Fabrication of a Sm2O3/In2S3 photocatalyst for boosting ciprofloxacin oxidation and the Cr(vi) reduction: process parameters and degradation mechanism

Abstract

A series of Sm₂O₃/xIn₂S₃ heterostructures (where x = 5, 10, 15, and 20 wt%) were synthesized and successfully employed as photocatalysts in the degradation of ciprofloxacin (CIP) and in the photocatalytic reduction of hexavalent chromium (Cr(VI)). This is the first report that investigates the impact of various operating conditions, including catalyst loading, substrate dosage, and co-existing anions (Cl⁻, SO₄²⁻, PO₄³⁻, HPO₄²⁻, CO₃²⁻, and HCO₃⁻) on the photocatalytic degradation of CIP as well as Cr(VI) reduction using Sm₂O₃/15 wt% In₂S₃ photocatalysts. Interestingly, the Sm₂O₃/15 wt% In₂S₃ photocatalyst demonstrated CIP degradation efficiency of 99.4% and 96.1% for Cr(VI) photoreduction with 50 mg L⁻¹ catalyst loading at 55 and 50 min, respectively. Catalyst loading and CIP concentration as well as K₂Cr₂O₇ dosage remarkably govern the photocatalytic performances. Co-existing anions, such as Cl⁻, PO₄³⁻, HPO₄²⁻, CO₃²⁻, and HCO₃⁻, notably deteriorate the photocatalytic performances. The scavenger studies emphasized that ˙OH and photogenerated electrons played a key role in the degradation of CIP and reduction of Cr(VI) to Cr(III), respectively. Liquid chromatography-masss spectroscopy analysis shows that CIP degradation preferentially propagates via the active piperazine ring. Reusability and stability studies exhibited >90% Cr(VI) reduction and CIP degradation after the 5th cycle, affirming the remarkable photostability of the Sm₂O₃/15 wt% In₂S₃ nanocomposite with the potential for practical applications.