Phenol degradation under visible light irradiation in the continuous system of photocatalysis and sonolysis

The combination of photocatalysis under visible light irradiation and sonolysis in the continuous system has been used to degrade an aqueous solution of phenol. ZnFe2O4/TiO2–GAC was employed as the photocatalysts which were obtained by sol–gel process and characterized by spectroscopic X-ray diffraction (XRD), scanning electron microscopy with energy dispersive X-ray microanalyses (SEM–EDX) and Brunauer–Emmett–Teller sorptometer (BET). It was observed that the rates of phenol degradation were affected by the initial pH value of phenol solution, salt addition, gas supplying and the recycling times of the recovered photocatalyst. The kinetic law for the phenol degradation can be apparently expressed as the first-order with respect to the concentration of phenol. Degradation of phenol solution in the continuous system, i.e., photocatalysis and sonolysis has synergistic effect in comparison with the photocatalytic reaction and sonolysis, respectively.