Treatment of pharmaceutical-manufacturing wastewaters by UV irradiation/hydrogen peroxide process

In this study, the treatment of pharmaceutical-manufacturing wastewaters (PMWW) by advanced chemical oxidation using UV irradiation/hydrogen peroxide (H2O2) process has been investigated. Effects of experimental conditions such as H₂O₂ dose, initial organic matter concentration, temperature and initial pH value on the removal efficiency and kinetics of organic matter were investigated. Results of this study indicated that UV/H ₂O₂ process can be successfully used to completely destroy aromatic compounds, and to remove chemical oxygen demand (COD) and total organic carbon (TOC) with removal efficiencies more than 95% and 90%, respectively. Kinetic experiments have demonstrated that TOC removal rate followed pseudo-second order kinetics. Rate constants of 1.12×10 ^-3 A^-1 min^-1 and 2×10^-5 L mg^-1 min^-1 were calculated for UV absorbance at 277 nm and TOC decay, respectively. These results indicate that the mechanism of pharmaceuticals degradation involves two main steps: (i) Rapid degradation of aromatic compounds by hydroxylation followed by oxidative opening of benzene rings to form aliphatic derivatives and (ii) subsequent slow fragmentation of aliphatic derivatives into small carboxylic acids which are mineralized into CO₂, H₂O and other inorganic ions during the final steps of degradation.