Removal of the Insecticide Imidacloprid from Water in Commercial Formulation using Electro-Fenton and Photo-Electro-Fenton: Optimization of COD Removal through Response Surface Methodology RSM-CCD

Abstract

This study aims to investigate the removal efficiency of insecticide imidacloprid (IMD) from its commercial formulation using electro-Fenton (EF) and photo electro-Fenton (PEF) processes in an open undivided electrolytic cell (BDD/Carbon felt). Ferrous (Fe2+) was used as catalyst in sulfate medium (Na2SO4) for both processes and a UV-C lamp (7 W) was used in PEF as source of UV irradiation. The effect of various operating conditions on IMD and COD removal was studied based on the response surface methodology (RSM-CCD). Optimal conditions for achieving maximum removal of IMD and COD by EF have been determined as follows: 17.15 mA cm−2 of current density, 0.255 mM of [Fe2+], and an electrolysis time of 80 min and 120 min for IMD and COD removals, respectively. The PEF process has been identified as a more efficient process compared to EF. It achieved 98 % of IMD removal after 75 min and 97 % of COD removal after 4 h of electrolysis time, with a Mineralization Current Efficiency (MCE%) value of 28.87 % and an Energy Consumption (EC) value of 7.9 kWh kg−1 COD removed in 3 h. Furthermore, quenching experiments using methanol, 2-propanol, and tert‑butanol as scavengers indicated that the primary oxidizing agent responsible for IMD degradation is •OH/BDD(•OH).