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

• Published in: Catalysts Vol. 12; no. 2; p. 163
• Main Authors: El Shahawy, Abeer, Ragab, Ahmed H., Mubarak, Mahmoud F., Ahmed, Inas A., Mousa, Abdullah E., Bader, Dina M. D.
• Format: Journal Article
• Language: English
• Published: Basel MDPI AG 01.02.2022
• Subjects: Activated carbon; Adsorption; Aqueous solutions; Catalysts; Chemical reactions; Chemical synthesis; Chemisorption; Crystal structure; Darkness; degradation; Electron microscopy; Enthalpy; Gibbs free energy; Luminous intensity; Morphology; Nanocomposites; Particle size; Pesticides; Photocatalysis; photocatalyst; Photodegradation; Pollutants; Porous materials; Scanning electron microscopy; Silicon dioxide; Sol-gel processes; Surface water; Titanium; titanium (IV) dioxide
• ISSN: 2073-4344; 2073-4344
• DOI: 10.3390/catal12020163

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 ΔG, enthalpy change ΔH, and entropy change ΔS°, 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 (ΔS) explain a decreased randomness process. HTiO2@AC/SiO2 would be a promising material.