The Study On Degradation Of Pentachlorophenol Adsorbed On Granular Activated Carbon And Regeneration Of Granular Activated Carbon By DBD Plasma

Non-equilibrium plasma pollutant control is an end-of-pipe advanced oxidation technology, which integrates effectiveness of high-energy electron impact, active species including ozone, ultraviolet light, etc. So it has many advantages such as high treatment efficiency, rapid and non-selective reactivity, and free of secondary pollution, etc. However, for the treatment of low-concentration wastewater, there are some drawbacks, such as low energy effieiency. Based on such problems, in the study, pentachlorophenol (PCP) in water was firstly adsorbed onto granular activated carbon (GAC), and then the saturated GAC was introduced into packed double-dielectric barrier discharge (DBD) plasma to simultaneously realize the degradation of PCP adsorbed on the GAC and the regeneration of GAC. The main results are summarized as follows:(1) The interaction between DBD plasma and GAC was investigated. The effects of applied voltage, power frequency, GAC pack and partical size on discharge images, waveforms of applied voltage and discharge current and power were studied. The effects of DBD plasma on morphology, acid-base properties and adsorption capacity of virgin carbon were also investigated. It was found that the discharge could occur under the condition that the bed was filled with GAC, and the micro-discharge became more homogeneous. After DBD plasma treated, the GAC surface presented unsmooth, and the number of acidic groups significantly increased with a decrease in the number of basic groups.(2) The effect of DBD plasma on PCP decomposition on GAC and GAC regeneration efficiency (RE) was evaluated. The influences of applied voltage, power frequebcy, treatment time, O2 flow rate, gas type, GAC bed thickness, partical size and regeneration number on the decomposition of PCP on GAC and RE of GAC by double-DBD plasma were studied. The results showed that increasing applied voltage, power frequency, treatment time and O2 flow rate were favorable for PCP degradation on GAC. Enhancing applied voltage and O2 flow rate contributed to the RE. With the treatment time continued, the RE increased firstly and then decreased, the optimized treatment time was found at 1.5 h in this discharge system. With the increase of regeneration cycles, the adsorption rates of regenerated-activated carbon presented a slight decrease. After four continuous adsorption/regeneration cycles, the RE of activated carbon was approximately 73%. After the spent GAC were treated for 1.5 h under the condition of 23.4 kV,500 Hz,2 L/min O2, degradation efficiency of PCP and RE were 65.2% and 87% respectively. Moreover, the RE decreased slightly with the increase of regeneration mumber.(3) The PCP degradation mechanism and GAC regeneration mechanism were studied. The results indicated that Ar-Cl bond was strongly decreased after plasma treated, and adsorptive sites were released. However, the physicochemical properties were affected during the discharge and a certain sites were occupied by intermediates, the adsorption capacity of GAC couldn't be recoveried completely.