Adsorption Ability of Polyaniline/TiO₂ Composite for U(Ⅵ) in Aqueous Solution

Polyaniline (PANI)/TiO₂ was synthesized via polymerization of aniline on the surface of TiO₂ which was prepared by a sol-gel method. And the surface functional groups, thermal stability and surface elemental composition of TiO₂, PANI and PANI/TiO₂ were characterized by FT-IR, TGA and XPS. Effects of pH, contacting time, initial U(Ⅵ) concentration, temperature on the U(Ⅵ) adsorption were investigated and optimized by static batch experiments. The results of FT-IR, TGA and XPS indicate that PANI/TiO₂ composite is successfully prepared. The optimum pH value for U(Ⅵ) adsorption on TiO₂, PANI and PANI/TiO₂ is 5.0, 4.5 and 5.0, respectively. The adsorption isotherms and kinetics as well as the thermodynamics were studied using various models. The results show that the adsorption processes are fitted well to the Langmuir and pseudo-second order equations. In addition, the monolayer adsorption capacity of TiO₂, PANI and PANI/TiO₂ is 11.49, 22.41 and 43.29 mg/g, respectively. The adsorption processes of TiO₂, PANI and PANI/TiO₂ for U(Ⅵ) are spontaneous and endothermic in nature. And, the PANI/TiO₂ composite shows excellent reusability, whose adsorption capacity only decreases by 15.4% when it is used at the fifth time.