WIT Press

Application Of Sub And Supercritical Water Technology For Waste Management


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WIT Press


S Urano, N Sato, H Daimon & K Fujie


A novel application of sub- and supercritical water technology for treatment of industrial waste was investigated. The technology has been used for degradation of hazardous materials like PCBs (Poly Chlorinated Biphenyls). In this research, it was applied for resource recovery of industrial wastes at relatively mild condition. The adopted wastes were waste casting sand, aluminum dross ash and carbon fiber reinforced plastics. Waste casting sand discharged from casting process is covered with burned adhesives. The sand is presently treated from the view point of environmental effect and disposal cost, however, the treatment involves the problems, inferior working condition by dust and recycled sand quality caused by remaining carbon and nitrogen. As a result of the treatment, sufficient removal of remaining organic carbon and nitrogen on the sand surface was obtained. Furthermore, improvement of surface acidity was achieved by the reaction. In the treatment of aluminum nitride, one of hazardous chemical in aluminum dross ash discharged from aluminum industry, was examined for the purpose of nitrogen removal and clarifying the relationship of reaction condition and removal rate. The results indicated that about 90 % of nitrogen in aluminum nitride was removed at the condition of 200 "C, 10 min. An optimum ratio between water and sample was also examined. Carbon fiber reinforced plastics (CFRP) has been used in various products such as sports goods, airplane wing, fishing rod among others. Recycle of CFRP is pretty difficult caused by its high intensity and heat resistance. By using semi-batch reactor, thermoset plastic was removed and recovered recyclable quality carbon fiber around 380 "C. In addition, it was indicated that the treatment could rearrange the surface property of carbon fiber. The results suggest a feasibility of the technology not only for decomposition of hazardous chemicals.