Preparation of diatomite–TiO2 composite for photodegradation of bisphenol-A in water

To enhance the photodegradation performance of pure titanium dioxide (TiO2), diatomite was used as a porous carrier to immobilize TiO2 powders using calcination method. The photodegradation of bisphenol-A (BPA; 4,4′-isopropylidenediphenol), which has been listed as one of endocrine disrupting chemicals, was carried out in a batch suspension reactor using pure TiO2 powders and diatomite–TiO2 composites, respectively. Under the controlled conditions, the photocatalytic efficiencies of the BPA degradation by the diatomite–TiO2 composites can be found to be higher than those by pure TiO2 powders. This result should be attributable to the accessibility of the BPA molecules to the surface of TiO2 particle in the modified photocatalysts, showing that the enrichment of the organic solute enhanced the rate of photodegradation on the diatomite–TiO2 composite. However, the photodegradation efficiency was not dependent on the pore properties of these TiO2 photocatalysts. The experimental results further indicated that the photodegradation kinetics for the destruction of BPA in water followed the first-order model well. The apparent first-order reaction constants (kobs), thus obtained from the fittings of the model, were in line with the destruction-removal efficiencies of BPA in all the photocatalytic experiments.