Applicability of electrocoagulation process to the treatment of Ofloxacin and Chloramphenicol in aqueous media: Removal mechanism and antibacterial activity

Abstract

Antibiotics are emerging micropollutants, which can be harmful and toxic for the human health and biotic community. Nowadays, it is recognized that the conventional wastewater treatment is relatively ineffective for their removal. Effluents are then among the main sources of antibiotics' releasing into environment. As a promising treatment process, electrocoagulation (EC) has proven efficacy for the treatment of many refractory pharmaceuticals but remains little studied for antibiotics. In this study, EC was applied for the first time to remove ofloxacin (OFL) and chloramphenicol (CAP), widely dispersed antibiotics in the environment worldwide. Results revealed that EC with Al-electrodes is effective for OFL and CAP removal in aqueous solution. 72 % of OFL is removed for 40 min electrolysis time, and a maximum of 78 % is reached after 105 min. CAP needs more time to reach 78 % (180 min) but its removal continues over time. Based on UV–visible, HPLC and FTIR analyses, it was shown that OFL is mainly removed by adsorption on the electro-generated Al(OH)3 flocs whereas cathodic degradation is responsible for CAP reduction. OFL adsorption is mainly controlled by surface complexation mechanism involving the surface functional group AlOH and the deprotonated carboxylate groups in the anionic (OFL−) and zwitterion (OFL0) ofloxacin. The cathodic degradation of CAP generates four main by-products: the nitroso product (NOCl2), an aromatic amine product (AMCl2) and two dechlorinated AMCl2 products (AMCl and AM). The toxicity assays showed that EC process could eliminate the antibacterial activity of OFL and CAP.