Sonophotolytic degradation of synthetic pharmaceutical wastewater: statistical experimental design and modeling.

The merits of the sonophotolysis as a combination of sonolysis (US) and photolysis (UV/H2O2) are investigated in a pilot-scale external loop airlift sonophotoreactor for the treatment of a synthetic pharmaceutical wastewater (SPWW). In the first part of this study, the multivariate experimental design is carried out using Box-Behnken design (BBD). The effluent is characterized by the total organic carbon (TOC) percent removal as a surrogate parameter. The results indicate that the response of the TOC percent removal is significantly affected by the synergistic effects of the linear term of H2O2 dosage and ultrasound power with the antagonistic effect of quadratic term of H2O2 dosage. The statistical analysis of the results indicates a satisfactory prediction of the system behavior by the developed model. In the second part of this study, a novel rigorous mathematical model for the sonophotolytic process is developed to predict the TOC percent removal as a function of time. The mathematical model is based on extensively accepted sonophotochemical reactions and the rate constants in advanced oxidation processes. A good agreement between the model predictions and experimental data indicates that the proposed model could successfully describe the sonophotolysis of the pharmaceutical wastewater.