Mineral Processing

silver Processing

At present, the proven reserves of silver ores are divided into two parts, one is silver ores with silver grades that meet industrial indicators with independent mining value, and the other refers to associated silver ores with silver grades lower than industrial indicators.

Main types of silver ore

Silver-bearing ores are mainly divided into gold-silver ores and lead-zinc-copper associated silver ores. Their silver production accounts for more than 99% of the total output.

Silver-gold ore
Apart from gold, gold-silver ore also contains tens of grams to hundreds of grams of silver per ton of ore.
Silver ores often coexist closely with clay minerals, iron oxide and manganese oxide. Natural silver particles are often covered by some metal oxide and hydroxide films. Gold minerals exist in the form of natural gold and silver gold, and the gold particles are very fine.

Lead Zinc Copper Associated Silver Ore
Silver in lead-zinc-copper associated silver ore mainly exists in the form of independent silver minerals. Various compounds of silver and sulfur, copper, lead, tin, antimony, tellurium, selenium, arsenic and other elements appear in various deposits:

Various silver minerals closely coexist with lead, zinc, copper and other sulfide minerals, and most of them are fine-grained. The particle size is almost below 0.04 mm, the particle size of most silver minerals is 0.04-0.02 mm, and the finest is only 0.001 mm. The fine-grained silver minerals are distributed in galena, sphalerite and copper sulfide minerals in the form of contiguous bodies, inclusions, and micro bodies.

In the flotation process, those sulfide minerals that are closely related to silver minerals will become their carriers, enriching silver into various concentrate products. Therefore, the occurrence state and inlay characteristics of silver minerals have a significant impact on the comprehensive recovery of silver.

Silver ore processing

There are many types of silver in silver-gold ore, and they often appear in various states, so the joint process is often used to deal with gold-silver mines. In general, beneficiation methods of silver-gold ore mainly include flotation or cyanidation. But these two methods of silver separation mainly depend on the composition of silver minerals.
When silver minerals are dominated by sphalerite and natural silver, flotation and cyanidation are both acceptable; when the ore contains a large amount of dark red silver, light red silver, selenium silver and other difficult cyanide minerals, it is only available flotation method.

It should be noted that there is a difference in recovery rate between the flotation method and the cyanidation method. Generally, the recovery rate of the cyanidation method is higher than that of the flotation method.
The common gold and silver ore beneficiation process flow is as follows:

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1. Flotation-cyanidation
The sulfide ore containing gold and silver quartz veins is subjected to flotation to obtain a small amount of concentrate, which is then cyanidated. Compared with the whole mud cyanidation process, the flotation concentrate cyanidation has the advantages of not requiring fine grinding of all ores, saving power consumption, small plant area, and saving capital investment.

2. Flotation-roasting-cyanation
This process is commonly used to process insoluble gold-arsenic ore, gold-antimony ore, and gold-pyrite with extremely high sulfide content. The purpose of roasting is to remove arsenic, antimony and other elements that are harmful to the cyanation process.

3. Flotation-fire treatment
The vast majority of polymetallic sulfide ores containing gold and silver are treated in this way. During flotation, gold and silver enter the copper and lead gold mines that are close to their symbiosis, and then sent to the smelter to recover the gold and silver.

4. Flotation-cyanation-roasting-cyanation
This scheme is used to treat quartz sulfide ores containing gold antimonide, pyrrhotite, chalcopyrite and other sulfide ores. Sulfide ore can be floated from the ore as concentrate, and then the gold and silver in the exposed sulfide can be roasted and then cyanidated. Because the gold and silver in the middle and tailings after flotation are still high, they need to be cyanidated for recovery.

5. Cyanide-flotation
When the gold and silver coexisting with the sulfide in the ore cannot be completely recovered by cyanidation method, the slag after cyanidation can be floated again to improve the gold and silver recovery rate.

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