Engineering ZnCdS nanosheets with nanoscale zero-valent nickel for synergistic uranium(VI) capture and reduction

Developing highly efficient uranium removal adsorbents is crucial for environmental remediation purposes. In this study, a novel nanocomposite consisting of nano zero-valent nickel (nZVN) supported on layered ZnCdS nanosheets (nZVN-ZCS) was synthesized using an in situ growth approach. This distinct 0D-2D architecture effectively inhibits the agglomeration of nZVN nanoparticles and synergistically integrates U(VI) adsorption with enhanced reduction, driven by superior electron transfer capabilities. Batch experiments demonstrate exceptionally rapid adsorption kinetics, reaching equilibrium within 20 min, and conform to both the pseudo-second-order and Langmuir models. Notably, the optimal 0.03nZVN-ZCS sample exhibits unprecedented maximum adsorption capacities of 1670 mg/g at 298 K and 2977 mg/g at 318 K (pH 4.0), significantly exceeding the capacities reported for most adsorbents. Additionally, nZVN-ZCS demonstrates high U(VI) selectivity in the presence of coexisting ions and shows excellent potential for continuous treatment of large volumes in dynamic adsorption experiments. The adsorption mechanism, elucidated through techniques such as XPS, FT-IR, TEM, and DFT calculations, demonstrates that nZVN-ZCS facilitates the immobilization and reduction of U(VI) through the action of Ni⁰ and S^2-. These findings position the 0D-2D nZVN-ZCS nanocomposite as a highly efficient adsorbent, holding substantial promise for addressing challenges associated with uranium contamination.