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

A series of Sm2O3/xIn(2)S(3) 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.