Recuperation of the Gold and Silver

The bulk concentrate and the mortar were cyanized, some previously lixiviated with H2SO4 and in the following conditions:

Acid Washing Conditions

• Granulometry             100% - 100 m.
• Solid/liquid relation         1/3
• pH (H2SO4)               1.8 to 2.0
• Time                     2 hours

Conditions of the Cyanidation

• Granulometry                Variable
• Time                       Variable
• Concentration NaCN          0.1 to 0.3%
• pH (lime)                   10.5
• Solid/liquid relation           1/3

Conclusions and Recommendations
- The elimination of the As and Sb is feasible and efficient in the bulk concentrate by means of the process of selective reduction toasting.

The loss of weight of the toasted material, for the elimination of contaminants, has an average of 32.12%.

- The oxidant toasting after the reductory toasting compliments the elimination of sulphur until 61.20%.

- Of the analysis of the conditions of work of the selective toasting at an pilot bach oven level it infers as the most favorable, where the variable of the most influence in the rating of heating.

- It is necessary to perform the most number of tests for the better study of the different variables such as:

• Rate of heating;
• Work temperature;
• Atmosphere.

- Effectuated the tests of cyanidation with the mortars it is concluded that: it is necessary to lixiviate previously the mortar with sulphuric acid sollutions, with the intention of dissolving substances which cover the surface of gold and eliminate cyanicide agents.

Of the test of cyanidation effectuated, being the extraction of gold of 68% and that of silver 56%.

The consumption of reactives of cyanidation is of 16.5 kilograms/TM of sodium cyanide and3.5 kilograms/TM of lime.

In the case of the process of cyanidation it is also necessary to perform some tests with the intention of optimizing the efficiency of the extraction of precious metals and minimizing the consumption of reactives.