A method for separating and recovering iron from an acid leaching solution of an iron-containing lithium ore

Abstract

The application provides a method for separating and recovering iron from an iron-containing lithium ore acid leaching solution, and relates to the field of hydrometallurgy. The method comprises the following steps: mixing the iron-containing lithium ore acid leaching solution with an oxidizing agent to perform a reaction, and then adding an acidity regulator to adjust the solution acidity to a target value; using an iron selective extractant to perform extraction on the solution to obtain an extraction loaded organic phase and a raffinate, the raffinate is used to prepare lithium carbonate after impurity removal; the extraction loaded organic phase is washed and then subjected to back extraction to obtain a back extraction solution; the back extraction solution is mixed with a neutralizing agent to obtain an iron salt slurry, and an iron salt solution is obtained after solid-liquid separation. The method comprehensively recovers iron in the lithium ore acid leaching solution, does not introduce impurity ions, has low lithium loss rate of the solution, can realize waste utilization, reduces waste residue discharge, and has the advantages of simple process, stable operation, and suitability for industrial scale production.

Description

Technical Field

[0001] The present application relates to the field of hydrometallurgy, and in particular to a method for separating and recovering iron from an acid leachate of an iron-containing lithium ore. Background Art

[0002] Currently, lithium extraction from lithium ore resources primarily involves the sulfuric acid and sulfate methods. The sulfuric acid method, in particular, boasts high adaptability and maturity, suitable for processing most lithium ore resources and achieving high lithium leaching rates. However, during the sulfuric acid method, significant amounts of impurities such as Fe and Al are leached into the solution during lithium ore processing, reaching concentrations of 0.1-20 g / L and 1-50 g / L, respectively.

[0003] The Fe in the sulfuric acid leachate of lithium ore is usually removed as an impurity and not recycled. The neutralization precipitation removal method is mainly used. By adding limestone, lime, alkali or ammonia, the Fe is precipitated into iron hydroxide slag, stored, and not recycled. In addition, due to the strong adsorption of iron hydroxide slag in the conventional precipitation method, the Li loss rate during the precipitation process is 5-10%, which not only affects the lithium recovery rate, but also increases the amount of solid waste discharged, affecting the environment. Summary of the Invention

[0004] The purpose of this application is to provide a method for separating and recovering iron from iron-containing lithium ore acid leaching solution to solve the above problems.

[0005] To achieve the above objectives, this application adopts the following technical solutions:

[0006] A method for separating and recovering iron from an acid leachate of an iron-containing lithium ore, comprising:

[0007] The iron-containing lithium ore acid leaching solution is mixed with an oxidant to react, and then an acidity regulator is added to adjust the acidity of the solution to a target value;

[0008] The solution is extracted with an iron-selective extractant to obtain an extracted organic phase and a raffinate, and the raffinate is used to prepare lithium carbonate after impurities are removed;

[0009] The extracted loaded organic phase is washed and then stripped to obtain a stripped liquid;

[0010] The stripping liquid is mixed with a neutralizing agent to obtain an iron salt slurry, and an iron salt solution is obtained after solid-liquid separation.

[0011] Preferably, the iron-containing lithium ore acid leaching solution has a lithium content of 0.5-25 g / L, a total iron content of 0.5-20 g / L, a divalent iron content of 0.01-3 g / L, an aluminum content of 5-50 g / L, and a pH of 0.1-3.

[0012] Preferably, the method for separating and recovering iron from an acid leachate of an iron-containing lithium ore satisfies one or more of the following conditions:

[0013] (1) The oxidant includes one or more of persulfuric acid, hydrogen peroxide, sodium persulfate, air, oxygen, ozone, a mixture of sulfur dioxide and air, or a mixture of sulfur dioxide and oxygen;

[0014] (2) the amount of the oxidant added is 0.1-10 times the molar amount of the divalent iron in the iron-containing lithium ore acid leaching solution;

[0015] (3) The endpoint redox potential of the reaction is 550-700 mV.

[0016] Preferably, the method for separating and recovering iron from an acid leachate of an iron-containing lithium ore satisfies one or more of the following conditions:

[0017] (1) The acidity regulator includes one or more of sulfuric acid, hydrochloric acid, sodium hydroxide, ammonia, potassium hydroxide, and lithium hydroxide;

[0018] (2) The target value is 0.1-1.5.

[0019] Preferably, the method for separating and recovering iron from an acid leachate of an iron-containing lithium ore satisfies one or more of the following conditions:

[0020] (1) The iron selective extractant includes one or more of di(2-ethylhexyl) phosphate, 2-ethylhexylphosphonic acid mono-2-ethylhexyl ester, monoalkyl phosphoric acid, trioctyl / decylamine, and tributyl phosphate;

[0021] (2) the volume concentration of the iron selective extractant is 1-40%;

[0022] (3) The extraction temperature is 5-50°C, and the extraction flow ratio of organic phase: aqueous phase is (0.1-10):1;

[0023] (4) The extraction adopts multi-stage countercurrent extraction with the number of stages being 2-10;

[0024] (5) adding a diluent during the extraction, wherein the diluent is 260# solvent kerosene;

[0025] (6) The total iron content in the raffinate obtained by the extraction is less than 0.05 g / L.

[0026] Preferably, the method for separating and recovering iron from an acid leachate of an iron-containing lithium ore satisfies one or more of the following conditions:

[0027] (1) The washing is carried out using sulfuric acid and / or hydrochloric acid at a concentration of 0.1-25 g / L;

[0028] (2) The washing is performed by countercurrent washing, with the number of stages being 1-5;

[0029] (3) The flow ratio of the washing organic phase: aqueous phase is (0.5-100):1.

[0030] Preferably, the method for separating and recovering iron from an acid leachate of an iron-containing lithium ore satisfies one or more of the following conditions:

[0031] (1) The stripping agent used in the stripping includes sulfuric acid and / or hydrochloric acid with a concentration of 10-200 g / L;

[0032] (2) The back extraction temperature is 2-50° C., and the extraction flow ratio of organic phase: aqueous phase is (1-100):1;

[0033] (3) The back extraction adopts countercurrent back extraction, and the number of stages is 1-20.

[0034] Preferably, the method for separating and recovering iron from an acid leachate of an iron-containing lithium ore satisfies one or more of the following conditions:

[0035] (1) The neutralizing agent includes one or more of ferric hydroxide, ferric oxide, and basic ferric carbonate;

[0036] (2) The pH of the iron salt slurry is 0.2-2.9.

[0037] Preferably, the method for separating and recovering iron from an acid leachate of an iron-containing lithium ore satisfies one or more of the following conditions:

[0038] (1) The pore size of the filter device used for solid-liquid separation is 1-100 μm, and the material is one or more of polytetrafluoroethylene, polypropylene, and polyester;

[0039] (2) The suspended matter content in the iron salt solution does not exceed 5 g / L.

[0040] Preferably, clean water or a high-concentration iron salt solution is added to the iron salt solution to adjust the iron content in the iron salt solution to 100-250 g / L.

[0041] Compared with the prior art, the advantages of this application include:

[0042] The present application provides a method for separating and recovering iron from an acid leachate of an iron-containing lithium ore. The method uses an extraction method to separate and recover iron ions in the solution. Compared with the traditional precipitation method for removing iron, the discharge of waste iron slag during the lithium extraction process is avoided, and the loss of lithium during the iron separation process is reduced. The traditional method for removing iron and lithium has a loss rate of 5 to 10%, while the extraction method for separating iron has a lithium loss rate of less than 1%. The extraction method is used to separate the iron ions in the solution, and after washing and stripping, an iron salt that meets the chemical industry standards can be prepared. Compared with the traditional method of precipitating iron into waste slag, the waste utilization of iron in the solution can be realized. The method is simple to operate, the process is stable and efficient, and it can be applied to industrial-scale production. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following is a brief introduction to the drawings required for use in the embodiments. It should be understood that the following drawings only show certain embodiments of the present application and therefore should not be regarded as limiting the scope of the present application.

[0044] Figure 1 The present invention provides a process flow diagram of a method for separating and recovering iron from an acid leachate of an iron-containing lithium ore, as provided in an embodiment. DETAILED DESCRIPTION

[0045] In order to better illustrate the technical solution provided by this application, before the embodiments, an overall description of the technical solution is first given, as follows:

[0046] A method for separating and recovering iron from an acid leachate of an iron-containing lithium ore, comprising:

[0047] The iron-containing lithium ore acid leaching solution is mixed with an oxidant to react, and then an acidity regulator is added to adjust the acidity of the solution to a target value;

[0048] The solution is extracted with an iron-selective extractant to obtain an extracted organic phase and a raffinate, and the raffinate is used to prepare lithium carbonate after impurities are removed;

[0049] The extracted loaded organic phase is washed and then stripped to obtain a stripped liquid; the organic extractant is regenerated and recycled;

[0050] The stripping liquid is mixed with a neutralizing agent to obtain an iron salt slurry, and an iron salt solution is obtained after solid-liquid separation.

[0051] In an optional embodiment, the iron-containing lithium ore acid leaching solution has a lithium content of 0.5-25 g / L, a total iron content of 0.5-20 g / L, a divalent iron content of 0.01-3 g / L, an aluminum content of 5-50 g / L, and a pH of 0.1-3.

[0052] Optionally, in the iron-containing lithium ore acid leachate, the lithium content may be 0.5 g / L, 1 g / L, 5 g / L, 10 g / L, 15 g / L, 20 g / L, 25 g / L or any value between 0.5 and 25 g / L; the total iron content may be 0.5 g / L, 1 g / L, 5 g / L, 10 g / L, 15 g / L, 20 g / L or any value between 0.5 and 20 g / L; the divalent iron content may be 0.01 g / L, 0.05 g / L, 0.1 g / L, 0. The content of the present invention can be any value between 5g / L, 1g / L, 1.5g / L, 2g / L, 2.5g / L, 3g / L or any value between 0.01-3g / L, the aluminum content can be 5g / L, 10g / L, 15g / L, 20g / L, 25g / L, 30g / L, 35g / L, 40g / L, 45g / L, 50g / L or any value between 5-50g / L, and the pH can be 0.1, 0.5, 1, 1.5, 2, 2.5, 3 or any value between 0.1-3.

[0053] In an optional embodiment, the method for separating and recovering iron from an iron-containing lithium ore acid leachate satisfies one or more of the following conditions:

[0054] (1) The oxidant includes one or more of persulfuric acid, hydrogen peroxide, sodium persulfate, air, oxygen, ozone, a mixture of sulfur dioxide and air, or a mixture of sulfur dioxide and oxygen;

[0055] By using the above substances as oxidants, a small amount of divalent iron in the oxidizing solution can be oxidized without introducing other impurity ions that affect lithium extraction.

[0056] (2) the amount of the oxidant added is 0.1-10 times the molar amount of the divalent iron in the iron-containing lithium ore acid leaching solution;

[0057] Optionally, the amount of the oxidant added may be 0.1 times, 1 times, 2 times, 3 times, 4 times, 5 times, 6 times, 7 times, 8 times, 9 times, 10 times, or any value between 0.1 and 10 times the molar amount of ferrous iron in the iron-containing lithium ore acid leachate;

[0058] (3) The endpoint redox potential of the reaction is 550-700 mV.

[0059] Optionally, the endpoint redox potential of the reaction may be 550 mV, 600 mV, 650 mV, 700 mV, or any value between 550 and 700 mV.

[0060] The amount of oxidant added and the oxidation endpoint potential are limited to completely oxidize the divalent iron in the solution to trivalent iron. This is because the extractant used selectively extracts only trivalent iron and does not extract divalent iron. If oxidation is not achieved, or if oxidation is incomplete, the divalent iron will not be extracted, and the total iron removal rate in the solution will be reduced, failing to achieve the desired removal.

[0061] In an optional embodiment, the method for separating and recovering iron from an iron-containing lithium ore acid leachate satisfies one or more of the following conditions:

[0062] (1) The acidity regulator includes one or more of sulfuric acid, hydrochloric acid, sodium hydroxide, ammonia, potassium hydroxide, and lithium hydroxide;

[0063] (2) The target value is 0.1-1.5.

[0064] Optionally, the target value may be 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.1, 1.2, 1.3, 1.4, 1.5 or any value between 0.1-1.5.

[0065] Iron extraction is the process of extracting iron under acidic conditions with a low pH value of the solution. If the pH value of the solution is not adjusted to an appropriate value, either too high or too low acidity will be detrimental to the iron extraction rate. The pH value will affect the iron extraction rate.

[0066] In an optional embodiment, the method for separating and recovering iron from an iron-containing lithium ore acid leachate satisfies one or more of the following conditions:

[0067] (1) The iron selective extractant includes one or more of di(2-ethylhexyl) phosphate (P204), 2-ethylhexylphosphonic acid mono-2-ethylhexyl ester (P507), monoalkyl phosphoric acid (P538), trioctyl / decylamine (N235), and tributyl phosphate (TBP);

[0068] (2) the volume concentration of the iron selective extractant is 1-40%;

[0069] Optionally, the volume concentration of the iron-selective extractant may be 1%, 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, or any value between 1% and 40%;

[0070] (3) The extraction temperature is 5-50°C, and the extraction flow ratio of organic phase: aqueous phase is (0.1-10):1;

[0071] Optionally, the extraction temperature may be 5°C, 10°C, 15°C, 20°C, 25°C, 30°C, 35°C, 40°C, 45°C, 50°C or any value between 5-50°C, and the extraction flow ratio of organic phase:aqueous phase may be 0.1:1, 1:1, 2:1, 3:1, 4:1, 5:1, 6:1, 7:1, 8:1, 9:1, 10:1 or any value between (0.1-10):1;

[0072] (4) The extraction adopts multi-stage countercurrent extraction with the number of stages being 2-10;

[0073] Optionally, the number of extraction stages may be 2, 3, 4, 5, 6, 7, 8, 9, 10, or any value between 2 and 10;

[0074] (5) adding a diluent during the extraction, wherein the diluent is 260# solvent kerosene;

[0075] Under certain conditions, solvent extraction can completely remove, separate and recover iron from the solution without forming precipitated residue and will not adsorb lithium to cause lithium loss, which is beneficial to the subsequent separation and recovery of aluminum in the solution.

[0076] (6) The total iron content in the raffinate obtained by the extraction is less than 0.05 g / L.

[0077] In an optional embodiment, the method for separating and recovering iron from an iron-containing lithium ore acid leachate satisfies one or more of the following conditions:

[0078] (1) The washing is carried out using sulfuric acid and / or hydrochloric acid at a concentration of 0.1-25 g / L;

[0079] Optionally, the concentration of the acid used for washing can be 0.1 g / L, 1 g / L, 5 g / L, 10 g / L, 15 g / L, 20 g / L, 25 g / L, or any value between 0.1 and 25 g / L;

[0080] (2) The washing is performed by countercurrent washing, with the number of stages being 1-5;

[0081] Optionally, the number of washing stages may be 1, 2, 3, 4, 5, or any value between 1 and 5;

[0082] (3) The flow ratio of the washing organic phase: aqueous phase is (0.5-100):1.

[0083] During the iron extraction process, the organic phase carries over and extracts a small amount of aluminum and lithium. A dilute acid solution is needed to wash off the aluminum and lithium carried over and extracted by the organic phase. This can reduce the loss of lithium on the one hand, and improve the purity of the iron salt obtained by stripping on the other hand, thereby reducing the impurity content in the iron salt.

[0084] Optionally, the wash flow ratio of organic phase:aqueous phase can be 0.5:1, 1:1, 5:1, 10:1, 20:1, 30:1, 40:1, 50:1, 60:1, 70:1, 80:1, 90:1, 100:1 or any value between (0.5-100):1.

[0085] In an optional embodiment, the method for separating and recovering iron from an iron-containing lithium ore acid leachate satisfies one or more of the following conditions:

[0086] (1) The stripping agent used in the stripping includes sulfuric acid and / or hydrochloric acid with a concentration of 10-200 g / L;

[0087] Optionally, the concentration of the stripping agent used in the back extraction can be 10 g / L, 50 g / L, 100 g / L, 150 g / L, 200 g / L or any value between 10 and 200 g / L;

[0088] (2) The back extraction temperature is 2-50° C., and the extraction flow ratio of organic phase: aqueous phase is (1-100):1;

[0089] Optionally, the back extraction temperature may be 2°C, 5°C, 10°C, 15°C, 20°C, 25°C, 30°C, 35°C, 40°C, 45°C, 50°C or any value between 2-50°C, and the extraction flow ratio organic phase:aqueous phase may be 1:1, 5:1, 10:1, 20:1, 30:1, 40:1, 50:1, 60:1, 70:1, 80:1, 90:1, 100:1 or any value between (1-100):1;

[0090] (3) The back extraction adopts countercurrent back extraction, and the number of stages is 1-20.

[0091] Optionally, the number of back extraction stages can be 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, or any value between 1 and 20;

[0092] The iron in the loaded organic phase is stripped under appropriate conditions to obtain a higher concentration of iron salt solution, and the organic phase is regenerated at the same time, so that the organic phase can be recycled and the operation consumption is reduced.

[0093] In an optional embodiment, the method for separating and recovering iron from an iron-containing lithium ore acid leachate satisfies one or more of the following conditions:

[0094] (1) The neutralizing agent includes one or more of ferric hydroxide, ferric oxide, and basic ferric carbonate;

[0095] (2) The pH of the iron salt slurry is 0.2-2.9.

[0096] Optionally, the pH of the iron salt slurry may be 0.2, 0.5, 1.0, 1.5, 2.0, 2.5, 2.9 or any value between 0.2 and 2.9.

[0097] In an optional embodiment, the method for separating and recovering iron from an iron-containing lithium ore acid leachate satisfies one or more of the following conditions:

[0098] (1) The pore size of the filter device used for solid-liquid separation is 1-100 μm, and the material is one or more of polytetrafluoroethylene (PTFE), polypropylene (PP), and polyester (PET);

[0099] The filtering device is one of a horizontal filter press, a vertical filter press, a vacuum disc filter, a precision filter, a bag filter and / or any combination thereof. The pore size and material referred to here refer to the parameters of the filter cloth in the aforementioned equipment.

[0100] Optionally, the pore size of the filter device used for solid-liquid separation can be 1 μm, 10 μm, 20 μm, 30 μm, 40 μm, 50 μm, 60 μm, 70 μm, 80 μm, 90 μm, 100 μm or any value between 1 and 100 μm;

[0101] (2) The suspended matter content in the iron salt solution does not exceed 5 g / L.

[0102] Because in the process of neutralizing the residual acid in the iron salt solution, the amount of neutralizer added will be excessive, and there will be some insoluble matter, and the suspended matter content will be greater than 5g / L, which exceeds the requirements of the chemical industry standards for suspended matter in iron salt solutions. Therefore, certain filtering devices are used to reduce the suspended matter in the solution to a certain content to meet the product standard requirements.

[0103] In an optional embodiment, clean water or a high-concentration iron salt solution is added to the iron salt solution to adjust the iron content in the iron salt solution to 100-250 g / L.

[0104] After the above series of processes, in order to obtain an iron salt product with stable concentration, the concentration of the iron salt solution is adjusted. If the iron salt content exceeds the standard value too much, it can be diluted with clean water; if the iron salt content in the iron salt solution is lower than the standard value, some high-concentration iron salt solution is added for adjustment, thereby producing a product with stable iron salt concentration.

[0105] The embodiments of the present application will be described in detail below in conjunction with specific examples, but it will be understood by those skilled in the art that the following examples are merely illustrative of the present application and should not be considered as limiting the scope of the present application. In the examples, if specific conditions are not specified, the conditions are carried out according to conventional conditions or manufacturer recommendations. The reagents or instruments used are not specified by the manufacturer and are conventional products that can be purchased commercially.

[0106] Example 1

[0107] like Figure 1 As shown, this embodiment provides a method for separating and recovering iron from an acid leachate of an iron-containing lithium ore, which specifically includes the following steps:

[0108] A clay-type lithium ore calcination-acid leaching solution comprises 1.7 g / L lithium, 3.5 g / L total iron, 0.45 g / L divalent iron, 16.5 g / L aluminum, and a pH value of 2.0. The molar amount of hydrogen peroxide added is 0.6 times the molar amount of divalent iron in the lithium ore acid leaching solution, and the redox potential of the endpoint solution is controlled to be 600 mV, so that the divalent iron in the solution is completely oxidized to trivalent iron. Sulfuric acid is then added to the solution to adjust the pH value of the solution to 1.0. The solution with adjusted acidity is subjected to three-stage countercurrent extraction of iron using an iron-selective extractant containing 30% by volume of trioctyl / decylamine (N235) and tributyl phosphate (TBP) and 70% by volume of diluent 260# solvent kerosene. The extraction temperature is 30°C, and the extraction flow ratio is organic phase / aqueous phase = 1. The lithium loss rate in the solution during the iron extraction process is 0.25%, and the iron extraction rate is 99.8%. The total iron content in the raffinate is 0.007 g / L, and the raffinate is removed by conventional methods to prepare a lithium carbonate product. The extracted loaded organic phase is washed with a 5 g / L sulfuric acid solution in two stages of countercurrent washing, with a washing flow ratio of organic phase to aqueous phase = 5. The loaded organic phase is countercurrently stripped with a 125 g / L sulfuric acid solution in three stages, with a stripping flow ratio of organic phase to aqueous phase = 40, and the stripping temperature is 30°C. Ferric hydroxide is added to the stripped solution obtained by stripping, and the pH value of the solution is adjusted to 2.5 to obtain an iron salt slurry. The iron salt slurry is filtered using a horizontal filter press with a filter cloth having a pore size of 20 microns and a filter cloth made of polypropylene (PP) to remove unreacted suspended matter in the solution, so that the suspended matter content in the filtered filtrate reaches 0.1 g / L. The filtered ferric sulfate filtrate is added with clean water to slightly adjust the iron content of the iron salt solution to 145 g / L, meeting the ferric sulfate requirements of the chemical industry standard HG / T 4816-2015.

[0109] Example 2

[0110] This embodiment provides a method for separating and recovering iron from an acid leachate of an iron-containing lithium ore, which specifically comprises the following steps:

[0111] A calcined, acidified, roasted, and water-leached solution of a spodumene concentrate contains 20.5 g / L lithium, 2.6 g / L total iron, 0.30 g / L divalent iron, 12.8 g / L aluminum, and a pH value of 2.3. Persulfuric acid is added in a molar amount that is 0.7 times the molar amount of divalent iron in the acid leaching solution of the spodumene concentrate, and the redox potential of the endpoint solution is controlled to be 650 mV to completely oxidize the divalent iron in the solution to trivalent iron. Sulfuric acid is then added to the solution to adjust the pH value of the endpoint acidity of the solution to 0.8. The solution with adjusted acidity is subjected to a four-stage countercurrent extraction of iron using an iron-selective extractant containing 25% by volume of di(2-ethylhexyl) phosphate (P204) and tributyl phosphate (TBP) and 75% by volume of diluent 260# solvent kerosene. The extraction temperature is 40°C, and the extraction flow ratio is organic phase / aqueous phase = 0.8. The lithium loss rate in the solution during the iron extraction process is 0.10%, and the iron The extraction rate is 99.85%, and the total iron content in the raffinate is 0.004 g / L. The raffinate is removed by conventional methods to prepare a lithium carbonate product; the extracted loaded organic phase is washed with a 10 g / L hydrochloric acid solution for three-stage countercurrent washing, with a washing flow ratio of organic phase to aqueous phase = 15; the loaded organic phase is countercurrently stripped with a 350 g / L hydrochloric acid solution for five stages, with a stripping flow ratio of organic phase to aqueous phase = 55, and the stripping temperature is 40°C; iron oxide is added to the stripped solution obtained by stripping, and the pH value of the solution is adjusted to 0.5 to obtain an iron salt slurry; the iron salt slurry is filtered using a vertical filter press with a filter cloth with a pore size of 50 microns and a filter cloth made of polyester (PET) to remove unreacted suspended matter in the solution, so that the suspended matter content in the filtered filtrate reaches 1 g / L; the filtered ferric chloride filtrate is added with ferric chloride solid, and the iron content of the iron salt solution is slightly adjusted to 185 g / L, meeting the chemical industry standard GB / T Ferric chloride requirements for 1621-2023.

[0112] Example 3

[0113] This embodiment provides a method for separating and recovering iron from an acid leachate of an iron-containing lithium ore, which specifically comprises the following steps:

[0114] A mixed lithium ore calcination-acid leaching solution is composed of 10g / L lithium, 5.3g / L total iron, 0.65g / L divalent iron, 9g / L aluminum, and a solution pH of 0.5; sulfur dioxide (3% by volume) and air are added to a mixed gas, the molar amount of sulfur dioxide in the mixed gas is 3 times the molar amount of divalent iron in the mixed lithium ore acid leaching solution, and the end point solution redox potential is controlled to 600mV to completely oxidize the divalent iron in the solution to trivalent iron; then, sulfur dioxide (3% by volume) and air are added to the mixed gas, the molar amount of sulfur dioxide in the mixed gas is 3 times the molar amount of divalent iron in the mixed lithium ore acid leaching solution, and the end point solution redox potential is controlled to 600mV to completely oxidize the divalent iron in the solution to trivalent iron; Sodium hydroxide was added to the solution to adjust the pH value of the solution to 1.2; the solution with adjusted acidity was subjected to 5-stage countercurrent extraction of iron using a monoalkyl phosphoric acid (P538) and trioctyl / decylamine (N235) with a volume content of 20% and a diluent 260# solvent kerosene with a volume content of 80%. The extraction temperature was 45°C and the extraction flow ratio was organic phase / aqueous phase = 2; the lithium loss rate in the solution during the iron extraction process was 0.15%, and the iron extraction rate was 99.9 %, the total iron content in the raffinate was 0.005 g / L, and the raffinate was removed by conventional methods to prepare a lithium carbonate product; the extracted loaded organic phase was washed with a 20 g / L hydrochloric acid solution for two-stage countercurrent washing, with a washing flow ratio of organic phase to aqueous phase = 20; the loaded organic phase was countercurrently stripped with a 320 g / L hydrochloric acid solution for five stages, with a stripping flow ratio of organic phase to aqueous phase = 45, and the stripping temperature was 45°C; basic ferric carbonate was added to the stripped solution obtained by stripping, and the pH value of the solution was adjusted to 1.0 to obtain an iron salt slurry; the iron salt slurry was filtered through a bag filter with a filter cloth having a pore size of 125 microns and a filter cloth material of polyester (PET) to remove unreacted suspended matter in the solution, so that the suspended matter content in the filtered filtrate reached 3 g / L; the filtered ferric chloride filtrate was added to clean water, and the iron content of the iron salt solution was slightly adjusted to 185 g / L, meeting the ferric sulfate requirement of the chemical industry standard HG / T4816-2015.

[0115] Comparative Example 1

[0116] A clay-type lithium ore calcination-acid leaching solution is prepared, the composition of which is 1.7 g / L lithium, 3.5 g / L total iron, 0.45 g / L divalent iron, 16.5 g / L aluminum, and the pH value of the solution is 2.0; the molar amount of hydrogen peroxide is 0.3 times the molar amount of divalent iron in the lithium ore acid leaching solution, and the redox potential of the end solution is controlled to be 300 mV, so that the divalent iron in the solution is partially oxidized to trivalent iron; sulfuric acid is then added to the solution to adjust the pH value of the solution to 1.0; the solution with adjusted acidity is treated with trioctyl / decylamine (N2 35) and tributyl phosphate (TBP) volume content is 30%, the volume content of diluent 260# solvent kerosene is 70% by weight, and iron is extracted by three-stage countercurrent extraction. The extraction temperature is 30°C and the extraction flow ratio is organic phase / aqueous phase = 1. The iron extraction rate in the solution is 92.9%, and the total iron content in the raffinate is 0.25 g / L. The purpose of completely separating the iron is not achieved. The raffinate needs to be further removed from the residual iron in the solution during the conventional impurity removal process before the lithium carbonate product can be prepared, which is not conducive to the recovery of aluminum and lithium in the solution.

[0117] Comparative Example 2

[0118] The composition of a clay-type lithium ore calcination-acid leaching solution is 1.7 g / L lithium, 3.5 g / L total iron, 0.45 g / L divalent iron, 16.5 g / L aluminum, and the pH value of the solution is 2.0; the molar amount of hydrogen peroxide added is 0.6 times the molar amount of divalent iron in the lithium ore acid leaching solution, and the end point solution redox potential is controlled to 600 mV to completely oxidize the divalent iron in the solution to trivalent iron; under the condition that the pH value of the solution is 2.0 and the pH value of the solution is not adjusted, the solution after the divalent iron is oxidized is treated with trioctyl / decylamine (N235 ) and tributyl phosphate (TBP) with a volume content of 30%, a diluent 260# solvent kerosene with a volume content of 70%, a three-stage countercurrent extraction of iron, an extraction temperature of 30°C, and an extraction flow ratio of organic phase / aqueous phase = 1; the iron extraction rate in the solution is 65.6%, and the total iron content in the raffinate is 1.20 g / L. The solution does not achieve the purpose of completely separating the iron. The raffinate needs to be further removed from the residual iron in the solution during the conventional impurity removal process before the lithium carbonate product can be prepared, which is not conducive to the recovery of aluminum and lithium in the solution.

[0119] Comparative Example 3

[0120] A clay-type lithium ore calcination-acid leaching solution is composed of 1.7 g / L lithium, 3.5 g / L total iron, 0.45 g / L divalent iron, 16.5 g / L aluminum, and a solution pH of 2.0; the molar amount of hydrogen peroxide added is 0.6 times the molar amount of divalent iron in the lithium ore acid leaching solution, and the endpoint solution redox potential is controlled to 600 mV to completely oxidize the divalent iron in the solution to trivalent iron; sulfuric acid is then added to the solution to adjust the solution endpoint acidity pH to 1.0; the solution with adjusted acidity is treated with trioctyl / decylamine (N235) and tributyl phosphate (TBP) with a volume content of 30%, and a diluent 260# solvent kerosene with a volume content of 70% to obtain an iron-selective The invention relates to a method for producing a lithium carbonate product by using a three-stage countercurrent extraction method with an extraction temperature of 30°C and an extraction flow ratio of organic phase to aqueous phase of 1. The iron extraction rate in the solution is 99.8%, and the total iron content in the raffinate is 0.007 g / L. The lithium carbonate product is prepared after impurities are removed by conventional methods. The extracted loaded organic phase is directly subjected to a three-stage countercurrent stripping with a 125 g / L sulfuric acid solution without washing. The stripping flow ratio is 40 and the stripping temperature is 30°C. Although the stripping method can also produce a ferric sulfate solution, the organic phase carries over a small amount of aluminum and lithium from the solution during the extraction process. The aluminum and lithium contents of the ferric sulfate solution obtained by stripping reach 22 g / L and 0.2 g / L, respectively, which is not suitable for preparing the ferric sulfate product according to the chemical industry standard HG / T 4816-2015. In addition, the total lithium loss rate in this process reaches 1.5%, which is higher than the 0.25% loss rate of the added washing step.

[0121] Comparative Example 4

[0122] A clay-type lithium ore calcination-acid leaching solution is composed of 1.7 g / L lithium, 3.5 g / L total iron, 0.45 g / L divalent iron, 16.5 g / L aluminum, and a solution pH of 2.0; the molar amount of hydrogen peroxide added is 0.6 times the molar amount of divalent iron in the lithium ore acid leaching solution, and the endpoint solution redox potential is controlled to 600 mV to completely oxidize the divalent iron in the solution to trivalent iron; sulfuric acid is then added to the solution to adjust the solution endpoint acidity pH to 1.0; the solution with adjusted acidity is treated with trioctyl / decylamine (N235) and tributyl phosphate (TBP) with a volume content of 30%, and a diluent 260# solvent kerosene with a volume content of 70% to obtain an iron-selective The extraction agent was used for three-stage countercurrent extraction of iron, the extraction temperature was 30°C, and the extraction flow ratio was organic phase / aqueous phase = 1; the lithium loss rate in the solution during the iron extraction process was 0.25%, the iron extraction rate was 99.8%, and the total iron content in the raffinate was 0.007g / L. The lithium carbonate product was prepared after impurities were removed by conventional methods; the extracted loaded organic phase was washed with a 5g / L sulfuric acid solution for two-stage countercurrent washing, and the washing flow ratio was organic phase / aqueous phase = 5; the loaded organic phase was countercurrently stripped with a 125g / L sulfuric acid solution for three stages, the stripping flow ratio was organic phase / aqueous phase = 40, and the stripping temperature was 30°C; the sulfuric acid concentration in the stripped liquid obtained by stripping was 12g / L, exceeding the chemical industry standard HG / T The acid content requirement of ferric sulfate solution in HG / T 4816-2015 was not met, so ferric hydroxide, ferric oxide or basic ferric carbonate was added to adjust the pH of the solution to 2.5 to obtain an iron salt slurry, in which the content of unreacted ferric hydroxide suspended matter was 13 g / L, exceeding the requirement of chemical industry standard HG / T 4816-2015 for the content of water-soluble matter in ferric sulfate solution. Therefore, the unreacted suspended matter in the solution was filtered through a horizontal filter press with a filter cloth with a pore size of 20 microns and made of polypropylene (PP) to reduce the suspended matter content in the filtered filtrate to 0.1 g / L. The filtered ferric sulfate filtrate was added with clean water to slightly adjust the iron content of the iron salt solution to 145 g / L, meeting the ferric sulfate requirement of chemical industry standard HG / T 4816-2015.

[0123] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some or all of the technical features therein. These modifications or replacements do not deviate the essence of the corresponding technical solutions from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A method for separating and recovering iron from an acid leachate of an iron-containing lithium ore, characterized in that: include: The iron-containing lithium ore acid leaching solution is mixed with an oxidant to react, and then an acidity regulator is added to adjust the acidity of the solution to 0.1-1.5; The solution is extracted with an iron-selective extractant to obtain an extracted organic phase and a raffinate, and the raffinate is used to prepare lithium carbonate after impurities are removed. The iron-selective extractant is any one of trioctyl / decylamine and tributyl phosphate, di(2-ethylhexyl) phosphate and tributyl phosphate, monoalkyl phosphoric acid, and trioctyl / decylamine. The extraction temperature is 5-50°C, and the extraction flow ratio of organic phase to aqueous phase is (0.1-10):

1. The extraction adopts multi-stage countercurrent extraction with 2-10 stages. The volume concentration of the iron-selective extractant is 1-40%. A diluent is added during the extraction, and the diluent is 260# solvent kerosene. The total iron content of the raffinate obtained by the extraction is less than 0.05 g / L. The extracted loaded organic phase is washed and then back-extracted to obtain a back-extracted liquid; the washing is performed using sulfuric acid and / or hydrochloric acid at a concentration of 0.1-25 g / L; the washing is performed using countercurrent washing with a stage number of 1-5; the flow ratio of the washing organic phase: aqueous phase is (0.5-100):1; the back-extraction agent used includes sulfuric acid and / or hydrochloric acid with a concentration of 10-200 g / L; the back-extraction temperature is 2-50°C, the extraction flow ratio of the organic phase: aqueous phase is (1-100):1; the back-extraction is performed using countercurrent back-extraction with a stage number of 1-20; The stripping liquid is mixed with a neutralizing agent to obtain an iron salt slurry, and an iron salt solution is obtained after solid-liquid separation; the neutralizing agent includes one or more of iron hydroxide, iron oxide, and basic iron carbonate; the pH of the iron salt slurry is 0.2-2.9; The iron-containing lithium ore acid leaching solution has a lithium content of 0.5-25 g / L, a total iron content of 0.5-20 g / L, a divalent iron content of 0.01-3 g / L, an aluminum content of 5-50 g / L, and a pH of 0.1-3; The oxidant includes one or more of persulfuric acid, hydrogen peroxide, sodium persulfate, air, oxygen, ozone, a mixture of sulfur dioxide and air, or a mixture of sulfur dioxide and oxygen; The amount of the oxidant added is 0.1-10 times the molar amount of divalent iron in the iron-containing lithium ore acid leaching solution; The endpoint redox potential of the reaction is 550-700 mV; The acidity regulator includes one or more of sulfuric acid, hydrochloric acid, sodium hydroxide, ammonia, potassium hydroxide, and lithium hydroxide.

2. The method for separating and recovering iron from an iron-containing lithium ore acid leaching solution according to claim 1, characterized in that: One or more of the following conditions are met: (1) The pore size of the filter device used for solid-liquid separation is 1-100 μm, and the material is one or more of polytetrafluoroethylene, polypropylene, and polyester; (2) The suspended matter content in the iron salt solution does not exceed 5 g / L.

3. The method for separating and recovering iron from an iron-containing lithium ore acid leaching solution according to claim 1 or 2, characterized in that: The iron salt solution is added with clean water or a high-concentration iron salt solution to adjust the iron content in the iron salt solution to 100-250 g / L.

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