Fabrication of environmentally sensitive amidoxime hydrogel for extraction of uranium (VI) from an aqueous solution

Abstract The main aim of this study is to evaluate the removal efficiency of U(VI) using an environmentally sensitive amidoxime hydrogel (AO-NIAMP). The sensitivity of the swelling behaviours to the temperature and pH of AO-NIAMP could promote the adsorption of uranium and facilitate the extraction out itself from solutions. Under the reaction pH of 6.0, and an initial U(VI) concentration o of 16.65 mg L-1,with 22.43 mg of AO-NIAMP, the maximum adsorption capacity was 36.3 mg g-1 as calculated by using response surface methodology (RSM). The adsorption process followed the pseudo-second-order and the Freundlich isotherm model. Moreover, AO-NIAMP showed a stable ability to remove U(VI) from a solution that contained multiple interfering metal ions. Based on spectroscopic analyses, the mechanisms of the removal of U(VI) by AO-NIAMP were the chelation of functional groups and electrostatic interactions. Additionally, the adsorption ability of sites on AO-NIAMP for UO22+ was calculated by density functional theory (DFT),which determined the following orders: oxime nitrogen > -C = O > oxime type O and N-(-C(NH2)=NOH) > oxime oxygen > -SO3H. AO-NIAMP could maintain a uranium adsorption rate of 82.5% after four adsorption (at 30 °C) - desorption (at 40 °C) cycles. By having good swelling properties triggered by external stimuli and the ability to remove uranium, AO-NIAMP has the potential to serve as a uranium extractor.