Decolorization of Mordant red 73 azo dye in water using H_2O_2/UV and photo-Fenton treatment

摘要

Decolorization of the Mordant red 73 (MR73) azo dye in water was investigated in laboratory-scale experiments using UV/H_2O_2 and photo-Fenton treatments. Photodegradation experiments were carried out in a stirred batch photoreactor equipped with a low-pressure mercury lamp as UV source at 254 nm. The effect of operating parameters such as pH, [H_2O_2], [dye] and the presence of inorganic salts (NaNO_3, NaCl and Na_2CO_3) were also investigated. The results indicated that complete dye decolorization was obtained in less than 60min under optimum conditions. Furthermore, results showed that dye degradation was dependent upon pH, [H_2O_2] and initial dye concentration. The presence of chloride ion led to large decreases in the photodegradation rate of MR73 while both nitrate and carbonate ions have a slight effect. The photo-Fenton treatment, in the presence of Fe powder as a source of Fe~(2+) ions, was highly efficient and resulted in 99% decolorization of the dye in 15 min. Mineralization of MR73 dye was investigated by determining chemical oxygen demand (COD). In a 3 h photoperiod "65%" of the dye was mineralized by the H_2O_2/UV process, while the photo-Fenton treatment was more efficient producing 85% mineralization over the same 3-h period.