Effective removal of pesticide imidacloprid from water using TiC@TiO2 core-shell photocatalyst: Kinetics and degradation mechanisms

Pesticide contamination of water resources poses significant environmental and public health risks. This study presents a novel application of a visible light-activated titanium carbide core — titanium dioxide shell (TiC@TiO₂) nano-photocatalyst for the degradation of the neonicotinoid pesticide imidacloprid, evaluated against the benchmark Degussa P25 TiO₂ under both UV-C and simulated sunlight irradiation. The TiC@TiO₂ core-shell architecture enables visible light absorption through a narrowed effective band gap (2.93 eV vs. 3.25 eV for P25 TiO₂). Degradation kinetics followed the Langmuir-Hinshelwood model at varying initial concentrations (50–600 mg/L), transitioning to pseudo-first-order behavior as the reaction progressed. Under UV-C irradiation, TiC@TiO₂ achieved 83.5% imidacloprid degradation within 90 minutes (k app = 0.0135 min⁻¹), significantly outperforming P25 TiO₂ (70.0%, k app = 0.0081 min⁻¹). Under simulated sunlight, TiC@TiO₂ achieved 64.7% degradation (k app = 0.0077 min⁻¹), a result not significantly different from P25 performance under UV-C irradiation (k app = 0.0081 min⁻¹, p > 0.05). Hydroxyl radical generation under both light sources was confirmed by electron paramagnetic resonance (EPR) spectroscopy. Using a novel solid-phase microextraction arrow (SPME-Arrow) coupled GC-MS method developed in this study, twenty degradation products were identified, and a photocatalytic degradation pathway was proposed. These results demonstrate that TiC@TiO₂ represents a promising visible-light-driven photocatalyst for pesticide remediation in water treatment applications.