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 composition comprising a mixture of:
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; and
a sulfide compound selected from dithiocarbamate compounds, trithiocarbonate compounds, hydrogen sulfide, calcium hydrogen sulfide, sodium hydrogen sulfide, trimercapto-S-triazine, silver sulfide, ferric sulfide, or a combination thereof.
2. The composition of claim 1 wherein the sulfide compound comprises a dithiocarbamate compound having the formula
wherein R 1 and R 2 are independently C 1 -C 4 alkyl, branched alkyl or alkenyl and X is sodium or potassium.
3. The composition of claim 2 wherein both R 1 and R 2 are methyl.
4. The composition of claim 1 wherein the sulfide compound comprises a water soluble trithiocarbonate compound comprising an alkali metal, an alkaline earth metal, ammonium, an alkylammonium, a hydroxyalkylammonium, or a combination thereof.
5. The composition of claim 1 further comprising a coagulant, the coagulant comprising Fe 3+ , Al 3+ , or a combination thereof.
6. The composition of claim 5 wherein the coagulant comprises a counterion selected from sulfate, halide, halohydrate, or a combination thereof.
7. The composition of claim 6 wherein the coagulant is selected from Fe 2 (SO 4 ) 3 , Al 2 (SO 4 ) 3 , FeCl 3 , AlCl 3 , aluminum chlorohydrate, polyaluminum chloride, or a combination thereof.
8. The composition of claim 5 wherein the weight ratio of polymer:coagulant in the composition is about 5:1 to 1:5.
9. The composition of claim 1 further comprising a flocculant, the flocculant comprising a polymer comprising about 10 mole % to 100 mole % of repeat units attributable to a conjugate base of acrylic acid, a conjugate base of a sulfonic acid functional monomer, or a combination thereof.
10. A method of forming a treated ore leachate comprising:
adding a precipitating agent to a gold ore leachate;
adding a coagulant to the gold ore leachate; and
separating a mercury-laden precipitate therefrom to provide the treated ore leachate, wherein the precipitating agent comprises a mixture of: 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; and a sulfide compound selected from dithiocarbamate compounds, trithiocarbonate compounds, hydrogen sulfide, calcium hydrogen sulfide, sodium hydrogen sulfide, trimercapto-S-triazine, silver sulfide, ferric sulfide, or a combination thereof, and wherein the coagulant is selected from Fe 2 (SO 4 ) 3 , Al 2 (SO 4 ) 3 , FeCl 3 , AlCl 3 , aluminum chlorohydrate, polyaluminum chloride, or a combination thereof.
11. The method of claim 10 further comprising adding a flocculant to the ore leachate prior to the separating.
12. The method of claim 11 wherein the adding is carried out contemporaneously.
13. The method of claim 11 wherein the adding is carried out sequentially in the order: precipitating agent; coagulant; and optionally flocculant.
14. The method of claim 13 wherein each addition is followed by a period of about 1 second to 10 hours prior to the subsequent addition.
15. The method of claim 10 wherein the separating is sedimentation/decanting, filtration, or flotation.