Method And Characteristic Of Activated Carbon Adsorption/Microwave Regeneration For The Treatment Of Typical Organic Pollutants

An integrated granular activated carbon (GAC) adsorption/microwave regeneration process is adopted for the treatment of high concentration pentachlorophenol and acid orange 7 solutions. The basic thought is to fully utilize the two special characteristics of activated carbon: One is that organic pollutants in water can be effectively adsorbed onto the surface and into the inner pores of activated carbon; the other is that activated carbon absorbs microwave energy intensively and its temperature can rise to over 1000℃ in a few minutes under appropriate microwave irradiation, so that organic pollutants adsorbed on it will be desorbed, decomposed and carbonized.The following works are carried out in this dissertation:A sheltered type-K thermocouple is employed to record the temperature rising courses of GAC in a microwave irradiation field under various conditions. The results show that microwave power, the nature and moisture content of GAC are main factors that determining the temperature rising rate. This interaction of GAC and microwave is utilized to the preparation of GAC-supported copper catalyst. The catalyst is characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), iodine number and pentachlorophenol adsorption isotherm. It is found that elemental copper distributed uniformly on the surface of GAC, and after loading copper, the adsorption capacity of GAC decreases due to the occupation of adsorption sites by copper.Decomposition of a typical chlorinated organic chemical, pentachlorophenol (PCP), on virgin GAC and copper-loaded GAC is assisted by microwave irradiation. Firstly, PCP in water is adsorbed onto GAC, then PCP-loaded GAC irradiated by microwave in a quartz reactor. The results indicates that most of PCP adsorbed on virgin GAC is decomposed or bound irreversibly to GAC under 850 W microwave irradiation for 10 min, and less than 2 % is transformed into intermediates. A more rapid decomposition rate of PCP is observed oncopper-loaded GAC with larger amount of intermediates formed. Identification of intermediates is accomplished by GC/MS analysis, and the degradation mechanism of PCP is speculated. It is also confirmed that GAC could be reused after several adsorption/microwave regeneration cycles and its adsorption capacity could maintain a relatively high level, even higher than that of virgin GAC.Another investigation is performed for the regeneration of three GACs exhausted with acid orange 7 (AO7). The three GACs are made from different materials, i.e. coconut shells, almond nucleus and coal. The AO7 adsorption process is carried out in a continuous flow adsorption column. After adsorption, the AO7-saturated GAC is dried at 120 °C, and then regenerated in a quartz reactor by microwave irradiation. The efficacy of this procedure is analyzed by determining the rates and amounts of AO7 adsorbed in successive adsorption/microwave regeneration cycles. Effects of this regeneration on the structural properties, surface chemistry and the AO7 adsorption capacities of GAC samples are examined. It is found that after several adsorption/regeneration cycles, the adsorption rates and capacities of GACs could maintain relatively high levels. The improvement of GAC adsorption properties is resulted from the modification of pore size distribution and surface chemistry by microwave irradiation.This study provides a theoretical base for the practical application of the GAC adsorption/in situ microwave regeneration process for the treatment of high concentration refractory organic wastewater.