Optimizing Polyacrylic Acid-Based Copolymer Hydrogel for Enhanced Uranyl Ion Adsorption: Effects of Drying Conditions, Crosslinker Content, and Copolymer Composition

The increasing concern over radioactive waste management necessitates the development of effective materials for the adsorption of hazardous ions, particularly uranyl ions (UO₂²⁺), prevalent in nuclear wastewater. This study investigates polyacrylic acid-based hydrogels as a potential superabsorbent for uranyl ion capture, focusing on the influence of drying conditions, crosslinker content, and the choice of secondary monomers on the hydrogel's performance. Incorporating a second monomer enhances the structural diversity and functionalization of the hydrogels, leading to improved adsorption capabilities. Initially, the impact of two drying methods (freeze-drying and oven-drying) on the structure and adsorption capabilities of the hydrogels is examined. Additionally, the role of crosslinker concentration in modulating the hydrogels' mechanical strength and swelling behavior is explored. A molar ratio of 1% initiator to monomer concentration is employed to fabricate a copolymer structure containing both acrylic acid and acrylamide, which is expected to enhance the capacity for uranyl ion adsorption. The effects of varying pH levels on adsorption capacity are systematically assessed at a controlled temperature of 40 °C in a solution containing 240 mg/L uranyl ions, with initial findings indicating a maximum adsorption capacity of 333.8 mg/g at pH 5. Given that nuclear wastewater typically exhibits acidic conditions, the selectivity and competitive adsorption behavior of the hydrogel in solutions with a pH of 2 are also investigated. The results demonstrate that the developed superabsorbent exhibits promising performance in multi-ion environments, highlighting its potential application in environmental remediation strategies aimed at mitigating the impacts of nuclear waste. This research contributes to advancing material science in the context of sustainable solutions for hazardous waste management.