Differential flotation of sulfide ores for recovering refractory gold

1. A process for recovery of gold from gold-containing raw materials comprising refractory gold-containing minerals, in particular gold-containing refractory sulfidic minerals, comprising:

(a) obtaining gold-containing raw material comprising refractory gold-containing sulfidic minerals comprising a first type of refractory sulfidic mineral having high gold content and a second type of sulfidic mineral having low gold content, the first type and the second type of sulfidic minerals are to be classified within a single type of refractory sulfidic minerals, wherein the gold-containing raw material comprises silicates in addition to the gold bearing minerals;

(b) forming a mineral pulp comprising the first type of refractory sulfidic mineral particles having high gold content and the second type of sulfidic mineral particles having low gold content by suspending ground gold-containing material in water and optionally further milling the material;

(c) conditioning the mineral pulp by addition of a surface modifying chemical for modifying the surface of the first type of refractory sulfidic mineral particles having high content thus making the particles non-floatable to obtain a conditioned pulp;

(d) subjecting the conditioned pulp to a froth flotation process to separate the first type of refractory sulfidic mineral particles having high gold content from the second type of sulfidic mineral particles having low gold content;

(e) recovering the non-floatable first type of refractory sulfidic mineral particles having high gold content as flotation tailings;

(f) pressuring oxidizing (POX) the flotation tailing recovered in step (e) to obtain a discharge slurry comprising liberated gold; and

(g) recovering gold from the discharge slurry obtained in step (f),

wherein the silicates are removed from the mineral pulp subsequent to the mineral flotation process (d) and prior to the pressure oxidizing process (f) by silicate flotation.

2. The processes as claimed in claim 1 , wherein the gold-containing material comprising refractory gold-containing minerals has a gold recovery rate less than 80% when subjected to direct cyanidation.

3. The process as claimed in claim 1 , wherein the refractory gold-containing material comprises gold locking or cyanide consuming materials such as iron sulphides, arsenic sulphides, copper sulphides, antimony sulfides, tellurides, elemental sulphur, or any mixture thereof.

4. The process as claimed in claim 1 , wherein the gold content of the first type of refractory sulfidic mineral having high gold content is above 5 ppm.

5. The process as claimed in claim 4 , wherein the gold content of the first type of refractory sulfidic mineral having high gold content is above 8 ppm.

6. The process as claimed in claim 4 , wherein the gold content of the first type of refractory sulfidic mineral having high gold content is between 10 to 100 ppm.

7. The process as claimed in claim 1 , wherein the gold content of the second type of refractory sulfidic mineral having low gold content is below 5 ppm.

8. The process as claimed in claim 7 , wherein the gold content of the second type of refractory sulfidic mineral having low gold content is below 1 ppm.

9. The process as claimed in claim 7 , wherein the gold content of the second type of refractory sulfidic mineral having low gold content is below 0.1 ppm.

10. The process as claimed in claim 1 , wherein the surface modifying chemical is selected from a group consisting of nitrogen, oxidizing agents, reducing agents, complexing agents and any mixtures thereof.

11. The process as claimed in claim 10 , wherein the surface modifying chemical is an oxidizing agent.

12. The process as claimed in claim 11 , wherein the oxidizing agent is selected from a group consisting of hydrogen peroxide, oxygen, ozone and alkali permanganate, chlorine, bromine, sulfuric acid, and any mixtures thereof.

13. The process as claimed in claim 10 , wherein the surface modifying chemical is a reducing agent.

14. The process as claimed in claim 13 , wherein the reducing agent is selected from a group consisting of hydrogen, carbon monoxide, sodium sulphide, sodium hydrosulfide, sodium dithionite, sulfur dioxide, ferrous sulphate, Fe powder, Zn powder, and any mixtures thereof.

15. The process as claimed in claim 10 , wherein the surface modifying chemical is a complexing agent.

16. The process as claimed in claim 15 , wherein the complexing agent is selected from a group consisting of ethylenediaminetetra-acetic acid (EDTA), diethylenetriamine (DETA), alkali cyanide, ammonia, alkali chloride, and any mixtures thereof.

17. The process as claimed in claim 15 , wherein the amount of the surface modifying chemical is 50 to 500 g/t of treated ore.