Adsorptive Preconcentration of Uranium in Hydrogels from Seawater and Aqueous Solutions

Cross-linked hydrogels containing poly(ethylene glycol methacrylate phosphate) (EGMP), poly(2-acrylamido-2-methyl-1-propane sulfonate) (AMPS), poly(acrylamidoxime) (AO), and AO along with different acidic (acrylic acid (AA), methacrylic acid (MAA), AMPS, and EGMP) and basic (3-(acrylamido propyl) trimethylammonium chloride (APTAC)) comonomers were prepared by UV-initiated bulk polymerization. These hydrogels were characterized in terms of their chemical structure and U(VI)-uptake behavior from aqueous and seawater samples. Except AMPS hydrogel, all these hydrogels were found to sorb U(VI) quantitatively (approximate to 90%) from the seawater. The U(VI)-sorption kinetics in EGMP and AO+MAA (60:40) hydrogels were found to be faster than other hydrogels under seawater conditions. The presence of a strong acid (-SO3H) comonomer with AO retards the overall kinetics involve in the U(VI) sorption from seawater. It was also observed that the U(VI) sorption kinetics was high]), dependent on the composition of the acidic and AO groups in the hydrogel. The uptake of U(VI) from acidic solution in AO+MAA hydrogel was found to be dependent on the acidity of the feed solution, and there was no uptake of U(VI) in this hydrogel from solution containing 1 mol L-1 HNO3. Contrary to this, EGMP hydrogel could sorb the U(VI) from solution containing high concentration of HNO3. This indicated that EGMP hydrogel call also be used for U(VI) preconcentration from the nuclear waste. U(VI) complexed in EGMP hydrogel and AO+MAA could be desorbed by their equilibration with 0.5 mol L-1 Na2CO3 and 1 mol L-1 HCl/HNO3, respectively. The mechanism of sorption of U(VI) in the hydrogels was Studied to understand the factors that control the U(VI) sorption from seawater.