Superparamagnetic ZnFe₂O₄/ZnS nanocomposites with a highly recyclable for degradation of bisphenol A under visible-light

Superparamagnetic ZnFe₂O₄/ZnS core–shell sub-microspheres were fabricated via a two-step forming method for recyclable photocatalytic degradation of bisphenol A (BPA) driven by visible light. The ZnFe₂O₄/ZnS nanocomposites display much higher photocatalytic efficiency as compared to that of the individual ZnFe₂O₄, which could remove about 97.7% of BPA in 135 min. The enhancement of photocatalytic activity is mainly attributed to the synergy effect of the energy band gap between ZnFe₂O₄ and ZnS, resulting in the enhanced visible light absorbance and separation efficiency of photo-generated electron–hole pairs. Specifically, the ZnFe₂O₄/ZnS nanocomposites can retain their stable photocatalytic activity toward BPA photodegradation for six successive cycles of reaction with rate constants of 0.0281–0.0272 min⁻¹ under visible light irradiation. The highly recyclable and stable performance of ZnFe₂O₄/ZnS nanocomposites might benefit from its superparamagnetic, which nanocomposite could be rapidly separated from aqueous solution by an external magnetic field, and without agglomeration when magnetic field removed. Our work demonstrates a practical means for fabrication of superparamagnetic nanocomposite to improve the visible light photocatalytic activity and reusability of photocatalyst.