A method for mining, beneficiation and smelting of ion-type rare earth

Abstract

The application provides a short process preparation method for mining, beneficiation and smelting of ionic rare earth, and belongs to the technical field of rare earth preparation.The application comprises the following steps: separating monovalent and high-valence ions from the clear solution of the pretreated ionic rare earth leaching mother liquor, obtaining a permeate and a retentate;returning the permeate to the preparation of the leaching agent for recycling;generating a rare earth concentrated solution through multi-stage concentration of the retentate, and directly using the rare earth concentrated solution for rare earth refining;sequentially adding an extractant and a back-extracting agent to the rare earth concentrated solution, obtaining a rare earth concentrated solution;and refining the rare earth concentrated solution to obtain ionic rare earth.The application is an integrated membrane separation technology composed of nanofiltration and multi-stage reverse osmosis membranes without additional chemical precipitants, and the integrated membrane separation technology is used to update and replace the traditional processes of in-situ rare earth leaching, chemical impurity removal, chemical precipitation and acid dissolution-extraction rare earth separation and purification, so that the process flow of the mining, beneficiation and smelting of ionic rare earth is simplified, the cost is reduced, and the recovery rate of the rare earth is improved.

Description

Technical Field

[0001] This invention relates to the field of rare earth preparation technology, and particularly to a method for preparing ionic rare earths, specifically a short-process preparation method for mining, beneficiation and smelting of ionic rare earths. Background Technology

[0002] Ionic rare earth elements are medium-heavy rare earth elements that are adsorbed in an ionic state in the soil of rare earth mines. Currently, the mining, beneficiation, and smelting processes for ionic rare earth elements are (e.g.) Figure 1 (As shown): Rare earth mine vegetation removal - manual drilling - in-situ leaching of leachate - chemical removal of rare earth mother liquor - chemical precipitation - solid-liquid separation - solid rare earth acid dissolution - extraction separation and purification. First, vegetation on the surface of the rare earth mine is removed manually. Then, holes are manually drilled in a specific distribution using a Luoyang shovel. Next, the prepared leachate is injected into the drilled holes in the rare earth mine via drip irrigation. Ion exchange is used to replace and leach the ionized rare earth elements adsorbed in the soil, yielding a rare earth leachate mother liquor. The rare earth mother liquor is collected and pumped into a rare earth mother liquor collection tank. A low concentration of sodium bicarbonate (or ammonium bicarbonate) is added, and after pneumatic stirring and reaction, the mixture is allowed to settle. Impurities such as aluminum ions and silicon are removed as precipitates. The supernatant after impurity removal enters a chemical precipitation tank. Excessive amounts of high-concentration sodium bicarbonate (or ammonium bicarbonate) precipitant and coagulant are added to the chemical precipitation tank to obtain rare earth carbonate precipitate. The supernatant from the chemical precipitation tank is returned to the leaching solution preparation and reuse water tank. The rare earth carbonate precipitated at the bottom of the precipitation tank is sent to the solid-liquid separation workshop, where solid-liquid separation is achieved through plate and frame filtration to obtain solid rare earth carbonate. The solid rare earth carbonate is transported to the rare earth smelting plant, where it is first dissolved in acid to form a rare earth solution, and then an extractant is added. Ionic rare earth enters the extraction phase, and after back-extraction, a high-concentration rare earth concentrate is obtained, thereby achieving the purpose of separating and purifying ionic rare earth.

[0003] This process involves chemical purification of rare earth mother liquor and chemical precipitation, which consume large amounts of chemical precipitants. It requires the construction of large-capacity chemical precipitation reaction tanks, as well as reagent preparation tanks and specialized reagent preparation personnel. Each precipitation reaction tank requires multiple operators for reagent addition and solid-liquid separation. The separation of rare earth precipitates and supernatants relies entirely on the operators' personal experience. During rare earth carbonate smelting, acid is used to dissolve rare earth carbonates into ionic states, generating large amounts of high-salt wastewater. In this mining, beneficiation, and smelting process, rare earth ions undergo a transformation from liquid ions to solid precipitates and then back to ions. The process is lengthy, consuming large amounts of chemical purification and precipitant agents, and relying entirely on the operators' personal experience in multiple separation stages. It often happens that rare earth carbonate precipitates (small particles) that cannot be completely precipitated in the supernatant of the chemical precipitation tank are discharged into the leachate distribution and reuse tank, and then returned to the soil of the rare earth mine through leaching drip irrigation. These rare earth precipitates are difficult to leach again with rare earth leachate, resulting in a large loss of rare earth in the rare earth mine.

[0004] Currently, there are numerous patent applications for mining, beneficiation, and smelting of ion-adsorption rare earths, mainly focusing on in-situ leaching, leaching solution impurity removal, rare earth mine restoration, tailings treatment, and rare earth smelting wastewater treatment. For example, invention patent application number CN202211195950.5 discloses a tiered leaching method: based on the geological conditions of the ion-adsorption rare earth mining area, leaching solution guide holes, leaching solution collection ditches, and rainwater drainage ditches are constructed according to volume division. The leaching solution seeps into the leaching solution guide holes set within the ore body, and finally collects in the seepage collection well at the foot of the mountain. After separation and purification, the leaching solution is returned to the mining area for injection. For example, patent application CN201911023135.9 discloses a device and method for intercepting and collecting ion-type rare earth leaching solution in situ. It uses a collection pipe with a female receiving port and an insertable male connector at both ends. The collection pipe has upward-facing intercepting flaps and a hydrophobic mesh on both sides, allowing the downward-flowing rare earth leachate to be intercepted and collected via a V-shaped guide channel formed by multiple interconnected intercepting and collecting devices. For example, patent application CN202410765206.7 discloses a device for electrically enhanced leaching of ion-type rare earth. It utilizes the electric effect of an external electric field to promote ion desorption and accelerate solution flow, thereby achieving rapid leaching of ion-type rare earth. For example, patent application CN202223266604.X discloses a system for purifying rare earth from ion-type rare earth ores, including a pretreatment device, an ion adsorption device, and a precipitation recovery device. The pretreatment device first pre-treats the rare earth ore, then uses an adsorption device filled with ion exchange resin to separate and enrich the rare earth ore. After the resin is saturated, desorption treatment is performed to achieve continuous separation and enrichment of the rare earth ore. For example, the invention patent with application number CN202323474978.5 discloses a permeable reaction system for the remediation of groundwater pollution in ion-type rare earth mining areas. This system achieves in-situ remediation of groundwater pollution in mining areas by setting up a permeable reaction system with a first transition zone, a second transition zone, a denitrification zone, a third transition zone, an adsorption zone, and a fourth transition zone underground. Another example is the invention patent with application number CN202111642307.8, which discloses a method for recovering valuable elements from the residue generated by chemical precipitation and impurity removal of rare earth leaching solutions. First, concentrated sulfuric acid is used for leaching, followed by filtration to obtain leachates containing rare earth, aluminum, uranium, and thorium. The valuable elements are then recovered through extraction.For example, patent application CN202410645819.7 discloses a green mining method integrating leaching, smelting, and leaching of ion-type rare earth ores. The method involves mixing leaching tailings, hydrometallurgical supernatant membrane concentrate, and leaching agent to obtain a leaching solution, which is then injected into the leaching field for leaching. The leaching mother liquor is collected through a collection liquid. After aluminum removal using an aluminum removal agent, the mother liquor reacts with a precipitant, resulting in solid-liquid separation to obtain rare earth products and hydrometallurgical supernatant. The supernatant is then membrane concentrated to obtain hydrometallurgical supernatant membrane concentrate and hydrometallurgical supernatant membrane concentrate desalinated water. This membrane concentrate desalinated water is reinjected into the leaching process. The membrane concentrate desalinated water obtained from different leaching cycles is reused in a tiered manner, and the leaching tailings are used for leaching, saving on leaching agent and acid usage. Another example is patent application CN202210392497.0, which discloses a solidifying agent for abandoned mines in ion-type rare earth in-situ leaching. This solidifying agent, when used to solidify rare earth in-situ leaching waste, effectively solves the problem of soft soil and prevents landslides. For example, patent application CN202410211498.X discloses a method for in-situ leaching and mineralization stabilization of thallium in ion-type rare earth leaching fields. This method involves in-situ leaching of the leaching field, treatment of thallium in the leaching tailings, in-situ mineralization stabilization, and backfilling remediation, addressing thallium release at its source. Another example is patent application CN2024102462248.X, which discloses a green mining method for ion-type rare earth ores. This method involves injecting leaching solution into the leaching field for in-situ leaching to obtain leaching mother liquor. Leaching water is then injected into the leaching field after leaching to obtain leaching solution. The leaching mother liquor and leaching mother liquor are mixed to obtain mother liquor, which is then subjected to aluminum removal treatment to obtain aluminum-removed solution. This solution is then subjected to precipitation treatment to obtain precipitated solution and rare earth products. The precipitated solution is further subjected to calcium removal treatment to obtain calcium-removed solution. After acid adjustment and membrane concentration, the concentrate is used as the leaching solution, and fresh water is used as leaching water. Improving the quality of rare earth products and recovering rare earths and leaching agents from leaching tailings reduces the risk of water pollution. For example, patent application CN202410033133.2 discloses a waste-free mining method for in-situ double salt leaching in ion-type rare earth mines. It uses an inorganic sulfate compound leaching agent, performs in-situ leaching through an injection system, removes aluminum ions using an aluminum-rich agent, and precipitates rare earths using carbonates, without introducing new cations and eliminating ammonia nitrogen pollution. Another example is patent application CN202410812057.5, which discloses a method for preparing ammonium chloride from high-salt wastewater in ion-type rare earth separation by evaporation. An alkaline substance is added to the high-salt wastewater to obtain pretreated wastewater, which is then evaporated and crystallized to obtain ammonium chloride product and crystallization mother liquor. The organic phase containing the extractant is extracted and separated to obtain raffinate, which is then returned to the pretreated wastewater for combined evaporation and crystallization.For example, the invention patent with application number CN202311394195.8 discloses a precipitation-organic extraction enrichment process for ion-type rare earth leaching mother liquor. Calcium and magnesium compounds are added to the leaching mother liquor to adjust the pH value to 5.1-5.4. The supernatant is then used to control the precipitation pH to 7.5-8.5 with calcium and magnesium compounds until the rare earth is completely precipitated. After solid-liquid separation, extraction, and back-extraction, a rare earth feed solution with a rare earth concentration greater than 200 g / L is obtained, which meets the requirements for rare earth smelting and separation. Xin Yuntao (CN202410043785.4) applied for an ion-type rare earth leaching and enrichment process: leaching agent is injected into the ore body to obtain leaching mother liquor. The low-concentration mother liquor with a concentration below 1 g / L is filtered to obtain concentrated liquid 1 and permeate 1. The permeate is filtered again to obtain concentrated liquid 2 and permeate 2. Concentrated liquid 1 and 2 are mixed to obtain enriched liquid. A chemical precipitant is added to the concentrated liquid with a concentration greater than 1 g / L to produce rare earth products. The supernatant is returned to the leaching process. Permeate 1 and permeate 2 are mixed and returned to the leaching process. For example, Wang Zhigao (Hydrometallurgy, 2014, 33(6): 469-472) pretreated the rare earth mother liquor from ammonium sulfate leaching with a ceramic membrane, and then concentrated it with a nanofiltration membrane, enriching the rare earth content from 0.46 g / L to 4.23 g / L.

[0005] From the publicly disclosed invention patents and papers, some focus on developing novel or compound leaching agents for ionic rare earths; others on the graded utilization and recycling of leachate; still others address the risk of thallium leaching and geological hazards such as loose soil after in-situ leaching, proposing in-situ solidification agents for thallium and soil. Some involve membrane concentration of the leachate to increase the concentration of chemical precipitation; others involve membrane treatment of the supernatant after chemical precipitation followed by water return for leaching; and still others describe methods for preparing ammonium chloride products from high-salt wastewater produced in the smelting process. Wang Zhigao used ultrafiltration and nanofiltration for concentration, but the concentration ratio of rare earths was low, making it difficult to meet the concentration requirements of the smelting process. All the publicly disclosed invention patents mentioned above are similar to current traditional leaching, mining, and smelting processes for ionic rare earths, with only minor adjustments. These traditional mining, beneficiation, and smelting processes generally have the following drawbacks: long process flow, rare earth products need to undergo multiple phase changes, low rare earth recovery rate, and incomplete solid-liquid separation in chemical precipitation tanks leading to rare earth loss. Summary of the Invention

[0006] In view of this, to address the technical problems of long process flow, low rare earth recovery rate, and rare earth loss due to incomplete solid-liquid separation in chemical precipitation tanks in the existing technology for preparing ionic rare earths, this invention provides a method for the mining, beneficiation, and smelting of ionic rare earths. It utilizes an integrated membrane separation technology consisting of nanofiltration and multi-stage reverse osmosis membranes, which eliminates the need for external chemical reagents. This integrated membrane separation technology updates and replaces traditional in-situ rare earth leaching, chemical precipitation, and acid dissolution-extraction processes for rare earth separation and purification, simplifying the mining, beneficiation, and smelting process of ionic rare earths, reducing production costs, increasing rare earth recovery rate, and reducing losses.

[0007] To achieve the above objectives, the present invention provides the following technical solution:

[0008] A method for preparing ionic rare earth elements includes the following steps:

[0009] Step (1): The clear liquid obtained after pretreatment of the ion-type rare earth leaching mother liquor is separated into monovalent and high-valent ions to obtain permeate and intercepted liquid respectively.

[0010] Step (2): The permeate is returned to the leaching agent preparation tank for the preparation of the leaching agent, so as to realize the full reuse of production water; the retentate is concentrated by subsequent multi-stage reverse osmosis membranes to obtain rare earth concentrate, which is then directly used for rare earth extraction.

[0011] Step (3): Extract and back-extract the rare earth concentrate from step (2) sequentially to obtain a rare earth concentrate.

[0012] Step (4): The rare earth concentrate from step (3) is refined to obtain ionic rare earth.

[0013] Preferably, in step (2), the multi-stage reverse osmosis membrane concentration is determined based on the concentration of rare earth ions in the retentate.

[0014] Preferably, in step (2), the multi-stage reverse osmosis membrane concentration is converted into a four-stage reverse osmosis membrane concentration.

[0015] Preferably, the four-stage reverse osmosis membrane concentration includes:

[0016] First-stage reverse osmosis membrane concentration: When the rare earth ion concentration is below 0.5 g / L, a low-pressure, high-flux reverse osmosis membrane element is used;

[0017] Second-stage reverse osmosis membrane concentration: When the rare earth ion concentration is concentrated to 1.2 g / L, a medium-pressure, high-rejection-rate reverse osmosis membrane is used;

[0018] Third-stage reverse osmosis membrane concentration: When the rare earth ion concentration is concentrated to 2.4 g / l, a high-pressure, high-rejection-rate reverse osmosis membrane is used;

[0019] Fourth-stage reverse osmosis membrane concentration: When the rare earth ion content exceeds 4 g / L, a disc tube type ultra-high pressure reverse osmosis membrane is used.

[0020] Preferably, the first-stage reverse osmosis membrane concentration operating pressure is 1.0-1.6 MPa;

[0021] The operating pressure for the second-stage reverse osmosis membrane concentration is 1.5-2.5 MPa;

[0022] The operating pressure for the third-stage reverse osmosis membrane concentration is 2.0-4.5 MPa;

[0023] The operating pressure for the fourth-stage reverse osmosis membrane concentration is 4.0-7.5 MPa.

[0024] Preferably, the permeate from the second-stage reverse osmosis membrane concentration is returned to the first-stage reverse osmosis membrane concentration.

[0025] The permeate from the third-stage reverse osmosis membrane concentration is returned to the second-stage reverse osmosis membrane concentration.

[0026] The permeate from the fourth-stage reverse osmosis membrane concentration is returned to the third-stage reverse osmosis membrane concentration.

[0027] The permeate from the first-stage reverse osmosis membrane concentration is returned to the water tank for preparing the leaching agent.

[0028] Preferably, in step (1), a nanofiltration membrane is used to separate monovalent and high-valent ions.

[0029] Preferably, the operating pressure of the nanofiltration membrane is 0.4-1.2 MPa.

[0030] Preferably, in step (3), the extractant is added directly to the rare earth concentrate for separation and purification, without the need for acid dissolution.

[0031] Preferably, in step (1), the pretreatment is gravity removal.

[0032] Compared with the prior art, the present invention has the following beneficial effects:

[0033] The method for preparing ionic rare earth provided by this invention uses an integrated membrane separation technology consisting of nanofiltration and multi-stage reverse osmosis membranes that do not require the addition of external chemical reagents. This integrated membrane separation technology updates and replaces the traditional in-situ rare earth leaching, chemical precipitation, and acid dissolution-extraction processes for rare earth separation and purification, simplifying the mining, beneficiation, and smelting processes of ionic rare earth, reducing production costs, increasing rare earth recovery rates, and reducing losses.

[0034] This invention focuses on ion-type rare earth leaching mother liquor. The supernatant after gravity impurity removal is first separated into monovalent and high-valent ions using nanofiltration membranes. The high-valent rare earth ions retained by the nanofiltration membranes are then concentrated using multi-stage reverse osmosis membranes. The permeate from the first-stage reverse osmosis membrane is returned to the leaching agent for recycling. The multi-stage reverse osmosis membranes are selected based on the rare earth concentration, using low-pressure (first-stage reverse osmosis membrane concentration), medium-pressure (second-stage reverse osmosis membrane concentration), high-pressure (third-stage reverse osmosis membrane concentration), and ultra-high-pressure (fourth-stage reverse osmosis membrane concentration) membranes in a cascaded integration. The resulting rare earth concentrate is directly sent to a rare earth smelter for the addition of an extractant for rare earth separation and purification. The mining, beneficiation, and smelting process provided by this invention uses only nanofiltration and reverse osmosis membranes, without the need for additional chemical precipitants and flocculants. It also eliminates the need for chemical precipitation tanks and aeration devices, significantly saving on rare earth ion chemical impurity removal agents, precipitants, infrastructure investment, and labor costs. Rare earth leaching mother liquor is directly separated and concentrated through an integrated membrane, and the concentrate is sent to the extraction section. This reduces the need for chemical impurity removal, chemical precipitation, plate and frame filtration, and rare earth carbonate acid dissolution sections, thereby reducing the amount of rare earth chemical impurity removers, precipitants, and rare earth dissolving acids used. This greatly simplifies the mining, beneficiation, and smelting process of ion-adsorption rare earths and significantly reduces the production cost of ion-adsorption rare earths.

[0035] This invention eliminates the need for external chemical reagents. The permeate obtained through integrated membrane concentration is reused in the preparation of leaching agents, preventing the introduction of kerosene from the extraction stage into the mine and avoiding the serious environmental damage caused by kerosene returning to the mine. The rare earth concentrate produced by integrated membrane concentration is directly extracted with an extractant, eliminating the need for chemical reagents for precipitation, flocculants, or plate and frame filtration for solid-liquid separation. No acid dissolution is required before extraction, significantly shortening the mining, beneficiation, and smelting process for ion-adsorption rare earths. Attached Figure Description

[0036] Figure 1 A schematic diagram of the traditional rare earth mining, beneficiation and smelting process;

[0037] Figure 2 This is a flowchart of the short process for rare earth mining-membrane concentration-smelting of the present invention.

[0038] Figure 3 This is a schematic diagram of the multi-stage reverse osmosis membrane concentration process in this invention;

[0039] In the diagram, 1 is the nanofiltration membrane stack; 2 is the first-stage reverse osmosis membrane stack; 3 is the second-stage reverse osmosis membrane stack; 4 is the third-stage reverse osmosis membrane stack; and 5 is the fourth-stage reverse osmosis membrane stack. Detailed Implementation

[0040] like Figure 2 As shown, this invention provides a method for preparing ionic rare earth elements, specifically a short-process method for the mining, beneficiation, and smelting of ionic rare earth elements, comprising the following steps:

[0041] Step (1): The clear liquid obtained after pretreatment of the ion-type rare earth leaching mother liquor is separated into monovalent and high-valent ions to obtain permeate and intercepted liquid respectively.

[0042] In step (1), nanofiltration membranes are preferably used to separate monovalent and high-valent ions. The preferred operating pressure of the nanofiltration membrane is 0.4-1.2 MPa.

[0043] The monovalent ions are mainly monovalent Na. + Cl - Etc. High-valence ions mainly refer to divalent (M... 2+ ) or divalent or higher (R 3 + Rare earth ions. Nanofiltration membranes allow monovalent ions to pass through, but prevent divalent or higher valent ions from passing through, thus achieving the separation of monovalent and high-valent ions.

[0044] Step (2): The permeate is returned to the leaching agent preparation tank for the preparation of the leaching agent, so as to realize the full reuse of production water; the retentate is concentrated by subsequent multi-stage reverse osmosis membranes to produce rare earth concentrate for rare earth extraction.

[0045] In step (2), the multi-stage reverse osmosis membrane concentration is determined based on the concentration of rare earth ions in the retentate to ensure that each stage of the reverse osmosis membrane is in optimal operating condition. In step (2), the multi-stage reverse osmosis membrane concentration is preferably a four-stage reverse osmosis membrane concentration. The four-stage reverse osmosis membrane concentration preferably includes:

[0046] First-stage reverse osmosis membrane concentration: When the rare earth ion concentration is below 0.5 g / l, a low-pressure, high-flux reverse osmosis membrane element is used; preferably, the operating pressure of the first-stage reverse osmosis membrane concentration is 1.0-1.6 MPa.

[0047] Second-stage reverse osmosis membrane concentration: When the rare earth ion concentration is concentrated to 1.2 g / L, a medium-pressure, high-rejection-rate reverse osmosis membrane is used; preferably, the operating pressure of the second-stage reverse osmosis membrane concentration is 1.5-2.5 MPa.

[0048] Third-stage reverse osmosis membrane concentration: When the rare earth ion concentration is concentrated to 2.4 g / l, a high-pressure, high-rejection-rate reverse osmosis membrane is used; preferably, the operating pressure of the third-stage reverse osmosis membrane concentration is 2.0-4.5 MPa.

[0049] Fourth-stage reverse osmosis membrane concentration: When the rare earth ion content exceeds 4 g / L, a disc tube type ultra-high pressure reverse osmosis membrane is used; preferably, the operating pressure of the fourth-stage reverse osmosis membrane concentration is 4.0-7.5 MPa.

[0050] Step (3): Extract and back-extract the rare earth concentrate from step (2) sequentially to obtain a rare earth concentrate; preferably, in step (3), the extractant is directly added to the rare earth concentrate for separation and purification, without the need for acid dissolution. Specifically, it can be:

[0051] In step (2), the rare earth concentrate is transported to the rare earth smelter in liquid form. Extractants are added directly to the rare earth concentrate for separation and purification without the need for acid dissolution. Membrane concentrate replaces chemical precipitation, solid-liquid separation and acid dissolution processes, simplifying the process of rare earth mining, beneficiation and smelting.

[0052] like Figure 3 The diagram illustrates a specific implementation of the integrated membrane technology for separating and concentrating rare earth elements according to the present invention. Specifically, the rare earth leaching mother liquor collected from in-situ leaching at a mine is first pretreated by a gravity impurity removal system, then pumped into nanofiltration membrane stack 1. The nanofiltration permeate is returned to the leaching agent preparation, and the nanofiltration retentate (rare earth leaching solution) enters the primary reverse osmosis membrane transfer tank. The rare earth leaching solution in the transfer tank is pumped into the primary reverse osmosis membrane stack 2, and the primary reverse osmosis permeate is returned to the leaching agent preparation. The primary reverse osmosis retentate (primary concentrated rare earth) enters the secondary reverse osmosis membrane transfer tank. The primary concentrated rare earth in the transfer tank is pumped into the secondary reverse osmosis membrane stack 3, and the secondary reverse osmosis permeate is returned to the primary reverse osmosis membrane transfer tank, where it mixes with the rare earth leaching solution. The first stage reverse osmosis membrane stack is circulated, and the second stage reverse osmosis membrane retentate (second stage concentrated rare earth) enters the third stage reverse osmosis membrane transfer tank. The second stage concentrated rare earth in the transfer tank is pumped into the third stage reverse osmosis membrane stack 4. The third stage reverse osmosis membrane permeate returns to the second stage reverse osmosis membrane transfer tank and circulates back into the second stage reverse osmosis membrane stack together with the first stage concentrated rare earth. The third stage reverse osmosis membrane retentate (third stage concentrated rare earth) enters the fourth stage reverse osmosis membrane transfer tank. The third stage concentrated rare earth in the transfer tank is pumped into the fourth stage reverse osmosis membrane stack 5. The fourth stage reverse osmosis permeate returns to the third stage reverse osmosis transfer tank and circulates back into the third stage reverse osmosis membrane stack together with the second stage concentrated rare earth. The fourth stage reverse osmosis retentate returns to the fourth stage reverse osmosis transfer tank. Through continuous concentration, the fourth stage concentrated rare earth is finally obtained.

[0053] Step (4): The fourth-stage concentrated rare earth from step (3) is sent to a rare earth extraction-back-extraction system to refine ionic rare earth.

[0054] To further improve the rare earth recovery rate, in this invention, the permeate from the second-stage reverse osmosis membrane is returned to the first-stage reverse osmosis membrane for concentration.

[0055] The permeate from the third-stage reverse osmosis membrane concentration is returned to the second-stage reverse osmosis membrane concentration.

[0056] The permeate from the fourth-stage reverse osmosis membrane concentration is returned to the third-stage reverse osmosis membrane concentration.

[0057] The permeate from the first-stage reverse osmosis membrane concentration is returned to the water tank for preparing the leaching agent.

[0058] In this invention, in step (1), the pretreatment is gravity removal.

[0059] In this invention, the nanofiltration membrane and the first, second and third stage reverse osmosis membrane elements are spiral wound membrane modules; the fourth stage reverse osmosis is a disc tube (DTRO) membrane module.

[0060] Each stage of the reverse osmosis membrane concentration system of this invention is equipped with a transfer water tank. The water from the previous stage is stored in the transfer water tank, and the reverse osmosis permeate from the next stage is returned to the transfer water tank. The transfer water tank is equipped with a high-pressure pump, which is responsible for pumping the solution in the transfer water tank into the corresponding membrane treatment system. The permeate from the first stage of reverse osmosis and nanofiltration membranes is returned to the water for preparing the leaching agent.

[0061] The entire system of this invention requires no external chemical precipitant. The permeate, after concentration, is reused in the preparation of the leaching agent, preventing the kerosene from the extraction stage from entering the mine and avoiding the serious environmental damage caused by kerosene returning to the mine. The rare earth concentrate produced by reverse osmosis membrane concentration is directly extracted with an extractant without the need for chemical reagents for precipitation, flocculants, or plate and frame filtration for solid-liquid separation. No acid dissolution is required before extraction, greatly shortening the mining, beneficiation, and smelting process of ion-adsorption rare earths.

[0062] The technical solution of the present invention will be clearly and thoroughly described below with reference to specific embodiments.

[0063] Example 1

[0064] The rare earth leaching mother liquor of 0.22 g / L was separated by nanofiltration at 1.2 MPa, resulting in a rare earth concentration of 0.30 g / L. After concentration by a first-stage reverse osmosis membrane at 1.6 MPa, the rare earth concentration was further concentrated to 0.95 g / L. After concentration by a second-stage reverse osmosis membrane at 1.5 MPa, the rare earth concentration was further concentrated to 2.36 g / L. After concentration by a third-stage reverse osmosis membrane at 3.5 MPa, the rare earth concentration was further concentrated to 5.24 g / L. After concentration by a disc-tube ultra-high pressure reverse osmosis membrane at 7.5 MPa, the rare earth concentration was further concentrated to 12.31 g / L. After extraction with an extractant, the rare earth concentration in the back-extraction solution reached 125 g / L, the rare earth concentration in the nanofiltration permeate was less than 0.0025 mg / L, and the rare earth concentration in the first-stage reverse osmosis membrane permeate was less than 0.0003 mg / L. The theoretical recovery rate of rare earth reached 99.3%.

[0065] Example 2

[0066] The rare earth leaching mother liquor of 0.18 g / L was separated by nanofiltration at 0.8 MPa, resulting in a rare earth concentration of 0.27 g / L. After concentration by a first-stage reverse osmosis membrane at 1.0 MPa, the rare earth concentration was further concentrated to 1.05 g / L. After concentration by a second-stage reverse osmosis membrane at 2.5 MPa, the rare earth concentration was further concentrated to 2.25 g / L. After concentration by a third-stage reverse osmosis membrane at 2.0 MPa, the rare earth concentration was further concentrated to 4.62 g / L. After concentration by a disc-tube ultra-high pressure reverse osmosis membrane at 4.0 MPa, the rare earth concentration was further concentrated to 11.05 g / L. After extraction with an extractant, the rare earth concentration in the back-extraction solution reached 105 g / L, the rare earth concentration in the nanofiltration permeate was less than 0.004 mg / L, and the rare earth concentration in the first-stage reverse osmosis membrane permeate was less than 0.0001 mg / L. The theoretical recovery rate of rare earth reached 99.4%.

[0067] Example 3

[0068] The rare earth leaching mother liquor of 0.12 g / L was separated by nanofiltration at 0.4 MPa, resulting in a rare earth concentration of 0.21 g / L. After concentration by a first-stage reverse osmosis membrane at 1.2 MPa, the rare earth concentration was concentrated to 1.14 g / L. After concentration by a second-stage reverse osmosis membrane at 2.0 MPa, the rare earth concentration was concentrated to 2.12 g / L. After concentration by a third-stage reverse osmosis membrane at 4.5 MPa, the rare earth concentration was concentrated to 4.37 g / L. After concentration by a disc-tube ultra-high pressure reverse osmosis membrane at 6.0 MPa, the rare earth concentration was concentrated to 11.09 g / L. After extraction with an extractant, the rare earth concentration in the back-extraction solution reached 116 g / L, the rare earth concentration in the nanofiltration permeate was less than 0.0035 mg / L, and the rare earth concentration in the first-stage reverse osmosis membrane permeate was less than 0.0002 mg / L. The theoretical recovery rate of rare earth reached 99.5%.

[0069] Comparative Example 1

[0070] Adopting such Figure 1 The existing technology shown requires the addition of 0.122 g / g rare earth carbonate to the 0.22 g / L rare earth leaching mother liquor for chemical purification, 0.006 g / g sulfuric acid to the purified residue, and 0.752 g / g rare earth carbonate to the chemical precipitation. The rare earth content in the supernatant of the chemical precipitation is 0.02 g / L, requiring 0.008 g / g rare earth flocculant. The theoretical recovery rate of rare earth is only 84.6%.

[0071] Comparative Example 2

[0072] Adopting such Figure 1The existing technology shown requires the addition of 0.098 g / g rare earth carbonate to the 0.18 g / L rare earth leaching mother liquor for chemical purification, 0.005 g / g sulfuric acid to the purified residue, and 0.615 g / g rare earth carbonate to the chemical precipitation. The rare earth content in the supernatant of the chemical precipitation is 0.03 g / L, requiring 0.007 g / g rare earth flocculant. The theoretical recovery rate of rare earth is 85.4%.

[0073] Comparative Example 3

[0074] Adopting such Figure 1 The existing technology shown requires the addition of 0.067 g / g rare earth carbonate to the 0.12 g / L rare earth leaching mother liquor for chemical purification, 0.003 g / g concentrated sulfuric acid to the purified residue, and 0.410 g / g rare earth carbonate to the chemical precipitation. The rare earth content in the supernatant of the chemical precipitation is 0.02 g / L, requiring 0.004 g / g rare earth flocculant. The theoretical recovery rate of rare earth is 82.7%.

[0075] By comparing Examples 1-3 and Comparative Examples 1-3, the new process eliminates the need for chemical impurity removers, chemical precipitants, sulfuric acid, and flocculants; it eliminates the need for chemical precipitation tanks and plate and frame filtration equipment; the rare earth content in both the nanofiltration membrane permeate and the first-stage reverse osmosis permeate is below 0.0003 mg / L, and the lost trace rare earths are returned to the mine in ionic form through the leaching agent and can be re-leached; the overall rare earth recovery rate in the rare earth mother liquor obtained from the single leaching is higher than 99.3%, far exceeding the theoretical recovery rate of the traditional process. The newly invented process flow is significantly shorter than the traditional process, reducing raw material consumption, cutting infrastructure investment, saving labor, and greatly improving the rare earth recovery rate.

Claims

1. A method for producing an ionic rare earth, characterized by, It comprises the following steps: Step (1), the clear solution obtained after the pre-treatment of the ion type rare earth leaching mother liquor is separated into monovalent and high valence ions, and the permeate and the intercept liquid are obtained respectively; Step (2), the permeate returns to the leaching agent water pool for the preparation of leaching agent to realize the full reuse of production water; the intercept liquid is concentrated by subsequent multi-stage reverse osmosis membrane to obtain rare earth concentrated liquid, which is directly subjected to rare earth extraction; Step (3), the rare earth concentrated liquid in step (2) is subjected to extraction and back extraction in sequence to obtain rare earth concentrated solution; Step (4), the rare earth concentrated solution in step (3) is refined to obtain ion type rare earth; In step (2), the multi-stage reverse osmosis membrane concentration is determined according to the concentration of rare earth ions in the intercept liquid; In step (2), the multi-stage reverse osmosis membrane concentration is four-stage reverse osmosis membrane concentration; The four-stage reverse osmosis membrane concentration comprises: First-stage reverse osmosis membrane concentration: when the concentration of rare earth ions is lower than 0.5 g / l, a low-pressure large-flux reverse osmosis membrane element is adopted; Second-stage reverse osmosis membrane concentration: when the concentration of rare earth ions is concentrated to 1.2 g / l, a medium-pressure high-rejection-rate reverse osmosis membrane is adopted; Third-stage reverse osmosis membrane concentration: when the concentration of rare earth ions is concentrated to 2.4 g / l, a high-pressure high-rejection-rate reverse osmosis membrane is adopted; Fourth-stage reverse osmosis membrane concentration: when the content of rare earth ions exceeds 4 g / l, a disc-tube ultra-high-pressure reverse osmosis membrane is adopted; In step (1), a nanofiltration membrane is adopted for the separation of monovalent and high valence ions.

2. The method for preparing ionic rare earth elements according to claim 1, characterized in that, The operation pressure of the first-stage reverse osmosis membrane concentration is 1.0-1.6 MPa; The operation pressure of the second-stage reverse osmosis membrane concentration is 1.5-2.5 MPa; The operation pressure of the third-stage reverse osmosis membrane concentration is 2.0-4.5 MPa; The operation pressure of the fourth-stage reverse osmosis membrane concentration is 4.0-7.5 MPa.

3. The method for preparing ionic rare earth elements according to claim 2, characterized in that, The water produced by the second-stage reverse osmosis membrane concentration returns to the first-stage reverse osmosis membrane concentration; The water produced by the third-stage reverse osmosis membrane concentration returns to the second-stage reverse osmosis membrane concentration; The water produced by the fourth-stage reverse osmosis membrane concentration returns to the third-stage reverse osmosis membrane concentration; The water produced by the first-stage reverse osmosis membrane concentration returns to the leaching agent water pool.

4. The method for preparing ionic rare earth elements according to claim 1, characterized in that, The operation pressure of the nanofiltration membrane is 0.4-1.2 MPa.

5. The method for preparing ionic rare earth elements according to claim 1, characterized in that, In step (3), the extractant is directly added to the rare earth concentrated liquid for separation and purification without adding acid for dissolution.

6. The method of claim 1-5, wherein the method is characterized by, In step (1), the pre-treatment is gravity removal.

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