Magnetic Lyogels for Uranium Recovery from Wet Phosphoric Acid

Abstract

The work introduces composite magnetic materials designed to capture uranium from wet-process phosphoric acid (WPA) containing 6 M H3PO4, 2% H2SO4, sodium fluoride, and metal salts of Fe(III) and Al(III). The materials include poly(vinyl chloride) (PVC) covalently modified with N,N-diethyldithiocarbamate (DEDTC) or O,O-diethyldithiophosphate (DEDTP) moieties by nucleophilic substitution of the >C–Cl bonds of PVC. To maintain the polymer processability, the maximum substitution degree was kept below 42%. The modified PVC formed stable organic gel (lyogel) materials with liquid uranium extractants such as di(2-ethylhexyl)phosphoric acid (DEHPA) or a liquid mixture of trialkylphosphine oxides, Cyanex 923. To impart the magnetic recoverability to the lyogels, iron nanoparticles (20–50 nm) coated by carbon for chemical stability were incorporated. The resulting magnetic lyogels contain variable contents of liquid extractants, maintain particle shape, exhibit very low leaching of the extractants, and are chemic...