Photocatalytic Degradation of Imidacloprid in Water Using TiO₂, ZnO and Modified TiO₂: Kinetics, Mineralization and Process Optimization
Keywords:
Imidacloprid, Photocatalytic degradation, TiO₂, ZnO, Modified TiO₂, HPLC-DAD, Mineralization, Reactive oxygen speciesAbstract
The present study investigated the photocatalytic degradation of imidacloprid in aqueous media using TiO₂, ZnO and modified TiO₂ as semiconductor photocatalysts. Photocatalytic experiments were carried out in a controlled batch reactor, and the effects of catalyst dosage, initial imidacloprid concentration, solution pH, light intensity, temperature and hydrogen peroxide dose were systematically evaluated. Residual imidacloprid was quantified by HPLC-DAD, while total organic carbon analysis was used to assess mineralization. The degradation kinetics were interpreted using an apparent pseudo-first-order model, and scavenger experiments were conducted to examine the contribution of hydroxyl radicals, superoxide-related species and photogenerated holes. Among the tested catalysts, modified TiO₂ showed the highest photocatalytic performance, achieving 97.62 ± 0.19% imidacloprid degradation after 120 min, with an apparent rate constant of 0.031 min⁻¹ and a half-life of 22.36 min. The most favourable responses were observed at approximately 1.00 g L⁻¹ catalyst loading, pH 7, 30 °C, full reference light intensity and 10 mM H₂O₂. TOC removal reached 77.74 ± 0.14% after 120 min, indicating that parent-compound degradation proceeded faster than complete mineralization. Scavenger studies suggested that hydroxyl radicals played a major role, while superoxide-related species and photogenerated holes also contributed. Modified TiO₂ retained approximately 90.6% of its initial activity after five reuse cycles. Overall, modified TiO₂ demonstrated promising potential for the photocatalytic removal of imidacloprid from aqueous systems.
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