Comparative study on the degradation of cephalexin by four electrochemical advanced oxidation processes: Evolution of oxidation intermediates and antimicrobial activity

Made available in DSpace on 2019-10-04T12:38:44Z (GMT). No. of bitstreams: 0 Previous issue date: 2019-09-15 Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) The degradation of the beta-lactam antibiotic cephalexin (CEX) was carried out by the following electrochemical advanced oxidation processes (EAOPs): anodic oxidation (AO), Fered-Fenton (EF-Fered), photoassisted anodic oxidation (PAO), and photoassisted Fered-Fenton (PEF-Fered). All experiments were done in a flow reactor incorporating a boron-doped diamond anode, at a low current density; for the PAO and PEF-Fered processes, the solution was irradiated with UVA light. The initial removal of CEX was attained by all EAOPs, but it was much faster by the Fenton-based processes, which thus presented higher initial rates of TOC removal. However, the coupling of the electrolytic and UVA photolytic processes enhanced the mineralization process; as a consequence, significantly greater TOC removals were attained by the PEF-Fered and PAO processes. From the initial oxidation intermediates detected by LC-MS/MS for the PEF-Fered and AO processes, it could be concluded that addition reactions involving the electrophilic HO center dot radicals occurred preferentially in the beta-lactam ring; however, due to the higher availability of HO center dot radicals, the Fenton-based process led to a faster rupture of that ring. Thus, the antibacterial activity of the treated CEX solution against Escherichia coli was completely terminated within less than 1 h of treatment by the PEF-Fered process, compared to 8 h by the AO process. The PEF-Fered and PAO processes yielded enhanced degradation performances despite mere use of UVA light. Univ Fed Sao Carlos, Dept Quim, CP 676, BR-13560970 Sao Carlos, SP, Brazil Univ Estadual Paulista, Dept Quim Analit, Inst Quim Araraquara, BR-14800900 Araraquara, SP, Brazil Univ Fed Sao Carlos, Dept Engn Quim, CP 676, BR-13560970 Sao Carlos, SP, Brazil Univ Estadual Paulista, Dept Quim Analit, Inst Quim Araraquara, BR-14800900 Araraquara, SP, Brazil CNPq: 152361/2016-2 CNPq: 311970/2017-6 CAPES: AUXPE 499/2013 FAPESP: 2004/08572-4 FAPESP: 2018/10805-0