Treatment of Direct Red ۲۳ in Recirculating Semi-Pilot System by O۳/UV Process: Operational Parameters Effect and Central Composite Design Modeling

The treatment of C.I. Direct Red ۲۳ (DR۲۳) solution has been investigated by the ozonation under UV irradiation (O۳/UV) in a recirculating semi-pilot mode. Decolorization efficiency (DE%) of DR۲۳ was compared using the O۳ and O۳/UV processes, which were ۷۴.۹% and ۹۲.۷% after ۳۰-min treatment of the dye (۱۰۰ mg/dm۳), respectively. Then, the effect of experimental parameters on the O۳/UV process including initial dye concentration, ozone mass flow rate, and initial pH was studied. The obtained results revealed that the decolorization efficiency increased by enhancing of ozone amount and decreasing the DR۲۳ concentration; the decolorization process was performed efficiently at the basic condition (pH= ۱۰) due to the production of extra hydroxyl radicals. The pseudo-first-order kinetic was observed for the dye decolorization. Electrical energy per order decreases using the O۳/UV process at the desired pH ۱۰ indicating an adequate synergistic effect of the photolysis and ozonation. Eventually, the Central Composite Design (CCD) approach was properly applied for the prediction of the DE% with appropriate performance (R۲ = ۹۸.۵۲%) and optimization of the process.

کلیدواژه ها:

Ozonation ، UV irradiation ، azo dye ، Decolorization ، Central composite design