Emerging organic contaminants in wastewater: Understanding electrochemical reactors for triclosan and its by-products degradation. (May 2020)

• Record Type: Journal Article
• Authors: Magro, Cátia; Mateus, Eduardo P.; Paz-Garcia, Juan M.; Ribeiro, Alexandra B.
• Is Part Of: Chemosphere. Volume 247(2020)
• Publication Date: 2020-05
• Subjects: Emerging organic contaminants -- Triclosan -- By-products -- Electrochemical process -- Electrokinetics -- Electro-degradation; BDD Boron-doped diamond -- DCP 2, 4-dichlorophenol -- EBR Electrochemical Batch Reactor -- EFR Electrochemical Flow Reactor -- EOCs emerging organic contaminants -- MTCS methyl-triclosan -- MMO Mixed metal oxides -- TCP 2, 4, 6-trichlorophenol -- TCS triclosan; Pollution -- Periodicals; Pollution -- Physiological effect -- Periodicals; Environmental sciences -- Periodicals; Atmospheric chemistry -- Periodicals; 551.511
• DOI: 10.1016/j.chemosphere.2019.125758
• Languages: English
• ISSNs: 0045-6535

Abstract

Abstract: Degradation technologies applied to emerging organic contaminants from human activities are one of the major water challenges in the contamination legacy. Triclosan is an emerging contaminant, commonly used as antibacterial agent in personal care products. Triclosan is stable, lipophilic and it is proved to have ecotoxicologic effects in organics. This induces great concern since its elimination in wastewater treatment plants is not efficient and its by-products (e.g. methyl-triclosan, 2, 4-dichlorophenol or 2, 4, 6-trichlorophenol) are even more hazardous to several environmental compartments. This work provides understanding of two different electrochemical reactors for the degradation of triclosan and its derivative by-products in effluent. A batch reactor and a flow reactor (mimicking a secondary settling tank in a wastewater treatment plant) were tested with two different working anodes: Ti/MMO and Nb/BDD. The degradation efficiency and kinetics were evaluated to find the best combination of current density, electrodes and set-up design. For both reactors the best electrode combination was achieved with Ti/MMO as anode. The batch reactor at 7 mA/cm 2 during 4 h attained degradation rates below the detection limit for triclosan and 2, 4, 6-trichlorophenol and, 94% and 43% for 2, 4-dichlorophenol and methyl triclosan, respectively. The flow reactor obtained, in approximately 1 h, degradation efficiencies between 41% and 87% for the four contaminants. This study suggests an alternative technology for emerging organic contaminants degradation, since the combination of a low current density with the flow and matrix induced disturbance increases and speeds up the compounds' elimination in a real environmental matrix. Graphical abstract: Image 1 Highlights: Electrochemical degradation reactors evaluation for triclosan and its by-products. Batch and flow reactors tested with two different anodes: Ti/MMO & Nb/BDD. Electro-batch reactor degradation efficiencies from 43% - < detection limit in 4 h. Electro-batch reactor kinetics higher with Ti/MMO used as anode. Electro-flow reactor degradation efficiencies from 41 to 87% in 1 h.