阅读说明：本技术 一种实现碳酸氢镁循环利用的稀土萃取方法 (Rare earth extraction method for realizing recycling of magnesium bicarbonate ) 是由 孙旭 刘向生 魏煜青 冯宗玉 黄小卫 彭新林 徐旸 王猛 夏超 于 2019-01-17 设计创作，主要内容包括：本发明属于稀土冶炼分离技术领域,具体涉及一种实现碳酸氢镁循环利用的稀土萃取方法。本发明所述稀土萃取方法,使用碳酸氢镁皂化酸性萃取剂有机相,同时回收皂化过程中的皂化废水和CO<Sub>2</Sub>,而得到的镁皂有机相则与稀土料液进行稀土皂化处理,实现稀土的萃取而制得稀土产品,而稀土皂化过程中产生的氯化镁废水则通过加入皂化废水和胺类萃取剂混合,并利用回收的CO<Sub>2</Sub>进行萃取-碳化反应,将氯化镁转化为碳酸氢镁,可循环用于酸性萃取剂的皂化过程,实现了镁盐的闭路循环利用,大大降低了稀土萃取过程中盐的排放,具有显著的环境效益。(The invention belongs to the technical field of rare earth smelting and separation, and particularly relates to a rare earth extraction method for realizing recycling of magnesium bicarbonate. The rare earth extraction method of the invention uses magnesium bicarbonate to saponify the acidic extractant organic phase, and simultaneously recovers the saponification wastewater and CO in the saponification process 2 The obtained magnesium soap organic phase and rare earth feed liquid are subjected to rare earth saponification treatment to realize extraction of rare earth and prepare rare earth products, and magnesium chloride wastewater generated in the rare earth saponification process is mixed by adding saponification wastewater and amine extractant and utilizing recovered CO 2 The extraction-carbonization reaction is carried out to convert the magnesium chloride into the magnesium bicarbonate which can be recycled in the saponification process of the acidic extractant, thereby realizing the closed cycle utilization of the magnesium salt, greatly reducing the salt discharge in the rare earth extraction process and having obvious environmental benefit。)

1. The rare earth extraction method for realizing recycling of magnesium bicarbonate is characterized in that magnesium chloride wastewater recovered in the rare earth soap process is mixed with organic amine extractant and recovered CO₂The preparation method of the magnesium bicarbonate solution through extraction-carbonization comprises the following steps:

(1) mixing acidic extractant with magnesium bicarbonate solution for saponification, and recovering CO generated in saponification process₂And saponifying the waste water for later use;

(2) uniformly mixing the saponified extractant and rare earth feed liquid to perform rare earth soap reaction, and performing extraction separation to obtain magnesium chloride wastewater and required rare earth products respectively;

(3) adding the saponification wastewater collected in the step (1) into the magnesium chloride wastewater collected in the step (2) for dilution, adding an amine extractant for uniformly mixing, and then introducing CO generated in the step (1)₂Carrying out carbonization reaction on the gas;

(4) and (3) after the carbonization is finished, clarifying and phase splitting the reaction liquid, wherein the obtained organic phase is an extract compound containing the amine extractant and hydrochloric acid, and the obtained water phase is the required magnesium bicarbonate solution and is circularly used for the saponification reaction in the step (1).

2. The rare earth extraction method for realizing recycling of magnesium bicarbonate according to claim 1, wherein in the step (1), the acidic extractant comprises one or more of P507, P204, P229 and HBTBPP.

3. The rare earth extraction method for realizing the recycling of the magnesium bicarbonate according to the claim 1 or 2, characterized in that in the step (1), the concentration of the magnesium bicarbonate solution is 0.01-0.5 mol/L.

4. The rare earth extraction method for realizing the recycling of the magnesium bicarbonate according to any one of claims 1 to 3, wherein in the step (1), the dosage ratio of the acidic extracting agent to the magnesium bicarbonate solution is 0.2: 1-2: 1.

5. the method for extracting rare earth for recycling magnesium bicarbonate according to any one of claims 1 to 4, wherein in the step (2), the concentration of the rare earth feed liquid is 0.5-2 mol/L, and the volume ratio of the saponified extractant to the rare earth feed liquid is 3: 1-15: 1.

6. The rare earth extraction method for realizing the recycling of the magnesium bicarbonate according to any one of claims 1 to 5, characterized in that the step (2) further comprises the step of adjusting the concentration of the magnesium chloride wastewater to be 0.1 to 5 mol/L, and/or the step of adjusting the pH of the magnesium chloride wastewater to be 2 to 7.

7. The rare earth extraction method for realizing the recycling of magnesium bicarbonate according to any one of claims 1 to 6, wherein in the step (3), the volume ratio of the saponified wastewater for dilution to the magnesium chloride wastewater is 5: 1-20: 1.

8. the rare earth extraction method for realizing recycling of magnesium bicarbonate according to any one of claims 1-7, wherein in the step (3):

the amine extractant comprises primary amine, secondary amine or tertiary amine organic amine extractant dissolved in diluent;

the diluent comprises benzene, monohydric alcohol, polyhydric alcohol or kerosene;

the volume ratio of the amine extractant to the diluent is 0.2: 1-2: 1.

9. the rare earth extraction method for realizing the recycling of the magnesium bicarbonate according to any one of claims 1 to 8, wherein in the step (3), the volume ratio of the magnesium chloride wastewater diluted by the saponified wastewater to the amine extractant is 0.2: 1-5: 1, control of CO introduced₂The purity is 30-100%, and the carbonization time is 5-300 min.

10. The rare earth extraction method for realizing the recycling of the magnesium bicarbonate according to claim 8, wherein the step (4) further comprises the step of adding pure water or the saponification wastewater into the separated organic phase for mixed back extraction; the phase ratio of the organic phase to the pure water or the saponified wastewater was 0.5: 1-5: 1, the time of the mixed back extraction is 1-60 min.

Technical Field

The invention belongs to the technical field of rare earth smelting and separation, and particularly relates to a rare earth extraction method for realizing recycling of magnesium bicarbonate.

Background

Rare earth is a general term for 17 elements of lanthanum, cerium, praseodymium, neodymium, promethium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, lutetium 15 lanthanoid elements of the third subgroup of the 6 th period of the periodic table of elements and yttrium and scandium of the same group. The rare earth element has various excellent special physical and chemical properties such as magnetism, light, electricity and the like due to the unique electronic layer structure, and the rare earth material is a strategic material which is indispensable or substituted for developing high-precision industries of various countries in the world at present and plays a vital role in improving the traditional industry, is known as vitamins of the modern industry and a new material treasury, and has very wide market prospect and strategic significance.

At present, the separation and purification of rare earth elements mainly adopts an extraction separation technology, the used extractant is mainly acidic extractants such as P507, P204 and the like, the extraction capacity of rare earth is inversely proportional to the third time of water phase equilibrium acidity, in order to improve the production efficiency of rare earth separation, the extractant is firstly saponified by ammonia water or liquid alkali, then the prepared saponified extractant is subjected to extraction reaction with a rare earth solution to generate a rare earth-containing loaded organic phase and an ammonia (sodium) salt solution, the obtained rare earth-containing loaded organic phase is used for the serial extraction separation of rare earth, then a high-purity single rare earth solution is obtained by acid back extraction, and then a rare earth compound product is prepared by ammonium bicarbonate or sodium carbonate and oxalic acid precipitation.

However, the extraction agent saponified with ammonia water or liquid alkali used in the prior art can generate a large amount of ammonia (sodium) salt wastewater in the extraction process. According to statistics, for every 1 ton of rare earth oxide is completely separated, at least about 1 ton of liquid ammonia or 6-8 tons of liquid alkali are used, and more than ten tons of ammonia (sodium) -containing wastewater are discharged. For a large amount of generated ammonia (sodium) -containing wastewater, at present, no efficient treatment method exists, and only an evaporative crystallization process with extremely high energy consumption can be generally adopted for treatment, but the treatment process is high in cost and cannot be borne by most enterprises. Moreover, a large amount of saponification wastewater is generated in the rare earth extraction separation process, high treatment cost is required for enterprises, and serious pollution is caused to the ecological environment due to discharge, so that an environment-friendly saponification and rare earth extraction process is required to be developed.

The magnesium bicarbonate is an excellent acid balancing agent in the saponification process of the acidic extracting agent, has low impurity content of Fe, Al and the like, can react with the acidic extracting agent and does not generate a three-phase substance, and therefore, has wide application prospect in the rare earth extraction process. During the process of saponifying the acidic extractant with magnesium bicarbonate, magnesium ions exchange with hydrogen ions in the organic phase, and the hydrogen ions promote the hydrolysis of the magnesium bicarbonate to produce CO₂And water. And (3) carrying out a rare earth soap process on the magnesium soap organic phase and the rare earth feed liquid, and exchanging magnesium ions with the rare earth ions to obtain the magnesium chloride wastewater. For example, chinese patent CN103382034A discloses a method for extracting agent saponification and rare earth extraction by using magnesium bicarbonate, in the process, magnesite, dolomite or magnesium carbonate is used as raw material after roasting and digestion, and MgCl generated in the saponification process is treated₂Preparing Mg (OH) from waste water through alkali conversion reaction₂And then with CO recovered during saponification₂Preparation of Mg (HCO) by carbonization₃)₂The solution was used for saponification extraction. But the process is for MgCl₂The recycling step of the wastewater needs to adopt caustic soda conversion of light-burned dolomite slurry to obtain Mg (OH)₂And CaCl₂Consumption of light burned dolomite for Mg (HCO)₃)₂Is supplied cyclically with CaCl₂And also needs to be recycled in a certain way.

Disclosure of Invention

Therefore, the invention aims to provide a rare earth extraction method for realizing recycling of magnesium bicarbonate so as to solve the problem of difficulty in wastewater treatment in the rare earth extraction process in the prior art.

In order to solve the technical problem, the rare earth extraction method for recycling the magnesium bicarbonate is characterized in that magnesium chloride wastewater recovered in the rare earth soap process is mixed with an organic amine extractant and recovered CO₂The preparation method of the magnesium bicarbonate solution through extraction-carbonization comprises the following steps:

(1) mixing acidic extractant with magnesium bicarbonate solution for saponification, and recovering CO generated in saponification process₂And saponifying the waste water for later use;

(2) uniformly mixing the saponified extractant and rare earth feed liquid to perform rare earth soap reaction, and performing extraction separation to obtain magnesium chloride wastewater and required rare earth products respectively;

(3) adding the saponification wastewater collected in the step (1) into the magnesium chloride wastewater collected in the step (2) for dilution, adding an amine extractant for uniformly mixing, and then introducing CO generated in the step (1)₂Carrying out carbonization reaction on the gas;

(4) and (3) after the carbonization is finished, clarifying and phase splitting the reaction liquid, wherein the obtained organic phase is an extract compound containing the amine extractant and hydrochloric acid, and the obtained water phase is the required magnesium bicarbonate solution and is circularly used for the saponification reaction in the step (1).

In the step (1), the acidic extractant includes one or more of P507 (2-ethylhexyl phosphate mono 2-ethylhexyl ester), P204(HDEHP), P229 (di (2-ethylhexyl) phosphonic acid, H [ DEHP ]), hbtpmp (di (2,4, 4-trimethylpentyl) phosphonic acid).

In the step (1), the concentration of the magnesium bicarbonate solution is 0.01-0.5 mol/L, preferably 0.05-0.25 mol/L.

In the step (1), the dosage ratio of the acidic extracting agent to the magnesium bicarbonate solution is 0.2: 1-2: 1, preferably 0.5: 1-1.2: 1.

the main reaction process of saponifying the organic phase with magnesium bicarbonate is shown in the following formula, and the saponification process produces H₂O and CO₂And respectively recovering:

Mg(HCO₃)₂(aq)+(HL)₂(o)→Mg(HL)₂(o)+H₂O+2CO₂(g)。

in the step (2), the concentration of the rare earth feed liquid is 0.5-2 mol/L, and the volume ratio of the saponified extractant to the rare earth feed liquid is 3: 1-15: 1.

In the rare earth soap process, the main reaction process is as follows, the rare earth soap process generates magnesium chloride wastewater, and the magnesium chloride wastewater is recovered for subsequent steps:

3Mg(HL)₂(o)+2RECl₃(aq)→3MgCl₂(aq)+2RE₂(HL)₃(o)。

in the step (2), the concentration of the magnesium chloride wastewater is adjusted to be 0.1-5 mol/L, and/or the pH of the magnesium chloride wastewater is adjusted to be 2-7.

In the step (3), the volume ratio of the saponified wastewater for dilution to the magnesium chloride wastewater is 5: 1-20: 1, preferably 7: 1-15: 1. because the magnesium chloride concentration obtained in the rare earth soap process is too high, the solubility of the magnesium bicarbonate solution is limited, and the highest magnesium bicarbonate concentration can only reach about 0.4 mol/L, the magnesium chloride wastewater needs to be diluted, and a certain degree of dilution is helpful for converting the magnesium chloride into the magnesium bicarbonate solution.

In the step (3):

the amine extractant comprises primary amine, secondary amine or tertiary amine organic amine extractant dissolved in diluent; the amine extractant is preferably N235, N263 and the like;

the diluent comprises benzene, monohydric alcohol, polyhydric alcohol or kerosene; the diluents are preferably mixed in equal amounts;

the main function of the amine extractant is to extract acidic substances in the presence of MgCl₂、CO₂And amine-based extractants, the following reactions occur:

CO₂(g)+H₂O→H₂CO₃；

H₂CO₃→HCO₃ ^-+2H⁺；

N₃R(o)+H⁺→N₃R·H⁺(o)；

Mg²⁺+2HCO₃→Mg(HCO₃)₂。

in this reaction system, it is first necessary to have sufficient CO₂Partial pressure of CO₂And H₂The carbonation of O is carried out sufficiently. Secondly, the key to the reaction is Mg²⁺+2HCO₃→Mg(HCO₃)₂The pH value of the process can effectively promote H when the pH value of the reaction system is more than 5₂CO₃Hydrolysis to HCO₃ ^-Further promote the reaction with Mg²⁺With HCO₃Formation of Mg (HCO)₃)₂The forward reaction of (2) and under the condition of proper concentration, the high-efficiency synthesis of magnesium bicarbonate solution.

The volume ratio of the amine extractant to the diluent is 0.2: 1-2: 1, preferably 0.5: 1-1.5: 1.

in the step (3), the volume ratio of the magnesium chloride wastewater diluted by the saponification wastewater to the amine extractant is 0.2: 1-5: 1, control of CO introduced₂The purity is 30-100%, and the carbonization time is 5-300min, preferably 20-80 min. Higher CO₂The purity can ensure that the system has enough CO₂Partial pressure, promoting the forward direction of the reaction.

In the step (4), a step of adding pure water or the saponification wastewater into the separated organic phase to perform mixed back extraction is further included; the phase ratio of the organic phase to the pure water or the saponified wastewater was 0.5: 1-5: 1, the time of the mixed back extraction is 1-60 min.

The rare earth extraction method for realizing the recycling of the magnesium bicarbonate uses the organic phase of the acidic extractant saponified by the magnesium bicarbonate and simultaneously recovers the saponified wastewater and CO in the saponification process₂The obtained magnesium soap organic phase and rare earth feed liquid are subjected to rare earth saponification treatment to realize extraction of rare earth and prepare rare earth products, and magnesium chloride wastewater generated in the rare earth saponification process is added with saponification wastewater and aminesMixing and coarse extracting with extractant, and utilizing recovered CO₂Carbonizing to convert magnesium chloride into magnesium bicarbonate for reuse in the saponification of acid extractant, and further back extracting the extracted hydrochloric acid with water or saponified waste water to obtain hydrochloric acid capable of being recovered. In the whole rare earth extraction process, the saponification wastewater and the magnesium chloride wastewater generated in each step can be recycled and then used for carbonizing and synthesizing magnesium bicarbonate, so that the closed cycle utilization of magnesium salts is realized, new other pollution is not introduced, only hydrochloric acid capable of being effectively utilized is generated, the salt discharge in the rare earth extraction process is greatly reduced, and the method has remarkable environmental benefits.

The rare earth extraction method for realizing the recycling of the magnesium bicarbonate can extract H by using the amine extractant⁺The method is characterized in that the method comprises the steps of firstly diluting magnesium chloride wastewater by using saponified wastewater, mixing the magnesium chloride wastewater with an amine extractant, and simultaneously introducing CO₂Performing carbonization reaction, because the amine extractant can extract H⁺The hydrochloric acid as a product enters the organic phase during the reaction, thereby inhibiting MgCl₂-CO₂The pH of the reaction water phase system is reduced, and the magnesium chloride and CO are promoted₂The carbonization reaction proceeds in the forward direction, so that magnesium chloride and CO are reacted₂The reaction generates magnesium bicarbonate solution, has higher reaction yield and further improves the efficiency of the whole process.

Drawings

In order that the present disclosure may be more readily and clearly understood, the following detailed description of the present disclosure is provided in connection with specific embodiments thereof and the accompanying drawings, in which,

FIG. 1 is a flow diagram of a rare earth extraction process of the present invention.

Detailed Description

In the rare earth extraction method related in the following examples of the present invention, the saponified wastewater of the acidic catalyst refers to the reaction of a magnesium bicarbonate solution with an acidic extractant, magnesium ions exchange with hydrogen ions in an organic phase, and the hydrolysis of the hydrogen bicarbonate generates CO₂Then obtaining the saponified wastewater.