Selective removal of 90Sr by a novel IDA-chelating resin from contaminated groundwater

The preparation of cost-effective, environmentally friendly, and highly selective adsorbents is crucial for capturing 90Sr from radionuclide-contaminated wastewater due to its long half-life and chemical toxicity. In this study, a novel IDA-type chelating resin (PS-IDA) was synthesized by chloroacetylating polystyrene (PS) and introducing iminodiacetic acid (IDA) onto it. Batch adsorption experiments were conducted to investigate the adsorption of Sr2+ on PS-IDA, including pH, contact time, initial concentration of Sr2+, and competing ions. The results indicated that pH 10 was the optimal condition for maximum Sr2+ ion adsorption. According to isotherm and kinetic data, the adsorption was well-fitted to the Freundlich model and pseudo-second-order kinetic model. Notably, PS-IDA exhibited a high removal rate at pH 10, removing 98.0% and 99.6% of non-radioactive Sr2+ and 90Sr, respectively. In simulative groundwater, PS-IDA demonstrated remarkable selectivity for trace levels of 90Sr (90Sr : Na+: K+: Cs+: Mg2+ molar ratio = 1: 6.6 × 1015: 3.8 × 1014: 2.5 × 1014: 1.5 × 1013), indicating its potential for selective capture of 90Sr from contaminated groundwater. Furthermore, PS-IDA resin with a suitable diameter and improved mechanical strength can be used for large-scale remediation of 90Sr-contaminated wastewater by column chromatography method. Finally, the adsorption mechanism was explained based on experimental data and characterizations which included ion exchange between Sr2+ in the solution with H+ on the resin and then the formation of chelates between adsorbed Sr2+ and O, N atoms from IDA.