Efficient degradation of imidacloprid in water through iron activated sodium persulfate

Abstract

The study focuses on the degradation of imidacloprid (IMI) through persulfate (PS) oxidation. The performance of different iron activators like magnetic biochar (MBC), nanoscale ferrous-ferric oxide (nFe3O4) and nanoscale zero-valent iron (nZVI) for PS activation was investigated by their application to sodium persulfate (SPS). The efficient degradation was achieved by nZVI/SPS system. The effects of different parameters like dosage of nZVI, initial concentrations of PS and IMI, pH and temperature of reaction solution, and the water matrix were investigated. Degradation of IMI was affected by initial pH. More than 80% of 30 ppm IMI, degraded within 20 min and 10 min respectively over pH 7.0 and 3.0. The mechanism of degradation was elucidated by electron paramagnetic resonance (EPR) and free-radical quenching analyses. EPR analysis showed that application of nZVI to SPS resulted in enhanced generation of sulfate (SO4−) and hydroxyl (OH) radicals, which were responsible for degradation. However, free-radical quenching analysis showed that addition of tert-butyl alcohol to nZVI/SPS system resulted more decreased degradation, which suggested that IMI was principally degraded by OH. Moreover, degradation was also supported by superoxide radicals (O2−). Finally, the applicability of nZVI/SPS system was investigated by carrying out experiments for degradation in different water matrices. The present study suggests that nZVI/SPS system is an efficient technique to control IMI-caused water pollution.