A Uranium Adsorbing Alginate Polyacylonitrile Membrane With Superior Regeneration Performance.

[NNadir]

The paper I'll briefly discuss is this one:

Preparation of Amidoxime Polyacrylonitrile and Sodium Alginate Composite Membrane with Superior Regeneration Performance for Efficient Uranium Adsorption Yunyang Gui, Guoyan Qi, Nannan Xie, Qiufang Li, Xiaoli Su, Yang-Hai Zheng, Hui Ruan, Yongde Yan, Yun Xue, Sheng Wu, and Fuqiu Ma Industrial & Engineering Chemistry Research 2026 65 (13), 7108-7119

In the presence of an oxygen atmosphere, uranium supplies on the planet Earth are inexhaustible. There is no technology that can consume all of this mildly radioactive element - the decay series of which supplies the bulk of the internal heat of the planet - although members of its decay series, the formation of which can be prevented by fissioning the parent nuclide, are highly radioactive. Uranium is continuously cycled through the Earth's crust from the mantle by volcanism and continental uplift, where erosion causes it to be, given its low but significant solubility in the +6 valence state, generally is a series of acquo complexes related to the UO₂²⁺ ion, a U(VI) species, washed to the sea. The uranium that is washed by rivers into the ocean, accumulates until the solubility is exceeded, whereupon it precipitates and is returned to the mantle by subduction.

The uranium content of the world's major rivers has been measured and is recorded in this publication and many other publications:

François Chabaux, Jean Riotte, Norbert Clauer, Christian France-Lanord, Isotopic tracing of the dissolved U fluxes of Himalayan rivers: implications for present and past U budgets of the Ganges-Brahmaputra system, Geochimica et Cosmochimica Acta, Volume 65, Issue 19, 2001, Pages 3201-3217.

A table from that paper:



The output of the Ganges river system, 1176 metric tons (1176 X 10⁶ grams) The amount of uranium released into the Indus river, converted to plutonium by neutron capture in nuclear reactors, is equal to close to 100 Exajoules of primary energy each year.

Overall, it is now understood that uranium content of the Earth's oceans is roughly 4.5 billion tons, at a concentration of about 3.3-3.4 micrograms per liter. Captured and converted to plutonium, this is the equivalent of over 500,000 years of human energy consumption at a prodigious energy demand of 700 Exjaoules/year, 50 Exajoules more than we are consuming as of now from all sources of energy, including the largest source of energy, about which antinukes and "I'm not an antinuke" antinukes couldn't care less, dangerous and deadly fossil fuels, which are destroying the planetary atmosphere.

It is true that almost all of the Earth's major riverine and riparian systems have been sacrificed to so called "renewable energy" - a scheme to industrialize all wilderness systems from rivers, deserts, mountain tops and even the seas themselves, so people can continue to worship their cars, go to "no nukes" rock concerts, and log on the internet to see "influencers" - whatever the hell they are - and thus the recharge from rivers is limited in these times. I have argued however, in a sample case of California, that it might be possible to restore riverine systems to free flow along with other bodies of water via supercritical water desalination:

The Energy Required to Supply California's Water with Zero Discharge Supercritical Desalination.

In addition, we are mining fossil groundwater all over the world, and as ground water flows to granite and other minerals with significant uranium content, many of these water supplies are contaminated with NORM (Naturally Occurring Radioactive Materials) most prominently with uranium, but also its radioactive decay series products. The flowback water from fracking operations in Pennsylvania is far more radioactive than the trivial tritium concentrations released at Fukushima about which all of our dumb antinukes carry on, but again, antinukes and "I'm not an antinuke" antinukes couldn't care less about fossil fuels, even when they release vast amounts of radioactivity. (Coal ash is a significant source of uranium.)

Although uranium is ubitiquous, and its native radioactivity - excluding, again, decay products - is low owing to its long half-life, thus meaning it isn't very dangerous from a radiological sense, it is a chemotoxin, leading to kidney damage. Thus removing uranium from mined groundwater is a good idea, making it a source of uranium for energy purposes.

This brings me to the paper cited at the outset, which begins with some statements I personally think are nonsense, irrespective of the fine paper's and introduction's other content.

The introductory text:

Under the dual challenges of surging global energy demand and the accelerating depletion of nonrenewable energy sources, nuclear energy has gained increasing attention as a high-efficiency, low-emission alternative. This accelerated development has, in turn, heightened the global demand for uranium resources. (1,2) However, as a fundamentally nonrenewable element, uranium sourced from terrestrial deposits is nearing depletion, underscoring the urgent need to identify alternative supply routes. Among the various strategies under consideration, uranium extraction from seawater (UES) has emerged as a promising pathway to supplement uranium supplies and support the long-term sustainability of nuclear energy. (3,4) Additionally, throughout the nuclear fuel cycle, a large amount of uranium-containing radioactive waste is generated, which poses chemical toxicity and radioactive hazards, causing irreversible harm to the natural ecosystem and human health. The removal and recovery of uranium from both waste liquids and seawater are of strategic importance, particularly in light of growing nuclear energy demands and environmental sustainability concerns. To enable the efficient enrichment and recovery of uranium from water, a range of methods has been developed, including electrocatalysis, (5) photocatalysis, (6) ion exchange, (7) chemical precipitation, (8) membrane separation, (9) and adsorption. (10) Among these, adsorption has attracted increasing attention owing to its operational simplicity, economic feasibility, and high efficiency and is now widely applied in the treatment of uranium-containing solutions.

Substantial advancements have been made in the field of uranium adsorption by using a variety of functional materials. Notable progress has been reported for systems based on inorganic compounds, (11) synthetic polymers, (12) naturally derived biomass, (13) metal–organic frameworks, (14) covalent organic frameworks, (15) and ion exchange resins. (16) Among them, membrane-based polymer materials have often been used as adsorbents due to their advantageous properties, including facile synthesis, modification, and chemical stability. In particular, the superior coordination affinity of amidoxime (AO) toward U(VI) made membrane materials containing such groups widely used for uranium adsorption. (17,18) For instance, Chen et al. (19) synthesized a polydopamine–amidoxime polyacrylonitrile membrane through a combination of dopamine polymerization/deposition and nonsolvent-induced phase separation. This membrane exhibited a remarkable uranium adsorption efficiency and selectivity. In another study, Sun et al. (20) fabricated an ultrathin PAO-based membrane by incorporating quaternized chitosan and PAO into a cross-linked sulfonated cellulose nanocrystal matrix, demonstrating excellent antibiofouling properties and significantly enhanced uranium adsorption capacity.

Concurrently, in response to growing environmental concerns, the biodegradability of polymer adsorbent materials is gradually gaining attention. (21) Sodium alginate (SA), as a natural polysaccharide, is particularly attractive due to its biodegradability, biocompatibility, and renewability and is rich in functional modifying groups such as carboxyl and hydroxyl groups. Its excellent film-forming ability and structural stability make it a favorable candidate for material synthesis...]

Alginate is a biologically sourced material, obtained from seaweed; acrylonitrile is a petroleum product. Theoretically, although not practically in the current world, acrylonitrile can be synthesized from biological materials and/or via a methanol based pathway via the hydrogenation of carbon dioxide or graphite produced via the Boudouard reaction driven by nuclear heat.

This is hardly the first paper written about pathways to extract uranium from seawater, groundwater, or process water using amidoximine functionalized polymers; there are literally thousands of such papers, going back over decades, but the paper claims the process is more selective than many other options, and is readily subject to reuse.

Some graphics from the paper:

A synthetic scheme cartoon from the abstract:



Another synthetic scheme cartoon from inside the paper:



The caption:

Figure 1. Schematic diagram for the synthesis of PAO-SA composite membrane.

The caption:

Figure 4. Kinetic model fitting curves correspond to the following models: (a) Pseudo-first-order, (b) Pseudo-second-order, and (c) Intraparticle diffusion. The isotherm model fitting curves for (d) Freundlich and (e) Langmuir at different temperatures. (f) Thermodynamic fitting calculations between ΔGθ and the temperature.

The caption:

Figure 5. (a) Adsorption partition coefficients (Kd) and adsorption rates, (b) adsorption capacity, and (c) the ratio of partition coefficients of PAO-SA for U(VI) and coexisting ions in simulated seawater. (d) Relationship between adsorption time and capacity of uranium spiked with different concentrations in real seawater. (e) Effect of different low concentration uranium on adsorption. (f) Effect of different amounts of PAO-SA on uranium adsorption in real seawater.

The caption:

Figure 6. Effect of (a) eluent type, (b) eluent concentration, (c) desorption time, (d) solid–liquid ratio, and (e) number of adsorption–desorption cycles on the desorption rate. (f) Effect of cycle number on the swelling rate of PAO-SA.

A table from the text comparing the performance of the authors' product with a small selection of others from the literature:



I have argued, and will continue to argue, that with incorporation of fast neutron spectrum nuclear reactors as well as adjustment of CANDU type thermal reactors incorporating ternary uranium, thorium, plutonium fuels, the uranium already mined, as well as the thorium dumped in tailings from lanthanide mines that serve, among other things, to support the useless wind industry, that humanity could provide all of its energy needs - eliminating all oil, gas, coal mines, as well as restoring wilderness industrialized for useless so called "renewable energy" junk - for centuries.

Nevertheless, products as those described in this paper (and many other papers), can help clean up naturally uranium and NORM contaminated groundwater, fracking wastewater as well as process water from uranium processing plants. (I personally do not like extraction procedures for nuclear fuel processing, and greatly prefer the fluoride volatility type and related pyroprocessing schemes.) The uranium so removed from these sources can then be available as fuels.

From the paper's conclusion:

In summary, in this work, PAO solution was synthesized in the homogeneous phase with sodium thiocyanate solution for the first time, and then SA was added to enhance the hydrophilicity and membrane-forming property of the material. Ultimately, the PAO-SA composite membrane was prepared by nonsolvent phase separation. The static adsorption experiments showed that the PAO-SA reached equilibrium after 6 h of adsorption at 298 K and pH = 6.0, with an adsorption capacity of 326.1 mg/g. Analysis of the relevant data using various kinetic and thermodynamic models revealed that both the pseudo-second-order kinetic and Langmuir isotherm models effectively described the adsorption process. This was an entropy-increasing controlled spontaneous chemical endothermic reaction. In addition, the theoretical adsorption capacity was calculated to reach 466.2 mg/g. The mechanism of adsorption on PAO-SA was comprehensively analyzed by various characterizations, and the results indicated that both the amidoxime and carboxyl groups on PAO-SA complexed with U(VI). Under the presence of various metal ions, PAO-SA exhibited an optimal selective adsorption for uranium, with the selective partition coefficient (Kd) for U(VI) reaching 3.0 × 104 mL/g, and the ratio of selectivity coefficient of U to V reaching 1.98...

(With reference to the U to V ratio, vanadium is always recovered as a side product of these procedures.)

Have a nice Mother's day, if you are celebrating it with members of your family.

[Shipwack]

1. Just do that I understand...

The anti renewable (solar, wind, hydropower) remarks are from you, and not the paper? Or both?

[NNadir]

2. It's from me. I strongly oppose fossil fuel dependent, mass and land intensive...

...so called "renewable energy," since, unlike the modern members of the Sierra Club, who never see a wilderness they don't wish to convert to an industrial park for solar and wind, my environmental views are consistent with those of the Sierra Club's founder John Muir, who founded the Club in a failed attempt to prevent industrialization of a natural wilderness, the Hetch Hetchy valley in Yosemite National Park, now a hydroelectric plant.

Nuclear energy is the only form of energy I regard as clean and sustainable


I know this view is unpopular in some circles here, but I unrepentantly hold this view based on roughly 40 years of consideration ever since the Chornobyl reactor exploded, establishing nuclear's worst case.

Thanks for asking.

[Shipwack]

3. Interesting take. Thank you for the explanation. nt

[Envirogal]

4. Always railing against renewables

Never can answer the nuclear waste issue though. Wouldn’t have a problem putting a nuclear plant at the Hetch Hetchy to cool these monstrosities though, right?

Hetch Hetchy is a gorgeous miraculous place that Muir saved. He also saved the Grand Canyon from development. But there are all kinds of lands and waters that were not saved from mining and other infrastructure projects. So your argument using the Trojan Horse of Muir before nuclear energy was invented, is a Stretch Stretchy.

Solar rooftops do not disrupt the wilderness. And using John Muir as an example is a bit much given how much of our natural world, including the rivers to build behemoth concrete nuclear plants, that Muir would most likely also oppose. Or the delicate desert ecosystems to store their waste.

Every energy tech has pros and cons—all have an impact, especially trying to satisfy the needs of a growing 8.3 BILLION population.

I’m still waiting for that Chernobyl- like fallout from rooftop solar panels to where the land the size of Rhode Island will not be habitable for thousands of years.

[eppur_se_muova]

5. Whoa, what's with the isotope ratios in that table ? U-234 more abundant than U-238 or 235 ???

Is there something at the bottom of the table that added, say, x 10-5 before it got cut off ?

Please don't tell me they used AI to "help" construct that table.

[NNadir]

6. I didn't notice that. Good catch. There may be a power of 10 with a negative exponent excluded. I'll check...

the full text of the paper, which is from 2000, so it's not AI, to see what's going on. Probably a misprint. I may not have time until I return from a business trip to a conference, so if I forget, remind me. (I'm writing during a brief sleep interruption.)

There is some isotope fractionation - obviously not on a scale to justify these numbers - in the oceans, because the ²³⁴Th, (t_1/2 = 24.1 days) is completely insoluble in water, as are U(IV) compounds. If this were not true, thorium was not insoluble, thorium might be as sustainable as uranium is. The latter is the reason that there were no reactors like the OKlo natural reactors until oxygen appeared in Earth's atmosphere. Many people believe - they're wrong - that thorium is more sustainable than uranium. There is, however, no water driven geochemical thorium cycle, although terrestrial thorium is more available than terrestrial uranium.

In general, in rock, the secular equilibrium between sup]234U/sup]238U is on the order of 10^-6. Displacement from secular equilibrium can be utilized in recording the geological history of a uranium source.

There are actually a lot of these riverine uranium content tables in a lot of papers, but I had this one in a file format that was convenient to post.

[NNadir]

7. As I indicated last night in post #6, the ratio is apparently a ratio of ratios, displacement from secular equilibrium.

From the full text of the paper:

The reproducibility and the reliability of the U isotopic analyses were tested by periodic determination of the HU1Ustandard supposed to be at secular equilibrium, i.e., (234U/238U) 51.

It would have been better if they'd listed at such in the table.

The value at secular equilibrium is simply the ratio of the decay constants, which is simply the ratio of the half-lives, 5.50 X 10^-5.

A discussion of displacement from secular equilibrium in seawater and other matrices is found in this open source paper: Hsun-Ming Hu et al. Sub-epsilon natural 234U/238U measurements refine the 234U half-life and U-Th geochronology. Sci. Adv.11,eadu8117(2025). The table therein is labeled better.