Spodumene and beryl are the main rare metal resources for lithium and beryllium extraction. Both are aluminosilicate minerals, often co-existing in the same pegmatite deposits. And both belong to non-magnetic minerals, the relative density is also very close. In beneficiation method, it is difficult to effectively separate beryl and spodumene when magnetic separation or gravity separation method is used. Therefore, flotation separation process can effectively separate beryl and spodumene.
At present, there are three common flotation separation process for spodumene and beryl, namely: preferential flotation method, mixed flotation method and combined flotation method.
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There are three methods for the separation of spodumene and beryl by preferential flotation: First, the method of preferential flotation of beryl and then of spodumene. Second, give priority to flotation of spodumene, and then select beryl. Third, part of the spodumene is preferentially flotated, and then lithium and beryllium are mixed and separated.
The method is to suppress beryl first, and preferentially float spodumene. Then after the spodumene is flotated, the beryl is activated again and the process method of flotation. First put Na2CO3 and alkali lignin (or sodium oxide and lignosulfonate) in a low alkaline medium for a long time. Alkali lignin forms a hydrophilic film on the surface of beryl and gangue minerals. At this time, beryl and gangue are suppressed. Collectors such as oxidized paraffin soaps, naphthenic acid soaps, and firewood then capture spodumene. The obtained tailings can activate beryl and inhibit gangue after adding NaOH, Na2S and FeCl3. Finally, oxidized paraffin soap and diesel oil are used for flotation of beryl.
The working sequence of the flotation method is to suppress spodumene first, to preferentially float beryl, and then activate spodumene and perform flotation. During flotation, the easy-to-float minerals need to be removed first. Spodumene was then inhibited in a highly alkaline medium with Na2CO3, Na2S and NaOH. Fatty acid soap (oxidized paraffin soap or diesel) is used to preferentially float out beryl. The obtained tailings were activated with NaOH, and fatty acid soap was added for flotation of spodumene.
In this method, NaF and Na2CO3 are used as adjusting agents, and part of spodumene is preferably floated with fatty acid soap. Then NaOH and Ca2+ are added, and the spodumene and beryl are flotated by mixing with fatty acid soap. The obtained mixed concentrate is heated with Na2CO3, NaOH and acid and alkaline water glass. Beryl can be surfaced to achieve the separation of lithium and beryllium.
When the mixed flotation separation method is used, spodumene and beryl will float together first. The spodumene and beryl are then selected separately from the concentrate. The process is divided into three steps: easy flotation, lithium-beryllium mixed flotation and selection-separation flotation.
Easy flotation: in neutral or weak alkaline (sodium carbonate) medium, use naphthenic acid soap (with oxide paraffin soap) to float free apatite, garnet and polluted fine-grained feldspar, quartz, de-mother, etc.
Lithium-beryllium mixed flotation: After removing the easily-floating matter, sodium carbonate, sodium hydroxide and sodium sulfide are used as regulators. In the strong alkaline pulp, collectors such as naphthenic acid soap, paraffin oxide soap and diesel oil are added. Spodumene and beryl can be simultaneously surfaced.
Selection-separation and flotation: After obtaining the mixed coarse concentrate, use sodium carbonate, sodium sulfide (add a small amount of calcium chloride if necessary), diesel oil and oxidized paraffin soap for selection. Its purpose is to remove as much as possible the gangue ore contained in the foam. Then, under the combined action of a mixture of ferric chloride and water glass (1:1 ratio), sodium sulfide and sodium carbonate, beryl is flotated with paraffin oxide soap to make spodumene a product in the tank.
The method of separating spodumene and beryl by combined flotation is generally a method used when the spodumene and beryl concentrates are obtained by mixed flotation, and the two cannot be effectively separated by single flotation. There are two main processes: roasting-flotation method and hot boiling-flotation method.
Roasting-flotation method is to roast the mixed concentrate of spodumene and beryl at different temperatures for one hour. After cooling, use sodium carbonate, sodium hydroxide or sodium sulfide as regulator and naphthenic acid soap as collector for flotation separation.
In order to effectively float beryl, the temperature needs to be controlled at 500~700°C during roasting. The dosage of sodium sulfide added is 1000-2000 g/ton, while the dosage of naphthenic acid soap is 150-200 g/ton.
It should be noted that, before roasting, the foam should be filtered and dried, and iron should be removed by a magnetic separation process.
The hot cooking-flotation method is to add sodium hydroxide, sodium sulfide, oxidized paraffin soap and diesel oil to the foam after mixing and flotation. Then boil (80~85°C) for 15 minutes, so that the coarse-grained spodumene, feldspar, quartz, etc. are suppressed. After cooling (25°C), fine-grained spodumene and beryl were floated out. Then add sodium carbonate, sodium chloride and alum and cook hot (85°C) for 30 minutes. After cooling, the spodumene is floated with naphthenic acid soap, leaving the fine-grained beryl in the tank.
The above are the commonly used flotation methods for separating spodumene and beryl. In actual beneficiation, the choice of flotation method should be determined according to the beneficiation test analysis. Only scientific and rational design of suitable mineral processing process and related mineral processing equipment can improve the return on investment. Otherwise, it is likely to cause a low recovery rate and reduce the return on investment.