Preparation of polypyrrole–TiO2 and its adsorption and photocatalytic degradation of salicylic acid

Polypyrrole–TiO2 composited photocatalysts have been prepared by sol–gel method. The as-prepared photocatalysts were characterized by scanning electron microscopy, X-ray diffraction, and FT-IR. The results showed that the polypyrrole–TiO2 consists of well-defined hollow tubes with the size of inner diameter 0.5–1 μm, and the hollow tubes exhibited non-crystal phase and it was well-formed anatase phase at high temperature treatment. The performances of polypyrrole–TiO2 were tested by adsorption and degradation of salicylic acid. The adsorption equilibrium data, at different temperatures, were described by the Langmuir, Freundich, Temkin and Dubinin–Radushkevich isotherm models. The results showed that the Langmuir model was well fit to the equilibrium adsorption data, and the adsorption capacities could reach 32.4 mg g−1. The photocatalytic degradation activity of salicylic acid with polypyrrole–TiO2 was investigated under visible light irradiation. It was revealed that the degradation rate of salicylic acid with the polypyrrole–TiO2 which synthesized at 5°C without heat treatment could reach 48.6%. And the kinetics of photocatalytic degradation obeyed second-order kinetics.