Mineralization of reactive green 19 in recirculating system by combined O3/UV process

In this research, the degradation of C.I. Reactive Green 19 (RG19) from aqueous solution has been studied by the ozonation under UV irradiation (O3/UV) in recirculating mode. Mineralization efficiency was compared using the O3 and O3/UV processes, which was 78.54% and 91.03% after 70 min for 100 mg/L of the dye, respectively. Then, the effect of experimental parameters on the O3/UV process including initial RG19 concentration, ozone mass flow rate and initial pH on the COD removal was studied. The obtained results revealed that the COD removal increases by enhancement of ozone amount and decreasing of the DR23 concentration; the mineralization process was performed efficiently at the basic condition (pH= 10) due to the production of extra hydroxyl radicals from ozone molecules. The pseudo-first order kinetic was observed for the dye mineralization and electrical energy per order decreases using the O3/UV process indicating adequate synergistic effect of the photolysis and ozonation. Eventually, central composite design (CCD) approach was properly applied for prediction of the COD removal with appropriate performance (R2 = 99%) and optimization of the process.