Method for recovering lithium from hydrochloric acid desorption solution

Abstract

The present application belongs to the technical field of waste resource recycling, and particularly relates to a method for recovering lithium from waste liquid. The method comprises the following steps: mixing hydrochloric acid desorption liquid and sodium hydroxide to perform a precipitation reaction, reacting the sodium hydroxide with impurities in the hydrochloric acid desorption liquid to generate precipitates insoluble in water, and then performing solid-liquid separation, so as to remove calcium, magnesium, iron and other impurity ions in the waste liquid and obtain an alkali metal solution; then, carbon dioxide is introduced into the alkali metal solution to perform carbonization and pyrolysis, and lithium resources in the solution are chemically transformed into lithium carbonate, so as to recover the lithium resources. The method for recovering lithium from hydrochloric acid desorption liquid provided by the present application effectively extracts lithium resources from hydrochloric acid desorption liquid which needs to be discharged to a sewage treatment station by an enterprise, and converts the lithium resources into lithium carbonate raw materials for producing high-purity industrial product lithium fluoride, thereby effectively reducing the operating cost of the enterprise and enhancing the competitiveness of the enterprise in the lithium fluoride market.

Description

Technical Field

[0001] This invention belongs to the field of waste resource recycling technology, specifically relating to a method for recovering lithium from waste liquid. Background Technology

[0002] Currently, the production of high-purity industrial lithium fluoride from industrial lithium carbonate requires carbonizing industrial lithium carbonate into a lithium bicarbonate solution, followed by using a lithium-type chelating resin to remove impurity ions from the lithium bicarbonate solution, including calcium ions, magnesium ions, and iron ions. The specific production steps are as follows:

[0003] First, the lithium-type chelating resin is regenerated into the hydrogen form using hydrochloric acid solution and washed until neutral. Then, the lithium carbonate mother liquor is transferred to the lithium form and washed until neutral. Finally, lithium bicarbonate is purified using lithium-type chelating resin. The working mechanism of the lithium-type chelating resin is that monovalent lithium ions bound to the functional groups of the lithium-type chelating resin exchange with divalent or higher impurity ions such as calcium, magnesium, and iron in the lithium bicarbonate solution, thereby removing impurity ions. However, due to defects in equipment performance and production process, during the purification process, the lithium-type chelating resin is not saturated with divalent or higher metal ions such as calcium, magnesium, and iron before desorption with hydrochloric acid solution is required. This results in the hydrochloric acid desorption solution containing a large amount of lithium resources, increasing operating costs. Summary of the Invention

[0004] The purpose of this invention is to provide a method for recovering lithium from waste liquid. The method provided by this invention can effectively recover lithium from hydrochloric acid desorption solution.

[0005] To achieve the above objectives, the present invention provides the following technical solution:

[0006] This invention provides a method for recovering lithium from hydrochloric acid desorption solution, comprising the following steps:

[0007] (1) After mixing hydrochloric acid desorption solution and sodium hydroxide to carry out precipitation reaction, solid-liquid separation is performed to obtain alkali metal solution;

[0008] The hydrochloric acid desorption solution includes LiCl and impurities; the impurities include a first impurity and a second impurity.

[0009] The first impurity includes KCl and / or NaCl;

[0010] The general formula for the second impurity is M x Cl y And M x OH y Insoluble in water;

[0011] (2) Carbon dioxide is introduced into the alkali metal solution for carbonation followed by pyrolysis to obtain potassium carbonate and lithium carbonate;

[0012] The amount of carbon dioxide introduced is determined by reducing the pH of the alkali metal solution to 8-9.

[0013] Preferably, the ratio of the total molar number of LiCl and impurities in the hydrochloric acid desorption solution to the molar number of sodium hydroxide is 1:1 to 1.1.

[0014] Preferably, the precipitation reaction is carried out at a temperature of 75–80°C and the holding time is 1–2 hours.

[0015] Preferably, the pyrolysis temperature is 90–95°C, and the holding time is 1–2 hours.

[0016] Preferably, the carbonization temperature is 20-30°C and the holding time is 0.5-1h.

[0017] Preferably, the second impurity includes CaCl2, MgCl2 and FeCl3.

[0018] Preferably, the carbon dioxide introduction rate is 1–1.2 Nm. 3 / h.

[0019] Preferably, the pyrolysis process further includes sequentially filtering and drying the resulting pyrolysis products.

[0020] Preferably, the drying temperature is 120°C and the holding time is 2 hours.

[0021] Preferably, the solid-liquid separation is filtration; the pore size of the filter is 0.2 to 0.5 μm.

[0022] This invention provides a method for recovering lithium from hydrochloric acid desorption solution. The method involves mixing a hydrochloric acid desorption solution containing lithium, potassium, sodium, calcium, magnesium, iron, and other metal ions with sodium hydroxide for a precipitation reaction. The sodium hydroxide reacts with impurities such as calcium chloride, magnesium chloride, and ferric chloride in the hydrochloric acid desorption solution to generate water-insoluble precipitates such as calcium hydroxide, magnesium hydroxide, and ferric hydroxide. Solid-liquid separation is then performed to remove calcium, magnesium, and iron impurity ions from the waste liquid, yielding an alkali metal solution. Subsequently, carbon dioxide is introduced into the alkali metal solution for carbonization followed by pyrolysis, chemically converting the lithium resources in the solution into lithium carbonate, thereby achieving the goal of lithium resource recovery.

[0023] This invention removes impurity ions such as calcium, magnesium, and iron in one step, effectively reducing equipment and labor load. It uses carbon dioxide as a carbon source for chemical transformation, effectively reducing operating costs and equipment load. This invention's fully self-developed chemical recovery method for lithium resources has very broad requirements for the hydrochloric acid desorption solution, requiring no pretreatment of the solution before lithium resource recovery, making it widely applicable.

[0024] The method for recovering lithium from hydrochloric acid desorption solution provided by this invention effectively extracts lithium resources from hydrochloric acid desorption solution that enterprises need to discharge to wastewater treatment plants, and converts it into lithium carbonate raw material for producing high-purity industrial lithium fluoride. This effectively reduces the operating costs of enterprises and enhances their competitiveness in the lithium fluoride market. Example results show that the method provided by this invention can recover more than 80% of the lithium resources. Attached Figure Description

[0025] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0026] Figure 1 The process flow diagram of the method for recovering lithium from hydrochloric acid desorption solution provided by the present invention is shown. Detailed Implementation

[0027] This invention provides a method for recovering lithium from hydrochloric acid desorption solution, comprising the following steps:

[0028] (1) After mixing hydrochloric acid desorption solution and sodium hydroxide to carry out precipitation reaction, solid-liquid separation is performed to obtain alkali metal solution;

[0029] The hydrochloric acid desorption solution includes LiCl and impurities; the impurities include a first impurity and a second impurity.

[0030] The first impurity includes KCl and / or NaCl;

[0031] The general formula for the second impurity is M x Cl y And M x OH y Insoluble in water;

[0032] (2) Carbon dioxide is introduced into the alkali metal solution for carbonation followed by pyrolysis to obtain potassium carbonate and lithium carbonate;

[0033] The amount of carbon dioxide introduced is determined by reducing the pH of the alkali metal solution to 8-9.

[0034] This invention involves mixing hydrochloric acid desorption solution and sodium hydroxide to undergo a precipitation reaction, followed by solid-liquid separation to obtain an alkali metal solution. In this invention, the lithium content of the hydrochloric acid desorption solution is preferably 15–20 g / L, more preferably 20 g / L; the second impurity preferably includes CaCl2, MgCl2, and FeCl3.

[0035] In this invention, the ratio of the total molar number of LiCl and impurities in the hydrochloric acid desorption solution to the molar number of sodium hydroxide is preferably 1:1 to 1.1, more preferably 1:1.05 to 1.1, and even more preferably 1:1.1. In this invention, the hydrochloric acid desorption solution contains impurities such as HCl, LiCl, KCl, NaCl, CaCl2, MgCl2, and FeCl3. Based on the concentrations of H, Li, K, Ca, Mg, and Fe ions in the lithium-containing solution, the mass of the aforementioned impurities is calculated. Then, based on the law of conservation of mass, the theoretical mass of hydroxide ions required is calculated, thereby determining the amount of sodium hydroxide to be used.

[0036] In this invention, the temperature of the precipitation reaction is preferably 75–80°C, more preferably 76–79°C, and even more preferably 77–78°C; the holding time is preferably 1–2 h, more preferably 1.2–1.8 h, and even more preferably 1.4–1.6 h; the apparatus for the precipitation reaction is preferably a precipitation reaction tank. This invention generates precipitates with low solubility products, such as Mg(OH)₂, Fe(OH)₃, and Ca(OH)₂, as well as substances with high solubility, such as KOH and LiOH, through precipitation reactions.

[0037] In this invention, the solid-liquid separation is preferably filtration; the filtration device is preferably a Buchner funnel; the pore size of the filter is preferably 0.2–0.5 μm, more preferably 0.2–0.3 μm. This invention separates precipitates such as Mg(OH)₂, Fe(OH)₃, and Ca(OH)₂ through solid-liquid separation.

[0038] After obtaining the alkali metal solution, the present invention introduces carbon dioxide into the alkali metal solution for carbonation followed by pyrolysis to obtain potassium carbonate and lithium carbonate. In the present invention, the alkali metal solution preferably contains KOH and LiOH; the pH value of the alkali metal solution is preferably 14.

[0039] In this invention, the amount of carbon dioxide introduced is based on reducing the pH value of the alkali metal solution to 8-9, preferably to 8.5; the preferred rate of carbon dioxide introduction is 1-1.2 Nm. 3 / h, more preferably 1.1 to 1.2 Nm 3 / h, further preferably 1.2Nm 3 / h.

[0040] In this invention, the carbonization temperature is preferably 20–30°C, more preferably 25–30°C, and the holding time is preferably 0.5–1 h, more preferably 0.7–0.9 h; the carbonization apparatus is preferably a lithium precipitation reaction tank; the alkali metal solution is preferably added to the lithium precipitation reaction tank from the precipitation reaction tank via a pump. This invention, through carbonization, completely carbonizes KOH and LiOH into KHCO3 and LiHCO3, respectively.

[0041] In this invention, the pyrolysis temperature is preferably 90–95°C, more preferably 91–94°C, and even more preferably 92–93°C. The holding time is preferably 1–2 h, more preferably 1.2–1.8 h, and even more preferably 1.4–1.6 h. The solubility of lithium carbonate decreases with increasing temperature. This invention utilizes the aforementioned reverse solubility property of lithium carbonate to react LiHCO3 into Li2CO3 through pyrolysis, and Li2CO3 precipitates out with increasing temperature.

[0042] In this invention, the pyrolysis process preferably further includes sequential filtration and drying of the resulting pyrolysis products; the filtration device is preferably a Buchner funnel; the pore size of the filter is preferably 0.2–0.5 μm, more preferably 0.2–0.3 μm; the drying temperature is preferably 120°C, and the holding time is preferably 2 hours; the drying device is preferably an oven. This invention separates lithium carbonate and lithium carbonate mother liquor containing potassium carbonate through filtration.

[0043] In this invention, the filtration process preferably further includes discharging the resulting lithium carbonate mother liquor to a wastewater treatment plant for hazardous waste treatment.

[0044] The method for recovering lithium from hydrochloric acid desorption solution provided by this invention has the following specific process flow: Figure 1 As shown in Table 1, this invention involves passing hydrochloric acid desorption solution and sodium hydroxide into a precipitation reaction tank for precipitation, followed by solid-liquid separation to obtain precipitated waste and an alkali metal solution. The alkali metal solution is then added to a lithium precipitation reaction tank, and carbon dioxide is introduced for carbonation. After the reaction is complete, the product is separated into solid and liquid components. The obtained lithium carbonate is dried and packaged for later use. The resulting lithium carbonate mother liquor is sent to a wastewater treatment plant for wastewater treatment. The chemical equations for each reaction in this invention are shown in Table 1.

[0045] Table 1 Chemical equations for each reaction in this invention

[0046]

[0047] The method for recovering lithium from hydrochloric acid desorption solution provided by this invention achieves a recovery rate of 80% for both elemental lithium and lithium carbonate.

[0048] To further illustrate the present invention, the following detailed description of the invention's solutions, in conjunction with the accompanying drawings and embodiments, is provided, but should not be construed as limiting the scope of protection of the present invention.

[0049] Example 1

[0050] (1) First, the mass concentrations of hydrochloric acid, calcium ions, magnesium ions, iron ions, lithium ions and potassium ions in the hydrochloric acid desorption solution were detected. The results showed that the mass concentration of hydrochloric acid was 4%, the calcium ion concentration was 1645 mg / kg, the iron ion concentration was 24.2 mg / kg, the potassium ion concentration was 1108 mg / kg, the magnesium ion concentration was 654.95 mg / kg and the lithium ion concentration was 15.125 g / L.

[0051] Take 4L of hydrochloric acid desorption solution. After calculation, the amount of NaOH required to neutralize hydrochloric acid is 178.516g, the amount of NaOH required to form Ca(OH)2 precipitate from calcium ions is 13.195g, the amount of NaOH required to form Fe(OH)3 precipitate from iron ions is 0.206g, the amount of NaOH required to form Mg(OH)2 precipitate from magnesium ions is 8.509g, the amount of NaOH required to form KOH from potassium ions is 4.573g, and the amount of NaOH required to form LiOH from lithium ions is 345.712g.

[0052] The above hydrochloric acid desorption solution and the calculated 554g sodium hydroxide were added to the precipitation reaction tank in proportion. After stirring and reacting at 75°C for 2 hours, precipitates with small solubility products such as Mg(OH)2, Fe(OH)3 and Ca(OH)2, as well as substances with large solubility such as KOH and LiOH, were generated. Then, the precipitates such as Mg(OH)2, Fe(OH)3 and Ca(OH)2 were separated by filtration through a Buchner funnel. The alkali metal solution containing KOH and LiOH was then pumped into the lithium precipitation reaction tank.

[0053] (2) Carbon dioxide is introduced into the alkali metal solution containing KOH and LiOH in the lithium precipitation reaction tank for carbonization. When the pH value drops from 14 to 8, KOH and LiOH are completely carbonized into KHCO3 and LiHCO3, respectively. Then the above solution is pyrolyzed at 90°C for 2 hours. After the pyrolysis is completed, lithium carbonate is obtained by filtration using a Buchner funnel. Then the lithium carbonate is dried in a 120°C oven for 2 hours to obtain 305g of dried lithium carbonate product. The lithium carbonate mother liquor is discharged to the sewage treatment plant for hazardous waste treatment.

[0054] According to the law of conservation of mass, the theoretical amount of lithium carbonate in this embodiment is calculated to be 376.6g. Therefore, the lithium resource recovery rate of the method provided by the present invention is 80.9%.

[0055] As can be seen from the above embodiments, the method provided by the present invention can effectively recover lithium from hydrochloric acid desorption solution, with a recovery rate of over 80%, which is economical and efficient.

[0056] Although the above embodiments have provided a detailed description of the present invention, they are only some embodiments of the present invention, and not all embodiments. Other embodiments can be obtained based on these embodiments without creative effort, and these embodiments all fall within the protection scope of the present invention.

Claims

1. A method for recovering lithium from hydrochloric acid desorption solution, characterized in that, Includes the following steps: (1) First, the mass concentrations of hydrochloric acid, calcium ions, magnesium ions, iron ions, lithium ions and potassium ions in the hydrochloric acid desorption solution were detected. The results showed that the mass concentration of hydrochloric acid was 4%, the calcium ion concentration was 1645 mg / kg, the iron ion concentration was 24.2 mg / kg, the potassium ion concentration was 1108 mg / kg, the magnesium ion concentration was 654.95 mg / kg and the lithium ion concentration was 15.125 g / L. Take 4L of hydrochloric acid desorption solution. After calculation, the amount of NaOH required to neutralize hydrochloric acid is 178.516g, the amount of NaOH required to form Ca(OH)2 precipitate from calcium ions is 13.195g, the amount of NaOH required to form Fe(OH)3 precipitate from iron ions is 0.206g, the amount of NaOH required to form Mg(OH)2 precipitate from magnesium ions is 8.509g, the amount of NaOH required to form KOH from potassium ions is 4.573g, and the amount of NaOH required to form LiOH from lithium ions is 345.712g. The above hydrochloric acid desorption solution and the calculated 554g sodium hydroxide were added to the precipitation reaction tank in proportion. After stirring and reacting at 75°C for 2 hours, precipitates with small solubility products of Mg(OH)2, Fe(OH)3 and Ca(OH)2, as well as substances with large solubility of KOH and LiOH were generated. Then, the Mg(OH)2, Fe(OH)3 and Ca(OH)2 precipitates were separated by filtration through a Buchner funnel. The alkali metal solution containing KOH and LiOH was then pumped into the lithium precipitation reaction tank. (2) Carbon dioxide is introduced into the alkali metal solution containing KOH and LiOH in the lithium precipitation reaction tank for carbonization. When the pH value drops from 14 to 8, KOH and LiOH are completely carbonized into KHCO3 and LiHCO3, respectively. Then, the above solution is pyrolyzed at 90°C for 2 hours. After the pyrolysis is completed, lithium carbonate is obtained by filtration using a Buchner funnel. Then, the lithium carbonate is dried in a 120°C oven for 2 hours to obtain 305g of dried lithium carbonate product. The lithium carbonate mother liquor is discharged to the sewage treatment plant for hazardous waste treatment.

Images