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NNadir

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Forensic Analysis of One of the Earliest Weapons Grade Plutonium Samples Ever Prepared.

Recently I've been studying - because some excellent articles on the topic have been showing up in the scientific journals I routinely scan and or read - the interesting chemistry of the clean up of one of the most radioactively contaminated sites in the world, the Hanford Reservation near Richland, Washington.

Here for instance, is one such paper on this topic, on which I may comment in the future in this space: Review of the Scientific Understanding of Radioactive Waste at the U.S. DOE Hanford Site (Peterson et al, Environ. Sci. Technol., 2018, 52 (2), pp 381–396)

I am always interested in radiochemistry, since I believe understanding it represents the last best hope of the human race.

Coincidentally, I've been going through old papers that I collected years ago but never read to sort them into appropriate directories, and I came across an interesting paper relating to one of the earliest known samples of plutonium ever prepared, prepared in the early days of the Manhattan project. The paper is here: Nuclear Archeology in a Bottle: Evidence of Pre-Trinity U.S. Weapons Activities from a Waste Burial Site (Schwantes et al., Anal. Chem., 2009, 81 (4), pp 1297–1306)

The Hanford site, which is where most of the plutonium for America's nuclear weapons was made, for most of its history as a production plant, operated on what its operators considered to be "emergency" conditions, extreme conditions of races against real and putative enemies, in both hot and cold war. The mentality was not focused at all on the long term other than potential post apocalyptic scenarios in which our enemies nuked us before we could nuke them. In such a mentality, so far as radioactive fission products as well as toxic chemicals were concerned, they were handled in a way that in our more distant time we would regard as extremely cavalier. In the earliest years, nuclear by products, often referred to as "nuclear waste," were often disposed of in open trenches, to be replaced later by single shell tanks, some of which famously leaked, and then in double shell tanks. Poor records and inventories were kept, but again, the remediation of this site has some fascinating chemistry and the clean up shows as much ingenuity as the creation of these materials did.

By the way, the existence of the Hanford Site has not lead to a death toll that even remotely approximates the number of people who have been killed by the by products of combustion of dangerous fossil fuels and biomass, which approximates about 7 million people a year, every year, which is roughly the equivalent of nuking and completely wiping out a city the size of Hong Kong every year, without stop. There are people, not very bright people, who wish to represent Hanford as the worst environmental problem that has ever existed, scientifically illiterate journalists for example. The 55,000 citizens of Richland, Washington are leading useful lives - many are scientists at Pacific Northwest National Laboratories - and are not dropping dead in the streets.

But no matter.

Anyway...Nuclear Forensics and the earliest plutonium samples:

From the opening text of the paper:

The frequency of smuggling events involving radioactive materials is supply driven and is on the rise world-wide.(1, 2) While special nuclear materials from the nuclear fuel cycle have not significantly contributed to this increasing trend to date, it is likely that with the current nuclear renaissance and greater access to these materials by the public, smuggling events involving fissionable materials may rise in the near future. Perhaps the most effective tool investigators have against this type of smuggling is the successful application of nuclear forensic science.(3) Nuclear forensics is defined as the science of identifying the source, point-of-origin, and/or routes of transit of nuclear and radiological materials associated with illegal activities for ultimately contributing to the prosecution of persons responsible for those activities.(4) In many respects, the goals of nuclear archeology are identical to those of nuclear forensics, without the added constraints specifically associated with legal prosecution. As such, studies of nuclear archeology serve as an excellent means for advancing the science and demonstrating the capabilities of the nuclear forensics community. Moreover, depending upon the pedigree of the artifacts studied, fully characterized finds representing specific end members of various processes or reactors may be of direct use to forensics experts for comparative purposes against real interdicted sample materials of unknown origin.(5-7) This work provides the public a rare glimpse at a real-world example of the science behind modern-day nuclear forensics and, in doing so, uncovers a sample of historical significance.

Background

The Hanford Site in Washington became the location for U.S. plutonium production during World War II. The Pu produced at this site was used in the first Pu nuclear weapon dropped on Nagasaki, Japan, on August 10, 1945, and in Trinity, the name given to the world’s first test of a nuclear weapon on July 16, 1945. In December 2004, a safe containing several hundred milligrams of extremely low burnup Pu (a term typically associated with Pu produced as part of a weapons program) in a one gallon glass jug was unearthed by Washington Closure Hanford (WCH) personnel while excavating the 618-2 burial ground in the 300-area of Department of Energy’s Hanford site.(8, 9) The jug contained ∼400 mL of slurry characterized as a white precipitate in a clear liquid. Pictures in Figure 1 document this find. In-field γ analysis conducted on the container detected the presence of only 239Pu. The minimum 239,240Pu/238Pu and 239Pu/241Am ratios were estimated to be at least 320:1, and 1000:1, respectively, based upon the detection limits of this analytical technique, indicating the Pu was produced from extremely low exposure fuel, consistent with early military reactor operations at Hanford. The absence of γ-emitting U or fission product isotopes in the spectra also suggested the Pu had been separated and purified prior to its disposal. Considering the potential historical significance of the find, WCH personnel coordinated with staff at Pacific Northwest National Laboratory (PNNL) to conduct further analysis of the sample. All of the liquid and ∼2% of the solid from the container were repackaged into two 1 L polypropylene bottles on May 10, 2006, with one of the two bottles being transferred to PNNL. The majority of the solid material remained, caked to the walls of the original glass jug and was earmarked for disposal. We have coined the process of characterizing this sample as nuclear archeology.


Here's a photograph of the safe and the bottle in it in which the plutonium was found:



The caption:

Figure 1. Pictures of (a) excavated safe and contents and (b) glass bottle containing several hundred milligrams of Pu.


Apparently the process utilized to isolate the plutonium used a lanthanum fluoride carrier. It must have been the case that there was very little plutonium available at the time of the isolation, which is not surprising. In 1944, a chemist named Don Mastick broke a test tube in such a way as to end up eating what was then the world supply of the element; and many years later, as an old man was interviewed on the subject before dying in 2007 at the age of 87.

The scheme for analyzing the contents of the bottle is shown in the following graphic, also from the paper:



One of the interesting things about this paper which surprised me - this after more than 3 decades of reading about nuclear science - was that there was enough Na-22, a radioactive isotope of sodium in the sample to use it as a kind of tracer of the history of the bottle. As it is a radioactive isotope that is neutron deficient, as opposed to neutron rich, it's not an isotope I ever bothered thinking much about. It arises from the interaction of fluorine, a monoisotopic element with a mass number of 19, with alpha particles:

GEA revealed the presence of the relatively short-lived 22Na isotope within the sample. The mechanism for the formation of 22Na (t1/2 = 2.6 years) within fluoride matrixes in the presence of α-emitting actinides has been well documented in the literature(18-23) following the reaction pathway of 19F(α,n)22Na. The production rate for this reaction is a function of the physical characteristics of the fluoride matrix, the production rate and energy of the α particles, and the proximity of the α particles to the 19F atoms. Equation 5 provides a mathematical model for the production of 22Na within simple actinide fluoride solids.




You learn something every day. This might be of interest to all those people working on MSRs (Molten Salt Reactors) utilizing the "FLIBE" or "FLINAK" salts. It's probably not a serious drawback, but one probably requiring some attention.

Some additional comment from the authors on the role of Na-22 in their analysis:

Isotopes like 22Na that are produced from secondary nuclear reactions involving radioactive material may be useful to investigators when a sample of unknown history containing such material is discovered. With the use of the Pu jug as an example, the 22Na activity becomes an easy to detect (γ energy, 1275 keV; branching ratio, 99.4%) signature for 239Pu under steady-state conditions (regions 2 and 4 of Figure 4). In addition, with the assistance of an accurate production model for 22Na, the total Pu within the sample prior to repackaging can be estimated prior to reaching steady-state conditions (i.e., within region 1) if it is known a priori when 22Na production began. Alternatively, the time since 22Na production began may be estimated during the in-growth period (region 1) if the amount of Pu within the sample (prior to repackaging) is known. However, it is region 3 of Figure 4 that is of most interest to the nuclear forensics community. Here the Pu jug after repackaging (2006) resembles what might be expected from an interdicted sample that, unknown to the investigator, had been separated from the majority of the Pu prior to confiscation. In such a case, a decrease in the 22Na activity with time would suggest the confiscated sample may have been portioned off from a greater amount of Pu that had escaped interdiction


Figure 4:



The caption:

Figure 4. Predicted and measured 22Na content with time within the Pu sample from 1945−2038.


Further elaboration is in the text of the original paper about how to use isotopes like 22Na (or similar secondary nuclear reactions) to determine whether the same contains all of the plutonium originally available from its source, or only a fraction of it.

By the way, the plutonium in this sample was almost pure Pu-239, a grade of plutonium that today would be considered an extreme weapons grade material. This is unsurprising, since the Manhattan project had no way of knowing the effect of plutonium-240 would have on their weapons, and probably went to great lengths to avoid its accumulation. This requirement, regrettably greatly increased the volume of waste in order to isolate it, and this remained an issue, even after it was understood that weapons grade plutonium could tolerate more Pu-240 than was realized. Weapons grade plutonium is still not at all like reactor grade plutonium.



The caption:

Figure 7. Comparison of measured Pu isotopic ratios from the sample (solid red squares) with predicted ratios within spent fuel from X-10 reactor at 3.6 and 3.7 MWd/MTU (solid and dashed blue lines, respectively) and B-reactor operations (dashed grey line) in the 1940s. The model line for the B-reactor represents ratios that would have been produced at the lowest recorded power level (17.2 MWd/MTU) for that reactor. The area above the B-reactor model line represents the possible range of isotopic ratios that could have been produced at power levels above the lowest recorded value. The value of the 242/239 ratio for the sample was found to be below the limit of detection (identified by the open red square) of the analytical technique used.


Using the ratio, the authors determined that the source of the plutonium was not Hanford's more famous B-reactor, but rather the X-reactor, which was not located at Hanford, but rather at Oak Ridge.

This is explicated in the full text.

Interesting stuff, I think.

I wish you a pleasant rest of the weekend.





Copernecium forms a mercury like amalgam with gold.

I'm going through old papers I collected 10 years ago but never read, and I came across this oldie but goodie from 2007, which somehow found its way into a directory about the environmental and climate impact of large dams, along with an obituary of John Wheeler:

Chemical characterization of element 112 (R. Eichler, N. V. Aksenov, A. V. Belozerov, G. A. Bozhikov, V. I. Chepigin, S. N. Dmitriev, R. Dressler, H. W. Gäggeler, V. A. Gorshkov, F. Haenssler, M. G. Itkis, A. Laube, V. Ya. Lebedev, O. N. Malyshev, Yu. Ts. Oganessian, O. V. Petrushkin, D. Piguet, P. Rasmussen, S. V. Shishkin, A. V. Shutov, A. I. Svirikhin, E. E. Tereshatov, G. K. Vostokin, M. Wegrzecki & A. V. Yeremin, Nature volume 447, pages 72–75 (03 May 2007))

One of the most dubious mining practices in the world is the extraction of gold from ores using liquid mercury, because mercury readily dissolves gold, which historically was the most problematic element to dissolve, at least until the discovery of a mixture of acids, hydrochloric and nitric acid, known as "aqua regia" because it dissolves "the king of metals." Aqua regia however is somewhat less effective when recovering gold from ores than mercury, and therefore mercury is still utilized for this purpose, particularly in wild cat mining of the type utilized to recover not only gold but many diffuse elements such as tantalum and the lanthanides, leading to distributed pollution that is difficult to address.

To recover gold from solution in liquid mercury, the mercury is distilled off.

Wonderful.

Anyway...

Element 112, now known as the element Copernicium, is a cogener of the toxic metals mercury and cadmium, the toxicity of which is largely an effect related to their displacing another cogener, zinc, in metalloenzymes, thus inactivating them.

The ten year old paper linked above refers to its chemistry, which has been the subject of some interest owing to relativistic corrections to its electronic structure, a topic to which the wonderful host of this group, directed my attention recently. It has not been clear whether or not Copernicium would be an inert gas rather like radon or a liquid. From the text:

The heaviest elements to have been chemically characterized are seaborgium1 (element 106), bohrium2 (element 107) and hassium3 (element 108). All three behave according to their respective positions in groups 6, 7 and 8 of the periodic table, which arranges elements according to their outermost electrons and hence their chemical properties. However, the chemical characterization results are not trivial: relativistic effects on the electronic structure of the heaviest elements can strongly influence chemical properties4–6. The next heavy element targeted for chemical characterization is element 112; its closed-shell electronic structure with a filled outer s orbital suggests that it may be particularly susceptible to strong deviations from the chemical property trends expected within group 12. Indeed, first experiments concluded that element 112 does not behave like its lighter homologue mercury7–9. However, the production and identification methods 10,11 used cast doubt on the validity of this result...

The systematic order of the periodic table places element 112 in group 12, which also includes zinc, cadmium and mercury. It should thus have the closed-shell electronic ground state configuration Rn: 5f 146d107s 2, which implies noble metal characteristics16. However, relativistic calculations of atomic properties of superheavy elements suggest4–6 contraction of the spherical s- and p1/2-electron orbitals. The effect may increase the chemical stability of the elemental atomic state of element 112 beyond that of a noble metal and endow it with inertness more similar to that of the noble gas radon17, although recent relativistic calculations on element 112 predicted18 that it should form a semiconductor-like solid with clear chemical bonds. It was suggested19 that the questions of the bonding characteristics of element 112 and whether it more strongly resembles a noble metal or a noble gas might be addressed experimentally, by determining its gas adsorption properties on a noble metal surface such as gold. In fact, relativistic calculations indicate that the spin-orbit splitting of the 6d orbitals results in element 112 having a ground-state configuration with a 6d5/2 outermost valence orbital, which would make it behave like a noble transition metal20,21. Moreover, relativistic density functional calculations of its interaction with noble metals predict metallic interactions similar to those of the lighter homologue mercury22–24...

... By directly comparing the adsorption characteristics of 283(Cn) to that of mercury and the noble gas radon, we find that element 112 is very volatile and, unlike radon, reveals a metallic interaction with the gold surface...


Some interesting details about this elegant experiment requiring significant teamwork:

Thermochromatography allows very efficient probing of the interaction potential of volatile gas-phase species with stationary surfaces over a broad range of interaction enthalpies.We used the in situ volatilization and on-line detection method28 for thermochromatography measurements at temperatures between135 uC and 2186 uC, with the original system modified and significantly improved11,29 to enable gas adsorption investigations of element 112 on gold surfaces. Figure 1 depicts schematically the experimental set-up. A target of 242PuO2 (1.4mg cm22 242Pu) with an admixture of nat.Nd2O3 (15 mg cm22 of Nd of natural isotopic composition) was deposited on a thin (0.7mg cm22) Ti backing foil and irradiated for about three weeks at the U-400 cyclotron at FLNR with 3.131018 48Ca particles at a primary energy of 27063MeV. The beam energy in themiddle of the target was 23663MeV, corresponding to the maximum of the production cross-section of 287Fl in the 242Pu(48Ca, 3n) reaction channel12. The irradiation generated not only 287Fl, but also the partially alphadecaying nuclide 185Hg with a half-life of 49 s. This nuclide is produced in the reaction 142Nd(48Ca, 5n) and serves in our experiment as a monitor for the production and separation process. Various isotopes of radon (for example, 219Rn, with a half-life of 4 s) were also produced in multi-nucleon transfer reactions between 48Ca and 242Pu. Thus, radon and mercury were studied simultaneously with element 112 throughout the experiment.


Cool, I think.

The conclusion:

The statistical Monte Carlo approach to modelling the gas chromatography results17,30 uses adsorption enthalpy values to mimic the observed deposition patterns, which provides upper and lower limits for the adsorption enthalpy of element 112 on gold2DHads Au(E112) of 98 kJ mol21 and 45 kJ mol21 (68% confidence interval), respectively; it also yields a most probable value of 2DHads Au(E112) 552 kJ mol21, which has a large associated uncertainty due to the small number of observed events (see also Supplementary Information section 2). Still, the range of likely adsorption enthalpies inferred from this study indicates an interaction between element 112 and gold that is significantly stronger than the purely dispersive van der Waals interactions of noble-gas like elements27. We therefore conclude that the stronger adsorption interaction of element 112 with gold involves formation of a metal bond, which is behaviour typical of group 12 elements.


The added bold is mine.


(Cn substituted for 112 and Fl for 114 in the original text where needed to distinguish the mass number from the atomic number, owing to the inability to utilize superscripts here.)

The host here recently directed me to a wonderful paper on the effects of relativity on the chemistry of heavy elements, which by the way, is evoked to account for the fact that mercury is a liquid rather than a solid.

It is here: Relativistic Effects in Chemistry: More Common Than You Thought (Pyykkö, Annual Review of Physical Chemistry, Vol. 63:45-64 (Volume publication date May 2012)

Have a nice Daylight Savings Time Sunday afternoon.








Uranium catalyzed electrolysis of water to produce hydrogen.

The paper I will discuss in this post is this one:
Uranium-mediated electrocatalytic dihydrogen production from water (Meyer et al Nature volume 530, pages 317–321 (18 February 2016))

First some bitter background:

I don't have much use for the anti-nuke ersatz "climate activist" Joe Romm, who I consider an appalling fool, but despite my general contempt for almost all of his rhetoric, there is one thing about it with which I agree: Hydrogen will never be a useful consumer fuel, useful for powering cars and other dubious artifacts of our modern "screw the planet and the future be damned" culture.

On this, he disagreed with his pal, fellow anti-nuke Moron Amory Lovins, who once promised us Hydrogen Hypercars in Showrooms by 2005 adding to his long list of stupid Ouija board quality prognostications about energy.

The referenced National Geographic puff piece on Lovins was published on October 16, 2001.

At Mauna Loa the weekly average for concentrations of the dangerous fossil fuel waste carbon dioxide in the planetary atmosphere posted on October 14, 2001 was 368.16 ppm.

On October 15, 2017, the posted figure from the same source was 403.97 ppm.

Nevertheless, irrespective of what a fool Amory Lovins is, hydrogen is, and for as long as an industrial society exists, will always be an important captive intermediate for a variety of products, the most important being ammonia, but for many other products as well, including fuels. Hydrogen can be used to reduce ("hydrogenate" ) carbon dioxide or carbon monoxide to make dirty fuels like gasoline (the Fischer-Tropsch process into which the Carter administration put lots of research effort) or clean fuels like dimethyl ether, and less attractively, methanol. This potential for a closed carbon cycle was enthusiastically advanced by the late great Nobel Laureate George Olah in his widely cited 2011 paper Anthropogenic Chemical Carbon Cycle for a Sustainable Future (Olah et al J. Am. Chem. Soc., 2011, 133 (33), pp 12881–12898)

Olah's dead, and despite his noble efforts during his magnificent life, the planet is still dying.

What Lovins, a poorly educated ignoramus who is nevertheless thought by some, including himself, to be a "real stable genius," was too stupid to understand, or simply deliberately avoided since he makes a lot of money "consulting" for huge and very dirty dangerous fossil fuel companies, is that 99% of the hydrogen on this planet is generated by the energy wasting process of reforming dangerous natural gas, and less commonly these days, coal.

Lovins liked to pretend, or at least convince his acolytes, that hydrogen could be industrially made by what he called "soft" technologies - they are actually environmentally egregious nightmares of unsustainable industrial chemistry - the solar driven electrolysis of water.

This is pretty funny, since Lovins, who made his name hyping "energy conservation," while apparently knowing zero about the laws of thermodynamics, never bothered to account for the fact that electrolysis of water is one of the most thermodynamically inefficient processes known for producing hydrogen. About 1% of the hydrogen on the planet is so produced, and of this 1%, almost all of it is produced as a side product in the production of chlorine gas utilized to make bleach, polyvinyl chloride and historically interesting molecules like DDT and CFC's. Until very recently and for most of the period of Lovins' awful career, the main electrode for undertaking these electrolysis efforts was a mercury electrode. Bleach produced still produced this way - and there is some - usually contains small amounts of mercury, making it the third largest contributor to mercury in the environment after coal burning and medical waste.

(By the way, despite all Lovins’ hype about energy conservation, the strategy has failed as badly as the solar and wind industries have failed. In 1973, world energy demand was estimated to be 256 exajoules. As of 2016, world energy consumption is 576 exajoules.

IEA 2017 World Energy Outlook, Table 2.2 page 79 (MTOE converted to exajoules.)
For the 1973 figure see Current Energy Demand; Ethical Energy Demand; Depleted Uranium and the Centuries to Come and references therein)



All the above said, the production of hydrogen via electrolysis also results in the isolation of heavy water which is useful in the production of stable labeled isotopes useful for chemical, biochemical, medical and environmental research. What should be equally important – or would be in a sane world – deuterium is a key component of a potentially extremely mass efficient type (particularly in thorium based cycles) of nuclear reactor, commonly called a CANDU reactor, a result of having been developed in Canada, but otherwise known more generally as a heavy water reactor. The main national nuclear energy program investing in this approach is India’s, although heavy water reactors do still operate in Canada.

Thus there is a role for electrolysis and for improving its efficiency.

This brings me to the paper cited at the outset of this post. The complexity of the electronic structures of the light actinide uranium and the multiple oxidation states suggests - as do other elements with this property of having multiple oxidation states . (This fact, the complexity of the electronic structure of uranium, was the subject of a recent post of mine in this space, Highly sensitive, uranium based UV detectors.)


As an “actinide,” uranium is expected to exhibit a +3 oxidation state, and it does. However the shielding of the 5f orbitals is less effective than it is for the corresponding lanthanides, where the filling of 4f orbitals results in lanthanide chemistry being being dominated by this +3 oxidation state, so much so, that the separation of the lanthanide elements from one another was long problematic.


Because of this ineffective shielding in uranium however, f orbitals are available for chemistry, and this is why, until the Seaborg actinide concept was developed and accepted, uranium was thought to be a cogener of tungsten, rather than a cogener of neodymium, with which it shares only limited chemistry.


Like uranium hexafluoride, a +6 compound, for example, a gaseous compound at moderate temperatures that plays a huge role in isotope separation both for nuclear power and for nuclear weapons, tungsten hexafluoride is a gas, and both tungsten and uranium form, for another example oxocations.

(However for reasons having more to do with quantum chemical formalism than actual chemistry, uranium is -rightly I think - considered an actinide, as is thorium, which effectively exhibits no f related chemistry at all, and in fact, doesn’t really possess a 3+ oxidation state of any significance.)

The availability of multiple oxidation states can be used to reduce water and this brings me (finally!) to a discussion of the paper cited in the opening paragraph of this post.

From the introductory text:

Depleted uranium is a mildly radioactive waste product that is stockpiled worldwide. The chemical reactivity of uranium complexes is well documented, including the stoichiometric activation of small molecules of biological and industrial interest such as H2O, CO2, CO, or N2 (refs 1–11), but catalytic transformations with actinides remain underexplored in comparison to transition-metal catalysis12–14. For reduction of water to H2, complexes of low-valent uranium show the highest potential, but are known to react violently and uncontrollably forming stable bridging oxo or uranyl species15. As a result, only a few oxidations of uranium with water have been reported so far; all stoichiometric2,3,16,17. Catalytic H2 production, however, requires the reductive recovery of the catalyst via a challenging cleavage of the uranium-bound oxygen-containing ligand. Here we report the electrocatalytic water reduction observed with a trisaryloxide U(iii) complex [((Ad,MeArO)3mes)U] (refs 18 and 19)—the first homogeneous uranium catalyst for H2 production from H2O. The catalytic cycle involves rare terminal U(iv)–OH and U(v)=O complexes, which have been isolated, characterized, and proven to be integral parts of the catalytic mechanism. The recognition of uranium compounds as potentially useful catalysts suggests new applications for such light actinides.


Here, from the paper, is the structure of the complex:



The caption:

Figure 2 | Independent synthesis and characterization of the uranium(IV) hydroxo complex [((Ad,MeArO)3mes)U–OH] (2–OH). a, Synthesis of 2–OH with concomitant H2 evolution. b, Molecular structure of the crystallographically characterized complex 2–OH in crystals of C67H84O5U ・ 3(C4H8O), with thermal ellipsoids at 50% probability. All hydrogen atoms except for the hydroxo H were omitted for clarity. c, Infrared vibrational spectra of 2–OH (black) and its isotopomer 2–OD (blue), showing the expected isotopic shift for the O–H stretching vibration ν. The inset is a close-up of the 2–OH spectrum, showing the two OH stretching frequencies at ν = 3,659 cm−1 and ν = 3,630 cm−1.


I very much doubt that this complex - and here I'm referring to the organic ligands and not the final synthesis shown in the graphic - is trivial to synthesize, but then again, it's a catalyst not a reagent, and depending on its stability and turn over rate, it might be viable to make it.

The authors propose the following mechanism for the hydrogen reduction reaction:



The caption:

Figure 3 | Postulated mechanism for the reduction of H2O by the U(iii) complex 1, based on EPR results. The addition of H2O to 1 probably yields a U(iii) aquo species, which forms a fleeting U(v) hydroxo–hydrido intermediate, [((Ad,MeArO)3mes)U(OH)(H)], by intramolecular insertion; this hydroxo–hydrido species then decays to a U(v) oxo species by elimination of H2 (reaction (1)). Subsequently, the U(iv) hydroxo complex 2–OH is formed in a comproportionation reaction between the U(v) oxo and the U(iii) aquo species (reaction (2)). In the net reaction, two U(iii) aquo complexes form two molecules of 2–OH and one equivalent H2.


Their experiments to confirm this mechanism sound like incredible fun:

To elucidate this mechanism, we performed time- and temperature- dependent EPR experiments with a reaction mixture of 1 and H2O in a frozen toluene solution at 7.5 K (Fig. 4). Initially, a spectrum of the neat U(iii) f 3 starting material (10 mM) in toluene was recorded, yielding an almost axial signal with g values centred at 1.56, 1.48, and 1.20 (see Supplementary Information), as expected for [((Ad,MeArO)3mes)U] (1)19. In the following measurement, a mixture of 1 (10 mM) in toluene with a sub-stoichiometric amount of H2O (0.375 equiv.) was prepared. Under these dilute conditions the reaction takes about 2 h at room temperature for completion...


Frozen toluene at 7.5K, I'd guess is made by dipping toluene in liquid helium; that my friends has to be fun.

And then...

Hence, the sample was allowed to equilibrate for 5 min at room temperature and then flash-frozen in liquid nitrogen to trap potential intermediate species in a frozen solvent matrix. Indeed, we obtained a convoluted spectrum of at least two species: the U(iii) starting material and another, welldefined rhombic species with simulated g values at 2.73, 1.83, and 1.35, consistent with an intermediate U(v) f 1 species (Fig. 4)


Here's the EPR spectrum:



And its caption:

Figure 4 | X-band EPR spectrum of a frozen 10 mM toluene solution of 1 with a sub-stoichiometric amount of H2O. The EPR data show a convoluted spectrum of two species: the U(iii) starting material and a well-defined rhombic species, tentatively assigned to the fleeting U(v) hydroxo–hydrido species. Experimental conditions are as follows: temperature T = 7.5 K, frequency ν = 8.96286 GHz, power P = 1 mW, modulation width of 1.0 mT. The experimental spectrum (black) and simulation (red) under these conditions are shown. The best fit for the experimental spectrum is a convolution of the signal of 1 in toluene (simulated, green; g values at g1 = 1.56, g2 = 1.48, g3 = 1.20, with line widths of W1 = 21.4 mT, W2 = 30.5 mT, W3 = 14.4 mT; relative weight of 1.0) and the signal of an additional, rhombic transient U(v) species (simulated, blue; g values at g1 = 2.73, g2 = 1.83, g3 = 1.35, with line widths of W1 = 18.9 mT, W2 = 25.5 mT, W3 = 26.5 mT; relative weight of 0.70). The spectra are offset for ease of viewing.


And finally the full cyclic mechanism of the electrolysis, wherein the oxidized uranium is reduced to U(III):



And its caption:

Figure 5 | Postulated electrocatalytic cycle for H2 generation from H2O in the presence of the homogeneous U(iii) catalyst [((Ad,MeArO)3mes)U] (1). Step 1 (top to bottom-right), H2 evolution and formation of [((Ad,MeArO)3mes)U(OH)(THF)] (2–OH) through oxidation of 1 with H2O. Step 2 (bottom-right to bottom-left), electrochemical reduction of 2–OH, forming the transient anion 2–OH−. Step 3 (bottom-left to top), elimination of OH– from 2–OH− to regenerate catalyst 1.


This device is a battery, and like all batteries, it wastes energy, however it wastes less energy than other electrolysis devices.

Regrettably the world has chosen, much to the detriment of the environment to choose to explore so called "renewable energy" to address climate change, surrounding this choice with all kinds of delusional statements designed to obscure the complete and total failure of this choice to address the expanding use of dangerous fossil fuels.

By their very nature, these systems are wasteful, since they necessarily require redundant systems, usually systems involving gas turbines. To the extent that the excess rotational energy of a spinning turbine being shut for a few hours so we can all make excited, if nonsensical, demonstrations of how great solar energy is, can be recovered, a battery is not a bad idea as a brake, as is the case in hybrid cars. At least some of the energy can be recovered and not wasted.

I actually think that this system, the uranium catalyzed electrolysis system might make sense in very limited circumstances, for example in remote systems, such as on space craft powered by RTG's, where the waste heat of the RTG might serve to provide operating temperatures for fuel cells operating on hydrogen.

Large scale energy storage should be a non-starter on environmental grounds but this is not culturally accepted yet, given the general contempt for science and the inexplicable pop enthusiasm for so called "renewable energy."

A better use for depleted uranium in my view, would be to convert it to plutonium and fission it, but that's just my view.

Have a nice evening, and if you're in this Nor'easter, as I am, by all means be safe.



Sexual Harassment in Science.

As a culture, it is a good thing from my perspective on which to reflect.

This video on this interesting question is from the American Chemical Society.

Especially for senior people, it's worth reflecting on the type of environment provided in your work place.

https://www.acs.org/content/acs/en/acs-webinars/popular-chemistry/harassment/video.html



Understanding the Relationship Between Chemical Feedstocks and Dangerous Fossil Fuels.

Recently in this space, I posted a very esoteric piece - so esoteric that it understandably provoked no comment - on the preparation of p-xylene from dimethylfuran, a chemical that is accessible from biomass such as straw.

The Conversion of Cellulosic Biomass Into Aromatic Compounds.

In so doing, I failed to apply a lesson I often - albeit with very limited success - try to evoke whenever one hears these "feel good/sound good" bits of environmental wishful thinking - which is to think about scale. For instance, the scale of world energy consumption as of 2016 was 576 exajoules per year - fraction of which that is derived from dangerous fossil fuels has been rising not falling throughout the 21st century - and all of the endless hype about the solar industry's "percent" growth is merely an attempt to bury the issue of scale. Wind and solar energy combined, despite all the cheering, did not produce 10 exajoules of energy in 2016 and thus has been insignificant, is insignificant, and always will be insignificant.

A recent publication in one of my favorite journals Environmental Science and Technology has served for my inattention to issues of scale in referencing a lab scale process as significant; there's a long way between "there" - "there" being significance - and "here," "here" being a world in which the collapse of the planetary atmosphere is accelerating and not as popularly imagined, even remotely being addressed. The paper is this one, about the role that dangerous fossil fuels play in the chemical industry, the chemical industry being at the very core of and essential to our way of life, pretty much involved in everything a modern bourgeois person - such as I am - does. Here is the paper: Mapping Global Flows of Chemicals: From Fossil Fuel Feedstocks to Chemical Products (Levi and Cullen, Environ. Sci. Technol., 2018, 52 (4), pp 1725–1734)

This graphic from the paper shows pretty much everything you need to know about it:



(Similar types of flow diagrams for energy are widely available from the Lawrence Livermore Laboratory and other places. I sometimes post a particular version here and there showing the energy flow diagram for Denmark, that offshore oil and gas hellhole showing how trivial its much ballyhooed and hyped wind industry is.)

Anyway.

From this diagram, one can discern the world requirement for "BTX" (Benzene, Toluene and Xylenes) is on the order of 80 million tons, of which roughly 70 million tons is carbon. This compares to the average annual average amount of carbon dioxide that is routinely dumped into the atmosphere while we wait for the grand super duper renewable energy nirvana that never comes, roughly 35 billion tons of CO2, corresponding to about 15 billion tons of carbon.

70 million tons may be accessible via "waste" biomass. Over on another website where I was banned for telling the truth, I roughly calculated from available references that the total carbon content of all the straw in China is roughly 267 million tons.

This of course does not account for transporting and processing all the straw in China, of course, just so I'm not encouraging false optimism.

According to the cited paper, the world chemical industry's contribution to climate change from direct by products of the chemicals themselves as carbon dioxide, is relatively small, 267 million tons, or less than 1%. More serious is the release of methane, and probably less serious, but significant all the same, is the contribution to climate change from nitrous oxide, a side product of the ammonia industry on which our food supply depends:



However this ignores the energy input of chemical processing, which is far more significant.

From the opening text of the paper we have these remarks from the authors:

Industrial chemicals and their derivatives pervade modern society. Although often diffuse in their application (e.g., pharmaceuticals), the bulk outputs of the chemical and petrochemical sector, (also referred to here as "the chemical sector" ), are deployed in huge volumes to make millions of tonnes per year (Mt yr–1) of chemical products, such as fertilizers and plastics. Our industrialized economy is dependent on chemicals.

In performing this pivotal role, the chemical sector exerts a large environmental burden. It is responsible for approximately 7% of global anthropogenic global greenhouse gas (GHG) emissions, and 5.5% when only counting CO2 emissions.(1) The sector’s final energy consumption is the largest among industrial sectors: 42.5 EJ in 2014, of which 25 EJ is feedstock energy.(2) Other sources of emissions include those stemming directly from the chemical transformations mobilized in reactors (process emissions), and from energy conversion in the transformation sector (indirect emissions). In addition to these gaseous emissions, chemical products can spawn pernicious aqueous discharges. The oft-publicised problem of fertilizer runoff contributing to hypertrophication,(3) and the more recent exposition of plastic waste ending up in the world’s oceans(4, 5) and organisms(6) are notable examples.


Returning to the issue of the ammonia industry, it is worth noting that 55 million tons, graphically it seems to be on the order of 1/3 of the total, comes from coal, the most dangerous of the three dangerous fossil fuels. Coal is often reported as being "dead," which is nonsense; reports of its death are greatly exaggerated, to steal a Twainism. Between 2000 and 2016 coal was the fastest growing source of primary energy on this planet, increasing by 2/3 of the amount used in 2000 (roughly 90 exajoules worth) by 60 additional exajoules. The contribution that coal makes to ammonia synthesis may be trivial in comparison to its use in the energy and steel industry, but it is real and significant.

I found this paper thought provoking, and it served for a useful refocusing on the realities of our increasingly dire environmental situation.

If we want to be serious - and there's no way that we are even remotely so in any country or even in any political party in any country - scale is the most important thing of which we can think.

I hope you're having a pleasant weekend.

Nature Climate and Atmospheric Science: Dramatic declines in snowpack in the western US

According to this open sourced paper in Nature Climate and Atmospheric Sci, the Western US Mountains Can't Hold Snow; the West Can't Get Water: Dramatic declines in snowpack in the western US (Mote, et al npj Climate and Atmospheric Sciencevolume 1, Article number: 2 (2018)

This is not a short term event. It's a trend.

California’s recent multi-year drought (2011–16) and its extension into Oregon and Washington has shown that warming can create drought simply by preventing the accumulation of mountain snowpack. The year 2015, for instance, set the record low 1 April snow water equivalent (SWE) at over 80% of sites west of 117° longitude,1 a result of high winter temperatures rather than low precipitation.2,3,4

More than a decade ago, we showed that spring snowpack had declined at a large majority of locations in the mountainous western US, and corroborated the observations with hydrologic modeling that reached broadly similar conclusions.5 We also noted that computing an area-averaged snowpack value from observations is challenging because the locations of long-term monitoring sites are usually chosen to favor a certain type of terrain and elevational range, with temperature-sensitive locations undersampled early in the record in some states.6 Methodological choices (e.g., about record length) can therefore strongly influence results and must be carefully evaluated. In contrast, model-based estimates provide a basis for estimating long-term SWE changes across the entire Western U.S. domain.

Since our earlier work, several papers have further explored the relationships between mountain snowpack, variability and trends in precipitation and temperature, and geographically important factors. Stoelinga et al. (ref. 7) derived a snowpack index for the Cascades from streamflow measurements, from which they estimated that the spring snowpack declined 23% between 1930 and 2007. Pierce et al. (ref. 8) using a hydrologic model forced by observations and by two 1600-year climate model runs to estimate natural internal climate variability, attributed declines in snowpack (specifically SWE divided by accumulation-season precipitation) across the western US to anthropogenic warming...


The article is, again, open sourced and there's not a whole lot of need to go over or quote the rest of it. It's pretty clear.

It seems to be involved with something called "climate change." A lot of whiny people have been carrying on about it, but fortunately we've successfully been able to completely and totally ignore them.

Don't worry; be happy.

California has lots of wind turbines and lots of solar cells and therefore all of our problems will shortly be solved, because they, and the natural gas on which they depend most of the time, are clean and green.

Have a nice Friday.

The Conversion of Cellulosic Biomass Into Aromatic Compounds.

Most of the chemicals utilized in the preparation of polymers are currently derived from petroleum, and to the extent they are degraded either by combustion or other means, the represent a climate risk.

Since we have, in our times, spectacularly failed to address climate change, offering in lieu of things that actually work truckloads of wishful thinking (solar and wind) future generations will need to clean up our mess, the biggest mess being the planetary atmosphere and the oceans with which they are in a shifting equilibrium.

Although plastics represent a huge environmental problem, the problem would be mitigated to the extent that they were obtained from air rather than from petroleum, since in the former case, they would represent sequestered carbon.

Some years back, there was a lot of talk about converting cellulosic materials into ethanol via fermentation schemes of various types. All of these efforts have more or less commercially failed, probably because, among other things, they were water and energy intensive.

However, the chemical dehydration of cellulosic materials, generally with acid and heat, is known to produce compounds in a class known as furans, five membered unsaturated rings, generally with one or two single carbon side chains. (Historically almost all the furan in the world was made from oat hulls, until petrochemicals replaced them via a route from butadiene obtained from dangerous fossil fuels.)

Here, for example is the structure of dimethylfuran:



A problem with biomass to chemicals conversion has been, however, the low production of aromatic compounds like benzene, toluene and the xylenes, one of which p-xylene, aka as 1,4-dimethylbenzene is an important precursor to common plastics like PET, polyethylene terephthalate, a polymer used in bottles and in clothing. Xylenes are also important constituents of cleaners, fuels, paints and varnishes, especially those requiring special properties such as in works of art.

It is thus with interest I came across the following paper published by Chinese scientists in the scientific literature: One-Step Conversion of Biomass-Derived Furanics into Aromatics by Brønsted Acid Ionic Liquids at Room Temperature (Zhang et al, ACS Sustainable Chem. Eng., 2018, 6 (2), pp 2541–2551)

The introduction covers what I just said.

Aromatics are elementary commodity products from petroleum resources. For example, p-xylene (PX) is a fundamental aromatic hydrocarbon and serves as the feedstock for the production of polyethylene terephthalate (PET), polybutylene terephthalate (PBT), coatings, dyes, and so on.1−3 With a research octane number of 127 and low toxicity, PX is regarded as an excellent octane booster while the price has limited its application.4 Since the last century, fossil resources have constituted the main feedstocks for the production of most fuels, chemicals, and materials, but the environmental concerns together with diminishing fossil reserves result in a global challenge. Efficient processes that enable the production of valuable products from renewable feedstocks with high yields must be developed to reduce global warming while satisfying the growing energy demands...


The authors express their goal and what they have accomplished a little further on:

one-step synthetic route at mild conditions with high selectivity would be a significant advance in the conversion of furanics into aromatics. Herein, we report a novel process to efficiently obtain PX and 2,5-methylbenzoic acid (2,5-DMBA) by acidic ionic liquids from biobased DMF and acrylic acid which can be produced by oxidative dehydration of the side-product from biodiesel production (i.e., glycerol).34,35 The reaction including Diels−Alder cycloaddition, dehydration, and decarboxylation could be accomplished conveniently at room temperature and atmospheric pressure as shown in Scheme 1c. The predominant success of this efficient conversion relies on the unique properties of ionic liquids (ILs) used as solvents and acidic catalysts to suppress the retro Diels−Alder reactions and side-reactions. For further understanding of the reaction mechanism, isotopic labeling and computational study were used. We also highlighted the generality of this catalytic system with a series of related furanic compounds and dienophiles; then, moderate aromatic yields were obtained, and the influence of different substituents of the reactants are also described.


Reference 35, on dehydrating and oxidizing glycerol to give acrylic acid is this one from the same journal: Highly Selective Production of Acrylic Acid from Glycerol via Two Steps Using Au/CeO2 Catalysts

The "ionic liquids" are salts, usually with one or two organic species, that are liquid at or near room temperature. Most of those used in the paper are of the alkylimidazole type, albeit mostly with inorganic counterions like sulfates or phosphates.

Some pictures from the paper:



The picture shows a tree as the source, but this is unnecessary, straw and things like corn cobs would work quite as well, if not better. Wood, by the way, is a source of aromatic compounds, from the lignin they contain in addition to cellulose, but in general they are phenolic, having one or more acidic -OH moieties on the aromatic ring.

Here the authors compare their work, (c), with those of previous authors working on the same idea, furans to aromatics:



Here is some graphics showing the yields and selectivity under several conditions:



The caption:

Figure 1. (a) Conversion of DMF and yield and selectivity of aromatics as a function of time at 25 °C. (b) Effect of temperature on DMF conversion and aromatic yield. (c) Effect of temperature on aromatic selectivity. Reaction conditions: 1 mmol of DMF, 6.9 mmol of acrylic acid, 2 mmol of [Bmim]HSO4, (b, c) 60 min (10, 25 °C), 30 min (40, 55, 70 °C).


PX is paraxylene, 2,5 DMBA is 2,5 dimethyl benzoic acid.

Reaction parameters:



The caption:

Figure 2. (a) Kinetics of the reaction between DMF and acrylic acid at different temperatures. Reaction conditions: 1 mmol of DMF, 6.9 mmol of acrylic acid, 2 mmol of [Bmim]HSO4. (b) Arrhenius plot for the conversion of DMF catalyzed by [Bmim]HSO4 from 10 to 70 °C.


Reaction mechanisms leading to the two main aromatic products:



Note the role of the inorganic anions.

The free energy diagram associated with this mechanism:



The authors thus conclude:

In summary, the one-step conversion of biobased furanics into aromatics via a synthetic route including Diels−Alder, dehydration, and decarboxylation reactions can be efficiently catalyzed by acidic ILs at mild conditions. [Bmim]HSO4 gave high yield of PX and 2,5-DMBA from DMF and acrylic acid with up to 89% aromatic selectivity in a single step at room temperature. The reaction mechanism supported by computational simulation and isotopic tracing was studied, and the energy barriers of every elementary step were presented. With application of [BSO3HMIm]HSO4 to the reactions using different dienes and dienophiles, moderate yields of various aromatics were obtained, which suggested the great potential to obtain excellent yield of renewable aromatics by tuning the structure and properties of ILs, particularly the acidity. It was also proven that the electron-donating methyl groups on the furan ring could significantly benefit the dehydration and decarboxylation processes.


Interesting I think, esoteric but interesting.

Have a pleasant Tuesday tomorrow.

Charles Ball describing being taken from his mother forever.

Recently in this space, I was describing the pain of reading the book The Half Has Never Been Told about the relationship between the origins of all American wealth, past and present, and human slavery:

I can only read this book in short spurts until the pain becomes too great. Read it, I must.

The early chapter makes considerable reference to the autobiographical work of the escaped slave Charles Ball, Slavery in the United States: a narrative of the life and adventures of Charles Ball, a black man, who lived forty years in Maryland, South Carolina and Georgia, as a slave,

Yesterday during my library research into other topics connected with my scientific work, I paused to download an electronic version of Ball's book, which begins with a description of being taken from his mother.

I reproduce a portion here:

My story is a true one, and I shall tell it in a simple style. It will be merely a recital of my life as a slave in the Southern States of the Union—a description of negro slavery in the “model Republic.”

My grandfather was brought from Africa and sold as a slave in Calvert county, in Maryland. I never understood the name of the ship in which he was imported, nor the name of the planter who bought him on his arrival, but at the time I knew him he was a slave in a family called Maud, who resided near Leonardtown. My father was a slave in a family named Hauty, living near the same place. My mother was the slave of a tobacco planter, who died when [Page 10] I was about four years old. My mother had several children, and they were sold upon master’s death to separate purchasers. She was sold, my father told me, to a Georgia trader. I, of all her children, was the only one left in Maryland. When sold I was naked, never having had on clothes in my life, but my new master gave me a child’s frock, belonging to one of his own children. After he had purchased me, he dressed me in this garment, took me before him on his horse, and started home; but my poor mother, when she saw me leaving her for the last time, ran after me, took me down from the horse, clasped me in her arms, and wept loudly and bitterly over me. My master seemed to pity her; and endeavored to soothe her distress by telling her that he would be a good master to me, and that I should not want anything. She then, still holding me in her arms, walked along the road beside the horse as he moved slowly, and earnestly and imploringly besought my master to buy her and the rest ofher children, and not permit them to be carried away by the negro buyers; but whilst thus entreating him to save her and her family, the slave-driver, who had first bought her, came running in pursuit of her with a raw-hide in his hand. When he overtook us, he told her he was her master now, and ordered her to give that little negro to its owner, and come back with him. [Page 11]

My mother then turned to him and cried, “Oh, master, do not take me from my child!” Without making any reply, he gave her two or three heavy blows on the shoulders with his raw-hide, snatched me from her arms, handed me to my master, and seizing her by one arm, dragged her back towards the place of sale. My master then quickened the pace of his horse; and as we advanced, the cries of my poor parent became more and more indistinct—at length they died away in the distance, and I never again heard the voice of my poor mother. Young as I was, the horrors of that day sank deeply into my heart, and even at this time, though half a century has elapsed, the terrors of the scene return with painful vividness upon my memory. Frightened at the sight of the cruelties inflicted upon my poor mother, I forgot my own sorrows at parting from her and clung to my new master, as an angel and a saviour, when compared with the hardened fiend into whose power she had fallen. She had been a kind and good mother to me; had warmed me in her bosom in the cold nights of winter; and had often divided the scanty pittance of food allowed her by her mistress, between my brothers, and sisters, and me, and gone supperless to bed herself. Whatever victuals she could obtain beyond the coarse food, salt fish and corn bread, allowed to slaves on the Patuxent and Potomac rivers, she carefully, distributed [Page 12] among her children, and treated us with all the tenderness which her own miserable condition would permit. I have no doubt that she was chained and driven to Carolina, and toiled out the residue of a forlorn and famished existence in the rice swamps, or indigo fields of the South.

My father never recovered from the effects of the shock, which this sudden and overwhelming ruin of his family gave him...


Unbelievable, absolutely unbelievable...

Lest we forget, this is who we are.

Cogenerating Thermochemical Hydrogen While Recovering Waste Copper.

The paper from the primary scientific literature to which I'll refer is this one:

Co-production of Hydrogen and Copper from Copper Waste Using a Thermochemical Cu–Cl Cycle (Farrukh Khalid* , Ibrahim Dincer, and Marc A. Rosen, Energy and Fuels, 2018, 32 (2), pp 2137–2144)

There are many hydrogen cycles known, water splitting thermal cycles. The CuCl2 cycle is just one of them, other examples include the much studied sulfur-iodine cycle and variations, various cerium cycles (which include carbon dioxide splitting options), zinc cycles...etc...etc.

I've dreamt up a few variations on my own, although I have no idea whether they would actually work.

In general, they all feature the possibility of high thermal efficiency, since they are easily coupled to thermal processes for electricity generation, the generation of heat for chemical processing, and the production of pure oxygen that may be utilized for closed combustion systems that will not involve smokestacks and will, to the extent that oxygen is used to combust biomass, allow for the recovery of carbon dioxide from the atmosphere for its removal.

One limitation of these cycles involves materials science, although we have in recent decades developed some spectacularly refractory materials and others are clearly on the horizon.

One of the problems that humanity faces however is the depletion of important elements in the periodic table, including some in the popular, but spectacularly failed, so called "renewable energy" industry, which is in fact, is neither "renewable" nor sustainable for precisely this reason.

When elements are distributed, as in "distributed energy" their recovery involves energy, and the more diffuse they are, the more distributed they are, the more energy is required to reconcentrate them into a recoverable and useful form. This is a consequence of the second law of thermodynamics, which cannot be repealed by the legislature of California (where such repeal is often proposed, albeit usually "by 'such and such' a date, when conveniently, the people voting on the repeal will be either out of office or dead) or by any other legislature or even by any ersatz or real dictator, orange or otherwise.

The dilution of elements or molecules is known as "the entropy of mixing."

An essential element in our modern life is copper, which is ever more critical particularly because of the sloppy ways we use it, in low capacity utilization systems such as wind turbines, which, since they require redundancy as well as the use of large mass collection systems, and when these systems turn into landfill, the recovery of copper in them will require energy.

That's why this paper is of interest.

From the introduction:

The use of energy plays an important part in the progress of any country. With increasing populations and rising living standards in many countries, the demand for energy is growing. The present dependence upon fossil fuels to meet most of this energy demand and the challenges associated with fossil fuels has led to research around the world to develop environmentally benign energy sources, such as renewable and nuclear. During the past decade, there has been an increasing interest in the development of large-scale non-fossil hydrogen production technologies, particularly coupled with renewable and nuclear process heat/waste heat, which leads to clean hydrogen production with almost negligible life cycle emissions and, hence, minimized environmental impact. In this regard, thermochemical and/or electrochemical processes with a renewable or nuclear option offer an environmentally friendly option.(1-5)


I agree with part of the last statement. Nuclear energy is environmentally friendly, but in my oft expressed opinion, so called "renewable energy" is not.

Hydrogen is not an acceptable fuel, but it an extremely useful captive intermediate where it can be utilized to make sustainable fuels - my personal favorite being dimethyl ether, DME - via the hydrogenation of carbon dioxide (or monoxide).

The introduction continues:

A number of thermochemical cycles have been investigated(6-8) to produce hydrogen from water. However, most of these cycles operate at over 800°C. The relatively lower temperature (550 °C) requirement and use of inexpensive chemicals make the copper–chlorine (Cu–Cl) thermochemical cycle a promising process for hydrogen production. To build large-scale hydrogen production facilities based on this cycle, some challenges need to be resolved. First, the difficulty in separation of CuCl and CuCl2 from the spent anolyte in the electrolytic step needs to be addressed. Second, some copper crossover is observed in the electrolyzer membrane, resulting in degradation of the electrolyzer performance. One of the possible ways to achieve better kinetics and integration is the introduction of a high-temperature electrolysis step in the Cu–Cl cycle. Such a high-temperature electrolysis step needs to be thoroughly examined in terms of feasibility and practical viability.

Copper is one of the most widely used metals in the world, with applications including energy technologies, electronic devices, electricity transport, and coin production. With advances in electrical and electronic technology and decreases in prices, the use of such equipment has increased.(9, 10) This has led to increases in copper waste, especially in the industrial world,(11) posing a worldwide challenge for safe disposal.(12, 13) There are numerous methods available to recycle copper from copper waste, such as pyrometallurgy and hydrometallurgy.(14-17) However, each process has drawbacks. For instance, the energy consumption is very high and the temperature requirement is high (more than 1273 K) in pyrometallurgy...


Here, from the paper, is a schematic of the particular copper chloride cycle the authors envision. Note that their cycle requires an electrical input, but not all cycles, not even all copper chloride cycles, do:



Their purpose in including electricity is to reduce the temperatures required. With advances in materials science, this may not be necessary.

Their particular cycle relies on the oxidation of chlorine gas at 950K with water (steam) to give HCl gas and oxygen, and the HCl gas is reacted with copper wastes to generate hydrogen and cuprous chloride (copper (I) chloride) and hydrogen at around 770K, a temperature at which the cuprous chloride is a liquid, simplifying mass transfer. This liquid is electrochemically disproportionated into copper metal and cupric chloride (CuCl2 - copper (II) chloride) and the latter is thermochemically decomposed at 883 K to give chlorine gas and copper metal.

Here's a schematic of the electrochemical step:



Here's a photograph of the actual lab scale operating system:



I used to love putting stuff together that looked like that when I was in the lab. It makes one feel all "sciency." (Sometimes modern instrumentation can look too clean to be fun.)

There's a nice discussion of the thermodynamics in the paper, as well as a simple graphic that shows the story:



The caption:

Figure 6. Specific exergy destruction and exergy efficency of the various steps of the proposed Cu–Cl cycle.


A number of other graphics in the paper discuss optimization of the temperatures for each step. The interested reader may refer to the original either by subscription or by traveling to a good scientific library.

Note that the electrochemical portion may not be strictly necessary, depending on process parameters, and indeed on chemistry. A well known variant of copper based thermochemical cycles is the copper bromide cycle, and indeed iodide cycles also are possible.

Usually at this point someone will mention cost, usually in the context of declaring that "nuclear energy is too expensive" among other distorted views by which anti-nukes morph into Ayn Rand type Laissez Faire capitalists, usually with a healthy dollop of selective attention.

So called "renewable energy" is not cheap unless it is isolated from the environmentally questionable necessity for redundant back up whenever the sun isn't shining - sunlight is widely reported to disappear for various amounts of time depending on latitude and season - and the wind isn't blowing.

The reality is that the back up - despite all the horseshit about Elon Musk's (and other) unsustainable batteries - is dangerous natural gas, also reported as being "cheap."

It's "cheap" only if someone other than the user pays for cleaning up the trash it leaves behind, for example, carbon dioxide, radioactive flowback water, permanently leaching spent fields, etc.

The people consigned to pay for these clean ups are not the users; it is rather all future generations, our children, our grandchildren, their children, their great grandchildren etc.

The fact is that the dangerous fossil fuel industry is simply allowed to dump its waste directly into the planetary atmosphere without restriction, and without cost, while cleaner forms of energy, notably nuclear energy, are required to show that they can contain all by products indefinitely, over as long a period as stupid people can imagine, even though nuclear materials have a spectacular record of not killing many people, while fossil fuel waste kills millions upon millions of people year after year after year after year with little comment.

Because of this situation, so called "natural gas" is described as being "cheap" even though it is no such thing.

In recent weeks I've been reading about the history of human slavery in this country; a horrible story that is very difficult to read. Sometimes I have to put the books I'm reading down weeping; they're too painful to read but innocent people were required to live these events.

It is hard not to express profound disgust at the generations of white Americans of those times in which human slavery was legal in this country, and the twisted mentality that sought to perpetuate this great crime for many unimaginably cruel generations.

And then I think about how future generations might regard our generation, and I'm not comforted by the thought.

Since all current schemes to stop dumping the dangerous fossil fuel waste carbon dioxide into our favorite waste dump, the planetary atmosphere, have all failed, future generations will be required to clean up our garbage, this while having fewer resources than our generation enjoyed - and squandered - with complete disregard for them.

To get resources, they'll have to dig through our garbage, and probably face huge health risks in doing so. It's hard to think they'll think kindly on us any more than I think kindly on the purveyors of human slavery in the United States.

Maybe processes described in this paper might help a little, but irrespective of leaving them with the paltry record of such unscaled experiments they will be totally in their rights, in my view, to view us with as much or more disgust as I - more than a century later - view the slaveholders and their enablers, North, South, and everywhere else.

Have a pleasant Sunday tomorrow.

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.
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