The main lithium- containing minerals are spodumene, lithium mica , and lithium feldspar . Their floatability is as follows:
1 spodumene A12O3·Li2O·4Si02, containing Li2O 4.5% to 8%. The surface-purified spodumene is easily floated with oleic acid and its soaps, but its surface is polluted or polluted by the slime in the pulp, and its floatability deteriorates. In addition, some dissolved salt ions ( copper , iron and aluminum ions, etc.) in the pulp not only activate the spodumene, but also activate the gangue minerals, so the mud is removed before the flotation and treated with alkali. When treated with sodium hydroxide, the recovery rate of spodumene increases with the amount of the spodumene, and the stirring time is also shortened accordingly. As the stirring strength increases, the recovery rate also increases. If the speed is increased by 7 times, the recovery rate can be increased by 40%.
When using oleic acid or naphthenic acid soap as a collector , spodumene can float well in both neutral and alkaline media. When octadecylamine and sodium phosphonate are used as collectors, spodumene can only float in weakly alkaline or neutral media. When oleic acid is used as a collector, sodium fluoride and lignosulfonate are used as regulators, and the pH of the spodumene is best when the pH is adjusted to 7 to 7.5 with sodium hydroxide and sodium carbonate.
The activated spodumene can be floated with an anionic or cationic collector. Unactivated spodumene is difficult to float when the amount of oleic acid is high.
Regardless of the type of collector used, water glass, dextrin and starch are strong inhibitors of spodumene. Among them, the selectivity of starch is better, followed by dextrin. They first suppress spodumene and then suppress gangue. However, the selectivity of water glass is poor, and the spodumene and gangue are simultaneously inhibited.
The flotation particle size of spodumene is generally below 0.15 mm. When the particle size was 0.2 mm, the recovery rate of flotation was 61%, and when the particle size was 0.3 mm, the flotation recovery was 22%. It is one of the characteristics of spodumene flotation.
2 lithium mica Al203·3Si02.2 (KLi)F, containing Li20 1.2% to 5.9%. The coarse-grained lithium mica is enriched by hand selection, air separation or friction, and the fine-grained lithium mica is recovered by flotation. The lithium mica collector is preferably a cationic collector, and when octadecylamine is used, the lithium mica is well floated in both acidic and neutral media. Unactivated lithium mica cannot be recovered by oleic acid, and after activation with hydrofluoric acid, better indicators can be obtained.
Some iron salts, lead salts, sodium sulfide, sodium hydrogen phosphate starch and pulp, and the like can be suppressed lepidolite. Lithium carbonates and sulfates activate lithium mica. When octadecylamine is used to select lithium mica, the best activators are water glass and lithium sulphate, while strong inhibitors are mixtures of bleaching powder, sodium sulphide and starch. The nitrates of copper, aluminum and lead are inhibitors of lithium mica, while the sulfates of copper and aluminum are activators of lithium mica.
3 lithium feldspar Al203·Li20·8SiO2, containing Li20 2%～4%, using anionic collector such as oleic acid, sodium oleate, sodium isooctyl citrate to float lithium feldspar at any pH None of them float. With a cationic collector, such as octadecylamine for flotation of lithium feldspar, its floatation is good. When octadecylamine is used as a collector, the recovery rate is 78% when the pH of the slurry is 5.5-6.0, and the alkylamine salt is used in an alkaline medium (pH 7.5-9.5). When flotation, the recovery rate can be increased to 90% to 92%.
When an alkylamine salt is used as a collector, ferric chloride (300-500 g/t) can strongly inhibit lithium feldspar. When the pH of the medium is 5.8, the recovery rate is reduced to 10% to 15%. In acidic and alkaline media, its inhibition is enhanced. Calcium chloride activates lithium feldspar and improves its recovery in neutral and alkaline media (pH = 9.2). In the case of using an alkylamine salt, the inhibitor of lithium feldspar is sodium sulfide, sodium silicate, starch, tannin, sodium carbonate, sodium fluorosilicate, and sodium hydrogen phosphate.
In the 1950s and 1960s, there were many studies on the principle and selection process of spodumene flotation at home and abroad. At the same time, the basic principles of beneficiation and the research on the specific nature of ore selection have been advancing leaps and bounds for more than a decade. Great achievements have been made, but there are few studies on spodumene, far behind the research on the sorting nature of other ores. In summary,
At present, there are three main difficulties in the practice of spodumene recycling:
1) The collector is still using a traditional potency agent with low potency. Collectors commonly used in the practice of spodumene flotation industry are: fatty acids and their soaps (731, naphthenic acid soap, oleic acid, tal oil, etc.), amine cation collectors, and alkyl sulfates. And sulfonates and the like. There are obvious defects in the above collectors. For example, fatty acid collectors are not only required to be used in large amounts, but also have a poor collection effect when used alone. They need to be used in combination with various collectors, and are sensitive to temperature and are not easily dissolved. Dispersion; the use conditions of alkyl sulfates and alkyl sulfonates are harsh, such collectors need to be effective in the selection of spodumene in an acidic environment; and the amine collectors are spodumene. It has a strong ability to capture, but at the same time it has a strong ability to capture other silicate-like gangue minerals with poor selectivity.
2) The modifier has poor selectivity and is mostly toxic. The sprigidity of spodumene minerals and silicate-like gangue minerals is similar. The key to the success of flotation process is the effective selective inhibition and activation of spodumene in flotation practice. Mainly include: water glass, 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 "inevitable ions" has an important influence on the spodumene flotation. Due to the surface characteristics of different silicate minerals after fracture and the natural differences in the chemical characteristics of their mineral crystals, there are certain flotation differences in different flotation environments. As long as the separation conditions are controlled, spodumene and others can be realized. Effective separation of silicate-like gangue minerals. During the grinding process, due to the role of steel balls and linings in the operation, the mineral surface is contaminated with a certain degree of iron, so that iron and its compounds are fixed on the mineral surface, and these "inevitable ions" are difficult to completely remove. Effects of mineral sorting a large extent; Further, the flotation water (particularly backwater) multivalent metal cations present in itself will produce different effects on the flotation of silicate minerals (e.g., Ca2 +, Mg2 + , Fe3+, etc.). Therefore, in the practice of industrial flotation, the above "inevitable ions" have an important influence on spodumene flotation.
It can be seen that the high-precision sorting of spodumene must be achieved by solving the basic problems of the selection of high-efficiency collectors and inhibitors, and the elimination of the influence of “inevitable ionsâ€.
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