Adsorption and Photocatalytic Properties of Titanium Dioxide/Chitosan/Bentonite Composites for Methylene Blue
Xiaofang Li, Xiaoqiang Feng, Ruixian Li, Wei Liu
Abstract
TiO2/chitosan/ bentonite composites were synthesized and characterized by infrared spectroscopy (IR), X-ray powder diffraction, field emission scanning electron microscopy (FE-SEM), energy disperse spectroscopy (EDS), and X-ray photoelectron spectroscopy (XPS). As a catalyst carrier, chitosan/bentonite plays an important role of supporting and dispersing catalysts. Hence, the adsorption and photocatalytic degradation behavior of TiO2/chitosan/bentonite on cationic dye methylene blue (MB) removal were investigated. Results showed that the optimized TiO2/chitosan/ bentonite sample has an excellent adsorption efficiency for MB (initial concentration was 30 mg/L) with a removal rate that exceeds 80% after 30 min, then the adsorbed contaminants can be effectively degraded during the later visible-light irradiation process. In addition, the photocatalytic degradation data was well fitted to the pseudo-first-order kinetics models, and the reaction rate constant k was 4.2 times of bare TiO2. The mechanisms of super adsorption and photocatalysis were discussed via material characterizations, adsorption models and photogenerated species analyses. Results indicated that the enhanced adsorption of TiO2/chitosan/bentonite for MB is due to surface electrostatic attraction and hydrogen bonding, meanwhile the h+ and $$^{\bullet }{\text{OH}}$$ radicals played crucial roles in the dye photocatalytic degradation.