Removal of complexed heavy metals from waste effluents

A method of treating a waste solution containing heavy metals tightly bound by one or more complexing agents selected from the group consisting of EDTA, NTA and thiosulfate to separate and recover the heavy metals and reduce pollution of streams by the heavy metals, said method comprising contacting the waste solution with a synergistic mixture of peroxide and ozone to oxidize and destroy the complexing agents, precipitating the heavy metals from the thus treated solution, and separating the insoluble heavy metal precipitates from waste solution to permit recovery of the valuable metal content thereof and to leave the waste solution substantially free of the heavy metals.

A continuous method for the treatment of waste solutions which contain heavy metals tightly bound by one or more complexing agents selected from the group consisting of EDTA, NTA and thiosulfate to recover the heavy metals and reduce pollution of streams by the heavy metals, said method comprising directing the waste solution containing the heavy metal complexes into a reaction vessel and introducing hydrogen peroxide into the reaction vessel and into contact with the waste solution while also bubbling ozone through the waste solution to oxidize and destroy the complexing agents and convert the heavy metals into a readily separable form, directing the solution from the reaction vessel to a causticizing vessel and introducing a causticizing agent to raise the pH of the solution to at least about 12 and precipitate some of the heavy metals as insoluble heavy metal oxides and hydroxides, directing the solution from the causticizing vessel to a polishing vessel and introducing sodium sulfide into the solution to bring about additional precipitation of the heavy metals as heavy metal sulfides, directing the solution and insoluble precipitates from the polishing vessel and separating the insoluble heavy metal precipitates from the waste solution leaving the solution substantially free from the heavy metals.