| A novel process, named microwave assisted catalytic wet air oxidation, is adopted for the treatment of p-nitrophenol (PNP) and pentachlorophenol (PCP) solutions through a granular activated carbon (GAC) or carbon-supported metal catalyst fixed bed under microwave irradiation and ambient pressure. The process is operated in continuous flow mode, and air is applied for oxygen supply. In order to investigate the possibility of its practical application, the process is applied to treat different industrial organic effluents with high concentration of pollutants.The following works are carried out in this dissertation:In order to eliminate the effect of GAC or carbon-supported metal catalysts adsorption on the degradation of target compound, the pre-adsorbed amounts of PNP and PCP onto catalysts are determined on the basis of their adsorption isotherms respectively.PNP solutions, its concentration from 200 mg·L-1 to 11000 mg·L-1, are treated by microwave assisted catalytic wet air oxidation using GAC as catalyst. The results show that PNP removal efficiencies are higher than 90%, and the concentration of the outflows keep constant with increasing initial solution concentration, PNP from aqueous solution are almost completely degraded and minerialized. Microwave power, air flow, GAC dose, and influent flow are proved to be major factors, and the influence of them on PNP degradation is investigated in order to obtain optimal experimental parameters. Under optimal conditions, the micropore amounts of GAC can be reduced for a long time irradiation, which result in the decrease of PNP degraded efficacy. o-Nitrophenol, phenol, nitrobenzene, hydroquinone, benzoquinone and 3-[p-nitrophenoxy] propionic acid are main course products for PNP degradation, pyrolysis and oxidation reaction coexist in the degradation pathways of PNP by microwave assisted catalytic wet air oxidation. PNP from aqueous solution can not be degraded in electrical heating experiment, and the removal effect of PNP treated by silicon carbide is apparently lower than GAC. The absorbing-microwave property and strong adsorption ability of GAC play important roles in the course of PNP degradation.Carbon-supported metal catalysts are prepared by using microwave energy, metallic particles disperse uniformly on the surface of GAC carrier, and its sizes of scanning electron microscopy and X-ray diffraction are smaller than those fabricated by conventional impregnation method. It needn't hydrogen reduction in the process of catalyst preparation by microwave method, and GAC reacts to metallic oxide as reductant.PNP and PCP from aqueous solution can be degraded and mineralized effectively by microwave through a carbon-supported metal catalyst fixed bed. Compared with GAC, carbon-supported metal catalyst has a higher removal efficiency and better stability in the treatment of PNP solution. Metal loaded onto the catalyst don't change the degradation pathways of PNP, and only accelerate PNP's degradation reaction. Dechlorinated and dehydroxy course products are formed in the course of PCP degradation, pyrolysis and oxidation also coexist in PCP's degrading course. Oxidation and sintered phenomena occur on the surface of copper and manganese particles, and the metallic leach happens in the course of reaction. Noble metal, such as platinum, has a good stability and no metallic dissolution in experiment.Biodegradability of the outflow, treated by GAC or carbon-supported metal catalyst, is improved apparently by microwave assisted catalytic wet air oxidation process.Pesticide wastewater, its initial CODo- concentration 7027 mg-L"1, and petrochemical aldehydic wastewater with initial CODo 33494 mg-L"1 are treated on the lab-scale setup by microwave assisted catalytic wet air oxidation. The results show that CODq- removal efficiency reachs 90% for pesticide wastewater, and CODa and TOC removal efficiencies are 94% and 99% for aldehydic wastewater respectively. Dye wastewater, pesticide wastewater, medical wastewater and simulating high concentration organic wastewater are treated on the pilot-scale apparatus, its design, manufacture and installation are completed by ourselves, and the high color removal and degrading efficiencies are obtained, and the biodegradabilities of real organic wastewaters are also improved.Based on energy balance calculation, microwave assisted catalytic wet air oxidation process adapts to treat high concentration organic wastewater. Increasing efficiencies of microwave energy utilization and heat exchanger can reduce the economical cost evidently, and increase the possibility of its practical application.
|
PDF Full Text Request