Degradation of aqueous p-nitrophenol by ozonation integrated with activated carbon

Degradation of aqueous p-nitrophenol (PNP) by ozonation integrated with granular activated carbon (GAC) was investigated. In the integrated process, organics were removed by the joint effect of oxidation and adsorption, and the removal was considerably enhanced. Operation parameters including pH value and ozone dosage were optimized, and pH was found to be the primary factor in the integrated process. Intermediates in PNP oxidation, including aromatic compounds and low-mass acids, were identified, and possible pathways of PNP degradation were introduced. The reaction mechanism was explored using radical scavenger to suspend the oxidation effect of radicals. The results indicated that the adsorption effect predominated in organics removal at acidic conditions while catalytic oxidation contributed primarily at basic conditions. In addition, the integrated process was successfully applied to treat a high concentrated real wastewater, showing that the integrated process would have great potential in practical application.