Light-driven bio-decolorization of triphenylmethane dyes by a Clostridium thermocellum-CdS biohybrid

Widespread application of synthetic dyes could generate colored wastewaters causing a range of serious environmental problems. Due to the complex nature of effluents from textile industries, it is difficult to obtain satisfactory treatment of dyes-contaminated wastewater using one single method. Biohybrids coupling of photocatalysts and biocatalysts have great potential in environmental purification. However, how to select suitable organisms and enhance the hybrid's catalytic activities remain challenging. Here, a novel biohybrid system (Clostridium thermocellum-CdS), created for light-driven biodecolorization under thermophilic treatment by using non-photosynthetic microorganism C. thermocellum self-photosensitized with CdS nanoparticles was established. The biohybrids exhibited remarkable decolorization effects on triphenylmethane dyes. The highest decolorization rate was 0.206 min^-1. More importantly, enhanced catalytic activities of cadmium sulfide (CdS)-based biohybrids by controlling the particle sizes of semiconductors were demonstrated. Biohybrids systems (Clostridium thermocellum-CdS) through the self-precipitation of CdS with different particle sizes not only showed dramatic changes in the optical properties but also exhibited a very different decolorization rate. This work can not only further broaden targeted applications of CdS-based biohybrids but also demonstrate a promising route for improving biohybrids corresponding photocatalytic capabilities through in situ precipitation CdS with different particle sizes.