| Advanced oxidation technologies were widely used to degrade contaminantsrecently. The advanced oxidation technology based on peroxymonosulfate (PMS) caneffectively degrade contaminants in solution. This kind of technology is easily to beoperated, no secondary pollution and no sludge. Therefore, it becomes the new studyhotspot.The conventional PMS activation methods were UV and metal activation, butthey all have shortcoming. Enriching PMS activation method is the exigent studyneed. In this study, granular activated carbon (GAC) was used as a catalyst to activateperoxymonosulfate (PMS) to degrade azo dye Acid Orange7(AO7) in aqueoussolution. AO7degradation, the mechanism of GAC reuse, AO7degradation andacidic modification GAC activation PMS was studied to discuss the GAC/PMScombined system. Specific studies are as follows:(1) In the GAC/PMS combined system, GAC was an excellent PMS catalyst. Aremarkable synergistic effect was found between GAC and PMS. The dyedecolorization was much faster in the combined system than that in only GACadsorption or PMS oxidation system. For the GAC/PMS system, under the conditionsof molar ratio of PMS/AO7at100:1and dosage of GAC at1.0g/L, the efficiency ofdecolorization of AO7was about85%in5hours. The decolorization efficiencyincreased as the PMS concentration, the GAC dosage and the reaction temperatureincreased. The reaction followed pseudo-first-order kinetic and low activation energywas determined to be25.13kJ/mol.(2) GAC regeneration is one of the key of GAC application. Regeneration GACand extending the life time of GAC is significant. Therefore, this study discussed themechanism of GAC regeneration. The recovery performance of GAC also was studied through the GAC reuse experiment and the AO7-spent GAC experiment. It was foundthat GAC had no obvious deactivation after being reused four times and there was notany difference on AO7removal between the GAC/PMS system and the AO7-spentGAC/PMS system, which implied that GAC can be in-situ regenerated. Theregeneration ability increased as the dosage of PMS increased. During the process ofAO7degradation by GAC activated PMS oxidation, GAC surface can be oxidized byPMS and GAC catalytic ability enhanced. It was found that only the catalytic abilitywas regenerated, but the sorption capability was not. Although GAC almost lostsorption ability, its catalytic ability could retain the same level as before. After10days sequence operation, GAC had no obvious deactivation.(3) To improve GAC adsorption and catalysis ability, many methods often wereused to pre-treat GAC. Among these methods, acidic modification was the easiest andeffective method. In this study, different kinds of acid modified GACs were used toactivate PMS to degrade AO7. Nitric acid, hydrochloric acid, phosphoric acid andsulfuric acid were used to treat GAC. PMS decomposition ratio and GAC reuseperformance were also studied. It was found that the GAC modified by nitric acid andsulfuric acid had a better catalysis and recovery performance, because the two acidshave stronger oxidation ability than hydrochloric acid and phosphoric acid. Acidconcentration had a slight effect, especially for hydrochloric acid.(4) Other carbon materials (coconut GAC and Activated carbon fiber, ACF) wereused to activate PMS to degrade AO7. It was found that coconut GAC/PMS showedthe similar catalytic efficiency with GAC/PMS. ACF/PMS showed excellent AO7decolorization efficicency. With the low ACF dosage and PMS concentration, AO7can be completely degraded in a short time. The decolorization efficiency increased asthe PMS concentration, the ACF dosage and the reaction temperature increased. Thereaction followed a pseudo-first-order kinetics and a lower activation energy wasdetermined to be9.207kJ/mol. ACF/PMS also can degrade high concentration AO7solution and ACF can be reused without deactivation. |
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