Recovery of Silver from Wastewater Using a New Magnetic Photocatalytic Ion-Imprinted Polymer

A novel magnetic, photocatalytic, and Ag(I)-imprinted thiol-functionalized polymer (Fe3O4@SiO2@TiO2-IIP) was prepared as functionalized IIP for selective removal and recycling of Ag+ ions from actual wastewater. The material used in this study exhibited a promising silver saturation adsorption capacity of 35.475 mg/g under the optimum pH of 6 within 80 min. The specific Ag+ ion adsorption property of the material was excellently offered by the Ag(I)-imprinted thiolfunctionalized polymer. The selectivity separation factors for Ag with respect to Li+, Co2+ , Cu2+, and Ni2+ are 10.626, 27.829, 13.276, and 68.109, respectively. In the presence of TiO2 and methanol used as the sacrificial agent (methanol/water 15:40), the adsorbed Ag(I) can be reduced to Ag(0) and then separated from the imprinted polymers after the ultrasound. The reduction rate is 0.00566 min(-1) based on a pseudo-first-order kinetic model. The retained adsorption capacity of the Ag-IIP was 68.51% after one round of photocatalysis and ultrasound, which was closed to three rounds of acid elution. We also conducted an experiment with real wastewater and validated the great potential of Fe3O4@SiO2@TiO2-IIP in advanced wastewater treatment. The results showed that 1.3 mg of silver was recovered from 100 mL of 50 mg/L AgNO3 solution with 0.1 g of the IIP. Accordingly, the functionalized IIP constructed and applied in this study demonstrated (a) the promising selective adsorption capacity of Ag, (b) the efficient photoreduction potential of Ag, (c) gentle and ecofriendly regeneration conditions, and (d) excellent magnetic separation ability, and it has great potential in future practical wastewater treatment.