Magnetic chitosan/TiO2 composite for vanadium(V) adsorption simultaneously being transformed to an enhanced natural photocatalyst for the degradation of rhodamine B

A magnetic chitosan/TiO2 composite material (MCT) was developed. MCT was successfully synthesized by a one-pot method using chitosan, TiO2, and Fe3O4. The absorption equilibrium time of MCT was 40 min in absorbing vanadium(V), the optimal adsorption pH was 4, and the maximum adsorption capacity of vanadium(V) was 117.1 mg g−1. The spent MCT was applied to photocatalytic reactions for reutilization. The decolorization rates for the degradation of rhodamine B (RhB) by new and spent MCT were 86.4% and 94.3%, respectively. The new and spent MCT exhibited absorption bands at 397 and 455 nm, respectively, which showed that the spent MCT was red-shifted to the cyan light region. These results indicated that the forbidden band widths of the new and spent MCT were about 3.12 and 2.72 eV, respectively. The mechanism of the degradation reaction showed that the hydroxyl radicals as oxidants in the spent MCT mediated the photocatalytic degradation of RhB. In addition, the superoxide anion radical formation of hydroxyl radicals was the main reaction, and the hole generation of hydroxyl radicals was the subordinate reaction. The N-de-ethylated intermediates and organic acids were monitored by MS and HPLC.