Process for the treatment of metal-containing water and recovery of metals therefrom

摘要

Metals contained in various wastewaters are selectively recovered as metal precipitates and/or as spinel ferrite and water suitable for discharge into the environment is obtained. High grade magnetic spinel ferrite is recovered from wastewaters having aluminum and arsenic if present in the wastewater, removed from the wastewater. There are three process stages for the treatment of wastewater. In the first process stage which is optional, at least a portion of at least one non-ferrous or non-ferric metal is precipitated from the wastewater by subjecting the wastewater to an oxidizing agent to increase the oxidation-reduction potential of the water, by adjusting the pH of the wastewater to a pH at which the metal precipitates from the water and by adding an organic or inorganic sulfur compound, capable of causing the metal to form a precipitate, to the water in a quantity sufficient to precipitate the metal. When aluminum is present in the wastewater, aluminum is recovered from the water by adding a reducing agent to lower the oxidation-reduction potential of the water and by adjusting the pH of the water to about 5. The aluminum which precipitates in the aqueous solution, is removed from the water. In the third precipitation stage, iron is recovered as spinel ferrite in an ambient temperature process by adding a reducing agent to the water, adding a soluble ferrous salt to the water, adjusting the pH to about 9-12 and oxidizing the water with an oxidizer, e.g., air, to form spinel ferrite. If aluminum and/or arsenic are present in the wastewater and are removed from the wastewater by the process, high grade magnetic spinel ferrite is recovered.