Degradation of phenol in water by the combination of sonolysis and photocatalysis

The combination of sonolysis and photocatalysis has been used to degrade an aqueous solution of phenol. The synergistic index for sonophotocatalysis was 1.06, indicating that there was a slightly synergistic effect between sonolysis and photocatalysis, and that the degradation by sonolysis, photocatalysis, and sonophotocatalysis presented a good fit to the pseudo-first-order kinetic model. Additionally, the effects of parameters such as the initial pH value of the solution, dissolved gases, salt addition, Fe3+ ions, and metaloxide (CuO and MnO2) on the sonophotocatalytic degradation were studied. The results shown that acidic/weakly acidic condition is superior to alkaline condition, and higher concentration of dissolved oxygen and the presence of Fe3+ favored the phenol degradation, CuO and MnO2 had no significant effect on the degradation, while NaHCO3 restrained the degradation rate.