CN106319247B

CN106319247B - The method of phosphorus and rare earth is recycled from containing rare earth phosphate rock

Info

Publication number: CN106319247B
Application number: CN201510347631.5A
Authority: CN
Inventors: 王良士; 黄小卫; 巫圣喜; 于瀛; 王春梅; 崔大立; 冯宗玉; 董金诗; 龙志奇
Original assignee: Grirem Advanced Materials Co Ltd
Current assignee: Grirem Advanced Materials Co Ltd
Priority date: 2015-06-19
Filing date: 2015-06-19
Publication date: 2019-01-25
Anticipated expiration: 2035-06-19
Also published as: CN106319247A

Abstract

The method that the present invention provides a kind of to recycle phosphorus and rare earth from containing rare earth phosphate rock obtains acid leaching residue and contains rare earth ion, Ca this method comprises: step S1, leaches rare earth phosphate rock with the solution of phosphoric acid²⁺And H₂PO₄ ^‑Leachate；Leachate progress ripening is obtained phosphoric acid rare-earth precipitation, makes rare earth and Ca by step S2²⁺And H₂PO₄ ^‑Separation；Wherein, the reaction temperature of step S2 is higher than the reaction temperature of step S1.This method carries out acidleach to rare earth phosphate rock under relatively low reaction temperature using the solution of phosphoric acid, enter phosphorus and rare earth element in leachate, then ripening is carried out to leachate at relatively high temperatures, rare earth ion is set to form phosphoric acid rare-earth precipitation, that realizes rare earth and phosphorus efficiently separates recycling, and rare-earth enrichment multiple is high, convenient for further recycling.

Description

Method for recovering phosphorus and rare earth from rare earth-containing phosphorite

Technical Field

The invention relates to the field of rare earth recovery, in particular to a method for recovering phosphorus and rare earth from rare earth-containing phosphorite.

Background

Rare earth minerals are commonly associated with minerals such as barite, calcite, apatite, silicate minerals and the like in nature. The occurrence state and content of rare earth elements in minerals are different due to different mineral forming reasons. In the rare earth minerals currently mined, the grade of rare earth oxides is generally several percent. In order to meet the requirement of rare earth metallurgy production, before smelting, the rare earth is separated from other ores by a mineral separation method, so that rare earth minerals are enriched. The content of rare earth oxide in the rare earth concentrate after mineral separation and enrichment is usually 50-70%.

The rare earth minerals mainly comprise bastnaesite, monazite, xenotime, ion adsorption type rare earth ore and the like. At present, the method for recovering rare earth from monazite mainly comprises the following two modes: (1) alkaline decomposition of monazite (suitable for high grade)Monazite ore), during the reaction of monazite and liquid alkali, the rare earth generates hydroxide which is insoluble in water, phosphorus is converted into trisodium phosphate, and the rare earth hydroxide is dissolved by hydrochloric acid and is subjected to impurity removal to obtain mixed rare earth chloride. If the impurities such as iron, silicon and the like in the concentrate are high in content, colloidal substances such as sodium silicate, ferric hydroxide and the like are easily formed, and the precipitation, filtration and separation process is difficult to perform, so that the process cannot normally operate. (2) Decomposing monazite ore by a concentrated sulfuric acid roasting method, mixing monazite concentrate with concentrated sulfuric acid for decomposing at 200-230 ℃, wherein the using amount of the concentrated sulfuric acid is 1.7-2 times of the weight of the concentrate, cooling decomposed products, leaching by using water with the weight of 7-10 times of the weight of the concentrate, and the rare earth content in leachate is about 50g/L (REO) and 25g/L P₂O₅，2.5g/L Fe₂O₃The acidity was 2.5 mol/L. The leaching solution has high acidity and high impurity phosphorus and thorium, adopts sodium sulfate double salt to precipitate rare earth and thorium, then converts the rare earth and the thorium into hydroxide through alkali, preferentially leaches the rare earth through acid, and extracts and separates the rare earth and the thorium. The method has the advantages of complex process, multiple liquid-solid separation steps, discontinuous process and low rare earth recovery rate; in addition, acid and alkali are used alternately, the consumption cost of chemical raw materials is high, the difficulty of phosphorus entering wastewater treatment is high, and the radioactive element thorium is difficult to effectively recover after being dispersed in slag and wastewater.

Phosphorite is the main raw material for producing phosphorus chemical products, and the worldwide phosphorite resource reserves are large and are often associated with trace rare earth. At present, the method for recovering rare earth in phosphorite comprises the following processes: (1) the wet phosphoric acid process for treating phosphorite by hydrochloric acid and nitric acid comprises the steps of adding more than 95% of rare earth into a solution, and recovering the rare earth by adopting solvent extraction, ion exchange, precipitation, crystallization and other modes; (2) the wet process phosphoric acid technology for treating phosphorite by sulfuric acid method includes adding rare earth into solution and phosphogypsum, leaching phosphogypsum with sulfuric acid to make rare earth into solution, and recovering rare earth from solution by solvent extraction, ion exchange, precipitation, crystallization and other methods. (3) A process for treating phosphorite by phosphoric acid, in the prior art, phosphate concentrate containing rare earth is mixed with phosphoric acid solution for reaction, the rare earth in the phosphorite is precipitated in a fluoride form by controlling process conditions, more than 85% of rare earth enters slag, and hydrochloric acid, nitric acid or sulfuric acid is adopted to dissolve and recover the rare earth in the slag, but the grade of the rare earth in the slag is very low, about 1%, the contents of impurities such as phosphorus, calcium, aluminum, silicon and the like are high, the rare earth fluoride is difficult to dissolve by acid, the acid consumption is high, the slag amount is large, and the recovery rate of the rare earth is low; in addition, 15% of rare earth entering the leaching solution is easy to enter gypsum slag during the calcium removal process and is difficult to recover.

The phosphorite containing monazite and rare earth is a mineral which is difficult to treat, and the phosphorite containing the monazite and the rare earth simultaneously contains a plurality of components including monazite, rare earth, phosphorite and the like. Because the monazite and the phosphorite belong to the same phosphate mineral and have closer mineralogical properties, the monazite and the phosphorite are closely embedded in the symbiotic mineral. When the rare earth elements and the phosphorus elements in the mixed ore are recovered, the coating, inlaying and dissociating difficulty of all the substances in the mixed ore is high, and the effective separation of the ore is difficult to realize by physical ore dressing. In particular, relatively harsh conditions are required for decomposing monazite, and relatively high temperature, high pH value and the like are required, so that when the phosphate ores containing monazite are treated by adopting the sulfuric acid method wet method in the prior art, the monazite cannot be completely decomposed, and the monazite cannot be effectively separated and utilized.

Therefore, how to effectively separate and recover phosphorus element and rare earth element in rare earth phosphorite, especially rare earth in mixed phosphorite containing monazite, which has low quality and complex mineral composition, becomes a technical problem to be solved urgently.

Disclosure of Invention

The invention mainly aims to provide a method for recovering phosphorus and rare earth from rare earth-containing phosphorite, so as to solve the problem of low recovery efficiency of phosphorus and rare earth elements in the rare earth phosphorite in the prior art.

In order to achieve the above object, according to one aspect of the present invention, there is provided a method for recovering phosphorus and rare earth from a rare earth-containing phosphorite, the method comprising the steps of: step S1, leaching the rare earth phosphorite by using a solution containing phosphoric acid to obtain a leaching solution and acid leaching slag, wherein the leaching solution contains rare earth ions and Ca²⁺And H₂PO₄ ^-(ii) a And step S2, aging the leachate to obtain rare earth phosphate precipitate and monocalcium phosphate solution; the reaction temperature of step S2 is higher than the reaction temperature of step S1.

Further, step S1 includes: leaching the rare earth phosphorite by using a solution containing phosphoric acid at the temperature of 10-60 ℃ for 0.5-8 hours, preferably 1-4 hours to obtain a leaching solution and acid leaching residues.

Further, step S2 includes: and (3) aging the leachate at 60-150 ℃, preferably 80-120 ℃ for 0.5-24 hours, preferably 1-8 hours, to obtain rare earth phosphate precipitate and monocalcium phosphate solution.

Further, when the rare earth phosphorite does not contain monazite, the method also comprises the following steps: recovering rare earth elements in the phosphoric acid rare earth precipitate; and recovering phosphorus element in the monocalcium phosphate solution.

Further, when the rare earth phosphate ore contains monazite, the method also comprises the following steps: mixing the acid leaching residue with the rare earth phosphate precipitate to obtain rare earth mixed residue, and recovering rare earth elements in the rare earth mixed residue; and recovering phosphorus element in the monocalcium phosphate solution.

Further, the step of recovering the phosphorus element in the monocalcium phosphate solution comprises the following steps: adding concentrated sulfuric acid with the mass concentration of more than 90% into the monocalcium phosphate solution to obtain a solid-liquid mixture; and carrying out solid-liquid separation on the solid-liquid mixture to obtain a first phosphoric acid solution and calcium sulfate.

Further, in the step of recovering phosphorus element from the monocalcium phosphate solution, after obtaining the first phosphoric acid solution, the method further includes: returning the first phosphoric acid solution to the step S1 to leach the rare earth phosphate ore; or removing impurities from the first phosphoric acid solution to obtain a second phosphoric acid solution; and returning the second phosphoric acid solution to the step S1 to leach the rare earth phosphorite.

Further, the step of recovering the rare earth elements in the rare earth mixed slag comprises the following steps: step A, adding an iron-containing substance into the rare earth mixed slag; adding concentrated sulfuric acid with the mass concentration of more than 90% to obtain a mixture; b, roasting the mixture to obtain a roasted product; step C, adding water to the roasted product for leaching to obtain a rare earth-containing water leaching solution and water leaching slag; d, adjusting the pH value of the rare earth-containing water leaching solution to 3.8-5, and filtering to obtain a rare earth sulfate solution and filter residues, wherein the filter residues contain iron elements, phosphorus elements and thorium elements; step E, preparing a rare earth compound by taking a sulfuric acid rare earth solution as a raw material; wherein, step E includes: extracting and separating the rare earth sulfate solution by using an acidic phosphorus extractant to obtain a mixed rare earth chloride compound or a single rare earth compound; or adding carbonate or oxalate into the rare earth sulfate solution to precipitate rare earth, thereby obtaining rare earth carbonate or rare earth oxalate; and calcining the rare earth carbonate or rare earth oxalate to obtain the rare earth oxide.

Further, the iron-containing substances are iron-containing tailings and/or iron-containing waste residues.

Further, the mass ratio of the iron element in the iron-containing substance to the phosphorus element in the rare earth mixed slag is 2-4: 1, preferably 2.5-3.5: 1.

further, step a comprises: mixing concentrated sulfuric acid and rare earth mixed slag according to the mass ratio of 1-2: 1, were mixed.

Further, in the step B, the roasting temperature is 200-500 ℃ and the roasting time is 1-8 hours, preferably 250-400 ℃ and the roasting time is 2-4 hours.

Further, in the step D, at least one of magnesium oxide, magnesium hydroxide and light-burned dolomite is adopted to adjust the pH value of the rare earth-containing water leaching solution to 4-4.5.

Further, the solution containing phosphoric acid also contains hydrochloric acid and/or nitric acid.

Further, with P₂O₅The mass concentration of the phosphoric acid in the phosphoric acid-containing solution is 15 to 50 percent, preferably 15 to 30 percent.

Furthermore, the proportion of hydrochloric acid and/or nitric acid in the phosphoric acid-containing solution is < 30%, preferably 2-15%, based on the number of moles of anions.

Further, before the step S1, the method further comprises the step of mixing the solution containing phosphoric acid and the rare earth phosphate ore according to a liquid-solid ratio of 2-10L: 1kg, preferably selecting a mixture with a liquid-solid ratio of 3-6L: 1 kg.

By applying the technical scheme of the invention, the rare earth phosphate ore is leached by adopting the solution containing phosphoric acid at a relatively low reaction temperature, the hydrogen ions in the phosphoric acid-containing solution are used for dissolving the phosphorus in the phosphate ore to form monocalcium phosphate solution, and meanwhile, the rare earth elements are also dissolved and enter the solution to form the solution containing rare earth ions and Ca²⁺And H₂PO₄ ^-The leachate of (2); further aging the leachate, which is favorable for forming rare earth phosphate precipitate from the rare earth elements to realize the separation of the rare earth elements from the phosphorus elements. The reaction temperature has little influence on the leaching of the phosphorus element in the acid leaching process, the solubility of the rare earth phosphate is relatively high at a lower temperature, the leaching of the rare earth element is facilitated, and simultaneously, the leaching of impurity elements such as iron, aluminum and the like in phosphorite can be effectively inhibited at a low temperature, so that the leaching rates of the iron element and the aluminum element are ensured<5 percent, greatly reducing the burden of subsequent phosphoric acid purification and impurity removal. And the temperature of the aging treatment is controlled to be higher than the temperature of the acid leaching step, so that the rare earth phosphate solubility product is small at relatively high temperature, the rare earth elements in the leaching solution are precipitated in the form of rare earth phosphate, and the effective separation of the rare earth elements and phosphorus elements is further realized. From phosphorite containing rare earth to phosphoric acid rare earth precipitation, the rare earth enrichment multiple is as high as dozens of times or even hundreds of times, the rare earth grade in the phosphoric acid rare earth precipitation can reach more than 45 percent, even more than 55 percent, the rare earth yield can reach more than 80 percent, even more than 90 percent, the rare earth separation efficiency is improved, the purpose of separating rare earth with low cost is realized, and the subsequent further recycling of rare earth elements is facilitated. When the phosphorus ore containing rare earth contains monazite, the monazite is not dissolved and remains in the slag in the acid leaching process, and the separation of rare earth elements and phosphorus elements is also realized. Produced by precipitation and acid leaching of rare earth phosphatesThe acid-containing leaching residues are mixed to form rare earth mixed residues, and the rare earth mixed residues have high rare earth content, so that the rare earth elements can be conveniently recycled in the follow-up process.

Drawings

The accompanying drawings, which are incorporated in and constitute a part of this application, illustrate embodiments of the invention and, together with the description, serve to explain the invention and not to limit the invention. In the drawings:

FIG. 1 is a schematic flow diagram showing a process for recovering phosphorus and rare earth from a rare earth-containing phosphorus ore according to an exemplary embodiment of the present invention; and

FIG. 2 is a schematic flow chart showing a process for recovering phosphorus and rare earth from rare earth-containing phosphorite when the rare earth-containing phosphorite also contains monazite according to another exemplary embodiment of the invention.

Detailed Description

It should be noted that the embodiments and features of the embodiments in the present application may be combined with each other without conflict. The present invention will be described in detail with reference to examples.

In the following description, Monazite (English name: Monazite) has the molecular formula of (Ln, Th) PO₄In the formula, Ln is at least one of rare earth elements except promethium.

The leachate is a solution containing impurities such as rare earth, phosphoric acid, monohydrogen phosphate, dihydrogen phosphate, iron, aluminum, etc., in addition to monocalcium phosphate.

The grade of the leaching solution refers to the content ratio of useful elements or compounds thereof in the ore. The higher the content, the higher the grade.

As indicated by the background, rare earth phosphate ores, e.g. containing fly ashThe mixed ore of various minerals such as stone, monazite and the like is treated by the existing separation method, and the rare earth element and the phosphorus element in the mixed ore are difficult to be effectively separated. In order to ameliorate the above-mentioned disadvantages of the prior art, in one exemplary embodiment of the present invention, there is provided a method for recovering phosphorus and rare earth from a rare earth-containing phosphorus ore, the method comprising the steps of: step S1, leaching the rare earth phosphorite by using a solution containing phosphoric acid to obtain a leaching solution and acid leaching slag, wherein the leaching solution contains rare earth ions and Ca²⁺And H₂PO₄ ^-(ii) a And step S2, aging the leachate to obtain rare earth phosphate precipitate and monocalcium phosphate solution; wherein the reaction temperature of step S2 is higher than the reaction temperature of step S1.

In the method, at a relatively low reaction temperature, rare earth phosphorite is leached by adopting a solution containing phosphoric acid, hydrogen ions in a phosphoric acid-containing solution are used for dissolving phosphorus in the phosphorite to form a monocalcium phosphate solution, and meanwhile, rare earth elements are dissolved in the acid leaching process and enter the solution in the form of ions to form a leaching solution; and further aging the leachate, which is favorable for forming rare earth phosphate precipitate from the rare earth elements contained in the solution, so that the separation of the rare earth elements and phosphorus elements is realized. The influence of the reaction temperature on the leaching of phosphorus in the acid leaching process is small, the solubility of the rare earth phosphate is high at relatively low temperature, the leaching of rare earth is facilitated, and the leaching of impurity elements such as iron and aluminum in phosphorite can be effectively inhibited at low temperature, so that the leaching rate of the iron element and the aluminum element is less than 5%, and the burden of subsequent purification and impurity removal of phosphoric acid is greatly reduced. And the temperature of the aging treatment is controlled to be higher than that of the acid leaching step, so that the rare earth solubility product of phosphoric acid at high temperature is small, the rare earth elements in the leaching solution are precipitated in the form of rare earth phosphate, and the further effective separation of the rare earth elements and phosphorus elements is realized.

In the separation method, the rare earth enrichment times from the rare earth phosphate ore to the rare earth phosphate precipitation are dozens of times or even hundreds of times, and the rare earth grade in the rare earth phosphate precipitation can reach more than 45 percent or even more than 55 percent; the yield of the rare earth reaches more than 80 percent, even more than 90 percent, the rare earth separation efficiency is greatly improved, the purpose of separating the rare earth with low cost is realized, and the subsequent further recycling of the rare earth elements is convenient.

In the step S1, the leaching with the phosphoric acid-containing solution is performed to dissolve out phosphorus and rare earth elements in the rare earth phosphorite, and impurity elements such as iron and aluminum remain in the slag to form acid leaching slag. Thus, any leaching process conditions that allow phosphorus and rare earth elements to be dissolved out as much as possible while impurity elements such as iron and aluminum remain in the acid-leached slag as much as possible are suitable for the present invention. In a preferred embodiment of the invention, the leaching solution and the acid leaching residue are obtained by leaching the rare earth phosphorite with the solution containing phosphoric acid for 0.5 to 8 hours, preferably 1 to 4 hours at the temperature of 10 to 60 ℃. The acid leaching residue can be selectively returned to the phosphorus element recovery process so as to further leach and recover the residual phosphorus element.

In the leaching step by adopting the solution containing phosphoric acid, the reaction temperature is controlled within the range of 10-60 ℃, the reaction temperature has small influence on the dissolution of phosphorus in the rare earth phosphorite, the solubility of rare earth phosphate is relatively high at the temperature, the leaching of rare earth is facilitated, and the leaching of impurity elements such as iron, aluminum and the like in the rare earth phosphorite can be effectively inhibited at the low temperature, so that the leaching rate of the iron element and the aluminum element is less than 5%, and the subsequent impurity removal burden is greatly reduced. More preferably, the leaching time is 2 to 5 hours. The leaching time in the range is selected, so that the phosphorus element and the rare earth element can be completely dissolved out, and the leaching period can be shortened.

In the aging treatment step, the specific time and temperature of the aging treatment can be adjusted according to different types of rare earth phosphorite. In a preferred embodiment of the invention, the leachate is aged at a temperature of 60-150 ℃, preferably 80-120 ℃, for 0.5-24 hours, preferably 1-8 hours, and the rare earth phosphate precipitate and the second solution are obtained by solid-liquid separation. The rare earth phosphate has small solubility product at high temperature, and the adoption of the higher temperature is favorable for precipitating the rare earth elements in the leaching solution in the form of rare earth phosphate, thereby realizing the effective separation of the rare earth elements and phosphorus elements. With increasing aging time, crystals grow up gradually, and amorphous precipitates gradually transform into crystalline precipitates. In the aging time range, the rare earth elements in the leachate can be precipitated more thoroughly, so that the separation of the rare earth elements and the phosphorus elements is more effectively realized.

In step S2, the rare earth element is separated in the form of rare earth phosphate precipitate to obtain a monocalcium phosphate solution, which contains calcium ions and dihydrogen phosphate ions as main components, and further contains a small amount of impurity ions such as monohydrogen phosphate ions, iron ions, or aluminum ions.

The separation method can effectively separate rare earth phosphate precipitate and leachate for removing rare earth ions, the rare earth enrichment factor is as high as dozens of times or even hundreds of times from rare earth phosphorite to rare earth phosphate precipitate, the rare earth grade in the rare earth phosphate precipitate can reach more than 45 percent, even more than 55 percent, the rare earth yield can reach more than 80 percent, even more than 90 percent, the rare earth separation efficiency is improved, the purpose of separating rare earth with low cost is realized, and the subsequent further recycling of rare earth elements is facilitated. In a preferred embodiment of the present invention, when the rare earth phosphate ore does not contain monazite, the method further comprises: recovering rare earth elements in the phosphoric acid rare earth precipitate; and recovering phosphorus element in the monocalcium phosphate solution. The step of recovering the rare earth elements adopts any one of acid dissolution, alkali conversion-acid dissolution, sulfuric acid roasting-water leaching for treatment, and then precipitation enrichment or extraction separation and purification are carried out. On the basis of higher separation efficiency, the recovery rate of the rare earth elements and the phosphorus elements is relatively higher.

The rare earth phosphate ore which can be separated by the separation method of the invention includes, but is not limited to, rare earth-containing apatite ore, phosphorite or rare earth-containing collophanite. In a preferred embodiment of the present invention, the rare earth phosphate ore separated by the above separation method is a monazite-containing rare earth phosphate ore. As shown in fig. 2, when the rare earth phosphorite contains monazite, the separation method is adopted for separation, the monazite is not dissolved in the acid leaching process and remains in slag, and the separation of rare earth elements and phosphorus elements can be realized. Then, the rare earth phosphate precipitate is mixed with acid leaching slag generated in the acid leaching process to form rare earth mixed slag. The rare earth mixed slag obtained by the two steps of separation and summary has high rare earth content (the rare earth yield of the rare earth phosphorite is more than 90% and the leaching rates of Fe and Al are respectively less than 10% in terms of the rare earth mixed slag), even in some more preferable embodiments, the rare earth yield of the rare earth phosphorite is more than 97% and the leaching rates of Fe and Al are respectively less than 5%), the rare earth separation efficiency is improved, the purpose of separating rare earth with low cost is realized, and the subsequent further recycling of rare earth elements is facilitated.

The rare earth phosphate rock containing monazite is a mineral which is difficult to treat, and since the monazite and the phosphate rock belong to phosphate minerals and have relatively similar mineralogical properties, the monazite and the phosphate rock are closely embedded in the symbiotic minerals. When the rare earth elements and the phosphorus elements in the mixed ore are recovered, the coating, inlaying and dissociating difficulty of all the substances in the mixed ore is high, and the effective separation of the ore is difficult to realize by physical ore dressing. In particular, relatively harsh conditions are required for decomposing monazite, and relatively high temperature, high pH value and the like are required, so that when the phosphate ores containing monazite are treated by adopting the sulfuric acid method wet method in the prior art, the monazite cannot be completely decomposed, and the monazite cannot be effectively separated and utilized. The method realizes the separation of phosphorus and monazite by utilizing the insolubility of monazite in the acid leaching process and the enrichment of monazite in slag. The rare earth entering the solution is precipitated and separated out by rare earth phosphate through aging treatment, and the rare earth is recovered together after the rare earth phosphate and monazite which is not dissolved in the acid leaching process form rare earth mixed slag, so that the recovery steps are simplified, the recovery rate of the rare earth is improved, and the aim of comprehensively recovering the rare earth at low cost is fulfilled.

After the high-grade rare earth mixed slag and the high-purity monocalcium phosphate solution are obtained, a person skilled in the art can determine whether to further respectively recover the rare earth elements in the rare earth mixed slag and the phosphorus elements in the monocalcium phosphate solution according to actual needs, and can specifically select a proper recovery method. In a preferred embodiment of the present invention, as shown in fig. 2, after obtaining the rare earth mixed slag and the monocalcium phosphate solution, the method further includes: recovering rare earth elements in the rare earth mixed slag; and recovering phosphorus element in the monocalcium phosphate solution to fully utilize rare earth and phosphorus in the rare earth phosphorite.

The specific recovery process for recovering the rare earth elements in the rare earth mixed slag can be reasonably selected according to different utilization modes of the rare earth elements. In a preferred embodiment of the present invention, as shown in fig. 2, the step of recovering the rare earth from the rare earth mixed slag includes: step A, adding an iron-containing substance (or simultaneously adding a magnesium-and/or calcium-containing substance) into the rare earth mixed slag, and adding concentrated sulfuric acid with the mass concentration of more than 90% to obtain a mixture; b, roasting the mixture to obtain a roasted product; step C, adding water to the roasted product for leaching to obtain a rare earth-containing water leaching solution and water leaching slag; d, adjusting the pH value of the rare earth-containing water leaching solution to 3.8-5, and filtering to obtain a rare earth sulfate solution and filter residues, wherein the filter residues contain iron elements, phosphorus elements and thorium elements; and step E, preparing a rare earth compound by using a sulfuric acid rare earth solution; wherein, step E includes: extracting and separating the rare earth sulfate solution by using an acidic phosphorus extractant to obtain a mixed rare earth chloride compound or a single rare earth compound; or adding carbonate or oxalate into the rare earth sulfate solution to precipitate rare earth, thereby obtaining rare earth carbonate or rare earth oxalate; and calcining the rare earth carbonate or rare earth oxalate to obtain the rare earth oxide.

The preferred embodiment keeps the rare earth in the rare earth phosphorite in the rare earth mixed slag, so that the grade of the rare earth in the rare earth mixed slag is improved, and the workload of subsequent treatment is greatly reduced. By adopting unique iron-added phosphorus fixation, phosphorus is solidified in slag, and the loss of rare earth is avoided. If magnesium and/or calcium are added at the same time, fluorine can be fixed, and the interference of phosphorus and fluorine can be eliminated, so that the loss caused by the rare earth forming phosphoric acid rare earth precipitation or rare earth fluoride precipitation in the subsequent water-adding leaching process can be effectively avoided. Meanwhile, the method also avoids the environmental pollution caused by the escape of fluorine element in the form of hydrogen fluoride gas in the roasting process. The method for recovering the rare earth elements has less acid and alkali consumption, and the recovery rate of the rare earth can reach more than 90 percent; meanwhile, thorium element is converted into thorium pyrophosphate to be solidified in slag, so that the scattered pollution of radioactive thorium element in the process flow is avoided.

In the process of recovering the rare earth elements in the rare earth mixed slag, the purpose of the added substances containing magnesium and/or calcium is to fix the fluorine elements in the mixed slag in the slag and facilitate the separation of the rare earth elements, so that any substances containing magnesium and/or calcium, which can enable the fluorine elements to be retained in the slag and the rare earth elements to be separated, are suitable for the invention. In a preferred embodiment of the present invention, the magnesium and/or calcium-containing substance is at least one of magnesium and/or calcium-containing oxide, magnesium and/or calcium-containing carbonate, and magnesium and/or calcium-containing mineral; more preferably, the magnesium and/or calcium containing mineral is dolomite and/or magnesite; the iron-containing material is iron-containing tailings and/or iron-containing waste residues, preferably tailings containing rare earth and iron. The ore has the advantage of rich resources, and the waste residues can save energy, reduce emission and change waste into valuable.

Preferably, in the process of adding the magnesium and/or calcium-containing substance, the ratio of the mole number of magnesium and/or calcium elements in the magnesium and/or calcium-containing substance to the mole number of fluorine elements in the rare earth mixed slag is 1-2: 2. the mixing ratio of the magnesium/calcium-containing substance and the phosphoric acid rare earth slag in the invention is not limited to the above range, and the magnesium/calcium-containing substance and the phosphoric acid rare earth slag are mixed by mixing the magnesium/calcium-containing substance and the phosphoric acid rare earth slag in a molar ratio of 1-2: 2 mixing, being favorable to reducing under the prerequisite that contains the input of magnesium/calcium material, can form magnesium fluoride/calcium, magnesium fluorophosphate/calcium solid with fluorine in the ore deposit and fix in the sediment, slowed down fluorine and escaped the polluted environment problem with hydrogen fluoride gas in the calcination process, avoided fluorine to form the rare earth loss that the rare earth fluoride deposit caused in solution edulcoration process simultaneously to the yield of tombarthite has been improved.

In the process of adding the iron-containing substance into the mixed slag, the addition amount of the iron-containing substance can be properly adjusted according to the content of the phosphorus element in the rare earth mixed slag. In a preferred embodiment of the invention, the mass ratio of the iron element in the iron-containing substance to the phosphorus element in the rare earth mixed slag is 2-4: 1, preferably 2.5 to 3.5: 1. the iron-containing rare earth tailings are added in the range for treatment, so that the rare earth yield is improved, the rare earth in the tailings is recycled, and the operation cost is greatly reduced; in the subsequent impurity removal process of adjusting the pH value to 3.8-5, iron phosphate precipitation can be effectively formed by controlling the Fe/P mass ratio, the phosphorus removal effect is good, excessive iron can be hydrolyzed to form precipitation under the condition of the pH value, the formation of rare earth phosphate precipitation is avoided, and the loss of rare earth is avoided.

Similarly, in the process of adding the concentrated sulfuric acid into the rare earth mixed slag, the dosage of the concentrated sulfuric acid can be properly adjusted according to the quality of the rare earth mixed slag. In a preferred embodiment of the invention, the mass ratio of concentrated sulfuric acid to rare earth mixed slag is 1-2: 1 to obtain a mixture. The mass ratio of the concentrated sulfuric acid to the rare earth mixed slag is controlled in the range, so that the sulfuric acid dosage is effectively controlled, and the effect of decomposing and leaching the rare earth is improved.

In the process of roasting the mixture, the roasting temperature can be reasonably selected according to different types and contents of the rare earth elements in the mixture. In a preferred embodiment of the invention, the temperature of the calcination mixture is 200 to 500 ℃, preferably 250 to 400 ℃. Roasting in the temperature range is favorable for forming phosphate and/or pyrophosphate precipitate of thorium, iron and phosphoric acid and solidifying the phosphate and/or pyrophosphate precipitate in the slag without leaching, and meanwhile, radioactive element thorium is also solidified in the slag, so that the scattered pollution of radioactive thorium in the process flow is avoided.

In the process of adjusting the pH value of the rare earth-containing aqueous leaching solution, appropriate substances can be selected according to the components and the pH value of the rare earth aqueous leaching solution to adjust the pH value of the rare earth aqueous leaching solution to an appropriate value. In a preferred embodiment of the invention, the pH value of the rare earth-containing water leaching solution is adjusted to 4-4.5 by adopting magnesium oxide and/or light-burned dolomite. Magnesium oxide and/or light-burned dolomite are/is adopted to adjust the pH value of the rare earth-containing water leaching solution, so that iron phosphate and thorium phosphate precipitate are formed as much as possible in phosphorus elements, and rare earth does not precipitate, thereby improving the recovery rate of the rare earth.

The specific recovery process for recovering the phosphorus element in the monocalcium phosphate solution can be reasonably selected according to different utilization modes of the phosphorus element. In a preferred embodiment of the present invention, as shown in fig. 1, the step of recovering phosphorus comprises: adding concentrated sulfuric acid with the mass concentration of more than 90% into the monocalcium phosphate solution to obtain a solid-liquid mixture; and carrying out solid-liquid separation on the solid-liquid mixture to obtain a first phosphoric acid solution and calcium sulfate. The above preferred embodiment has the beneficial effect of recovering the phosphorus element in the monocalcium phosphate solution in the form of the first phosphoric acid solution containing phosphoric acid, thereby realizing the preparation of a high-value weak acid from a low-value strong acid.

In a more preferred embodiment of the present invention, the step of recovering phosphorus element from the monocalcium phosphate solution further includes, after obtaining the first phosphoric acid solution: directly returning the first phosphoric acid solution to the step S1 for leaching the rare earth phosphorite; or, removing impurities from the first phosphoric acid solution to obtain a second phosphoric acid solution with relatively high phosphoric acid purity; and then returning the second phosphoric acid solution to the step S1 for leaching the rare earth phosphate ore, wherein the second phosphoric acid solution can be further used for phosphate fertilizer production or phosphorus chemical industry production such as phosphoric acid refining and the like. In the method, the recovered phosphoric acid solution containing impurities or after impurity removal is used for decomposing and leaching the rare earth phosphorite, the whole process is reasonable in connection, and not only is the high-efficiency separation of the rare earth elements and the phosphorus elements realized, but also the cyclic utilization of the phosphorus elements is realized. The impurity elements removed in the above impurity removal step include, but are not limited to, iron, silicon, aluminum, calcium, magnesium, thorium, uranium, and the like. The specific impurity removal step can be performed by adopting a conventional process in the prior art as required.

In the process of leaching the rare earth phosphate ore by the phosphoric acid-containing solution, the phosphoric acid-containing solution comprises phosphoric acid, and hydrochloric acid and/or nitric acid can be added according to actual conditions. In a preferred embodiment of the present invention, the phosphoric acid-containing solution further contains hydrochloric acid and/or nitric acid. Hydrochloric acid or nitric acid in the mixed acid solution is beneficial to decomposition of the apatite, so that leaching rate of the apatite and rare earth is improved. And hydrochloric acid or nitric acid can be extractedHydrogen donating ion H⁺Under the condition of the same acid amount, the content of phosphate radical can be reduced, the system viscosity is reduced, and the leaching of phosphorus is facilitated; meanwhile, the existence of chloride ions or nitrate ions is beneficial to improving the solubility of calcium ions in the solution and the decomposition of apatite. In a more preferred embodiment of the present invention, the proportion of hydrochloric acid and/or nitric acid is 0 to 30% (excluding 0), preferably 2 to 15%, based on the number of moles of anions. The content of the hydrochloric acid or the nitric acid used in the invention is not limited to the range, and the hydrochloric acid or the nitric acid with too high content can be used for simultaneously increasing the solubility of the rare earth phosphate in the system, so that the rare earth is difficult to precipitate and separate out in the aging treatment process, the rare earth cannot be enriched in the rare earth phosphate precipitate, and the rare earth yield is low.

In the solution containing phosphoric acid, the mass concentration of phosphoric acid can be reasonably selected according to different leached rare earth phosphorite components. In a preferred embodiment of the present invention, the solution containing phosphoric acid is a solution containing P₂O₅The mass concentration of the phosphoric acid is 15 to 50 percent, preferably 15 to 30 percent. P in the phosphoric acid-containing solution used in the present invention₂O₅The mass concentration is not limited to the above range, and P is used₂O₅When the mass concentration is in the range, higher acidity is beneficial to the decomposition of phosphorite, so that the yield of phosphorus is improved, but the problem of low mass transfer efficiency caused by high viscosity exists due to excessively high content of phosphoric acid.

Before the process of leaching the rare earth phosphorite by the solution containing the phosphoric acid, the solution containing the phosphoric acid and the rare earth phosphorite can be reasonably proportioned according to the concentration of the phosphoric acid in the solution containing the phosphoric acid and the different components of the rare earth phosphorite, so that phosphorus and rare earth elements in the rare earth phosphorite are dissolved out. In a preferred embodiment of the invention, the liquid-solid ratio of the solution containing phosphoric acid to the rare earth phosphate ore mixed solution is 2-10L: 1kg, preferably 3-6L: 1 kg. By controlling the acid dosage, the method is favorable for generating soluble monocalcium Ca (H) phosphate from phosphorus element and calcium element under the condition of reducing the acid dosage₂PO₄)₂The solubility of the rare earth phosphate is high under the condition of high acidity when the rare earth phosphate enters the solution, which is beneficial toLeaching rare earth in apatite into a solution, wherein the proportion in the range is favorable for fully dissolving out phosphorus element and rare earth element, and is favorable for subsequent aging treatment to form rare earth phosphate precipitate enriched rare earth. When the ore also comprises monazite, the monazite which is difficult to dissolve is remained in the slag, thereby realizing the effective separation and recovery of the rare earth element and the phosphorus element.

The advantageous effects of the present invention will be further described with reference to specific examples.

In the following examples, the mass concentration of phosphoric acid is P₂O₅The hydrochloric acid or nitric acid is calculated by the mole number of anions. The contents of iron, aluminum, rare earth and other elements are measured by ICP, and the leaching rate and recovery rate of each element are calculated according to the contents, the phosphorus test is carried out by GBT 1871.1-1995, and the calcium test is carried out by GBT 1871.4-1995.

Example 1

Using 1000g of phosphorite containing 0.05 wt% of rare earth as a raw material, leaching the rare earth phosphorite by adopting a phosphoric acid solution with the mass concentration of 15%, and controlling the liquid-solid ratio of a system to be 10: 1, reacting for 1h at 10 ℃, and filtering to obtain a monocalcium phosphate solution containing rare earth and acid leaching residue.

And (3) placing the monocalcium phosphate solution containing the rare earth at 60 ℃ for aging for 24 hours to separate out the rare earth elements in the form of rare earth phosphate precipitate, and performing solid-liquid separation to obtain the monocalcium phosphate solution and 0.71g of rare earth phosphate precipitate.

Through detection, the leaching rate of impurity Fe in phosphorite is 3.5%, the leaching rate of impurity Al is 2.5%, and the leaching rate of phosphorus element is 95.3%; the content of rare earth in the phosphoric acid rare earth precipitate is 57.1 percent, and the recovery rate of the rare earth is 81.08 percent.

Example 2

Using 1000g of phosphorite containing 0.2 wt% of rare earth as a raw material, leaching the rare earth phosphorite by adopting a phosphoric acid solution with the mass concentration of 20%, and controlling the liquid-solid ratio of a system to be 6: 1, reacting for 6 hours at the temperature of 20 ℃, and filtering to obtain a monocalcium phosphate solution containing rare earth and acid leaching residue.

And (3) ageing the monocalcium phosphate solution containing the rare earth at 60 ℃ for 1h to separate the rare earth elements from the monocalcium phosphate solution in the form of rare earth phosphate precipitate, so that the monocalcium phosphate solution and 3.30g of rare earth phosphate precipitate are obtained through solid-liquid separation.

Through detection, the leaching rate of Fe in phosphorite is 4.1%, the leaching rate of Al is 3.1%, and the leaching rate of phosphorus element is 96.8%; the content of rare earth in the phosphoric acid rare earth precipitate is 52.1 percent, and the recovery rate of the rare earth is 85.97 percent.

Example 3

And (3) ageing the monocalcium phosphate solution containing the rare earth at 80 ℃ for 1h to separate the rare earth elements from the monocalcium phosphate solution in the form of rare earth phosphate precipitate, so that the monocalcium phosphate solution and 3.40g of rare earth phosphate precipitate are obtained through solid-liquid separation.

Through detection, the leaching rate of Fe in phosphorite is 4.1%, the leaching rate of Al is 3.1%, and the leaching rate of phosphorus element is 96.6%; the content of rare earth in the phosphoric acid rare earth precipitate is 53.8 percent, and the recovery rate of the rare earth is 91.46 percent.

Example 4

Using 1000g of phosphorite containing 0.3 wt% of rare earth as a raw material, leaching the rare earth phosphorite by adopting a phosphoric acid solution with the mass concentration of 30%, and controlling the liquid-solid ratio of a system to be 4: 1, reacting for 3 hours at 30 ℃, and filtering to obtain a monocalcium phosphate solution containing rare earth and acid leaching residue.

And (3) placing the monocalcium phosphate solution containing the rare earth at 100 ℃ for aging for 0.5h to separate the rare earth elements from the monocalcium phosphate solution in the form of rare earth phosphate precipitates, and thus obtaining the monocalcium phosphate solution and 4.98g of rare earth phosphate precipitates through solid-liquid separation.

Through detection, the leaching rate of Fe in phosphorite is 4.2%, the leaching rate of Al is 3.2%, and the leaching rate of phosphorus element is 96.5%; the content of rare earth in the phosphoric acid rare earth precipitate is 55.3 percent, and the recovery rate of the rare earth is 91.80 percent.

Example 5

And (3) ageing the monocalcium phosphate solution containing the rare earth at 100 ℃ for 3 hours to separate the rare earth elements from the monocalcium phosphate solution in the form of rare earth phosphate precipitate, so that the monocalcium phosphate solution and 5.03g of rare earth phosphate precipitate are obtained through solid-liquid separation.

Through detection, the leaching rate of Fe in phosphorite is 4.2%, the leaching rate of Al is 3.2%, and the leaching rate of phosphorus element is 96.2%; the content of rare earth in the phosphoric acid rare earth precipitate is 55.4 percent, and the recovery rate of the rare earth is 92.89 percent.

Example 6

Using 1000g of phosphorite containing 0.5 wt% of rare earth as a raw material, leaching the rare earth phosphorite by adopting a phosphoric acid solution with the mass concentration of 40%, and controlling the liquid-solid ratio of a system to be 3: 1, reacting for 4 hours at 25 ℃, and filtering to obtain a monocalcium phosphate solution containing rare earth and acid leaching residue.

And (3) ageing the monocalcium phosphate solution containing the rare earth at 120 ℃ for 4 hours to separate the rare earth elements from the monocalcium phosphate solution in the form of rare earth phosphate precipitate, so that the monocalcium phosphate solution and 8.10g of rare earth phosphate precipitate are obtained through solid-liquid separation.

Through detection, the leaching rate of Fe in phosphorite is 4.5%, the leaching rate of Al is 3.6%, and the leaching rate of phosphorus element is 95.8%; the content of rare earth in the phosphoric acid rare earth precipitate is 56.3 percent, and the recovery rate of the rare earth is 91.21 percent.

Example 7

1000g of phosphorite with the rare earth content of 0.5 wt% is taken as a raw material, and phosphoric acid solution with the mass concentration of 30% (taking P as₂O₅Calculated) and hydrochloric acid mixed solution to leach the rare earth phosphate ore, wherein the hydrochloric acid accounts for 2 percent of the mixed acid by the mole number of anions, and the liquid-solid ratio of the system is controlled to be 4: 1, reacting for 3 hours at 30 ℃, and filtering to obtain a monocalcium phosphate solution containing rare earth and acid leaching residue.

And (3) ageing the monocalcium phosphate solution containing the rare earth at 120 ℃ for 3h to separate the rare earth elements from the monocalcium phosphate solution in the form of rare earth phosphate precipitate, so that the monocalcium phosphate solution and 8.23g of rare earth phosphate precipitate are obtained through solid-liquid separation.

Through detection, the leaching rate of Fe in phosphorite is 4.7%, the leaching rate of Al is 3.8%, and the leaching rate of phosphorus element is 97.1%; the content of rare earth in the phosphoric acid rare earth precipitate is 56.8 percent, and the recovery rate of the rare earth is 93.49 percent.

Example 8

1000g of phosphorite with the rare earth content of 0.5 wt% is taken as a raw material, and phosphoric acid solution with the mass concentration of 30% (taking P as₂O₅Calculated) and nitric acid mixed solution to leach the rare earth phosphate ore, wherein the nitric acid accounts for 2 percent of the mixed acid by the mole number of anions, and the liquid-solid ratio of the system is controlled to be 4: 1, at 30 DEG CReacting for 3 hours, and filtering to obtain a rare earth-containing monocalcium phosphate solution and acid leaching residues.

And (3) ageing the monocalcium phosphate solution containing the rare earth at 120 ℃ for 3h to separate the rare earth elements from the monocalcium phosphate solution in the form of rare earth phosphate precipitate, so that the monocalcium phosphate solution and 8.26g of rare earth phosphate precipitate are obtained through solid-liquid separation.

Through detection, the leaching rate of Fe in phosphorite is 4.7%, the leaching rate of Al is 3.8%, and the leaching rate of phosphorus element is 97.3%; the content of rare earth in the phosphoric acid rare earth precipitate is 56.3 percent, and the recovery rate of the rare earth is 93.01 percent.

Example 9

1000g of phosphorite with the rare earth content of 0.5 wt% is taken as a raw material, and phosphoric acid solution with the mass concentration of 30% (taking P as₂O₅Calculated) and hydrochloric acid mixed solution to leach the rare earth phosphate ore, wherein the hydrochloric acid accounts for 15 percent of the mixed acid by mole number of anions, and the liquid-solid ratio of the system is controlled to be 4: 1, reacting for 3 hours at 30 ℃, and filtering to obtain a monocalcium phosphate solution containing rare earth and acid leaching residue.

And (3) ageing the monocalcium phosphate solution containing the rare earth at 120 ℃ for 3h to separate the rare earth elements from the monocalcium phosphate solution in the form of rare earth phosphate precipitate, so that the monocalcium phosphate solution and 8.38g of rare earth phosphate precipitate are obtained through solid-liquid separation.

Through detection, the leaching rate of Fe in phosphorite is 4.9%, the leaching rate of Al is 4.6%, and the leaching rate of phosphorus element is 98.5%; the content of rare earth in the phosphoric acid rare earth precipitate is 56.8 percent, and the recovery rate of the rare earth is 95.20 percent.

Example 10

1000g of phosphorite with the rare earth content of 0.5 wt% is taken as a raw material, and phosphoric acid solution with the mass concentration of 40% (taking P as₂O₅Meter) and hydrochloric acid mixed solution to theLeaching rare earth phosphate ore, wherein the proportion of hydrochloric acid in the mixed acid is 25% in terms of the mole number of anions, and the liquid-solid ratio of the system is controlled to be 3: 1, reacting for 4 hours at 25 ℃, and filtering to obtain a monocalcium phosphate solution containing rare earth and acid leaching residue.

And (3) ageing the monocalcium phosphate solution containing the rare earth at 120 ℃ for 4 hours to separate the rare earth elements from the monocalcium phosphate solution in the form of rare earth phosphate precipitate, so that the monocalcium phosphate solution and 7.2g of rare earth phosphate precipitate are obtained through solid-liquid separation.

Through detection, the leaching rate of Fe in phosphorite is 5.0%, the leaching rate of Al is 5.0%, and the leaching rate of phosphorus element is 99.2%; the content of rare earth in the phosphoric acid rare earth precipitate is 55.9 percent, and the recovery rate of the rare earth is 80.50 percent.

Example 11

Taking 1000g of phosphorite containing 1 wt% of rare earth as a raw material, leaching the rare earth phosphorite by adopting a phosphoric acid solution with the mass concentration of 50%, and controlling the liquid-solid ratio of a system to be 2: 1, reacting for 0.5h at 60 ℃, and filtering to obtain a monocalcium phosphate solution containing rare earth and acid leaching residue.

And (3) aging the monocalcium phosphate solution containing the rare earth at 130 ℃ for 1h to separate the rare earth elements from the monocalcium phosphate solution in the form of rare earth phosphate precipitates, so that the monocalcium phosphate solution and 16.9g of rare earth phosphate precipitates are obtained through solid-liquid separation.

Through detection, the leaching rate of Fe in phosphorite is 8.0%, the leaching rate of Al is 6.0%, and the leaching rate of phosphorus element is 95.0%; the content of rare earth in the phosphoric acid rare earth precipitate is 47.8 percent, and the recovery rate of the rare earth is 80.78 percent.

Example 12

The method is characterized in that 1000g of phosphorite with the rare earth content of 7.4 wt% is used as a raw material, wherein the monazite content is 9.5 wt%, the rare earth phosphorite is leached by adopting a phosphoric acid solution with the mass concentration of 20%, and the liquid-solid ratio of a system is controlled to be 6: 1, reacting for 2 hours at 25 ℃, and filtering to obtain a monocalcium phosphate solution containing rare earth and 205.0g of acid leaching residue.

And (3) placing the monocalcium phosphate solution containing the rare earth at 100 ℃ for aging for 1h to separate out the rare earth element by using rare earth phosphate precipitation, and performing solid-liquid separation to obtain the monocalcium phosphate solution and 15.8g of rare earth phosphate precipitation.

Through detection, the leaching rate of impurity Fe in phosphorite is 3.3%, the leaching rate of impurity Al is 3.0%, and the leaching rate of phosphorus element is 96.5%; the content of rare earth in the phosphoric acid rare earth precipitate is 54.8 percent, and the recovery rate of the rare earth is 97.80 percent.

Example 13

1000g of phosphorite with the rare earth content of 7.4 wt% is used as a raw material, wherein the monazite content is 9.5 wt%, and a phosphoric acid solution (taking P) with the mass concentration of 15% is adopted₂O₅Calculated) and hydrochloric acid mixed solution to leach the rare earth phosphate ore, wherein the hydrochloric acid accounts for 10 percent of the mixed acid by mole number of anions, and the liquid-solid ratio of the system is controlled to be 10: 1, reacting for 8 hours at the temperature of 20 ℃, and filtering to obtain a monocalcium phosphate solution containing rare earth and 178.0g of acid leaching residue.

And (3) ageing the monocalcium phosphate solution containing the rare earth at 70 ℃ for 8h to separate the rare earth elements from the monocalcium phosphate solution in the form of rare earth phosphate precipitate, so that the monocalcium phosphate solution and 16.5g of rare earth phosphate precipitate are obtained through solid-liquid separation.

Through detection, the leaching rate of Fe in phosphorite is 4.4%, the leaching rate of Al is 4.2%, and the leaching rate of phosphorus element is 98.2%; the content of rare earth in the phosphoric acid rare earth precipitate is 52.8 percent, and the recovery rate of the rare earth is 98.10 percent.

Example 14

1000g of phosphorite with the rare earth content of 7.4 wt% is taken as a raw material, wherein the content of monazite is9.5 wt%, using a phosphoric acid solution (as P) with a mass concentration of 15%₂O₅Calculated) and hydrochloric acid mixed solution to leach the rare earth phosphate ore, wherein the hydrochloric acid accounts for 25 percent of the mixed acid by mole number of anions, and the liquid-solid ratio of the system is controlled to be 8: 1, reacting for 8 hours at the temperature of 20 ℃, and filtering to obtain a monocalcium phosphate solution containing rare earth and 154.0g of acid leaching residue.

And (3) ageing the monocalcium phosphate solution containing the rare earth at 70 ℃ for 12h to separate the rare earth elements from the monocalcium phosphate solution in the form of rare earth phosphate precipitate, so that the monocalcium phosphate solution and 17.3g of rare earth phosphate precipitate are obtained through solid-liquid separation.

Through detection, the leaching rate of Fe in phosphorite is 5.0%, the leaching rate of Al is 5.0%, and the leaching rate of phosphorus element is 98.9%; the content of rare earth in the phosphoric acid rare earth precipitate is 52.5 percent, and the recovery rate of the rare earth is 97.75 percent.

Example 15

1000g of phosphorite with the rare earth content of 9.0 wt% is used as a raw material, wherein the monazite content is 11.9 wt%, and a phosphoric acid solution (taking P) with the mass concentration of 15% is adopted₂O₅Calculated) and mixed solution of hydrochloric acid and nitric acid to leach the rare earth phosphate ore, wherein the mole number of anions is calculated, the proportion of hydrochloric acid in the mixed acid is 15%, the proportion of nitric acid in the mixed acid is 15%, and the liquid-solid ratio of a system is controlled to be 6: 1, reacting for 4 hours at the temperature of 20 ℃, and filtering to obtain a monocalcium phosphate solution containing rare earth and 167.0g of acid leaching residue.

And (3) placing the monocalcium phosphate solution containing the rare earth at 150 ℃ for aging for 0.5h to separate the rare earth elements from the monocalcium phosphate solution in the form of rare earth phosphate precipitates, and thus obtaining the monocalcium phosphate solution and 17.5g of rare earth phosphate precipitates through solid-liquid separation.

Through detection, the leaching rate of Fe in phosphorite is 4.8%, the leaching rate of Al is 4.5%, and the leaching rate of phosphorus element is 98.6%; the content of rare earth in the phosphoric acid rare earth precipitate is 53.5 percent, and the recovery rate of the rare earth is 98.50 percent.

Example 16

1000g of phosphorite with the rare earth content of 14.7 wt% is used as a raw material, wherein the monazite content is 20.5 wt%, and a phosphoric acid solution with the mass concentration of 25% (taking P as₂O₅Calculated) and hydrochloric acid mixed solution to leach the rare earth phosphate ore, wherein the hydrochloric acid accounts for 10 percent of the mixed acid by the mole number of anions, and the liquid-solid ratio of the system is controlled to be 3: 1, reacting for 2 hours at 15 ℃, and filtering to obtain a monocalcium phosphate solution containing rare earth and 258.0g of acid leaching residue.

And (3) placing the monocalcium phosphate solution containing the rare earth at 90 ℃ for aging for 2h to separate the rare earth elements from the monocalcium phosphate solution in the form of rare earth phosphate precipitate, and thus obtaining the monocalcium phosphate solution and 16.7g of rare earth phosphate precipitate through solid-liquid separation.

Through detection, the leaching rate of Fe in phosphorite is 3.8%, the leaching rate of Al is 2.9%, and the leaching rate of phosphorus element is 98.4%; the content of rare earth in the phosphoric acid rare earth precipitate is 55.7 percent, and the recovery rate of the rare earth is 98.30 percent.

Comparative example 1

Taking 1000g of phosphorite containing 0.3 wt% of rare earth as a raw material, leaching the rare earth phosphorite by adopting a hydrochloric acid solution with the mass concentration of 20%, and controlling the liquid-solid ratio of a system to be 6: 1, reacting for 4 hours at 30 ℃, and filtering to obtain a solution containing rare earth and acid leaching slag.

And (3) aging the solution containing the rare earth at 120 ℃ for 3h to separate out the rare earth elements in the form of rare earth phosphate precipitate, and performing solid-liquid separation to obtain 0.5g of rare earth phosphate precipitate.

Through detection, the leaching rate of impurity Fe in phosphorite is 68%, the leaching rate of impurity Al is 56%, and the leaching rate of phosphorus element is 99.5%; the content of rare earth in the phosphoric acid rare earth precipitate is 46.3 percent, and the recovery rate of the rare earth is 7.72 percent.

Comparative example 2

Using 1000g of phosphorite containing 0.3 wt% of rare earth as a raw material, leaching the rare earth phosphorite by adopting a phosphoric acid solution with the mass concentration of 30%, and controlling the liquid-solid ratio of a system to be 4: 1, reacting for 3 hours at the temperature of 100 ℃, and filtering to obtain monocalcium phosphate solution and 65.8g of acid leaching residue.

Through detection, the leaching rate of the impurity Fe in the phosphorite is 54.2 percent, the leaching rate of the impurity Al is 43.7 percent, the leaching rate of the phosphorus element is 96.7 percent, and the recovery rate of the rare earth is 96.7 percent.

As can be seen from the comparison of the above examples 1 to 16 with the comparative examples 1 and 2, the method of the present invention has high separation efficiency of phosphorus and rare earth elements, and can obtain high recovery rates of rare earth elements and phosphorus elements. Moreover, as can be seen from examples 1 to 11, at a relatively low reaction temperature, rare earth phosphate ore is leached by using a solution containing phosphoric acid, the reaction temperature has a small influence on leaching of phosphorus in the acid leaching process, and the solubility of rare earth phosphate at a relatively low temperature is high, which is beneficial to leaching of rare earth, and simultaneously, the leaching of impurity elements such as iron and aluminum in the phosphate ore can be effectively inhibited at a low temperature, so that the leaching rate of the iron element and the aluminum element is less than 5%, the burden of purification and impurity removal of subsequent phosphoric acid is greatly reduced, and the rare earth grade of rare earth phosphate precipitate obtained in the subsequent aging process is improved. And the hydrochloric acid or nitric acid in the mixed acid solution is beneficial to the decomposition of the apatite, thereby improving the leaching rate of the phosphorus and the rare earth in the apatite. The rare earth-containing monocalcium phosphate solution is further aged, so that rare earth elements contained in the solution can form rare earth phosphate precipitates, and the separation of the rare earth elements and phosphorus elements is realized. In addition, the yield and the rare earth grade of the rare earth are favorably improved by controlling the higher aging temperature, the product of the solubility of the rare earth phosphate is small at high temperature, and the rare earth element in the leachate is favorably precipitated in the form of rare earth phosphate, so that the effective separation of the rare earth element and the phosphorus element is realized. From examples 12 to 16, it can be seen that when the rare earth phosphorite contains monazite, the separation of phosphorus and monazite is realized by utilizing the fact that the monazite is not dissolved in the acid leaching process and enters the slag for enrichment. The rare earth entering the solution is precipitated and separated out by rare earth phosphate through aging treatment, and the rare earth is recovered together after the rare earth phosphate and monazite which is not dissolved in the acid leaching process form rare earth mixed slag, so that the recovery steps are simplified, the recovery rate of the rare earth is improved, and the aim of comprehensively recovering the rare earth at low cost is fulfilled.

In addition, the inventor further mixes the acid leaching residue and the rare earth phosphate precipitate in the embodiment 13 to obtain rare earth mixed residue, and takes 15g of the rare earth mixed residue to recycle rare earth elements, and the specific recycling steps are shown in the following embodiments 17 to 23.

Example 17

Adding iron-containing slag according to the phosphorus content in the mixed slag, and controlling the Fe/P mass ratio to be 2.5: 1, adding concentrated sulfuric acid with the mass concentration of 98% for mixing, wherein the mass ratio of the concentrated sulfuric acid to the rare earth mixed slag is 1: 1;

roasting the mixture at 200 ℃ to obtain a roasted product;

adding water to the roasted product for leaching to obtain rare earth-containing water leaching solution and water leaching slag;

adjusting the pH value of the rare earth-containing water leaching solution to 4.0 by using magnesium oxide, filtering to obtain a rare earth sulfate solution and filter residues, wherein the filter residues contain ferric phosphate and thorium phosphate precipitates; the content of Fe is 0.02g/L, the content of P is 0.005g/L and the content of Th is less than 0.05mg/L in the sulfuric acid rare earth solution calculated by oxide;

extracting and separating the rare earth sulfate solution by using an acidic phosphorus extractant to obtain a mixed rare earth chloride compound or a single rare earth compound; wherein, the yield of the rare earth is 92.5 percent.

Example 18

Adding iron-containing slag according to the phosphorus content in the mixed slag, and controlling the Fe/P mass ratio to be 2.5: 1, adding concentrated sulfuric acid with the mass concentration of 95% and mixing; the mass ratio of concentrated sulfuric acid to rare earth mixed slag is 1: 1;

roasting the mixture at 250 ℃ to obtain a roasted product;

adjusting the pH value of the rare earth-containing water leaching solution to 4.0 by using magnesium oxide, filtering to obtain a rare earth sulfate solution and filter residues, wherein the filter residues contain ferric phosphate and thorium phosphate precipitates; the content of Fe is 0.03g/L, the content of P is 0.004g/L and the content of Th is less than 0.05mg/L in the sulfuric acid rare earth solution calculated by oxides;

adding carbonate to the sulfuric acid rare earth solution to precipitate rare earth and obtain a rare earth carbonate product, wherein the recovery rate of the rare earth in the whole process is 94.1%.

Example 19

Adding iron-containing rare earth tailings and dolomite according to the phosphorus content in the mixed slag, and controlling the Fe/P mass ratio to be 2.5: 1, the molar ratio of Mg and Ca elements to F elements in the dolomite is 1: and 2, adding concentrated sulfuric acid with the mass concentration of 99% for mixing, wherein the mass ratio of the concentrated sulfuric acid to the rare earth mixed slag is 1: 1;

roasting the mixture at 500 ℃ to obtain a roasted product;

adjusting the pH value of the rare earth-containing water leaching solution to 4.0 by using magnesium oxide, filtering to obtain a rare earth sulfate solution and filter residues, wherein the filter residues contain ferric phosphate and thorium phosphate precipitates; the content of Fe is 0.05g/L, the content of P is 0.004g/L and the content of Th is less than 0.04mg/L in the sulfuric acid rare earth solution calculated by oxides;

extracting and separating the rare earth sulfate solution by using an acidic phosphorus extractant to obtain a mixed rare earth chloride compound or a single rare earth compound; wherein, the yield of the rare earth is 95.8 percent.

Example 20

Adding iron-containing rare earth tailings and dolomite according to the phosphorus content in the mixed slag, and controlling the Fe/P mass ratio to be 2: 1, the molar ratio of Mg and Ca elements to F elements in the dolomite is 1.5: 2, adding concentrated sulfuric acid with the mass concentration of 99% and mixing; the mass ratio of the concentrated sulfuric acid to the rare earth mixed slag is 1.5: 1;

roasting the mixture at 350 ℃ to obtain a roasted product;

adjusting the pH value of the rare earth-containing water leaching solution to 4.5 by using magnesium oxide, filtering to obtain a rare earth sulfate solution and filter residues, wherein the filter residues contain ferric phosphate and thorium phosphate precipitates; the content of Fe is 0.008g/L, the content of P is 0.004g/L and the content of Th is less than 0.05mg/L in the sulfuric acid rare earth solution calculated by oxide;

wherein, the yield of the rare earth in the sulfuric acid rare earth solution is 94.2 percent.

Example 21

Adding iron-containing rare earth tailings and dolomite according to the phosphorus content in the mixed slag, and controlling the Fe/P mass ratio to be 4: 1, the molar ratio of Mg and Ca elements to F elements in the dolomite is 1.5: 2, adding concentrated sulfuric acid with the mass concentration of 99% and mixing; the mass ratio of the concentrated sulfuric acid to the rare earth mixed slag is 1.5: 1;

roasting the mixture at 350 ℃ to obtain a roasted product;

adjusting the pH value of the rare earth-containing water leaching solution to 4.5 by using light-burned dolomite, filtering to obtain a rare earth sulfate solution and filter residues, and precipitating iron phosphate and thorium phosphate in the filter residues; the content of Fe is 0.01g/L, the content of P is 0.007g/L and the content of Th is less than 0.04mg/L in the sulfuric acid rare earth solution calculated by oxides;

wherein, the yield of the rare earth in the sulfuric acid rare earth solution is 97.3 percent.

Example 22

Adding iron-containing rare earth tailings and dolomite according to the phosphorus content in the mixed slag, and controlling the Fe/P mass ratio to be 3.5: 1, the molar ratio of Mg and Ca elements to F elements in the dolomite is 1: 1, then adding concentrated sulfuric acid with the mass concentration of 99%, wherein the mass ratio of the concentrated sulfuric acid to the rare earth mixed slag is 2: 1;

roasting the mixture at 400 ℃ to obtain a roasted product;

adjusting the pH value of the rare earth-containing water leaching solution to 3.8 by using magnesium hydroxide, filtering to obtain a rare earth sulfate solution and filter residues, and precipitating iron phosphate and thorium phosphate in the filter residues; the content of Fe is 0.04g/L, the content of P is 0.002g/L and the content of Th is less than 0.05mg/L in the sulfuric acid rare earth solution calculated by oxide;

wherein, the yield of the rare earth in the sulfuric acid rare earth solution is 97.5 percent.

Example 23

Adding iron-containing slag and dolomite according to the phosphorus content in the mixed slag, and controlling the Fe/P mass ratio to be 3: 1, the molar ratio of Mg and Ca elements to F elements in the dolomite is 1.5: 2, adding concentrated sulfuric acid with the mass concentration of 99% and mixing; the mass ratio of the concentrated sulfuric acid to the rare earth mixed slag is 1.5: 1;

roasting the mixture at 450 ℃ to obtain a roasted product;

wherein, the yield of the rare earth in the sulfuric acid rare earth solution is 96.1 percent.

From the above description, it can be seen that the above-described embodiments of the present application achieve the following technical effects: the method comprises leaching rare earth phosphorite with phosphoric acid-containing solution, dissolving phosphorus in the phosphorite to form monocalcium phosphate by using hydrogen ions in the phosphoric acid-containing solution, and dissolving rare earth elements into the solution to form a solution containing rare earth ions and Ca²⁺And H₂PO₄ ^-The leaching solution is further aged, so that rare earth ions in the leaching solution can form rare earth phosphate precipitates to separate rare earth elements from phosphorus elements. In addition, the temperature of the aging treatment is controlled to be higher than the temperature of the acid leaching step, so that the leaching of impurity elements such as iron, aluminum and the like in rare earth phosphorite can be effectively inhibited at low temperature, and the leaching rate of the iron element and the aluminum element is ensured<5 percent, thereby greatly lightening the subsequent impurity removal burden; the rare earth phosphate has small solubility product at high temperature, and is favorable for precipitating the rare earth elements dissolved in the leaching solution in the form of rare earth phosphate, thereby further realizing the effective separation of the rare earth elements and the phosphorus elements. When the rare earth phosphorite contains monazite, the monazite is not dissolved and remains in the slag in the acid leaching process, thereby realizing the separation of rare earth elements and phosphorus elements. Then, the rare earth phosphate precipitate is mixed with acid leaching residue containing rare earth generated in the acid leaching process to form rare earth mixed residue. The separation method improves the rare earth separation efficiency, ensures that the rare earth content in the phosphoric acid rare earth precipitation and the rare earth mixed slag is high, realizes the purpose of separating the rare earth with low cost, and is convenient for further recycling the rare earth elements.

The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for recovering phosphorus and rare earth from rare earth-containing phosphorite, characterized in that the method comprises:

step S1, leaching the rare earth phosphorite by using a solution containing phosphoric acid to obtain a leachate and acid leaching slag, wherein the leachate contains rare earth ions and Ca²⁺And H₂PO₄ ^-(ii) a And

step S2, aging the leachate to obtain rare earth phosphate precipitate and monocalcium phosphate solution; wherein,

the reaction temperature of the step S1 is between 10 ℃ and 60 ℃, the reaction temperature of the step S2 is between 60 ℃ and 150 ℃, and the reaction temperature of the step S2 is higher than the reaction temperature of the step S1.

2. The method according to claim 1, wherein the step S1 includes:

leaching the rare earth phosphorite for 0.5-8 hours by using the solution containing phosphoric acid to obtain the leachate and the acid leaching residue.

3. The method according to claim 1, wherein the step S1 includes:

leaching the rare earth phosphorite for 1-4 hours by using the solution containing phosphoric acid to obtain the leachate and the acid leaching residue.

4. The method according to any one of claims 1 to 3, wherein the step S2 includes:

and aging the leachate at the temperature of 80-120 ℃ for 0.5-24 hours to obtain the rare earth phosphate precipitate and the monocalcium phosphate solution.

5. The method according to any one of claims 1 to 3, wherein the step S2 includes:

and aging the leachate at the temperature of 80-120 ℃ for 1-8 hours to obtain the rare earth phosphate precipitate and the monocalcium phosphate solution.

6. The method of claim 1, wherein when the rare earth phosphate ore is free of monazite, the method further comprises:

recovering rare earth elements in the rare earth phosphate precipitate; and

and recovering the phosphorus element in the monocalcium phosphate solution.

7. The method of claim 1, wherein when the rare earth phosphate ore contains monazite, the method further comprises:

mixing the acid leaching residue with the phosphoric acid rare earth precipitate to obtain rare earth mixed residue;

recovering rare earth elements in the rare earth mixed slag; and

and recovering the phosphorus element in the monocalcium phosphate solution.

8. The method of claim 6 or 7, wherein the step of recovering elemental phosphorus from the monocalcium phosphate solution comprises:

adding concentrated sulfuric acid with the mass concentration of more than 90% into the monocalcium phosphate solution to obtain a solid-liquid mixture;

and carrying out solid-liquid separation on the solid-liquid mixture to obtain a first phosphoric acid solution and calcium sulfate.

9. The method as claimed in claim 8, wherein the step of recovering the phosphorus element from the monocalcium phosphate solution further comprises, after obtaining the first phosphoric acid solution:

returning the first phosphoric acid solution to the step S1 to leach the rare earth phosphorite; or

And removing impurities from the first phosphoric acid solution to obtain a second phosphoric acid solution, returning the second phosphoric acid solution to the step S1, and leaching the rare earth phosphorite.

10. The method according to claim 7, wherein the step of recovering the rare earth element in the rare earth slag mixture comprises:

step A, adding an iron-containing substance into the rare earth mixed slag, and adding concentrated sulfuric acid with the mass concentration of more than 90% to obtain a mixture;

b, roasting the mixture to obtain a roasted product;

step C, adding water to the roasted product for leaching to obtain rare earth-containing water leaching solution and water leaching slag;

d, adjusting the pH value of the rare earth-containing water leaching solution to 3.8-5, and filtering to obtain a rare earth sulfate solution and filter residues, wherein the filter residues contain iron elements, phosphorus elements and thorium elements; and

step E, preparing a rare earth compound by taking the sulfuric acid rare earth solution as a raw material,

wherein the step E comprises:

extracting and separating the rare earth sulfate solution by using an acidic phosphorus extractant to obtain a mixed chlorinated rare earth compound or a single rare earth compound; or

Adding carbonate or oxalate into the sulfuric acid rare earth solution to precipitate rare earth elements to obtain rare earth carbonate or rare earth oxalate; and calcining the rare earth carbonate or the rare earth oxalate to obtain the rare earth oxide.

11. The method of claim 1, wherein the phosphoric acid-containing solution further comprises hydrochloric acid and/or nitric acid.

12. Method according to claim 1 or 11, characterized in that P is used₂O₅The mass concentration of the phosphoric acid in the phosphoric acid-containing solution is 15-50%.

13. Method according to claim 1 or 11, characterized in that P is used₂O₅The mass concentration of the phosphoric acid in the phosphoric acid-containing solution is 15-30%.

14. The method according to claim 11, characterized in that the solution containing phosphoric acid has a hydrochloric acid and/or nitric acid content of < 30% by moles of anions.

15. The method according to claim 11, wherein the phosphoric acid-containing solution contains hydrochloric acid and/or nitric acid in an amount of 2 to 15% by mole based on the anion.

16. The method according to claim 1, wherein before the step S1, the method further comprises: and (3) mixing the solution containing phosphoric acid and the rare earth phosphate ore according to a liquid-solid ratio of 2-10L: mixing was carried out at a ratio of 1 kg.

17. The method according to claim 16, wherein the liquid-solid ratio is 3-6L: 1 kg.