Polyurethane sponge assisted recoverable photocatalyst for outdoor weak sunlight-driven efficient water purification

Abstract

Photocatalysis is an effective technology to address wastewater issue. However, the difficult recoverability of sample powders and poor degradation performance of catalysts under weak sunlight irradiation restrict the commercialization applications. In this work, the Bi2WO6/g-C3N4 heterojunction is synthesized by hydrothermal and calcination techniques, and a three-dimensional polyurethane sponge is introduced to assist the catalyst powder. On the one hand, weather variations produce less affection for Bi2WO6 sample, which exhibits the efficient photocatalytic activity driven by weak sunlight. The construction of Bi2WO6/g-C3N4 heterojunction speeds up separation and transfer of photogenerated carriers, further improving the catalytic performances of pristine Bi2WO6. Under cloudy (solar power density 21.93–52.97 mW/cm2) and overcast (solar power density 3.66–18.99 mW/cm2) weathers, tetracycline degradation efficiencies of Bi2WO6/g-C3N4 reach 64.66% and 55.19% after 150 min of sunlight irradiation, respectively. On the other hand, catalyst powder is tightly loaded onto the surface of polyurethane sponge via polyurethane waterproof coating, which is convenient for material recovery and reuse. After 4 cycles, tetracycline degradation efficiencies of Bi2WO6/g-C3N4 present no significant decrease, saving reaction cost and causing no secondary pollution to water environment. This work provides a promising candidate for large-scale commercialization applications of wastewater treatment.