Fabrication of Bi/BiPMo12O40 composite with enhanced photocatalytic activities for Cr(VI) reduction and tetracycline degradation

Applying photocatalytic technology to remove pollutants in wastewater represents an ideal pathway to solve the crisis of environmental contamination. However, It's always a great challenge to design efficient, recyclable and multifunctional photocatalysts. Herein, the x wt% Bi/BiPMo12O40 (x = 0.5, 1.0, 2.0 and 3.0) composites were successfully constructed via a hydrothermal method, and characterized with a variety of technological methods. These composites displayed enhanced and persistent photocatalytic activity for removing various pollutants. Specifically, the 1.0% Bi/BiPMo12O40 exhibited optimal performance with the removal efficiencies of 89.33% (Cr(VI)), 77.5% (TC) and 97.5% (MO) under visible light (λ＞420 nm), respectively. Moreover, the influence factors including the Cr(VI) concentration, catalyst dosage, the pH of solution, water quality and inorganic anions, on Cr(VI) reduction were studied in detail. Meanwhile, the degradation products of TC were identified with HPLC-MS, and a feasible degradation pathway was established. The toxicity of intermediates was assessed through QSAR prediction. The outstanding catalytic activity could be attributed to the strong visible absorption, enhanced BET specific surface area and the promotion in separation of photoinduced carriers. Capturing experiments and ERS tests verified the main active substances for Cr reduction (·O2− and e−) and TC degradation (·O2−, ·OH and h+). Eventually, the reasonable photocatalytic mechanism was proposed. This work provides a rational strategy for designing and constructing of efficient and durable POMs-based catalysts for environmental modification.