Sub- and supercritical water oxidation are quite new techniques for wastewater treatment. Temperatures must be high enough and reaction times long enough that the organic compounds are completely oxidized into carbon dioxide and water. Thecritical temperature and pressure of water are 374℃ and 22.1 MPa. The primary aim of the study was to determine whether potassium persulfate is a feasible choice for oxidant in work clearly below the critical temperature of water. Because potassiumpersulfate is water soluble, it can be added directly to water containing organic compounds. Simple equipment was constructed for oxidation in high-temperature pressurized water, and oxidation of phenol, 2,3-dichlorophenol, and 1-naphthol was carried outin aqueous environment at 75340℃ with potassium persulfate used as oxidant. The pressure was adjusted to 25-45 MPa. The concentration of the organic compounds was 1.0 mM, and that of the oxidant was 1.0-10.0 mM. Study was made of the effects ofconcentration, temperature, and reaction time on oxidation efficiency. The removal percentages of phenol were good even at 115℃. Concentration of the oxidant turned out to be a very important parameter. Also temperature and reaction time had an effect on the results. There were some problems arising from the formation of rust and from blockage of the capillaries of the equipment. However, the blockage could be prevented with use of a precipitant collector.
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