Adsorption of bisphenol A by TiO₂-based organic–inorganic hybrid materials

In this study, TiO₂-P25 was modified with benzoic acid (BA) and 2-naphthalenecarboxylic acid (NCA), and subsequently used to adsorb bisphenol A (BPA). The relationship between the hydrophobicity of the modified TiO₂ and the amount of BPA adsorbed was investigated. The equilibrium adsorption data were analyzed using the Langmuir, Freundlich, Dubinin–Radushkevich, Temkin, Harkins–Jura, and Halsey models. Additionally, TiO₂ and Ti_xZr_(1-x)O₂ of high specific surface area were synthesized via the sol-gel and solvothermal methods. The materials were modified using NCA and used to adsorb BPA. The surface properties of the adsorbent were investigated by Brunauer–Emmett–Teller surface area analysis, Barrett–Joyner–Halenda pore size analysis, CO₂ temperature-programmed desorption, and CHN elemental analysis. The specific surface area of Ti_xZr_(1-x)O₂ (252.1– 455.0 m²/g) was higher than that of TiO₂ (157.6 m²/g) and the amount of NCA modified onto Ti_xZr_(1-x)O₂ (1.106– 1.319 mmol/g) was also higher than that of TiO₂ (0.405 mmol/g). The amount of NCA modification onto Ti_xZr_(1-x)O₂ was promoted by surface base points. The maximum amount of BPA adsorbed was 22.4 mg/L, which was 5.86 times that of TiO₂-P25, and approximately 90 % of the BPA was removed from a solution having an initial concentration of 100 mg/L.