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 < 323 K < 373 K), suggesting an exothermic process with the Gibbs free energy change Delta G, enthalpy change Delta H, and entropy change Delta S degrees, being -3.17 kJ/mol, -8.85 kJ/mol, and -0.019 J/mol K, respectively, at 310 K for HTiO2@AC/SiO2 under visible light. This indicates spontaneous adsorption, and negative (Delta S) explain a decreased randomness process. HTiO2@AC/SiO2 would be a promising material.