Method for processing water-soluble mineral lithium-containing raw materials

Abstract

The present invention relates to hydrometallurgy of rare metals, and particularly to the adsorption recovery of lithium from natural brines and wastewaters. The method comprises introducing a feed lithium-containing brine into an adsorption-desorption concentration module in the form of a vertical column filled with an inorganic adsorbent, which is a chlorine-containing lithium aluminum double hydroxide. After adsorption, the lithium-saturated adsorbent is washed with a 27% ammonium chloride solution in the column and in an amount of 80-150% of the adsorbent volume, and flows through the column in a direction opposite to the direction of the feed brine stream. Then, lithium is desorbed from the adsorbent with demineralized water to obtain a lithium-rich solution containing ammonium chloride impurities, which is then evaporated, and then ammonium chloride is sublimated from the dried mixture. The effect of the present invention is to reduce the loss of lithium in the washing solution and to increase the purity of the target product (LiCl concentrate).

Description

Technical Field

[0001] The present invention relates to the field of lithium hydrometallurgy and can be used for recovering lithium from natural brines and water, process solutions, and waste waters of various production facilities. Background Art

[0002] Lithium-containing natural waters and brines are one of the types of raw materials currently used for producing lithium and its compounds. Since the concentration of lithium ions in such raw materials is low compared to the concentrations of alkali metal and alkaline earth metal ions and other related components present in significant amounts, the application of adsorption techniques and the use of adsorbents selective for lithium are advantageous for recovering lithium from brines (see, for example, Ryabtsev A.D., Processing of lithium-bearing poly-component hydromineral feedstock based on its lithium concentration, Abstract of Doctoral Dissertation in Engineering Sciences, Tomsk, 2011).

[0003] For recovering lithium from water-soluble mineral raw materials, lithium aluminum chloride double hydroxide is known as a selective inorganic adsorbent. The effective adsorption of lithium from brines using the above-mentioned adsorbent and the subsequent desorption of lithium to obtain a concentrate are confirmed in various sources of information (see, for example, WO 2019221932, November 21, 2019, US20190256368, August 22, 2019, CN 106140121, November 23, 2016, RU 2659968, July 4, 2018, RU 2720420, July 29, 2020, RU 2713360, February 4, 2020, etc.).

[0004] However, in order to obtain, for example, a high-purity lithium concentrate suitable for the production of lithium batteries, the above methods require additional processing stages, additional reagents, and / or the use of additional equipment, which complicates the process. The production of high-quality lithium batteries is quite sensitive to the boron content in the raw materials. The known adsorption methods for producing Li concentrates from brines do not provide the required degree of boron cleanliness for the resulting products.

[0005] There is a known method for producing lithium compounds from feed chloride brines that provides a relatively low boron concentration in the resulting product, and according to this method, an organic solution of C6-C 16 fatty alcohols in kerosene extracts boron from the feed brine at pH 1-2, then the boron-containing organic phase is separated, magnesium and calcium are removed from the aqueous phase, and lithium carbonate is precipitated (see US5219550, June 15, 2010).

[0006] The disadvantages of this method are the additional extraction stage using organic reagents and the need for significant brine acidification.

[0007] The method closest to the proposed technical solution is the method of processing raw materials, including the recovery of lithium by adsorption from brine, followed by desorption of lithium with water.

[0008] The method according to RU 2688593, which the inventor selected as the prototype, includes feeding lithium-containing brine into a vertically installed column filled with granular inorganic adsorbent, the granular inorganic adsorbent being a lithium-aluminum double hydroxide containing chlorine. Lithium saturation is achieved in the adsorbent, and then lithium desorption is carried out by adding demineralized water to the column in an amount of 90 - 130% of the volume of the adsorbent in the direction opposite to the added lithium-containing brine to obtain a primary lithium concentrate (lithium chloride solution) with magnesium and calcium impurities. Then, the lithium concentrate is purified from the impurities, and after washing, the brine is recycled into the added lithium-containing brine stream for adsorption.

[0009] The disadvantages of this method are that up to 30% of the adsorbed lithium is lost at the stage of washing the lithium-saturated adsorbent with demineralized water, and when the salt concentration decreases, the lost lithium transfers into the washing aqueous solution. These situations require the recycling of lithium and result in a decrease in the adsorbent capacity. In addition, in brines with a significant boron concentration, boron is not completely removed from the adsorbent by water washing but is desorbed together with the lithium-contaminated lithium desorbent. Summary of the Invention

[0010] The object of the present invention is to provide an effective method for processing lithium-containing brine, which allows reducing the volume of recycled lithium in the washing solution, increasing the purity of the lithium concentrate, especially in terms of boron contaminants, and reducing the number of process stages for further processing the obtained eluate (desorbent) into a commercial lithium-containing product.

[0011] This object is solved by the described method for processing lithium-containing aqueous mineral raw materials, which includes:

[0012] Introducing the fed lithium-containing brine into an adsorption-desorption concentration module to obtain a lithium-saturated adsorbent, where the adsorption-desorption concentration module is at least one vertically installed column filled with inorganic granular adsorbent, and the inorganic granular adsorbent is a lithium-aluminum double hydroxide containing chlorine.

[0013] Washing the lithium-saturated adsorbent with a 27% ammonium chloride saturated solution by flowing the solution through the column in a direction opposite to the direction of the fed lithium-containing brine stream and in an amount of 80 - 150% of the volume of the adsorbent present in the column.

[0014] Desorbing lithium from the adsorbent with demineralized water to obtain a lithium-rich solution.

[0015] In one embodiment, the method further includes:

[0016] By directing the solution to a feed lithium-containing brine stream, recycling the solution obtained from the stage of washing the saturated adsorbent in the column with ammonium chloride solution.

[0017] In yet another embodiment, the method further comprises:

[0018] Evaporating the lithium-rich solution containing ammonium chloride impurities obtained from the desorption stage to obtain a dry mixture of lithium and ammonium chloride, and

[0019] Heat-treating the obtained dry mixture of lithium and ammonium chloride at 337 - 338 °C until the sublimation of ammonium chloride is complete.

[0020] The inventors believe that due to the following reasons, the technical effect is achieved through the above combination of inventive features.

[0021] The inventors surprisingly found that alkali metal and alkaline earth metal impurities are displaced from the interparticle spaces of the adsorbent particles, and boron adsorbed from the brine is desorbed, which occurs during the stage of washing the lithium-saturated adsorbent with a saturated ammonium chloride solution, and the saturated ammonium chloride solution is fed to the adsorbent in a direction opposite to the direction of the feed lithium-containing brine stream and in an amount of 80% to 150% of the volume of the adsorbent in the column. Due to the high background chloride concentration in the washing solution, lithium is not desorbed from the adsorbent during washing (as opposed to washing with demineralized water). Without being bound by any specific theory, the inventors believe that due to the following reasons, the adsorption / desorption mechanism is different in the proposed and known methods. Lithium cations are adsorbed and retained together with chloride anions in the interparticle spaces of the adsorbent particles (chlorine-containing double alumina and lithium hydroxide). Due to the formation of partial complexes with hydroxyl groups, boron is adsorbed by the adsorbent together with lithium in the form of boric acid or borate according to the solid organic mechanism.

[0022] In the prototype method, when washing the lithium-saturated adsorbent with demineralized water, the salt background concentration decreases, and lithium chloride begins to transfer from the adsorbent to the solution together with the impurities.

[0023] In the proposed method, when washing the adsorbent with a saturated ammonium chloride solution, the total salt background concentration does not decrease, and lithium is not washed off the adsorbent in the form of lithium chloride, where ammonium cations break the complex of boron with the hydroxyl groups of the adsorbent, which leads to the removal of boron from the lithium-saturated adsorbent.

[0024] Contrary to the desorbent containing alkali metal and alkaline earth metal chloride impurities and boron according to the prototype, using demineralized water to further desorb lithium from the adsorbent pre-washed with ammonium chloride allows the production of a desorbent containing lithium chloride and ammonium chloride impurities. Description of the Drawings

[0025] Figure 1It shows the correlation between the ion concentration in the solution discharged from the column, the total volume of ammonium chloride solution flowing through the column during the washing of the adsorbent, and the volume of demineralized water used for desorbing lithium from the adsorbent. Detailed implementation

[0026] Figure 1 The graphs shown in [reference] demonstrate that the elution curves of boron, alkali metals, and alkaline earth metals do not intersect with the lithium desorption curve, which proves an increase in the purity of the lithium concentrate compared to the prototype method.

[0027] Figure 1 It is also proven that the amount of saturated ammonium chloride solution (80 - 150 vol% of the adsorbent volume) is significant, as this is the range that ensures the separation of the elution curves of impurities and the target component (Li), i.e., an increase in the purity of the target product (lithium concentrate) without lithium loss.

[0028] According to the proposed method, by heat-treating the dry residue obtained after drying the strippant, the ammonium chloride impurity in the strippant can be easily separated from lithium chloride by sublimation. The ammonium chloride vapor can sublimate and return to the process, and almost pure lithium chloride remains in the dry residue.

[0029] The proposed method can be implemented as follows.

[0030] The feed brine solution can be natural brine (such as oilfield brine, geothermal brine, salt lake brine, etc.), process solution, or wastewater from oil production, chemical or chemical metallurgy production facilities, or a combination thereof. The feed brine is introduced into the adsorption-desorption concentration module, which includes a vertical column or column system connected in series under a spinner scheme, and the column is filled with granular adsorbent based on chloride-type aluminum-lithium double hydroxide. In the adsorption-desorption module, lithium is adsorbed from the feed brine using a fixed adsorbent bed by filtering the feed brine in flow or in a part in the upward filtration direction. When the adsorbent in the column is saturated with lithium, the filtration of the lithium-containing brine through the column is suspended, and the flow through the column is switched under a Marry-Go-Round scheme to wash the granular adsorbent layer from the brine in the downward direction with a saturated ammonium chloride solution (27%). Depending on the required degree of impurity washing and the completeness of boron desorption, the volume of the washing solution should be 80% to 150% of the volume of the granular adsorbent used in the adsorption-desorption concentration module. The displaced brine is directed to the feed lithium-containing brine stream, which enters the adsorption-desorption concentration module for processing the next part of the feed lithium-containing chloride brine. Then, lithium desorption is carried out by flowing demineralized water through the adsorption-desorption concentration module in a partially downward direction. The solution produced during the desorption process is a lithium concentrate in the form of lithium chloride, which contains ammonium chloride impurities and almost no alkali metals, alkaline earth metals, sulfate, and boron impurities.

[0031] If a dry product is to be prepared, the lithium concentrate is evaporated to dry salts of lithium chloride and ammonium chloride, and then ammonium chloride is sublimed from the dry mixture at about 337.6 °C. The lithium chloride resulting in the dry residue can be used to obtain commercial lithium-containing products such as lithium carbonate, fluoride, bromide, hydroxide, hydroxide-hydrate, etc. without additional purification.

[0032] Example.

[0033] Feed brine having the following ionic composition, g / l: lithium Li + –0.437; sodium Na + –114.55; potassium K + –9.1; chlorine Cl - –196.0; magnesium Mg 2+ –3.56; calcium Ca 2+ –1.73; boron - 0.312; sulfate (SO4 2- ) - 6.51, is introduced in a bottom-up direction through an adsorption-desorption concentration module which is a vertical column filled with granular adsorbent - aluminum-lithium dihydroxide of the formula LiCl*2.5Al(OH)3 having 50 wt% moisture. The adsorbent volume in the column is 5 L. The adsorbent is saturated by monitoring the lithium concentration equilibrium in the brine upstream and downstream of the column. After the lithium adsorption stage is completed, the adsorbent in the column is washed with a saturated ammonium chloride solution (27%) in a downward direction. Then the lithium desorption stage is carried out by passing demineralized water in a downward direction through the adsorbent column. The eluent is analyzed to determine the concentrations of lithium, sodium, potassium, calcium, magnesium, boron, and sulfate. The analysis results are shown in Figure 1 in.

[0034] When a saturated ammonium chloride solution (27%) passes through the adsorption-desorption concentration module in an amount of 4.0 to 7.5 L, which is 80% to 150% of the adsorbent volume used, most of the impurities calcium (95.4 and 99.4% respectively), magnesium (95.3 and 99.0% respectively), sodium (97.4 and 99.6% respectively), potassium (97.7 and 99.8% respectively), boron (90.4 and 98.7% respectively), sulfate (97.5 and 99.7% respectively) contained in the adsorption-desorption concentration module are eluted.

[0035] According to Figure 1 the figures shown in

[0036] Compared with the prototype, for calcium (up to 99.4%, 98.8% in the prototype), magnesium (up to 99%, 98.5% in the prototype), sodium (up to 99.6%, 55% in the prototype), and boron (which is prone to slowly desorb water from the adsorbent of such contaminated lithium eluate), the elution effect is high. Therefore, compared with the prototype, the proposed purification method allows for better elution of boron impurities (up to 98.7%).

[0037] The washing solution that leaves the adsorption - desorption concentration module in an amount of 80 - 150% is directed to the feed lithium - containing brine stream entering the adsorption - desorption concentration module for processing the next portion of the feed lithium - containing chloride brine. Since ammonium chloride does not cause lithium desorption and does not cause negative consequences such as precipitation of calcium and magnesium salts, its presence in the feed brine does not pose a risk.

[0038] Directing the washing solution received from the adsorbent eluate into the stream of the next feed lithium - containing brine portion in the adsorption - desorption concentration module helps capture the lithium contained in the washing solution after adsorbent washing. The adsorbent is washed at a concentration of 0.136 - 0.166 g / L, which prevents the loss of lithium during its recovery from the lithium - containing chloride brine. The recycled lithium volume is 3.5 - 5.7% of the adsorption amount (7 - 12% according to the prototype), which is at least twice lower than the prototype.

[0039] The column of the adsorption - desorption concentration module is further desorbed with demineralized water, such that lithium chloride is desorbed into the lithium concentrate. After drying, the obtained lithium concentrate is then heat - treated at the ammonium chloride sublimation temperature (337.6 °C), allowing for the single - stage obtaining of lithium chloride with a minimum concentration of 0.01 - 0.06% calcium impurities, 0.09 - 0.38% magnesium impurities, 0.32 - 2.15% sodium impurities, 0.02 - 0.15% potassium impurities, 0.07 - 0.48% boron impurities, and 0.01 - 0.12% sulfate impurities. According to the prototype, the impurity concentration in the lithium concentrate was only 18% for calcium and magnesium impurities, which made it impossible to obtain pure lithium chloride without further purification.

[0040] It should also be noted that ammonium nitrogen, which is part of mineral fertilizers and an important component for plant growth, can sometimes have a positive impact on the environmental conditions and the development of ecosystems in places where lithium recovery technologies are used.

[0041] During the research, the present inventors tested various known adsorbents based on lithium - aluminum double - hydroxide chloride. The research showed that the technical results within the scope of the required combination of features were achieved with all types of such adsorbents.

[0042] As demonstrated herein, the proposed method defined by the combination of features included in the claims provides the claimed technical results and has the following advantages compared with the prototype:

[0043] - The efficiency of lithium recovery from lithium-containing brine is improved due to the reduction of impurities, especially boron, in the desorbent.

[0044] - Prevent the loss of lithium with the flushing water.

[0045] - Increased effective operating capacity of the adsorbent.

[0046] - Eliminate the discharge of acid, alkali solution and additional reagent solution required in the post-treatment of lithium chloride according to the prototype method to remove calcium, magnesium, boron and sodium impurities.

Claims

1. A method for processing a lithium-containing aqueous mineral raw material, the method comprising: introducing a feed lithium-containing brine into an adsorption-desorption concentration module to obtain a lithium-saturated adsorbent, wherein the adsorption-desorption concentration module is at least one vertically installed column filled with an inorganic granular adsorbent, and the inorganic granular adsorbent is a chlorine-containing lithium aluminum double hydroxide; washing the lithium-saturated adsorbent with a solution flowing through the column in a direction opposite to the direction of the feed lithium-containing brine stream; and desorbing lithium from the adsorbent with demineralized water to obtain a lithium-rich solution; wherein the lithium-saturated adsorbent is washed with a 27% ammonium chloride saturated solution introduced into the column and in an amount of 80-150% of the volume of the adsorbent present in the column.

2. The method according to claim 1, wherein, Recycling the solution obtained from the stage of washing the lithium-saturated adsorbent in the column with an ammonium chloride solution by directing it to the feed lithium-containing brine stream.

3. The method according to claim 2, the method further comprising: evaporating the lithium-rich solution containing ammonium chloride impurities obtained from the desorption stage to obtain a dry mixture of lithium and ammonium chloride, and thermally treating the obtained dry mixture of lithium and ammonium chloride at 337-338 °C until the sublimation of ammonium chloride is complete.

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