Use of Ozone in the Treatment of Cyanide Containing Effluents

This technical paper reviews the use of ozone in the treatment of cyanide-containing effluents from gold and silver processing. The document explains that ozone is a powerful oxidant that can rapidly oxidize free cyanide, copper-cyanide complexes, and thiocyanate under the right conditions, making it a promising option for industrial wastewater treatment. The study highlights practical advantages of ozone such as onsite generation, reduced chemical handling, simple operation, and fast oxidation performance compared with some conventional treatment methods.

For process performance, the paper shows that alkaline pH is critical for effective cyanide oxidation with ozone. In alkaline solution, cyanide can be completely oxidized, while at pH below 9 the reaction becomes ineffective because cyanide converts to hydrocyanic acid (HCN), which is not readily oxidized by ozone. The study also indicates that the ozone addition rate directly affects treatment time, while initial cyanide concentration mainly affects how long treatment takes rather than the oxidation rate itself. Temperature had little effect in the tested range, and the presence of copper above about 80 mg/L helped reduce ozone consumption and treatment time.

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