The synergic persulfate-sodium dodecyl sulfate effect during the electro-oxidation of caffeine using active and non-active anodes

Author(s)

Escalona-Duran, Florymar ^[1] ; da Silva, Djalma Ribeiro ^[1] ; Martinez-Huitle, Carlos A. ^{[2, 1]} ; Villegas-Guzman, Paola ^{[1, 3]}

Affiliation

^[1] Univ Fed Rio Grande do Norte, Inst Chem, Environm & Appl Electrochem Lab, BR-59078970 Natal, RN - Brazil

^[2] UNESP, Inst Chem, Natl Inst Alternat Technol Detect Toxicol Evaluat, POB 355, BR-14800900 Araraquara, SP - Brazil

^[3] Fdn Univ Navarra UNINAVARRA, Ctr Invest UNINAVARRA CINA, Calle 10, 6-41 Primer Piso, Neiva, Huila - Colombia

• Document type: Journal article
• Source: Chemosphere; v. 253, AUG 2020.
• Web of Science Citations: 0

Abstract

It has previously been established during the elimination of organic matter that the addition of sodium dodecyl sulfate in solution is an important condition in the electrochemical oxidation approach that allows to increase the production of persulfate, enhancing the efficacy of the treatment. This outcome was observed when using the anodic oxidation with boron doped diamond (BDD), the extra production of persulfate was achieved after the SDS-sulfate released in solution and it reacts with hydroxyl radicals electrogenerated at BDD surface. However, this effect was not already tested by using active anodes. For this reason, the effect of sodium dodecyl sulfate (SDS) during the electrochemical treatment of caffeine was investigated by comparing non-active and active anodes performances. A significant decrease on the oxidation efficiency of caffeine was observed by using Ti/IrO2-Ta2O5 anode at high current density when SDS was added to the solution. Conversely, at BDD anode, the presence of SDS enhanced the degradation efficiency, depending on the applied current density. This behavior is mainly due to the degradation of SDS molecules, which allows to increase the amount of sulfate in solution, promoting the production of persulfate via the mechanism involving hydroxyl radicals when BDD is used. Meanwhile, no oxidation improvements were observed when Ti/IrO2-Ta2O5 anode was employed, limiting the caffeine oxidation. Results clearly showed that the surfactant concentration had little influence on the degradation efficiency, but this result is satisfactory for the BDD system, since it demonstrates that effluents with complex matrices containing surfactants could be effectively degraded using the electrooxidation technique. Degradation mechanisms were explained by electrochemical measurements (polarization curves) as well as the kinetic analysis. Costs and energy consumption were also evaluated. (C) 2020 Elsevier Ltd. All rights reserved. (AU)

• FAPESP's process: 14/50945-4 - INCT 2014: National Institute for Alternative Technologies of Detection, Toxicological Evaluation and Removal of Micropollutants and Radioactivies
• Grantee: Maria Valnice Boldrin
• Support Opportunities: Research Projects - Thematic Grants