Removal of low-concentration tetracycline from water by a two-step process of adsorption enrichment and photocatalytic regeneration

Developing a high-performance method that can effectively control pollution caused by low concentrations of antibiotics is urgently needed. Herein, a novel three-dimensional PPy/Zn3In2S6 nanoflower composites were prepared for the comprehensive treatment of low-concentration tetracycline (Tc) hydrochloride in wastewater based on the adsorption/photocatalysis of Zn3In2S6 and the conductivity of PPy. In this preparation method, adsorption enrichment and photocatalytic regeneration were conducted in two steps, eliminating the dilution and dispersion effects of aqueous solvents on photocatalytic species and antibiotics. Results showed that Zn3In2S6 could effectively adsorb 87.85% of Tc at pH of 4.5 and photocatalytically degrade Tc at pH of 10.5. Although the adsorption capacity of Zn3In2S6 was slightly reduced after being combined with PPy, its photocatalytic efficiency was substantially enhanced. Specifically, 0.5%PPy/Zn3In2S6 could degrade 99.92% of the surface-enriched Tc in 1 h and induce the regeneration of the adsorption sites. Furthermore, the adsorption capacity remained above 85% even after recycling PPy/Zn3In2S6 ten times. The photocatalytic degradation mechanism analysis revealed that the enrichment of Tc on 0.5%PPy/Zn3In2S6 negatively impacts the photocatalytic efficiency, while center dot O-2(-) and center dot OH radicals were the main oxidative species that played an important role in the photoregeneration process.

Automated summary

In this study, a novel three-dimensional PPy/Zn3In2S6 nanoflower composite was prepared for the comprehensive treatment of low-concentration tetracycline (Tc) hydrochloride in wastewater. The composite material showed high efficiency in both adsorption and photocatalytic degradation of Tc. The combination of PPy and Zn3In2S6 significantly enhanced the photocatalytic efficiency of the material.