| abstract |
A method of extracting metal ions from an aqueous solution which comprises a chelated metal-ligand complex, the method comprises the steps of: (a) reacting the metal-ligand complex at a temperature of at least 60 °C with a persulfate oxidant to decompose the chelating agent and thereby release the metal ions from the metal-ligand complex; (b) raising the pH of the solution to precipitate the metal ions in the form of a metal oxide or metal oxyhydroxide; and (c) separating the metal oxide or metal oxyhydroxide precipitate from the solution. Preferably, the persulfate oxidant is peroxomonosulfuric acid, peroxodisulfuric acid, a peroxomonosulfate salt, a peroxodisulfate salt or a mixture of two or more thereof. The chelating agent can be a citrate, gluconate, tartrate, malonate or ethylenediaminetetraacetic acid (EDTA). The metal ions may comprise cobalt, copper, nickel, chromium, manganese, zinc, cadmium, mercury or lead. The aqueous solution can comprise wastewater generated from electroplating or electronic circuit board manufacturing. The separation step (c) may be carried out by sedimentation and/or filtration. |