Evaluation of the Removal of Reactive Green 19 by Using O3/UV Advanced Oxidation Process

Recently, water crisis has been a global threat for most countries, particulately for midelist countries. In this regard industrial wastewaters treatment is a vital to prevent unfavorable environmental consequences. Advanced oxidation processes are the preferred treatment process for the removal of resisitant organic pollutants without producing secondary wastes. In this research study, the removal of RG19 from aqueous solution was studied by O3/UV processes. A recirculation system equipped with an UV lamp and ozonation tank was applied for the degradation of model di-azo dye from textile industry. The RG19 concentration was measured using a spectrophotometer at 625 nm. Comparison of RG 19 removal by O3 and O3/UV showed that, under same operational condition, the combined process had more decolorization efficiency (DE%). Moreover, the experimental results revealed that the DE% increased by increasing the ozone amount and decreasing the concentration of RG19. The efficiency of degradation process was performed at the basic (alkali) condition due to the production of extra hydroxyl radicals. The pseudo-first order kinetic was observed for the dye decolorization. The consumption of electrical energy decreased per order using the O3/UV process at the desired basic pH; indicating adequate synergistic effect of the photolysis and ozonation. In addition, central composite design (CCD) approach was applied for prediction of the DE% at pH= 10 for independent variables including the RG19 concentration range (379.6-1220.4 mg/L), ozone mas flow rate range (2.5-7.2 g/h), and process duration time range (4.8-55.2 min). After investigating the effect of the operational parameters on the decolorization efficiency, a nonlinear CCD model was developed for prediction of DE%. The optimum operational conditions for the complete dye degradation at pH=10 was experimentally verified when: [RG19] concentration was of 524 mg/L, ozone mass flow rate was 7 g/h, and process time was 54 min. The EEO declined at the optimized pH for the coupled process owing to the synergistic effect of ozonation and UV.