[Application of solar irradiation / K2S2O8 photochemical oxidation process for the removal of reactive blue 19 dye from aqueous solutions]

ABSTRACT

Dyes are organic compounds with complex structures, which due to toxicity, carcinogenicity and nonbiodegradabity, this type of pollutants is one of the most important pollutants of the environment. The goal of this research was to study the feasibility of the application of solar irradiation in presence of potassium persulfate [K[2]S[2]O8] for the removal of Reactive blue19 [RB19] from synthetic wastewater. This research was carried out in laboratory scale with using of 200ml volume of batch photoreactor. The effects of operating parameters such as concentration of K[2]S[2]O[8], pH, photo exposure time and preliminary concentrations of dye on decolonization have been evaluated. Different concentrations of pollutant in waste water were prepared by solution of variousmasses of RB19 on tap water. The reactors were exposed with natural solar irradiation as a UVA source from11 am to 14 pm. The maximum absorption wave length of this dye [lambda[max]] was determined by spectrophotometer [Unico, 2100]. The measurement of dye concentrations was determined with using of standard curve and its best line equation Analysis of absorbtion spectra showed that the lambda[max] of RB19 is 592 nm. The average intensity of the UVA irradiated from solar system was 54.6 microW/Cm2. The results of decolorization process showed that 38.2%of this dye can be removed within 3 hr in the presence of potassium persulfate and decreasing of pH leads to the elevation of dye removal efficiency. Based on these findings, the efficiency of dye removal with 3h photo exposure time and pH ranges of 4,6 and 8 were found to be 98.2 88.5 and 78.5%, respectively. Also, the results showed that increasing of K[2]S[2]O[8] dosage leads to elevation of dye removal efficiency in 3h photo exposure time and K[2]S[2]O[8] dosages within 1-5mmol/L, with the removal efficiency of 75,86,92,95 and 98.5%, respectively. Analysis of data indicates that the kinetic of the removal of RB19 with this process is a first order reaction which its rate constant is 0.01min-1. Due to the operation problems presented in heterogeneous photocatalitical processes such as catalysts separation and high costs of operation and maintenance of these processes caused by manmade sources of irradiations; homogeneous photocatalitical process with using of potassium persulfate associated with natural solar irradiation can be used as a suitable process for the removal of dyes from textile industries wastewaters