Insights into persulfate-activated photodegradation of tinidazole and photoreduction of hexavalent chromium through β-In2S3 anchored on Ag-doped fish scale-derived HAp composite quantum dots

Abstract

Herein, novel Ag/HAp/In2S3 composite quantum dots (QDs) were engineered to activate persulfate (PS) under visible light irradiation to photodegrade tinidazole (TNZ). An alkaline treatment was employed to extract hydroxyapatite (HAp) from fish scales, and a bioreduction method was used to dope HAp with Ag nanoparticles. Finally, In2S3 was grown over Ag/HAp via a facile solvothermal method. The formulated catalyst showed excellent catalytic photoactivity toward the photodegradation of TNZ and other emerging toxins with high efficiency through green and clean technology. The reaction conditions, determination of reactive species, the mechanisms, the effect of competing species, COD, and TOC removal were investigated and discussed. During 30 min of visible light irradiation, 0.24 g/L of Ag/HAp/In2S3 composite QDs degraded 96.32 ± 1.76% of 20 mg/L of TNZ at a rate constant of 0.1021 min−1 and showed a mineralization efficiency of 79.33%. The degradation intermediates were identified through HR-LCMS, and the effect of the Ag/HAp/In2S3/Vis@PS system on other pollutants and real water conditions was analyzed. Moreover, Cr(VI) photoreduction to Cr(III) was also enhanced with an efficiency of 83.63 ± 1.69% and a rate constant of 0.02648 min−1. The silver metal acted as an electron accumulator and enhanced the degradation and reduction process by increasing the electron-hole recombination time. This work elucidated the role of the metal sulfide catalyst in the activation of PS for the elimination of emerging pollutants for a cleaner environment in visible light exposure. The novel Ag/HAp/In2S3 composite QDs could prove to be a potential material for environmental remediation against various contaminants in the near future.