Photocatalytic degradation of persistent organic pollutants by Co-Cl bond reinforced CoAl-LDH/Bi12O17Cl2 photocatalyst: mechanism and application prospect evaluation

Abstract

The widespread distribution of persistent organic pollutants (POPs) in natural waters has aroused global concern due to their potential threat to the aquatic environment. Photocatalysis represents a promising mean to remediate polluted waters with the simple assistance of solar energy. Herein, we fabricated a Co-Cl bond reinforced CoAl-LDH/Bi₁₂O₁₇Cl₂ heterogeneous photocatalyst to investigate the feasibility of photocatalysis to treat POPs-polluted water under environmental conditions. The optimum CoAl-LDH/Bi₁₂O₁₇Cl₂ (5-LB) composite photocatalyst exhibited excellent photocatalytic performance, which could degrade 92.47 % of ciprofloxacin (CIP) and 95 % of bisphenol A (BPA) with 2h of actual solar light irradiation in Changsha, China (N 28.12 °, E 112.59 °). In view of the synergistic influence of water constituents, various water matrices greatly affected the degradation rate of CIP (BPA), with the degradation efficiency of 82.17% (84.37%) in tap water, 69.67% (71.63%) in wastewater effluent, and 44.07% (67.7%) in wastewater inflow. The results of electron spin resonance, and chemical trapping experiment, HPLC-MS and density functional theory calculation reflected that the degradation of CIP was mainly attributed to h⁺ and ¹O₂ attacking the active atoms of CIP molecule with high Fukui index. Furthermore, the non-toxicity of both 5-LB photocatalyst and treated CIP solution was proved by E.coli and B.subtilis cultivation, which further demonstrated the feasibility of the 5-LB to treat POPs in real water under irradiation of solar light.

Keywords: Actual sunlight; Bi(12)O(17)Cl(2); Ciprofloxacin degradation; CoAl-LDH; Photocatalysis; Toxicity assessment.