What chemical is commonly added to remove cyanide from metal waste streams?

The addition of bleach, which contains sodium hypochlorite, is a common method for removing cyanide from metal waste streams. The reaction involves the oxidation of cyanide ions to form non-toxic compounds, typically cyanate or carbon dioxide and nitrogen, depending on the conditions. Bleach is effective due to its strong oxidizing properties, which facilitate this transformation. Proper use of bleach in a controlled environment allows for effective detoxification of hazardous cyanide compounds in industrial effluents.

In contrast, ammonia, hydrogen peroxide, and formaldehyde do not serve the same function in the treatment of cyanide. Ammonia can complicate waste treatment processes, particularly if ammonium ions interfere with biological treatment methods. Hydrogen peroxide could potentially oxidize cyanide as well, but it is not as widely used or effective in this specific context compared to bleach. Formaldehyde is not a suitable choice for cyanide treatment and can introduce additional toxicity. Thus, bleach is recognized as the appropriate agent for this purpose in wastewater management practices.