Low-temperature collecting agent for spodumene flotation and preparation method of low-temperature collecting agent

Abstract

The invention discloses a spodumene flotation low-temperature collecting agent and a preparation method thereof, and belongs to the technical field of mineral processing. The collecting agent can effectively solve the problems that an existing collecting agent is poor in dispersity and low in selectivity in low-temperature ore pulp. The preparation method of the collecting agent comprises the following steps: mixing oleic soap, isomeric alcohol polyoxyethylene ether and a specifically synthesized polyglycol ether-maleic anhydride-benzohydroximic acid terpolymer at a proper temperature, then adding specifically synthesized zwitterionic modified long-chain alkyl betaine and diethylene glycol monobutyl ether, and finally adding water for blending. Through the molecular design and synergistic effect of the two novel compounds, the dissolving dispersity of the collecting agent at the low temperature, the firm adsorbability of the collecting agent to the surface of spodumene and the selective repulsion capacity of the collecting agent to gangue minerals are remarkably enhanced, and therefore efficient and energy-saving flotation recovery of spodumene is achieved under the low-temperature condition without external heating.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of mineral processing, and particularly relates to a low-temperature collecting agent for spodumene flotation and a preparation method thereof. BACKGROUND

[0002] Spodumene is the main occurrence mineral of hard rock type lithium resources, and its efficient separation is a key link to guarantee the supply of lithium resources. Among many separation processes, flotation method has become the core technology for enriching spodumene due to its high efficiency and relatively low cost. This technology relies on the selective adsorption of collecting agent on the surface of target mineral to change its hydrophobicity, thereby realizing the separation from gangue minerals. However, in actual industrial production, especially in high-altitude mining areas in western China or in cold seasons, the temperature of the ore slurry is often in a low range, which brings a serious challenge to the traditional flotation process. Traditional fatty acid collectors, such as widely used oleic acid and its saponified products, have certain effects at room temperature, but their performance is highly dependent on temperature. In low-temperature ore slurry, the solubility of such reagents decreases significantly, the viscosity increases, and they are prone to crystallization and precipitation, which leads to a sharp deterioration of their dispersion in the ore slurry, and it is difficult for them to uniformly adsorb on the surface of the mineral. At the same time, low temperature also greatly reduces the reaction kinetics rate of the collecting agent molecules and the active sites on the surface of spodumene, making the adsorption process slow and not firm. The direct consequence is that the recovery rate of spodumene is significantly reduced, and the concentrate grade is decreased. In order to maintain production indicators, a large amount of ore slurry often has to be preheated, which not only consumes a large amount of energy and increases production costs, but also makes it extremely difficult to apply flotation technology in mining areas lacking heat sources.

[0003] To cope with the constraints of low temperature environment on flotation efficiency, the industry and research institutions have made many explorations and improvements. The early improvement ideas mainly focus on the physical compounding of reagents, such as adding alcohol, ether and other surfactants as auxiliary agents or dispersants to traditional collectors, in order to improve the emulsification and dispersion state of reagents in cold water. Another study attempts to introduce functional groups with stronger complexing ability, such as hydroxamic acid groups, to partially make up for the weakening of adsorption caused by low temperature by using their stronger specific chelation with aluminum and lithium sites on the surface of spodumene. Although these methods can alleviate the negative effects of low temperature to some extent, they do not fundamentally solve the problem. Physical compounding is difficult to change the low temperature properties of the main collector molecules themselves, and may introduce new complexity; and the introduction of stronger complexing groups cannot fully play its advantages if the overall behavior of the molecule in the low temperature medium is not addressed. In recent years, some studies have begun to focus on building a mixed collector system to improve low temperature performance by using the synergistic effect between different components of the reagent, such as the combination of anionic and cationic collectors. This kind of system can sometimes obtain a more stable adsorption layer through electrostatic attraction, co-adsorption and other mechanisms. However, this kind of scheme design often relies more on experience, the synergistic mechanism is not clear enough, and at lower temperatures, different components may not act in sync due to differences in physical and chemical properties, or even interfere with each other, leading to a decrease in selectivity, and the inhibition effect on common gangues such as feldspar and quartz is not ideal, limiting its wide application.

[0004] Therefore, developing a special collector for spodumene that can adapt to low temperature environment from the molecular design level, with good dispersibility, strong adsorption and high selectivity, has become the key to breaking through the current technical bottleneck. The ideal low-temperature collector should have the following characteristics: first, its molecular structure should contain a strong hydrophilic chain segment that can ensure good solubility and dispersion in cold water, avoiding self-aggregation; second, it must have a strong anchoring group that can form a firm and specific bond with the surface of spodumene, and this bond is less affected by temperature fluctuations; third, the overall molecular configuration should help form a dense and stable hydrophobic film on the surface of the target mineral, while producing steric hindrance or electrostatic repulsion on the surface of the gangue mineral, thereby strengthening the separation selectivity. Based on this, the present application aims to prepare two new modified compounds through innovative molecular design and synthesis, and to scientifically compound them to build a new flotation reagent system, in order to achieve efficient, energy-saving and high-selectivity recovery of spodumene in low-temperature ore slurry without relying on external heating. SUMMARY

[0005] The present application aims to provide a low-temperature collector for spodumene flotation and a preparation method thereof, which solves the technical problems of poor dispersibility, weak selectivity and weak adsorption of existing spodumene collectors in low-temperature ore slurry, resulting in the need to heat the ore slurry and high energy consumption.

[0006] The application achieves the above-mentioned purpose by the following technical solutions: A preparation method of a low-temperature collecting agent for spodumene flotation, comprising the following steps: S1, in a reaction kettle, deionized water is added, stirred and heated to 48-52℃; 15-30 parts of oleic acid soap and 5-15 parts of isomeric tridecanol polyoxyethylene ether are sequentially added; 20-40 parts of polyethylene glycol ether-maleic anhydride-benzohydroxamic acid terpolymer is added, and stirring is continued to obtain a mixture; S2, then the mixture is cooled to 35-40℃, 10-25 parts of a zwitterionic modified long-chain alkyl betaine and 3-10 parts of diethylene glycol monobutyl ether are added under stirring, and stirring is continued; deionized water is added and stirred to mix.

[0007] In the present invention, the final preparation of spodumene flotation low-temperature collector is not a simple physical mixing, but a "soft chemistry" process of inducing optimal intermolecular interaction between components through controllable process to build a stable and efficient composite reagent system. The reaction mechanism mainly reflects the interaction and functional integration of each functional component under specific temperature and sequence. In the first stage, in the moderately warm aqueous phase, first add oleic acid soap and isomeric alcohol polyoxyethylene ether. As a traditional anionic collector, the carboxylate ion of oleic acid soap can provide basic hydrophobicity and general affinity for minerals; as a nonionic surfactant, the polyoxyethylene chain of isomeric alcohol polyoxyethylene ether can strongly interact with water molecules through hydrogen bonds and embed into the micelles or aggregates of oleic acid soap, playing the role of emulsification, dispersion and reducing the freezing point and surface tension of the whole system. The subsequently added polyethylene glycol ether maleic anhydride benzohydroxamic acid terpolymer solid gradually dissolves in this mild heat environment. Its dissolution process is accompanied by full hydration of the polyether chain segment with the water environment and stretching of the polymer chain. More importantly, part of the carboxyl groups or unreacted polar groups on its chain may temporarily weakly bind with the oleic acid soap and nonionic surfactant through hydrogen bonds and dipole interactions, forming a dynamic and loose "pre-assembled body", which helps the uniform distribution and stability of each component in the solution and prevents phase separation at low temperature. In the second stage, after the system is cooled to near the target use temperature, the amphoteric ion modified long-chain alkyl betaine and low molecular weight ether solvent are added. The temperature control in this step is crucial, aiming to simulate low-temperature conditions and promote the adaptive assembly of each component under this condition. The addition of amphoteric ion compounds introduces strong steric hindrance and ion pair interactions. Its sulfonate and quaternary ammonium cation head group can be electrostatically attracted to the oppositely charged regions (such as the carboxylate of oleic acid soap and the partially protonated sites of the copolymer) in the "pre-assembled body" formed previously, while its large hydrated head group prevents disordered aggregation that could lead to precipitation. The addition of low molecular weight ether solvents further improves the low-temperature fluidity of the whole system and may insert into the hydrophobic regions of different molecules, playing the role of "plasticizing" and reducing viscosity. Finally, a uniform and transparent composite solution is formed by adding water and sufficient stirring. In this final product, the two new modified compounds play a structural role: the copolymer provides a strong chelating backbone throughout and low-temperature solubility; the amphoteric ion compound acts as a "molecular bridge" and "space stabilizer", optimizing the adsorption configuration of the entire composite on the mineral surface through electrostatic and steric effects, enabling it to rapidly diffuse and firmly anchor to the surface of spodumene at low temperatures, while effectively repelling gangue minerals, achieving a perfect unity from molecular design to macroscopic performance.

[0008] According to the preferred embodiment of the present invention, in step S1, the time for continuing stirring is 60-80 min.

[0009] According to the preferred embodiment of the present application, the time for continuing stirring in step S2 is 90-120 min.

[0010] According to the preferred embodiment of the present application, the preparation method of the polyethylene glycol ether-maleic anhydride-benzhydroxamic acid terpolymer comprises: A1, under the protection of dry nitrogen, adding methoxyl polyethylene glycol and anhydrous xylene into a four-necked flask, heating to 115-125℃, and stirring to obtain a mixture; cooling the mixture to 84-86℃, and adding maleic anhydride and p-toluenesulfonic acid successively, and stirring to obtain a reaction solution; dissolving azobisisobutyronitrile in anhydrous N,N-dimethylformamide, and dropping into the reaction solution, and reacting at 88-92℃ to obtain a reaction mixture; A2, cooling the reaction mixture to 58-62℃, adding benzhydroxamic acid and 4-dimethylaminopyridine, and reacting at 68-72℃ under the protection of nitrogen to obtain a mixture; cooling the mixture to room temperature, and rotary evaporation to obtain a product, dissolving the product in deionized water, adjusting the pH to 7-8, and then dropping into cold acetone under stirring for precipitation purification, collecting the solid precipitate by filtration, and drying in a vacuum drying oven at 38-42℃.

[0011] In the present application, the synthesis of the polyethylene glycol ether-maleic anhydride-benzhydroxamic acid terpolymer is a well-designed sequential reaction process, and the core mechanism is to first construct a polymer main chain with active reaction sites, and then precisely graft high selectivity chelating groups. The first step is the polymerization reaction. Methoxyl polyethylene glycol is used as a macromonomer, and the terminal hydroxyl group is capped with a methoxyl group, but the polyether long chain itself can serve as a flexible hydrophilic backbone. The key is that the reaction is essentially a free radical copolymerization reaction between the double bond of maleic anhydride and the trace amount of unsaturated end groups that may exist in the polyether chain or the chain radical sites generated under the action of the initiator. The azobisisobutyronitrile added as an initiator decomposes to generate free radicals under heat, thereby initiating the ring-opening polymerization and chain growth of maleic anhydride. In this process, p-toluenesulfonic acid plays a dual role, on the one hand, it may catalyze the ring-opening of maleic anhydride, and on the other hand, it ensures that the reaction system is in a water-free acidic environment, preventing maleic anhydride from prematurely hydrolyzing into a diacid, thereby ensuring its high reactivity. The polymer intermediate main chain formed in this step is composed of polymaleic anhydride, and the side chain is suspended with a polyethylene glycol ether long chain, and the polymer chain is rich in highly active anhydride five-membered ring structures. The second step is the functionalization grafting reaction, which is the key to endowing the molecule with strong adsorption ability at low temperature. After cooling the reaction system, benzhydroxamic acid and catalyst dimethylamino pyridine are added, and the reaction is carried out under nitrogen protection. The core reaction of this step is the nucleophilic ring-opening reaction between the hydroxamic acid group in the benzhydroxamic acid molecule and the highly active anhydride ring on the polymer side chain. Specifically, the nitrogen or oxygen atom of the hydroxamic acid group acts as a nucleophile to attack the carbonyl carbon of the anhydride, causing the anhydride ring to open, forming an acyloxy oxime acid structure containing both ester and amide bonds. This structure is a well-known strong metal chelating group, and its nitrogen and oxygen atoms can form stable five-membered ring chelates with aluminum ions and lithium ions on the surface of spodumene, with a very high binding constant. Dimethylamino pyridine as a highly efficient acylation catalyst greatly accelerates this nucleophilic substitution process. Finally, through acid-base adjustment and solvent precipitation purification, the target product obtained is a comb-shaped polymer with both hydrophilic polyether chain segments and strong chelating hydroxamic acid head groups. Among them, the polyether long chain maintains the molecule stretched and prevents self-aggregation in low-temperature aqueous solution through steric hindrance and hydrogen bonding, while multiple hydroxamic acid groups provide a guarantee for multi-point and firm anchoring on the mineral surface.

[0012] According to the preferred embodiment of the present application, in step A1, the reaction time at 88-92°C is 8-10h.

[0013] According to the preferred embodiment of the present application, in step A2, the reaction time at 68-72°C under nitrogen atmosphere is 12-14h.

[0014] According to the preferred embodiment of the present application, the preparation method of the zwitterionic modified long-chain alkyl betaine comprises: B1, in a high-pressure reaction kettle, N,N-dimethyl hexadecylamine and isopropanol are added, and the temperature is raised to 65-70 DEG C; under stirring, dry chloromethane gas is introduced, and the reaction is carried out at 70-75 DEG C; after the reaction is completed, pressure is released and cooling is carried out, to obtain an intermediate mixture; B2, the intermediate mixture is subjected to rotary evaporation, to obtain long-chain alkyl trimethyl ammonium chloride crude product; the long-chain alkyl trimethyl ammonium chloride crude product is dissolved in a mixed solvent composed of water and ethanol, sodium 3-chloro-2-hydroxypropyl sulfonate and sodium hydroxide are added, the temperature is raised to 78-82 DEG C to reflux, to obtain a reaction liquid; the reaction liquid is cooled to room temperature, rotary evaporation is carried out, the obtained crude product is recrystallized with ethanol, filtration is carried out, to obtain crystals, and the crystals are subjected to vacuum drying.

[0015] In the present application, the synthesis of the zwitterionic modified long-chain alkyl betaine follows the strategy of step-by-step molecular construction, aiming to create a dual hydrophilic headgroup zwitterionic structure which carries both permanent positive and negative charges and has a long hydrophobic tail. The first step is quaternary ammonium reaction, aiming to construct the hydrophobic core and the first cationic center of the molecule. The long-chain alkyl tertiary amine is dissolved in isopropanol, and reacts with chloromethane gas under heating and pressurization. Chloromethane, as an electrophilic reagent, is attacked by the lone pair of electrons on the nitrogen atom of the tertiary amine, and a bimolecular nucleophilic substitution reaction occurs. The nitrogen atom forms a new carbon-nitrogen bond with the methyl carbon, and the valence state of the nitrogen atom changes from three to five, carrying a permanent positive charge, to generate long-chain alkyl trimethyl ammonium chloride. This step is carried out under closed pressurization conditions, aiming to improve the concentration and mass transfer efficiency of the gaseous reactant, to ensure the complete quaternary ammonium reaction. The second step is the Williamson etherification reaction, which is a key step for introducing the second anionic hydrophilic headgroup. The quaternary ammonium salt intermediate obtained in the previous step is dissolved in a mixed solvent of water and ethanol together with sodium trichloro-2-hydroxypropyl sulfonate, and sodium hydroxide is added. In this alkaline environment, the terminal hydroxyl group carried by isopropanol or generated by the reaction of the quaternary ammonium salt molecule forms an alkoxide anion under the action of sodium hydroxide, which is a strong nucleophile. The alkoxide anion immediately attacks the chlorine atom connected to the sulfonic acid group in the sodium trichloro-2-hydroxypropyl sulfonate molecule, and another round of bimolecular nucleophilic substitution reaction occurs. The chlorine atom is removed as a leaving group, and the oxygen atom of the alkoxide anion forms a new carbon-oxygen ether bond with the propyl carbon atom, thereby covalently connecting the side chain containing the sulfonic acid group to the quaternary ammonium salt molecule. The newly introduced sulfonic acid group exists in the form of sulfonate anion under the conditions of the reaction system. Therefore, in the final product molecule, the same nitrogen atom is both the center of the quaternary ammonium cation and is connected to the sulfonate anion through an ether bond, forming a unique "inner salt" or zwitterionic structure. The long alkyl chain provides hydrophobic driving force, while the closely adjacent but oppositely charged hydrophilic headgroups endow the molecule with excellent hydration capacity and spatial volume, enabling it to produce a significant steric exclusion effect when adsorbed at the interface.

[0016] According to the preferred embodiment of the present application, the reaction time in step B1 is 6-8h at 70-75℃.

[0017] According to the preferred embodiment of the present application, the reaction time in step B2 is 24-30h at 78-82℃.

[0018] The present application also provides a lithium aluminosilicate flotation low-temperature collector prepared according to the preparation method of the lithium aluminosilicate flotation low-temperature collector.

[0019] The present application has the following beneficial effects: The lithium aluminosilicate flotation low-temperature collector and the preparation method thereof provided by the present application fundamentally overcome the inherent defects of traditional collectors in low-temperature environment through innovative molecular design and delicate composite process, and achieve significant and multi-faceted technical effects. The core effect is that the physical and chemical behavior of the collector in the low-temperature ore pulp is completely changed, so that the collector can not only maintain excellent dissolution and dispersion state under low-temperature conditions, but also realize high-strength and high-selectivity specific adsorption on the surface of lithium aluminosilicate, thereby breaking the dependence on external heating of the ore pulp, and providing a new solution for efficient separation of lithium aluminosilicate in low-temperature environment.

[0020] Specifically, the technical effects of the present application are first derived from the synergistic effect of two new structural modified compounds. The first compound, i.e. the polyethylene glycol ether-maleic anhydride-benzhydroxamic acid terpolymer, integrates multiple functional units in its molecular structure. The long chain of polyethylene glycol ether provides strong steric hindrance and hydration, ensuring that the entire molecule can fully stretch and dissolve in cold water, effectively preventing ineffective agglomeration or crystallization precipitation between molecules due to low temperature, which is the basis for realizing high-efficiency dispersion of the collector under low temperature. At the same time, the benzhydroxamic acid group on the polymer backbone serves as a strong chelating head group, which has much stronger affinity for the aluminum-lithium active sites on the surface of lithium aluminosilicate than traditional carboxylic acids, and can still undergo firm chemical adsorption under low-temperature kinetic unfavorable conditions, forming a stable five-membered ring chelate structure, thereby ensuring the strength and persistence of the collecting force. The second compound, i.e. the zwitterionic modified long-chain alkyl betaine, plays the role of an "intelligent regulator". Its unique dual hydrophilic head group structure is electrically neutral in the ore pulp, but can be flexibly combined with various sites on the mineral surface through dipole interaction, on the one hand, it can assist the co-adsorption of the main collector on the surface of lithium aluminosilicate, enhancing the integrity and stability of the hydrophobic film; on the other hand, when it is close to the surface of gangue minerals such as quartz and feldspar, it will produce strong steric hindrance effect and interfacial hydration film repulsion, thereby selectively inhibiting the floating of gangue, greatly improving the selectivity of the flotation process. The combination of these two compounds realizes the perfect combination of "strong anchoring" and "intelligent screening".

[0021] Finally, the comprehensive application effect brought by the present application is very outstanding. In actual low-temperature flotation tests, using the present collector can directly obtain high recovery rate and high grade of spodumene concentrate in low-temperature ore pulp without any preheating treatment, and the separation efficiency is even better than that of the traditional collector at normal temperature. This not only greatly reduces the huge energy consumption and production cost caused by ore pulp heating, simplifies the process flow, but also makes it possible to carry out spodumene flotation production in high-cold areas or winter, significantly expands the range and production cycle of the ore mine. In addition, the synergistic effect of each component in the collector formula is strong, the dosage is relatively saved, the synthetic raw materials are easy to obtain, the preparation process is stable and controllable, and it has good industrial production and popularization application prospect, which provides strong key technical support for the resource guarantee of lithium battery new energy industry. DETAILED DESCRIPTION

[0022] The following further describes the present application, and it is necessary to point out here that the following detailed description is only used to further illustrate the present application, and cannot be understood as limiting the protection scope of the present application. Those skilled in the art can make some non-essential improvements and adjustments to the present application according to the above application content.

[0023] Example 1

[0024] Preparation of poly(ethylene glycol ether)-maleic anhydride-hydroxamic acid terpolymer: A 2 L four-necked flask was charged with methoxypoly(ethylene glycol) (molecular weight 1000) 100.0 g and anhydrous xylene 300 mL under a dry nitrogen atmosphere. A mechanical stirrer, a thermometer, a condenser, and a nitrogen inlet were installed. The stirring was started at 200 rpm and the heating was started at a rate of 3 °C / min. The reaction mixture was warmed to 120 °C and stirred at this temperature for 30 min, and the water was removed azeotropically through a drying tube connected to the upper end of the condenser. Subsequently, the reaction system was cooled to 85 °C using an oil bath, and the nitrogen flow was maintained during the cooling. Maleic anhydride 30.0 g and a catalyst p-toluenesulfonic acid 2.0 g were sequentially added to the reaction flask, and the stirring speed was increased to 300 rpm. The stirring was continued for about 20 min until all the solids were completely dissolved, and a clear and uniform reaction solution was obtained. Initiator azobisisobutyronitrile 1.5 g was dissolved in 10 mL of anhydrous N,N-dimethylformamide, and the solution was transferred to a constant pressure dropping funnel. The dropping speed was controlled, and the initiator solution was slowly and uniformly added to the reaction system over 1 h. The temperature of the reaction solution was maintained at 90 ± 1 °C during the dropping. After the dropping was completed, the reaction system was continuously stirred at 90 °C for 9 h, and the nitrogen atmosphere and the stirring speed of 300 rpm were maintained during the reaction. After the reaction was completed, the oil bath temperature was decreased to 60 °C, and the reaction mixture was naturally cooled to this temperature. Subsequently, hydroxamic acid 35.0 g and a catalyst 4-dimethylaminopyridine 0.5 g were added to the reaction system. After the nitrogen was replaced again, the reaction system was stirred at 70 °C for 13 h at a stirring speed of 300 rpm. After the reaction was completed, the oil bath was removed, and the reaction mixture was naturally cooled to 25 °C (room temperature). The reaction mixture was transferred to a rotary evaporator, and the xylene solvent was completely removed by rotary evaporation at a water bath temperature of 60 °C and a vacuum degree of -0.095 MPa to obtain a light yellow viscous product. The viscous product was dissolved in 200 mL of deionized water, and a 10 wt% aqueous sodium carbonate solution was slowly added dropwise under stirring to adjust the pH to 7.5. The obtained aqueous solution was added dropwise in a fine stream to 1000 mL of acetone, which was previously cooled to 4 °C, under vigorous stirring (500 rpm), and white flocculent precipitates were immediately generated. After the dropping was completed, the stirring was continued in an ice water bath for 30 min. The white solid precipitate was collected by vacuum filtration through a Buchner funnel. The precipitate was washed twice with a small amount of cold acetone (about 50 mL, 4 °C). The filter cake was transferred to a watch glass and dried in a vacuum drying oven at 40 °C under a vacuum of -0.09 MPa for 24 h. After drying, a white solid powder of the product, i.e., poly(ethylene glycol ether)-maleic anhydride-hydroxamic acid terpolymer, was obtained, and the weight was measured and recorded.

[0025] Preparation of zwitterionic modified long chain alkyl betaine: Into a 500 mL stainless steel autoclave, N, N-dimethylhexadecylamine 50.0 g and isopropanol 150 mL were added. A magnetic stir bar was installed and the autoclave was sealed. The stirring was turned on with a speed setting of 400 rpm and heating was started to bring the reaction mixture to 68 °C to dissolve the amine completely. Dry chloromethane gas was introduced into the autoclave through a gas inlet valve and the pressure of the reaction system was controlled at 0.5 MPa by a back pressure valve. The reaction temperature was controlled at 72 °C and the stirring was continued for 7 h under these conditions. During the reaction, the internal conditions were monitored by a pressure gauge and a temperature indicator on the autoclave. After the reaction was completed, the heating was turned off and the autoclave was cooled in a cold water bath to below 35 °C. The pressure relief valve was slowly opened to release the residual pressure in the autoclave. The autoclave was opened and the resulting intermediate mixture was transferred to a 500 mL round bottom flask. The round bottom flask was connected to a rotary evaporator and rotary evaporation was performed at 50 °C water bath and -0.095 MPa vacuum to remove isopropanol and unreacted chloromethane completely to give a light yellow waxy solid, which was the crude long chain alkyl trimethylammonium chloride. The crude product was placed in a 500 mL three necked flask together with sodium 3-chloro-2-hydroxypropyl sulfonate 40.0 g. A mixed solvent consisting of 100 mL deionized water and 100 mL absolute ethanol was added. A mechanical stirrer, a condenser and a thermometer were installed. The stirring was started (300 rpm) and sodium hydroxide 8.0 g was added to the system. The heating was turned on to 80 °C and the stirring and reflux were continued for 28 h. After the reaction was completed, the heating was turned off and the reaction solution was allowed to cool to 25 °C naturally. The solution was transferred to a rotary evaporator and rotary evaporation was performed at 65 °C water bath and -0.095 MPa vacuum to remove most of the solvent to give a viscous paste of the crude product. Absolute ethanol 100 mL was added to the crude product and the solution was heated to 60 °C and stirred to dissolve the product again. The solution was then transferred to a beaker and placed in a refrigerator at 4 °C to recrystallize for 12 h. White flaky crystals were precipitated. The crystals were collected by vacuum filtration through a Buchner funnel. The crystals were washed quickly with a small amount of cold ethanol (about 20 mL, 4 °C) twice. The filter cake was placed in a vacuum drying oven at 50 °C and -0.09 MPa for 6 h to give the product as white crystals, which was the zwitterionic modified long chain alkyl betaine, and was weighed and recorded.

[0026] Preparation of lithium spodumene flotation low temperature collector: Into a 1 L glass reaction kettle equipped with an anchor type stirring blade, a thermometer and a condenser, 200 g of deionized water was added. The stirring was started with a rotation speed set at 150 rpm and the water bath heating was started to increase the water temperature to 50 °C. Once the temperature was stabilized, 22.0 g of oleic acid soap and 10.0 g of isomeric tridecanol polyoxyethylene ether (EO = 9) were added to the reaction kettle in sequence, the stirring rotation speed was increased to 300 rpm and the mixture was stirred for 15 min to form a homogeneous emulsion. The temperature was maintained at 50 °C and the stirring rotation speed was maintained at 300 rpm, and 30.0 g of the previously prepared polyethylene glycol ether-maleic anhydride-benzohydroxamic acid terpolymer was added slowly in portions over a period of about 10 min. After the addition was completed, the conditions were maintained (50 °C, 300 rpm) for an additional 70 min of stirring to ensure complete dissolution and dispersion of the terpolymer and to obtain a homogeneous mixture. Subsequently, the water bath was switched to a circulating cooling water system and the cooling rate was controlled to decrease the temperature of the mixture in the reaction kettle to 38 °C. The temperature was maintained at 38 °C and the stirring rotation speed was maintained at 300 rpm, and 18.0 g of the previously prepared zwitterion-modified long-chain alkyl betaine and 6.0 g of diethylene glycol monobutyl ether were added in sequence. After the addition was completed, the stirring was continued under these conditions for 100 min. Finally, the heating was stopped and the stirring was continued, and deionized water was added to the reaction kettle to make the total mass of the final product exactly 500 g. The stirring rotation speed was adjusted to 200 rpm and the mixing was continued for 30 min, after which the stirring was stopped and the product was discharged. The product obtained was a light amber colored translucent liquid which did not separate into layers or precipitate when left standing for 24 h at 25 °C, and this was the lithium spodumene flotation low temperature collector of the present invention.

[0027] Example 2

[0028] The preparation method is the same as that in Example 1, except that the preparation of polyethylene glycol ether-maleic anhydride-benzhydroxamic acid terpolymer: under the protection of dry nitrogen, a 2L four-necked flask was charged with methoxypolyethylene glycol (molecular weight 1000) 120.0 g and anhydrous xylene 360 mL. A mechanical stirrer, a thermometer, a condenser and a nitrogen inlet were installed. Start stirring at 200 rpm, and start heating at a rate of 3°C / min. The reaction mixture was heated to 118°C and stirred at this temperature for 30 min to remove water by azeotropic distillation. Subsequently, the reaction system was cooled to 85°C. Maleic anhydride 25.0 g and catalyst p-toluenesulfonic acid 2.0 g were added to the reaction flask in turn, and the stirring speed was increased to 300 rpm, and the stirring was continued for about 20 min until complete dissolution. The initiator azobisisobutyronitrile 1.5 g was dissolved in 10 mL of anhydrous N,N-dimethylformamide, and was slowly added to the reaction system through a constant pressure dropping funnel within 1 h, and the reaction liquid temperature was maintained at 89°C during the dropping process. After the dropping was completed, the reaction system was continuously stirred at 90°C for 8 h. After the reaction was completed, the reaction mixture was cooled to 59°C. Benzhydroxamic acid 30.0 g and catalyst 4-dimethylaminopyridine 0.5 g were added to the reaction system. Under the protection of nitrogen, the reaction system was stirred at 69°C for 12 h. After the reaction was completed, the reaction mixture was naturally cooled to 25°C. The reaction mixture was rotary evaporated to remove the solvent at 60°C water bath and -0.095 MPa vacuum. The viscous product was dissolved in 240 mL of deionized water, and 10 wt% sodium carbonate aqueous solution was added dropwise to adjust the pH value to 7.2. The aqueous solution was added dropwise into 1200 mL of acetone previously cooled to 4°C under vigorous stirring to precipitate. It was filtered through a Buchner funnel and the precipitate was washed with cold acetone. The filter cake was placed in a vacuum drying oven at 40°C for 24 h to obtain polyethylene glycol ether-maleic anhydride-benzhydroxamic acid terpolymer.

[0029] Preparation of zwitterion-modified long-chain alkyl betaine: A 500 mL autoclave was charged with N,N-dimethylhexadecylamine 55.0 g and isopropyl alcohol 165 mL. The stirring was started at 400 rpm and the reaction mixture was heated to 67 °C. Dry chloromethane gas was bubbled into the reaction mixture and the pressure was controlled at 0.48 MPa and the temperature at 71 °C for 6 h. After the reaction was completed, the reactor was cooled and depressurized. The intermediate mixture was transferred and the solvent was removed by rotary evaporation to give a crude product. The crude product was charged into a 500 mL three-necked flask with sodium 3-chloro-2-hydroxypropyl sulfonate 35.0 g and a mixed solvent of 110 mL deionized water and 110 mL absolute ethanol was added. The stirring was started and sodium hydroxide 7.0 g was added. The temperature was raised to 79 °C and the reaction was stirred for 24 h. After the reaction was completed, the reactor was cooled and the solvent was removed by rotary evaporation. Absolute ethanol 100 mL was added to the crude product and the mixture was heated to dissolve the product. The solution was cooled to 4 °C and the crystals were collected by filtration. The crystals were washed with cold ethanol and dried at 50 °C under vacuum for 6 h to give zwitterion-modified long-chain alkyl betaine.

[0030] Preparation of lithium spodumene flotation low-temperature collector: A 1 L glass reactor was charged with 200 g deionized water. The stirring was started at 150 rpm and the reactor was heated to 49 °C in a water bath. Oleic acid soap 28.0 g and isomeric tridecanol polyoxyethylene ether (EO = 9) 13.0 g were added sequentially and the stirring speed was increased to 300 rpm. The temperature and stirring were maintained and the previously prepared polyethylene glycol ether-maleic anhydride-benzohydroxamic acid terpolymer 25.0 g was added slowly. The stirring was continued for 65 min after the addition was completed. The temperature of the reactor was lowered to 36 °C and the stirring was maintained. The previously prepared zwitterion-modified long-chain alkyl betaine 22.0 g and diethylene glycol monobutyl ether 4.0 g were added sequentially and the stirring was continued for 110 min after the addition was completed. Finally, deionized water was added to make the total mass 500 g and the stirring speed was adjusted to 200 rpm. The mixture was stirred for 30 min and the collector was discharged.

[0031] Example 3

[0032] The preparation method is the same as in Example 1, except that the preparation of the polyethylene glycol ether-maleic anhydride-benzohydroxamic acid terpolymer: Into a 2 L four-necked flask, under dry nitrogen protection, was added methoxylated polyethylene glycol (molecular weight 1000) 80.0 g and anhydrous xylene 240 mL. A mechanical stirrer, thermometer, condenser and nitrogen inlet were installed. The stirring was started at 200 rpm, and the temperature was raised to 122°C and stirred for 30 min for azeotropic dehydration. Then the temperature was lowered to 86°C. Maleic anhydride 35.0 g and catalyst p-toluenesulfonic acid 2.0 g were added successively, and the stirring speed was increased to 300 rpm and stirred until dissolved. Initiator azobisisobutyronitrile 1.5 g was dissolved in 10 mL of anhydrous N,N-dimethylformamide and added dropwise to the reaction system within 1 h, and the temperature was maintained at 91°C during the dropwise addition. After the dropwise addition was completed, the reaction was stirred at 92°C for 10 h. After the reaction was completed, the temperature was lowered to 61°C. Benzohydroxamic acid 40.0 g and catalyst 4-dimethylaminopyridine 0.5 g were added, and the reaction was stirred at 71°C for 14 h under nitrogen atmosphere. After the reaction was completed, the temperature was cooled to 25°C. The solvent was removed by rotary evaporation, and the product was dissolved in 160 mL of deionized water, and the pH was adjusted to 7.8. The solution was added dropwise to 800 mL of acetone at 4°C for precipitation. After filtration and washing, the solid was dried in a vacuum drying oven at 42°C for 24 h to obtain the polyethylene glycol ether-maleic anhydride-benzohydroxamic acid terpolymer.

[0033] Preparation of zwitterion-modified long-chain alkyl betaine: Into a 500 mL high-pressure reaction kettle was added N,N-dimethylhexadecylamine 45.0 g and isopropyl alcohol 135 mL. The mixture was heated to 70°C with stirring. Chloromethane gas was introduced, and the pressure was controlled at 0.52 MPa and the temperature at 74°C, and the reaction was carried out for 8 h. After cooling and depressurizing, the mixture was concentrated by rotary evaporation to obtain a crude product. The crude product was placed in a three-necked flask with sodium 3-chloro-2-hydroxypropyl sulfonate 45.0 g, and a mixed solvent of 90 mL of deionized water and 90 mL of anhydrous ethanol was added. Sodium hydroxide 9.0 g was added with stirring. The temperature was raised to 81°C, and the reaction was carried out with reflux stirring for 30 h. After the reaction, the mixture was cooled and concentrated by rotary evaporation. The crude product was recrystallized from 100 mL of anhydrous ethanol, and after standing at 4°C, the crystals were filtered. The crystals were dried in a vacuum drying oven at 50°C for 6 h to obtain the zwitterion-modified long-chain alkyl betaine.

[0034] Preparation of low temperature collector for spodumene flotation: A 1 L reactor was charged with 200 g of deionized water. The mixture was stirred and heated to 52 °C. Oleic acid soap 18.0 g and isomeric tridecanol polyoxyethylene (EO = 9) ether 7.0 g were added sequentially and stirred for 15 min at 300 rpm. The previously prepared polyethylene glycol ether-maleic anhydride-benzohydroxamic acid terpolymer 35.0 g was added and stirring was continued for 75 min. The mixture was cooled to 40 °C. The previously prepared zwitterionically modified long chain alkyl betaine 14.0 g and diethylene glycol monobutyl ether 9.0 g were added and stirring was continued for 95 min. Deionized water was added to make the total mass 500 g. After mixing for 30 min at 200 rpm, the collector was discharged.

[0035] Comparative Example 1

[0036] The preparation method was the same as Example 1, except that the preparation of the low temperature collector for spodumene flotation: A 1 L glass reactor was charged with 200 g of deionized water. The stirring (150 rpm) was started and the water bath was heated to 50 °C. Oleic acid soap 50.0 g and isomeric tridecanol polyoxyethylene (EO = 9) ether 10.0 g were added, and the stirring speed was increased to 300 rpm, and stirring was continued for 70 min. Then the mixture was cooled to 38 °C. Diethylene glycol monobutyl ether 6.0 g was added with stirring, and stirring was continued for 100 min. Finally, deionized water was added to make the total mass 500 g. The stirring speed was adjusted to 200 rpm, and mixing was continued for 30 min before the comparative collector was discharged.

[0037] Comparative Example 2

[0038] The preparation method was the same as Example 1, except that the preparation of the zwitterionically modified long chain alkyl betaine: The preparation method was exactly the same as Example 1. The preparation of the low temperature collector for spodumene flotation: A 1 L glass reactor was charged with 200 g of deionized water. The stirring (150 rpm) was started and the water bath was heated to 50 °C. Oleic acid soap 22.0 g and isomeric tridecanol polyoxyethylene (EO = 9) ether 10.0 g were added sequentially and stirred for 15 min at 300 rpm, and then stirring was continued for a total of 70 min. The mixture was cooled to 38 °C. The previously prepared zwitterionically modified long chain alkyl betaine 18.0 g and diethylene glycol monobutyl ether 6.0 g were added with stirring, and stirring was continued for 100 min. Finally, deionized water was added to make the total mass 500 g. After mixing for 30 min at 200 rpm, the comparative collector was discharged.

[0039] Comparative Example 3

[0040] The preparation method is the same as that in Example 1, except that the preparation of polyethylene glycol ether-maleic anhydride-benzohydroxamic acid terpolymer: the preparation method is exactly the same as that in Example 1. Preparation of spodumene flotation low-temperature collector: into a 1L glass reaction kettle, 200g deionized water was added. Start stirring (150rpm), and heat to 50℃ in a water bath. Add oleic acid soap 22.0g and isomeric tridecanol polyoxyethylene ether (EO=9) 10.0g in turn, and stir at 300rpm for 15min. Maintain the conditions, and slowly add the polyethylene glycol ether-maleic anhydride-benzohydroxamic acid terpolymer prepared above 30.0g, and continue stirring for 70min after the addition is completed. Cool the mixture to 38℃. Add diethylene glycol monobutyl ether 6.0g under stirring, and continue stirring for 100min. Finally, make up with deionized water to a total mass of 500g, and mix at 200rpm for 30min before discharging to obtain the comparative collector.

[0041] Performance test and result analysis

[0042] According to the existing national and industry standards, the performance of the spodumene flotation low-temperature collectors prepared in Examples 1-3 and Comparative Examples 1-3 was tested by the following methods: The test sample was a pegmatite type lithium spodumene ore from a certain place, which was crushed and sieved to obtain a-2mm size sample for use. Chemical analysis showed that the raw ore had a Li2O grade of 1.25%, and the main gangue minerals were sodium feldspar, quartz and a small amount of mica. The performance test was carried out in a laboratory type hanging tank flotation machine, and 500.0g of ore sample was taken for each flotation experiment. The ore sample was placed in an XMQ-67 type 240mmx90mm conical ball mill, and deionized water was added for grinding until the-0.074mm content was 75%, and the grinding concentration was controlled at 65%. The ground ore slurry was transferred to a 1.5L flotation tank, and deionized water was added to adjust the ore slurry concentration to 30%. The flotation machine was started and stirred at a speed of 1992r / min. First, sodium hydroxide solution was added to adjust the pH of the ore slurry to 7.5, and stirred for 2min; then water glass was added as depressant at a dosage of 200g / t (based on dry ore), and stirred for 3min; then the collector prepared in different examples or comparative examples was added, and stirred for 5min; finally, the air charging valve was opened, and the air charging amount was 0.25m³ / h, and the roughing was scraped for 5min. The whole flotation process was carried out in a low-temperature water bath circulation system, and the temperature of the ore slurry was constant at 10.0±0.5℃ throughout the process. The concentrate foam product and the tank tailings were collected, filtered, dried, weighed, sampled and sent to the laboratory for determination of Li2O content by atomic absorption spectrometry. According to the weight and grade of the concentrate and tailings, the recovery rate of lithium spodumene, concentrate grade, enrichment ratio and selectivity index were calculated. Each collector was tested in triplicate under the same conditions, and the average value was taken as the final test result.

[0043] Table 1: Performance test results of each example and comparative example

[0044] As can be seen from Table 1, the collectors represented by Examples 1 to 3 successfully and comprehensively solve the core technical problems faced by existing spodumene collectors in low-temperature slurry environments through systematic comparison with Comparative Examples 1-3.

[0045] First, in terms of the "poor dispersibility" problem, Examples 1-3 achieved much higher recovery rates (89.2% vs. 71.3%) at a lower dosage of only 450 g / t than Comparative Example 1 (600 g / t), which directly indicates that the strong hydrated head groups of the polyethylene glycol ether hydrophilic long chain and the zwitterionic compound introduced by the terpolymer in the present application greatly improve the solubility and dispersion of the reagent molecules in low-temperature water, ensuring that effective molecules can fully contact the minerals, thereby achieving higher recovery rates at lower dosages and overcoming the defects of traditional collectors that easily agglomerate at low temperatures, requiring increased dosages or heating to maintain effectiveness.

[0046] Second, in terms of the "weak selectivity" and "poor adsorption" problems, the concentrate grade (up to 4.52%) and selectivity index (up to 3.87) of Examples 1-3 are significantly better than those of Comparative Examples 1-3. In particular, compared with Comparative Example 2 (concentrate grade 3.20%, selectivity index 2.45) and Comparative Example 3 (concentrate grade 4.05%, selectivity index 3.22) which only contain a single functional component, the examples achieve the highest recovery rate and selectivity index while maintaining high grade, which reveals the indispensable synergistic mechanism of the two modified compounds: the benzohydroxamic acid group in the terpolymer provides a firm chelating anchoring effect on the surface of spodumene, solving the problem of low-temperature adsorption strength; and the zwitterionic compound effectively suppresses the floating of gangue minerals through its unique steric hindrance and electrostatic effect, together greatly improving the selectivity of separation.

[0047] Finally, the comprehensive performance indicators show that the collector of the present application can achieve simultaneous optimization of high recovery rate and high-grade concentrate at low temperature without any external heating, and its performance is even better than that of traditional collectors at higher dosages, fundamentally solving the industry pain point of "having to heat the slurry to overcome the low-temperature bottleneck, resulting in high energy consumption", and achieving the core goal of energy saving and consumption reduction.

Claims

1. A process for the preparation of a low temperature collector for spodumene flotation of lithium, characterized by the steps of The application relates to a lithium spodumene low-temperature collector and a preparation method thereof. S1, adding deionized water into a reaction kettle, stirring and heating to 48-52 DEG C; sequentially adding 15-30 parts of oleic acid soap and 5-15 parts of isomeric tridecanol polyoxyethylene ether; adding 20-40 parts of polyethylene glycol ether-maleic anhydride-benzohydroxamic acid terpolymer, continuing to stir to obtain a mixture; S2, then cooling the mixture to 35-40 DEG C, adding 10-25 parts of a zwitterionic modified long-chain alkyl betaine and 3-10 parts of diethylene glycol monobutyl ether under stirring, continuing to stir; adding deionized water and stirring to mix.

2. The method for preparing the low-temperature collector for spodumene flotation according to claim 1, characterized in that, In step S1, the time for continuing to stir is 60-80 min.

3. The method for preparing the low-temperature collector for spodumene flotation according to claim 1, characterized in that, In step S2, the time for continuing to stir is 90-120 min.

4. The method for preparing the low-temperature collector for spodumene flotation according to claim 1, characterized in that, The preparation method of the polyethylene glycol ether-maleic anhydride-benzohydroxamic acid terpolymer comprises the following steps: A1, under the protection of dry nitrogen, adding methoxyl polyethylene glycol and anhydrous xylene into a four-necked flask, heating to 115-125 DEG C, stirring to obtain a mixture; cooling the mixture to 84-86 DEG C, sequentially adding maleic anhydride and p-toluenesulfonic acid, stirring to obtain a reaction solution; dissolving azobisisobutyronitrile in anhydrous N, N-dimethylformamide, dropping into the reaction solution, reacting at 88-92 DEG C to obtain a reaction mixture; A2, cooling the reaction mixture to 58-62 DEG C, adding benzohydroxamic acid and 4-dimethylaminopyridine, reacting at 68-72 DEG C under the atmosphere of nitrogen to obtain a mixture; cooling the mixture to room temperature, rotary evaporation to obtain a product, dissolving the product in deionized water, adjusting the pH to 7-8, then dropping into cold acetone under stirring for precipitation purification, collecting the solid precipitate through filtration, and drying in a vacuum drying box at 38-42 DEG C.

5. The method of claim 4, wherein the lithium spodumene low temperature collector is prepared by the steps of: In step A1, the reaction time at 88-92 DEG C is 8-10 h.

6. The method of claim 4, wherein the lithium spodumene low temperature collector is prepared by the steps of: In step A2, the reaction time at 68-72 DEG C under the atmosphere of nitrogen is 12-14 h.

7. The method of claim 1, wherein the low temperature lithium spodumene flotation collector is prepared by the steps of: The preparation method of the zwitterionic modified long-chain alkyl betaine comprises the following steps: B1, adding N, N-dimethylhexadecylamine and isopropyl alcohol into a high-pressure reaction kettle, heating to 65-70 DEG C; under stirring, introducing dry chloromethane gas, reacting at 70-75 DEG C, discharging pressure after the reaction is completed, and cooling to obtain an intermediate mixture; B2, rotary evaporation is conducted on the intermediate mixture to obtain long-chain alkyl trimethylammonium chloride crude product; dissolving the long-chain alkyl trimethylammonium chloride crude product and 3-chloro-2-hydroxypropyl sulfonic acid sodium in a mixed solvent composed of water and ethanol, adding sodium hydroxide, heating to 78-82 DEG C to reflux, obtaining a reaction solution; cooling the reaction solution to room temperature, rotary evaporation, recrystallizing the obtained crude product with ethanol, filtering to obtain crystals, and vacuum drying the crystals.

8. The method of claim 7, wherein the lithium spodumene low temperature collector is prepared by the steps of: In step B1, the reaction time at 70-75 DEG C is 6-8 h.

9. The method of claim 7, wherein the lithium spodumene low temperature collector is prepared by the steps of: In step B2, the time for heating to 78-82 DEG C to reflux is 24-30 h.

10. A low temperature collector for spodumene flotation, characterized in that, The lithium spodumene low-temperature collector is prepared according to the preparation method of the lithium spodumene low-temperature collector in any one of claims 1-9.

Images