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/Zn 3 In 2 S 6 nanoflower composites were prepared for the comprehensive treatment of low-concentration tetracycline (Tc) hydrochloride in wastewater based on the adsorption/photocatalysis of Zn 3 In 2 S 6 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 Zn 3 In 2 S 6 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 Zn 3 In 2 S 6 was slightly reduced after being combined with PPy, its photocatalytic efficiency was substantially enhanced. Specifically, 0.5%PPy/Zn 3 In 2 S 6 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/Zn 3 In 2 S 6 ten times. The photocatalytic degradation mechanism analysis revealed that the enrichment of Tc on 0.5%PPy/Zn 3 In 2 S 6 negatively impacts the photocatalytic efficiency, while • O 2 − and •OH radicals were the main oxidative species that played an important role in the photoregeneration process. [Display omitted] • 3D PPy/Zn 3 In 2 S 6 nanoflower composite was prepared for treatment of low-concentration Tc. • A two-step process of adsorption enrichment and photocatalytic regeneration was proposed. • Proposed method can eliminate the dilution and dispersion effects of solution on Tc. • 3D PPy/Zn 3 In 2 S 6 nanoflowers can be used many times and maintain their treatment efficiency. [ABSTRACT FROM AUTHOR]