(60d) Removal of Pesticide from Wastewater By Electrochemical Advanced Oxidation Processes

Most recently, the use of advanced oxidation processes (AOPs) on the treatment of biorefractory organic pollutants has shown great performance. AOPs include chemical, photo-assisted and electrochemical processes that permit the oxidation of those organics by the very strong (generated hydroxyl radical. This radical can non-selectively attack most of the organic pollutants, transforming them into CO₂ and inorganic ions. In particular, a great efforts were put on the use of electrochemical AOPs (EAOPs) fir treatment of different emerging contaminates due to their simple setups and handling, mild operation conditions and high efficiency.

The present work reports the electrochemical degradation of the pesticide advanced oxidation processes like anodic oxidation with electro-generated H₂O₂, electro-Fenton (EF) and UVA photo-electro-Fenton (PEF). A boron-doped diamond (BDD) anode was combined with an air-diffusion cathode to produce H₂O₂ and oxidize the pesticide. Degradation of pesticide was related to its, applied current density, and the concentration of fenton reagent. Complete pesticide removal and approximately 88% of organic matter oxidation was achieved by all methods at a constant current density (j) ≥120.0 mA cm^−2. Pesticide degradation kinetics as well as chemical oxygen demand removal rate were successfully modeled to pseudo first-order kinetic. Organic matter mineralization was found to be independent from pH within the range 3.0–9.0. Electro-Fenton and photo-electro-Fenton processes showed an optimum pH and ferric ion concentration of 3.0, 0.50 mM, respectively, and showed the highest pesticide removal under two consecutive pseudo-first-order kinetic stages. The obtained degradation efficiency was related to the fast reaction between the targeted pesticide and the generated hydroxyl radicals. In conclusion, PEF was observed to give the best treatment as a results of the decomposition of photoactive intermediates by UVA radiation. The pesticide degradation pathway was proposed based on the products identified by GC–MS and LC-MS/MS. Oxalic and oxamic acids were detected as final carboxylic acids by ion-exclusion HPLC.