Abstract
The necessity to recover uranium from dilute solutions (for environmental/safety and resource management) is driving research towards developing new sorbents. This study focuses on the enhancement of U(VI) sorption properties of composite algal/Polyethylenimine beads through the quaternization of the support (by reaction with glycidyltrimethylammonium chloride). The sorbent is fully characterized by FTIR, XPS for confirming the contribution of protonated amine and quaternary ammonium groups on U(VI) binding (with possible contribution of hydroxyl and carboxyl groups, depending on the pH). The sorption properties are investigated in batch with reference to pH effect (optimum value: pH 4), uptake kinetics (equilibrium: 40 min) and sorption isotherms (maximum sorption capacity: 0.86 mmol U g−1). Metal desorption (with 0.5 M NaCl/0.5 M HCl) is highly efficient and the sorbent can be reused for five cycles with limited decrease in performance. The sorbent is successfully applied to the selective recovery of U(VI) from acidic leachate of uranium ore, after pre-treatment (cementation of copper, precipitation of rare earth elements with oxalate, and precipitation of iron). A pure yellow cake is obtained after precipitation of the eluate.
Highlights
The demand of uranium for nuclear applications makes the extraction of this metal a strategic issue in terms of both economic and strategic aspects
The signals associated with Ca 2p (i.e., Ca 2p3/2 and Ca 2p1/2) are significantly affected by metal sorption both in terms of Binding energies (BEs), full width at half maximum (FWHM) values and atomic fractions (a) anionic exchange between Cl ions on quaternary ammonium groups and anionic uranyl species [64], (b) ion-exchange with Ca2+ bound to carboxylate groups, protons on the hydroxyl and amine groups and cationic UO22+, and/or
These complementary treatments reduce the residual concentration of copper to 3 mg Cu L−1, while the concentration of rare earth elements (REEs) decreases to 5.3 mg L−1 (97.5% of REEs are removed after oxalate treatment)
Summary
The demand of uranium for nuclear applications makes the extraction of this metal a strategic issue in terms of both economic and strategic aspects. A new generation of porous material (Algal/Polyethyleneimine beads, APEI) was synthesized through the interaction of alginate and brown algae biomass with polyethylenimine (PEI) [37,38,39] These materials may combine chelation and ion-exchange properties, depending on the pH, and the metal ion (including its speciation). APEI was quaternized by grafting glycidyltrimethylammonium moieties on the composite beads (Q-APEI) This sorbent was efficiently tested for the sorption of Sc(III), especially for the recovery of the metal from complex effluent issued from the treatment of red mud [41]. The properties of these materials have been fully characterized in terms of composition (elemental analysis, FTIR, and XPS), textural properties and thermogravimetric analysis. A series of pre-treatments is used for separating the metals before using Q-APEI for the recovery of uranyl ions as a yellow cake
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