Decomposition of Thiocyanate Ion by Sub- and Supercritical Water Oxidation

For the purpose of stable supply of energy while decreasing dependence of fossil fuels in the future, both clean coal technologies and environment load reduction technologies are extremely required to develop. For the development of clean-up system of sulfur-containing wastes from coal devoletilization process in coke oven, decomposition experiments of a thiocyanic ion, SCN-, in sub- and supercritical water were examined with oxygen and hydrogen peroxide as oxidizers at temperatures from 25 to 400 °C and at 25 MPa by a flow-through reactor. High-temperature water treatment in the presence of oxygen with O2/SCN- molar rario of 75 led to about 40 % decomposition of SCN- for 30 s at 350 °C. In contrast, the treatment in the presence of hydrogen peroxide with O2/SCN- molar rario of 30 led to complete decomposition of SCN- for 30 s at 200 °C. It was found that decomposition ratio of SCN- could be much improved with hydrogen peroxide as a oxidizer. These results show the clean-up system of sulfur-containing wastes can be made compact using sub- and supercritical water oxidation techniques.