Construction of Magnetic S-Doped CoWO₄ Composite for Efficient and Selective Recovery of Gold from Wastewater via Adsorption-Reduction Pathway

The design and synthesis of efficient adsorbents for the recovery of precious metals from secondary resources are of great environmental and economic significance. Herein, a magnetic sulfur-doped composite CoFe₂O₄@S-CoWO₄ (CF@S-CoWO₄) is developed through a hydrothermal synthesis method, which is used to selectively recover gold in aqueous media. Significantly, CF@S-CoWO₄ exhibits the best overall performance with gold ions adsorption capacity (Q_max) and distribution coefficient (K_d) are 1049 mg g^-1 and 4.4 x 10⁶) mL g^-1, respectively, which are much higher than those of other gold adsorption materials. The selectivity coefficients (K) toward other metal ions (Pd²⁺, Ca²⁺, Mg²⁺, Cd²⁺, Al³⁺, Li⁺, Ni⁺) are also higher, which suggests that CF@S-CoWO₄ had a preferential selectivity for Au³⁺ in coexisting ion solutions. Moreover, the antianion interference of the composite follows the order: SO₄^2- > PO₄^3- > NO₃^- > CO₃^2-, and it also shows very good reusability with adsorption efficiency at 81.78% after four repeated cycles. Based on characterizations and calculation, it is found that Au(III) mainly undergoes chelation and reduction reactions in the S sites in CF@S-CoWO₄, which indicates the important role of S sites. Hence the CF@S-CoWO₄ composite demonstrates a promising application for the recycling of gold ions from electronic wastewater. © 2023 The Authors. Small Structures published by Wiley-VCH GmbH