More than 1000× uranium exists in the oceans than exists in terrestrial ores. With nuclear power generation expected to increase over the coming decades, access to this unconventional reserve is a matter of energy security. With origins in the mid-1950s, materials have been developed for the selective recovery of seawater uranium for more than six decades, with a renewed interest in particular since 2010. This review comprehensively surveys materials developed from 2000–2016 for recovery of seawater uranium, in particular including recent developments in inorganic materials; polymer adsorbents and related research pertaining to amidoxime; and nanostructured materials such as metal–organic frameworks, porous-organic polymers, and mesoporous carbons. Challenges of performing reliable and reproducible uranium adsorption studies are also discussed, as well as the standardization of parameters necessary to ensure valid comparisons between different adsorbents.

Materials for the Recovery of Uranium from Seawater

Montmorillonite-supported magnetite nanoparticles for the removal of hexavalent chromium [Cr(VI)] from aqueous solutions

Herein, we present a survey of the literature covering the development of molecular imprinting science and technology over the years 2004-2011. In total, 3779 references to the original papers, rev ...

Molecular imprinting science and technology: a survey of the literature for the years 2004-2011.

The recovery of uranium (U) from seawater has been investigated for over six decades in efforts to secure uranium sources for future energy production. The majority of the research activities have focused on inorganic materials, chelating polymers, and nanomaterials. Previous studies of uranium adsorption from aqueous solutions, mainly seawater, are reviewed here with a focus on various adsorbent materials, adsorption parameters, adsorption characterization, and marine studies. Continuous progress has been made over several decades, with adsorbent loadings approaching 3.2 mg U/g adsorbent in equilibrium with seawater. Further research is needed to improve first, the viability including improved capacity, selectivity, and kinetics, and second, the sorbent regeneration for multicycle use. An overview of the status of the uranium adsorption technology is provided and future research needs to make this technology commercially competitive are discussed.

Recovery of Uranium from Seawater: A Review of Current Status and Future Research Needs

Metal ion-imprinted polymers : Novel materials for selective recognition of inorganics

Major quantities of uranium find use as nuclear fuel in nuclear power reactors. In view of the extreme toxicity of uranium and consequent stringent limits fixed by WHO and various national governments, it is essential to remove uranium from nuclear power reactor effluents before discharge into environment. Ion imprinted polymer (IIP) materials have traditionally been used for the recovery of uranium from dilute aqueous solutions prior to detection or from seawater. We now describe the use of IIP materials for selective removal of uranium from a typical synthetic nuclear power reactor effluent. The IIP materials were prepared for uranyl ion (imprint ion) by forming binary salicylaldoxime (SALO) or 4-vinylpyridine (VP) or ternary SALO-VP complexes in 2-methoxyethanol (porogen) and copolymerizing in the presence of styrene (monomer), divinylbenzene (cross-linking monomer), and 2,2'-azobisisobutyronitrile (initiator). The resulting materials were then ground and sieved to obtain unleached polymer particles. Leached IIP particles were obtained by leaching the imprint ions with 6.0 M HCl. Control polymer particles were also prepared analogously without the imprint ion. The IIP particles obtained with ternary complex alone gave quantitative removal of uranyl ion in the pH range 3.5-5.0 with as low as 0.08 g. The retention capacity of uranyl IIP particles was found to be 98.50 mg/g of polymer. The present study successfully demonstrates the feasibility of removing uranyl ions selectively in the range 5 microg - 300 mg present in 500 mL of synthetic nuclear power reactor effluent containing a host of other inorganic species.

Removal of Toxic Uranium from Synthetic Nuclear Power Reactor Effluents Using Uranyl Ion Imprinted Polymer Particles

Investigation of the role of chelating ligand in the synthesis of ion-imprinted polymeric resins on the selective enrichment of uranium(VI).

The presence of chromium in iron oxides such as hematite and magnetite hinders their dissolution in reductive-complexing formulations The oxidative pretreatment (op) of such oxides, which results in Cr leaching from the oxide, has improved the dissolution when subsequently treated with a reductive-complexing formulation In this study, various oxidative reagents such as Mn(III)−L and permanganate (acidic/alkaline) reagents were compared for their effectiveness of Cr2O3 dissolution Because the permanganate reagents were effective for the op of Cr-substituted hematites/magnetites, the relative effectiveness of permanganate reagents can be shown as HMnO4 ≈ NP > AP The op with permanganate reagents was found to be marginally advantageous for the reductive-complexing dissolution of Cr-substituted hematites (csh) and magentites (csm) in V(II) formulations such as vanadium(II) picolinate, vanadium(II) ethylenediaminetetraacetate, and vanadium(II) citrate Nevertheless, the amount of chromium released during t

Effect of Oxidative Pretreatment for the Dissolution of Cr-Substituted Hematites/Magnetites

Dissolution behavior of synthetic Mg/Zn-ferrite corrosion products in EDTA and NTA based formulations

The dissolution rate coefficients of Cr-substituted (0-20 at.% Cr) iron oxides viz. hematite and magnetite were determined by using an inverse cubic rate (ICR) law applicable for spherical particles as well as by a general kinetic equation (GKE) applicable for polydispersed particles. An attempt is made to compare both the treatments for different kinds of dissolution profiles obtained by employing oxides with narrow particle size distribution in V(II)-EDTA and citric acid-EDTA-ascorbic acid formulations at 353±5K. The dissolution profiles could be classified into three types based on the nature of oxide and formulations. It is observed that both ICR and GKE treat the dissolution course as a function of decrease in fraction of undissolved mass, m/m0. The dissolution rate coefficients determined by ICR and GKE have shown the similar trend of decrease with increasing Cr content of the oxides and was ascribed to lattice stabilization.



Les coefficients de vitesse de dissolution des oxydes de fer substitues par du Cr (0-20 % de Cr), a savoir l'hematite et la magnetite, ont ete determines a l'aide de la loi de « vitesse cubique inverse » (ICR) applicable aux particules spheriques ainsi que d'une « equation cinetique generale » (GKE) applicable aux particules polydispersees. On tente de comparer ces deux approches pour differentes sortes de profils de dissolution obtenus avec des oxydes a distribution de tailles de particules etroite dans les formulations de V(II)-EDTA et d'acide citrique-EDTA-acide ascorbique a 353±5K. Les profils de dissolution pourraient se classer en trois categories selon la nature de l'oxyde et les formulations. On observe que les methodes ICR et GKE traitent le processus de dissolution comme une fonction de la diminution de la fraction de matiere non dissoute, m/m0. Les coefficients de vitesse de dissolution determines par l'ICR et la GKE montrent la meme tendance a la diminution avec l'augmentation de la teneur en Cr des oxydes, ce qui est impute a une stabilisation du reseau.

G. Venkateswaran

Papers

Removal of Toxic Uranium from Synthetic Nuclear Power Reactor Effluents Using Uranyl Ion Imprinted Polymer Particles

Investigation of the role of chelating ligand in the synthesis of ion-imprinted polymeric resins on the selective enrichment of uranium(VI).

Effect of Oxidative Pretreatment for the Dissolution of Cr-Substituted Hematites/Magnetites

Dissolution behavior of synthetic Mg/Zn-ferrite corrosion products in EDTA and NTA based formulations

Preparation and Kinetic Considerations for the Dissolution of Cr‐substituted Iron Oxides in Reductive‐complexing Formulations