Sequential separation of metals by controlled pH precipitation

摘要

A process for separately removing zinc and iron from acidic wastewater. The process involves adding alkali metal hydroxide to the acidic wastewater (below about pH 4) to achieve a first pH of about 4.8 to at most about 5.4 and precipitate an iron hydroxide-containing precipitate at this pH. The precipitate from the wastewater is separated and then additional alkali metal hydroxide is added to achieve a second pH in the range from about 8.8 to about 9.4. A zinc hydroxide containing precipitate forms at this second pH and is then recovered by filtration.