sn foil catalysts require a large applied potential of −1.3 V (vs RHE, applies for all potentials mentioned in this study) to achieve a FEHCOO– of 90%.(26) Similarly, the heat-treated Sn dendrite electrodeposited on Sn foil is also reported to convert CO2 to formate with a moderate FEHCOO– of 71% but this is also done at a large negative applied potential of −1.35 V.(22)


With all due deference to Wibara, this statement is a little off:

The direct conversion of CO2 to liquid fuel using renewable energy, which can readily be integrated with the current infrastructure, will help realize...


The current infrastructure contains very little so called "renewable energy;" overall the fraction of fossil fuels representing world energy portfolios is rising, not falling. In 2000, 80% of world energy came from dangerous fossil fuels. In 2016 (the latest data available) 81% of world energy came from dangerous fossil fuels.

Capturing carbon dioxide using electrical infrastructure that is almost entirely fossil fuel based is simply a perpetual motion machine.

But in theory, if not in practice, clean electricity is potentially available, albeit not from so called "renewable energy.'

No matter.

Some cool pictures of how they make their tin oxide mesoporous catalyst:



The caption:

Scheme 1. Fabrication of m-SnO2 Catalyst


A description of what's going on:

Mesoporous SnO2 was prepared by nanocasting method using KIT-6 as the hard template. KIT-6 was fabricated using an established method.(46) Briefly, 2 g of P123 (Pluronic P-123, Sigma-Aldrich, 99%) was dissolved in 72 mL of deionized water, followed by the addition of 2.5 mL of HCl. Then 2.47 mL of butanol was added dropwise and the mixture was stirred for a duration of 1 h at 35 °C. The solution was then transferred to a hydrothermal reactor and heated to 100 °C for 24 h. The solid product formed was then filtered and calcined at 600 °C for 5 h. To prepare mesoporous SnO2, 1.75 g of tin(IV) tetrachloride pentahydrate (SnCl4·5H2O, Sigma-Aldrich, 99%) was dissolved in 30 mL of ethanol. Then 0.6 g of KIT-6 was added and the mixture heated to 70 °C to evaporate ethanol. The sample was then calcined at 600 °C for 3 h. The impregnation and the calcination process were repeated again with two thirds of the Sn precursor used in the first step to complete the nanocasting process. The KIT-6 templates were then removed by washing the calcined powder twice in a hot 2 M NaOH solution. The resulting samples were collected by repeated centrifugation and washing with deionized water.


KIT-6 is mesoporous silica. I don't know how it's made, but I could look it up, but I'm short on time.

Here's some micrographs of the product anyway:



One of the interesting things about this paper is that the species being reduced is not carbon dioxide but rather the potassium bicarbonate salt. Electrolytic reduction of carbon dioxide is always limited by the low solubility of the gas in water, however the bicarbonate salt (which is made by the absorption of carbon dioxide into basic solutions) is very soluble.

The conclusion:

In summary, mesoporous SnO2 catalyst prepared by a simple and facile nanocasting method using a hard template was successfully employed as a novel electrocatalyst for the selective conversion of CO2 to HCOO–. The as-synthesized catalyst was capable of reducing CO2 to HCOO– with high efficiency and current density at low overpotentials and demonstrated a maximum Faradaic efficiency of 75% and a large current density of 10.8 mA cm–2 at an applied potential of −1.15 V. The results presented herein also demonstrated the high stability of the m-SnO2 electrode toward CO2RR, displaying a stable current density and Faradaic efficiency with no observable decay over 16 h of operation. The improved catalytic activity of the m-SnO2 electrode was ascribed to (i) preferential exposure of crystalline facets that provides sufficient active sites for CO2RR, (ii) significant presence of oxygen vacancy defects, and (iii) enhancement of CO2RR reaction kinetics due to reduced impedance and greater transport of reactants and facile dissipation of products through the large mesopores and well-dispersed catalyst.


Because we have been disinterested in their fate, future generations will need to clean up our carbon dioxide mess, and will need to do so with diminished resources, basically the trash we leave them.

In this regard, this is an interesting paper, since things like this may give them something to work with.

Have a nice evening.



Platinum Group Metal Extraction With Thermomorphic Ionic Liquids.

Many elements in the periodic table are subject to depletion from ores in near term; others in the long term.

Those subject in the short term include the "platinum group metals" - often referred to in the scientific literature as "PGM."

These are the elements, ruthenium (Ru), rhodium (Rh), palladium (Pd), osmium (Os), iridium (Ir) and platinum (Pt).

The first three elements are common fission products that can be isolated from used nuclear fuels. Two of them, ruthenium and rhodium can be obtained in a non-radioactive form with a few decades of cooling; pure non-radioactive (but monoisotopic) Pd can be obtained from the decay of ruthenium-106, which has a half life a few days longer than a year.

Palladium that is isolated as a fission product will remain slightly radioactive for millions of years, owing to the long lived isotope Pd-107. From my perspective this does not mean it is not useful; it can be used as a catalyst (one of the big uses for palladium) in closed systems, and off line I've been considering it as a component of superalloys that would prove superior (higher melting) to the nickel based superalloys which plays a key role in many technologies, notably power generation. The longer the half-life of an isotope, the lower its specific activity; which is why bananas, radioactive because of the potassium they contain, don't kill you. K-40 has a half-life of billions of years.

In the next few years, rhodium will become more available from used nuclear fuels than it is from domestic ores.

It is thus with interest that I came across a paper in the literature today that mentions the extraction of these valuable elements from used nuclear fuels, this one: Significant Acceleration of PGMs Extraction with UCST-Type Thermomorphic Ionic Liquid at Elevated Temperature (Arai et al, ACS Sustainable Chem. Eng., 2018, 6 (2), pp 1555–1559.

The authors describe an "ionic liquid" that is useful for the extraction of the light PGM from used nuclear fuel, where they are considered problematic because they interfere with the bad idea of throwing the stuff in used nuclear fuel away, that is dumping it. (This is a bad idea because all of the components of used nuclear fuel are potentially very useful materials to have. We need more of the stuff, not less, even if as a culture we're generally too stupid to figure that out.)

Here's what they say in their introduction which I've just echoed above:

Ionic liquids (ILs) are commonly defined as organic salts which melt below 100 °C. They have unique properties, e.g., nonflammability, nonvolatility, high conductivity, and diversity of combinations of cations and anions. Specifically, it is possible to synthesize an IL with potential to extract metal ions (Mn+) due to introducing functional groups on either its cationic or anionic components. Because of these properties, the use of ILs as an extraction solvent for Mn+ has been frequently investigated.(1-8) The above characteristics make these extraction systems more environmentally friendly compared with the ordinary organic/aqueous biphasic systems. One of expected applications is treatment of radioactive wastes.(9) For example, platinum group metals (PGMs) like Ru, Rh, and Pd in the high-level liquid wastes are sometimes problematic in the vitrification process.(10, 11) Hence, removal of these PGMs is significantly required. In this context, we are investigating the potential of ILs in the PGMs extraction. A few ILs undergo a temperature-responsive behavior, which shows transition of miscibility of IL with an aqueous solution at a critical temperature.(12-17) Specifically, an IL consisting of N,N,N-trimethylglycinium (or betainium, [Hbet]+) and bis(trifluoromethylsulfonyl)amide ([Tf2N]− ) is hydrophobic enough to form an organic phase immiscible with water at room temperature, whereas these layers are completely miscible with each other above 55 °C, namely, the upper-critical solution temperature (UCST).(18-24) Therefore, [Hbet][Tf2N] (Figure 1(a)) is highly promising for an energy-saving extraction process because ultimately homogeneous mixing of the aqueous/IL biphasic system is facilitated only by heating.


Whenever I look at a new chemical these days, I try to reflect on its environmental fate based on my general knowledge of biochemistry and toxicology. This is why I'm horrified at the latest trend in "green" solar technology, the perovskites, because these are compounds of the toxic element lead, which is even worse than the use of the toxic element cadmium used in commercial solar cells being distributed today with complete disregard for all future generations and too much regard for fads.

Things with a shorter half-life in the environment are obviously better than those with longer half-lives. The best case is compounds that occur naturally.

As it happens, you contain ionic liquids and would die without them. This is choline, which is trimethylammonium ethanol amine chloride (or hydroxide), the cation being an peralkylated and reduced form of the amino acid glycine (albeit not biochemically synthesized from glycine, but rather from serine or methionine.)

Anyway...

Since used nuclear fuels have a very high energy to mass ratio, one should - with a little chemical sophistication - require trivial amounts of materials to process them, but this said, this has historically not been true, as we have learned from the interesting case of the Hanford tanks from the former weapons plutonium isolation plant in Washington State. (The interesting chemistry of these tanks is fascinating, by the way, but that's a topic for another day.)

Here is the structure of the ionic liquids that may prove useful for the extraction of PGM from used nuclear fuels:



The ion on the top left is betaine, a common constituent of plants that helps plant cells balance their osmotic pressure. The ion on the top right is dehydroxycholine; I'm not aware of its presence or lack of presence in living cells, but I image it's going to be metabolized much like either choline or betaine.

The ion on the bottom of both species is however, is bistrifluromethylsulfonyl imide. This is a derivative of triflate, a common reagent utilized as a protecting group in organic synthesis. Triflate is the salt of trifluorosulfonic acid, one of the more powerful acids in the world and regrettably, an acid that is extremely stable. It is therefore environmentally suspect, since it is likely to persist for a long time, rather like the problematic PFOS side product of the Teflon industry and the fabric protection industry, widely distributed, long lived and rather suspect as a potential carcinogen.

I would suspect that triflate might be subject to some radiological degradation, but a lot of radiation in the presence of lots of water would be required, which is why the stuff is good for processing nuclear fuels, but potentially problematic unless completely recovered and recycled.

Anyway, this ionic liquid is very good at the removal of PGMs not only from nuclear fuels, but from other materials from which they may need recovery, at least when they are heated in low concentrations of nitric acid. (PGM are very, very, very, very useful elements.)

A graphic from the paper:



The caption:

Figure 5. Dependence of the extraction efficiency (E%) of Mn+ on [HNO3] in HNO3(aq)–[Hbet][Tf2N] systems.


They may also be useful for partial separations from one another, given their differening distribution constants:



The caption:

Figure 6. Distribution ratio (D) of Ru(III), Rh(III), and Pd(II) as functions of (a) [[Hbet]+] in 0.3 M HNO3(aq)/[TMPA][Tf2N] and (b) [H+] in (H,Na)NO3(aq)/[Hbet][Tf2N] (total [NO3–]: 3.00 M). Initial condition: [Ru(III)] = 7 mM, [Rh(III)] = 3 mM, [Pd(II)] = 5 mM, T = 353 K.


The authors conclude thusly:

To answer what drives the extraction of inert PGMs from HNO3(aq) to the thermomorphic [Hbet][Tf2N] ionic liquid, we studied the distribution behavior of Ru(III) and Rh(III) at different temperatures as well as that of Pd(II), the labile PGM. As a result, the kinetics of the extraction reactions of the inert PGMs were successfully improved at elevated temperatures. Their interaction with [Hbet]+ to form extractable species is the rate-determining step, which has been successfully accelerated by convection heating. Thus, the extraction of these inert PGMs seems to be simply temperature controlled regardless of the heating methods like convection and microwave. The extraction mechanism of Ru(III), Rh(III), and Pd(II) in the current extraction system is concluded to follow the formation of the PGM:bet complexes to release H+ to the aqueous phase. Further detailed investigations are currently ongoing, for instance, separation from other Mn+, preparation and characterization of the extractable PGM:bet complexes, and stripping behavior of the extracted PGMs from [Hbet][Tf2N]. We wonder that the back-extraction kinetics would also be affected by the temperature.


The subtext of this is that despite public fear and ignorance, there are still some people intelligent enough to be figuring out what to do with used nuclear fuels. This can only be good for a future that may prove inhabited by wiser people than we have proved to be.

Have a nice day tomorrow.




Emily Carter Predicts Low Temperature Photodissociation of Nitrogen Gas Bonds.

Although nitrogen comprises about 78% of the planetary atmosphere, living things cannot utilize it in its native state, and until the early 20th century, all of the bioavailable nitrogen depended on nitrogen fixing bacteria, often (on land) in symbiotic association with legumes. The enzymes responsible are probably iron based biocatalysts. (cf. PNAS 2006 November, 103 (46) 17107-17112 (A thermophilic nitrogen fixing bacteria is also known (cf Science 15 Dec 2006:Vol. 314, Issue 5806, pp. 1783-1786 - it or a similar organism may have played a role in the evolution of life on earth.)

In its diatomic elemental form nitrogen is extremely non-reactive. In fact, many chemical reactions in the lab are conducted under pure nitrogen gas (or semi-pure nitrogen in which the other constituent is argon) because the gas is considered inert, a kind of honorary noble gas.

One of the most important industrial chemical reactions on which our food supply depends is the Haber-Bosch process for breaking the triple bond in N2 gas, which liberated humanity from dependence on legumes for nitrogen fixation. (There is no physical way world population today could subsist on biologically fixed nitrogen; without industrially fixed nitrogen easily more than half the people now living would need to starve to death.)

The energy for this reaction comes from the use of dangerous natural gas (reformed with water to give hydrogen gas). According to the USGS the world produced 140 million metric tons of ammonia in 2016. The thermodynamic limit for this reaction is on the order of 20.9 GJ/ton, as of 2000, according to Smil's famous book on the topic, the industrial process's energy requirement had been reduced from 100 GJ/ton (dangerous coal based) in 1920 to 26 GJ/ton by the year 2000 (dangerous natural gas based.) (Smil, Enriching the Earth, MIT Press, 2001, Appendix K, Page 244.) It is difficult to imagine that an industrial process operating in 2000 at 80% thermodynamic efficiency has improved by all that much, but even it were operating at 100% efficiency, it would still represent a significant amount of energy. At 26 GJ/ton the demand to make 140 million tons of ammonia would be around 3.6 exajoules.

For comparison sake, all the world's solar and wind plants combined, the subject of so much delusional cheering, according to the 2017 World Energy Outlook, table 2.2, page 79 produced 9.4 exajoules of energy (out of 576 exajoules overall.)

However, much of the energy associated with ammonia production involves both heat and pressure to overcome the thermodynamic barrier of breaking the nitrogen-nitrogen triple bond in nitrogen gas. This bond is one of the strongest chemical bonds known, having a strength of 941 kJ/mol, (225 kcal/mol). (cf: Chirik et al, Nature Chemistry volume 2, pages 30–35 (2010))

Thus it was with interest that I came across a note in my email referring to recent calculations by the Dean of Engineering at Princeton University, Emily Carter, and one of her students that show that it is possible, based on computational chemistry determinations to photochemically lower the activation energy for the dissociation of nitrogen-nitrogen bonds:

New process could slash energy demands of fertilizer, nitrogen-based chemicals.

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Dr. Carter is one of the foremost computational chemists in the world, a leader in the development of what is known as "orbital-free density functional theory," a method of calculations to direct the discovery of new materials, catalysts and other molecules. While this sort of thing is somewhat esoteric, it is nonetheless extremely important to science and technology, and thus to modern human life.

It is difficult to predict how world changing scientific discoveries will prove to be; many seem to be earth shattering, but afterwards encounter difficulties that prove industrially insurmountable or simply get lost for a lack of funding by people who hate science, like, say, um Trump, Ryan and their league of exceedingly stupid people.

Nonetheless this discovery predicting a gold nanoparticle based catalysis could prove to be very important. (Perhaps scientists in less declining countries than the United States could take it up.)

Dr. Carter's scientific paper is open sourced and is here: Prediction of a low-temperature N2 dissociation catalyst exploiting near-IR–to–visible light nanoplasmonics (Martirez and Carter, Sci. Adv. 2017;3: eaao4710 22 December 2017)

Have a pleasant Sunday.








Little Wing.

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