Beneficiability of lithium minerals and factors affecting recovery

① Spodumene A12O3·Li2O·4Si02, containing Li2O4.5% ~ 8%. Spodumene with a pure surface is easy to float with oleic acid and its soaps, but its surface is polluted by weathering or contaminated by slime in the slurry, and its floatability becomes bad. In addition, the ions of some dissolved salts in the pulp (ions of copper, iron and aluminum, etc.) not only activate spodumene, but also activate gangue minerals, so it is necessary to demud and treat with alkali before flotation. When treated with sodium hydroxide, the recovery rate of spodumene increases with the increase of its dosage, and the stirring time is shortened accordingly. With the increase of stirring intensity, the recovery rate also increased. If the speed is increased by 7 times, the recovery rate can be increased by 40%. When oleic acid or naphthenic acid soap is used as collector, spodumene can float well in both neutral and alkaline media. When stearamine and sodium phosphonate are used as collectors, spodumene can float only in weakly alkaline or neutral media. When oleic acid is used as collector, sodium fluoride and lignosulfonate are used as regulator, and sodium hydroxide and sodium carbonate are used to adjust pH to 7 ~ 7.5, the flotation effect of spodumene is the best. Activated spodumene can float with anionic or cationic collectors. Without activating spodumene, it is difficult to float when the amount of oleic acid is high. No matter which collector is used, water glass, dextrin and starch are strong inhibitors of spodumene. Starch was the most selective, dextrin was the second. They inhibit spodumene first, then gangue. However, the selectivity of water glass is poor, which can inhibit spodumene and gangue at the same time. The flotation particle size of spodumene is generally below 0.15mm. When the particle size is 0.2 mm, the flotation recovery rate is 61%, and when the particle size is 0.3 mm, the flotation recovery rate is 22%. The difficulty of coarse particles floating is one of the characteristics of spodumene flotation.

② Lipolite Al203.3Si02.2 (KLi)F, containing Li20 1.2% ~ 5.9%. Coarse lepidolite is enriched by hand, wind or friction, and fine lepidolite is recovered by flotation. The cationic collector is the best collector for leucite, and the flotation of leucite in acidic and neutral media can be performed well when octadecylamine is used. The unactivated lipolite can not be collected by oleic acid, and a better index can be obtained by activating it with hydrofluoric acid. Some iron salts, aluminum salts, lead salts, sodium sulfide, starch and sodium hydrogen phosphate in the pulp can inhibit lemica. Lithium carbonate and sulfate can activate lipolite. In the separation of lepidolite by octadecylamine, the best activators are water glass and lithium sulfate, and the strong inhibitors are the mixture of bleaching powder, sodium sulfide and starch. Nitrates of copper, aluminum and lead are inhibitors of lepidolite, while sulfates of copper and aluminum are activators of lepidolite.

(3) Al203·Li20·8SiO2, containing Li20 2% ~ 4%, with anionic collectors such as oleic acid, sodium oleate, sodium isoctylarsonate to flotation, at any pH are not floating. When cationic collectors, such as octadecylamine, are used to float lipolite, its floating property is very good. When the pH of pulp is 5.5 ~ 6.0, the recovery rate is 78%, but when alkylamine salts are used in alkaline medium (pH is 7.5 ~ 9.5), the recovery rate can be increased to 90% ~ 92%. When the alkylamine salt is used as the collector, ferric chloride (300 ~ 500g/t) can strongly inhibit dipolitrite. When the pH of the medium is 5.8, its recovery rate drops to 10% ~ 15%. In acidic and alkaline media, its inhibition effect is strengthened. Calcium chloride can activate transliborite and improve its recovery in neutral and alkaline media (pH= 9.2). In the use of alkylamine salts, the inhibitors of lipolite include sodium sulfide, sodium silicate, starch, tannin, sodium carbonate, sodium fluosilicate and sodium hydrogen phosphate. In the 1950s and 1960s, there were more and more researches on the floatation principle and separation process of spodumene at home and abroad. In the past ten years, the research on the basic principle of mineral processing and the separation properties of specific ores at home and abroad has made rapid progress and achieved great results, but the research on spodumene is less, far behind the research on the separation properties of other ores. To sum up, there are three main difficulties that may exist in the current spodumene recycling practice:

1) Traditional agents with low efficiency are still used as collectors. In the practice of spodumene flotation industry, the commonly used collectors are: fatty acids and their soaps (731, naphthenic acid soap, oleic acid, tar oil, etc.), amine cationic collectors, and alkyl sulfates and sulfonates. The above collectors all have obvious defects. For example, fatty acid collectors not only require a large amount, but also have poor collection effect when used alone, and need to be combined with a variety of collectors. Moreover, they are sensitive to temperature and difficult to dissolve and disperse. Alkyl sulfates and alkyl sulfonates are used under harsh conditions, and such collectors need to be in acidic environment to achieve effective separation of spodumene. Although the amine collector has a strong ability to collect spodumene, it also has a strong ability to collect other silicate gangue minerals, and the selectivity is poor.

2) The selectivity of the regulator is poor, and most of them are toxic. The floating property of spodumene minerals is similar to that of silicate gangue minerals. The key to the success or failure of flotation process lies in whether the effective selective inhibition and activation of spodumene can be achieved in flotation practice. At present, the common inhibitors mainly include: Sodium silicate, dextrin, starch, sodium fluoride, sodium sulfide, etc., these inhibitors not only have an inhibitory effect on gangue minerals, but also have an obvious inhibitory effect on spodumene.

3) The existence of "unavoidable ions" has an important impact on the flotation of spodumene. Due to the surface characteristics of different silicate minerals after crushing and the natural differences in their mineral crystal chemical characteristics, there are certain flotation differences in different flotation environments. As long as the separation conditions are well controlled, the effective separation of spodumene and other silicate gangue minerals can be realized. In the grinding process, due to the role of steel balls and lining plates in the operation, the mineral surface is polluted by iron to a certain extent, so that iron and its compounds are fixed on the mineral surface, and these "unavoidable ions" are difficult to completely remove, which greatly affects the mineral selection; In addition, the polyvalent metal cation itself in the flotation water (especially the backwater) will also have different degrees of influence on the flotation of silicate minerals (such as Ca2+, Mg2+, Fe3+, etc.). Therefore, in industrial flotation practice, the above "unavoidable ions" have an important impact on spodumene flotation.

It can be seen that the selection of efficient collectors and inhibitors and the overcoming of the influence of "unavoidable ions" must be solved in order to achieve high-precision separation of spodumene.