Efficient cephalexin degradation using active chlorine produced on ruthenium and iridium oxide anodes: Role of bath composition, analysis of degradation pathways and degradation extent

Lic A. Perea, Ricardo E. Palma-Goyes, Jorge Vazquez-Arenas, Issis Romero-Ibarra, Carlos Ostos, Ricardo A. Torres-Palma

Research output: Contribution to journalArticlepeer-review

15 Scopus citations

Abstract

© 2018 The elimination of cephalexin (CPX) using electro-generated Cl 2 -active on Ti/RuO 2 -IrO 2 anode was assessed in different effluents: deionized water (DW), municipal wastewater (MWW) and urine. Single Ti/RuO 2 and Ti/IrO 2 catalysts were prepared to compare their morphologies and electrochemical behavior against the binary DSA. XRD and profile refinement suggest that Ti/RuO 2 -IrO 2 forms a solid solution, where RuO 2 and IrO 2 growths are oriented by the TiO 2 substrate through substitution of Ir by Ru atoms within its rutile-type structure. SEM reveals mud-cracked structures with flat areas for all catalysts, while EDS analysis indicates atomic ratios in the range of the oxide stoichiometries in the nominal concentrations used during synthesis. A considerably higher CPX degradation is achieved in the presence of NaCl than in Na 2 SO 4 or Na 3 PO 4 media due to the active chlorine generation. A faster CPX degradation is reached when the current density is increased or the pH value is lowered. This last behavior may be ascribed to an acid-catalyzed reaction between HClO and CPX. Degradation rates of 22.5, 3.96, and 0.576 μmol L −1 min −1 were observed for DW, MWW and urine, respectively. The lower efficiency measured in these last two effluents was related to the presence of organic matter and urea in the matrix. A degradation pathway is proposed based on HPLC-DAD and HPLC-MS analysis, indicating the fast formation (5 min) of CPX-(S)-sulfoxide and CPX-(R)-sulfoxide, generated due the Cl 2 -active attack at the CPX thioether. Furthermore, antimicrobial activity elimination of the treated solution is reached once CPX, and the initial by-products are considerably eliminated. Finally, even if only 16% of initial TOC is removed, BOD 5 tests prove the ability of electro-generated Cl 2 -active to transform the antibiotic into biodegradable compounds. A similar strategy can be used for the abatement of other recalcitrant compounds contained in real water matrices such as urine and municipal wastewaters.
Original languageAmerican English
Pages (from-to)377-387
Number of pages338
JournalScience of the Total Environment
DOIs
StatePublished - 15 Jan 2019

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