Principle process for enriching gold and silver from sand ore and primary ore

The method of enriching gold and silver from sand ore and primary ore is mainly based on the characteristics of deposit type, mineral structure, morphology and symbiotic combination. The enrichment methods commonly used in different deposits are:

First, the gold deposit. The natural gold of a good sand deposit is separated from the gangue, and the dissociation of gold particles is present in the gravel. However, only a small amount of gold particles in the slope or alluvial deposits have been dissociated from the gangue and need to be broken first. These ores are usually pretreated, and the concentrates are produced by re-election, and then treated by amalgamation or cyanidation (or by first mixing mercury to capture coarse gold and then cyanidation).

Second, the monomeric natural gold embedded in the quartz vein, usually the ore is broken and directly treated by re-election method, amalgamation method or cyanidation method.

Third, natural disseminated gold iron sulfide (pyrite, arsenopyrite or pyrrhotite) in, or antimony, arsenic, copper, nickel, gold intergrowth or in the presence of gold telluride, usually after the first flotation And calcination, and then the resulting concentrate or calcine is treated by cyanidation. If the ore is secondary copper sulfide, barium sulfide and gold are present in the carbonaceous shale , if it is difficult to use the cyanidation process, the concentrate is treated by other methods after flotation and the tailings are treated by cyanidation.

4. A small amount of gold co-existing with iron, copper and nickel sulfide deposits is embedded in the crystal lattice of these sulfide minerals. Such ores are mainly produced from copper and nickel. The ore obtained by flotation is sent to the smelting plant for treatment, and the gold and silver are comprehensively recovered while producing copper and nickel. Gold and silver in these ores increase the total value of the deposit.

5. From a mineralogical point of view, gold and silver are often symbiotic with each other in nature, or in the form of natural alloys. For example, the composition of natural gold often contains 0 to 30% of silver in addition to gold. Given that silver is symbiotic or associated with gold and other minerals: “single” silver deposits are only dominated by silver. Therefore, the method of enriching silver from silver ore should generally consider recovering other minerals that are symbiotic or associated with it. Generally speaking, the recovery of silver from copper, lead , zinc and other ores is mainly based on flotation, and the well is supplemented by other methods. The silver in the gold ore can be enriched by a method similar to the recovery of gold, recovered as an alloy, and then separated and purified; sometimes it is separated and then separately purified. Platinum group metals and gold are often associated with commensal or may be comprehensive recovery processing. The silver-containing sulfide is usually calcined by oxidation, then cyanated, or leached with acidic brine or sodium thiosulfate.

6. Silver-containing manganese sulfide and silver-containing soft manganese deposits. Due to the presence of manganese, the direct use of cyanide leaching is not good, and other methods are also difficult. For this reason, special treatment is usually carried out so as not to affect the leaching of silver.

The Caron method for treating silver-containing pyrolusite is to introduce sulfur dioxide into the cyanide slurry to reduce MnO ₂ . In the process, additional lime is needed to neutralize the mineral acid and precipitate together with the reduced manganese to enhance the cyanide leaching of the silver. It is economical to use a Karen method to treat silver ores with low MnO ₂ , but when the MnO ₂ content is high, the cost of adding SO ₂ and lime is carefully calculated through production experiments.

The treatment of silver-bearing manganese sulfide ore is produced in Peru by flotation. The process of recovering silver from concentrate is to first leaching manganese with dilute sulfuric acid. The H ₂ S produced in the process oxidizes it to SO ₂ and then absorbs the lye in the scrubber to produce the Na ₂ S supply market. The leached manganese sulfate liquid is produced by electrolysis to produce high quality manganese.

The principle processes for enriching gold and silver from various gold and silver ores are listed in Tables 1 and 2.

Table 1 Principle process for processing gold ore

Table 2 Main silver minerals and suitable method for metallurgy