Destruction of environmental organic pollutants by supercritical water oxidation

The supercritical water oxidation of two environmental pollutants in the form of diesel fuel and two waste landfill leachate samples have been examined in relation to sub-critical and supercritical water oxidation conditions. Supercritical water oxidation involves reactions in an aqueous fluid phase under conditions below and around the critical point of water (T_c = 374 °C, P_c = 22.1 MPa). Experiments were carried out using a batch autoclave reactor at temperatures between 300 °C and 380 °C corresponding to pressures between 10.5 MPa and 22.8 MPa. The oxidative decomposition of the diesel fuel, which was loaded onto a sand matrix to simulate a contaminated land sample, was determined in relation to process conditions. The results showed that almost complete destruction of the components of the diesel fuel could be achieved. In addition, intermediate oxygenated compounds were formed and identified. The level of loading of the diesel fuel onto the sand matrix influenced the level of compound decomposition and the amount of intermediate oxygenated compounds formed. The characteristics of the waste landfill leachates were determined and were shown to be highly chemically complex. The high chloride concentration of the leachate resulted in significant corrosion of the reactor. However, almost complete oxidation of the organic components of the leachate could be achieved under supercritical water oxidation conditions.