Comprehensive removal of various dyes by thiourea modified chitosan/ nano ZnS composite via enhanced photocatalysis: Performance and mechanism

Dyeing wastewater is a carcinogenic pollutant, which is widely known for its harmful effects on humans and marine organisms. In this study, a novel composite was prepared by blending thiourea modified chitosan with zinc sulfide nanoparticles (T-CS/ZnS) to comprehensively remove methyl orange (MO), rhodamine B (Rh B), and methylene blue (MB) effectively. Characterization results suggested that the synthesized composite has an irregular and rough surface that provided high specific surface area for adsorption process, while the strong optical response and low bandgap width contributed to the subsequent photocatalytic degradation of adsorbed dye molecules. Under optimum experimental conditions, the removal rates of MO, Rh B, and MB were 99.59 %, 99.49 %, and 91.04 %, respectively. Amino and hydroxyl groups provide electrons in photocatalytic reactions. The reaction process is consistent with the quasi-first-order kinetic model, and the material has good stability and regeneration potential. This study indicated that T-CS/ZnS composite is a highly effective material for the treatment of dyeing wastewaters.

Automated summary

A novel composite material (T-CS/ZnS) was prepared by blending thiourea modified chitosan with zinc sulfide nanoparticles, which effectively removed methyl orange, rhodamine B, and methylene blue dyes. The synthesized composite had an irregular and rough surface, providing a high specific surface area for adsorption, and displayed strong optical response and low bandgap width for subsequent photocatalytic degradation. Under optimized conditions, the removal rates of the dyes were high. Amino and hydroxyl groups played a role in the photocatalytic reactions, and the material showed good stability and regeneration potential. This study demonstrates the high efficiency of T-CS/ZnS composite for dyeing wastewater treatment.