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

Abstract

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.

Rice Straw as Green Waste in a HTiO2@AC/SiO2 Nanocomposite Synthesized as an Adsorbent and Photocatalytic Material for Chlorpyrifos Removal from Aqueous Solution

“…Chlorpyrifos and lead adsorption investigation on polyanilinegrafted cross-linked chitosan beads yielded similar results (G.X.C.S.) [20,24].…”

“…The pore diameters of AC and HTiO 2 were 4.322 and 0.2 nm, respectively, as shown in Figure 4. The surface properties have been described in detail (refer to [20]).…”

“…The R 2 values for the Freundlich model for HTiO 2 @AC/SiO 2 -Dark and Light are provided in Table 1. All model coefficient details were described in [20].…”

“…The activation process was carried out at 100 • C for 3 h using an activating agent of 85% H 3 PO 4 and 85% K.O.H [20].…”

“…Si (Li) Brüker determines powder particle chemical composition. XRD precautions and details have been described in detail in [20]. The Brunauer-Emmett-Teller (BET) method was used to determine the specific surface area, SBET, with relative pressure, p/p 0 , between 0.05 and 0.1.…”