Magnetically Recoverable NiFe ₂ O ₄ /ZnIn ₂ S ₄ for Efficient Visible-Light-Driven Photocatalytic Degradation of Xanthates

A magnetic photocatalyst, composed of nickel ferrite (NiFe2O4, NFO) and zinc indium sulfide (ZnIn2S4, ZIS), and denoted as NFO/ZIS, was successfully synthesized via a hydrothermal method. The structural, morphological, optical, and electronic properties of the composite were systematically characterized using multiple instruments. The 10 wt % NFO/ZIS composite behaved best in the photocatalytic degradation of xanthate. It achieved xanthate degradation efficiency of 80.41% at a rate constant of 0.01191 min–1 under visible-light irradiation, substantially outweighing the pristine NFO and ZIS. The enhanced performance was attributed to improved visible-light absorption, reduced charge transfer resistance, and more efficient separation of photogenerated charge carriers. Active-species trapping experiments and ESR results confirmed that superoxide radicals (O2·–) played a dominant role in the photocatalytic degradation. Density functional theory (DFT) calculations and electronic structure analysis further validated the interfacial charge transfer from ZIS to NFO. Moreover, cyclic tests demonstrated that the composite had excellent stability, magnetic recoverability (89.00%), and reusability, maintaining over 98% of its initial activity after five cycles. This work expands the application of NFO/ZIS photocatalysts to the challenging degradation of xanthates and provides a promising strategy for developing magnetically recyclable photocatalysts to treat mineral processing wastewater.