Adsorption of azo dye methyl orange from aqueous solutions using TiO2-SiO2/alginate nanocomposite

In this research work, TiO2-SiO2/alginate nanocomposite with high surface area has been prepared and applied as adsorbent for the removal of azo dye methyl orange from aqueous solutions. Characteristics of phases and crystallite size of TiO2-SiO2/alginate nanocomposite were obtained from XRD and the surface area and pore size distribution were achieved from BET and BJH analysis methods. TiO2-SiO2/alginate nanocomposite with pure anatase phase, the average crystallite size of 8.3 nm, has specific surface area of 188.4 m^2/g^–1. To find the nature of adsorption procedure, the equilibrium adsorption isotherms were investigated. The linear correlation coefficients of Langmuir, Freundlich and Temkin isotherms were obtained. Based on results, Langmuir isotherm model fitted the experimental data better than the other models. According to the Langmuir isotherm model, the maximum adsorption capacity of TiO2-SiO2/alginate nanocomposite for sequestering methyl orange was about 68.85 mg/ g^−1. Furthermore, negative ΔG0 and ΔH0 values obtained through thermodynamic investigation indicated that the adsorption of methyl orange onto TiO2-SiO2/alginate nanocomposite was simultaneous and exothermic in nature, respectively.