Removal of Hg from NaOH with Photoreuction plus Air Purging

摘要

Industry is replete with alkaline solutions which are contaminated by Hg. Examples include caustic soda (NaOH) produced by the Hg-cell process, Bayer Process (aluminum extraction) liquor, nuclear fuel processing wastes, and waste streams from petroleum refining. Fig is undesirable because of environmental degradation, occupational health and safety, and the risk of amalgamation with, and weakening of, tanks, pipes, or hardware. We investigated several potential candidates for the removal of Hg from these alkaline solutions, including (a) chemical or UV photo-reduction and purging of Hg~deg at elevated temperatures, (b) amalgamation with colloidal silver followed by filtration, (c) extraction on an immobilized gold substrate, and (d) coprecipitation with sodium carbonate. The most promising option appears to be photo-reduction, and purging out the Hg~0.