Removal of imidacloprid in geopolymer granules coupled with low-intensity photocatalytic and chemical oxidation processes

In this study, TiO2-immobilized geopolymer granules (TiO2-GCs) were developed for the removal of imidacloprid from water. TiO2 nanoparticle immobilization into the geopolymer material helped increase its crystalline structure and refine geopolymer pores by filling up mesopores and macropores (10-100 nm) in the porous geopolymer materials resulting in its denser structure. The maximum TiO2 content for the formation of geopolymer having good structural properties was 14 wt%. Then, the removals of imidacloprid from water through adsorption and photocatalytic processes in the TiO2-GCs were evaluated. The imidacloprid adsorption efficiencies varied between 10.7 and 11.1 % with the increase in TiO2 contents not influencing the imidacloprid adsorption on the TiO2-GCs. After UV irradiation, a maximum removal efficiency of 96.85 % of gradually absorbed imidacloprid on TiO2-GCs was achieved at 14 wt% TiO2 content. The results demonstrated that photocatalytic degradation was the main responsible mechanism for imidacloprid removal. The addition of H2O2 (10-20 mM) increased the imidacloprid removal rates in TiO2-GCs by 30-60 %.