Cyanide waste may be destroyed by the use of which chemical?

• A. Chlorine
• B. Sulfamic acid
• C. Ozone
• D. Hydrogen peroxide

Answer: (A)

Cyanide waste is treated by oxidizing the cyanide ions (CN−) to a less toxic form, cyanate (OCN−). Chlorine is a strong, readily available oxidant that rapidly converts CN− to OCN− in water, especially under alkaline conditions used in wastewater treatment. The reaction provides a practical pathway to neutralize cyanide: CN− plus chlorine and water yields cyanate and chloride and protons, and under basic pH the cyanate remains stable and easier to handle. Chlorine is favored in industry because it’s inexpensive, widely available, and effective at typical treatment pH levels. While other oxidants like ozone or hydrogen peroxide can also destroy cyanide by forming cyanate, chlorine’s combination of speed, cost, and practicality makes it the common choice. Sulfamic acid isn’t an oxidant, so it doesn’t serve this destruction role.