Efficiency of Integrated Photocatalytic UV/Persulfate Process in Removal of Methylene Blue and Acid Green 3 from Aqueous Solutions

The release of dyestuff wastewaters produced in textile industry into receiving waters affects both human health and the environment. The aim of this study was to investigate the efficiency of a photocatalytic UV/persulfate process in removal of methylene blue and acid green 3 dyes from aqueous solutions.

The current study was an experimental study, in which the effects of the most important operating variables including pH (3,5,7,9,11), contact time (5, 10, 20, 50, 70, and 90 min), Na2S2O8 dose (0.1, 1, 3, and 5 mM/L) as well as acid green 3 and methylene blue concentrations (10, 25, 50, 75, 100, 200, and 500 mg/L) were investigated to determine the optimal condition for dye removal in a batch cylindrical photoreactor equipped with a 9-W UV-C lamp, in laboratory scale. The concentration of target dyes in aqueous solution was detected using UV/Vis spectrophotometer.

The results showed that, under the optimum condition for studied variables, i.e. pH 7, persulfate concentration 1 mM/L, initial dye concentration of 50 mg/L, and contact time of 20 min, the removal efficiency of acid green 3 and methylene blue were 93.91 and 95.44%, respectively. In addition, at the aforementioned condition, the removal rate of COD and TOC were 67.35 and 53.30 % for acid green 3 as well as 70.74 and 56.99 % for methylene blue, respectively. Experiments were carried out under optimal condition for real wastewater, in which the removal rates of MB and AG Dyes were 76.11 and 72.51%, respectively, indicating the effectiveness of developed method.

The findings showed that the integrated UV/S2O8 process is a promising method for removing the methylene blue and acid green 3 dyes from aqueous solutions and it can be applied as an effective alternative for treatment of dyes-containing solutoins in large-scale applications.