Method for extractng lithium from a lithium-containing solution by sorption

Abstract

The invention relates to a method for extracting lithium from lithium-containing solutions. The method includes at least two cycles, performed consecutively. The first cycle comprises: a) a sorption stage in which a raffinate is removed; b) a sorbent washing stage in which a washing solution is removed; c) a desorption stage in which an eluate is removed. In the second and subsequent cycles, either the sorbent is washed using washing solution drawn from the washing solution removed in stage b) of the preceding cycle, or the sorbent is washed using washing solution drawn from the washing solution removed in stage b) of the preceding cycle and then using raffinate drawn from the first 0.4-1.5 column volumes of the raffinate removed from stage a) of the preceding or current cycle, i.e. the volume of liquid equal to the volume of sorbent involved in the process stage. The invention makes it possible to reduce the amount of water required for washing the sorbent and to reduce the amount of lithium recycled to the sorption stage, as well as to enhance the productivity of the sorption apparatus and increase the amount of lithium extracted with the eluate.

Description

[0001] METHOD FOR SORPTION EXTRACTION OF LITHIUM FROM A LITHIUM-CONTAINING SOLUTION

[0002] Field of technology

[0003] The proposed invention relates to a method for extracting lithium from lithium-containing solutions, including natural brines and waters, process solutions and wastewater from various industries.

[0004] Prior art

[0005] A feature of the processes of sorption extraction in general, and lithium in particular, is the relatively high consumption of water for washing the sorbent from contaminating components that are part of the solution from which the target component is extracted, as well as for the desorption of lithium

[0006] During sorption extraction of lithium, the volume of water used to flush the sorption column can reach 1.5 KO. The resulting wash water, due to its high lithium content, is returned to the sorption process mixed with the process solution. Depending on the sorption and desorption conditions, the amount of lithium recovered is 2-3 grams of lithium per liter of sorbent per cycle. This means that the specific water consumption for flushing is 0.5-0.75 liters of water per gram of lithium.

[0007] The specific water consumption for lithium desorption can reach 2.5 liters per 1 g of recovered lithium, and 95-98% of the consumed water can be recovered through reverse osmosis concentration of the eluate. Thus, the specific water consumption for desorption, taking into account reverse osmosis, can reach 0.13 liters per 1 g of recovered lithium, which is significantly lower than the water consumption for flushing.

[0008] Reducing the wash duration, on the one hand, reduces water consumption and the amount of lithium returned with the wash water for resorption, but leads to a significant increase in the content of impurity elements, which complicates the processing technology of the resulting eluate. In particular, due to the increased contribution of impurities (NaCl, MgCE, CaCh) to the osmotic pressure, the efficiency of reverse osmosis concentration decreases, and the energy consumption for concentration using evaporation units increases. Reagent consumption (including water) also increases, and the equipment required for purifying the lithium concentrate from alkaline earth elements becomes more complex. Therefore, this method of reducing water consumption may be considered controversial and should only be used in the absence of alternatives. Patent RU2816073, published on March 26, is the closest comparable method.2024, which discloses a method for the sorption production of lithium concentrate from a lithium-containing solution, comprising: a sorption step comprising passing the lithium-containing solution through a sorbent to extract lithium, a step of washing said sorbent, and a desorption step. During the washing step of said sorbent, a washing liquid containing a depleted raffinate and / or a depleted eluate is used for washing. The depleted raffinate is a solution collected from the first 0.4-1.5 column volumes of the solution obtained in the sorption step as a result of contact between the lithium-containing brine and said sorbent. The depleted eluate is a solution taken from any of the 4th, 5th, 6th, 7th or 8th column volumes of the solution obtained at the desorption stage as a result of contact of the desorbing solution with the specified sorbent.

[0009] In the method proposed as a prototype, due to the use of depleted raffinate for washing, it is possible to reduce water consumption by 30-40%, however, the amount of lithium returned for repeated sorption remains at the same level, which leads to a decrease in the productivity of the sorption unit.

[0010] Disclosure of invention

[0011] In this application: raffinate is a solution formed in the sorption stage as a result of contact between a lithium-containing solution and a sorbent for lithium extraction; eluate is a solution formed in the desorption stage as a result of contact between a desorbing solution and a sorbent for lithium extraction; depleted raffinate is a solution collected from the first 0.4-1.5 column volumes of the solution obtained in the sorption stage as a result of contact between a lithium-containing brine and the said sorbent. In other words, a lithium-containing solution is fed to the unit (sorption-desorption enrichment module) and comes into contact with the sorbent. The resulting solution leaving the unit is raffinate. From the total volume of raffinate leaving the unit, the very first 0.4-1.5 column volumes are collected and withdrawn as depleted raffinate for subsequent use in the washing liquid.Column volume (VO) is the volume of liquid equal to the volume of the sorbent involved in the process stage / operation; sorption stage (saturation stage) is the stage in which the feed solution from which the target component is extracted, for example, a lithium-containing solution (a salt solution containing lithium chloride as a useful component), is fed into the column. Washing stage is the next stage after the sorption stage. At this stage, a wash solution (a solution used to wash the sorbent) is passed through the sorbent to prepare it for the desorption stage. After the sorption stage, the column, in addition to the saturated sorbent, contains significant quantities of the feed solution, and in addition to the component being extracted, the column contains large quantities of impurity components. During lithium sorption, the column contains a solution of NaCl, MgCl, and CaCh, which are not valuable components and can potentially contaminate the eluate obtained during desorption.To reduce the impurity content of the column and sorbent, the sorbent is washed, typically with water or another solution with a low impurity content. During the first washing stage, the initial solution is "displaced" from the column by water, which fills the free space of the column and the space between the sorbent granules. The resulting solution at the column outlet is similar in composition to the initial solution but slightly diluted. During the second washing stage, impurities are removed from the sorbent granules, resulting in a highly diluted solution.The solutions obtained in the washing stage contain significant amounts of lithium, and to avoid its loss, they are usually sent for resorption in a mixture with the original solution; the desorption stage is the stage in which the absorbed substance is at least partially removed (removed together with the liquid) from the sorbent, producing an eluate - a solution leaving the column with a sufficiently low content of impurities, which is sent to subsequent processing stages.

[0012] The objective and technical result of the present invention is to reduce the water consumption for washing the sorbent and to reduce the amount of lithium returned for repeated sorption, while maintaining the quality of the resulting eluate, which leads to an increase in the productivity of the sorption unit and an increase in the amount of lithium extracted with the eluate.

[0013] In order to solve the stated problem and achieve the technical result, a method for the sorption extraction of lithium from a lithium-containing solution is proposed, comprising at least two cycles carried out sequentially, wherein the cycle contains: a) a sorption stage with removal of raffinate; b) a stage of washing the sorbent with removal of the washing solution; c) a desorption stage with removal of the eluate; characterized in that at stage b) of the second and subsequent cycles, a washing solution is used for washing the sorbent, taken from the washing solution removed from stage b) of the previous cycle after removing the first 1 KO of the washing solution, or at stage b) of the second and subsequent cycles, a washing solution is used for washing the sorbent, taken from the washing solution removed from stage b) of the previous cycle after removing the first 1 KO of the washing solution, and then raffinate is used, taken from the first 0.4-1.5 KO of the raffinate removed from stage a) of the previous or current cycle.

[0014] As will be shown in the examples below, after the first fraction of the wash solution (1 KO (one column volume)) is removed ("displacement"), a fraction is collected that can be used as a wash solution in subsequent cycles. This reduces water consumption for sorbent washing and decreases the amount of lithium returned for repeated sorption, while maintaining the quality of the resulting eluate. This leads to increased productivity of the sorption unit and an increase in the amount of lithium recovered with the eluate. For example, in stage b) of the second cycle, the wash solution collected from the wash solution removed from stage b) of the first cycle after the first 1 KO of wash solution is removed is used to wash the sorbent. And so on.

[0015] Alternatively, after washing the sorbent with the above-mentioned fraction of the washing solution, the sorbent is washed with raffinate selected from the first 0.4-1.5 KO of raffinate withdrawn from stage a) of the previous or current cycle. This also allows for a reduction in water consumption for washing the sorbent and a reduction in the amount of lithium returned for repeated sorption, while maintaining the quality of the resulting eluate, which leads to an increase in the productivity of the sorption unit and an increase in the amount of lithium extracted with the eluate. For example, at stage b) of the second cycle, the sorbent is washed with a washing solution selected from the washing solution withdrawn from stage b) of the first cycle after the first 1 KO of the washing solution is withdrawn, and then the sorbent is washed with raffinate selected from the first 0.4-1.5 KO of raffinate withdrawn from stage a) of the first or second cycle. And so on.

[0016] In a preferred embodiment, at stage b) of the second and subsequent cycles, a washing solution is used for washing the sorbent, taken from the washing solution withdrawn from stage b) of the previous cycle after the first 1 KO of the washing solution is withdrawn, and then water is used, or at stage b) of the second and subsequent cycles, a washing solution is used for washing the sorbent, taken from the washing solution withdrawn from stage b) of the previous cycle after the first 1 KO of the washing solution is withdrawn, then raffinate is used, taken from the first 0.4-1.5 KO of the raffinate withdrawn from stage a) of the previous or current cycle, and then water is used.

[0017] The washing stage can be completed (the amount of washing solution can be brought to the required quantity) using any liquid known from the prior art that is suitable for washing the sorbent; however, the use of water is preferable, since it allows for a reduction in the amount of impurities in the eluate.

[0018] In a preferred embodiment, at stage b) of the second and subsequent cycles, a washing solution is used to wash the sorbent, taken from the first 0.3-0.75 KO of the washing solution removed from stage b) of the previous cycle after removing the first 1 KO of the washing solution.

[0019] The specified narrower ranges of washing solution volumes are preferable and allow for an additional reduction in water consumption for washing the sorbent and a reduction in the amount of lithium returned for repeated sorption, while maintaining the quality of the resulting eluate, which leads to an additional increase in the productivity of the sorption unit and an increase in the amount of lithium extracted with the eluate.

[0020] In a preferred embodiment, at stage b) of the second and subsequent cycles, a washing solution is used to wash the sorbent, taken from the first 0.5 KO of the washing solution removed from stage b) of the previous cycle after removing the first 1 KO of the washing solution.

[0021] The specified narrower ranges of washing solution volumes are preferable and allow for an additional reduction in water consumption for washing the sorbent and a reduction in the amount of lithium returned for repeated sorption, while maintaining the quality of the resulting eluate, which leads to an additional increase in the productivity of the sorption unit and an increase in the amount of lithium extracted with the eluate.

[0022] In a preferred embodiment, at stage b) of the second and subsequent cycles, raffinate selected from the first 0.5 KO of raffinate removed from stage a) of the previous or current cycle is used to wash the sorbent.

[0023] The specified narrower ranges of raffinate volumes are preferable and allow for an additional reduction in water consumption for washing the sorbent and a reduction in the amount of lithium returned for repeated sorption, while maintaining the quality of the resulting eluate, which leads to an additional increase in the productivity of the sorption unit and an increase in the amount of lithium extracted with the eluate.

[0024] The above steps themselves are known in the art and are therefore described in general terms. The present invention consists of implementing such a sequence of actions using known units, which results in an unexpected and unanticipated increase in the efficiency of the lithium production process.

[0025] The above stages can be carried out by means known to a specialist, while the particular variants of implementing the stages indicated below make it possible to achieve the stated technical result in the most effective way.

[0026] Brief description of the drawings

[0027] The drawings are presented for a better understanding of the invention, however, it will be obvious to a person skilled in the art that the disclosed invention is not limited to the embodiment shown in them.

[0028] Fig. 1 schematically shows the directions of liquid flows at different stages.

[0029] Embodiments of the invention. The best embodiment of the invention.

[0030] The described embodiments are provided for illustrative purposes only. Those skilled in the art will readily recognize that other embodiments are possible without changing the essence of the invention.

[0031] The essence of the proposed invention can be demonstrated by the following examples. Example 1.

[0032] The sorption column containing the AXIONIT Li-sorb(3) sorbent was saturated with a lithium-containing solution, the composition of which is given in Table 1.

[0033] After saturation, water was passed through the sorbent to wash the sorption column and desorb lithium.

[0034] The solution from the column outlet was fractionated by 0.5 KO, the compositions of the obtained fractions are given in Table 1.

[0035] To evaluate the efficiency of reverse osmosis concentration, the calculated value of osmotic pressure and partial osmotic pressure of lithium chloride are given for each fraction.

[0036] Table 1. Compositions of the initial solution and fractions obtained during lithium desorption from a saturated sorbent, and average (calculated) compositions of the wash and eluate fractions, with different fractionation of the wash and eluate

[0037] * The volume of liquid used for flushing is given in brackets

[0038] As can be seen from the table above, the first two fractions (d01-d02) contain too many impurities and, due to high osmotic pressure, clearly cannot be used for reverse osmosis concentration.

[0039] The third fraction (d03) of the resulting solution has a significantly lower osmotic pressure and can be concentrated using a reverse osmosis unit with an operating pressure of 40 atm or more. However, the high magnesium and boron content requires increased reagent consumption for purification. For example, precipitating magnesium hydroxide from this fraction requires 8.4 g of NaOH per liter of processed fraction, which corresponds to a specific consumption of 4.5 g of NaOH per gram of recovered lithium.

[0040] Table 1 also shows the average composition of the wash and eluate for a wash volume of 1.5 KO and desorption volume of 3 KO. In addition, Table 1 indicates the relative content of impurities in the eluate (relative to lithium).

[0041] Example 2.

[0042] To test the possibility of using the above-mentioned third fraction (d03) 0.5 KO in washing the sorption column, a series of experiments were carried out in which the described fraction was cut off from the previous washing fractions and the subsequent eluate fraction, and was used in washing in the next cycle (experiment).

[0043] To more clearly distinguish the fractions, the first fraction of the removed wash solution in the volume of 1 KO is further designated as “displacement”, since this fraction mainly represents the displacement solution of the original brine, and the third fraction (d03) is assigned the serial number of the sorption-desorption cycle (wash 1, wash 2, etc.).

[0044] Beginning with Experiment 2 (the second cycle), the washing fraction from the previous cycle and water were used for washing. In the experiments described, the number of fractions collected was reduced to reduce the number of analyzed samples. In this method of sorption extraction of lithium from a lithium-containing solution, five cycles were performed sequentially, each cycle containing: a) a sorption stage with raffinate removal (not shown); b) a sorbent washing stage with removal of the washing solution; c) a desorption stage with removal of the eluate.

[0045] In the 1st cycle (experiment 1), 1 KO of the washing solution was removed from the washing stage (displacement), and then the washing solution was collected (wash 1), which was used in the 2nd cycle (the next one) to wash the sorbent, which was completed in the usual way using water.

[0046] In this case, in the 2nd cycle (experiment 2), 1 KO of the washing solution was removed from the washing stage (displacement), and then the washing solution was collected (wash 2), which was used in the 3rd cycle (the next one) to wash the sorbent, which was completed in the usual way using water.

[0047] In this case, in the 3rd cycle (experiment 3), 1 KO of the washing solution was removed from the washing stage (displacement), and then the washing solution was collected (wash 3), which was used in the 4th cycle (the next one) to wash the sorbent, which was completed in the usual way using water.

[0048] In this case, in the 4th cycle (experiment 4), 1 KO of the washing solution was removed from the washing stage (displacement), and then the washing solution was collected (wash 4), which was used in the 5th cycle (the next one) to wash the sorbent, which was completed in the usual way using water.

[0049] In the 5th cycle (experiment 5), 1 KO of the washing solution was removed from the washing stage (displacement), and then the washing solution was collected (wash 5), which was used in the next cycle to wash the sorbent.

[0050] The volume of the removed wash 1-5 in the examples was 0.5 KO, but it can be more or less than this volume, preferably 0.3-0.75 KO, and is selected according to the process parameters of the column.

[0051] Table 2 below describes the solutions fed during washing and desorption, as well as the volume and composition of the resulting solutions. Additionally, Table 2 shows the relative impurity content in the eluate (relative to lithium).

[0052] Table 2. Compositions of fractions obtained by multiple washing cycles (sorption stage not shown)

[0053] * The volume of liquid used for flushing is given in brackets

[0054] As Table 2 shows, using the designated fraction for the first washing stage results in increased lithium and impurity content in the collected fractions. However, after 4-5 cycles, their composition stabilizes, and by the fifth cycle, compositions close to steady-state conditions are achieved.

[0055] When considering the composition of the resulting eluate as the main and target product, it can be seen that there has been an increase in the lithium content in the eluate and an increase in the relative content of impurities in the eluate.

[0056] The use of the final washing fraction at the first stage of washing instead of water allows for a significant reduction in water consumption, with a slight deterioration in the quality of the eluate relative to the eluate obtained during long-term washing (washing 1.5 KO, example 1), with a decrease in the amount of lithium returned for sorption with the displacement fraction, and an increase in the amount of lithium extracted with the eluate.

[0057] Example 3.

[0058] It differs from example 2 in that at the beginning of the saturation stage, a 0.5 KO fraction of depleted raffinate with a low salt content was separated from the solution leaving the column, which was also used to wash the sorbent after using the reverse washing fraction (supplying the solutions sequentially).

[0059] This example is a continuation of example 2.

[0060] In the 6th cycle (experiment 6), at the washing stage, the sorbent was washed sequentially: with a washing solution (wash 5), collected in the 5th cycle (previous), the first 0.5 KO of raffinate (depleted raffinate 6), removed from the sorption stage of the 6th cycle (current), and water.

[0061] And in the 6th cycle (experiment 6), 1 KO of the washing solution was removed from the washing stage (displacement), and then the washing solution was collected (wash 6), which was used in the 7th cycle (the next one) to wash the sorbent.

[0062] In the 7th cycle (experiment 7), at the washing stage, the sorbent was washed sequentially: with a washing solution (wash 6), collected in the 6th cycle (previous), the first 0.5 KO of the raffinate (depleted raffinate 7), removed from the sorption stage

[0063] 7th (current) cycle, water.

[0064] In this case, in the 7th cycle (experiment 7), 1 KO of the washing solution was removed from the washing stage (displacement), and then the washing solution was collected (wash 7), which was used in the 8th cycle (the next one) to wash the sorbent.

[0065] In the 8th cycle (experiment 8), at the washing stage, the sorbent was washed sequentially: with a washing solution (wash 7), collected in the 7th cycle (previous), the first 0.5 KO of the raffinate (depleted raffinate 8), removed from the sorption stage

[0066] 8th (current) cycle, with water.

[0067] In the 8th cycle (experiment 8), 1 KO of the washing solution was removed from the washing stage (displacement), and then the washing solution was collected (wash 8), which was used in the next cycle to wash the sorbent.

[0068] The volume of the removed wash 6-8 in the examples was 0.5 KO, but it can be more or less than this volume, preferably 0.3-0.75 KO, and is selected according to the process parameters of the column.

[0069] To wash the sorbent, the first 0.4-1.5 KO of the raffinate removed from the sorption stage of the previous or current cycle can be used, preferably the first 0.5 KO.

[0070] The volumes and composition of the obtained fractions are given in Table 3.

[0071] In addition, Table 3 shows the relative content of impurities in the eluate (relative to lithium).

[0072] Table 3. Compositions of fractions obtained from multiple washing cycles and depleted raffinate

[0073] * The volume of liquid used for flushing is given in brackets

[0074] As can be seen from the data presented in Table 3, the composition of the resulting lean raffinate contains insignificant amounts of salts, and its use in column washing has virtually no effect on the composition of the resulting eluate and backwash fractions. Furthermore, the combined (sequential) use of backwash and lean raffinate allows for a reduction in water consumption during washing to 0.5 KO while maintaining a high amount of lithium recovered with the eluate and relatively low amounts of lithium returned for sorption with the displacement fraction.

Claims

Invention formula 1. A method for the sorption extraction of lithium from a lithium-containing solution, comprising at least two cycles carried out sequentially, wherein the cycle comprises: a) a sorption stage with removal of raffinate; b) a sorbent washing stage with removal of the washing solution; c) a desorption stage with removal of the eluate; characterized in that at stage b) of the second and subsequent cycles, a washing solution is used for washing the sorbent, taken from the washing solution removed from stage b) of the previous cycle after removing the first 1 KO of the washing solution, or at stage b) of the second and subsequent cycles, a washing solution is used for washing the sorbent, taken from the washing solution removed from stage b) of the previous cycle after removing the first 1 KO of the washing solution, and then raffinate is used, taken from the first 0.4-1.5 KO of the raffinate removed from stage a) of the previous or current cycle.

2. The method according to claim 1, characterized in that at stage b) of the second and subsequent cycles, a washing solution is used for washing the sorbent, taken from the washing solution withdrawn from stage b) of the previous cycle after the first 1 KO of the washing solution has been withdrawn, and then water is used, or at stage b) of the second and subsequent cycles, a washing solution is used for washing the sorbent, taken from the washing solution withdrawn from stage b) of the previous cycle after the first 1 KO of the washing solution has been withdrawn, then raffinate is used, taken from the first 0.4-1.5 KO of the raffinate withdrawn from stage a) of the previous or current cycle, and then water is used.

3. The method according to item 1 or item 2, characterized in that at stage b) of the second and subsequent cycles, a washing solution is used to wash the sorbent, selected from the first 0.3-0.75 KO of the wash solution, removed from stage b) of the previous cycle after removal of the first 1 KO of the wash solution.

4. The method according to paragraph 1 or paragraph 2, characterized in that at stage b) of the second and subsequent cycles, a washing solution is used to wash the sorbent, taken from the first 0.5 KO of the washing solution removed from stage b) of the previous cycle after removing the first 1 KO of the washing solution.

5. The method according to item 1 or item 2, characterized in that at stage b) of the second and subsequent cycles, raffinate taken from the first 0.5 KO of raffinate removed from stage a) of the previous or current cycle is used to wash the sorbent.

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