1992-05-04_REVISION - M1988112 ‎(3)‎

• Permit No: M1988112
• IBM Index Class Name: Revision
• Doc Date: 5/4/1992
• Doc Name: CYANIDE DESTRUCTION THE INCO SO2 AIR PROCESS
• Type & Sequence: TR6
• Media Type: D
• Archive: No

CYANIDE POLLUTION CONTROL -THE INCO PROCESS
E.A. Dewyst & G. Robbins
A unique process for removing cyanide and base metal
complexes from industrial waste streams was patented by GJ,
Borberly et a1 (1984). The process uses SOz (liquid or gas, or
solutions of sulfite salts, or from burning elemental sulfur), plus
air that is dispersed in the effluent using a well agitated vessel
Acid produced in the oxidation reactions is neutralized
with lime at a controlled pH generally in the range 7 to 10. The
reaction requires the presence of soluble copper as a catalyst
which can be supplemented by copper sulfate if necessary.
The process can be applied to the detoxification of gold
and silver mining waste streams, such as carbon-in-pulp (CJP)
tailing pulps, barren solution bleeds, pond wader, and heap leach
rinse solutions and also to plating shops wastewaters.
The SO~/Arr process has substantial advantages over two
of the main alternative methods of cyanide destruction, namely
alkaline chlorination and hydrogen peroxide.
Alkaline chlorination is highly penalized in terms of
reagent consumption. Chlorine is a strong oxidant reacting with
species other than cyanide present in the effluent such as
thiocyanate and sulfides. Furthermore alkaline chlorination is
an incomplete detoxification process. Iron cyanide is not
removed and the potential for harmful by-products species exist.
Consequently final effluents may be subject to additional
treatment in order to comply with regulatory demands.
Hydrogen peroxide is selective for cyanide in solutions,
but is an extremely expensive reagent which, in many cases
decomposes rapidly in the presence of solids. This may lead to
high reagent consumpdonand/or incomplete cyanide destruction.
The Inco SO~/Air process is selective for total cyanide
detoxification, including iron cyanide which is removed as a
precipitate, uses safe, low-cost reagents. It is therefore, the most