Method of separating mercury from an ore leachate
Described herein are compositions and methods for preferentially separating mercury from a metal product where both are present in an ore leachate. The separation is accomplished by adding a precipitating agent and a coagulant to an ore leachate followed by separating a mercury-laden precipitate therefrom to collect the treated leachate. The treated leachate includes about 0 to 50% by weight of the mercury and about 90% to 100% by weight of the metal product present in the ore leachate. In embodiments, the method further includes adding a flocculant to the ore leachate prior to the separating of the mercury-laden precipitate.
1. A method of making a treated gold ore leachate, the method comprising
contacting a gold-bearing ore with a sodium cyanide solution at a pH of 9 or greater to form a gold ore leachate, the gold ore leachate comprising gold and mercury;
adding a precipitating agent and a coagulant to the gold ore leachate to form a partitioned composition, the precipitating agent comprising a dithiocarbamate polymer that is a water-soluble ethylene dichloride ammonia polymer having a weight-average molecular weight of about 5000 g/mol and about 50 mole % dithiocarbamate salt groups, the coagulant consisting essentially of Fe 2 (SO 4 ) 3 ; and
separating a mercury-laden precipitate from the partitioned composition to form the treated ore leachate, the mercury-laden precipitate comprising about 50% to about 100% by weight of the mercury and about 0% to about 10% of the gold present in the gold ore leachate.
2. The method of claim 1 wherein the method further comprises adding a flocculant to the partitioned composition.
3. The method of claim 1 comprising adding the precipitating agent and the coagulant contemporaneously.
4. The method of claim 1 comprising adding the precipitating agent before adding the coagulant.
5. The method of claim 1 wherein the ratio of precipitating agent to coagulant added is 5:1 to 1:5 by weight.
6. The method of claim 1 comprising adding the precipitating agent to the gold ore leachate at about 1 ppm to 50 ppm per 2000 μg/l of mercury.
7. A composition consisting essentially of
a gold ore leachate formed by contacting a gold-bearing ore with a sodium cyanide solution at a pH of 9 or greater;
a precipitating agent that is a water-soluble ethylene dichloride ammonia polymer having a weight-average molecular weight of about 5000 g/mol and about 50 mole % dithiocarbamate salt groups;
a coagulant that is Fe 2 (SO 4 ) 3 ;
optionally a flocculant; and
optionally a trithiocarbonate,
wherein the weight ratio of precipitating agent:coagulant in the composition is about 5:1 to 1:5.
8. The composition of claim 7 wherein the flocculant is a neutralized or partially neutralized polymer comprising about 10 mole % to 100 mole % of repeat units attributable to acrylic acid or a sulfonic acid functional monomer.
9. The composition of claim 7 wherein the trithiocarbonate is water soluble and comprises alkali metal, alkaline earth metal, ammonium, alkylammonium, or hydroxyalkylammonium.