Hierarchical surface ion-imprinted sodium alginate/silica composite spheres for selective adsorption Cu(II) from wastewater and subsequently being transformed into an efficient photocatalyst for reducing CO2 to methanol

The extensive use of copper leads to the generation of a large amount of copper-containing wastewater, which poses a serious threat to both biological health and the environment. Therefore, recovery and reutilization of Cu from wastewater is of great practical significance for humans. In this study, the novel hierarchically ionimprinted microsphere (H-Cu-IIP) and surface ion-imprinted microsphere (Cu-IIP) were successfully prepared from alginate/silica composite materials for the selective recovery of Cu(II). Both synthesized materials were characterized using various techniques including FT-IR, SEM, BET, TGA, and XPS, and their adsorption properties for Cu(II) were evaluated in terms of pH, adsorption kinetics, adsorption isotherm, selective adsorption, and stability. The results showed that H-Cu-IIP and Cu-IIP achieved excellent equilibrium adsorption capacities of 390.6 mg/g and 358.4 mg/g, respectively, with high selectivity and good stability, and could effectively remove Cu(II) even in actual water environments. The Langmuir model and pseudo-second-order equation can well describe adsorption isotherms and kinetics, respectively. In addition, the catalysts derived from the Cu(II)loaded adsorbents through simple calcination exhibits excellent catalytic efficiency for photocatalytic reduction of CO2. These findings suggest that the proposed method is a promising approach for the selective recovery and reuse of Cu(II) from wastewater, aligning with the principles of green and sustainable practices.