Method for the intensified leaching of ion-type rare earths

Abstract

The application provides a method for strengthening leaching of ionic rare earth, which is based on regulation of ZETA potential and seepage rate of clay mineral by cation and anion coordination adsorption to improve leaching efficiency of ionic rare earth, and comprises the following steps: providing ionic rare earth ore, citrate solution and non-ammonium inorganic salt solution, wherein the liquid-solid ratio of the citrate solution to the ionic rare earth ore is 0.1-0.5:1, and the liquid-solid ratio of the non-ammonium inorganic salt solution to the ionic rare earth ore is 0.9-0.5:1; using the citrate solution to perform first leaching treatment on the ionic rare earth ore to obtain first leaching solution; using the non-ammonium inorganic salt solution to perform second leaching treatment on the ionic rare earth ore to obtain second leaching solution; performing first post-processing treatment on the first leaching solution to obtain rare earth; and performing second post-processing treatment on the second leaching solution to obtain rare earth. The method for leaching ionic rare earth has the advantage of high leaching rate.

Description

Technical Field

[0001] This invention relates to the field of rare earth resource development and environmental protection technology, and in particular to an enhanced leaching method for ion-type rare earths. Background Technology

[0002] Efficient leaching and green production of ionic rare earth elements have always been key aspects of ionic rare earth resource development. Selecting suitable leaching reagents and determining their required concentration range and leaching steps are fundamental to proposing new leaching processes. Therefore, research on leaching of ionic rare earth elements is extensive, with industrial leaching agents used including early methods like sodium chloride, ammonium sulfate (used for over thirty years), and more recently, magnesium sulfate, calcium chloride, and aluminum sulfate. Each of these leaching agents has its advantages and disadvantages, and the appropriate agent should be selected based on specific requirements and objectives.

[0003] Ionic rare earth elements often coexist with ion-adsorbed aluminum. Their coexistence impacts rare earth leaching and subsequent enrichment processes. To reduce aluminum leaching and simplify subsequent enrichment and recovery methods, methods have been proposed to suppress aluminum leaching by adding reagents. A common approach is to add alkaline reagents with acid-base buffering properties, such as hexamethylenetetramine, organic weak acids, and their salts, which can adjust the leaching pH. These form a buffer system with the hydrogen ions exchanged during leaching. Maintaining a pH above 5 in the leachate significantly reduces the aluminum leaching rate. However, while aluminum leaching is suppressed, rare earth leaching is also inhibited to some extent, thus reducing rare earth leaching efficiency. Therefore, how to suppress aluminum leaching while maintaining or even improving rare earth leaching efficiency is a hot topic in the research and development of new reagents and technologies.

[0004] In related technologies, additives of a certain concentration are typically added to leaching reagent solutions such as ammonium sulfate solution before leaching using the original method. However, due to changes in acidity during the leaching process, the actual leaching effect is difficult to control, and sometimes it may even reduce the leaching efficiency. Moreover, continuously adding additives throughout the leaching process increases costs and interferes with the enrichment and recovery of rare earth elements in the leachate. Among the additives studied extensively are organic acids and their salts, such as synthetic organic acids and their salts derived from biomass conversion. Because organic acids and their salts have different coordination abilities with rare earth elements and aluminum, their effects vary considerably. For example, the increase in rare earth and aluminum leaching rates caused by the coordination of some weakly coordinating organic acid ligands can be offset by the decrease caused by the buffer system composed of organic acid salts on the leaching acidity, resulting in slightly higher or lower leaching rates. Furthermore, this contribution is highly dependent on the acidity and concentration during the leaching process, as well as their dosage ratio, making it difficult to control. Therefore, the industrial application of adding additives to leaching reagent solutions is limited, and its practical application is very limited. Summary of the Invention

[0005] To address the aforementioned deficiencies in existing technologies, this invention provides an enhanced leaching method for ionic rare earth elements, aiming to solve the problem of low leaching rates in existing enhanced leaching methods for ionic rare earth elements.

[0006] The enhanced leaching method for ion-type rare earth elements provided by this invention includes the following steps:

[0007] The solution provides ionic rare earth ore, citrate solution, non-ammonium inorganic salt solution, and a precipitant, wherein the liquid-to-solid ratio of the citrate solution to the ionic rare earth ore is 0.1. The liquid-to-solid ratio of the non-ammonium inorganic salt solution to the ionic rare earth ore is 0.5:1. 0.9:1;

[0008] The ionic rare earth ore was subjected to a first leaching treatment using the citrate solution to obtain a first leachate.

[0009] The ionic rare earth ore that has undergone the first leaching treatment is subjected to a second leaching treatment using the non-ammonium inorganic salt solution to obtain a second leachate.

[0010] The first leachate is subjected to a first post-processing treatment to obtain rare earth elements; and

[0011] The second leachate is subjected to a second post-processing treatment to obtain rare earth elements.

[0012] In at least one embodiment, the concentration of citrate in the citrate solution is in the range of 0.01%. 0.3 mol / L.

[0013] In at least one embodiment, the concentration of the non-ammonium inorganic salt in the non-ammonium inorganic salt solution is in the range of 0.1%. 0.6 mol / L.

[0014] In at least one embodiment, the citrate solution contains at least one sodium salt, potassium salt, and ammonium salt.

[0015] In at least one embodiment, the non-ammonium inorganic salt in the non-ammonium inorganic salt solution is at least one of the following: soluble chloride of an alkali metal, soluble nitrate of an alkali metal, soluble sulfate of an alkali metal, soluble chloride of an alkaline earth metal, soluble nitrate of an alkaline earth metal, soluble sulfate of an alkaline earth metal, soluble chloride of aluminum, soluble nitrate of aluminum, and soluble sulfate of aluminum.

[0016] In at least one embodiment, the first post-processing includes the steps of first extraction, back-extraction, first precipitation treatment, and second extraction of the first leachate, wherein the first precipitation treatment yields a first rare earth hydroxide.

[0017] In at least one embodiment, the second post-processing includes the following steps: subjecting the second leachate to a second precipitation treatment to obtain a second rare earth hydroxide; mixing the first rare earth hydroxide and the second rare earth hydroxide to obtain a mixture; and subjecting the mixture to the second extraction to obtain rare earth.

[0018] In at least one embodiment, the precipitant used in the first precipitation treatment and the second precipitation treatment is at least one of calcium oxide, magnesium oxide, and ammonium bicarbonate.

[0019] In at least one embodiment, after obtaining the second leachate, the enhanced leaching method for ionic rare earth elements further includes the following steps:

[0020] Water is added to the ionic rare earth ore to obtain a third leachate;

[0021] The pH value and pollutant concentration of the third leachate are tested. When the pH value and pollutant concentration of the third leachate meet the discharge requirements, the addition of water to the ion-adsorption rare earth ore is stopped.

[0022] In at least one embodiment, after obtaining the first leachate, before performing a second leaching treatment on the ionic rare earth ore using the non-ammonium inorganic salt solution, the enhanced leaching method for ionic rare earth further includes the following steps:

[0023] A sodium salt solution and / or a potassium salt solution are provided, wherein the liquid-to-solid ratio of the sodium salt solution to the ionic rare earth ore is 0.01. The liquid-to-solid ratio of the potassium salt solution to the ionic rare earth ore is 0.01:1. The liquid-to-solid ratio of the sodium salt solution and potassium salt solution to the ionic rare earth ore is 0.01:1. 0.1:1;

[0024] The ionic rare earth ore is subjected to another leaching treatment using the sodium salt solution and / or potassium salt solution to obtain an intermediate leachate.

[0025] In the technical solution of this invention, the citrate in the citrate solution can strongly coordinate with rare earth elements and aluminum, thus requiring only a small amount (the liquid-to-solid ratio of the citrate solution to the ion-adsorption type rare earth ore is 0.1). A citrate solution of 0.5:1 can significantly increase the concentration of rare earth ions in the first leachate. Specifically, the coordination adsorption of citrate anions can increase the zeta potential of ionic rare earth mineral particles and the thickness of the double-layer film (including a compact layer and a diffusion layer covering the compact layer, wherein the ionic rare earth mineral particles are negatively charged; in this invention, the compact layer is a cation layer formed by the tight adsorption of rare earth ions, aluminum ions, magnesium ions, etc., onto the surface of the ionic rare earth mineral particles, and the diffusion layer is a coordination compound unit formed by the coordination of citrate anions and rare earth ions migrating from the compact layer) on the surface of the ionic rare earth mineral particles, thereby promoting the swelling of the ionic rare earth mineral particles and increasing the leaching rate. However, when the citrate anion coordinates with the rare earth ions on the surface of the ionic rare earth mineral particles, the originally trivalent rare earth ions transform into large-volume coordination compound units with zero or monovalent valence. The high ionic potential advantage of the rare earth ions in the compact layer disappears, forcing them to migrate outwards into the diffusion layer or even the solution. This causes the zeta potential of the ionic rare earth mineral particles to become negative, the water film layer to thicken, and the water permeation rate to decrease, resulting in the water film layer loaded with rare earth ions being unable to separate from the mineral ions. To address this, during the second leaching process, the addition of the non-ammonium inorganic salt can adjust the zeta potential of the ionic rare earth mineral particles back to the normal range. The ionic rare earth mineral particles shrink and aggregate, the water film layer thins, promoting solid-liquid separation and allowing the leachate to completely overflow from the ionic rare earth mineral, thereby improving the recovery rate and rare earth leaching rate. Testing showed that the rare earth concentration peak of the leachate from this invention was significantly enhanced, shifted forward, and narrowed. Therefore, the enhanced leaching method for ionic rare earths of the present invention not only has the advantage of high leaching rate, but also the advantages of low leaching agent dosage and high tailings stability. Attached Figure Description

[0026] To more clearly illustrate the solutions of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0027] Figure 1 This is a flowchart of the leaching method for ion-type rare earth ores according to an embodiment of the present invention.

[0028] Figure 2 The figures show the relationship between the concentration of the mixed solution and the leaching rate when using a mixed solution of sodium citrate and calcium chloride as the leaching solution for drip leaching according to an embodiment of the present invention, and the relationship between the concentration of calcium chloride and the leaching rate when using sodium citrate and calcium chloride as the leaching solution for staged drip leaching.

[0029] Figure 3 This is a graph showing the relationship between the types of organic acid salts and the leaching rate in an embodiment of the present invention.

[0030] Figure 4 This is a graph showing the relationship between the concentration of sodium citrate solution and the leaching rate in an embodiment of the present invention.

[0031] Figure 5 This is a graph showing the relationship between the amount of sodium citrate solution used and the leaching rate in an embodiment of the present invention.

[0032] Figure 6 This is a graph showing the relationship between the concentration of calcium chloride solution and the leaching rate in an embodiment of the present invention.

[0033] Figure 7 This is a graph showing the relationship between the concentration of the sulfate solution and the leaching rate when using multiple sulfates as the second-stage leaching agents in an embodiment of the present invention.

[0034] Figure 8 This is a graph showing the relationship between the number of water washing cycles and zeta potential of the tailings after sulfate leaching in an embodiment of the present invention.

[0035] Figure 9 This is a graph showing the relationship between the number of water washing cycles and pH value of the tailings after sulfate leaching in an embodiment of the present invention.

[0036] Figure 10 This is a graph showing the relationship between the number of water washing cycles and electrical conductivity of the tailings after sulfate leaching, according to an embodiment of the present invention.

[0037] Figure 11 This is a graph showing the relationship between the concentration of the chloride solution and the leaching rate when using multiple chloride salts as the second-stage leaching agents in an embodiment of the present invention.

[0038] Figure 12 This is a graph showing the relationship between the number of water washing cycles and zeta potential of the tailings after chloride leaching in an embodiment of the present invention.

[0039] Figure 13 This is a graph showing the relationship between the number of water washing cycles and pH value of tailings after chloride leaching in an embodiment of the present invention.

[0040] Figure 14 This is a graph showing the relationship between the number of water washing cycles and electrical conductivity of tailings after chloride leaching, according to an embodiment of the present invention.

[0041] The realization of the objective, functional features and advantages of the present invention will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0042] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0043] In this invention, the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined with "first" or "second" may explicitly or implicitly include at least one of that feature. Furthermore, the technical solutions of the various embodiments can be combined with each other, but only on the basis of being achievable by those skilled in the art. If the combination of technical solutions is contradictory or impossible to implement, such a combination of technical solutions should be considered non-existent and not within the scope of protection claimed by this invention.

[0044] Please see Figure 1 This invention provides an enhanced leaching method for ionic rare earth elements, which improves the leaching efficiency of ionic rare earth elements by regulating the ZETA potential and percolation rate of clay minerals through anion-cation coordination adsorption. The method includes the following steps:

[0045] Step S1: Provide ionic rare earth ore, citrate solution, non-ammonium inorganic salt solution, and precipitant, wherein the liquid-to-solid ratio of the citrate solution to the ionic rare earth ore is 0.1. The liquid-to-solid ratio of the non-ammonium inorganic salt solution to the ionic rare earth ore is 0.5:1. 0.9:1;

[0046] Step S2: The ionic rare earth ore is subjected to a first leaching treatment using the citrate solution to obtain a first leachate;

[0047] Step S3: The ionic rare earth ore is subjected to a second leaching treatment using the non-ammonium inorganic salt solution to obtain a second leachate;

[0048] Step S4: Perform a first post-processing treatment on the first leachate to obtain rare earth elements; and

[0049] Step S5: Perform a second post-processing on the second leachate to obtain rare earth elements.

[0050] In at least one embodiment, the ion-adsorption rare earth ore may be screened.

[0051] In at least one embodiment, the citrate solution can be continuously dripped onto the upper layer of the ionic rare earth ore with a mesh size of less than 800 mesh for a first leaching treatment; the non-ammonium inorganic salt solution can be continuously dripped onto the upper layer of the ionic rare earth ore for a second leaching treatment.

[0052] In at least another embodiment, the ion-adsorption rare earth ore can be placed in a sand-core glass column, with filter paper placed at both the top and bottom of the sand-core glass column to ensure more uniform seepage. A citrate solution can be added to the sand-core glass column to leach the ion-adsorption rare earth ore smaller than 20 mesh for a first leaching treatment; subsequently, a non-ammonium inorganic salt solution is added to the sand-core glass column to leach the ion-adsorption rare earth ore again for a second leaching treatment.

[0053] Understandably, the volume of the first leachate is comparable to the volume of the citrate solution. The volume of the second leachate is comparable to the volume of the non-ammonium inorganic salt solution.

[0054] In at least one embodiment, the concentration of citrate in the citrate solution is in the range of 0.01%. 0.3 mol / L. For example, in the citrate solution, the concentration range of citrate is 0.01 mol / L, 0.02 mol / L, 0.04 mol / L, 0.06 mol / L, 0.08 mol / L, 0.1 mol / L, 0.12 mol / L, 0.14 mol / L, 0.16 mol / L, 0.18 mol / L, 0.2 mol / L, 0.22 mol / L, 0.24 mol / L, 0.26 mol / L, 0.28 mol / L, or 0.3 mol / L.

[0055] In at least one embodiment, the concentration of the non-ammonium inorganic salt in the non-ammonium inorganic salt solution is in the range of 0.1%. 0.6 mol / L. For example, in the non-ammonium inorganic salt solution, the concentration range of the non-ammonium inorganic salt is 0.1 mol / L, 0.2 mol / L, 0.3 mol / L, 0.4 mol / L, 0.5 mol / L, or 0.6 mol / L.

[0056] Understandably, the concentration of citrate, the concentration of non-ammonium inorganic salt, the amount of citrate, and the amount of non-ammonium inorganic salt need to be adjusted according to the water content of the ore body, converted to dry ore, and the concentration range of citrate is 0.01. The concentration of the non-ammonium inorganic salt is 0.3 mol / L, and the concentration range is 0.1 mol / L. 0.6 mol / L. As the water content increases, the concentration of sodium citrate and non-ammonium inorganic salts should be increased, while the liquid-to-solid ratio should be decreased, while keeping the volume or weight ratio of dry ore basically unchanged.

[0057] Understandably, when leaching the ion-adsorbed rare earth, the leaching operation is carried out at a total liquid-to-solid ratio of 1:1. That is, the ratio of the volume of the citrate solution and the non-ammonium inorganic salt solution to the mass of the ion-adsorbed rare earth ore is 1:1. Obviously, the amount of leaching solution used in this invention is less than that used in related technologies.

[0058] In at least one embodiment, the citrate in the citrate solution is at least one sodium, potassium, or ammonium salt. The citrate is preferably an alkali metal citrate, such as sodium citrate or potassium citrate. The ammonium salt may be ammonium citrate.

[0059] In at least one embodiment, the non-ammonia inorganic salt in the non-ammonia inorganic salt solution is at least one of the following: soluble chlorides of alkali metals, soluble nitrates of alkali metals, soluble sulfates of alkali metals, soluble chlorides of alkaline earth metals, soluble nitrates of alkaline earth metals, soluble sulfates of alkaline earth metals, soluble chlorides of aluminum, soluble nitrates of aluminum, and soluble sulfates of aluminum. Specifically, it may be at least one of the following: lithium chloride, sodium chloride, potassium chloride, rubidium chloride, cesium chloride, francium chloride, lithium nitrate, sodium nitrate, potassium nitrate, rubidium nitrate, cesium nitrate, francium nitrate, lithium sulfate, sodium sulfate, potassium sulfate, rubidium sulfate, cesium sulfate, francium sulfate, beryllium chloride, magnesium chloride, calcium chloride, strontium chloride, barium chloride, radium chloride, beryllium nitrate, magnesium nitrate, calcium nitrate, strontium nitrate, barium nitrate, radium nitrate, beryllium sulfate, magnesium sulfate, aluminum chloride, aluminum nitrate, and aluminum sulfate.

[0060] In at least one embodiment, the first post-processing includes the steps of first extraction, back-extraction, first precipitation treatment, and second extraction of the first leachate, wherein the first precipitation treatment yields a first rare earth hydroxide.

[0061] In at least one embodiment, the second post-processing includes the following steps: subjecting the second leachate to a second precipitation treatment to obtain a second rare earth hydroxide; mixing the first rare earth hydroxide and the second rare earth hydroxide to obtain a mixture; and subjecting the mixture to the second extraction to obtain rare earth.

[0062] It is understood that the extraction, back-extraction, and precipitation processes are common techniques in the field, and will not be elaborated upon here.

[0063] In at least one embodiment, the precipitant used in the first precipitation treatment and the second precipitation treatment is at least one of calcium oxide, magnesium oxide, and ammonium bicarbonate.

[0064] In the technical solution of this invention, the citrate in the citrate solution can strongly coordinate with rare earth elements and aluminum, thus requiring only a small amount (the liquid-to-solid ratio of the citrate solution to the ion-adsorption type rare earth ore is 0.1). A citrate solution of 0.5:1 can significantly increase the concentration of rare earth ions in the first leachate. Specifically, the coordination adsorption of citrate anions can increase the zeta potential of ionic rare earth mineral particles and the thickness of the double-layer film (including a compact layer and a diffusion layer covering the compact layer, wherein the ionic rare earth mineral particles are negatively charged; in this invention, the compact layer is a cation layer formed by the tight adsorption of rare earth ions, aluminum ions, magnesium ions, etc., onto the surface of the ionic rare earth mineral particles, and the diffusion layer is a coordination compound unit formed by the coordination of citrate anions and rare earth ions migrating from the compact layer) on the surface of the ionic rare earth mineral particles, thereby promoting the swelling of the ionic rare earth mineral particles and increasing the leaching rate. However, when the citrate anion coordinates with the rare earth ions on the surface of the ionic rare earth mineral particles, the originally trivalent rare earth ions are transformed into large-volume coordination compound units with zero or monovalent valence. The high ionic potential advantage of the compact layer disappears, and the rare earth ions are forced to migrate outward, entering the diffusion layer or even the solution. This causes the zeta potential of the ionic rare earth mineral particles to become negative, the water film layer to thicken, and the water permeation rate to decrease, resulting in the water film layer loaded with rare earth ions being unable to separate from the mineral ions. To address this, during the second leaching treatment, the addition of the non-ammonium inorganic salt can adjust the zeta potential of the ionic rare earth mineral particles back to the normal range. The ionic rare earth mineral particles shrink and aggregate, the water film layer thins, promoting solid-liquid separation, and allowing the leachate to completely overflow from the ionic rare earth mineral, thereby improving the recovery rate and rare earth leaching rate. Testing showed that the rare earth concentration peak of the leachate of this invention was significantly enhanced, shifted forward, and narrowed. Therefore, the enhanced leaching method for ionic rare earths of the present invention not only has the advantage of high leaching rate, but also the advantages of low leaching agent dosage and high tailings stability.

[0065] After obtaining the second leachate, the enhanced leaching method for ionic rare earth elements further includes the following steps:

[0066] Water is added to the ionic rare earth ore to obtain a third leachate;

[0067] The pH value and pollutant concentration of the third leachate are tested. When the pH value and pollutant concentration of the third leachate meet the discharge requirements, the addition of water to the ion-adsorption rare earth ore is stopped.

[0068] In at least one embodiment, the discharge requirement for the third leachate includes: the pH value of the third leachate is 6. 9. In the third leachate, the concentration of calcium and magnesium ions is less than 300 mg / L, and the concentration of aluminum ions is less than 3 mg / L.

[0069] In this invention, water can be added to the ion-adsorption rare earth ore to obtain a third leachate. The pH value and pollutant concentration of the third leachate are monitored. When the pH value and pollutant concentration of the third leachate meet the discharge requirements, the addition of water to the ion-adsorption rare earth ore is stopped to meet the discharge standards and avoid environmental pollution. In summary, this invention proposes an enhanced leaching method for ion-adsorption rare earths based on the changes in zeta potential, pH value, and leaching rate with electrolyte concentration during the leaching process, as well as the influence of the amount of electrolyte added and the leaching method.

[0070] After obtaining the first leachate, before performing a second leaching treatment on the ion-adsorption rare earth ore using the non-ammonium inorganic salt solution, the enhanced leaching method for ion-adsorption rare earth ore further includes the following steps:

[0071] A sodium salt solution and / or a potassium salt solution are provided, wherein the liquid-to-solid ratio of the sodium salt solution to the ionic rare earth ore is 0.01. The liquid-to-solid ratio of the potassium salt solution to the ionic rare earth ore is 0.01:1. The liquid-to-solid ratio of the sodium salt solution and potassium salt solution to the ionic rare earth ore is 0.01:1. 0.1:1;

[0072] The ionic rare earth ore is subjected to another leaching treatment using the sodium salt solution and / or potassium salt solution to obtain an intermediate leachate.

[0073] In at least one embodiment, the liquid-to-solid ratio of the sodium salt solution to the ionic rare earth ore is 0.01:1, 0.02:1, 0.04:1, 0.05:1, 0.06:1, or 0.1:1.

[0074] In at least one embodiment, the liquid-to-solid ratio of the potassium salt solution to the ionic rare earth ore is 0.01:1, 0.02:1, 0.04:1, 0.05:1, 0.06:1, or 0.1:1.

[0075] In at least one embodiment, the liquid-to-solid ratio of the mixed solution of sodium salt and potassium salt to the ionic rare earth ore is 0.01:1, 0.02:1, 0.04:1, 0.05:1, 0.06:1, or 0.1:1.

[0076] In at least one embodiment, the sodium salt may be sodium chloride or sodium nitrate.

[0077] In at least one embodiment, the potassium salt may be potassium chloride or potassium nitrate.

[0078] In the technical solution of this invention, the appropriate addition of sodium and potassium salts can avoid coordination competition between aluminum ions, calcium ions, and magnesium ions and citrate ions, thereby improving the rare earth leaching rate. However, excessive addition of sodium chloride is not conducive to improving the rare earth leaching rate.

[0079] Example 1

[0080] To investigate the effect of adding organic acids and their salts on rare earth leaching, when using organic acid salts as electrolytes for drip leaching of Dingnan ore samples, the high suspension properties of the Dingnan ore particles made sedimentation difficult, preventing the collection of supernatant for rare earth content analysis. Therefore, Example 1 employed two methods to study the effect of the amount of organic acid salts added on the rare earth leaching rate.

[0081] Method 1: Prepare a mixed solution of sodium citrate with a concentration of 0.4 mol / L and calcium chloride with a concentration of 0.6 mol / L; use the mixed solution as an electrolyte to continuously leach the Dingnan ore sample.

[0082] Method 2: Prepare 2 mL of 0.4 mol / L sodium citrate solution; prepare 0.6 mol / L calcium chloride solution; add 2 mL of 0.4 mol / L sodium citrate solution to the Dingnan ore sample; then continuously leach the Dingnan ore sample with 0.6 mol / L calcium chloride solution.

[0083] Depend on Figure 2 It can be seen that in Method 1, the rare earth leaching rate gradually increases with the increase of the concentration of the mixed solution. However, to obtain the ideal leaching rate, a higher concentration of the mixed solution is required. In Method 2, a higher leaching rate can be obtained when the concentration of calcium chloride is low, and the leaching rate does not change much with the increase of the concentration of calcium chloride.

[0084] In Examples 1 to 5, the total solution volume was maintained at 250 ml during drip leaching, containing 25 g of mineral sample. After drip leaching equilibrium, the solution was clarified, and samples were taken for rare earth concentration analysis to calculate the leaching rate. Subsequent Examples 1 to 5 all used a staged drip leaching method to leach the Dingnan mineral sample, and the description of taking the supernatant and calculating the leaching rate was omitted to avoid redundancy.

[0085] Example 2

[0086] To study the effect of the type of organic acid salt on the leaching rate, Example 2 uses three organic acid salts to study the effect of the type of organic acid salt on the rare earth leaching rate.

[0087] Specifically, 2 mL of 0.2 mol / L sodium citrate solution, 0.6 mol / L sodium acetate solution, and 0.3 mol / L sodium tartrate solution were dripped into the corresponding Dingnan ore samples, respectively, followed by dripping with 0.6 mol / L calcium chloride solution, with calcium chloride alone serving as a control.

[0088] It is understood that the concentration of organic acid salts in the examples is to maintain a consistent equivalent concentration.

[0089] Depend on Figure 3 It can be seen that the extraction rate is highest when sodium citrate solution is used.

[0090] Example 3

[0091] To determine the effect of sodium citrate solution concentration and dosage on the leaching rate, Example 3 used sodium citrate of different concentrations and dosages as the electrolyte solution for the first stage of drip leaching to study the effect of sodium citrate solution concentration and dosage on the rare earth leaching rate.

[0092] The corresponding Dingnan ore samples were leached dropwise with 2 mL of sodium citrate solutions with concentrations of 0.2 mol / L, 0.4 mol / L, and 0.6 mol / L, respectively; the leaching was then continued with 0.6 mol / L calcium chloride solution.

[0093] Depend on Figure 4 It can be seen that the extraction rate is higher when a high concentration of sodium citrate solution is used.

[0094] The corresponding Dingnan ore samples were leached dropwise with 2.5 mL, 3 mL, 3.5 mL, and 4 mL of 0.2 mol / L sodium citrate solution, respectively; the leaching was then continued with 0.6 mol / L calcium chloride solution.

[0095] Depend on Figure 5 It can be seen that the extraction rate is relatively high when using 4 mL of 0.2 mol / L sodium citrate solution.

[0096] In summary, increasing the concentration and dosage of sodium citrate solution during the first-stage leaching process is beneficial to improving the leaching rate, which also indicates that sodium citrate solution directly contributes to the leaching of rare earth elements.

[0097] Example 4

[0098] Example 3 shows that calcium chloride, as the leaching agent in the second-stage leaching process, has a certain impact on the leaching rate of rare earth elements. Example 4 uses calcium chloride solutions of different concentrations and amounts to study the effect of the concentration and amount of calcium chloride solution on the leaching rate of rare earth elements.

[0099] Several Dingnan ore samples were leached dropwise with 2 mL of 0.4 mol / L sodium citrate solution; then, the corresponding Dingnan ore samples were leached dropwise with 0.15 mol / L, 0.3 mol / L, 0.45 mol / L and 0.6 mol / L calcium chloride solutions, respectively.

[0100] Depend on Figure 6It can be seen that the leaching effect is best in the later stage when using a 0.6 mol / L calcium chloride solution. That is, the increase of calcium chloride concentration has an effect on the leaching rate in the later stage. The higher the concentration of calcium chloride solution, the smaller the decrease in leaching rate.

[0101] Example 5

[0102] To investigate the effect of the type and concentration of inorganic salts on the leaching rate, Example 5 uses three inorganic salts with different valence states to study the effect of the type and concentration of organic acid salts on the rare earth leaching rate.

[0103] The first stage of drip leaching used a 2 mL solution of 0.4 mol / L sodium citrate.

[0104] The leaching agents used in the second stage of drip leaching were 0.6 mol / L potassium sulfate, 0.6 mol / L sodium sulfate, 0.6 mol / L ammonium sulfate, 0.6 mol / L magnesium sulfate, 0.6 mol / L zinc sulfate, 0.2 mol / L ferric sulfate, 0.2 mol / L aluminum sulfate, 1.2 mol / L potassium chloride, 1.2 mol / L sodium chloride, 1.2 mol / L ammonium chloride, 0.6 mol / L magnesium chloride, 0.6 mol / L zinc chloride, 0.6 mol / L calcium chloride, 0.4 mol / L ferric chloride, and 0.4 mol / L aluminum chloride.

[0105] Several Dingnan ore samples were leached dropwise with 2 mL of 0.4 mol / L sodium citrate solution; the same leaching agent was then used to leach dropwise the corresponding Dingnan ore samples.

[0106] After drip leaching, the mixture was filtered, and the zeta potential, pH value, and conductivity of the filtered Dingnan ore particles suspension were measured during multiple water leachings to evaluate the characteristics of the tailings.

[0107] Depend on Figure 7 It can be seen that the different variation patterns are due to the differences in the coordination ability of various sulfate electrolytes with citric acid and the differences in the exchange leaching ability of cations for rare earth elements. Specifically, the decrease in leaching rate in the first stage decreases in the order of iron, aluminum, zinc, and magnesium, while in the second stage it increases in the order of magnesium, aluminum, zinc, and iron.

[0108] Depend on Figure 8 It can be seen that the suspension obtained after aluminum sulfate leaching has the smallest absolute value of zeta potential, followed by ferric sulfate, zinc sulfate, etc., proving that the zeta potential of the suspension is directly related to the extent of improvement in subsequent leaching efficiency.

[0109] Depend on Figure 9It is known that the pH value of the suspension obtained after leaching with aluminum sulfate, ferric sulfate, and zinc sulfate is low, and it needs to be neutralized with lime to a value above 6 in order to meet environmental requirements.

[0110] Depend on Figure 10 It can be seen that the conductivity of the suspension decreases with the increase of the number of water washes.

[0111] Depend on Figure 11 It can be seen that the different variation patterns are due to the differences in the coordination ability of various chloride electrolytes with citric acid and the differences in the exchange leaching ability of cations for rare earth elements. Specifically, the decrease in leaching rate in the first stage decreases in the order of iron, aluminum, zinc, calcium, and magnesium, while in the second stage it increases in the order of aluminum, zinc, and iron.

[0112] Depend on Figure 12 It can be seen that the suspension obtained after leaching with aluminum chloride has the smallest absolute value of zeta potential, followed by ferric chloride, zinc chloride, etc., proving that the zeta potential of the suspension is directly related to the extent of improvement in subsequent leaching efficiency.

[0113] Depend on Figure 13 It is known that the pH value of the suspension obtained after leaching with aluminum chloride, ferric chloride, and zinc chloride is low, and it needs to be neutralized with lime to a value above 6 in order to meet environmental requirements.

[0114] Depend on Figure 14 It can be seen that the conductivity of the suspension decreases with the increase of the number of water washes.

[0115] The above results demonstrate that the inorganic salt cations used in the second stage compete with rare earth ions for coordination with citric acid. Rare earth ions initially coordinated with citric acid decompose upon encountering aluminum, iron, or zinc, and are re-adsorbed by clay minerals, significantly reducing the leaching rate. Divalent cations such as calcium and magnesium also contribute to a decrease in rare earth leaching rate. However, as the cation concentration increases, their exchange leaching capacity for rare earth ions strengthens, thus restoring the rare earth leaching rate. Aluminum cations, in particular, can dramatically increase the rare earth leaching rate, while the recovery rate from iron cation exchange leaching is much smaller, which is related to the stronger hydrolysis tendency of iron cations.

[0116] A larger absolute value of the zeta potential indicates stronger electrorepulsion between clay particles, better suspension, and a greater susceptibility to soil erosion, landslides, and other dangerous events. The pH value of the system after water leaching objectively reflects the acidity of the mine soil after rainwater infiltration; excessively high or low acidity is detrimental to the survival of plants and organisms. The rare earth element content in the solution flowing out of the tailings after water leaching is extremely low; therefore, the measured conductivity value is equivalent to the concentration of other electrolytes in the solution, with higher concentrations indicating more electrolytes. The above experimental results show that, using sodium citrate solution as a guide, the suspension stability of clay particles in the tailings water leaching system after drip leaching with different valence inorganic salt leaching agents decreases sequentially in the order of monovalent, divalent, and trivalent inorganic electrolytes.

[0117] Regarding the pH values ​​of the tailings leaching system after drip leaching with sodium citrate solution as a lead inorganic salt leaching agent of different valence states: after three water leachings, the pH value of the trivalent inorganic salt electrolyte system is lower, while the pH values ​​of the divalent and monovalent inorganic salt electrolyte systems are close to neutral, which meets the requirements of green environmental protection.

[0118] For the electrolyte concentration of the tailings after water leaching following drip leaching with sodium citrate solution as a lead inorganic salt leaching agent of different valence states, the electrolyte concentration in the solution after the first water leaching is related to the concentration of the drip leaching electrolyte; the higher the drip leaching concentration, the higher the electrolyte concentration in the solution after the first water leaching. However, the concentrations of each electrolyte in the solution after the second and third water leachings are not significantly different.

[0119] Example 6

[0120] Weigh 100g of ion-adsorption type rare earth ore (below 20 mesh) into a sand core glass column, with filter paper placed on the top and bottom to make the seepage more uniform;

[0121] When leaching ion-adsorption type rare earth ores, the leaching operation is carried out at a total liquid-to-solid ratio of 1:1. First, several organic acid salt solutions (sodium citrate solution, ammonium citrate solution, potassium citrate solution, sodium tartrate solution, malic acid solution, sodium acetate solution, citric acid solution, and EDTA solution) at a liquid-to-solid ratio of 0.3:1 are added to the upper layer of the corresponding ion-adsorption type rare earth ores. After all the solutions have entered the corresponding ion-adsorption type rare earth ores layer, a calcium chloride solution with a concentration of 0.128 mol / L is added to the corresponding ion-adsorption type rare earth ores layer at a liquid-to-solid ratio of 0.7:1. Finally, deionized water is added to the corresponding ion-adsorption type rare earth ores layer at a ratio of 1:1.

[0122] The leachate was collected every 10 mL, and the rare earth content was determined. The leaching rate was calculated using a comparative method, with the total rare earth content in the entire leachate obtained from a full rinse using an excess of 2% (0.15N) ammonium sulfate as the calculation basis, recorded as 100%. The results showed that, compared to other organic acid salts, sodium citrate, ammonium citrate, and potassium citrate significantly advanced the rare earth leaching peak. Among them, sodium citrate solution had the best effect on promoting early leaching of rare earths, achieving a rare earth leaching rate of 100.68% when the liquid-to-solid ratio of the collected solution was 0.3. When the liquid-to-solid ratio of the collected solution was 0.3, the order of rare earth leaching rates was: sodium citrate > ammonium citrate > potassium citrate > sodium tartrate > malic acid > sodium acetate > citric acid > EDTA.

[0123] Example 7

[0124] Following the analytical method described in Example 6, sodium citrate solutions of different concentrations (liquid-to-solid ratio of 0.3, with concentrations of 0.03366 mol / L, 0.06732 mol / L, 0.101 mol / L, 0.1346 mol / L, 0.1683 mol / L, and 0.202 mol / L, respectively) were first added to the upper layer of the corresponding ion-adsorption rare earth ore. After all the solution had entered the corresponding ion-adsorption rare earth ore layer, a calcium chloride solution with a concentration of 0.128 mol / L was added to the corresponding ion-adsorption rare earth ore layer at a liquid-to-solid ratio of 0.7:1. Finally, deionized water was added to the corresponding ion-adsorption rare earth ore layer at a ratio of 1:1.

[0125] The leachate was collected every 10 mL, and the rare earth and citrate contents were measured. The citrate residue rate was the ratio of the total citrate content measured in the leachate to the corresponding total citrate added. Results showed that sodium citrate solutions with concentrations higher than 0.03366 mol / L promoted earlier rare earth leaching, and the rare earth effluent peak shifted forward with increasing sodium citrate solution concentration. Considering the cost of the leaching agent and its environmental impact, the optimal concentration of sodium citrate solution was 0.1346 mol / L. Furthermore, the citrate content remaining in the tailings after staged leaching with different concentrations of sodium citrate solution and calcium chloride varied, but all were above 18%, which can provide organic carbon for subsequent tailings remediation.

[0126] Example 8

[0127] Following the analytical method described in Example 6, a sodium citrate solution with a liquid-to-solid ratio of 0.1:1 and a concentration of 0.1346 mol / L was added to the upper layer of the ion-adsorption rare earth ore. After the solution had completely entered the ion-adsorption rare earth ore layer, a calcium chloride solution with a liquid-to-solid ratio of 0.9:1 and a concentration of 0.128 mol / L was added to the upper layer of the ion-adsorption rare earth ore. Finally, deionized water was added to the corresponding ion-adsorption rare earth ore layer at a ratio of 1:1. The leachate was collected every 10 mL and the rare earth content was measured.

[0128] Following the analytical method described in Example 6, a sodium citrate solution with a liquid-to-solid ratio of 0.2:1 and a concentration of 0.1346 mol / L was added to the upper layer of the ion-adsorption rare earth ore. After the solution had completely entered the ion-adsorption rare earth ore layer, a calcium chloride solution with a liquid-to-solid ratio of 0.8:1 and a concentration of 0.128 mol / L was added to the upper layer of the ion-adsorption rare earth ore. Finally, deionized water was added to the corresponding ion-adsorption rare earth ore layer at a ratio of 1:1. The leachate was collected every 10 mL and the rare earth content was measured.

[0129] Following the analytical method described in Example 6, a sodium citrate solution with a liquid-to-solid ratio of 0.3:1 and a concentration of 0.1346 mol / L was added to the upper layer of the ion-adsorption rare earth ore. After the solution had completely entered the ion-adsorption rare earth ore layer, a calcium chloride solution with a liquid-to-solid ratio of 0.7:1 and a concentration of 0.128 mol / L was added to the upper layer of the ion-adsorption rare earth ore. Finally, deionized water was added to the corresponding ion-adsorption rare earth ore layer at a ratio of 1:1. The leachate was collected every 10 mL and the rare earth content was determined.

[0130] The results show that as the liquid-to-solid ratio of sodium citrate solution with the same concentration increases, the rare earth effluent peak shifts forward and the peak value gradually increases. Therefore, the optimal liquid-to-solid ratio for adding sodium citrate solution in this application is 0.3:1.

[0131] Example 9

[0132] The results above show that the sodium citrate solution in the first stage can exchange most of the rare earth elements. Considering the cost factor, the amount of leaching agent used in the second stage can be appropriately reduced for the small amount of rare earth elements that are not leached later. Therefore, the applicant studied the effect of the amount of calcium chloride solution used in the second stage on the leaching of rare earth elements.

[0133] The results showed that the rare earth leaching rate increased with the increase of calcium chloride solution volume. However, when the calcium chloride solution volume exceeded 30 mL, the increase in rare earth leaching rate was small, and the optimal amount of calcium chloride solution added was 30 mL. Using this as the experimental condition, the applicant further changed the concentration of calcium chloride solution to explore the effect on the rare earth leaching rate, but the results showed that the concentration of calcium chloride solution had little effect on the rare earth leaching rate.

[0134] Taking all factors into consideration, the optimal liquid-to-solid ratio for calcium chloride addition under the experimental conditions was 0.3:1, with a concentration of 0.032 mol / L. This differs from the results of Example 4 because during column leaching, the rare earth elements leached from citrate move downwards and do not directly contact the calcium chloride solution. Therefore, the competition for coordination between calcium and citrate is minimal, having little impact on the rare earth leaching rate. In this case, only the regulation of the zeta potential of ion-adsorbed rare earth minerals by cations needs to be considered. This helps reduce the consumption of leaching agent and lowers the risk of excessive wastewater generated by rainwater leaching.

[0135] Example 10

[0136] The applicant re-examined the impact of the types of inorganic salts in the second stage on rare earth leaching. Based on the above results, a 0.1346 mol / L sodium citrate solution with a liquid-to-solid ratio of 0.3:1 was added in the first stage, followed by the addition of 0.256N calcium chloride, magnesium chloride, aluminum sulfate, and ammonium sulfate with a liquid-to-solid ratio of 0.7:1. Subsequently, deionized water was added at a 1:1 ratio. After collecting the leachate, the rare earth content was measured and the leaching efficiency was calculated.

[0137] The results showed that when calcium chloride, magnesium chloride, aluminum sulfate, and ammonium sulfate were used as the second-stage leaching agents, the order of rare earth leaching rates was: ammonium sulfate ≈ aluminum sulfate > magnesium chloride > calcium chloride. However, the total rare earth leaching rates were all above 100%, and the differences were not significant.

[0138] The results show that this invention, using sodium citrate solution as the leaching agent at a liquid-to-solid ratio of 0.3:1 and inorganic salt leaching agent at a liquid-to-solid ratio of 0.7:1, can achieve a higher rare earth leaching rate than ammonium sulfate at a liquid-to-solid ratio of 2:1, and the required leaching agent concentration is not high. The inorganic salt leaching solution used can be a solution of one or more inorganic electrolytes, especially calcium magnesium chloride, which makes it easier to meet wastewater discharge requirements for the zeta potential, pH value, and conductivity of the leached tailings.

[0139] Example 11

[0140] As can be seen from the results of Example 10, compared with ammonium sulfate, the total leaching efficiency of rare earth is not high when aluminum sulfate, magnesium chloride and calcium chloride are used as leaching agents in the second stage. This is because the citrate added in the previous stage will complex with aluminum ions, calcium ions and magnesium ions, which will cause rare earth to compete with these cations while coordinating with citrate, thus reducing the leaching efficiency of rare earth.

[0141] Therefore, the applicant added a short sodium chloride leaching step between the sodium citrate solution and the respective inorganic salts (aluminum sulfate, magnesium chloride, and calcium chloride) in the staged leaching process to prevent direct contact between the citrate rare earth leaching solution and the subsequent high-valence cation electrolyte solution, thereby eliminating rare earth back-absorption caused by coordination competition.

[0142] The method in Experiment Eleven is similar to that in Example Ten, including: first adding a 0.1346 mol / L sodium citrate solution (liquid-to-solid ratio of 0.3:1), then adding a 0.256N sodium chloride solution with a liquid-to-solid ratio of 0.01:1 (alternatively, the liquid-to-solid ratio can also be 0.02:1, 0.04:1, 0.06:1, 0.07:1, or 0.1:1), then adding a 0.256N calcium chloride solution (liquid-to-solid ratio of 0.7:1, or alternatively adding magnesium chloride solution or aluminum sulfate solution), followed by adding 1:1 deionized water, collecting the leachate and determining the rare earth content, and calculating the leaching efficiency.

[0143] The results showed that appropriate addition of sodium chloride could avoid coordination competition between aluminum, calcium, and magnesium ions and citrate ions, thus improving the rare earth leaching rate. However, excessive addition of sodium chloride was detrimental to improving the rare earth leaching rate. Specifically, for the aluminum sulfate leaching agent in the second stage, the optimal liquid-to-solid ratio of sodium chloride was 0.01. 0.07:1; For the second stage of calcium chloride and magnesium chloride leaching agents, the optimal liquid-to-solid ratio for sodium chloride is 0.01. 0.03:1.

[0144] The above description is merely a preferred embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural transformations made using the content of the present invention under the inventive concept of the present invention, or direct / indirect applications in other related technical fields, are included within the patent protection scope of the present invention.

Claims

1. A method for enhanced leaching of ion-type rare earth elements, comprising the following steps: The solution provides ionic rare earth ore, citrate solution, and non-ammonium inorganic salt solution, wherein the liquid-to-solid ratio of the citrate solution to the ionic rare earth ore is 0.

1. The liquid-to-solid ratio of the non-ammonium inorganic salt solution to the ionic rare earth ore is 0.5:

1. 0.9:1; The ionic rare earth ore was subjected to a first leaching treatment using the citrate solution to obtain a first leachate. The ionic rare earth ore that has undergone the first leaching treatment is subjected to a second leaching treatment using the non-ammonium inorganic salt solution to obtain a second leachate. The first leachate is subjected to a first post-processing treatment to obtain rare earth elements; and The second leachate is subjected to a second post-processing treatment to obtain rare earth elements.

2. The enhanced leaching method for ion-type rare earth elements according to claim 1, characterized in that: The concentration of citrate in the citrate solution is in the range of 0.01%. 0.3 mol / L.

3. The enhanced leaching method for ion-type rare earth elements according to claim 1, characterized in that: In the non-ammonium inorganic salt solution, the concentration range of the non-ammonium inorganic salt is 0.1%. 0.6 mol / L.

4. The enhanced leaching method for ion-type rare earth elements according to claim 1, characterized in that: In the citrate solution, the citrate is at least one of a sodium salt, a potassium salt, and an ammonium salt.

5. The enhanced leaching method for ion-type rare earth elements according to claim 1, characterized in that: The non-ammonium inorganic salt in the non-ammonium inorganic salt solution is at least one of the following: soluble chloride of alkali metal, soluble nitrate of alkali metal, soluble sulfate of alkali metal, soluble chloride of alkaline earth metal, soluble nitrate of alkaline earth metal, soluble sulfate of alkaline earth metal, soluble chloride of aluminum, soluble nitrate of aluminum, and soluble sulfate of aluminum.

6. The enhanced leaching method for ion-type rare earth elements according to claim 1, characterized in that: The first post-processing includes the steps of first extraction, back-extraction, first precipitation treatment, and second extraction of the first leachate, wherein the first precipitation treatment yields the first rare earth hydroxide.

7. The enhanced leaching method for ion-type rare earth elements according to claim 6, characterized in that: The second post-processing includes the following steps: subjecting the second leachate to a second precipitation treatment to obtain a second rare earth hydroxide; mixing the first rare earth hydroxide and the second rare earth hydroxide to obtain a mixture; and subjecting the mixture to the second extraction to obtain rare earth.

8. The enhanced leaching method for ion-type rare earth elements according to claim 7, characterized in that: The precipitant used in the first precipitation treatment and the second precipitation treatment is at least one of calcium oxide, magnesium oxide, and ammonium bicarbonate.

9. The enhanced leaching method for ion-type rare earth elements according to claim 1, characterized in that: After obtaining the second leachate, the enhanced leaching method for ionic rare earth elements further includes the following steps: Water is added to the ionic rare earth ore to obtain a third leachate; The pH value and pollutant concentration of the third leachate are tested. When the pH value and pollutant concentration of the third leachate meet the discharge requirements, the addition of water to the ion-adsorption rare earth ore is stopped.

10. The enhanced leaching method for ion-type rare earth elements according to claim 1, characterized in that: After obtaining the first leachate, before performing a second leaching treatment on the ion-adsorption rare earth ore using the non-ammonium inorganic salt solution, the enhanced leaching method for ion-adsorption rare earth ore further includes the following steps: A sodium salt solution and / or a potassium salt solution are provided, wherein the liquid-to-solid ratio of the sodium salt solution to the ionic rare earth ore is 0.

01. The liquid-to-solid ratio of the potassium salt solution to the ionic rare earth ore is 0.01:

1. The liquid-to-solid ratio of the sodium salt solution to the potassium salt solution, or the mixed solution of the sodium salt solution and the potassium salt solution, to the ionic rare earth ore is 0.01:

1. 0.1：1； The ionic rare earth ore is subjected to another leaching treatment using the sodium salt solution and / or potassium salt solution to obtain an intermediate leachate.

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