Removing the Oxamyl from Aqueous Solution by a Green Synthesized HTiO₂@AC/SiO₂ Nanocomposite: Combined Effects of Adsorption and Photocatalysis

The photocatalytic degradation and adsorption of the oxamyl pesticide utilizing a nano-HTiO2@activated carbon-amorphous silica nanocomposite catalyst (HTiO2@AC/SiO2). Sol-gel Synthesis was used to produce HTiO2@AC/SiO2, which was examined using Scanning Electron Microscopy, Transmission Electron Microscopy, and an X-ray diffractometer. The analyses confirmed that HTiO2 is mainly present in its crystalline form at a size of 7–9 nm. The efficiency of HTiO2@AC/SiO2 was assessed at various pHs, catalyst doses, agitating intensities, initial pesticide concentrations, contact times, and temperatures under visible light and in darkness. Oxamyl adsorption kinetics followed a pseudo-second-order kinetic model, suggesting that the adsorption process is dominated by chemisorption, as supported by a calculated activation energy of −182.769 kJ/mol. The oxamyl adsorption is compatible with Langmuir and Freundlich isotherms, suggesting a maximum adsorption capacity of 312.76 mg g−1. The adsorption capacity increased slightly with increasing temperature (283 K 2@AC/SiO2 under visible light. This indicates spontaneous adsorption, and negative (ΔS) explain a decreased randomness process. HTiO2@AC/SiO2 would be a promising material