Enhanced activation of periodate by iodine-doped granular activated carbon for organic contaminant degradation

In this study, iodine-doped granular activated carbon (I-GAC) was prepared and subsequently applied to activate periodate (IO4-) to degrade organic contaminants at ambient temperature. The physicochemical properties of GAC and I-GAC were examined using scanning electron microscopy, N-2 adsorption/desorption, Raman spectroscopy, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy. No significant difference was observed between the two except for the existence of triiodide (I-3(-)) and pentaiodide (I-5(-)) on I-GAC. The catalytic activity of I-GAC towards IO4- was evaluated by the degradation of acid orange 7 (AO7), and superior catalytic performance was achieved compared with GAC. The effects of some influential parameters (preparation conditions, initial solution pH, and coexisting anions) on the catalytic ability were also investigated. Based on radical scavenging experiments, it appeared that IO3 center dot was the predominant reactive species in the I-GAC/IO4- system. The mechanism underlying the enhanced catalytic performance of I-GAC could be explained by the introduction of negatively charged I-3(-) and I-5(-) into I-GAC, which induced positive charge density on the surface of I-GAC. This accelerated the interaction between I-GAC and IO4-, and subsequently mediated the increasing generation of iodyl radicals (IO3 center dot). Furthermore, a possible degradation pathway of AO7 was proposed according to the intermediate products identified by gas chromatography-mass spectrometry. (C) 2017 Elsevier Ltd. All rights reserved.