Chemical Oxidation of Thiocyanate Ion by Ozone

Thiocyanate ion and weak ammonia liquor from a coking operation were ozonated in a semi-batch reactor. In a typical case, 500 mg/L thiocyanate ion disappeared in 8 minutes using an ozone dose of 82 mg/min at pH 7. The cyanide ion concentration was maximized immediately after the thiocyanate ion disappeared. The ozone-to-thiocyanate ion stoichiometric molar ratio was found to be 2.0 ± 0.2. The rate constants for the reaction of thiocyanate ion and cyanide ion with ozone under the typical conditions listed above were 5.4×104 L2/(mmole2-min) and 1.5 L/[mmole-min], respectively.