Influence of electrolysis conditions on the treatment of herbicide bentazon using artificial UVA radiation and sunlight. Identification of oxidation products

JOURNAL OF ENVIRONMENTAL MANAGEMENT

卷:231

Article

Guelfi, Diego R. V.¹  Brillas, Enric²  Gozzi, Fabio¹  Machulek, Amilcar, Jr.¹  de Oliveira, Silvio C.¹  Sires, Ignasi² 

[1] Univ Fed Mato Grosso do Sul, Inst Quim INQUI, 549,Av Senador Filinto Muller 1555, BR-79070900 Campo Grande, MG, Brazil

[2] Univ Barcelona, Lab Electroquim Mat & Medi Ambient, Dept Quim Fis, Fac Quim, Marti & Franques 1-11, E-08028 Barcelona, Spain

关键词: Anodic oxidation;    Electro-Fenton;    Hydroxyl radical;    Pesticide;    Solar photoelectro-Fenton;   

DOI  :  10.1016/j.jenvman.2018.10.029

来源: Elsevier

【 摘 要 】

The main objective of this work is to demonstrate the viability of solar photoelectro-Fenton (SPEF) process to degrade pesticides in urban wastewater matrix, selecting the herbicide bentazon as a model molecule. In order to provide a correct assessment of the role of the different oxidants and catalysts involved, bentazon was comparatively treated by anodic oxidation with electrogenerated H2O2 (AO-H2O2), electro-Fenton (EF) and UVA-assisted EF (i.e., PEF) processes as well, either in sulfate or chloride media. Trials were made in a stirred tank reactor with an air-diffusion cathode and a boron-doped diamond (BDD), RuO2-based or Pt anode. In chlorinated matrices, the herbicide disappeared more rapidly using a RuO2-based anode because of the generated active chlorine. The best mineralization performance was always obtained using BDD due to its higher oxidation power, which allowed the complete destruction of refractory chloroderivatives. A concentration of 0.50 mM Fe2+ was found optimal to catalyze Fenton's reaction, largely enhancing the mineralization process under the action of center dot OH. Among photo-assisted treatments, sunlight was proven superior to a UVA lamp to promote the photolysis of intermediates, owing to its greater UV irradiance and contribution of visible photons, although PEF also allowed achieving a large mineralization. In all cases, bentazon decay obeyed a pseudo-first-order kinetics. SPEF treatment in urban wastewater using BDD at only 16.6 mA cm(-2) yielded 63.2% mineralization. A thorough, original reaction pathway for bentazon degradation is proposed, including seven non-chlorinated aromatics, sixteen chloroaromatics and two chloroaliphatics identified by GC-MS, most of them not previously reported in literature. Ion-exclusion HPLC allowed the detection of seven short-chain linear carboxylic acids.

【 授权许可】

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