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I was referring to a correction paper in the recent issue of Chemical Reviews and following it around lazily, I came across this interesting and inspiring site for women scientists working at UC Berkeley.


What I found particularly interesting is some examples of women who entered the university in non-science majors, and stumbled into science after taking a math class or something of that nature.

For example, here is the graduate student Rachel Woods-Robinson who is a third year graduate student in Applied Physics at UC Berkeley who entered ULCA as a college freshman hoping to major in playing the trombone.

Recently I had a conversation with a young woman who complained that during interviews for her admission to graduate school, people kept telling her that she was a strong candidate because she is a woman of color. She didn't think it was right, felt that she was privileged. (I happen to know that she was also privileged by coming from a wealthy family, but I didn't go there.)

(She shares ethnicity with 50% of our fabulous VP nominee.)

Being an old man - an old white man with a white wife and two white sons - I told her that we all have opportunities based on our backgrounds: My sons for instance got to go to better schools than my wife did - she went to an inner city school - and that was an "unfair" advantage for them.

We in this country are working to smooth out the obstacles before each of us, and if it was a little more difficult for my son to get into an engineering program than it was for some women of color because they are women of color, well, that evens things, doesn't it?

It is not why we have opportunities, I said, but what we do with them when we get them.

Anyway, it strikes me as wonderful that these young STEM students are celebrating being women STEM scientists.

We need more of this, not less of it.

In honor of our wonderful VP candidate...Let's do Frank...

I can hand carry my absentee ballot to the Board of Elections and Circumvent Trump's Destruction...

...of the Post Office.

Concerned about the politicization of even the US Post Office, I emailed my commissioners. Here is the exchange:

Dear Mr. XXXXXX:

You are entitled to deliver your Mail-In Ballot to the Board's Office and you may utilize any secure drop box located throughout the County. The list of drop boxes to place the ballot in will be updated prior to the November Election. Please note that if you and your family elect to hand deliver Mail-In Ballots to the Board, the ballot must be completed prior to arriving at the window. The Staff will have a form to complete to confirm your delivery.

Anthony R. Francioso
Mercer County Board of Elections

From: XXXX <XXXX@gmail.com>
Sent: Saturday, August 8, 2020 12:37 PM
To: boardofelections mercercounty.org <boardofelections@mercercounty.org>; Corrigan, Mary <mcorrigan@mercercounty.org>; Francioso, Anthony <afrancioso@mercercounty.org>
Subject: Questions connected with absentee ballots.

Dear Commissioners:

It has become clear that the US Post Office is under attack in connection with the election, and efforts are being made to politicize it by the officials in the current federal government.

In connection with my personal responsibility to help our democracy survive, I want to be sure my vote will be counted and not trashed or deliberately "lost."

As such, can I and my family request an absentee ballot and hand deliver the filled out ballots directly to the board of elections?

Thanks in advance for your answer.

Best regards,

Such and Such Road.

Some town somewhere, NJ ZZZZZ

This is what I'm going to advise all four Biden voters in my family to do.

Liquid/Liquid Extraction Kinetics for the separation of Americium and Europium.

The paper I'll discuss in this post is this one: Liquid/Liquid Extraction Kinetics of Eu(III) and Am(III) by Extractants Designed for the Industrial Reprocessing of Nuclear Wastes (T. H. Vu, Jean-Pierre Simonin*, A. L. Rollet, R. J. M. Egberink, W. Verboomm AE Enschede,
M. C. Gullo, and A. Casnati, Ind. Eng. Chem. Res. 2020, 59, 30, 13477–13490.)

I have come to consider americium as a critical nuclear fuel if we are ever to get serious about addressing climate change, something about which clearly are not at all serious.

(Solar cells and wind turbines haven't cut it, aren't cutting it and won't cut it. The reason is physics, the extraordinary low energy to mass ratio of these systems which leads to them being purely and totally unsustainable, and in fact, environmentally odious.)

The advantages of americium nuclear fuel include these:

1) The melting point of the metal, while not as low as that of plutonium, is sufficiently low to be accessible for containment for long periods of time. The metal also has a very high liquid range, comparable to that of neptunium and gallium.

2) The critical mass in the fast neutron spectrum (which I regards as a superior spectrum) is much higher than it is for plutonium for the two most common isotopes, Am-241 and Am-243. I discussed these critical masses in this space here: Critical Masses of the Three Accessible Americium Isotopes. The continuous recycling of plutonium will lead to rising critical masses because of the increases in the proportion of Am-243 with respect to Am-241.

3) Over a long period of operation Americium will produce two valuable plutonium isotopes that are critical for denaturing weapons grade plutonium, Pu-238 and Pu-242.

4) Considerable inventories of Americium exist and are readily available owing to the environmentally disastrous fear and ignorance that have prevented the prompt recycling of nuclear fuels.

5) The accumulation of Curium-242, Curium-244, and Plutonium-238 in americium based fuels, besides generating heat, will also generate supplies of the important industrial gas helium, a gas which is rapidly being depleted from mined sources.

6) Over the long term, the decay of Pu-238 will produce important supplies of U-234, which will eliminate, largely, the need for isotopic enrichment of uranium (particularly when conducted in concert with the use of thorium based U-233.)

Besides these advantages, it is possible, but not known to my knowledge, that liquid americium metal will prove to be less corrosive than liquid plutonium. That would simplify things a bit, although in my opinion, the corrosive nature of plutonium is a surmountable problem.

The evolution of an americium based liquid metal fuel over a period of decades will result in an Americium-Plutonium-Uranium alloy. Here is a (computationally derived) ternary phase diagram of this alloy showing liquidus curves:

The caption:

Fig. 7. Predicted liquidus projection of the U-Pu-Am system. Along the dashed curve the liquid alloy decomposes to the U-rich and Am-rich b.c.c, phases..

Source: Ogawa, Journal of Alloys and Compounds, 194 (1993) pp. 1-7.

As the fuel evolves, the melting point decreases, and with it, the expectation of sufficiently liquid fuels to allow for in line fuel processing, with the caveat being the effect of fission products.

Europium is a fission product, a relatively minor fission product, but a fission product all the same. It is always to be expected to be present in used nuclear fuels, both from the capture of neutrons in samarium isotopes as well as a direct fission product. Overall, one would expect, qualitatively for europium to relatively depleted because the two natural isotopes Eu-151 and Eu-153, high neutron capture cross sections, at least in the thermal spectrum, as do the two fairly long lived radioactive isotopes and their nuclear isomers, Eu-152 and Eu-154, with half-lives respectively for their low energy isomers, of 13.5 and 8.6 years. Although small quantities of these isotopes probably represent burnable poisons, and may have some utility as such, it may be, and most likely is desirable to remove europium from americium.

This brings me to the paper under discussion. Liquid/liquid extraction (often abbreviated "LLE" ) has been the most common approach to reprocessing used nuclear fuels. I don't necessarily endorse these as being likely to be the best approach, but nobody cares what I think anyway. Almost always, these extractions require agitation and worse, the use of solvents obtained from dangerous fossil fuels. It has occurred to me in recent years, particularly in light of the development of low temperature ionic liquids, that there may be other ways to exploit mass transfer across liquid interfaces, and thus this paper is of potential interest for me as I develop my generally useless thinking.

From the introductory text of the paper:

The reprocessing of nuclear wastes resulting from spent nuclear fuel is a worldwide topic of utmost importance in the nuclear industry and for the society itself. Various processes, generally based on liquid/liquid (L/L) extraction stages, have been proposed with the aim of reducing the volume, heat, and radiotoxicity of highly radioactive waste (plutonium and americium in particular) for their disposal in a geologic repository.(1) These processes involve the separation of the most problematic radioactive elements in the wastes.

Various strategies have been developed worldwide for the reprocessing of used fuel. An overview of the main solvent extraction processes(2) (besides Europe) is presented in Table 1. References are indicated in the table that give more details on the policies of the countries in this domain.

Table 1:

The text continues:

In Europe, this topic has been tackled with determination through the financing of successive European EURATOM projects since the early 90’s: NEWPART, PARTNEW, EUROPART, ACSEPT, SACSESS,(7) and now GENIORS (GEN IV Integrated Oxide fuels Recycling Strategies).(8) The European approach was centered around the use of selective extractants and molecular diluents that would generate a minimal amount of secondary waste. A feature of this strategy is the use of chemicals that only comprise the C, H, O, and N atoms (often referred to as the CHON principle(9)), which makes them suitable for subsequent incineration.
Reference aqueous separation process routes have emerged from these in-depth studies. They are depicted in Figure 1.(10,11)

Figure 1:

The caption:

Figure 1. Main routes of the European partitioning process strategy envisaged for the recycling of actinides (An) from used fuel (Ln = lanthanides). EXAM = extraction of americium.

Some descriptive text:

One route uses the GANEX (Grouped Actinide EXtraction) process(12,13) in which uranium is separated from the waste in a first step, and then, transuranic actinide elements are isolated (Np, Pu, Am, and Cm) from all fission products.
In the other route, the PUREX (plutonium, uranium, reduction, and extraction) process,(14) first implemented in the Manhattan project, is employed for the separation of uranium and plutonium from other fission products by using tributyl phosphate (TBP) as the extractant. The COEX process is a modified version of PUREX. Then, the DIAMEX (DIAMide EXtraction) process developed at CEA (Commissariat à l’Energie Atomique) in France may be used. It consists of the co-extraction of trivalent minor actinides [MA’s, mainly composed of americium(III) and curium(III)] and lanthanides (Ln’s) from a PUREX raffinate by employing a malondiamide extractant. Although they constitute less than 0.1% of the initial spent fuel mass, the MA’s (especially neptunium, americium, and curium) will be the main contributors to the radiotoxicity (and heat generation) after a three-century storage of high-level radioactive liquid waste (obtained after the PUREX stage).

The authors here are referring to the "storage" of so called "nuclear waste." By contrast, I speak of the recovery of nuclear resources. They are also speaking of "once through" thermal fuel, largely, and not continuously recycled actinides.

These caveats aside - most of humanity has been trained to think in this way, of waste rather than resources and this is clearly a fatal way to think, fatal to the future.

In a continuous actinide recycling program, some calculations show that it is possible to obtain americium alone in concentrations of close to 1.5% (cf. Ref: Nuclear Reactor Physics, William E. Stacy, Wiley and Sons 2001. pg.234). In a world in which we we did not use any dangerous fossil fuels, where we let our rivers run free, where we did not convert our wilderness into industrial parks for wind turbines, destroy rain forests for biofuels, generate millions of tons of toxic electronic waste for solar cells, we would need, in order to produce 600 exajoules of energy per year that we use as of recent times, we would require the fission of about 7,500 tons of plutonium (or other actinides) per year. This implies about 100 MT of americium would be available per year, a significant quantity of potential industrial importance. There may not be a lot of americium, but for the reasons given above, it may prove a useful fuel.

The authors use a device known as "rotating membrane cell" which is pictured here:

The caption:

Figure 2. RMC technique. Left: View of the cell with the membrane glued at the bottom. Center: Cell rotating in the outer phase. Right: Sketch of the technique.

The technique is closely related to solvent extraction techniques used in the industry, with several extractants in a commercially available mixture of dodecane isomers known as "TPH" containing a small amount of n-octanol, whereupon the solvent is known as "TPH-O." The extractants utilized in these solutions are shown in the following figure:

The caption:

Figure 3. Chemical structures of the molecules used in this study (SO3-Ph-BTP in tetravalent ionic form, counterion: Na+).

The membranes employed are commercially available, one being a hydrophilic membrane, the other hydrophobic:

Two types of membranes were purchased from Merck Millipore: the hydrophilic Omnipore PTFE membrane (JHWP04700, manufacturer’s data: pore size 0.45 μm, porosity of 80%) was employed to contain aqueous solutions, and the hydrophobic Durapore PVDF membrane (HVHP04700, manufacturer’s data: pore size 0.45 μm, porosity of 75%) was employed for organic solutions. The porosity values were also measured by impregnating membranes (glued on a plastic cylinder) with TPH and by measuring the corresponding mass of diluent. The membrane thicknesses, L, were measured by using a digital micrometer.

There is considerable discussion in the paper of the technique, and there is not time to describe all of it in detail. However the separation efficiency and speed are significant.

The last figure in the paper shows distribution coefficients for one system evaluated:

The caption:

Figure 7. Aq/org distribution ratios (1/K, left scale), and separation factor [SF(Am/Eu), right scale], of Eu(III) and Am(III) for an organic 0.2 M TODGA solution in TPH-O and an aqueous 0.5 M HNO3 solution as a function of SO3-Ph-BTP concentration in the aqueous phase up to 40 mM. ( ● ) = Eu(III); ( ○ ) = Am(III).

The authors conclude, noting that the purpose of their work is to provide input for further modeling and development of new systems.

...Extraction and stripping of Eu(III) and Am(III) were studied for various concentrations of nitric acid and TODGA, in mixtures of CyMe4-BTBP with TODGA, and in the presence of the aqueous ligands SO3-Ph-BTP and PTD. It was somewhat striking to find that TODGA is not surface-active at the interface between nitric acid and TPH-O, which is in contrast with the case of TODGA in n-dodecane.

The kinetic data obtained in this work will be used as input parameters in simulation codes (such as, e.g., PAREX, developed at CEA(64,65)) for a modeling of separation processes carried out in extractors (e.g., centrifugal) that operate with a short contact time between the phases.

The experimental results, obtained with TODGA and the two aqueous stripping ligands, show that faster transfer kinetics are associated with higher partitioning for Am(III) over Eu(III). This favorable outcome bodes well for future efficient actinide/lanthanide separation in the nuclear reprocessing industry.

My personal feeling is that we need to move beyond nitric acid dissolution of used nuclear fuel, which is a feature of the chemistry herein.

I believe the cleaner option for future nuclear fuel reprocessing is to conduct some of it in line using techniques including but not limited to distillation. There are also possibilities, some of which were briefly explored in the 1950's, to utilize liquid/liquid extractions in line using inorganic liquids.

However, it may be that liquid/liquid interfaces may be important at some point in future techniques. We need to take a deeper look at molten salt based separations, included but not limited to organic ionic liquids. Much attention is being paid to these substances. Finally a driving force for both separations and dissolution may not need to involve mechanical forces. Electrochemical techniques, including those involving liquid membranes are worthy of consideration.

There are really a wealth of options for the treatment of nuclear fuels and the recovery and use of the radioactive and non-radioactive materials therein. These materials are probably, in my view, the best shot we have to save the world.

I hope your weekend was pleasant as much as it was safe.

Susan Collins.

The Genome of the Last Surviving Member of an Order from which Dinosaurs, Birds, Mammals...

...and modern reptiles evolved has been sequenced.

The paper to which I'll refer is this one: The tuatara genome reveals ancient features of amniote evolution (Gemmel et al., Nature, https://doi.org/10.1038/s41586-020-2561-9).

An amniote is an animal whose embryonic development takes place in an amiotic fluid surrounded by a membrane called a chorion. This class of animals includes all reptiles, birds, and mammals.

The paper is open sourced, anyone can read it. It describes the last member of a class of animals which once dominated the Earth before branching out to evolve as dinosaurs, birds, modern reptiles, and mammals including that somewhat destructive animal the human being.

An excerpt from the abstract:

The tuatara (Sphenodon punctatus)—the only living member of the reptilian order Rhynchocephalia (Sphenodontia), once widespread across Gondwana1,2—is an iconic species that is endemic to New Zealand2,3. A key link to the now-extinct stem reptiles (from which dinosaurs, modern reptiles, birds and mammals evolved), the tuatara provides key insights into the ancestral amniotes2,4. Here we analyse the genome of the tuatara, which—at approximately 5 Gb—is among the largest of the vertebrate genomes yet assembled. Our analyses of this genome, along with comparisons with other vertebrate genomes, reinforce the uniqueness of the tuatara. Phylogenetic analyses indicate that the tuatara lineage diverged from that of snakes and lizards around 250 million years ago.

From the introduction:

The tuatara (Sphenodon punctatus)—the only living member of the reptilian order Rhynchocephalia (Sphenodontia), once widespread across Gondwana1,2—is an iconic species that is endemic to New Zealand2,3. A key link to the now-extinct stem reptiles (from which dinosaurs, modern reptiles, birds and mammals evolved), the tuatara provides key insights into the ancestral amniotes2,4. Here we analyse the genome of the tuatara, which—at approximately 5 Gb—is among the largest of the vertebrate genomes yet assembled. Our analyses of this genome, along with comparisons with other vertebrate genomes, reinforce the uniqueness of the tuatara. Phylogenetic analyses indicate that the tuatara lineage diverged from that of snakes and lizards around 250 million years ago.

It is also a species of importance in other contexts. First, the tuatara is a taonga (special treasure) for Māori, who hold that tuatara are the guardians of special places2. Second, the tuatara is internationally recognized as a critically important species that is vulnerable to extinction owing to habitat loss, predation, disease, global warming and other factors2. Third, the tuatara displays a variety of morphological and physiological innovations that have puzzled scientists since its first description2. These include a unique combination of features that are shared variously with lizards, turtles and birds, which left its taxonomic position in doubt for many decades2. This taxonomic conundrum has largely been addressed using molecular approaches4, but the timing of the split of the tuatara from the lineage that forms the modern squamates (lizards and snakes), the rate of evolution of tuatara and the number of species of tuatara remain contentious2. Finally, there are aspects of tuatara biology that are unique within, or atypical of, reptiles. These include a unique form of temperature-dependent sex determination (which sees females produced below, and males above, 22 °C), extremely low basal metabolic rates and considerable longevity2.

A graphic from the paper:

The caption:

a, The tuatara, (S. punctatus) is the sole survivor of the order Rhynchocephalia. b, c, The rhynchocephalians appear to have originated in the early Mesozoic period (about 250–240 million years ago (Ma)) and were common, speciose and globally distributed for much of that era. The geographical range of the rhynchocephalians progressively contracted after the Early Jurassic epoch (about 200–175 Ma); the most recent fossil record outside of New Zealand is from Argentina in the Late Cretaceous epoch (about 70 Ma). c, The last bastions of the rhynchocephalians are 32 islands off the coast of New Zealand, which have recently been augmented by the establishment of about 10 new island or mainland sanctuary populations using translocations. The current global population is estimated to be around 100,000 individuals. Rhynchocephalian and tuatara fossil localities are redrawn and adapted from ref. 1 with permission, and incorporate data from ref. 2. In the global distribution map (c, top); triangle = Triassic; square = Jurassic; circle = Cretaceous; and diamond = Palaeocene. In the map of the New Zealand distribution (c, bottom); asterisk = Miocene; cross = Pleistocene; circle = Holocene; blue triangle = extant population; and orange triangle = population investigated in this study. Scale bar, 200 km. Photograph credit, F. Lanting.

It's well worth a look, and again, open sourced. It's well worth a look.

If interested, enjoy...

I wish you a safe, healthy and pleasant weekend.

Our power is on again.

Everything is right with the world.

For Father's day, my family bought me the video documentary Juice: How Electricity Explains the World, which is about life without electricity in Puerto Rico - for years after the Trumpers abandoned these Americans - and, sadly, Lebanon - Africa and elsewhere. I had the electricity to watch it.

It was pretty well done overall.

Of course I knew all about this, life without electricity, after Hurricane Sandy (during which I was pretty badly injured), but the reminder connected with the tropical storm this week in New Jersey was, um, um, for lack of a better term for it, "a useful reminder."

Like Taj Mahal used to sing, "You don't miss your water, until your well runs dry."

This Immigrant Who Trump Clearly Hates, Built an Innovative Scientific Tool Company in the US.

Every day I get pop up ads in various places for scientific instruments, whether at work or at home. I usually can learn something from them, but it is not possible to open them all.

Today's ad came from a company developing innovative devices that would have been much appreciated in an earlier part of my career; regrettably I have no need for rotary evaporators, although I have a certain nostalgia for the days when they were part of my daily life.

An immigrant to this country, from Ghana, has founded a company built around an improved rotary evaporator device.

George Adjabeng

About Our Founder

Born in Somanya, Ghana, George Adjabeng attended the University of Cape Coast in nearby Ghana for his undergraduate studies. Graduating in 2000, he received the Mendell Award for overall top chemistry student. In the fall of 2000, he moved to Brock University (St. Catharines, Canada) where he began his masters’ research with Professor Alfredo Capretta studying new and robust methodologies for palladium-catalyzed, cross-coupling reactions. There, he co-authored five internationally acclaimed articles. He left Brock in the fall of 2003 to pursue a medicinal chemistry career with Roche (Palo Alto, California). At Roche, his research was focused on infectious diseases where he co-authored two papers. In 2004, George left Roche to join GSK (Research Triangle Park, North Carolina) to pursue cancer drug research. He was awarded the Exceptional Science Award twice for making significant contributions to the discovery of new drugs. He was a discoverer and first inventor of the advanced melanoma drug, Tafinlar. His contributions on many more projects lead to the discovery of drugs, publications and many patents. In his research into infectious diseases, he independently invented a scaffold upon which a Hepatitis C Virus pan-genotype inhibitor drug was discovered. He left GSK in 2011 as a Senior Scientist and briefly held research positions at the National Institute of Health (NIH, Rockville, MD) and UNC Eshelman School of Pharmacy (Chapel Hill, NC) before venturing into entrepreneurship...

...During his MBA studies his entrepreneurial spirit was awakened and after graduating in 2010, he filed his first sole inventor patent titled Rotary Evaporator. Prior to this invention, George used rotary evaporators extensively in research for over a decade. George developed his first prototype in 2013, followed by the second prototype in 2014 and the customer-ready product the EcoChyll® in 2015. Today, he leads Ecodyst through its formative years in instrument design, engineering, manufacturing, finance, marketing, sales and customer relations.

Now you would need to have a shithole brain and an extremely primitive understanding of the world, a lousy education, and the moral level of a decomposed turnip to not appreciate Mr. Adjabeng.

Mr. Adjabeng has much of which to be proud, of course, of what he brought to his adopted country - may we be worthy of him - and it goes significantly beyond being such an idiot as to be proud of reciting "Person, Man, Woman, Camera, TV..."

The company: Ecodyst: Leading High Speed Solvent Recovery.

It is going to take a long time, a long time, before our country can erase the stain of Trumpist racism from our history.

Efficient, Reversible, and Selective Absorption of SO2 in an Emim-Cl Ionic Liquid Deep Eutectic.

The paper I'll discuss in this post is this one: Highly Efficient, Reversible, and Selective Absorption of SO2 in 1-Ethyl-3-methylimidazolium Chloride Plus Imidazole Deep Eutectic Solvents (Zi-Liang Li, Lin-Sen Zhou, Yue-Han Wei, Hai-Long Peng, and Kuan Huang, Ind. Eng. Chem. Res. 2020, 59, 30, 13696–13705).

Sulfur dioxide is a major pollutant from the combustion of dangerous fossil fuels as well as, albeit to a lesser extent, the combustion of "renewable" biomass. My interest in this paper is not connected with putting lipstick on the dangerous fossil fuel pig, nor as an endorsement of so called "renewable energy" which has proved to be, at enormous expense, yet another form of lipstick on the dangerous fossil fuel pig.

My interest is connected rather with a particular version of a thermochemical water splitting cycle, specifically, the sulfur iodine cycle which generates separate streams of hydrogen and oxygen. My considerations of thermochemical cycles has in recent years focused on other cycles, specifically those utilizing transition metals or cerium, a multivalent lanthanide, but it has always been the case that the sulfur iodine cycle - and some closely related cycles - have the advantage of requiring only fluid phases. An issue in the sulfur iodine cycle is that the oxygen generated may be contaminated with sulfur dioxide, limiting its use in oxyfuel combustion, and also suffering from reversibility. (The oxyfuel combustion of biomass under closed conditions - no smokestack - is a fairly straight forward path to recovering carbon dioxide from the atmosphere, and much safer than current procedures which are responsible for about half of the six to seven million air pollution deaths per year.)

The recent developments in ionic liquid approaches have renewed my interest in this cycle - although others offer different advantages.

These cycles are accessible by the use of clean energy, of which there is only one real form, nuclear energy. Because these cycles take place at relatively high temperatures, they also afford the achievement of high energy efficiency with managed heat flows, coming under the general rubric of "process intensification."

Anyway, from the introduction to the paper - artifacts of the translation of thoughts in Chinese to English text notwithstanding:

Sulfur dioxide (SO2) is an air contaminant that can be found in the tail gas of thermal power plants, sulfuric acid factories, and steel mills. It constitutes the major precursor of acid rain and may cause serious harm to the global environment if directly emitted into the atmosphere.(1,2) Therefore, the contents of SO2 in industrial tail gas should be strictly controlled. On the other hand, SO2 is very useful as the extractant, food additive, and raw material for the production of sulfur-containing chemicals.(3) Therefore, it is of great significance to eliminate and recycle SO2 from industrial tail gas.(4) At present, the most widely adopted method to capture SO2 from industrial tail gas is wet scrubbing, which utilizes absorbents such as organic solvents,(5) seawater(6) limestone slurry,(7) and aqueous ammonia.(8) However, these absorbents are associated with many shortcomings. For example, traditional organic solvents are highly volatile and may cause secondary pollution to the environment; seawater is abundant only in coastal areas and of relatively low efficiency for SO2 absorption; limestone slurry and aqueous ammonia are irreversible for SO2 absorption, leading to the waste of sulfur resource.

Given these shortcomings, developing new absorbents with low volatility, high efficiency, and good reversibility is highly demanded. Since there are many other components (e.g., N2 and CO2) in industrial tail gas, the developed absorbents should also exhibit high selectivity. To this end, ionic liquids (ILs) were proposed as promising candidates.(9−11) ILs are a class of organic molten salts and credited as “green solvents” owing to their negligible volatility. In addition, the properties of ILs can be easily tuned by tailoring the structures of ILs.(12−16) It is expected that highly efficient, reversible, and selective absorption of SO2 can be achieved in ILs. Within this regard, many functionalized ILs with excellent performance for SO2 capture have been developed by utilizing the electron-deficient and Lewis acidic property of SO2 molecules.

The authors combine two developments garnering a great deal of attention, the ionic liquids mentioned the text, and "deep eutectic solvents."

From the text:

Recently, deep eutectic solvents (DESs) started to attract considerable attention in gas separation research because they share similar features with ILs in terms of low volatility and tunable properties.(30,31) DESs are simple mixtures of hydrogen-bond acceptors (HBAs) and hydrogen-bond donors (HBDs). They have lower melting points than individual components because the hydrogen-bond interaction formed between HBAs and HBDs changes the electron distribution of molecules.(32) In comparison with ILs, DESs can be more easily prepared from commercial reagents, thus making them more intriguing from a practical perspective. Therefore, DESs are regarded as more promising candidates to achieve highly efficient, reversible, and selective absorption of SO2.

The authors add the very simple ionic liquid, ethylmethylimidazolium chloride, most often designated "emim chloride" imidazole, to imidazole, the chemical precursor to emim cations.

The structure of the emim chloride and imidazole are given in this figure:

The caption:

Scheme 1. Chemical Structures of [Emim]Cl and Imidazole

A table in the paper gives literature references for a number of other deep eutectic solvents utilized for the capture SO2.

Of more immediate relevance is a table of the showing viscosities as a function of composition, along with the decomposition temperatures of the mixtures.

The viscosities at room temperature (298K) are roughly equivalent, for the most dilute IL in imidazole, to that of, say, corn oil, only slightly higher. The supplementary data of the table gives the viscosities as a function of temperature, and near the temperature of regeneration reported in the paper which was around 353 K, about 20 K lower than the boiling point of water, the viscosities are quite low, not quite as low as that of water, but approaching it more closely. Note that the desorption temperature is only around 40 K lower than the decomposition temperatures of the deep eutectic solvent mixtures with the lowest concentrations of the emim-Cl. A mixture of SO2 and O2 gas from the thermal decomposition of sulfuric acid would emerge at much higher temperatures, but there is certainly an impetus to rapidly cool this gas mixture - most wisely in a process intensification setting - to prevent the rapid reoxidation of SO2 to SO3, the latter being the anhydride of sulfuric acid.

In the paper's experimental section it is noted that the viscosity is determined using a Brookfield viscometer, which is a widely used but considerably less sophisticated instrument than those provided by, say, Anton Paar, or TA instruments, which measure the full viscosity curves over a wide range of shear rates, but it is, at least illustrative.

No Arrhenius plot of the decomposition reaction is given, nor is the reaction clearly described, despite the fact that the regeneration (desorption) temperature is relatively close to that of the decomposition paper, but the paper does describe the behavior over multiple cycles, suggesting a fairly good stability:

The caption:

Figure 3. Solubilities of SO2 in [emim]Cl+imidazole (1:0.5) for ten consecutive absorption–desorption cycles (absorption condition, 313.2 K and ∼100 kPa; desorption condition, 353.2 K and ∼0.1 kPa for 2 h).

The reported concentrations of SO2 are quite high, approximately 15 mol/kg, which translates to over 900 grams of SO2/kg.

This data is, however, for the most viscous deep eutectic and concentrated with respect to the ionic liquid. Perhaps there are reasonable trade offs, which also seem necessary with respect to the time of regeneration.

This system is designed for the exhaust of dangerous fossil fuels, and thus the selectivity with respect to carbon dioxide and nitrogen gas are described, and not oxygen, but it is notable that the absorption depends on the lewis acidity of SO2, a property not generally associated with oxygen gas. This breakthrough graph from the paper shows the selectivity with respect to nitrogen and carbon dioxide, neither of which would be present in a sulfur iodine cycle decomposition gas:

Figure 6. Breakthrough curves for the absorption of SO2/CO2/N2 mixed gas (0.02/0.15/0.87 vol) in [emim]Cl+imidazole (1:0.5) at 298.2 K.

In an industrial setting, fast analysis might prove possible using simple IR techniques.

The caption:

Figure 11. FTIR spectra of [emim]Cl+imidazole (1:0.5) before and after SO2 absorption (black line, before SO2 absorption; red line, after SO2 absorption).

This quite an interesting little paper, I think, cheap and easy to synthesize reagents, readily accessible temperatures in a process intensification setting, and other features. In any case there is a long distance between an industrial sulfur-iodine cycle and the present day, but it could make for an interesting future in clean energy, the only sustainable form of which is nuclear energy.

I trust you are having a safe weekend and are enjoying life as much as is possible in these tragic times.

For what change in yourself do you hope when President Biden takes office?

Mine: I want to feel less bitter, less angry, and free of wishing cruel things on people, irrespective of how evil they are.

I don't like many of the things I think; and never knew they were in me.
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