Method for extracting gold and silver

Abstract

The invention relates to a method for extracting gold and silver, comprising the following steps of: mixing pulp by using barren solution after flotation concentrate, adding sodium cyanide and lime, grinding ores in a ball grinding mill, grading the ores discharged by the ball grinding mill by using a swirler, and returning the ball grinding machine for regrinding the graded ores and settled sand; washing and concentrating the graded overflow by using a thickener, leaching a bottom flow, continuously adding the sodium cyanide and the lime for leaching, and washing cyanogen slag to be sold as sulfur concentrate; forming a precious solution by using overflow water of the thickener, purifying the precious solution, deoxidizing the precious solution, replacing gold and silver by zinc powder to form the barren solution, and making the barren solution return as flotation concentrate pulp-mixing water and washing water. The method for extracting gold and silver is characterized in that in an ore-grinding process, oxygen is introduced to the ball grinding mill, the concentration of the oxygen in the ball grinding mill is improved with the enlargement (destroy of a coated film) of the ore grain grinding degree and the explosion of gold and silver grains, the concentration ratio of a cyanogen radical to the oxygen approaches to the optimum value in a milling-strengthening process, the concentration of the oxygen during grinding and leaching is kept above 5 mg / L, the [CN] is kept at 2,500-3,500 mg / L, and the concentration ratio of the [CN] to the [O] is 500-700. The method realizes oxygen enrichment cyaniding, leaching and ore grinding by filling pure oxygen in the ball grinding mill and improves the leaching rate of gold and silver ore grinding, thereby improving the gold and silver cyaniding recovery rate, reducing the grade of cyanogen slag and obtaining a better economic technical index.

Description

technical field [0001] The invention relates to a method for extracting gold and silver, in particular to a method for extracting gold and silver from ores or beneficiation products by using a cyanide leaching method. Background technique: [0002] As we all know, there are many methods for extracting gold and silver, but the cyanide leaching method is still the main method at present. 2 and H 2 The combined action of O forms a water-soluble gold (silver) cyanide complex [Au(CN) - 2 ]([Ag(CN) - 2 ]) process, namely 2Au+4NaCN+? o 2 +H 2 O=2NaAu(CN) 2 +2NaOH, in the cyanide leaching process, the dissolution rate of gold and silver depends on both the concentration of cyanide and the concentration of oxygen. In a certain temperature range, [CN] / [O 2 ]=600 (unit: mg / L), the dissolution rate of gold and silver can reach the limit value, and the leaching effect is the best, and it is impossible to increase the dissolution rate of gold and silver by increasing one of the c...

AI Technical Summary

Problems solved by technology

[0003] At present, in the cyanide leaching process of gold mines while grinding and leaching, the method of filling the leaching tank with air or pure oxygen is used to provide oxygen. The oxygen content is low, especially in the grinding process, the oxygen consumption is large, the oxygen in the ball mill discharge liquid is less than 1.2mg / L (dissolved oxygen in the normal leaching process is above 8mg / L), and the concentration of sodium cyanide is 3100mg / L L, [CN] / [O 2 ] The ratio is much higher than the optimal value, the gold leaching rate of grinding and leaching is only about 70%, and the silver leaching rate is lower than 50%.

In order to achieve a high gold and silver leaching rate, leaching equipment is often added in the follow-up process to prolong the leaching time and reduce the gold and silver grades of cyanide slag, which will not only increase equipment investment, but also increase power consumption and increase production costs.