Degradation of imidacloprid by fluidized-bed Fenton process

Wastewater containing imidacloprid (IMI), a new and widely used insecticide, can harm human health and aquatic organisms. To remove IMI, this study applied a fluidized-bed Fenton process due to its low capital cost. The degradation of IMI was investigated in a bench-scale reactor with synthetic wastewater. The studied conditions included pH 2–5, 1.0–10.0 mM Fe²⁺, 1.0–15.0 mM H₂O₂, 1.0 mM IMI, 100–400% bed expansion, 100 g of SiO₂ and at 25 ^◦C. Under the conditions of 3 mM Fe²⁺, 5 mM H₂O₂, 400% bed expansion, and pH of 3.0, degradation efficiencies of 97%, 41%, and 12% for IMI, COD, and TOC, respectively, were obtained within 45 min of reaction period while total iron removal reached 10%. Increasing bed expansion up to 400% did not have a significant impact on IMI degradation; however, it slightly deteriorated the total iron removal performance due to a scouring effect. At 100% bed expansion, total iron removal increased to 22%. The apparent rate law for IMI degradation by the fluidized-bed Fenton reactor under the studied conditions can be expressed as follows: d[IMI]/dt (mM min⁻¹ ) = -0.2218[H₂O₂] ^0.1182[ Fe²⁺]^0.3717