the present invention relates to water - soluble polymers and the use of such water - soluble polymers in a process for the displacement of the cyanide ions from the metal ions within metal - cyanide complexes . the process waste streams can include metal - cyanide containing electroplating waste streams , mining leach waste streams , mineral processing waste streams , and related metal - cyanide containing waste streams . the metal ions of interest are metals that give very strong complexes with cyanide , mostly iron , nickel , and copper . the physical separation of the water - soluble polymer - metal complex from the cyanide ions can be accomplished through the use of ultrafiltration . once the metal - cyanide complex is disrupted , the freed cyanide ions can be recovered for reuse or destroyed using available oxidative processes rendering the cyanide nonhazardous . the metal ions are released from the polymer , using dilute acid , metal ion oxidation state adjustment , or competing chelating agents , and collected and recovered or disposed of by appropriate waste management techniques . the water - soluble polymer can then be recycled . preferred water - soluble polymers include polyethyleneimine and polyethyleneimine having a catechol or hydroxamate group .