Activation of periodate by granular activated carbon for acid orange 7 decolorization

Abstract

This study investigated the activation of periodate (IO4−) by granular activated carbon (GAC) for acid orange 7 (AO7) decolorization at ambient temperature. It was found that there existed a remarkable synergistic effect in the GAC/IO4− system. Some influential parameters, including periodate concentration, GAC dosage, initial solution pH and anions (Cl− and CO32−) were examined and analyzed. The results from radical scavenging experiments (with ethanol and tert–butyl alcohol) and electron spin resonance (ESR) analysis revealed that hydroxyl radical (•OH) made a minor contribution to AO7 decolorization. Furthermore, the increasing formation of iodate (IO3−) as the reaction proceeded in the presence of excessive ethanol indirectly suggested that iodyl radical (IO3•) was likely to be the dominating reactive species that controlling the oxidation process. In the reuse experiments, the efficiencies of AO7 decolorization enhanced surprisingly and remained 100% when the dried-GAC (GAC collected from the former cycle experiment and dried at 105°C for 24h) was reused for over ten cycles, which indicated that the dried-GAC showed remarkable catalytic ability and sustainable reuse capability. Besides, a series of experiments were conducted to testify the main contributor to the strong enhancement of AO7 decolorization with the dried-GAC.