Which of the following is not a common method for the treatment of cyanide in wastewater?

Filtration is not a common method for the treatment of cyanide in wastewater because its primary function is to physically remove particles or suspended solids from a liquid rather than chemically transforming or neutralizing contaminants. Cyanide treatment typically focuses on processes that alter or eliminate the toxic properties of the cyanide compound rather than just separating it from the water.

Oxidation is frequently used in cyanide treatment, often involving agents like chlorine or hydrogen peroxide, which convert cyanide into less harmful compounds. Reduction processes can also be utilized to convert cyanide into more benign substances, often through chemical reactions that involve transferring electrons. Neutralization might apply in some scenarios where pH adjustment can help decrease toxicity, although this is not as direct as oxidation or reduction.

Therefore, filtration does not effectively address the chemical nature of cyanide in wastewater or render it harmless, making it the least applicable method among the options provided.