The decolorization and mineralization of orange II by microwave-assisted ball milling

This study proposed an integrated technique of reduction coupled with an oxidation process in order to acquire simultaneously both decolorization and mineralization of orange II under the condition of microwave-assisted milling. Experimental variables of initial dye concentration, iron dosage, microwave power, solution pH and initial H₂O₂ concentration were systematically studied. Under the optimal operational parameters (100 mg/L aqueous solution of pH 3 containing 400 mg/L H₂O₂ while controlling microwave power at 400 W), the results showed that the decolorization efficiency is up to 91% after reaction for 2 min and the total organic carbon removal efficiencies were 72.7% and 80.5% at a reaction time of 10 min and 60 min, respectively. It indicated that the decolorization and mineralization of orange II were largely enhanced by the reduction of zero-valent iron in the ball milling process and the oxidation of hydroxyl radicals generated by hydrogen peroxide. It suggested that microwave-assisted ball milling technology has potential application for degradation of azo dye in wastewater.