A method for recovering lithium from acid clinker

Abstract

The present application discloses a method for recovering lithium from acid clinker, which relates to the technical field of lithium extraction from ores. The method comprises the following steps: adjusting the pH of the acid clinker to 5.9-6.1, performing a leaching reaction, and then pressing to perform solid-liquid separation to obtain a leachate and a leachate residue; removing Fe 2+ Oxidized to Fe 3+ , adding sodium sulfate solution to form yellow sodium iron alum precipitation and filtering to obtain iron removal leachate and sodium iron alum residue; adding potassium sulfate solution to the iron removal leachate for reaction, filtering to obtain potassium aluminum sulfate precipitation and filtrate, adding calcium oxide to the filtrate to form calcium sulfoaluminate precipitation, filtering to obtain aluminum slag and aluminum removal leachate; adding slaked lime to the aluminum removal leachate and adjusting the pH to 7.0-9.0, filtering to remove slag, adding slaked lime and sodium hydroxide, adjusting the pH to 10.0-13.0, filtering to remove slag, and obtaining a lithium-containing filtrate; heating and concentrating the lithium-containing filtrate, adding sodium carbonate solution and filtering to obtain a concentrated solution and a filter cake, cooling the concentrated solution and precipitating salt crystals, and then vacuum filtering to obtain a lithium ion solution.

Description

Technical Field

[0001] The present application relates to the technical field of lithium extraction from ores, and in particular to a method for recovering lithium from acid clinker. Background Art

[0002] In the process of producing lithium hydroxide by spodumene sulfuric acid method, the acid clinker after acidification and roasting contains Li + In addition, there are a lot of metal impurity ions Fe 3+ , Fe 2+ 、Al 3+ Mg 2+ , Mn 2+ , Ca 2+ , K + 、Na + The conventional method of removing impurities is to adjust the pH by adding alkali to form a precipitate, and then remove the residue by filtering. However, since metal ions such as iron, aluminum, magnesium, and manganese react with alkali to form colloidal hydroxides, the colloidal precipitate easily adheres to the surface of the acid clinker, resulting in the inability of the lithium ions in the acid clinker to be fully transferred to the solution, which reduces the recovery rate of lithium. In addition, iron hydroxide and aluminum hydroxide precipitates generally have adsorption properties and are easy to adsorb valuable metal ions, thereby causing the loss of lithium ions. Based on this, the present application proposes a method for recovering lithium from acid clinker to improve the recovery rate of lithium. Summary of the invention

[0003] The main purpose of this application is to provide a method for recovering lithium from acid clinker, aiming to solve the technical problem that the recovery rate of lithium resources in the prior art needs to be improved.

[0004] To achieve the above object, the present application proposes a method for recovering lithium from acid clinker, comprising the following steps:

[0005] The pH of the acid clinker is adjusted to 5.9-6.1, a leaching reaction is carried out, and then a solid-liquid separation is carried out by squeezing to obtain a leaching liquid and a leaching residue;

[0006] The Fe in the leaching solution 2+ Oxidized to Fe 3+ , then adding sodium sulfate solution to form yellow sodium ferroalloy precipitate, filtering to obtain iron removal leaching solution and sodium ferroalloy slag;

[0007] A potassium sulfate solution is added to the de-ironizing leachate to react, and after filtering, potassium aluminum sulfate precipitate and filtrate are obtained, and calcium oxide is added to the filtrate to form calcium sulfoaluminate precipitate, and then filtered to obtain aluminum slag and de-aluminizing leachate;

[0008] Adding slaked lime to the aluminum-removing leachate and adjusting the pH value to 7.0-9.0, filtering and removing the slag, then adding slaked lime and sodium hydroxide and adjusting the pH value to 10.0-13.0, and filtering and removing the slag to obtain a lithium-containing filtrate;

[0009] The lithium-containing filtrate is heated and concentrated, and then a sodium carbonate solution is added and filtered to obtain a concentrated solution and a filter cake. The concentrated solution is cooled and salt crystals are precipitated, and then vacuum filtered to obtain a lithium ion solution.

[0010] Optionally, in the step of performing the leaching reaction, the liquid-to-solid ratio is (4-5):1, the reaction temperature is 80°C-100°C, the reaction time is 1h-2h, and stirring is performed simultaneously at a stirring speed of 300rpm-400rpm.

[0011] Optionally, after the step of obtaining the leaching liquid and the leaching residue by pressing for solid-liquid separation, the step further comprises:

[0012] The leached residue is reversely stirred and washed to obtain a washing liquid, and the washing liquid is subjected to a leaching reaction together with the acid clinker.

[0013] Optionally, the Fe in the leaching solution 2+ Oxidized to Fe 3+ The steps include:

[0014] Hydrogen peroxide is added to the leaching solution, and oxidation is carried out at 18° C.-22° C. for 10 min-12 min. The amount of hydrogen peroxide used is 110%-130% of the total concentration of Fe ions in the leaching solution.

[0015] Optionally, in the step of adding sodium sulfate solution and forming natrolite precipitate, the reaction temperature is 85°C-95°C, the reaction time is 4.0h-4.5h, and the pH is controlled at 2.0-2.2, wherein the amount of sodium sulfate solution used is 130%-140% of the Fe ion concentration in the leachate.

[0016] Optionally, in the step of adding potassium sulfate solution to the deironing leachate for reaction, the reaction temperature is 22°C-25°C, the reaction time is 3.0h-4.0h, and the amount of the potassium sulfate solution is 150%-160% of the Al ion concentration in the deironing leachate.

[0017] Optionally, in the step of adding calcium oxide to the filtrate to form calcium sulfoaluminate precipitate, the amount of calcium oxide is determined according to the following relationship:

[0018] n(CaO)=4.8[c(Al 3+ )×V]

[0019] Among them, c(Al3+ ) is the Al ion concentration in the filtrate, and V is the volume of the filtrate.

[0020] Optionally, in the step of adding slaked lime and sodium hydroxide, adjusting the pH to 10.0-13.0, filtering and removing slag to obtain a lithium-containing filtrate, the reaction temperature is controlled at 90° C.-110° C., and the mass ratio of slaked lime to sodium hydroxide is (1.5-2):1.

[0021] Optionally, the step of heating and concentrating the lithium-containing filtrate comprises:

[0022] The lithium-containing filtrate is evaporated and concentrated by using a triple-effect evaporator, so that the lithium ion concentration in the lithium-containing filtrate reaches 180 g / L-220 g / L.

[0023] Optionally, in the step of adding the sodium carbonate solution and filtering to obtain a concentrated solution and a filter cake, the amount of sodium carbonate used is determined according to the following relationship:

[0024] n(Na2CO3)=c(Ca 2+ )×V

[0025] Among them, c(Ca 2+ ) is the concentration of calcium ions in the lithium-containing filtrate after heating and concentration, and V is the volume of the lithium-containing filtrate after heating and concentration.

[0026] The present application firstly completes the leaching and separation of lithium ions under weakly acidic conditions, so that the lithium ions in the acid clinker are fully transferred to the solution to reduce the lithium content in the leached residue and improve the recovery rate of lithium. The ferrous ions in the leachate are then oxidized to ferric ions to form a stable sodium ferroaluminate precipitate. The sodium ferroaluminate precipitate is easier to settle than the ferric hydroxide colloid and does not have the adsorption effect of the ferric hydroxide colloid. The sodium ferroaluminate slag is then removed by filtration to complete the removal of iron ions without causing lithium loss. The sodium ferroaluminate slag can also be reused in industry as a by-product, thereby realizing the recovery of iron. Potassium sulfate and aluminum ions are then added to form potassium aluminum sulfate precipitate. To preliminarily remove aluminum ions from the leachate, potassium aluminum sulfate precipitate does not have an adsorption effect on lithium ions and will not cause lithium loss. However, due to its weak solubility, potassium aluminum sulfate precipitate cannot completely precipitate the aluminum ions in the leachate. Therefore, this application further removes aluminum ions by adding calcium oxide to form calcium sulfoaluminate precipitate. Excess calcium oxide will continue to react with aluminum hydroxide and calcium sulfate precipitate to form calcium sulfoaluminate. Calcium sulfoaluminate has good crystallinity and does not have the adsorption capacity of amorphous aluminum hydroxide precipitate, so that the lithium element adsorbed by the aluminum hydroxide precipitate re-enters the solution. Therefore, the calcium sulfoaluminate precipitate does not cause lithium loss. In removing Fe 2+ , Fe 3+ 、Al 3+After that, the pH value is adjusted to 7.0-9.0 so that the Mg content in the leaching solution is 2+ Formation of Mg(OH)2 precipitate, thereby Mg 2+ Remove, then continue to add slaked lime and sodium hydroxide, and control the pH to 10.0-13.0, which can make the Mn in the leachate 2+ Mn(OH)2 precipitation is formed, which is then removed by filtration to obtain a lithium-containing filtrate. The lithium-containing filtrate is then heated and concentrated to increase the concentration of lithium ions. During the heating process, a small amount of Ca(OH)2 precipitation is precipitated. Then, sodium carbonate solution is added to react with calcium ions to form calcium carbonate precipitation, thereby removing calcium ions in the leachate and calcium introduced by slaked lime. Finally, sodium and potassium sulfate crystals are precipitated by cooling to remove Na + and K + , and Na2SO4 and K2SO4 can be recycled for Fe 3+ and Al 3+ The impurities can be removed, thereby saving resource costs. After being treated by the method of the present application, a relatively pure lithium ion solution can be recovered, and the recovery rate of lithium ions can be greatly improved. At the same time, other valuable metal ions in the acid clinker can be recovered. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. It is obvious that the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on the structures shown in these drawings without paying any creative work.

[0028] Figure 1 The reaction formula for generating yellow sodium ferroaluminate precipitate described in the examples of the present application;

[0029] Figure 2 The reaction formula for generating potassium aluminum sulfate precipitate described in the examples of the present application;

[0030] Figure 3 This is the reaction formula for generating calcium sulfoaluminate precipitate described in the examples of this application.

[0031] The realization of the purpose, functional features and advantages of this application will be further explained in conjunction with embodiments and with reference to the accompanying drawings. DETAILED DESCRIPTION

[0032] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0033] In view of the technical problems existing in the prior art, an embodiment of the present application provides a method for recovering lithium from acid clinker, comprising the following steps:

[0034] The pH of the acid clinker is adjusted to 5.9-6.1, a leaching reaction is performed, and then a solid-liquid separation is performed by squeezing to obtain a leaching liquid and a leaching residue;

[0035] The Fe in the leaching solution 2+ Oxidized to Fe 3+ , then adding sodium sulfate solution to form yellow sodium ferroalloy precipitate, filtering to obtain iron removal leaching solution and sodium ferroalloy slag;

[0036] A potassium sulfate solution is added to the de-ironizing leachate to react, and after filtering, potassium aluminum sulfate precipitate and filtrate are obtained, and calcium oxide is added to the filtrate to form calcium sulfoaluminate precipitate, and then filtered to obtain aluminum slag and de-aluminizing leachate;

[0037] Adding slaked lime to the aluminum-removing leachate and adjusting the pH value to 7.0-9.0, filtering and removing the slag, then adding slaked lime and sodium hydroxide and adjusting the pH value to 10.0-13.0, and filtering and removing the slag to obtain a lithium-containing filtrate;

[0038] The lithium-containing filtrate is heated and concentrated, and then a sodium carbonate solution is added and filtered to obtain a concentrated solution and a filter cake. The concentrated solution is cooled and salt crystals are precipitated, and then vacuum filtered to obtain a lithium ion solution.

[0039] The present application firstly completes the leaching and separation of lithium ions under weak acid conditions, so that the lithium ions in the acid clinker are fully transferred to the solution to reduce the lithium content in the leached residue and improve the lithium recovery rate, and then oxidizes the ferrous ions in the leachate into ferric ions to form a stable sodium ferroaluminate precipitate. The reaction formula is as follows: Figure 1 As shown, the sodium iron alum precipitate is easier to settle than the iron hydroxide colloid and does not have the adsorption effect of the iron hydroxide colloid. Then, the sodium iron alum slag is removed by filtration to complete the removal of iron ions without causing lithium loss. The sodium iron alum slag can also be reused in industry as a by-product, thereby realizing iron recovery. Then, potassium sulfate is added to form potassium aluminum sulfate precipitate with aluminum ions to preliminarily remove aluminum ions in the leachate. The reaction formula is as follows: Figure 2As shown, potassium aluminum sulfate precipitate has no adsorption effect on lithium ions and will not cause lithium loss. However, due to the weak solubility of potassium aluminum sulfate precipitate, the aluminum ions in the leachate cannot be completely precipitated. Therefore, the present application further removes aluminum ions by adding calcium sulfoaluminate precipitate formed by calcium oxide. The reaction formula is as follows: Figure 3 As shown, the excess calcium oxide will continue to react with aluminum hydroxide and calcium sulfate precipitation to form calcium sulfoaluminate. Calcium sulfoaluminate has good crystallinity and does not have the adsorption capacity of amorphous aluminum hydroxide precipitation, so the lithium element adsorbed by the aluminum hydroxide precipitation re-enters the solution. Therefore, the calcium sulfoaluminate precipitation does not cause lithium loss. 2+ , Fe 3+ 、Al 3+ After that, the pH value is adjusted to 7.0-9.0 so that the Mg content in the leaching solution is 2+ Formation of Mg(OH)2 precipitate, thereby Mg 2+ Remove, then continue to add slaked lime and sodium hydroxide, and control the pH to 10.0-13.0, which can make the Mn in the leachate 2+ Mn(OH)2 precipitation is formed, which is then removed by filtration to obtain a lithium-containing filtrate. The lithium-containing filtrate is then heated and concentrated to increase the concentration of lithium ions. During the heating process, a small amount of Ca(OH)2 precipitation is precipitated. Then, sodium carbonate solution is added to react with calcium ions to form calcium carbonate precipitation, thereby removing calcium ions in the leachate and calcium introduced by slaked lime. Finally, sodium and potassium sulfate crystals are precipitated by cooling to remove Na + and K + , and Na2SO4 and K2SO4 can be recycled for Fe 3+ and Al 3+ The impurities can be removed, thereby saving resource costs. After being treated by the method of the present application, a relatively pure lithium ion solution can be recovered, and the recovery rate of lithium ions can be greatly improved. At the same time, other valuable metal ions in the acid clinker can be recovered.

[0040] As an implementation method of the present application, in the step of performing the leaching reaction, the liquid-solid ratio is (4-5):1, the reaction temperature is 80°C-100°C, the reaction time is 1h-2h, and stirring is performed simultaneously at a stirring speed of 300rpm-400rpm.

[0041] During the leaching process, slaked lime is added for leaching, and the pH is adjusted to 5.9-6.1, so that lithium ions can be fully leached into the solution, thereby improving the recovery rate of lithium ions. Preferably, a higher leaching rate is achieved when the liquid-to-solid ratio is 4.5:1, the reaction temperature is 90°C, and the reaction time is 1.5h. At the same time, stirring can increase the contact between the acid clinker and the slaked lime, which is beneficial to the leaching reaction, thereby improving the leaching rate of lithium ions.

[0042] As an implementation method of the present application, after the step of obtaining the leaching liquid and the leaching residue by pressing for solid-liquid separation, the step further includes:

[0043] The leached residue is reversely stirred and washed to obtain a washing liquid, and the washing liquid is subjected to a leaching reaction together with the acid clinker.

[0044] Since the leaching residue attached liquid contains lithium sulfate, in order to reduce the lithium content attached to the leaching residue, the present application further reduces the lithium sulfate in the leaching residue by leaching again with the washing liquid obtained after reverse stirring and washing the leaching residue, thereby reducing the loss of lithium and improving the recovery rate of lithium.

[0045] As an implementation method of the present application, the Fe in the leachate is 2+ Oxidized to Fe 3+ The steps include:

[0046] Hydrogen peroxide is added to the leaching solution, and oxidation is carried out at 18° C.-22° C. for 10 min-12 min. The amount of hydrogen peroxide used is 110%-130% of the total concentration of Fe ions in the leaching solution.

[0047] In order to form yellow sodium iron alum precipitation, the present application removes ferrous ions and ferric ions in the leachate, firstly oxidizes the ferrous ions into ferric ions by adding hydrogen peroxide, and in order to completely oxidize the ferrous ions, preferably, the oxidation time is 11 minutes, the oxidation temperature is 20°C, and the amount of hydrogen peroxide used is 120% of the total concentration of Fe ions.

[0048] As an implementation method of the present application, in the step of adding sodium sulfate solution and forming yellow sodium ferroaluminate precipitation, the reaction temperature is 85°C-95°C, the reaction time is 4.0h-4.5h, and the pH is controlled at 2.0-2.2, wherein the amount of the sodium sulfate solution is 130%-140% of the Fe ion concentration in the leachate.

[0049] Depend on Figure 1It can be seen from the reaction formula that the amount of acid increases during the precipitation of sodium ferroaluminate. When 1g of iron generates sodium ferroaluminate, about 1.75g ​​of sulfuric acid is released. Although the pH value of sodium ferroaluminate can be 1.7-1.9, sulfuric acid is continuously produced during the generation of alum, which will cause the pH value to continue to decrease. Therefore, in order to meet the pH value of sodium ferroaluminate generation, the acid produced during the generation of sodium ferroaluminate must be neutralized with alkali. If there are not enough alkali metal cations or ammonium ions in the solution, the iron ions may react with hydrogen ions or hydronium ions to generate ferroaluminate. The sedimentation performance of ferroaluminate is not much better than that of ferric hydroxide. Filtration and washing are not ideal, and the residual iron in the solution is still very high. The present application first adds slaked lime, and the leaching solution contains alkali metal cations, which can be neutralized with acid to stabilize the pH value, thereby ensuring the continuity of alum formation and the thoroughness of iron removal. The present application stably controls the pH value at 2.0-2.2.

[0050] As an implementation method of the present application, in the step of adding potassium sulfate solution to the iron removal leachate for reaction, the reaction temperature is 22°C-25°C, the reaction time is 3.0h-4.0h, and the amount of the potassium sulfate solution is 150%-160% of the Al ion concentration in the iron removal leachate.

[0051] Depend on Figure 2 As can be seen from the reaction formula, since the reaction to form potassium aluminum sulfate precipitation is a reversible reaction, in order to promote the reaction to the right, the present application adds excess potassium sulfate to react with Al ions. The amount of potassium sulfate solution used is preferably 155% of the Al ion concentration, which can promote the reaction to the right as much as possible and achieve a higher aluminum removal rate.

[0052] As an implementation method of the present application, in the step of adding calcium oxide to the filtrate to form calcium sulfoaluminate precipitate, the amount of calcium oxide is determined according to the following relationship:

[0053] n(CaO)=4.8[c(Al 3+ )×V]

[0054] Among them, c(Al 3+ ) is the Al ion concentration in the filtrate, and V is the volume of the filtrate.

[0055] Depend on Figure 3It can be seen from the reaction formula that when the amount of CaO is small, an amorphous aluminum hydroxide precipitate with strong adsorption will be generated, and lithium will be adsorbed during the aluminum hydroxide precipitation process, thereby causing lithium loss. However, excess calcium oxide will further react with aluminum hydroxide and calcium sulfate precipitates to generate calcium sulfoaluminate. Calcium sulfoaluminate has good crystallinity and does not have the adsorption performance of amorphous aluminum hydroxide precipitate. The lithium element adsorbed by the aluminum hydroxide precipitate can re-enter the solution. Therefore, the calcium sulfoaluminate precipitate does not cause lithium loss. Therefore, the present application determines the amount of excess CaO according to the Al ion concentration in the filtrate.

[0056] As an implementation method of the present application, in the step of adding slaked lime and sodium hydroxide, adjusting the pH to 10.0-13.0, and then filtering and removing the slag to obtain a lithium-containing filtrate, the reaction temperature is controlled at 90°C-110°C, and the mass ratio of slaked lime to sodium hydroxide is (1.5-2):1.

[0057] When the pH is 10.0-13.0, the Mn in the leaching solution can be 2+ Mn(OH)2 precipitation is formed, and when the reaction temperature is controlled at 90℃-110℃, the reaction can be promoted to the right, thereby increasing the Mn 2+ removal rate.

[0058] As an implementable method of the present application, the step of heating and concentrating the lithium-containing filtrate comprises:

[0059] The lithium-containing filtrate is evaporated and concentrated by using a triple-effect evaporator, so that the lithium ion concentration in the lithium-containing filtrate reaches 180 g / L-220 g / L.

[0060] Since the lithium ion concentration in the lithium-containing filtrate is low and cannot be directly used for the subsequent preparation of lithium hydroxide products, the present application increases the lithium ion concentration to 180g / L-220g / L by evaporating and concentrating the lithium-containing filtrate, and then uses it for the subsequent preparation of lithium products.

[0061] As an implementation method of the present application, in the step of adding the sodium carbonate solution and then filtering to obtain the concentrated solution and the filter cake, the amount of the sodium carbonate is determined according to the following relationship:

[0062] n(Na2CO3)=c(Ca 2+ )×V

[0063] Among them, c(Ca 2+ ) is the concentration of calcium ions in the lithium-containing filtrate after heating and concentration, and V is the volume of the lithium-containing filtrate after heating and concentration.

[0064] The present invention aims to remove calcium ions in the leachate and calcium ions introduced by slaked lime by adding an alkalizing agent, sodium carbonate, to react with Ca2+ Calcium carbonate precipitation is formed, and then Ca 2+ To avoid excessive addition of sodium carbonate, which introduces too much carbonate ions, this application is based on Ca 2+ The concentration of sodium carbonate is used to determine the amount of sodium carbonate used.

[0065] The above technical solution of the present application is described in detail below in conjunction with specific embodiments.

[0066] Example 1

[0067] A method for recovering lithium from acid clinker comprises the following steps:

[0068] The pH of the acid clinker was adjusted to 6.0, the liquid-solid ratio was 4.5:1, and the leaching reaction was carried out at a reaction temperature of 90°C and a reaction time of 1.5 hours. The mixture was stirred at a stirring speed of 350 rpm, and then the solid-liquid separation was carried out by pressing to obtain the leaching liquid and the leaching residue.

[0069] The leached residue is reversely stirred and washed to obtain a washing liquid, and the washing liquid is subjected to a leaching reaction together with the acid clinker;

[0070] Hydrogen peroxide was added to the leaching solution and oxidized at 20°C for 11 min to remove Fe 2+ Oxidized to Fe 3+ , then add sodium sulfate solution, control the reaction temperature to 85°C-95°C, the reaction time to 4.2h, the pH to 2.1, form yellow sodium ferroalloy precipitate, filter, and obtain iron removal leaching solution and sodium ferroalloy slag;

[0071] A potassium sulfate solution is added to the de-ironizing leachate to react at a reaction temperature of 23° C. for a reaction time of 3.5 hours. After filtering, potassium aluminum sulfate precipitate and filtrate are obtained. Excess calcium oxide is added to the filtrate, wherein the molar ratio of Ca to Al is 4.8:1, and calcium sulfoaluminate precipitate is formed. After filtering, aluminum slag and de-aluminizing leachate are obtained.

[0072] Add slaked lime to the aluminum-removing leachate and adjust the pH value to 8.0. After filtering and removing the slag, add slaked lime and sodium hydroxide in a mass ratio of 1.8:1 and adjust the pH value to 12.0. The reaction temperature is controlled at 100° C., and after filtering and removing the slag, a lithium-containing filtrate is obtained.

[0073] The lithium-containing filtrate is evaporated and concentrated by a triple-effect evaporator to make the lithium ion concentration in the lithium-containing filtrate reach 200 g / L, and then a sodium carbonate solution is added and filtered to obtain a concentrated solution and a filter cake. After the concentrated solution is cooled and salt crystals are precipitated, vacuum filtration is performed to obtain a lithium ion solution.

[0074] Example 2

[0075] A method for recovering lithium from acid clinker comprises the following steps:

[0076] The pH of the acid clinker was adjusted to 5.9, the liquid-solid ratio was 4:1, and the leaching reaction was carried out at a reaction temperature of 80°C and a reaction time of 2 hours. The mixture was stirred at a stirring speed of 300 rpm, and then the solid-liquid separation was carried out by pressing to obtain the leaching liquid and the leaching residue.

[0077] The leached residue is reversely stirred and washed to obtain a washing liquid, and the washing liquid is subjected to a leaching reaction together with the acid clinker;

[0078] Hydrogen peroxide was added to the leaching solution and oxidized at 18°C ​​for 12 min to remove Fe 2+ Oxidized to Fe 3+ , then add sodium sulfate solution, control the reaction temperature to 85°C, the reaction time to 4.5h, the pH to 2.0, form yellow sodium ferroalloy precipitate, filter, and obtain iron removal leaching solution and sodium ferroalloy slag;

[0079] A potassium sulfate solution is added to the de-ironizing leachate to react at a reaction temperature of 22° C. for a reaction time of 3.0 h. After filtering, potassium aluminum sulfate precipitate and filtrate are obtained. Excess calcium oxide is added to the filtrate, wherein the molar ratio of Ca to Al is 4.8:1, and calcium sulfoaluminate precipitate is formed. After filtering, aluminum slag and de-aluminizing leachate are obtained.

[0080] Add slaked lime to the aluminum-removing leachate and adjust the pH to 7.0, filter and remove the slag, then add slaked lime and sodium hydroxide in a mass ratio of 1.5:1, adjust the pH to 10.0, control the reaction temperature at 90° C., filter and remove the slag, and obtain a lithium-containing filtrate;

[0081] The lithium-containing filtrate is evaporated and concentrated by a triple-effect evaporator to make the lithium ion concentration in the lithium-containing filtrate reach 180 g / L, and then sodium carbonate solution is added and filtered to obtain a concentrated solution and a filter cake. After the concentrated solution is cooled and salt crystals are precipitated, vacuum filtration is performed to obtain a lithium ion solution.

[0082] Comparative Example 1

[0083] A method for recovering lithium from acid clinker comprises the following steps:

[0084] The pH of the acid clinker was adjusted to 6.0, the liquid-solid ratio was 4.5:1, and the leaching reaction was carried out at a reaction temperature of 90°C and a reaction time of 1.5 hours. The mixture was stirred at a stirring speed of 350 rpm, and then the solid-liquid separation was carried out by pressing to obtain the leaching liquid and the leaching residue.

[0085] The leached residue is reversely stirred and washed to obtain a washing liquid, and the washing liquid is subjected to a leaching reaction together with the acid clinker;

[0086] A potassium sulfate solution is added to the leachate to react at a reaction temperature of 23° C. for a reaction time of 3.5 hours. After filtering, potassium aluminum sulfate precipitate and filtrate are obtained. Excess calcium oxide is added to the filtrate, wherein the molar ratio of Ca to Al is 4.8:1, and calcium sulfoaluminate precipitate is formed. The filtrate is filtered to obtain aluminum slag and aluminum-removed leachate.

[0087] Add slaked lime to the aluminum-removing leachate and adjust the pH to 8.0, filter and remove the slag, then add slaked lime and sodium hydroxide in a mass ratio of 1.8:1, adjust the pH to 11.0, control the reaction temperature at 100° C., filter and remove the slag, and obtain a lithium-containing filtrate;

[0088] The lithium-containing filtrate is evaporated and concentrated by a triple-effect evaporator to make the lithium ion concentration in the lithium-containing filtrate reach 200 g / L, and then a sodium carbonate solution is added and filtered to obtain a concentrated solution and a filter cake. After the concentrated solution is cooled and salt crystals are precipitated, vacuum filtration is performed to obtain a lithium ion solution.

[0089] Comparative Example 2

[0090] A method for recovering lithium from acid clinker comprises the following steps:

[0091] The pH of the acid clinker was adjusted to 6.0, the liquid-solid ratio was 4.5:1, and the leaching reaction was carried out at a reaction temperature of 90°C and a reaction time of 1.5 hours. The mixture was stirred at a stirring speed of 350 rpm, and then the solid-liquid separation was carried out by pressing to obtain the leaching liquid and the leaching residue.

[0092] The leached residue is reversely stirred and washed to obtain a washing liquid, and the washing liquid is subjected to a leaching reaction together with the acid clinker;

[0093] Hydrogen peroxide was added to the leaching solution and oxidized at 20°C for 11 min to remove Fe 2+ Oxidized to Fe 3+ , then add sodium sulfate solution, control the reaction temperature to 90°C, the reaction time to 4.2h, the pH to 2.1, form yellow sodium ferroalloy precipitate, filter, and obtain iron removal leaching solution and sodium ferroalloy slag;

[0094] Add slaked lime to the iron removal leachate and adjust the pH to 8.0, filter and remove the slag, then add slaked lime and sodium hydroxide in a mass ratio of 1.8:1, adjust the pH to 11.0, control the reaction temperature at 100° C., filter and remove the slag, and obtain a lithium-containing filtrate;

[0095] The lithium-containing filtrate is evaporated and concentrated by a triple-effect evaporator to make the lithium ion concentration in the lithium-containing filtrate reach 200 g / L, and then a sodium carbonate solution is added and filtered to obtain a concentrated solution and a filter cake. After the concentrated solution is cooled and salt crystals are precipitated, vacuum filtration is performed to obtain a lithium ion solution.

[0096] Comparative Example 3

[0097] A method for recovering lithium from acid clinker comprises the following steps:

[0098] The pH of the acid clinker was adjusted to 6.0, the liquid-solid ratio was 4.5:1, and the leaching reaction was carried out at a reaction temperature of 90°C and a reaction time of 1.5 hours. The mixture was stirred at a stirring speed of 350 rpm, and then the solid-liquid separation was carried out by pressing to obtain the leaching liquid and the leaching residue.

[0099] The leached residue is reversely stirred and washed to obtain a washing liquid, and the washing liquid is subjected to a leaching reaction together with the acid clinker;

[0100] Add slaked lime to the leachate and adjust the pH to 8.0, filter and remove the slag, then add slaked lime and sodium hydroxide in a mass ratio of 1.8:1, adjust the pH to 11.0, control the reaction temperature at 100° C., filter and remove the slag, and obtain a lithium-containing filtrate;

[0101] The lithium-containing filtrate is evaporated and concentrated by a triple-effect evaporator to make the lithium ion concentration in the lithium-containing filtrate reach 200 g / L, and then a sodium carbonate solution is added and filtered to obtain a concentrated solution and a filter cake. After the concentrated solution is cooled and salt crystals are precipitated, vacuum filtration is performed to obtain a lithium ion solution.

[0102] Experimental example

[0103] The recovery rate of lithium in the acid clinker treated by the methods of the embodiments of the present application and the comparative example and the total lithium content in the leached slag were tested, and the test results are shown in Table 1 below.

[0104] Table 1

[0105]

[0106]

[0107] As can be seen from Table 1, the total lithium content in the leached residue after being treated by the method of the present application can be reduced to 0.23%, indicating that after the leaching reaction, the lithium ions can be fully transferred to the solution, and the lithium recovery rate in the embodiment of the present application can reach more than 95%. In Comparative Example 1, the iron ions are not removed by forming a yellow sodium ferroaluminate precipitate, but the iron ions are directly removed by adding slaked lime and adjusting the pH to 7.0-9.0 to form iron hydroxide and ferrous hydroxide precipitates. Since the iron hydroxide and ferrous hydroxide precipitates have a certain adsorption effect on lithium ions, The lithium recovery rate decreases; in Comparative Example 2, aluminum ions are not removed separately, but the pH is directly adjusted to 7.0-9.0 to form aluminum hydroxide precipitation to remove aluminum ions. Due to the adsorption of lithium ions by aluminum hydroxide colloid, the lithium recovery rate decreases; in Comparative Example 3, iron ions and aluminum ions are not removed separately, but the pH is directly adjusted to form a hydroxide precipitation method to remove iron ions and aluminum ions. Since the hydroxide precipitation will entrain a large amount of solution during sedimentation and filtration, and has an adsorption effect on lithium ions, it causes the loss of lithium resources.

[0108] The above description is only an optional embodiment of the present application, and does not limit the patent scope of the present application. All equivalent structural transformations made by using the contents of the present application specification and drawings under the inventive concept of the present application, or directly / indirectly applied in other related technical fields are included in the patent protection scope of the present application.

Claims

1. A method for recovering lithium from acid clinker, It is characterized in that The following steps are involved: The pH of the acid clinker is adjusted to 5.9-6.1, a leaching reaction is carried out, and then a solid-liquid separation is carried out by squeezing to obtain a leaching liquid and a leaching residue; The Fe in the leaching solution 2+ Oxidized to Fe 3+ , then adding sodium sulfate solution to form yellow sodium ferroalloy precipitate, filtering to obtain iron removal leaching solution and sodium ferroalloy slag; A potassium sulfate solution is added to the de-ironizing leachate to react, and after filtering, potassium aluminum sulfate precipitate and filtrate are obtained, and calcium oxide is added to the filtrate to form calcium sulfoaluminate precipitate, and then filtered to obtain aluminum slag and de-aluminizing leachate; The amount of calcium oxide used is determined according to the following relationship: n(CaO)=4.8[c(Al 3+ )×V] Among them, c(Al 3+ ) is the Al ion concentration in the filtrate, and V is the volume of the filtrate; Adding slaked lime to the aluminum-removing leachate and adjusting the pH value to 7.0-9.0, filtering and removing the slag, then adding slaked lime and sodium hydroxide and adjusting the pH value to 10.0-13.0, and filtering and removing the slag to obtain a lithium-containing filtrate; The lithium-containing filtrate is heated and concentrated, and then a sodium carbonate solution is added and filtered to obtain a concentrated solution and a filter cake, and the concentrated solution is cooled and salt crystals are precipitated, and then vacuum filtered to obtain a lithium ion solution; The amount of sodium carbonate used is determined according to the following relationship: (Na 2 CO 3 )=c(Ca 2+ )×V Among them, c(Ca 2+ ) is the concentration of calcium ions in the lithium-containing filtrate after heating and concentration, and V is the volume of the lithium-containing filtrate after heating and concentration.

2. The method for recovering lithium from acid clinker according to claim 1, It is characterized in that In the step of performing the leaching reaction, the liquid-solid ratio is (4-5):1, the reaction temperature is 80°C-100°C, the reaction time is 1h-2h, and stirring is performed simultaneously at a stirring speed of 300rpm-400rpm.

3. The method for recovering lithium from acid clinker according to claim 1, It is characterized in that After the step of obtaining the leaching solution and the leaching residue by pressing for solid-liquid separation, the process further comprises: The leached residue is reversely stirred and washed to obtain a washing liquid, and the washing liquid is subjected to a leaching reaction together with the acid clinker.

4. The method for recovering lithium from acid clinker according to claim 1, It is characterized in that The Fe in the leaching solution 2+ Oxidized to Fe 3+ The steps include: Hydrogen peroxide is added to the leaching solution, and oxidation is carried out at 18° C.-22° C. for 10 min-12 min. The amount of hydrogen peroxide used is 110%-130% of the total concentration of Fe ions in the leaching solution.

5. The method for recovering lithium from acid clinker according to claim 1, It is characterized in that In the step of adding sodium sulfate solution and forming yellow sodium ferroaluminate precipitation, the reaction temperature is 85°C-95°C, the reaction time is 4.0h-4.5h, and the pH is controlled at 2.0-2.2, wherein the amount of the sodium sulfate solution is 130%-140% of the Fe ion concentration in the leachate.

6. The method for recovering lithium from acid clinker according to claim 1, It is characterized in that In the step of adding potassium sulfate solution to the deironing leachate for reaction, the reaction temperature is 22°C-25°C, the reaction time is 3.0h-4.0h, and the amount of the potassium sulfate solution used is 150%-160% of the Al ion concentration in the deironing leachate.

7. The method for recovering lithium from acid clinker according to claim 1, It is characterized in that In the step of adding slaked lime and sodium hydroxide, adjusting the pH to 10.0-13.0, filtering and removing slag to obtain a lithium-containing filtrate, the reaction temperature is controlled at 90° C.-110° C., and the mass ratio of slaked lime to sodium hydroxide is (1.5-2):

1.

8. The method for recovering lithium from acid clinker according to claim 1, It is characterized in that The step of heating and concentrating the lithium-containing filtrate comprises: The lithium-containing filtrate is evaporated and concentrated by using a triple-effect evaporator, so that the lithium ion concentration in the lithium-containing filtrate reaches 180 g / L-220 g / L.

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