Lithium is the lightest metal found in nature element, with a strong electrochemically active. Lithium products have important applications in high-energy batteries, aerospace, nuclear fusion power generation, etc. Therefore, lithium is known as "a new energy metal in the 21st century", and lithium is also known as "an important element in driving the world forward."

Lithium resources are mainly distributed in the granite pegmatite deposit and the salt lake brine deposit. China's lithium resources are relatively abundant, and the proven lithium resource reserves are about 540,000 tons (converted to pure metal lithium), ranking the world's forefront. Among them, China's brine lithium accounted for a large proportion, up to 79%, is also an important source of lithium resources in China. Although the cost of lithium extraction from brine is relatively low, domestic brine resources are mostly distributed in the Qinghai-Tibet Plateau, and the development conditions are poor. At the same time, lithium extraction from salt lake brines in China has not yet achieved large-scale industrialization. Therefore, the current situation of lithium extraction from lithium minerals in China is still difficult to change in the short term. Lithium ore mainly comprising lithium minerals spodumene (with Li2O 5.80% ~ 8.10%), lepidolite (containing Li2O 3.20% ~ 6. 45%) , lithium aluminum phosphate rock (including Li2O 7.10% ~ 10.10%), through Lithium feldspar (containing Li2O 2.90% to 4.80%) and iron lithium mica (containing Li2O 1.10% to 5. 00%), of which spodumene is the most important lithium mineral resource. To this end, we must focus on the processing of spodumene.

At present, the selection methods of spodumene mainly include: hand selection method, pyrolysis solution, magnetic separation method, resuspension method, flotation method and joint beneficiation method. Among them, the spodumene flotation method is the most widely used in the laboratory, and the most widely used mineral processing method in the industry. Based on the current status of pegmatite-type spodumene ore resources, the physicochemical properties and floatability of the main constituent minerals in the spodumene ore, the analysis and summary of the basic research and process status of the spodumene ore flotation, pointed out the Weijing The main influencing factors and major problems in the flotation process of rock-type spodumene ore.

1 pegmatite-type spodumene ore

1.1 Status of pegmatite-type spodumene ore resources

The distribution of lithium ore resources in China is relatively concentrated. The granitic pegmatite-type lithium deposits are mainly distributed in 7 provinces and regions, and their reserves are shown in Table 1. Among them, Sichuan, Xinjiang, Jiangxi, and Hunan are the main lithium ore resources, while the spodumene resources are mainly concentrated in Sichuan and Xinjiang. At present, the main domestic lithium deposits are: Sichuan Kangding methyl card lithium antimony ore, Sichuan Jinchuan-Malcon Kelin lithium antimony ore, Xinjiang Fuyun Coco Tokai lithium antimony ore, Xinjiang Fuyun Kelumut lithium niobium Ta-Nb ore, lithium ore Jiangxi Yichun Ta-Nb, Hunan Linwu fragrant flower shop mountain peak lithium niobium mine, Xiangtan County of Hunan Road is the source of lithium, rubidium red polymetallic ore.

1.2 Physicochemical properties and floatability of major minerals

1.2.1 Spodumene

Lithofene (LiAl[Si2O6]) is a chain-like silicate mineral, and the [SiO4] tetrahedron is joined in the c-axis direction by a co-angled oxygen to form an infinitely extending siloxane tetrahedral chain; Al and O form [ AlO6] octahedron, and infinitely extended octahedral chain connected in a zigzag shape along the c-axis direction in a co-edge manner. The two [SiO4] tetrahedral chains form a 2:1 sandwiched "I" shaped chain with an [AlO6] octahedral chain, which is then joined by Li. Li is in the M2 position, Al is in the M1 position, and its crystal structure is shown in Fig. 1.

When spodumene dissociates, the bond between the large radius cation filled or compensated for the oxygen and the oxygen in the mineral lattice is prone to break. In aqueous solution, these cations exchange with H+ in the water, so that H+ is adsorbed on the surface oxygen region of the mineral. In addition, the Si exposed after the Si-O bond is broken has the ability to bond OH- in water, and the high-valent small-radius cations of the linked chain are rarely exposed. As a result of these two effects, the surface of the spodumene is bound in the water. The hydroxyl group is negatively charged over a wide range of pH values, and the zero point is very low. When the surface-purified spodumene is floated with an anionic collector , the floatability is poor. When the cation-carrying dodecylamine is used for flotation, the mineral has good floatability.

1.2.2 Quartz

Quartz is a silicate mineral with a frame structure. In the crystal structure, each [SiO4] tetrahedron is shared with the adjacent four [SiO4] tetrahedrons by the top O at the four corners, and is connected into a three-dimensional space. The extended frame structure has a crystal structure as shown in Fig. 2.

When the mineral dissociates, there is a large amount of Si-O bond cleavage, which exposes a large amount of Si and O on the mineral surface. Si adsorbs OH- in the aqueous solution to form SiOH, and O also adsorbs H+ in water to form -OH. The surface is negatively charged, so the zero point of quartz is very low. The surface-purified quartz is difficult to float with the anionic collector sodium oleate, and it has good floatability when floated with the cationic collector dodecylamine.

1.2.3 Feldspar

The silicate mineral micro-plagioclase and apatite feldspar are all aluminosilicates. In their mineral crystal structure, the siloxane tetrahedrons are connected to each other to form a chain parallel to the a-axis. The chain is surrounded by four tetrahedrons. The tetragonal ring is formed, and the chain and the chain are connected to each other to form a frame structure in a three-dimensional space, and there is a large gap in each of the square ring structures, wherein the insufficient charge is supplemented by a large radius metal cation K+, Na+, Ca2+, etc. . Taking micro-plagioclase as an example, its crystal structure is shown in Figure 3.

In the mineral structure, 1/4 of Si is replaced by Al. When the mineral dissociates, the Si-O and Al-O bonds break. When the cations such as K + , Na+ and Ca2+ are compensated on the surface, they are dissolved and exchanged with H+ in the water. H+ is adsorbed on the oxygen zone of the mineral surface, and both Si and Al exposed to the mineral surface can bond OH- in the water. The above factors cause the two minerals to be negatively charged, and the zero point is very low. The surface pure feldspar is difficult to float with the anionic collector sodium oleate, and is easily floated with the cationic collector dodecylamine.

1.2.4 Mica

The layered structure silicate mineral mica is a TOT type three-layer structure. In its crystal structure, the active oxygen and OH- of the two silicon tetrahedrons are relatively up and down, but have relative displacement in the plane direction, thereby making the upper and lower layers active. Oxygen and OH- are the most closely packed, and the cations such as Al3+ are filled with octahedral voids to form an Al-O4(OH)2 octahedron. Two layers of tetrahedral sheets sandwich an octahedral sheet to form the basic structure. One quarter of the Si in the tetrahedral sheet is replaced by Al. The resulting negative charge is compensated by the large radius cations such as K+. Such as lithium mica (or muscovite), the crystal structure shown in Figure 4.

Since the mineral dissociates along the interlayer, large-area alkali metal cations are exposed, and after dissolving in water, these cations exchange with H+ in the water to adsorb H+ to the surface oxygen region. Since mica is in a sheet-like structure, H+ can be adsorbed on the mineral surface over a large area. In addition, since Si is replaced by Al, it is inevitably caused to have more negative charges on the surface of the mineral, so the zero point of the mineral is extremely low. The pure mica on the surface is completely non-floating when it is floated with the anion collector sodium oleate. When it is floated with the cationic collector dodecylamine, it can be completely recovered in a wide pH range.

It is not difficult to compare the crystal structure and physicochemical properties of the main minerals in the spodumene ore. The spodumene, quartz, feldspar and mica are all silicate minerals with low zero point, and their pure minerals are not easy to use. The anion collector floats, and both are easy to float with the cationic collector, which brings great difficulties to the flotation separation of these minerals. At the same time, because the surface of the spodumene ore is often weathered or contaminated The slurry is contaminated by the slime, causing its floatability to deteriorate, and some ions (Ca2+, Fe3+, Mg2+, etc.) in the pulp not only activate the spodumene, but also activate the gangue minerals, so that spodumene and veins The separation efficiency of stone mineral flotation is greatly reduced, which increases the difficulty of flotation separation of spodumene ore.

2 Research status of flotation separation of spodumene ore

So far, some achievements have been made in the basic theory and sorting process of the spodumene flotation, and the focus is on the flotation agent of the spodumene ore.

2.1 spodumene ore flotation collector

2.1.1 Cationic collector

The cation collector used in the flotation of spodumene ore is mainly an amine collector, which floats gangue minerals such as quartz, feldspar and mica under acidic conditions, leaving the spodumene at the bottom of the tank. This method is often used for the rough selection of spodumene, and it is not possible to directly obtain a spodumene concentrate with a higher purity, which needs to be used in combination with other sorting methods. In production practice, Yan Gengsheng is aiming at a pegmatite spodumene ore, using a process of flotation of spodumene with mixed soap and diesel under alkaline conditions after flotation of mica with folic acid amine under acidic conditions. Mica concentrate and spodumene concentrate have been obtained, and good economic benefits have been achieved. In terms of single minerals, Yin Wanzhong and Sun Chuanqi studied the flotation of spodumene with a cationic collector dodecylamine without adding any activators and inhibitors, and obtained lithium fusilli in the dodecylamine system. Stone has a good floatability conclusion.

3.1. 2 anion collector

The traditional spodumene anion collectors are mainly fatty acids and soaps thereof, namely oleic acid, oxidized paraffin soap, naphthenic acid soap, tal oil and sodium oleate, alkyl sulfates and sulfonates. However, due to the difference in ore properties, the increasing complexity of ore components and the comprehensive utilization of low-grade spodumene ore, the use of collectors has evolved from a single drug to a mixed drug.

Ren Wenbin used the tannic acid instead of the original oxidized paraffin soap as a collector for the recyclable recycling of the cocoaco spodumene tailings. The grade of spodumene concentrate was increased from 2.3% to 5.8%.

In terms of mixed drugs, Zhao Yun used a combination of oxidized paraffin soap and tall oil to obtain a good index and solved the problem of low recovery rate of a high-grade psogorite in a granitic pegmatite in Jiangxi. The problem of low recovery rate. Sun Wei and Ye Qiang used oxidized paraffin soap and naphthenic acid soap as collectors to conduct a flotation test on a pegmatite-type spodumene (Li2O grade 1.42%) in Sichuan, and finally obtained a concentrate of Li2O grade 6.04. %, a good indicator of a recovery rate of 85.88%. Liu Ningjiang conducted a flotation test on the sprigite of V26 and V38 ore in the rare coke mine in Xinjiang, using a strong agitation scrub to clean the mud, and using a cationic collector with a foaming agent flotation mica under neutral weak base conditions. Then, using sodium carbonate, sodium hydroxide combination adjusting agent to adjust the slurry to a pH of 10.5 to 11. 5, using oxidized paraffin soap and naphthenic acid soap as a flotation process of the collector, obtained 5.65% ~ 6.37 % of spodumene concentrate with a good recovery of 80.77%.

2.1.3 New collector

In the research of the selectivity of spodumene collector, Wang Yuhua replaced the traditional oxidized paraffin soap with a new chelating collector, which achieved the flotation separation of spodumene with quartz and feldspar, which not only significantly reduced the cost of the agent. Moreover, the sorting property between spodumene and quartz and feldspar can be greatly improved, thereby improving the nichromite beneficiation index. At the same time, He Jianyu used the chelation collector YZB-17 to improve the grade and recovery rate of spodumene and beryl mixed concentrate for the spodumene (Li2O grade 0.46%) and beryl in a granite pegmatite mineral. And the separation of spodumene and beryl can be achieved.

In the study of the collection performance of spodumene collectors, Wang Yuhua studied sodium oleate, C7-9 hydroxamic acid, sodium dodecyl sulfate and the new amphoteric collector YOA- through a single mineral flotation test. 15 The capture performance of spodumene, the results show that: the new amphoteric collector YOA-15 ​​has a higher ability to capture spodumene than sodium oleate, C7-9 carboxylic acid and sodium dodecyl sulfate. Strong ability to capture. For the No.3 vein spodumene mine and tailings tailings, the Cocoto Sea Concentrator used the new amphoteric collector YOA-15 ​​to conduct flotation tests under different water quality, showing strong harvesting capacity. With the foaming ability, a rough selection can achieve a better sorting index of crude concentrate Li2O grade 5.26% and a recovery rate of 83.3%.

According to the research of domestic scholars, it is not difficult to find that there are few studies on the reverse flotation process of spodumene, which may be related to the content of spodumene in the ore and the low grade; in the positive flotation of anion collector, the traditional single The agent has been difficult to meet the flotation separation of spodumene, the combination of drugs is a new direction of development; in the new collector, mainly concentrated in the multi-group chelation collector and amphoteric collector, but to achieve industrial Production still has a long way to go.

2.2 spodumene ore flotation regulator

The spodumene ore flotation regulator is mainly “tri-alkali”, namely: Na2CO3, NaOH, Na2S and CaCl2. The amount, the location of the addition and the calcium ion content in the water have a great influence on the flotation. At the same time, since the main minerals in the spodumene ore are basically silicate minerals, which have similar floatability, they are all easily activated by metal cations. Based on these characteristics, the separation of spodumene from other gangue minerals is domestic. Many research scholars have done a lot of work.

In terms of the mechanism of action of the regulator, Li Yikang studied the mechanism of action of Na2CO3 and Na2S on the spodumene activated by Ca2+ and Fe3+ with a spodumene single mineral. The results show that: in the strong alkaline medium, the inhibitory component of Na2CO3 is CO2-3, and the inhibitory component of Na2S is HS-(S2-); CO2-3 is more inhibited by Ca2+-activated spodumene. Na2S has no inhibitory effect on Ca2+-activated spodumene, and Na2S has a stronger inhibitory effect on Fe3+-activated spodumene.

In the study of the influence mechanism of different addition order of adjusting agent and collector on the flotation of spodumene, Liu Fang and Sun Chuanqi studied the doping of metal cations Fe3+, Al3+, Pb2+, Cu2+ and collector in the dodecylamine flotation system. The effect of different addition sequences on the flotation of spodumene single minerals. The results show that: Fe3+ and Al3+ have a good inhibitory effect on spodumene flotation before dodecylamine, and the addition of dodecylamine enhances the inhibition of spodumene; Pb2+ and Cu2+ before dodecylamine Addition has a certain inhibitory effect on spodumene flotation, and the addition of dodecylamine enhances the inhibition of spodumene. At the same time, Liu Fang and Sun Chuanqi also studied the effect of different addition order of metal cations Fe3+, Al3+, Pb2+ and Cu2+ and collector on the single mineral flotation of spodumene in the sodium oleate flotation system. The results show that: (1) Adding Fe3+ and Al3+ before sodium oleate has different degrees of activation on the flotation of spodumene; adding Pb2+ and Cu2+ before sodium oleate, there is basically no flotation of spodumene. (2) Adding Fe3+ after sodium oleate has little effect on the flotation of spodumene; adding Al3+ and Cu2+ after sodium oleate has no significant effect on the flotation of spodumene; After adding Pb2 + , there is basically no effect on the flotation of spodumene.

In production practice, regarding the activation effect of metal cations, Lu Yongxin has researched and developed a new method for flotation separation of pegmatite spodumene and beryl: The ore does not require pretreatment and washing purification (to eliminate metal cations during grinding) Mainly Ca2 + , Fe3 + ) pollution of minerals, but to utilize and control this pollution and activation effect, so that common inorganic salt regulator anions (mainly F-, CO2-3) and metamorphic water glass to contaminated cations Selective desorption and inhibition are carried out to achieve the purpose of separating minerals by using a carboxylic acid collector. For a pegmatite spodumene mine in Xinjiang, Yuan Liying used Na2CO3-NaOH-CaCl2 combined regulator to use Lithium Oxide soap and hydroxamic acid as collectors. Li2O was obtained at pH 10.5～11.5. A spodumene concentrate with a grade of 6.22% and a recovery rate of 96.7%.

In terms of new selective inhibitors, Wang Yuhua et al. investigated inorganic inhibitors of sodium sulfide, sodium hexametaphosphate and various small molecule inhibitors of citric acid, oxalic acid, lactic acid, tartaric acid and disodium EDTA on spodumene and beryl. The inhibition behavior of two kinds of mineral flotation shows that sodium hexametaphosphate and disodium EDTA have better inhibition effect on spodumene and beryl than sodium sulfide and EDTA, and may be used as a substitute for sodium sulfide in lithium strontium. The conclusion in the practice of separation of mine flotation.

Regarding the research of modifiers, there are many researches on the activation of metal cations at home and abroad. There are many advances in both theory and practice, but there are few studies on new regulators, especially new organic modifiers. Facing the problem of difficult flotation separation of spodumene ore, it is very important to develop and develop new regulators, systematically study the mechanism of action of modifiers and spodumene, and create favorable conditions for the flotation separation of spodumene and gangue minerals. .

3 Main factors affecting the flotation of spodumene ore

There are many factors affecting the flotation index of the spodumene ore. The key factors are: grinding fineness, slime and easy-floating impurities, water quality, mixing intensity of mixing operation, temperature and rational use of drugs.

3.1 Grinding fineness

The coarse-grained floating is one of the characteristics of spodumene flotation. When the particle size is 0.2 mm, the flotation recovery rate is 61%; when 0.3 mm, the flotation recovery rate is 22%, so the flotation particle size of spodumene Generally less than 0.15 mm. With the change in the particle size of the spodumene inlay, the appropriate grinding fineness plays a crucial role in flotation.

3.2 slime and easy to float impurities

Because the surface of the ore is often polluted by weathering or contaminated by slime in the slurry and some easily floating impurities, its floatability deteriorates. Therefore, in the production practice, there is often a de-sliming operation or a priority to float the easy-floating impurities, which not only complicates the process, but also increases production input and reduces economic benefits.

3.3 Impact of water quality

The concentration ratio of CO2-3, OH- and Ca2+ ions in the flotation pulp is one of the key factors affecting the flotation index. The softness and hardness of the water used are different, and the amount of the adjusting agent and the place of addition are also different. Metal cations in water easily activate spodumene and other silicate minerals, thus affecting the selection criteria for flotation separation.

3.4 slurry mixing

The slurry agitation before flotation is the basic operation to ensure flotation separation, and the equipment conditions and mixing strength are the two core issues that must be paid attention to in the slurry operation. According to the data, under the same conditions, the recovery rate of the four-tank series stirring is still 5.41% higher than that of the two-tank stirring even if the stirring strength is about twice as high as that of the cocoa sea preparation plant. When the slurry agitation intensity of the Cocoto Sea Plant is nearly double that of the Kelumu Special Plant, the lithium concentrate grade and recovery rate are increased by 0.49% and 7.85%, respectively.

3.5 Influence of temperature

China's spodumene ore is mainly distributed in Ganzi Prefecture of Sichuan and the Cocoto Sea and Altai in Xinjiang. For example, the Sichuan Mika Lithium Mine in high altitude and cold regions has low temperature and thin air, fatty acids and amines. The charge performance is greatly affected by temperature, thus increasing the difficulty of spodumene flotation. For a spodumene mine with an altitude of more than 4000 m, Yixinhui used fatty acid collectors in the same process and pharmaceutical system and under different temperature conditions. The results showed that: water temperature after grinding was 10 °C, stirring float When the temperature is 13 ~ 14 °C, the Li2O grade of lithium concentrate is 6.01% and the recovery rate is 32.62%. When the water temperature is 16 °C after grinding and the stirring flotation temperature is 17-18 °C, the Li2O grade of lithium concentrate is 6.72% and the recovery rate is 64.49%. .

3.6 Rational use of drugs

For a long time, the flotation of spodumene mostly adopts the traditional two-alkali two soap-oil formula, but with the change of ore properties, the traditional formula can not reach a good flotation index. Different collectors have different collection properties for spodumene. For the selection of low-grade spodumene, modifiers and activators are also very important.

4 Major problems faced by spodumene ore flotation

At present, the main problems in the production of spodumene ore flotation can be summarized as follows:

(1) Research on the flotation behavior of major minerals in spodumene ore needs to be strengthened. At present, domestic and foreign scholars have mainly studied the physical and chemical properties of the actual ore in the spodumene ore and the main minerals in the spodumene ore. The research on the selective disintegration of the spodumene ore is still blank. The research on the flotation dynamic behavior of spodumene under different conditions is not enough. Strengthening the flotation kinetics of spodumene ore is beneficial to the regulation of the separation conditions of the spodumene flotation process and the improvement of flotation efficiency. In addition, the research work mainly focuses on the target mineral spodumene, but ignores the flotation behavior of its associated gangue minerals. Therefore, systematically studies the flotation behavior of different gangue minerals and its influence on the flotation behavior of spodumene. It seems very necessary.

(2) The performance of the spodumene ore flotation collector needs to be further improved. At present, most of the collectors used in the flotation have certain defects, mainly because the collection performance and the selection performance cannot be balanced. The performance is not strong in the ability to collect or foam, the selectivity is not good, and the agent is difficult to dissolve and disperse. High requirements for flotation equipment . Therefore, systematic research on the structure-activity relationship of spodumene ore flotation collectors and improving the performance of spodumene ore flotation collectors are still important research directions in the future.

(3) The selectivity of spodumene ore flotation separation inhibitors needs to be improved. Inhibitors commonly used in production practice are: water glass, starch, dextrin, lignosulfonate, Na2S, etc. However, these agents still have problems in many aspects such as environmental protection, dosage, and stability. For example, Na2S is a selective inhibitor used in the separation process of lithium lanthanum flotation, but Na2S is easily oxidized and fails, resulting in complicated process operation, high production volatility, and Na2S has certain toxicity, which can not meet the current The higher the environmental requirements.

(4) The flotation behavior of slime and its influence on the flotation behavior of spodumene, as well as the research on the efficient disposal technology of slime need to be strengthened. At present, most of the domestic plants adopt high-concentration, strong agitation, and multiple flotation and de-sludge flotation processes. These processes not only complicate the process, but also have a low de-sludge rate, which further deteriorates the subsequent flotation. The selection process has a low overall economic efficiency.

(5) At present, most of the domestic spodumene resources are located in areas above 3000 m above sea level, and the effects of thin air on the flotation process of spodumene ore (including the interaction between chemicals and minerals, and flotation equipment) Improvements, etc.) is a brand new topic that deserves high attention and research.

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