Fe3O4-CS-L: a magnetic core-shell nano adsorbent for highly efficient methyl orange adsorption

Tio2/SiO2/Fe3O4 magnetic nanoparticles synthesis and application in methyl orange UV photocatalytic removal

Three main parameters affecting TiO₂/SiO₂/Fe₃O₄ nanoparticles activity in photocatalytic degradation of methyl orange were investigated using response surface methodology (SRM). Precipitation method and sol-gel technique were used to prepare SiO₂/Fe₃O₄ electromagnetic composite support and TiO₂/SiO₂/Fe₃O₄ photocatalytically active nanoparticles. The specific surface area, pore volume, and average pore size of the synthesized nanoparticles were respectively equal to 56 m²/g, 0.12 cm³/g and 9.4 nm. The point of zero charge (PZC) of the catalyst was measured to be 5.9. The maximum and minimum photocatalytic degradation of methyl orange using the synthesized nanoparticles were 100% and 30%, respectively. A linear model was fitted to the obtained results with R²_adjusted equal to 0.87. The results of analysis of variance (ANOVA) revealed that catalyst concentration, reaction media pH and aeration rate were significantly affected the photocatalytic activity. Optimization was performed considering photocatalytic activity as the main objective functions. In order to maximize photocatalytic activity, catalyst loading, reaction media pH and aeration rate were respectively adjusted to 2,000 ppm, 3 and 2.5 L/min, which resulted in total methyl orange removal. Considering promising photocatalytic activity of TiO₂/SiO₂/Fe₃O₄ along with core-sell nanocomposite separation performance led us to propose this photocatalyst as an alternative solution for treating waste waters.

Modified xanthan gum for methyl orange uptake: Kinetic, isotherm, and thermodynamic behaviors

A novel hydrogel, named XGTTE, was prepared by modification of acrylamide and trimethylolpropane triglycidyl ether (TTE) on xanthan gum (XG). XGTTE was utilized as an adsorbent to remove methyl orange (MO) from an aqueous solution. Functional groups present in the external surface of XGTTE, such as carboxyl, hydroxyl, and amino groups, were identified, and these functional groups are responsible for the occurrence of the mechanism for MO adsorption. The structure of XGTTE after MO adsorption became more disordered. The adsorption dynamics and isotherms of MO onto XGTTE conformed well to the pseudo-second-order kinetics and the Freundlich equation, indicated that the adsorption included physical and chemical adsorption, with electrostatic interaction and hydrogen-bonding interaction. The calculated values of the thermodynamic parameters, such as changes in enthalpy (ΔH) and entropy (ΔS) were 27.30 kJ/mol and 125.63 J/mol/K, respectively. The changes in free energy (ΔG) were - 9.53 kJ/mol (293.15 K), -10.16 kJ/mol (298.15 K), -10.78 kJ/mol (303.15 K), -11.41 kJ/mol (308.15 K), and - 12.04 kJ/mol (313.15 K), respectively, indicating the adsorption process is endothermic, spontaneous, and entropic. The maximum adsorption capacities of XGTTE2, XGTTE3, XGTTE4, XGTTE5, and XGTTE6 for MO were 18.62 ± 0.99, 21.92 ± 0.84, 28.60 ± 0.84, 29.56 ± 0.99, and 12.38 ± 0.84 mg/g, respectively.