High-efficiency removal of imidacloprid from wastewater by heterogeneous electro-Fenton process using MnFe2O4/g-C3N4 catalyst in a wide range of pH

Abstract

MnFe₂O₄/g-C₃N₄ composites were prepared for the high-efficiency removal of Imidacloprid (IMD) in wastewater via Heterogeneous Electro-Fenton (HEF) process. The prepared catalysts were characterized by XRD, FTIR, Raman, N₂ adsorption–desorption analysis, SEM-EDS, and XPS, which proved that the MnFe₂O₄ was successfully combined with g-C₃N₄. Moreover, IMD removal by the HEF process using an electrochemical cell was carried out to examine the catalytic performance of the MnFe₂O₄/g-C₃N₄. 99.7 % of IMD was decomposed after 60 min of electrolysis under the optimal conditions: the ratio MnFe₂O₄/g-C₃N₄ was 1:2, the dose of (1:2) MnFe₂O₄/g-C₃N₄ was 0.3 g L⁻¹, the current density was 10 mA cm⁻² and the initial pH was 5.5 (natural pH). These results confirmed the excellent removal performance of the system at the lowest Energy Consumption (EC) of 0.107 kWh g⁻¹. Prolonged treatment time of 3 h achieved 87.6 % TOC removal. The HEF process demonstrated an improved Mineralization Current Efficiency (MCE) of 14.5 % and a reduced EC of 0.84 kWh g⁻¹ TOC. Quenching experiments exhibited the hydroxyl radicals (•OH) as the primary active species for IMD degradation. Moreover, the HEF with MnFe₂O₄/g-C₃N₄ showed excellent catalytic effectiveness in different water matrices, reaching 84.5 % IMD removal in real wastewater after 60 min. This study evaluates the recyclability and the stability of (1:2) MnFe₂O₄/g-C₃N₄ catalyst during 5 cycles, which was confirmed by various characterization analyses of the used catalyst such as XRD, FTIR and XPS measurements.