Thallium removal method for thallium-containing solution in process of extracting lithium from lepidolite

Abstract

The invention provides a thallium removal method for a thallium-containing solution in a process of extracting lithium from lepidolite, and the method comprises the following steps: pumping the thallium-containing solution into a first-stage reaction kettle, adding a first mixing agent, stirring for reaction, and filtering to obtain a first-stage thallium-removed solution and first-stage thallium-removed slag; and pumping the first-stage thallium removal liquid into a second-stage reaction kettle, adding a second mixing agent, stirring for reaction, standing, and filtering to obtain second-stage thallium removal liquid and second-stage thallium removal slag. According to the thallium removal method for the thallium-containing solution in the lithium extraction process of lepidolite, thallium removal is carried out on the thallium-containing solution in two steps, the first step is carried out through the first mixing agent, the second step is carried out through the second mixing agent, no organic flocculant is used, rapid sedimentation can be achieved, no harmful gas is generated, the sludge amount is small, the process is short, and lithium loss is low; and efficient thallium removal in the process of extracting lithium from lepidolite is realized.

Description

Technical Field

[0001] The present application relates to the technical field of lithium extraction from lepidolite, and in particular to a method for removing thallium from a thallium-containing solution during lithium extraction from lepidolite. Background Art

[0002] In the process of preparing lithium carbonate from lepidolite, the trace element thallium contained in the lepidolite concentrate enters the leachate and wastewater along with the roasting and leaching processes. The thallium in lepidolite exists in the form of monovalent thallium. During roasting, part of it is carried out with the flue gas and finally enters the desulfurization wastewater through the desulfurization process; thallium enters the leachate during clinker leaching, and a large amount of waste salt is generated when the low-concentration lithium-containing solution is subsequently concentrated and enriched. The leaching toxicity of thallium in the waste salt is ≥1000ppb. If the front-end thallium removal process is not carried out, a large amount of solid hazardous waste and thallium-containing wastewater will be generated.

[0003] At present, there is little research on the process of removing thallium in the process of lithium extraction from lepidolite. Most thallium removal processes are mainly aimed at thallium-containing wastewater, mainly including oxidation, sulfidation, adsorption, electrocoagulation, etc. The oxidation and sulfidation methods are suitable for wastewater with a high initial thallium concentration, which requires subsequent flocculation and treatment of a large amount of hazardous waste, and the sulfidation method will produce a large amount of harmful hydrogen sulfide gas. The adsorption method has a long treatment time, a small treatment volume, and requires frequent regeneration of the adsorption material. Summary of the invention

[0004] The present application provides a method for removing thallium from a thallium-containing solution during lithium extraction from lepidolite, which is beneficial to improving thallium removal efficiency.

[0005] In a first aspect, an embodiment of the present application provides a method for removing thallium from a thallium-containing solution during lithium extraction from lepidolite, the method comprising:

[0006] The thallium-containing solution is pumped into a primary reaction kettle, and a first mixed agent is added, stirred for reaction, and filtered to obtain a primary thallium removal solution and a primary thallium removal slag; wherein the first mixed agent includes a first thallium removal agent (JLCT-A) formed by a mixture of an oxidant powder and a calcium sulfate whisker coated with manganese oxide;

[0007] The first-level thallium removal liquid is pumped into a second-level reaction kettle, and a second mixed agent is added, stirred for reaction, and filtered after standing to obtain a second-level thallium removal liquid and a second-level thallium removal slag; wherein the second mixed agent includes a second thallium removal agent (JLCT-B) made of manganese oxide and polysilicate; the second-level thallium removal liquid is used for preparing industrial lithium.

[0008] According to the first aspect, in a possible implementation manner, the first mixture includes a first thallium removal agent and the secondary thallium removal slag.

[0009] According to the first aspect, in a possible implementation, the first mixture includes: 55-75 parts of the first thallium removal agent and 25-45 parts of the secondary thallium removal slag.

[0010] According to the first aspect, in a possible implementation manner, the method includes:

[0011] Add calcium sulfate whiskers to the aqueous solution at a ratio of 1 g: 5 ml to 20 ml, and stir thoroughly to form a calcium sulfate suspension;

[0012] Adding 1% to 5% by volume of a polysilicate in an aqueous solution and 5% to 10% by mass of a manganese oxide in the calcium sulfate suspension to the calcium sulfate suspension, and stirring evenly at 60° C. to 80° C. to form a first hydrogel;

[0013] Drying the first hydrogel to obtain a first xerogel; the drying temperature is 60° C. to 100° C., and the drying time is 4 h to 8 h;

[0014] grinding the first xerogel to obtain manganese oxide-coated calcium sulfate whiskers;

[0015] The oxidant powder is mixed with the manganese oxide-coated calcium sulfate whisker to obtain a first thallium removing agent (JLCT-A).

[0016] According to the first aspect, in a possible implementation, the mass percentage of the oxidant powder and the manganese oxide is 10% to 30%: 70% to 90%;

[0017] According to the first aspect, in a possible implementation manner, the method includes:

[0018] Weigh 30-80 parts of manganese oxide and 10-40 parts of polysilicate,

[0019] Adding the polysilicate into the aqueous solution according to a preset addition ratio to prepare a suspension with a mass concentration of 5% to 10%;

[0020] adding manganese oxide to the suspension and stirring to form a mixed solution;

[0021] Adding 1% to 3% water glass by volume fraction into the mixed solution, stirring evenly at 40° C. to 60° C., to form a second hydrogel;

[0022] Drying the second hydrogel to obtain a second xerogel; the drying temperature is 60° C. to 80° C., and the drying time is 5 h to 10 h;

[0023] The second xerogel was ground to obtain a second thallium removing agent (JLCT-B).

[0024] According to the first aspect, in a possible implementation manner, the oxidant powder includes at least one of potassium permanganate, sodium permanganate, calcium permanganate, zinc permanganate, sodium perchlorate, potassium perchlorate, potassium ferrate, and sodium ferrate.

[0025] According to the first aspect, in a possible implementation, the manganese oxide includes at least one of manganese oxide, manganese dioxide, and trimanganese tetraoxide; and / or,

[0026] The polysilicate includes at least one of polysodium silicate, polycalcium silicate, polyaluminum silicate, polymagnesium silicate and polyferric silicate.

[0027] According to the first aspect, in a possible implementation, in the step of pumping the thallium-containing solution into a primary reactor, adding a first mixed agent, stirring the reaction, filtering, and obtaining a primary thallium removal solution and a primary thallium removal slag, the mass ratio of the first thallium removal agent (JLCT-A) in the first mixed agent to the thallium ions in the thallium-containing solution is 100 to 200:1.

[0028] According to the first aspect, in a possible implementation, in the step of pumping the primary thallium removal liquid into a secondary reactor, adding a second mixed agent, stirring the reaction, letting it stand and then filtering to obtain a secondary thallium removal liquid and a secondary thallium removal slag, the mass ratio of the second thallium removal agent (JLCT-B) to the thallium ions in the primary thallium removal liquid is 50 to 100:1.

[0029] The present application provides a method for removing thallium from a thallium-containing solution during lithium extraction from lepidolite. The thallium-containing solution is removed from the solution in two steps, the first step being carried out using a first mixed agent, and the second step being carried out using a second mixed agent. No organic flocculant is used, rapid sedimentation can be achieved, no harmful gas is generated, the amount of sludge is small, the process is short, and lithium loss is low, thereby achieving efficient thallium removal during lithium extraction from lepidolite. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to more clearly illustrate the implementation methods of the present application or the technical solutions in the prior art, the drawings required for use in the implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some implementation methods of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0031] Figure 1 It is a schematic flow chart of a method for removing thallium from a thallium-containing solution in a lithium extraction process of lepidolite in one embodiment of the present application;

[0032] Figure 2 It is a schematic flow chart of a method for removing thallium from a thallium-containing solution in a lithium extraction process of lepidolite in another embodiment of the present application;

[0033] Figure 3 It is a schematic flow chart of a method for removing thallium from a thallium-containing solution in a lithium extraction process from lepidolite in another embodiment of the present application; DETAILED DESCRIPTION

[0034] The words "preferably", "more preferably", etc. in the present invention refer to embodiments of the present invention that may provide certain beneficial effects in certain circumstances. However, other embodiments may also be preferred under the same circumstances or other circumstances. In addition, the description of one or more preferred embodiments does not imply that other embodiments are not applicable, nor is it intended to exclude other embodiments from the scope of the present invention.

[0035] When a numerical range is disclosed herein, the above range is considered to be continuous and includes the minimum and maximum values ​​of the range, as well as every value between such minimum and maximum values. Further, when a range refers to an integer, every integer between the minimum and maximum values ​​of the range is included. In addition, when multiple ranges are provided to describe features or characteristics, the ranges can be combined. In other words, unless otherwise indicated, all ranges disclosed herein should be understood to include any and all subranges included therein.

[0036] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of the present invention.

[0037] Unless otherwise specified, the reagents, methods and equipment used in the present invention are conventional reagents, methods and equipment in the art.

[0038] This application provides a method for removing thallium from a thallium-containing solution during lithium extraction from lepidolite. Figure 1 In one embodiment, the method comprises:

[0039] Step S10, pumping the thallium-containing solution into a primary reaction kettle, adding a first mixed agent, stirring for reaction, filtering, and obtaining a primary thallium removal solution and a primary thallium removal slag;

[0040] The thallium concentration of the thallium-containing solution is 1-5 mg / L, that is, the thallium-containing solution can be suitable for the thallium-containing solution produced in each stage of the entire process of lithium extraction from lepidolite, including lepidolite leaching solution, desulfurization waste liquid, lithium precipitation mother liquor, high-salt waste liquid, rainwater in the production area and various slag washing water treatment.

[0041] The first mixed agent includes a first thallium removing agent (JLCT-A) formed by a mixture of an oxidant powder and a calcium sulfate whisker coated with manganese oxide.

[0042] The first mixture is put into a primary reactor and mixed with a thallium-containing solution. The oxidant powder in the first mixture is first used to oxidize the monovalent thallium ions in the thallium-containing solution into trivalent thallium ions. The calcium sulfate whiskers in the first mixture are a single crystal material with a specific needle shape, which can produce sufficient pores between its particles, have the characteristics of low density, large specific surface area, non-toxicity and easy to compound with polymers. After being coated with manganese oxide, the surface of these whiskers tightly adsorbs manganese oxide, making it difficult for manganese oxide to fall off. Manganese oxide has a good adsorption capacity for trivalent thallium ions, and can efficiently adsorb and remove oxidized trivalent thallium ions. Through the dual effects of precipitation and adsorption, the efficient removal of thallium ions in the solution is achieved.

[0043] During the synthesis of the first mixture, the calcium sulfate whiskers may be modified with polysilicate to enhance their surface activity, thereby improving the adsorption efficiency of thallium ions.

[0044] The first mixture is added in step S10 according to the mass ratio of the first thallium removal agent to thallium ions being 100 to 200:1, and the synthesized first mixture is added to the thallium-containing solution for use. The reaction parameters in step S10 are: stirring speed 200 rpm to 400 rpm, and reaction time 10 min to 30 min. In actual operation, the amount of the first mixture added and the reaction conditions (such as stirring speed, reaction time, etc.) can be reasonably adjusted according to the concentration and characteristics of the thallium-containing solution to ensure the best thallium removal effect.

[0045] Step S10 can remove 70-90% of the thallium ions in the thallium-containing solution.

[0046] Step S20, pumping the primary thallium removal liquid into a secondary reaction kettle, adding a second mixed agent, stirring for reaction, standing and filtering to obtain a secondary thallium removal liquid and a secondary thallium removal slag;

[0047] The second mixed agent includes a second thallium removal agent (JLCT-B) made of manganese oxide and polysilicate; the secondary thallium removal solution is used to prepare industrial lithium. Manganese oxide has a good adsorption capacity for trivalent thallium ions (Tl3+), while polysilicate can strengthen this adsorption mechanism. Through precipitation, adsorption and co-coagulation, the composite thallium removal agent can deeply remove the remaining trivalent thallium ions in the solution. It is worth noting that this process does not require the addition of additional flocculants, thereby simplifying the operation process and reducing processing costs.

[0048] After the treatment in step S20, the remaining thallium ions in the primary thallium removal solution are further removed, so that the thallium concentration in the secondary thallium removal solution reaches an extremely low level. This step not only ensures the purity of the final product, but also reduces the pollution to the environment. The secondary thallium removal solution can then be used to prepare industrial lithium, such as lithium carbonate, to meet the quality requirements of lithium products in the process of lithium extraction from lepidolite.

[0049] The second mixture is added in step S20 according to the mass ratio of the second thallium removal agent to thallium ions being 50 to 100:1; the synthesized second mixture is added to the primary thallium removal solution for use; the reaction parameters in step S20 are: stirring speed 200 rpm to 400 rpm, reaction adsorption time 10 min to 30 min;

[0050] In this embodiment, thallium is removed from the thallium-containing solution in two steps, the first step using the first mixed agent and the second step using the second mixed agent, thereby improving the thallium removal efficiency; and the thallium removal process does not produce harmful byproducts or secondary pollution.

[0051] In addition, the thallium removal method in this embodiment can utilize the original reactor in the lithium extraction process of lepidolite, without the need for additional equipment, simple operation, short reaction time, easy implementation, shortening the treatment process, saving the cost of structure construction, and reducing the cost of deep thallium removal from water bodies.

[0052] Plate and frame filtration can be used in both step S10 and step S20.

[0053] Specifically, in step S10, after the primary thallium removal reaction is completed, the reacted solution and solid residue need to be separated. At this time, a plate and frame filter press can be used for operation. The plate and frame filter press applies pressure to allow the solution to pass through the filter cloth, while the solid residue is trapped on the filter cloth, thereby achieving effective separation of the solution and the solid residue. Since more solid residue may be produced in the primary thallium removal reaction, the high filtration efficiency and powerful processing capacity of the plate and frame filter press are particularly important at this stage.

[0054] In step S20, after the secondary thallium removal reaction is completed, it is also necessary to separate the solution from the solid residue. Similar to step S10, a plate-frame filter press can also be used for operation at this time. Since the secondary thallium removal reaction may further remove the thallium ions in the solution and may produce finer solid particles, the fine filtering ability of the plate-frame filter press is also crucial at this stage. Through the treatment of the plate-frame filter press, the purity of the secondary thallium removal solution can be ensured, providing high-quality raw materials for the subsequent preparation of industrial lithium.

[0055] The second embodiment is different from the first embodiment in that, in the second embodiment, the first mixture includes a first thallium removal agent and the secondary thallium removal slag.

[0056] Since the second thallium removal agent in S20 adsorbs very little thallium, the moisture content of the secondary thallium removal slag is 1-5%; and under alkaline conditions, thallium ions are extremely difficult to separate from the secondary thallium removal slag, so the secondary thallium removal slag can be returned to S10 and used in conjunction with the first thallium removal agent (JLCT-A), thereby further improving the thallium removal efficiency; the reuse of the secondary thallium removal slag reduces waste emissions, reduces processing costs, and realizes the maximum utilization of resources. .

[0057] The secondary thallium removal slag is returned to S10 and used in combination with the first thallium removal agent (JLCT-A), and the ratio is 55-75 parts of the first thallium removal agent (JLCT-A) and 25-45 parts of the secondary thallium removal slag. Step S10 is performed according to the mass ratio of the first thallium removal agent (JLCT-A) to thallium ions being 100-200:1.

[0058] like Figure 2 As shown, the method for removing thallium from a thallium-containing solution in the process of extracting lithium from lepidolite includes the preparation of a first thallium removing agent, comprising the following steps:

[0059] Step S31, adding calcium sulfate whiskers into the aqueous solution at a ratio of 1 g: 5 ml to 20 ml, and stirring thoroughly to form a calcium sulfate suspension;

[0060] We need to add calcium sulfate whiskers to an appropriate amount of aqueous solution according to a specific addition ratio (1g of calcium sulfate whiskers corresponds to 5ml to 20ml of aqueous solution). Then, use a stirring device to fully stir the mixture to ensure that the calcium sulfate whiskers can be evenly dispersed in the aqueous solution to form a stable calcium sulfate suspension.

[0061] The stirring process should be sufficient and uniform to avoid local concentration being too high or too low, which will affect the stability of the calcium sulfate suspension. The prepared calcium sulfate suspension should be uniform milky white or off-white, without obvious precipitation or stratification.

[0062] When adding calcium sulfate whiskers, they can be added gradually and stirred while adding to avoid whisker agglomeration. The prepared calcium sulfate suspension should be used in the subsequent steps as soon as possible to avoid precipitation or deterioration due to long-term storage.

[0063] Step S32, adding 1% to 5% by volume of aqueous solution of polysilicate and 5% to 10% by mass of manganese oxide of the calcium sulfate suspension to the calcium sulfate suspension, stirring evenly at 60° C. to 80° C. to form a first hydrogel;

[0064] Stirring is performed at a temperature range of 60°C to 80°C. This temperature range helps accelerate chemical reactions and promote the formation of hydrogels. Stirring should be sufficient and uniform to ensure that all additives are evenly dispersed in the calcium sulfate suspension.

[0065] The polysilicate includes at least one of polysodium silicate, polycalcium silicate, polyaluminium silicate, polymagnesium silicate and polyferric silicate. The manganese oxide includes at least one of manganese oxide, manganese dioxide and manganese tetraoxide;

[0066] Step S33, drying the first hydrogel to obtain a first xerogel; the drying temperature is 60° C. to 100° C., and the drying time is 4 h to 8 h;

[0067] The first hydrogel is placed in a drying device and dried at a temperature range of 60°C to 100°C. This temperature range helps to effectively remove moisture from the hydrogel while avoiding excessively high temperatures that may damage the gel structure or degrade its performance. The drying process should last 4 to 8 hours to ensure that the moisture in the hydrogel is fully removed. The length of the drying time depends on the efficiency of the drying equipment, the water content of the gel, and the desired degree of drying. Hot air drying ovens, vacuum drying ovens, and other equipment may be used for drying.

[0068] Step S34, grinding the first dry gel to obtain manganese oxide-coated calcium sulfate whiskers;

[0069] Select appropriate grinding equipment, such as a ball mill, a vibration mill, an air flow mill, etc., to grind the first dry gel. The selection of equipment should be based on the hardness and toughness of the gel and the required grinding fineness. According to the type of grinding equipment and the properties of the gel, select appropriate grinding media, such as grinding balls, grinding rods or air flow, etc. The selection of grinding media should ensure that the gel can be effectively refined while avoiding excessive damage to the whiskers.

[0070] The grinding process should be continued for a sufficient time to ensure that the gel is fully refined and the manganese oxide-coated calcium sulfate whiskers are exposed. The length of the grinding time depends on the efficiency of the grinding equipment, the hardness of the gel and the desired grind fineness. After grinding, the ground product should be separated and purified by screening or centrifugation to remove impurities and fine powder generated during the grinding process.

[0071] Step S35, mixing the oxidant powder with the manganese oxide-coated calcium sulfate whisker to obtain a first thallium removing agent (JLCT-A).

[0072] The oxidant powder includes at least one of potassium permanganate, sodium permanganate, calcium permanganate, zinc permanganate, sodium perchlorate, potassium perchlorate, potassium ferrate and sodium ferrate.

[0073] According to the formula requirements, the oxidant powder is mixed with the manganese oxide coated calcium sulfate whisker in a mass percentage of 10% to 30%: 70% to 90%. This means that if we have 100g of manganese oxide coated calcium sulfate whisker, 10g to 30g of oxidant powder should be added for mixing.

[0074] The two can be fully mixed by mechanical mixing, air flow mixing, ultrasonic mixing and the like to ensure that the oxidant powder can be evenly distributed in the manganese oxide-coated calcium sulfate whiskers.

[0075] like Figure 3 As shown, the method for removing thallium from a thallium-containing solution in the process of extracting lithium from lepidolite includes the preparation of a second thallium removal agent, comprising the following steps:

[0076] Step S41, weighing 30 to 80 parts of manganese oxide and 10 to 40 parts of polysilicate,

[0077] The manganese oxide includes at least one of manganese oxide, manganese dioxide and manganese tetraoxide; the polysilicate includes at least one of polysodium silicate, polycalcium silicate, polyaluminum silicate, polymagnesium silicate and polyferric silicate. Manganese oxide plays a key role in the thallium removal process. Polysilicate provides additional structural stability and reactivity.

[0078] Step S42, adding the polysilicate into the aqueous solution according to a preset addition ratio to prepare a suspension with a mass concentration of 5% to 10%;

[0079] The calculated polysilicate is slowly added to the prepared aqueous solution, and fully stirred at the same time to ensure that the polysilicate can be evenly dispersed in the water to form a suspension with a mass concentration of 5% to 10%. This concentration range is selected to promote the uniform dispersion of manganese oxide in the subsequent steps and facilitate the formation of gel.

[0080] In the process of preparing the suspension, sufficient stirring is the key to ensure uniform dispersion of polysilicate. By stirring, the agglomeration between polysilicate particles can be broken, so that it can be better dispersed in water to form a uniform suspension.

[0081] Step S43, adding manganese oxide to the suspension and stirring to form a mixed solution;

[0082] Step S44, adding 1% to 3% water glass by volume fraction of the aqueous solution to the mixed solution, stirring evenly at 40° C. to 60° C. to form a second hydrogel;

[0083] Add 1% to 3% water glass in volume fraction to the mixed solution. Water glass is a commonly used inorganic gelling material, which can enhance the structural stability of the gel.

[0084] Stir evenly at a temperature of 40°C to 60°C to allow the water glass and the mixed liquid to fully react to form a second hydrogel. This temperature range helps to accelerate the chemical reaction and promote the formation of gel.

[0085] Step S45, drying the second hydrogel to obtain a second xerogel; the drying temperature is 60° C. to 80° C., and the drying time is 5 h to 10 h;

[0086] The formed second hydrogel is dried at a temperature of 60°C to 80°C for 5 h to 10 h. This drying process helps to remove moisture from the gel while maintaining its structural stability.

[0087] Step S46, grinding the second dry gel to obtain a second thallium removing agent (JLCT-B).

[0088] After drying, the second dry gel is ground to obtain the second thallium removal agent (JLCT-B). The grinding process should ensure that the particle size of the product is uniform so that the thallium removal effect can be fully exerted in subsequent applications.

[0089] According to the first aspect, in a possible implementation, in the step of pumping the thallium-containing solution into a primary reactor, adding a first mixed agent, stirring the reaction, filtering, and obtaining a primary thallium removal solution and a primary thallium removal slag, the mass ratio of the first thallium removal agent (JLCT-A) in the first mixed agent to the thallium ions in the thallium-containing solution is 100 to 200:1.

[0090] According to the first aspect, in a possible implementation, in the step of pumping the primary thallium removal liquid into a secondary reactor, adding a second mixed agent, stirring the reaction, letting it stand and then filtering to obtain a secondary thallium removal liquid and a secondary thallium removal slag, the mass ratio of the second thallium removal agent (JLCT-B) to the thallium ions in the primary thallium removal liquid is 50 to 100:1.

[0091] Example 1

[0092] In the case of lithium carbonate mainly produced by lithium extraction from lepidolite, a large amount of thallium-containing solutions such as leachate, lithium precipitation mother liquor, desulfurization wastewater, and rainwater in the production area are generated during the lithium extraction process. On average, more than 4,000 m3 of thallium-containing solutions need to be treated every day. These solutions contain more than 1 mg / L, and a large amount of potassium and sodium salts are generated during the secondary lithium precipitation process. If the front-end lepidolite leachate / lithium precipitation mother liquor thallium removal process is not considered, a large amount of potassium and sodium salt byproducts have a serious excess of thallium content, which is upgraded from general solid waste to solid hazardous waste. It is necessary to further spend high hazardous waste treatment costs and increase the production cost of lithium carbonate. If the traditional sulfidation method of excessive addition is adopted, additional thallium removal equipment is required, which increases the space pressure in the production area and is prone to hydrogen sulfide gas poisoning if not handled properly.

[0093] Preparation of the first thallium removal agent (JLCT-A):

[0094] Calcium sulfate whiskers are added to an aqueous solution at a ratio of 2kg:10000ml, and stirred sufficiently to form a calcium sulfate suspension. 200g of polysodium silicate with a volume fraction of 2% of the aqueous solution is added, and 600g of manganese dioxide is added to the suspension, and stirred uniformly at 60°C to form a hydrogel. The hydrogel is dried at 100°C for 4h to obtain a dry gel, and the obtained dry gel is ground to obtain manganese oxide-coated calcium sulfate whiskers; finally, 257g of potassium permanganate is mixed with the manganese oxide-coated calcium sulfate whiskers to obtain a first thallium removal agent (JLCT-A) for standby use.

[0095] Preparation of the second thallium removal agent (JLCT-B):

[0096] Weigh 30 g of manganese dioxide and 20 g of polysodium silicate, first prepare the silicate into a suspension with a mass concentration of 5%, then add manganese dioxide to the suspension, stir evenly, and add 12 ml of water glass, stir evenly at 40°C to form a hydrogel, dry the hydrogel at 80°C for 10 hours to obtain a dry gel, and grind the obtained dry gel to obtain a second thallium removal agent (JLCT-B) for later use.

[0097] The first thallium removal agent (JLCT-A) and the second thallium removal agent (JLCT-B) provided in Example 1 of the present invention are used to perform a thallium removal experiment on the lepidolite leachate in the workshop, which includes the following steps:

[0098] S1: 10m3 of lepidolite leachate with a thallium ion concentration of 2.1mg / L is pumped into a primary reactor, and a high-efficiency thallium removal agent (JLCT-A) is added. The mass ratio of the first thallium removal agent (JLCT-A) to the thallium ion is 100:1. The first thallium removal agent (JLCT-A) is added as follows: 2.1kg of the first thallium removal agent prepared in Example 1 is weighed and added to the leachate. The reactor is stirred at a speed of 300rpm, reacted for 20 minutes, allowed to stand and settle for 5min, and passed through a plate frame to obtain a primary thallium removal liquid and a primary thallium removal slag;

[0099] S2: The first-level thallium removal liquid obtained in step S1 is accurately detected by ICP-MS, and the thallium ion concentration of the first-level thallium removal liquid is 88.67μg / L, which has not yet reached the target value of water discharge. The first-level thallium removal liquid is pumped into the second-level reactor, and 44.4g of the second thallium removal agent (JLCT-B) is added. The mass concentration ratio of the second thallium removal agent (JLCT-B) to thallium ions is 50:1. The second thallium removal agent (JLCT-B) is added as follows: weigh the required mass and add it as a whole to the first-level thallium removal liquid. The reactor is stirred at a speed of 250rpm, reacted for 15 minutes, allowed to settle for 5 minutes, and passed through a plate frame to obtain a second-level thallium removal liquid and a second-level thallium removal slag.

[0100] The on-site treatment effect is shown in Table 1. The results show that the combination of the first thallium removal agent (JLCT-A) and the second thallium removal agent (JLCT-B) can stably reduce the thallium ion concentration in the lithium mica leachate to below 10μg / L, achieving the predetermined goal.

[0101] Table 1: On-site treatment results of thallium removal from lepidolite leachate (unit: μg / L)

[0102] Serial number Leachate (Tl) Primary Thallium Removal Liquid (Tl) Secondary Thallium Removal Solution (Tl) 1 2100 88.67 4.43

[0103] In addition, the effects of different proportions of the first thallium removal agent (JLCT-A) and the second thallium removal agent (JLCT-B) prepared in Example 1 were tested using the lithium mica leachate. The 2.1 mg / L batch leachate was uniformly used as the stock solution. The treatment effects are shown in Table 2. The results show that changing the first thallium removal agent (JLCT-A) and the second thallium removal agent (JLCT-B) according to different proportions can reduce the thallium ion concentration to below the predetermined target value of 10 μg / L.

[0104] Table 2: Thallium removal results of lepidolite leachate (thallium content unit: mg / L)

[0105] Serial number 2 3 4 Leachate(m3) 10 10 10 10 JLCT-A addition amount / g 2100 2500 2800 3000 JLCT-B addition amount / g 44.4 44.3 62.16 79.92 Leachate (Tl) 2.1 2.1 2.1 2.1 Primary Thallium Removal Liquid (Tl) 0.08867 0.07391 0.05527 0.09548 Secondary Thallium Removal Solution (Tl) 0.00443 0.00412 0.00528 0.00562

[0106] Example 2

[0107] Considering that the secondary thallium removal slag in the embodiment absorbs less thallium ions, and it is extremely difficult for thallium ions to be separated from the manganese oxide in situ under alkaline conditions, whether it can be recycled and reused, this embodiment still uses the lithium mica leachate as the research object, and the secondary thallium removal slag obtained in Example 1 is dried and dehydrated, and the moisture content is 2.3%. The preparation method of the first thallium removal agent (JLCT-A) and the second thallium removal agent (JLCT-B) used in this embodiment is consistent with that in Example 1. . The first thallium removal agent (JLCT-A) in this embodiment and the secondary thallium removal slag in Example 1 are mixed in a mass percentage ratio of 55%:45%.

[0108] S1: 10m3 of lepidolite leachate with a thallium ion concentration of 1.91mg / L is pumped into a primary reactor, and a first thallium removal agent (JLCT-A) is added (wherein the first thallium removal agent (JLCT-A) is composed of), the mass concentration ratio of the first thallium removal agent (JLCT-A) to the thallium ion is 100:1, and the first thallium removal agent (JLCT-A) is added as follows: 1050.5g of the first thallium removal agent (JLCT-A) prepared in Example 1 and 859.5g of the secondary thallium removal slag in Example 1 are weighed and added to the leachate, the reactor is stirred at a speed of 300rpm, reacted for 20 minutes, allowed to stand and settle for 5min, passed through a plate frame, and a primary thallium removal solution and a primary thallium removal slag are obtained;

[0109] S2: The first-level thallium removal liquid obtained in step S1 is accurately detected by ICP-MS, and the thallium ion concentration of the first-level thallium removal liquid is 108.33μg / L, which has not yet reached the target value of the effluent. The first-level thallium removal liquid is pumped into the second-level reactor, and 44.4g of the second thallium removal agent (JLCT-B) is added. The mass concentration ratio of the second thallium removal agent (JLCT-B) to the thallium ion is 50:1. The second thallium removal agent (JLCT-B) is added as follows: weigh the required mass and add it as a whole to the first-level thallium removal liquid. The reactor is stirred at a speed of 250rpm, reacted for 15 minutes, allowed to settle for 5 minutes, and passed through a plate frame to obtain a second-level thallium removal liquid and a second-level thallium removal slag.

[0110] The on-site treatment effect is shown in Table 3. The results show that the secondary thallium removal slag can be recycled as the first thallium removal agent for secondary utilization, and the thallium ion concentration in the lithium mica leachate can be stably reduced to below 15μg / L.

[0111] Table 3: On-site treatment results of thallium removal from lepidolite leachate (unit: μg / L)

[0112] Serial number Leachate (Tl) Primary Thallium Removal Liquid (Tl) Secondary Thallium Removal Solution (Tl) 1 1910 108.33 3.37

[0113] Example 3

[0114] Lepidolite concentrate is mainly a silicate layered mineral composed of potassium, lithium, silicon, aluminum and other elements. During the lithium extraction process of lepidolite sulfate roasting, lithium is leached out along with a large amount of sodium, potassium, sulfate and other ions. The sodium and potassium ions in the lithium precipitation mother liquor obtained by subsequent lithium precipitation are close to saturation. As shown in Table 4, the lithium precipitation mother liquor belongs to a high-salt solution. The thallium ion concentration in the lithium precipitation mother liquor is 1-3 mg / L. The ordinary sulfidation method and the commonly used thallium removal agents and thallium removal processes are not effective in removing thallium in high-salt solutions, and there are problems such as large slag volume and serious lithium loss.

[0115] Table 4: Typical composition of lithium precipitation mother liquor in lithium extraction from lepidolite

[0116] Thallium mg / L Sodium g / L Potassium g / L Sulfate g / L 1.56 40.5 19.6 90.5

[0117] Preparation of the first thallium removal agent (JLCT-A):

[0118] Calcium sulfate whiskers are added to an aqueous solution at a ratio of 2kg:10000ml, and stirred sufficiently to form a calcium sulfate suspension. 300g of polysodium silicate with a volume fraction of 3% of the aqueous solution is added, and 984g of manganese dioxide is added to the suspension, and stirred evenly at 60°C to form a hydrogel. The hydrogel is dried at 100°C for 4h to obtain a dry gel. The obtained dry gel is ground to obtain manganese oxide-coated calcium sulfate whiskers; finally, 246g of potassium ferrate is mixed with the manganese oxide-coated calcium sulfate whiskers to obtain a first thallium removal agent (JLCT-A) for standby use.

[0119] Preparation of the second thallium removal agent (JLCT-B):

[0120] Weigh 60 g of manganese dioxide and 40 g of polysodium silicate, first prepare the sodium silicate into a suspension with a mass concentration of 5%, then add manganese dioxide to the suspension, stir evenly, and add 12 ml of water glass, stir evenly at 40°C to form a hydrogel, dry the hydrogel at 80°C for 10 hours to obtain a dry gel, and grind the obtained dry gel to obtain a second thallium removal agent (JLCT-B) for later use.

[0121] The present embodiment provides a method for efficiently removing thallium in a lithium extraction process of lepidolite, which comprises the following steps:

[0122] S1: 10m3 of lithium precipitation mother liquor with a thallium ion concentration of 1.56mg / L is pumped into a primary reactor, and a first thallium removal agent (JLCT-A) is added. The mass concentration ratio of the first thallium removal agent (JLCT-A) to thallium ions is 100:1. The first thallium removal agent (JLCT-A) is added in the following manner: 1560g of the first thallium removal agent (JLCT-A) is weighed and added to the lithium precipitation mother liquor. The reactor is stirred at a speed of 300rpm, reacted for 25 minutes, allowed to stand and settle for 5min, and passed through a plate frame to obtain a primary thallium removal liquid and a primary thallium removal slag.

[0123] S2: The primary thallium removal liquid obtained in step S1 is accurately detected by ICP-MS and has not yet reached the target water output value. The primary thallium removal liquid is pumped into the secondary reactor, and the second thallium removal agent (JLCT-B) is added. The mass concentration ratio of the second thallium removal agent (JLCT-B) to thallium ions is 50:1. The second thallium removal agent (JLCT-B) is added as follows: manganese dioxide, manganese oxide, and polysodium silicate are mixed according to the mass ratio and added to the primary thallium removal liquid as a whole. The reactor is stirred at a speed of 300 rpm, reacted for 15 minutes, allowed to settle for 5 minutes, and passed through a plate frame to obtain a secondary thallium removal liquid and a secondary thallium removal slag.

[0124] The on-site treatment effect is shown in Table 5. The results show that the combination of the first thallium removal agent (JLCT-A) and the second thallium removal agent (JLCT-B) can stably reduce the thallium ion concentration in the lithium precipitation mother liquor to below 10μg / L, achieving the predetermined goal.

[0125] Table 5: Field results of thallium removal from lithium precipitation mother liquor (unit: μg / L)

[0126] Batch number Lithium precipitation mother liquor (Tl) Primary Thallium Removal Liquid (Tl) Secondary Thallium Removal Solution (Tl) 1 1560 76.93 3.11 2 1560 79.44 3.94

[0127] Example 4

[0128] In the experiment of removing thallium from lithium precipitation mother liquor in lithium extraction from lepidolite, the water source was the same as in Example 3, and the polysilicate was replaced with polycalcium silicate during the preparation of the high-efficiency thallium removal agent (JLCT-A) and the second thallium removal agent (JLCT-B). The other parameters and preparation process were consistent with those in Example 3.

[0129] The process of treating the lithium precipitation mother liquor by adjusting different proportions of the first thallium removal agent (JLCT-A) and the second thallium removal agent (JLCT-B) according to the present invention is as follows:

[0130] S1: Pump lithium precipitation mother liquor with thallium ion concentration of 1.56 mg / L into the primary reactor, add high-efficiency thallium removal agent (JLCT-A), stir the reactor at 300 rpm, react for 25 minutes, let it stand for 5 minutes, pass through the plate frame, and obtain the primary thallium removal liquid and the primary thallium removal slag;

[0131] S2: The first-level thallium removal liquid obtained in step S1 is accurately detected by ICP-MS, and the water outlet target value has not yet been reached. The first-level thallium removal liquid is pumped into the second-level reactor, and the second thallium removal agent (JLCT-B) is added. The reactor is stirred at a speed of 300rpm, reacted for 15 minutes, and allowed to settle for 5 minutes. After passing through the plate frame, the second thallium removal liquid and the second thallium removal slag are obtained.

[0132] The on-site treatment effect is shown in Table 6. The results show that the first thallium removal agent (JLCT-A) and the second thallium removal agent (JLCT-B) can stably reduce the thallium ion concentration in the lithium precipitation mother liquor to below 10μg / L, achieving the predetermined goal. The effect is still stable and good when the component ratio of the first thallium removal agent is adjusted.

[0133] Table 6: Field results of thallium removal from lithium precipitation mother liquor (unit: μg / L)

[0134]

[0135] After the lithium precipitation mother liquor is dethalliumed by the present invention, the solution is concentrated to obtain salt by MVR, and the concentrated solution is further frozen step by step to obtain mirabilite. The potassium and sodium salts before and after the dethallium removal are subjected to leaching toxicity tests, which can meet the general solid waste requirements. Table 7 shows the leaching toxicity test results of potassium and sodium mixed salts before and after the dethallium removal.

[0136] Table 7: Leaching toxicity test results of potassium and sodium salts before and after thallium removal in lithium precipitation mother liquor

[0137]

[0138] The present invention uses the first thallium removal agent (JLCT-A) and the second thallium removal agent (JLCT-B) to remove thallium from the leaching solution and the lithium precipitation mother liquor. Compared with the traditional sulfidation method, the present invention mainly shows the characteristics of high efficiency in thallium removal, small amount of slag, and low lithium loss. Table 8 mainly compares the differences between the traditional sulfidation method and the present invention in thallium removal.

[0139] Table 8: Comparison of the present invention and the traditional sulfidation process for removing thallium (target value of thallium ions in effluent water ≤ 10 μg / L)

[0140]

[0141] Test Example 1

[0142] In order to explore the practicality of the first thallium removal agent (JLCT-A) and the second thallium removal agent (JLCT-B) in the present invention for removing thallium from different water samples, this test case conducted thallium removal experiments on the rainwater collection pool, ground washing water and various types of slag washing water in the factory area. After ICP-MS detection, the thallium ion concentrations of desulfurization waste liquid, rainwater collection pool, ground washing water and various types of slag washing water were 0.046, 0.31 and 0.874 mg / L respectively.

[0143] Preparation of the first thallium removal agent (JLCT-A):

[0144] Calcium sulfate whiskers are added to an aqueous solution at a ratio of 100 g:500 ml, and stirred sufficiently to form a calcium sulfate suspension. 10 g of polysodium silicate with a volume fraction of 2% of the aqueous solution is added, and then 11 g of manganese dioxide is added to the suspension, and stirred evenly at 50° C. to form a hydrogel. The hydrogel is dried at 100° C. for 4 hours to obtain a dry gel. The obtained dry gel is ground to obtain manganese oxide-coated calcium sulfate whiskers; finally, 4 g of potassium permanganate is mixed with the manganese oxide-coated calcium sulfate whiskers to obtain a first thallium removal agent (JLCT-A) for standby use.

[0145] Preparation of the second thallium removal agent (JLCT-B):

[0146] Weigh 15 g of manganese dioxide and 11 g of polysodium silicate, first prepare the silicate into a suspension with a mass concentration of 5%, then add manganese dioxide to the suspension, stir evenly, and add 2 ml of water glass, stir evenly at 40°C to form a hydrogel, dry the hydrogel at 80°C for 10 hours to obtain a dry gel, and grind the obtained dry gel to obtain a second thallium removal agent (JLCT-B) for later use.

[0147] The treatment process is as follows: S1: 5 liters of the liquid to be treated is taken into a beaker, the first thallium removal agent (JLCT-A) is added, the stirring speed is 200 rpm, the reaction is carried out for 20 minutes, the sedimentation is allowed to stand, and the supernatant is taken for detection. S2: The second thallium removal agent (JLCT-B) is added to the supernatant obtained in S1, the stirring speed is 200 rpm, the reaction is carried out for 20 minutes, the sedimentation is allowed to stand, and the supernatant is taken for detection. The treatment effect is shown in Table 9.

[0148] Table 9: Experimental results of different types of wastewater containing thallium

[0149]

[0150] According to the test results, the thallium-containing solution in the rainwater collection pool only needs to undergo primary treatment with the first thallium removal agent (JLCT-A) according to the above components to meet the national standard requirement of less than 5μg / L, while ground washing water and various slag washing waters require secondary thallium removal before they can be discharged.

[0151] The applicant declares that the present invention illustrates the detailed method of the present invention through the above-mentioned embodiments, but the present invention is not limited to the above-mentioned detailed method, that is, it does not mean that the present invention must rely on the above-mentioned detailed method to be implemented. Those skilled in the art should understand that any improvement of the present invention, equivalent replacement of the method of the present invention, addition of auxiliary steps, selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

Claims

1. A method for removing thallium from a thallium-containing solution in a lithium extraction process of lepidolite, characterized in that: The method comprises: The thallium-containing solution is pumped into a primary reaction kettle, and a first mixed agent is added, stirred for reaction, and filtered to obtain a primary thallium removal solution and a primary thallium removal slag; wherein the first mixed agent includes a first thallium removal agent (JLCT-A) formed by a mixture of an oxidant powder and a calcium sulfate whisker coated with manganese oxide; The first-level thallium removal liquid is pumped into a second-level reaction kettle, and a second mixed agent is added, stirred for reaction, and filtered after standing to obtain a second-level thallium removal liquid and a second-level thallium removal slag; wherein the second mixed agent includes a second thallium removal agent (JLCT-B) made of manganese oxide and polysilicate; the second-level thallium removal liquid is used for preparing industrial lithium.

2. The method for removing thallium from thallium-containing solution in the lithium extraction process of lepidolite according to claim 1, characterized in that: The first mixed agent includes a first thallium removal agent and the secondary thallium removal slag.

3. The method for removing thallium from thallium-containing solution in the lithium extraction process of lepidolite according to claim 2, characterized in that: The first mixed agent includes: 55-75 parts of the first thallium removal agent and 25-45 parts of the secondary thallium removal slag.

4. The method for removing thallium from thallium-containing solution in the lithium extraction process of lepidolite according to claim 1, characterized in that: The method comprises: Add calcium sulfate whiskers to the aqueous solution at a ratio of 1 g: 5 ml to 20 ml, and stir thoroughly to form a calcium sulfate suspension; Adding 1% to 5% by volume of a polysilicate in an aqueous solution and 5% to 10% by mass of a manganese oxide in the calcium sulfate suspension to the calcium sulfate suspension, and stirring evenly at 60° C. to 80° C. to form a first hydrogel; Drying the first hydrogel to obtain a first xerogel; the drying temperature is 60° C. to 100° C., and the drying time is 4 h to 8 h; grinding the first xerogel to obtain manganese oxide-coated calcium sulfate whiskers; The oxidant powder is mixed with the manganese oxide-coated calcium sulfate whisker to obtain a first thallium removing agent (JLCT-A).

5. The method for removing thallium from thallium-containing solution in the lithium extraction process of lepidolite according to claim 4, characterized in that: The mass percentage of the oxidant powder and the manganese oxide is 10% to 30%: 70% to 90%.

6. The method for removing thallium from thallium-containing solution in the lithium extraction process of lepidolite according to claim 4, characterized in that: The oxidant powder includes at least one of potassium permanganate, sodium permanganate, calcium permanganate, zinc permanganate, sodium perchlorate, potassium perchlorate, potassium ferrate and sodium ferrate.

7. The method for removing thallium from thallium-containing solution in the lithium extraction process of lepidolite according to claim 1, characterized in that: The method comprises: Weigh 30-80 parts of manganese oxide and 10-40 parts of polysilicate, Adding the polysilicate into the aqueous solution according to a preset addition ratio to prepare a suspension with a mass concentration of 5% to 10%; adding manganese oxide to the suspension and stirring to form a mixed solution; Adding 1% to 3% water glass by volume fraction into the mixed solution, stirring evenly at 40° C. to 60° C., to form a second hydrogel; Drying the second hydrogel to obtain a second xerogel; the drying temperature is 60° C. to 80° C., and the drying time is 5 h to 10 h; The second xerogel was ground to obtain a second thallium removing agent (JLCT-B).

8. The method for removing thallium from a thallium-containing solution in a lithium extraction process of lepidolite according to any one of claims 4 to 6, characterized in that: The manganese oxide includes at least one of manganese oxide, manganese dioxide and trimanganese tetraoxide; and / or, The polysilicate includes at least one of polysodium silicate, polycalcium silicate, polyaluminum silicate, polymagnesium silicate and polyferric silicate.

9. The method for removing thallium from thallium-containing solution in the lithium extraction process of lepidolite according to claim 1, characterized in that: In the step of pumping the thallium-containing solution into a primary reactor, adding a first mixed agent, stirring for reaction, filtering, and obtaining a primary thallium removal solution and a primary thallium removal slag, the mass ratio of the first thallium removal agent (JLCT-A) in the first mixed agent to the thallium ions in the thallium-containing solution is 100 to 200:

1.

10. The method for removing thallium from a thallium-containing solution in a lithium extraction process of lepidolite according to claim 1, wherein: In the step of pumping the primary thallium removal liquid into a secondary reactor, adding a second mixed agent, stirring for reaction, standing and filtering to obtain a secondary thallium removal liquid and a secondary thallium removal slag, the mass ratio of the second thallium removal agent (JLCT-B) to the thallium ions in the primary thallium removal liquid is 50 to 100:1.

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