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

This study investigated the activation of periodate (IO 4 − ) 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/IO 4 − system. Some influential parameters, including periodate concentration, GAC dosage, initial solution pH and anions (Cl − and CO 3 2− ) 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 (IO 3 − ) as the reaction proceeded in the presence of excessive ethanol indirectly suggested that iodyl radical (IO 3 • ) 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 24 h) 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. [ABSTRACT FROM AUTHOR]