Degradation of phenolic wastewaters by solar/TiO_2 and solar/TiO_2/H_2O_2 processes

摘要

The application of Advanced Oxidation Processes (AOPs) (solar/TiO_2 and solar/TiO_2/H_2O_2) to treat phenol, o-cresol, m-cresol, and p-cresol wastewaters was investigated. The experiments were performed in batch solar reactor using TiO_2 as catalyst. The effect of the hydrogen peroxide concentration on the degradation kinetics was evaluated in the range of 0.15-1.5 g/L. It was observed that the degradation rate increased as the hydrogen peroxide increased, but excessive H_2O_2 concentration was detrimental. The rate of degradation is two to three times faster in solar/TiO_2/H_2O_2 process when compared with solar/TiO_2 process. In the presence of inorganic salts, the phenol removal was 19% and 90% in solar/TiO_2 and solar/TiO_2/H_2O_2 process, respectively. For untreated samples of 100 mg/L the BOD/COD ratio is 0, while solar photocatalytic treatment of 1 h permits its enhancement up to values near 0.66 and 0.57 for m-cresol and o-cresol; for phenol and p-cresol the values were nearer to 0.53 and 0.65 after 2 h and 3 h phototreatment respectively, which represent considerable biodegradability of wastewaters.