AU2015319798B2

AU2015319798B2 - A method of enriching rare earth by priority leaching and removing phosphorus and calcium from REE-bearing phosphorus ores

Info

Publication number: AU2015319798B2
Application number: AU2015319798A
Authority: AU
Inventors: Yanqing FAN; Linyong FENG; Kaixi JIANG; Wei Jiang; Xunxiong JIANG; Jiangshun LIN; Wei Liu; Shengdong WANG; Yinan Yin; Denggao ZHANG; Lei Zhao
Original assignee: Beijing General Research Institute of Mining and Metallurgy
Current assignee: Beijing General Research Institute of Mining and Metallurgy
Priority date: 2014-09-30
Filing date: 2015-03-13
Publication date: 2017-08-31
Anticipated expiration: 2035-03-13
Also published as: CN105525092A; CN105525092B; AU2015319798A1; WO2016050036A1

Abstract

Abstract A rare earth enrichment method by priority leaching and removing phosphorus and calcium from REE-bearing phosphorus ores, is to mix REE-bearing phosphorus ores with recycled phosphorus acid solution with 15wt%-55wt% of P20 5 , 2-25 g/L Ca 2+, and 5wt%-45wt% available P20 5 at the solid-liquid ratio of 1:2-10, to stir the mixture to activate its reaction at the temperature of 20'C-70'C for 0.5-4 hours, and age 1- 5 hours to gain rare earth enrichment residue and lixivium by solid-liquid separation. Mix the gained lixivium with sulfuric acid and appropriate amounts of gypsum residue, where the molar quantity of added sulfuric acid is about 0.7-1 times of calcium molar quantity in the lixivium, and the added amount of gypsum residue is 10%-100% of the mass of REE-bearing phosphorus ores. Through reaction and filtering, get regenerated phosphorus acid and gypsum residue, part of which need to be washed and added water properly for mixture, back used as recycled phosphorus acid.

Description

A Method of Enriching Rare Earth by Priority Leaching and Removing Phosphorus and Calcium from REE-bearing Phosphorus Ores

It is hereby to apply to enjoy the rights of priority for Chinese Patent Applications No. 201410523267.9 submitted on Sep. 30, 2014.

FIELD OF THE INVENTION

The invention is a part of the enrichment and comprehensive recovery of the associated rare earth, particularly involving a method to remove phosphorus and calcium and enrich rare earth by priority leaching in the mixed solution of phosphoric acid and mono-calcium phosphate from the phosphorus ore with rare earth.

BACKGROUND OF THE INVENTION

There are three types of rare earth resources: (1) independent rare earth ores, such as monazite, bastnaesite, and xenotime etc.; (2) ion-type rare earth ores adsorbing on the mineral grain surface or layers in the ionic form; (3) other mineral ores with associated rare earth ores in the form of isomorphism replacement, such as apatite and other ores. Nowadays, rare earth minerals worldwide are mainly from the first two resources, while few associated rare earth ores are developed and utilized.

Basically, rare earths are generally associated to phosphoms ore with different content ratio ranging from 0.1% or so to over 5% at best. Since the rare earth adsorbs to phosphate minerals in apatite ores in the form of isomorphism replacement, physical concentration is not effective in the enrichment of rare earth. Direct leaching of rare earth is of great difficulty and high cost to recover rare earth in that it is a type of low-grade ore with high content of deleterious phosphorus as impurity and calcium. Sulfuric acid method is the basic method adopted for the wet-process phosphoric acid production in the world at present. In the acidolysis process by sulfuric acid in the above method, a large amount of phosphor-gypsum - featuring by strong adsorption to rare earth - are generated, making it hard for rare earth to be leached in the process. US4636369 revaled that bring in aluminum ions, iron ions, silicon ions or theirs mixes in the wet-process phosphoric acid slurry, to increase the solubility of rare earth in the solution, with 56% of rare earth leaching rate. As stated in China’s patent No. 200710178377.6, organic ornonorganic surfactants are added in the process of sulfuric acid decomposing phosphorus ore, which is able to leach 80% of rare earth by changing crystal form of phosphor-gypsum to decrease the adsorption of rare earth. Whereas, in the China’s patent No. 201010217142.5, a method for leaching the rare earth by phosphoric acid is stated. Namely, the phosphorite with rare earth can be leached by phosphorus ore above 65°C, where about 90% of rare earth can be leached. Although the methods above are able to leach rare earth with high efficiency, they still have difficulties to further recover rare earth from solutions, because lixivium with rare earth contains phosphate acid in high concentration and even a large amount of impurities, including calcium.

For these reasons, pre-impregnation process plays a key role in comprehensive recovery associated rare 1 earth from phosphorus ore, by removing impurities of phosphorus, calcium, iron and aluminum in the phosphorus ore beforehand to increase the enrichment ratio of rare earth.

Nitric acid and hydrochloric acid have a strong ability to dissolve phosphorus and calcium in phosphorite, yet dissolve out most rare earth as well, making it harder to enrich rare earth with the lixivium mixed with phosphate and nitrate or chloride, and unfavorable to the production of phosphoric acid or phosphorous fertilizers. Although sulfuric acid also has strong dissolving capacity of phosphorus in the phosphorite, and phosphoms, iron, aluminum and rare earth in sulfuric solutions are leached into the solutions, all calcium transforms into gypsum remaining in slags, while gypsum has a strong adsorption effect on rare earth, causing the leached rare earth is recaptured into slags. In the process of sulfuric acid acidulating phosphorite, a large quantity of phosphor-gypsum are produced, about 1.5 tons of phosphor-gypsum out of 1 ton of phosphorus ore in the sulfuric leaching process. Thereby, rare earth cannot be well pre-enriched, as it has an even lower grade in the slags of phosphor-gypsum than those in phosphorus ore.

In the traditional wet-process phosphoric acid production, acidulation of phosphorus ore is normally developed in large amount of phosphoric acid solution medium. Thereby, the whole dissolving process can be divided into two steps: first, phosphorus ore and phosphoms acid or that returned to the system can react in the temperature of 60 - 100 °C, where phosphoms and calcium are removed from phosphoms ore by reacting with phosphoms acid to generate mono-calcium phosphate [Ca(H2P04)2] with water solubility. Due to excessive phosphoms acid, rare earth ions and phosphoms acid radical ions (P043) complex into solvable negative anions [RE(P04)2]3 to leach large quantities of rare earth into solution with the rare earth leaching rate over 50%; second, when mono-calcium phosphate reacts with excessive sulfuric acid, mono-calcium phosphate is transformed into phosphoms acid, and gypsums are dissolved out, causing the loss of rare earth leached in the first step, which is adsorbed into slags again. Apart from rare earth leaching into solutions, as the high reaction temperature in the first step, fluorine in the phosphoms ore is transferred to hydrogen fluoride, which will react with aluminosilicate in phosphoms ore, affecting the subsequent separation, by leading a great deal of aluminum and silicon to the solutions again.

Ca5F(P04)3 + 7H3P04 = 5Ca(H2P04)2 + HF| 3H2S04+6HF+Si02Al203 = H2SiF6+Al2(S04)3+5H20 Ca(H2P04)2 + H2S04 = CaS04|+2H3P04 A method of extracting rare earth from phosphoms ores published in EP 0522234A1 is that recovery the REE-bearing phosphoms ores on the basis of the wet-process phosphoms acid production. In the process, mix excess phosphoms acid of three times of volume with phosphoms concentrates with rare earth, dissolve phosphoms ores by heating the mixture to 60 - 110°C, classify the sedimentation of reacted ore pulp, and then get calcium-bearing coarse-grained slags and REE-bearing fine-graded rare-earth residues. As the leaching under the high temperature of 60 - 110°C, a large quantity of rare earth is dissolved into solution at the dissolution rate of 30% - 40%, while 20% - 50% rare earth is dissolved into coarse-grained slags, leading the separation of rare earth with low recovery rate, only about 20% - 50%. However, in China’s Patent No. 201110143415.0, another method of separating rare earth from phosphoms ores is to leach the phosphoms ores with excess phosphoms acid. Make full use of the advantage properties of 2 fluorine in the phosphorus ores to generate fluoride that rare earth is hard to dissolved into, then rare earth is enriched in leaching slags while phosphorus in the form of mono-calcium phosphate is dissolved into solutions.

All in all, due to low-grade rare earth in the phosphoms ores and high-content phosphorus, calcium, iron, and aluminum affecting rare earth separation and recovery, a chemical impurity removing method will improve rare earth enrichment ratio, rather than an expensive direct-leaching method to recover rare earth with great difficulties. The key to improve rare earth enrichment ratio is to pre-remove impurities of phosphorus, calcium, iron, and aluminum from REE-bearing phosphorus ores without affecting the production of phosphorus products based on the production process of phosphorus acid and fertilizers. Although phosphorus acid leached has a good effect on leaching phosphoms and calcium in phosphorite, phosphoms acid is well able to leaching out iron, aluminum and magnesium with a great excess coefficient, and even part of rare earth under a certain condition. As for a high cost, phosphoms acid has to be repeatedly used by regeneration in the production process; otherwise the process will go with a high cost. The dissolution of iron, aluminum, and magnesium will affect the regeneration of phosphoms acid. When iron, aluminum, and magnesium reach a certain concentration in the system, even to hardly regenerate and reuse phosphoms acid. The dissolution of rare earth leads to the dispersing and loss of rare earth. Thereby, the key to enrich rare earth through pre-impregnation by phosphoric acid method is to reduce the dissolution of iron, aluminum, magnesium, and rare earth by decreasing the excess coefficient of phosphoms acid.

Summary of the Invention

With regards to the deficiencies of the existing technologies, the invention aims to provide a method to remove phosphoms and calcium and enrich rare earth by priority leaching in the mixed solution of phosphoric acid and mono-calcium phosphate from phosphoms ore with rare earth. Specifically, given the large excess coefficient of phosphoms acid, high dissolution rate of rare earth, and a plenty of impurities such as iron, aluminum, and magnesium affecting the regeneration and reuse of phosphoms acid when pre-leaching REE-bearing phosphoms ores in phosphoms acid, control the content of calcium in the ore pulp during phosphoms acid regeneration and leaching, to generate a small amount of nano mono-calcium phosphate particles, separate and recover the associated rare earth in the phosphoms ores with nanoparticles as its carriers. Meanwhile control the dissolution of impurities of iron, aluminum, and magnesium in phosphoms ores by controlling the concentration of calcium to reduce the excess coefficient of phosphoms acid and then decrease effective P2Os The specific technical proposal is to control the reaction conditions to maintain calcium concentration at a certain level in the solution in the regeneration and reuse process of phosphoms acid. That is, to obtain the mixed solution of phosphoms acid and mono-calcium phosphate, then in the leaching phase, adopt low-temperature (20°C - 60°C) reaction of the mixed solution and phosphoms ores, to generate few 200-nanometer calcium hydro-phosphate particles, accounting for 0.05% - 2% of leaching residue weight. Then maintain rare earth in the residue based on the strong adsorption and eutectic effects of nano-scale calcium hydro-phosphate particles in the ore pulp on the rare earth, and meanwhile, the mixed solution has a small impact on the regeneration and reuse process of phosphoms acid 3 due to small excess coefficient of phosphorus acid in the mixed solution, low available phosphorus acid concentration, and low dissolution ratio of iron, aluminum, magnesium and other impunities in phosphorus ores.

The purpose of the present invention is implemented through the following technical planning.

The invention is adopted to provide a method to remove phosphorus and calcium and enrich rare earth by priority leaching in the mixed solution of phosphoric acid and mono-calcium phosphate from phosphorus ore with rare earth. The method encompasses the steps as below: (1) The REE-bearing phosphorus ores react with recycling leaching agent, at the temperature of 20 °C -70 °C, with the priority of 30 °C-50 °C; (2) Transfer the ore pulp prepared in Step (1) into an agitation tank for aging for 1-5 hours; (3) Conduct the ore pulp in Step (2) with a solid-liquid separation process, and get rare earth enrichment residue and lixivium; (4) Mix the lixivium in Step (3) and sulfuric acid and gypsum, where the molar quantity of added sulfuric acid is about 0.7-1 times of calcium molar quantity in the lixivium, and the quantity of added gypsum residue is 10%-100% of the mass of REE-bearing phosphorus ores; (5) Conduct the ore pulp in Step (4) with a solid-liquid separation process, and get regenerated phosphorus acid and gypsum residue, which need to be washed and added water properly for mixture, back to Step (1) used as recycled phosphorus acid.

In the method aforesaid, the recycled leaching agent in Step (1) is the mixed solution of phosphorus acid and mono-calcium phosphate, and its total P205 mass concentration is about 15%-55%, with the priority of 20%-35%. The Ca2+ concentration is 2-25 g/L, with the priority of 5-15 g/L, and the available P2O5 concentration is at 5wt%-45wt%; the mass and volume ratio of phosphorus concentrate with rare earth and recycled phosphorus acid is 1:2-10, with the priority of 1:4-8; the reaction time takes 0.5-4 hours, with the priority of 1-3 hours.

In the method aforesaid, with regards to the ageing process in Step (2), appropriate amount of rare earth enrichment residue got in Step (3), about 10% - 50% of the mass of REE-bearing phosphorus ores, shall be added to the agitation tank.

In the method aforesaid, the sulfuric acid in Step (4) shall be with the concentration above 90%, with the reaction temperature of 35 °C-80 °C and reaction time of 3 - 4 hours.

The method in the invention is to remove phosphorus and calcium and enrich rare earth by priority leaching in the mixed solution of phosphoric acid and mono-calcium phosphate from phosphorus ore with rare earth and to reduce the concentration of available acid in the leaching agent to selectively leach and remove phosphorus and calcium by low temperature and calcium concentration control. Namely, in the low temperature reaction of the mixed solution of phosphorus acid and mono-calcium phosphate, few of nano-scale calcium hydro-phosphate particles are generated while dissolving phosphorus and most calcium from phosphorus ores, to maintain rare earth in the residues in adsorption and eutectic forms and to achieve effective separation and enrichment of rare earth in the phosphorus ores. Moreover, as a result of low available phosphorus acid concentration of leaching agent, low dissolution of iron, aluminum and 4 magnesium from phosphorus ores, few impurity elements are dissolved into regenerated solutions, conducive to the regeneration and reuse of leaching agent of the mixed solution. In principle, no any limitations will be applied to phosphorus ores for the invention. However, since rare earth in phosphorus concentrate is more enriched than those in raw ores, it’s more cost effective to use phosphorus concentrate with rare earth.

To cut down the cost, recycled phosphorus acid is adopted in the invention, but any diluted, crude or industrial phosphorus acid can also be applied. A method to remove phosphorus and calcium and enrich rare earth by priority leaching in the mixed solution of phosphoric acid and mono-calcium phosphate from phosphorus ore with rare earth, is to selectively dissolve the phosphorus and calcium by the reacting technology of low temperature and calcium concentration control for enriching the rare earth. In comparison with wet-process phosphorus acid production process, the simpler but new procedures are of high rare earth enrichment ratio and recovery rate.

Brief Description of the Drawings

Fig. 1 refers to a principle processing drawing for the method introduce in the invention.

Detailed Description A method to remove phosphorus and calcium and enrich rare earth by priority leaching in the mixed solution of phosphoric acid and mono-calcium phosphate from phosphorus ore with rare earth, is to mix REE-bearing phosphorus ores with recycled phosphorus acid solution with 15wt%-55wt% of P2O5 and 2-25 g/L Ca2+ at the solid-liquid ratio of 1:2-10, to stir the mixture to activate its reaction at the temperature of 20°C-70°C for 0.5-4 hours, and age 1- 5 hours to gain rare earth enrichment residue and lixivium by solid-liquid separation. Mix the gained lixivium with sulfuric acid and appropriate amounts of gypsum residue, where the mole quantity of added sulfuric acid is about 0.7-1 times of calcium mole quantity in the lixivium, and the added amount of gypsum residue is 10%-100% of the mass of REE-bearing phosphorus ores. Through reaction and filtering, get regenerated phosphorus acid and gypsum residue, part of which need to be washed and added water properly for mixture, back used as recycled phosphorus acid.

The invention is further illustrated in the non-defining examples below to help you for a better understanding of the content and advantages of the invention, rather than defining the protection scope of the invention, which will be prescribed in patent claims.

Embodiment 1

Mix lOOg REE-bearing phosphorus ores (0.14 wt %) with l,000mL diluted phosphorus acid solution - with 20 wt% P205 and 8 g/L Ca2+ - at the solid-liquid ratio of 1:10, stir the mixture at the temperature of 20°C for 1 hour reaction, and then age for 2 hours to filter to get the filtrate and leaching residue. After drying out, weigh and analyze the residue, to get the residue rate of 22%, 0.59% of rare earth out of residue, and 93% of rare earth enriched in the residue, with the enrichment factor of 4.2 times. 5

Embodiment 2

Mix lOOg phosphorus ores with rate earth (0.14 wt %) with l,000mL diluted phosphorus acid solution with 20 wt% P2O5 and 8 g/L Ca2+ at the solid-liquid ratio of 1:10, stir the mixture at the temperature of 45°C for 1 hour reaction, then age for 2 hours, and filter to get the filtrate and leaching residue. After drying out, weigh and analyze the residue to get the residue rate of 21%, 0.57% of rare earth out of residue, and 85% of rare earth enriching in the residue, with the enrichment factor of 4.1 times.

Embodiment 3

Mix lOOg REE-bearing phosphorus ores (0.14 wt %) with l,000mL diluted phosphorus acid solution with 20 wt% P205 and 8 g/L Ca2+ at the solid-liquid ratio of 1:10, stir the mixture at the temperature of 25°C for 3 hours reaction, then age for 4 hours, and filter to get the filtrate and leaching residue. After drying out, weigh and analyze the residue to get the residue rate of 18%, 0.73% of rare earth out of residue, and 94% of rare earth enriching in the residue, with the enrichment factor of 5.2 times.

Embodiment 4

Mix 200g REE-bearing phosphorus ores (5 wt %) with l,000mL recycled phosphorus acid solution with 30 wt% P2O5 and 15 g/L Ca2+ at the solid-liquid ratio of 1:10, stir the mixture at the temperature of 30°C for 4 hours reaction, then age for 2 hours, and filter to get the filtrate and leaching residue. After drying out, weigh and analyze the residue, to get the residue rate of 25%, 19.5% of rare earth out of residue, and 95% of rare earth enriching in the residue, with the enrichment factor of 4 times.

Embodiment 5

Mix lOOg phosphorus concentrate with rare earth (0.8 wt %) with l,000mL diluted phosphorus acid solution with 28 wt% P2O5 and 12 g/L Ca2+ at the solid-liquid ratio of 1:10, stir the mixture at the temperature of 30°C for 4 hours reaction, then age for 2 hours, and filter to get the filtrate and leaching residue. After drying out, weigh and analyze the residue, to get the residue rate of 25%, 3.04% of rare earth out of residue, and 95% of rare earth enriching in the residue.

Embodiment 6

Mix lOOg REE-bearing phosphorus ores (5 wt %) with l,000mL diluted phosphorus acid solution with 35 wt% Ρ205 and 15 g/L Ca2+ at the solid-liquid ratio of 1:10, stir the mixture at the temperature of 50°C for 4 hours reaction, then age for 2 hours, and filter to get the leaching residue. The leaching residue will be re-enriched under the same condition, and then be processed with the solid-liquid separation, to get the residue rate of 20%, 24.5% of rare earth out of residue, and 95% of rare earth enriching in the residue.

Embodiment 7

Mix lixivium in the Example 6 with sulfuric acid with the concentration rate of 95% for 0.85 times of mole quantity of calcium in the lixivium, and 50g gypsum residues, to be in reaction at the temperature of 50°C for 3 hours reaction. Mix 500 mL filtrate with 50g REE-bearing phosphorus ores (5 wt %), stir the mixture 6 at the temperature of 50°C for 4 hours reaction, then age for 2 hours, and filter to get the leaching residue. The leaching residue will be re-enriched under the same condition, and then be processed with the solid-liquid separation, to get the residue rate of 22%, 21.5% of rare earth out of residue, and 95% of rare earth enriching in the residue.

In summary the descriptions aforesaid only refer to the preferred embodiments of the invention, but its scope of the protection is not limited to herein. The present teachings encompass various available alternatives and modifications, as will be appreciated by those of skill in the art. Therefore, the scope of protection for the invention shall be subject to provisions stated in the Patent Claims. 7

Claims

Patent Claims

1. A rare earth enrichment method by priority leaching and removing phosphoms and calcium from REE-bearing phosphoms ores is featured by its processing procedures as below: (1) The REE-bearing phosphoms ores react with recycling leaching agent, at the temperature of 20°C-70°C, with the priority of 30°C-50°C; (2) Transfer the ore pulp prepared in Step (1) into an agitation tank for aging for 1-5 hours; (3) Conduct the ore pulp in Step (2) with a solid-liquid separation process, and get rare earth enrichment residue and lixivium; (4) Mix the lixivium in Step (3) with sulfuric acid and gypsum residue, where the molar quantity of added sulfuric acid is about 0.7-1 times of calcium molar quantity in the lixivium, and the mass of added gypsum residue is 10%-100% of the mass of REE-bearing phosphoms ores; (5) Conduct the ore pulp in Step (4) with a solid-liquid separation process, and get regenerated phosphoms acid and gypsum residue, part of which need to be washed and added water properly for mixture, back to Step (1) used as recycled phosphoms acid.
2. The rare earth enrichment method of claims 1, wherein the recycled leaching agent in Step (1) is the mixture of phosphoms acid and mono-calcium phosphate, its P205 mass concentration is about 15%-55% with the priority of 20%-35%, and the Ca2+ concentration is 2-25 g/L with the priority of 5-15 g/L; the mass and volume ratio of phosphoms concentrate with rare earth and recycled phosphoms acid is 1:2-10 with the priority of 1:4-8; the reaction time takes 0.5-4 hours with the priority of 1-3 hours.
3. The rare earth enrichment method of claims 1, wherein the P2Os mass concentration of the available phosphoms acid stated in Step (1) is at 5%-45% in leaching agents with the priority of 10%-25%.
4. The rare earth enrichment method of claims 1, wherein by said ageing process in Step (2),while ageing, rare earth enrichment residue made in Step (3) - about 10%-50% of the mass of REE-bearing phosphoms ores - shall be added to the agitation tank.
5. The rare earth enrichment method of claims 1, wherein in step (4), where the sulfuric acid is of the concentration above 90%, to react at the temperature of 35°C-80°C for 3-4 hours.