Synthesis of industrial waste-based geopolymer catalyst and its application in removing imidacloprid insecticide from water

Geopolymer granules containing fly ash as aluminosilicate materials and mill scale as a catalyst were applied for photocatalytic degradation of imidacloprid insecticide. The surface properties of the geopolymer catalyst were optimized by providing an optimum ratio of waste materials and pore-forming agents. The geopolymer catalyst yielded complete imidacloprid removals during batch experiments, with more than 80 % of its removals taking place after only 1 h of UV exposure. High photocatalytic activities were maintained over 10 repetitive cycles, exhibiting its longevity during which a gradual release of sediment with higher photocatalytic activities was observed, thus increasing its overall photocatalytic degradation rate of the geopolymer catalyst. • Fly ash and mill scale industrial waste are utilized for synthesis of geopolymer granules. • Surface morphology of geopolymer granules was optimized for photocatalytic reaction. • Complete removals of imidacloprid were achieved using geopolymer catalyst. • High photocatalytic degradation rates were maintained over 10 repetitive operating cycles. • Sediment released from geopolymer also served as reactive sites for photocatalytic reaction.