Conventional flotation of polymetallic sulfide ores

Multi metal sulfide ores Ore primarily copper, lead, zinc and sulfur. Lead ore or zinc ore of a single metal in nature is rare, and the common ones are lead-zinc, copper-zinc, copper-lead-zinc, lead-zinc-sulfur, copper-lead-zinc-sulfur symbiotic ore. These ores contain more or less pyrite or pyrrhotite. The task of sorting polymetallic sulphide ore is to obtain copper, lead and zinc concentrates respectively, and when the content of iron sulphide is high, it is necessary to obtain sulphur concentrate. When gold or silver and other associated elements are contained in the ore, recycling must be considered.

1. The floatability of lead-zinc sulfide minerals

The sulfide minerals of lead are mainly galena, and the sulfide minerals of zinc are mainly sphalerite.

Galena ( PbS , lead 86.6% ) - brittle, fresh surface is hydrophobic, easy to float when not oxidized, floatable after oxidation. Typical collector is a xanthate or black powder, is typically heavy chromate inhibitor, it can not be suppressed cyanide. Sodium sulfide is sensitive to the floatability of the lead ore, and the presence of excess sulfur ions can inhibit the flotation of galena.

Sphalerite ( ZnS , pure zinc blende containing 67.1% ) - very few pure zinc blends in nature, common yellow or black sphalerite variants - iron sphalerite, iron content of 0~20% The higher the iron content, the darker the color. Sphalerite also often contains elements such as copper and cadmium , containing up to 2% copper and cadmium up to 1.0% to 1.5% . These elements exist in the lattice in the form of isomorphic exchanges, and some exist in very fine inclusions. Sphalerite is the most difficult to float sulfide mineral. Natural sphalerite is more or less activated by copper or other ions in the deposit. Some heavy metal salts such as mercury , copper, silver, lead, cadmium, etc., can activate the flotation of sphalerite. Due to the different impurity content, the sphalerite floatability varies greatly. A commonly used activator is copper sulfate. Cyanide can strongly inhibit sphalerite. Zinc sulfate, sulfite, thiosulfate, sodium sulfide, etc. can all inhibit the flotation of sphalerite.

2. Separation method and pharmaceutical system

The main problems to be solved in the flotation of polymetallic sulphide ore are: lead-zinc separation, copper-zinc separation, copper-lead separation, and separation of iron sulphide from iron sulfide. Separation of sulfide minerals from gangue minerals is usually not very difficult.

( 1 ) Lead-zinc separation

When using the bismuth-based collector to float lead-zinc ore, almost all of them adopt the scheme of suppressing zinc and floating lead. The scheme of suppressing lead and floating zinc is rarely used, and it is only used as lead removal of zinc concentrate or dezincification of lead concentrate. There are two types of methods for inhibiting sphalerite: cyanide and non-cyanide.

1 Cyanide method - cyanide often combined with other agents, such as zinc sulfate, can reduce the amount of cyanide, but also strengthen the inhibition.

Cyanide inhibition of sphalerite can lead to better separation of lead-zinc separation, and the process is easier to control. However, because cyanide is toxic and dissolves gold and silver, it has gradually been replaced by a cyanide-free process.

2 non-cyanide (cyanide-free process) method - the main inhibitors of this type of method are sulfurous acid, sodium sulfite, sulfur dioxide gas and sodium thiosulfate. It can also be used in combination with zinc sulfate. Such agents are non-toxic and the suppressed sphalerite is easily reactivated.

When the lead-zinc ore is sorted, the grinding grain size may be slightly coarser, the pulp pH value is low, and the separation system is simple. For ore with higher sulfur content, the grinding grain size is generally finer, and the pulp pH is higher.

( 2 ) Zinc-sulfur separation

Zinc-sulfur separation is generally carried out by using lime to inhibit iron sulfide. When pH=10~12 or higher, the zinc oxide is activated by copper sulfate and collected by xanthate. It is also possible to raise the temperature to make the surface of the zinc blende and the iron sulfide different in oxidation, and to suppress the iron sulfide by heating. After the mixed concentrate is heated and aerated, the surface of the iron sulfide is oxidized, the floatability is lowered, and the sphalerite is lower than the temperature. 6 5 °C When the temperature is exceeded, the recovery rate of sphalerite will also decrease.

( 3 ) Copper-zinc separation

Copper-zinc separation is currently a problem. The reasons are many and complex, and the pharmaceutical system is difficult to control. At present, copper-zinc separation mainly uses zinc-suppressed copper or zinc-suppressed copper or sulfur such as zinc sulfate, sodium sulfite and sodium sulfide, and then copper-sulfur separation.

( 4 ) Copper-lead separation

Copper and lead in copper and lead sulfide ore are often in the form of galena and chalcopyrite. They are similar in floatability. Usually, copper-lead mixed concentrate is obtained first and then further separated. The separation scheme should pay attention to the following aspects:

A pair of unactivated or surface oxidized galena may be inhibited by dichromate and sulfite, but has a less inhibitory effect on galena which has been activated by copper ions. The chalcopyrite can be inhibited by sodium sulfide, and the chalcopyrite and the porphyrite can be inhibited by cyanide;

2 When the copper content is large, the lead-free copper should be mainly used;

3 Try to choose a cyanide-free and chromium-free process to reduce environmental pollution.

( 5 ) De-peeling of mixed concentrate

Separation of mixed concentrates is often difficult because the mixed concentrate contains excess chemicals. Removal of these agents prior to separation can significantly improve the separation. The commonly used methods for drug removal in China are as follows: 1 Concentrate the mixed concentrate, concentrate the overflow, discard it, add the supernatant to the bottom stream and then float it; or concentrate, filter and add the water and then float ; 2 Concentrate the concentrate, concentrate the product and grind it to Scrubbing the surface of the mineral and then separating the flotation ; 3 desorbing the surface of the mineral surface collector film with sodium sulfide, then removing and filtering the agent after flotation ; 4 using activated carbon to adsorb excess agent in the slurry, which is a simple And effective methods are widely used.

3. Development trend of domestic polymetallic sulfide ore flotation

( 1 ) Lead-zinc ore generally adopts a preferential flotation process.

(2) lead - zinc - Flotation sulfur types: â‘  lead - zinc - sulfur flotation; â‘¡ lead - zinc - after flotation of sulfur, mixed concentrate regrinding lead - zinc - flotation separation of sulfur sequentially; â‘¢ Lead-sulfur mixed sorting, zinc preferential flotation, mixed concentrate and lead-sulfur separation flotation ; 4 lead preferential flotation, zinc-sulfur mixed sorting, re-zinc-sulfur separation flotation ; 5 lead and easy floating zinc mixed selection It is difficult to float zinc and sulfur mixed, and then separate flotation.

The flotation process and types of lead-zinc-sulfur ore are mainly due to the large difference in floatability between sphalerite and iron sulfide minerals in the ore. When there is a sphalerite which is easy to float and difficult to float in the ore. When the iron sulfide in the ore is good in floatability, the preferential flotation process should generally be adopted along the activation.

( 3 ) Copper-lead-zinc ore or copper-lead-zinc-sulfur ore flotation process; copper-lead mixed selection is more common now, zinc and sulfur are preferred in the future; copper-lead-zinc mixed selection in individual plants, Later, copper is separated from lead and zinc, and lead and zinc are separated. In some plants, lead-copper-zinc-sulfur mixed mixing is used. After mixing and grinding, copper-lead-zinc is separated from sulfur, copper is separated from lead and zinc, and finally lead and zinc are separated. The concentrate is sent to the smelting plant for processing.

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