AU2016200606B2 - A method for recovering phosphorus and rare earth from rare earth containing phosphorite - Google Patents

A method for recovering phosphorus and rare earth from rare earth containing phosphorite Download PDF

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AU2016200606B2
AU2016200606B2 AU2016200606A AU2016200606A AU2016200606B2 AU 2016200606 B2 AU2016200606 B2 AU 2016200606B2 AU 2016200606 A AU2016200606 A AU 2016200606A AU 2016200606 A AU2016200606 A AU 2016200606A AU 2016200606 B2 AU2016200606 B2 AU 2016200606B2
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rare earth
solution
phosphorus
slag
phosphorite
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AU2016200606A1 (en
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Jinshi DONG
Zongyu FENG
Xiaowei Huang
Zhiqi Long
Xu SUN
Liangshi Wang
Shengxi Wu
Longsheng ZHAO
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Grirem Advanced Materials Co Ltd
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    • CCHEMISTRY; METALLURGY
    • C22METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22BPRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
    • C22B59/00Obtaining rare earth metals
    • CCHEMISTRY; METALLURGY
    • C01INORGANIC CHEMISTRY
    • C01BNON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B25/00Phosphorus; Compounds thereof
    • C01B25/16Oxyacids of phosphorus; Salts thereof
    • C01B25/18Phosphoric acid
    • C01B25/22Preparation by reacting phosphate-containing material with an acid, e.g. wet process
    • C01B25/222Preparation by reacting phosphate-containing material with an acid, e.g. wet process with sulfuric acid, a mixture of acids mainly consisting of sulfuric acid or a mixture of compounds forming it in situ, e.g. a mixture of sulfur dioxide, water and oxygen
    • CCHEMISTRY; METALLURGY
    • C22METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22BPRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
    • C22B3/00Extraction of metal compounds from ores or concentrates by wet processes
    • C22B3/04Extraction of metal compounds from ores or concentrates by wet processes by leaching
    • C22B3/06Extraction of metal compounds from ores or concentrates by wet processes by leaching in inorganic acid solutions, e.g. with acids generated in situ; in inorganic salt solutions other than ammonium salt solutions
    • CCHEMISTRY; METALLURGY
    • C22METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22BPRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
    • C22B3/00Extraction of metal compounds from ores or concentrates by wet processes
    • C22B3/04Extraction of metal compounds from ores or concentrates by wet processes by leaching
    • C22B3/06Extraction of metal compounds from ores or concentrates by wet processes by leaching in inorganic acid solutions, e.g. with acids generated in situ; in inorganic salt solutions other than ammonium salt solutions
    • C22B3/10Hydrochloric acid, other halogenated acids or salts thereof
    • YGENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02PCLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P10/00Technologies related to metal processing
    • Y02P10/20Recycling

Abstract

The present disclosure discloses a method for recovering phosphorus and rare earth from rare earth containing phosphorite. The method includes the following steps: leaching a rare earth containing phosphorite by using a mixed acid solution, and filtering and obtaining a mono-calcium phosphate solution and a rare earth phosphate containing slag, the main component of the mixed acid solution is a phosphoric acid and the mixed acid solution further comprises a hydrochloric acid and/or a nitric acid; recovering the phosphorus of the mono-calcium phosphate solution, and recovering the rare earth of the rare earth phosphate containing slag. The method leaches the rare earth containing phosphorite by using the mixed acid solution so that the phosphorus in the phosphorite forms the higher soluble mono-calcium phosphate, at the same time by regulating and controlling the acidity in the leaching process to precipitate and enrich the rare earth in the form of a rare earth phosphate in the slag, if the rare earth containing phosphorite further contains a monazite, the monazite and the rare earth phosphate are enriched in the slag, thereby separating the phosphorus and the rare earth, simplifying recovery steps, improving the recovery rate of the rare earth, and achieving the purpose of comprehensive recovery of the rare earth with low cost. 37 Rare earth containing phosphorite Phosphoric acid solution+hydroc Leaching •••••••••••••••••••••••••••• hioric acid/nitric acid Filtration Rare eart hosphate Monocalcium Iron-containing contain sla hoshatesolution compound .l | Magnesium/calcium- S r 7 acid containing compound Enhanced bake Filtration Concentrated sulfuric acid Waterleaching Phosphorus Gypsum containing Carbonate/oxalate solution r rare earth Solvent precipitation extraction Impurities removal rare earth rare earth chloride carbonate/ oxalate Phosphorus product Fig. 1 38

Description

Rare earth containing phosphorite
Phosphoric acid solution+hydroc Leaching •••••••••••••••••••••••••••• hioric acid/nitric acid
Filtration
Rare eart hosphate Monocalcium Iron-containing contain sla hoshatesolution compound .l | Magnesium/calcium- containing compound 7 S r acid Enhanced bake Filtration
Concentrated sulfuric acid Waterleaching Phosphorus Gypsum containing Carbonate/oxalate solution r rare earth Solvent precipitation extraction Impurities removal
rare earth rare earth chloride carbonate/ oxalate Phosphorus product
Fig. 1
Technical field The present disclosure 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 usually coexist with minerals including barite, calcite, apatite, silicate minerals and so on in nature. Due to different mineral genesis, rare earth elements also occur in different states with different contents in minerals. Generally, the grade of rare earth oxides in rare earth minerals mined currently is several percent. To satisfy demands of rare earth metallurgy and production, it is necessary to separate rare earth from other ores by ore sorting dressing method before smelting so as to enrich rare earth minerals to satisfy demands of rare earth metallurgy and production. Usually, the content of rare earth oxides in a rare earth headings is 50% to 70% after ore dressing and enrichment. Major rare earth minerals include bastnaesite, monazite, xenotime and ion-adsorpted rare earth ores and so on. At present, rare earth in monazite is mainly recovered by the following two methods : (1) the monazite is decomposed and processed by an alkaline method (applicable to a high grade monazite ore), and during a reaction process of the monazite and liquid alkali, water insoluble hydroxides are generated from the rare earth, phosphorus is transformed into trisodium phosphate, and the rare earth hydroxides are further subjected to hydrochloric acid selective dissolution and impurity removal to obtain mixed rare earth chlorides. Colloidal substances including sodium silicate, ferric hydroxide and so on will be formed easily if abundant impurities including iron, silicon and so on are contained in a headings, and processes including precipitation, filtering and separation can be hardly implemented, and thus the process cannot be operated normally. (2) a mann ~ ~ A- - nr I- -4-~A,. &-an~n -nn44-n -,4k-A . . -- aanaa ; nf l -- 4 4 -. .... -a acid, a monazite concentrate is mixed with the concentrated sulfuric acid in an use amount accounting for 1.7 to 2 times the weight of the headings, and is decomposed at 200°C to 230°C, a decomposition product is cooled and then leached by using water which is 7 to 10 times the weight of the headings, a leaching solution having an acidity of 2.5mol/L contains about 50g/L (REO)of rare earth, 25g/L of P205 and 2.5g/L of Fe203. The leaching solution is highly acidic with a high content of impurities including phosphorus and thorium, the rare earth and the thorium are precipitated by using a sodium sulfate double salt, and then transformed into hydroxides by an alkali, subsequently, the rare earth is leached preferentially by using an acid, and the rare earth and the thorium are extracted and separated. The method has a complicated and discontinuous process, many liquid-solid separation steps, and a low rare earth recovery rate; besides, the acids and the alkali are used alternately, thus chemical materials are consumed at a high cost, the phosphorus enters waste water to result in high processing difficulty, and it is difficult to effectively recover the radioactive element thoriumdispersed in a slag and the waste water. Phosphorite is a main raw material in production of a phosphorus chemical product, the reserves of phosphorite resources is large around the world , and the phosphorite usually accompanied with trace rare earth. At present, methods for recovering rare earth in phosphorite include the following processes: (1) A wet process phosphoric acid technique for processing phosphorite with hydrochloric acid , nitric acid, in which more than 95% of rare earth enters a solution, and is then recovered by means of solvent extraction, ion exchange, precipitation, crystallization and so on; (2) A wet process phosphoric acid technique for processing phosphorite with sulfuric acid, in which rare earth enters a solution and phosphor gypsum respectively, and the phosphogy psum is then leached by sulfuric acid so that rare earth enters a solution, and the rare earth in the solution may be recovered by means of 4 -- k -n - ;-- - 6 - n- L m .- -.. m :4.,4.- 4--.~ m -a -fnI... 44 -4 -nr n -n V N A technique for processing phosphorite with phosphoric acid, In patent CN201110143415.0, a rare earth containing phosphate headings and a phosphoric acid solution are mixed carry out a reaction, and a technical condition is controlled to precipitate rare earth in the phosphorite in the form of fluorides, more than 85% of the rare earth is enters a slag, and then the rare earth in the slag is dissolved and recovered by hydrochloric acid, nitric acid or sulfuric acid, however, the slag has a grade as low as about 1% of rare earth, and contains abundant impurities including phosphorus, calcium, aluminum, silicon and so on, and the rare earth fluorides are hardly dissolved by using acid, thereby resulting in high acid consumption, a large amount of the slag, and a low recovery rate of the rare earth, besides, 15% of rare earth in a leaching liquid enters a gypsum slag easily during a calcium removal process, and is thus difficult to be recovered. Phosphorite containing monazite and rare earth is an ore that can be hardly disposed and contains many components including monazite, rare earth, phosphorite and so on. Monazite and phosphorite, which are phosphate minerals, have close mineralogical properties, and usually disseminate closely in an ore in which the monazite and the phosphorite coexist. Since it is difficult to dissociate each substance for they are coated and embedded in the mixed ore, it is hard to separate the ore effectively by physical dressing when rare earth elements and the phosphorus element are recovered. Especially, since strict conditions are required for decomposing the monazite, and a relatively high temperature and pH value and so on are required, the monazite cannot be fully decomposed in most cases when the monazite containing phosphorite is disposed by a wet sulfuric acid process in the prior art, and the monazite cannot be recovered and utilized effectively. Therefore, it has become a new subject for researchers and developers to recover phosphorus and rare earth in rare earth containing phosphorite, especially rare earth in such a low quality ore as the monazite and rare earth containing phosphorite that has nm linfnerJ minn.-nl nnnwane,
Summary The present disclosure aims to provide a method for recovering phosphorus and rare earth from a rare earth containing phosphorite so as to improve the recovery rates of the rare earth and the phosphorus and achieve the purpose of comprehensive recovery of the rare earth with low cost. To achieve the above mentioned purposes, a method for recovering phosphorus and rare earth from a rare earth containing phosphorite in the present disclosure. The method includes the following steps: leaching the rare earth containing phosphorite by using a mixed acid solution, and filtering and obtaining a mono-calcium phosphate solution and a rare earth phosphate containing slag, the main component of the mixed acid solution is a phosphoric acid and the mixed acid solution further comprises a hydrochloric acid and/or a nitric acid; recovering the phosphorus of the mono-calcium phosphate solution, and recovering the rare earth of the rare earth phosphate containing slag. In particular, the present invention provides a method for recovering phosphorus and rare earth from a rare earth containing phosphorite comprising the following steps: leaching the rare earth containing phosphorite at a leaching temperature of 70 0C to 1500C and for a leaching time is 0.5 to 8 hours using a mixed acid solution, filtering and obtaining a mono-calcium phosphate solution and a rare earth phosphate containing slag, wherein the main component of the mixed acid solution is a phosphoric acid and the mixed acid solution further comprises a hydrochloric acid and/or a nitric acid; recovering (i) the phosphorus of the mono-calcium phosphate solution, and (ii) the rare earth of the rare earth phosphate containing slag. Further, the rare earth containing phosphorite contains a monazite. Further, based on the molar number of anions, the proportion of the hydrochloric acid and/or the nitric acid in the mixed acid solution is 1% to 30%, preferably 2% to 15%. Further, the mass fraction of P205 in the mixed acid solution is 15% to %, preferably 15% to 30%. Further, in the step of leaching the rare earth containing phosphorite by using the mixed acid solution, the mixed acid solution and the rare earth containing phosphorite are mixed at a liquid-to-solid ratio of 2L to 10L: 1kg, preferably 4L to 8L: 1kg. Further, in the step of leaching the rare earth containing phosphorite by using the mixed acid solution, a leaching temperature is 55 to 150 0C, preferably 60 to 90°C and a leaching time is 0.5 to 8 hours, preferably 2 to 5 hours. Further, the step of recovering the phosphorus of the mono-calcium phosphate solution includes: adding a sulfuric acid into the mono-calcium phosphate solution, performing solid-liquid separation and obtaining a phosphorus containing solution and a calcium sulfate gypsum, and then recovering the phosphorus of the phosphorus containing solution. Further, the step of recovering the phosphorus of the mono-calcium phosphate solution further includes: preparing a phosphoric acid from a portion of the phosphorus containing solution after impurities removal, then recycling the prepared phosphoric acid containing hydrochloric acid or nitric acid to the leaching step. Further, the step of recovering the rare earth of the rare earth phosphate containing slag includes: adding an iron containing compound, a compound containing magnesium and/or calcium into the rare earth phosphate containing slag, then mixing with a concentrated sulfuric acid, with subsequent enhanced bake to obtain a calcination slag; leaching the calcination slag by water to obtain a rare earth containing water leach solution and an water leach slag; adjusting the pH value of the rare earth containing water leach solution to 3.8 to 5, filtering and obtaining a rare earth sulfate solution and a slag containing iron and thorium; adding a carbonate or an oxalate into the rare earth sulfate solution to precipitate the rare earth, and obtaining a rare earth carbonate or a rare earth oxalate, calcining the rare earth carbonate and the rare earth oxalate to obtain a rare earth oxide, or extracting the rare earth sulfate solution by using an acidic phosphorus extractant to obtain a mixed rare earth chloride or single rare earth compounds. Further, the compound containing magnesium and/or calcium is at least one of an oxide of magnesium and/or calcium, a carbonate of magnesium and/or calcium or a mineral containing magnesium and/or calcium, preferably the mineral containing magnesium and/or calcium is at least one of dolomite, magnesite; the iron containing compound is at least one of an iron containing tailing and an iron containing slag, preferably a tailing containing rare earth and iron.
Further, the molar ratio of the magnesium and/or calcium of the compound containing magnesium and/or calcium to the fluorine of the rare earth phosphate containing slag is 1 to 2: 2. Further, the mass ratio of the iron of the iron containing compound to the phosphorus of the rare earth phosphate containing slag is 2 to 4: 1, preferably 2.5 to 3.5: 1. Further, during the enhanced bake, the concentrated sulfuric acid and the rare earth phosphate containing slag are mixed at a mass ratio of 1 to 2: 1, and the bake temperature during enhanced bake is 200 °C to 500 °C, preferably 250 °C to 400 °C. Further, in the step of adjusting the pH value of the rare earth containing water leach solution, the pH value of the rare earth containing water leach solution is adjusted by using a magnesium oxide and/or a caustic calcined dolomite, and the pH value of the rare earth containing water leach solution is adjusted to 4 to 4.5. By applying the technical solution of the present disclosure, the present disclosure leaches a rare earth containing phosphorite by using a mixed acid solution, so that the phosphorus in the phosphorite forms a highly-soluble mono-calcium phosphate with higher solubility, at the same time by regulating and controlling the acidity in the leaching process to precipitate and enrich the rare earth in the form of a rare earth phosphate in a slag, if the rare earth containing phosphorite further contains a monazite, the monazite and the rare earth phosphate are enriched in the slag, thereby separating the phosphorus and the rare earth. A hydrochloric acid or a nitric acid in the mixed acid solution is propitious to decompose apatite while ensuring that the rare earth is enriched in the slag in the form of a rare earth phosphate precipitate, thereby improving the leaching rate of the phosphorus in the apatite. Besides, the hydrochloric acid or the nitric acid can provide hydrogen ions H+, and can reduce the content of phosphate radicals and the viscosity of the system with the same acid content, thus facilitating leaching of the phosphorus; in the meanwhile, the existence of the chloride ions or the nitrate ions is propitious to increase the solubility of calcium ions in a solution and decomposition of the apatite. The rare earth and the phosphorus element can be separated effectively by a filtering process, thus improving the recovery rates of the rare earth and the phosphorus. At the same time, the rare earth enters the slag in the form of the rare earth phosphate, and is enriched with the insoluble monazite during the acid leaching process so as to recover the rare earth, thereby simplifying recovery steps, improving the recovery rate of the rare earth, and achieving the purpose of comprehensive recovery of the rare earth with low cost.
Brief description The accompanying drawings of the specification, which constitute a part of the present application, are used for providing further understanding to the present disclosure. The schematic embodiments of the present disclosure and description thereof are used for explaining the present disclosure, instead of forming improper limitation to the present disclosure. In the accompanying drawings: Fig. 1 shows the flowchart of a method for recovering phosphorus and rare earth from a rare earth containing phosphorite according to an embodiment of the present disclosure.
Detailed description It needs to be noted that the embodiments in the present application and the characteristics in the embodiments may be combined with each other if there is no conflict. The present disclosure will be expounded hereinafter with reference to the accompanying drawings and in conjunction with the embodiments. In the following description, the molar cular formula of monazite is (Ln, Th)
P0 4 , where the Ln refers to at least one of rare earth elements except for promethium. As pointed out in the background art, the rare earth containing phosphorite has a lower rare earth grade and high impurities of phosphorus, the calcium and so on, thus it is difficult to efficiently separate the phosphorus and the calcium from the rare earth. It is more difficult to recover the phosphorus and the rare earth from a mixed phosphate mineral ore of a plurality of minerals including the apatite, the monazite and so on especially, the monazite and the phosphorite, which are phosphate minerals, have close mineralogical properties, and usually disseminate closely in the ore in which the monazite and the phosphorite coexist, thus the phosphorus and the rare earth in such a mixed ore of a plurality of minerals including the apatite, the monazite and so on are more difficult to recover. To solve the above-mentioned technical problems, a method for recovering a phosphorus and a rare earth from a rare earth containing phosphorite is provided in an embodiment of the present disclosure. As shown in Fig. 1, the method includes the following steps: leaching the rare earth containing phosphorite by using a mixed acid solution, filterating and obtaining a mono-calcium phosphate solution and a rare earth phosphate containing slag, the main component of the mixed acid solution is a phosphoric acid and the mixed acid solution further comprises a hydrochloric acid and/or a nitric acid; recovering the phosphorus in the mono-calcium phosphate solution, and recovering the rare earth in the rare earth phosphate containing slag. The method leaches the rare earth containing phosphorite by using the mixed acid solution , and forms the highly-soluble mono-calcium phosphate with the phosphorus in the phosphorite by using hydrogen ions in the mixed acid solution, at the same time by regulating and controlling the acidity in the leaching process to precipitate and enrich the rare earth in the form of a rare earth phosphate in the slag, if the rare earth containing phosphorite further contains a monazite, the monazite cannot be dissolved during the acid leaching process and enters into the slag together with the rare earth phosphate, so as to separate the phosphorus from the monazite and the rare earth. The hydrochloric acid or the nitric acid in the mixed acid solution induces the decomposition of the apatite while ensuring that the rare earth is enriched in the slag in the form of a rare earth phosphate precipitate, thereby increasing the leaching rate of the phosphorus in the apatite. Besides, the hydrochloric acid or the nitric acid can provide hydrogen ions H+, and can reduce the content of phosphate radicals and the viscosity of the system with the same acid content, thus facilitating leaching of the phosphorus; in the mean while, the existence of chloride ions or nitrate ions is propitious to increase the solubility of calcium ions in a solution and decomposition of the apatite. The rare earth and the phosphorus element in the rare earth containing phosphorite can be separated effectively by a filtering process, thus increasing the recovery rates of the rare earth and the phosphorus. At the same time, the rare earth enters the slag in the form of the rare earth phosphate to form the rare earth phosphate containing slag with the insoluble monazite during the acid leaching process and then the rare earth is recovered collectively, thereby simplifying recovery steps, increasing the recovery rate of the rare earth, and achieving the purpose of comprehensive recovery of the rare earth with low cost. Applying the method above, the mono-calcium phosphate with higher solubility is formed by performing the leaching using the mixed acid solution, and the addition of the hydrochloric acid or the nitric acid induces the decomposition of the apatite, thereby improving the decomposition rate of the phosphorite and the yield of the phosphorus and reducing the slag rate. By means of regulating and controlling the leaching process, more than 95% of phosphorus in the apatite will enter into the solution, the rare earth is enriched in the slag to form the rare earth phosphate containing slag while ensuring a high phosphorus leaching rate, and more than 95% of rare earth in the mineral is enriched in the rare earth phosphate containing slag, the grade of rare earth in the mixed slag is significantly improved, and it is conductive to recovering the rare earth subsequently. The aim of the leaching using the mixed acid solution in the present disclosure is to dissolve the phosphorus in the rare earth containing phosphorite while keeping the rare earth in the slag to form the rare earth phosphate containing slag. In a preferred embodiment of the present disclosure, the rare earth containing phosphorite further contains a monazite, the monazite cannot be decomposed and remains in the slag to be enriched with the rare earth phosphate, the use amount of the acid is reduced. Preferably, in the step of leaching by using the mixed acid solution, the mixed acid solution and the rare earth containing phosphorite are mixed with a liquid-to-solid ratio of 2L to 10L: 1kg, preferably 4L to 8L: 1kg. The use amount of the acid is controlled so that the soluble mono-calcium phosphate (Ca(H 2 PO 4 )2 ) is generated from the phosphorus and the calcium and enters the solution while reducing the use amount of the acid, the rare earth phosphate has a low solubility in a low-acidity condition, so that the rare earth in the apatite can be concentrated in the slag in the form of the rare earth phosphate, at the moment, the insoluble monazite will remain in the slag, thereby achieving the effective separation of the phosphorus from the rare earth and the monazite. Preferably, based on the mole number of the anions, the proportion of the hydrochloric acid or the nitric acid in the mixed acid solution used in the leaching step using the mixed acid is 1% to 30%, preferably 2% to 15%. The content of hydrochloric acid or nitric acid used in the present disclosure is not limited to the ranges above, the solubility of the rare earth phosphate in the system increases with high content of hydrochloric acid or nitric acid, so that the rare earth is leached out and enters into the solution, thus the rare earth cannot be concentrated in the slag. Preferably, the mass fraction of P 2 0 5 in the mixed acid used in the leaching step using the mixed acid is 15% to 50%, preferably 15% to 30%. The mass fraction of P 2 0 5 in the mixed acid used in the present disclosure is not limited to the ranges above, a high acidity facilitates decomposition of the phosphorite when the mixed acid containing P 20 5 within the ranges above is applied, thereby improving the yield of the phosphorus, however, an excessively high content of the phosphoric acid results in problems including low mass transfer efficiency due to high viscosity and so on. Preferably, in the leaching step using the mixed acid, the leaching temperature is 55C to 150 °C, and the leaching time is 0.5 to 8 hours. The leaching temperature and the leaching time in the leaching step using the mixed acid in the present disclosure are not limited to the ranges above, higher temperature facilitates the decomposition of the phosphorite, and the solubility product of the rare earth phosphate is smaller at the high temperature, so that the precipitate of the rare earth phosphate can be formed and enters the slag to be enriched therein. More preferably, the leaching temperature is 60°C to 90 °C, and the leaching time is 2 to 5 hours. A method specifically applicable to the phosphorus recovery may be selected as a solution for recovering the phosphorus in the mono-calcium phosphate solution. In a preferred embodiment of the present disclosure, the step of recovering the phosphorus of the mono-calcium phosphate solution includes: adding a sulfuric acid into the leaching solution to remove the calcium, with subsequent solid-liquid separation to obtain a phosphorus containing solution and a calcium sulfate gypsum, recovering the phosphorus of the phosphorus containing solution. In this method, the phosphorus in the apatite may be recovered by applying a mature wet-process sulfuric acid technique , the technique has simple steps and a relatively high recovery yield. Preferably, the step of recovering the phosphorus of the mono-calcium phosphate solution further includes: preparing a phosphorus product from the phosphorus containing solution after impurities removal, or recycling the phosphorus containing solution for leaching the phosphorite. In this method, the recycled phosphoric acid is used for decomposing and leaching the apatite, the whole process has reasonable links to effectively recover the rare earth and the phosphorus at the same time with low consumption of the sulfuric acid and low cost. The impurity removal step in the step above includes, but is not limited to removal of iron, silicon, aluminum, calcium, magnesium, thorium and uranium from the phosphorus containing solution. These impurity removal steps may apply conventional processes in the prior art as required. Similarly, the phosphorus has been separated from the rare earth before the step of recovering the rare earth in the rare earth phosphate containing slag in the present disclosure. The content of the rare earth in the rare earth phosphate containing slag, which is 3 to 10 times higher than that of the phosphorite, is still low, and the contents of the impurities including phosphorus, silicon, aluminum and so on are high, thus it is hard to recover the rare earth effectively by applying conventional sodium hydroxide decomposition, sulfuric acid decomposition. In a preferred embodiment of the present disclosure, the step of recovering the rare earth in the rare earth phosphate containing slag includes: adding an iron containing compound, a compound containing magnesium and/or calcium to the rare earth phosphate containing slag, then mixing with a concentrated sulfuric acid, with subsequent enhanced bake to obtain a calcination slag; leaching the calcination slag by water to obtain a rare earth containing water leach solution and a water leach slag; adjusting the pH value of the rare earth containing water leach solution to 3.8 to 5, filtering and obtaining a rare earth sulphate containing solution and a slag containing iron and thorium; adding a carbonate or an oxalate into the rare earth sulfate solution to precipitate the rare earth to obtain a rare earth carbonate or a rare earth oxalate, calcining the rare earth carbonate and the rare earth oxalate to obtain a rare earth oxide; or extracting the rare earth sulfate solution by using an acidic phosphorus extractant and obtaining a mixed rare earth chloride or single rare earth compounds. The present disclosure may keep the monazite and the rare earth phosphate in the slag so as to enrich the monazite and the rare earth phosphate, thus increasing the grade of the rare earth in the slag, and considerably reducing the amount of subsequent processing. Simple and unique processes including adding an iron to immobilize the phosphorus, adding a magnesium/calcium to immobilize fluorine and enhancing the calcination with the sulfuric acid so as to eliminate the interference of the phosphorus and the fluorine, thus effectively avoiding loss of rare earth precipitated in the form of a rare earth phosphate and a rare earth chloride during the leaching process, and avoiding environmental pollution caused by the fluorine escaping as a hydrogen fluoride gas during the calcination process. The method has low acid and alkaline consumption and the recovery rate of the rare earth may reach above 90%; in the meanwhile, the thorium is transformed into thorium pyrophosphate immobilized in the slag, thus preventing the radioactive thorium from being dispersed in the process to cause pollution. At the same time, the iron containing compound is added to immobilize the phosphorus in the slag, thus avoiding loss of the rare earth. Preferably, the added compound containing magnesium and/or calcium is at least one of an oxide of magnesium and/or calcium, a carbonate of magnesium and/or calcium, or a mineral containing magnesium and/or calcium, preferably, the mineral containing magnesium and/or calcium is at least one of dolomite and magnesite, and the iron containing compound is at least one of an iron containing tailing and an iron containing slag, preferably a tailing containing rare earth and iron. Preferably, in the step of adding the iron containing compound to the mixed slag, the mass ratio of the iron of the iron containing compound to the phosphorus of the rare earth phosphate containing slag is 2 to 4: 1, preferably 2.5 to 3.5: 1, an iron containing rare earth tailing is added in the ranges above to perform processing, which not only improves the yield of the rare earth, but also implements comprehensive utilization of an iron resource of the tailing, and implements recovery and utilization of rare earth in the tailing while largely reducing operation cost; besides, the mass ratio of Fe/P may be controlled in the subsequent impurity removal process with the pH value adjusted to 3.8 to 5, so as to form an iron phosphate precipitate and effectively remove the phosphorus, while excess iron may be hydrolyzed at the pH value to form a precipitate to avoid formation of a rare earth phosphate precipitate, thereby avoiding the rare earth loss. Preferably, in the step of adding the compound containing magnesium and/or calcium in the mixed slag, the molar ratio of magnesium and/or calcium in the compound containing magnesium and/or calcium to the fluorine in the rare earth phosphate containing slag is 1 to 2:2. The mixing ratio of the magnesium and/or calcium containing compound to the rare earth phosphate containing slag in the present disclosure is not limited to the range above, the two are mixed according to the molar ratio of 1 to 2:2, base on the premise the advantage of reducing the amount of the magnesium and/or calcium containing compound adding, the fluoride in the ore may be formed into a magnesium/calcium fluoride and magnesium/calcium fluorophosphate solid immobilized in the slag during the calcination process, thereby reducing environmental pollution caused by the escape of the fluoride as the hydrogen fluoride gas during the calcination process, while avoiding loss of the rare earth caused by a rare earth fluoride precipitate formed by the fluoride during the impurity removal process of the solution, so as to further improve the yield of rare earth. An available magnesium and/or calcium containing compound includes, but is not limited to a magnesium and/or calcium oxide , carbonate, or a magnesium and/or calcium containing mineral, such as dolomite, magnesite and so on. Preferably, during the enhanced bake, the concentrated sulfuric acid and the rare earth phosphate containing slag are mixed with a mass ratio of 1 to 2: 1, and the bake temperature is 200 to 500 °C, preferably 250 to 400°C. The calcination is performed within the temperature ranges so that the thorium, the iron and the phosphoric acid are formed into a phosphate and a pyrophosphate precipitates immobilized in the slag without being leached. Meanwhile, the radioactive element thorium is also immobilized in the slag, thus preventing the radioactive element thorium from being dispersed in the process to cause pollution. The concentration of the concentrated sulfuric acid used in the foregoing step is larger than or equal to 70%, preferably a concentrated sulfuric acid with the concentration of 98.3%. Preferably, in the step of adjusting the pH value of the rare earth containing water leach solution, the pH value of the rare earth containing water leach solution is adjusted by using a magnesium oxide and/or a caustic calcined dolomite, and the pH value of the rare earth containing water leach solution is adjusted to 4 to 4.5, preferably. The pH value of the rare earth containing water leach solution is adjusted by the magnesium oxide and/or the caustic calcined dolomite to ensure that the phosphorus may be transformed to an iron phosphate and a thorium phosphate as much as possible without the precipitation of rare earth. The beneficial effect of the present disclosure will be further described below in combination with Embodiment 1 to Embodiment 27. Embodiment 1 100 g of phosphorite containing 1.5% rare earth is used as a raw material, and leached with a mixed acid solution of phosphoric acid and hydrochloric acid, the mass fraction of the phosphoric acid in the mixed acid is 15% (based on P 2 0 5 ), and the proportion of the hydrochloric acid is 5% (based on the molar number of anions), the liquid-to-solid ratio of the system is controlled to : 1, 1000 mL of the mixed acid solution is added, a reaction is carried out for 6h at 55 °C , and filtering is performed to obtain a mono-calcium phosphate solution and 12.1 g rare earth phosphate containing slag. It is tested that the leaching rate of the rare earth in the phosphorite is 3.6% and the leaching rate of phosphorus is 95.1%. Sulfuric acid is added to the obtained mono-calcium phosphate solution to remove the calcium, and solid-liquid separation is performed to obtain a phosphorus containing solution and gypsum, phosphorus in the phosphorus containing solution is recovered. And a portion of the phosphorus containing solution is recycled and used for leaching phosphorite. Embodiment 2 100 g of phosphorite containing 3% rare earth is used as a raw material, and leached by using a mixed acid solution of phosphoric acid and hydrochloric acid, the mass fraction of the phosphoric acid in the mixed acid is % (based on P 205 ), and the proportion of the hydrochloric acid is 5% (based on the mole number of anions). The liquid-to-solid ratio of the system is controlled at 8: 1, 800 mL of the mixed acid solution is added, a reaction is carried out for 5h at 700C, and filtering is performed to obtain a mono-calcium phosphate solution and 11.1g rare earth phosphate containing slag. It is tested that the leaching rate of the rare earth in the phosphorite is 3.4% and the leaching rate of phosphorus is 98.1%. Sulfuric acid is added to the obtained mono-calcium phosphate solution to remove the calcium, and solid-liquid separation is performed to obtain a phosphorus containing solution and gypsum, phosphorus in the phosphorus containing solution is recovered. And a portion of the phosphorus containing solution is recycled and used for leaching phosphorite. Embodiment 3 100 g of phosphorite containing 3% rare earth is used as a raw material, and leached by using a mixed acid solution of phosphoric acid and hydrochloric acid, the mass fraction of the phosphoric acid in the mixed acid is % (based on P 205 ), and the proportion of the hydrochloric acid is 5% (based on the mole number of anions), the liquid-to-solid ratio of the system is controlled at 8: 1, 800 mL of the mixed acid solution is added, a reaction is carried out for 5h at 70C, and filtering is performed to obtain a mono-calcium phosphate solution and 10.6g rare earth phosphate containing slag. It is tested that the leaching rate of the rare earth in the phosphorite is 4.2% and the leaching rate of phosphorus is 98.1%. Sulfuric acid is added to the obtained mono-calcium phosphate solution to remove the calcium, and solid-liquid separation is performed to obtain a phosphorus containing solution and gypsum, phosphorus in the phosphorus containing solution is recovered. And a portion of the phosphorus containing solution is recycled and used for leaching phosphorite. Embodiment 4 100 g of phosphorite containing 3% rare earth is used as a raw material, and leached by using a mixed acid solution of phosphoric acid and hydrochloric acid, the mass fraction of the phosphoric acid in the mixed acid is % (based on P 205 ), and the proportion of the hydrochloric acid is 1% (based on the mole number of anions), the liquid-to-solid ratio of the system is controlled at 8: 1, 800 mL of the mixed acid solution is added, a reaction is carried out for 5h at 700C, and filtering is performed to obtain a mono-calcium phosphate solution and 11.8g rare earth phosphate containing slag. It is tested that the leaching rate of the rare earth in the phosphorite is 2.7% and the leaching rate of phosphorus is 95.5%. Sulfuric acid is added to the obtained mono-calcium phosphate solution to remove the calcium, and solid-liquid separation is performed to obtain a phosphorus containing solution and gypsum, phosphorus in the phosphorus containing solution is recovered. And a portion of the phosphorus containing solution is recycled and used for leaching phosphorite. Embodiment 5 100 g of phosphorite containing 3% rare earth is used as a raw material, and leached by using a mixed acid solution of phosphoric acid and hydrochloric acid, the mass fraction of the phosphoric acid in the mixed acid is % (based on P 2 05 ), and the proportion of the hydrochloric acid is 25% (based on the mole number of anions), the liquid-to-solid ratio of the system is controlled at 8: 1, 800 mL of the mixed acid solution is added, a reaction is carried out for 5h at 70C, and filtering is performed to obtain a mono-calcium phosphate solution and 11.0g rare earth phosphate containing slag. It is tested that the leaching rate of the rare earth in the phosphorite is 5% and the leaching rate of phosphorus is 98.5%. Sulfuric acid is added to the obtained mono-calcium phosphate solution to remove the calcium, and solid-liquid separation is performed to obtain a phosphoruscontaining solution and gypsum, phosphorus in the phosphorus containing solution is recovered. And a portion of the phosphorus containing solution is recycled and used for leaching phosphorite. Embodiment 6 100 g of phosphorite containing 2% rare earth is used as a raw material, and leached by using a mixed acid solution of phosphoric acid, hydrochloric acid and nitric acid, the mass fraction of the phosphoric acid in the mixed acid is 40% (based on P 2 05 ), and the proportion of the hydrochloric acid and the nitric acid is 8% (based on the mole number of anions, the mole ratio of the hydrochloric acid to the nitric acid is 1:1), the liquid-to-solid ratio of the system is controlled at 6: 1, 600 mL of the mixed acid solution is added, a reaction is carried out for 4h at 800C, and filtering is performed to obtain a mono-calcium phosphate solution and 9.7g rare earth phosphate containing slag. It is tested that the leaching rate of the rare earth in the phosphorite is 4.5% and the leaching rate of phosphorus is 97.8%. Sulfuric acid is added to the obtained mono-calcium phosphate solution to remove the calcium, and solid-liquid separation is performed to obtain a phosphorus containing solution and gypsum, phosphorus in the phosphorus containing solution is recovered. And a portion of the phosphorus containing solution is recycled and used for leaching phosphorite. Embodiment 7 100 g of phosphorite containing 14.4% rare earth and 20% of monazite is used as a raw material, and leached by using a mixed acid solution of phosphoric acid and hydrochloric acid, the mass fraction of the phosphoric acid in the mixed acid is 20% (based on P 2 05 ), and the proportion of the hydrochloric acid is 10% (based on the mole number of anions), the liquid-to-solid ratio of the system is controlled at 2: 1, 200 mL of the mixed acid solution is added, a reaction is carried out for 8h at 550C, and filtering is performed to obtain a mono-calcium phosphate solution and 33.4g rare earth phosphatecontaining slag. It is tested that the leaching rate of the rare earth in the phosphorite is 2.6% and the leaching rate of phosphorus is 95.0%. Sulfuric acid is added to the obtained mono-calcium phosphate solution to remove the calcium, and solid-liquid separation is performed to obtain a phosphorus containing solution and gypsum, phosphorus in the phosphorus containing solution is recovered. And a portion of the phosphorus containing solution is recycled and used for leaching phosphorite. Embodiment 8 100 g of phosphorite containing 14.4% rare earth and 20% of monazite is used as a raw material, and leached by using a mixed acid solution of phosphoric acid and hydrochloric acid, the mass fraction of the phosphoric acid in the mixed acid is 20% (based on P 2 05 ), and the proportion of the hydrochloric acid is 10% (based on the mole number of anions), the liquid-to-solid ratio of the system is controlled at 7: 1, 700 mL of the mixed acid solution is added, a reaction is carried out for 8h at 550C, and filtering is performed to obtain a mono-calcium phosphate solution and 31.1g rare earth phosphate containing slag. It is tested that the leaching rate of the rare earth in the phosphorite is 3.1% and the leaching rate of phosphorus is 97.5%. Sulfuric acid is added to the obtained mono-calcium phosphate solution to remove the calcium, and solid-liquid separation is performed to obtain a phosphorus containing solution and gypsum, phosphorus in the phosphorus containing solution is recovered. And a portion of the phosphorus containing solution is recycled and used for leaching phosphorite. Embodiment 9 100 g of phosphorite containing 14.4% rare earth and 20% of monazite is used as a raw material, and leached by using a mixed acid solution of phosphoric acid and hydrochloric acid, the mass fraction of the phosphoric acid in the mixed acid is 20% (based on P 2 05 ), and the proportion of the hydrochloric acid is 10% (based on the mole number of anions), the liquid-to-solid ratio of the system is controlled at 9: 1, 900 mL of the mixed acid solution is added, a reaction is carried out for 8h at 550C, and filtering is performed to obtain a mono-calcium phosphate solution and 31.0g rare earth phosphate containing slag. It is tested that the leaching rate of the rare earth in the phosphorite is 3.2% and the leaching rate of phosphorus is 98.2%. Sulfuric acid is added to the obtained mono-calcium phosphate solution to remove the calcium, and solid-liquid separation is performed to obtain a phosphorus containing solution and gypsum, phosphorus in the phosphorus containing solution is recovered. And a portion of the phosphorus containing solution is returned and used for leaching phosphorite. Embodiment 10 100 g of phosphorite containing 7.4% rare earth and 9.5% monazite is used as a raw material, and leached by using a mixed acid solution of phosphoric acid and hydrochloric acid, the mass fraction of the phosphoric acid in the mixed acid is 25% (based on P 2 05 ), and the proportion of the hydrochloric acid is 15% (based on the mole number of anions). The liquid-to-solid ratio of the system is controlled at 6: 1, 600 mL of the mixed acid solution is added, a reaction is carried out for 2h at 700C, and filtering is performed to obtain a mono-calcium phosphate solution and 17.8g rare earth phosphate containing slag. It is tested that the leaching rate of the rare earth in the phosphorite is 2.7% and the leaching rate of phosphorus is 98.2%. Sulfuric acid is added to the obtained mono-calcium phosphate solution to remove the calcium, and solid-liquid separation is performed to obtain a phosphorus containing solution and gypsum, phosphorus in the phosphorus containing solution is recovered. And a portion of the phosphorus containing solution is recycled and used for leaching phosphorite.
Embodiment 11 100 g of phosphorite containing 7.4% rare earth and 9.5% monazite is used as a raw material, and leached by using a mixed acid solution of phosphoric acid and nitric acid, the mass fraction of the phosphoric acid in the mixed acid is 25% (based on P 2 05 ), and the proportion of the nitric acid is 15% (based on the mole number of anions). the liquid-to-solid ratio of the system is controlled at 6: 1, 600 mL of the mixed acid solution is added, a reaction is carried out for 2h at 700C, and filtering is performed to obtain a mono-calcium phosphate solution and 18.9g rare earth phosphate containing slag. It is tested that the leaching rate of the rare earth in the phosphorite is 2.9% and the leaching rate of phosphorus is 97.6%. Sulfuric acid is added to the obtained mono-calcium phosphate solution to remove the calcium, and solid-liquid separation is performed to obtain a phosphorus containing solution and gypsum, phosphorus in the phosphorus containing solution is recovered. And a portion of the phosphorus containing solution is recycled and used for leaching phosphorite. Embodiment 12 100 g of phosphorite containing 9% rare earth and 11.9% monazite is used as a raw material, and leached by using a mixed acid solution of phosphoric acid and hydrochloric acid, the mass fraction of the phosphoric acid in the mixed acid is 25% (based on P 2 05 ), and the proportion of the hydrochloric acid is 20% (based on the mole number of anions), the liquid-to-solid ratio of the system is controlled at 6: 1, 600 mL of the mixed acid solution is added, a reaction is carried out for 4h at 57C, and filtering is performed to obtain a mono-calcium phosphate solution and 20.7g rare earth phosphate containing slag. It is tested that the leaching rate of the rare earth in the phosphorite is 3.5% and the leaching rate of phosphorus is 96.6%. Sulfuric acid is added to the obtained mono-calcium phosphate solution to remove the calcium, and solid-liquid separation is performed to obtain a phosphorus containing solution and gypsum, phosphorus in the phosphorus containing solution is recovered. And a portion of the phosphorus containing solution is recycled and used for leaching phosphorite. Embodiment 13 100 g of phosphorite containing 9.0% rare earth and 11.9% monazite is used as a raw material, and leached by using a mixed acid solution of phosphoric acid and hydrochloric acid, the mass fraction of the phosphoric acid in the mixed acid is 25% (based on P 2 05 ), and the proportion of the hydrochloric acid is 20% (based on the mole number of anions), the liquid-to-solid ratio of the system is controlled at 6: 1, 600 mL of the mixed acid solution is added, a reaction is carried out for 4h at 900C, and filtering is performed to obtain a mono-calcium phosphate solution and 20.1g rare earth phosphate containing slag. It is tested that the leaching rate of the rare earth in the phosphorite is 3.2% and the leaching rate of phosphorus is 98.3%. Sulfuric acid is added to the obtained mono-calcium phosphate solution to remove the calcium, and solid-liquid separation is performed to obtain a phosphorus containing solution and gypsum, phosphorus in the phosphorus containing solution is recovered. And a portion of the phosphorus containing solution is recycled and used for leaching phosphorite. Embodiment 14 100 g of phosphorite containing 9.0% rare earth and 11.9% monazite is used as a raw material, and leached by using a mixed acid solution of phosphoric acid and hydrochloric acid, the mass fraction of the phosphoric acid in the mixed acid is 25% (based on P 2 05 ), and the proportion of the hydrochloric acid is 20% (based on the mole number of anions), the liquid-to-solid ratio of the system is controlled at 6: 1, 600 mL of the mixed acid solution is added, a reaction is carried out for 4h at 1200C, and filtering is performed to obtain a mono-calcium phosphate solution and 19.9g rare earth phosphate containing slag.
It is tested that the leaching rate of the rare earth in the phosphorite is 3.2% and the leaching rate of phosphorus is 98.2%. Sulfuric acid is added to the obtained mono-calcium phosphate solution to remove the calcium, and solid-liquid separation is performed to obtain a phosphorus containing solution and gypsum, phosphorus in the phosphorus containing solution is recovered. And a portion of the phosphorus containing solution is recycled and used for leaching phosphorite. Embodiment 15 1000 g of phosphorite containing 8.1% rare earth and 10.6% monazite is used as a raw material, and leached by using a mixed acid solution of phosphoric acid and hydrochloric acid, the mass fraction of the phosphoric acid in the mixed acid is 20% (based on P 2 05 ), and the proportion of the hydrochloric acid is 15% (based on the mole number of anions), the liquid-to-solid ratio of the system is controlled at 6: 1, 6000 mL of the mixed acid solution is added, a reaction is carried out for 5h at 800C, and filtering is performed to obtain a mono-calcium phosphate solution and 168.4g rare earth phosphate containing slag. It is tested that the leaching rate of the rare earth in the phosphorite is 3.0% and the leaching rate of phosphorus is 98.5%. Sulfuric acid is added to the obtained mono-calcium phosphate solution to remove the calcium, and solid-liquid separation is performed to obtain a phosphorus containing solution and gypsum, phosphorus in the phosphorus containing solution is recovered. And a portion of the phosphorus containing solution is recycled and used for leaching phosphorite. Embodiment 16 100 g of phosphorite containing 11.4% rare earth and 15.5% monazite is used as a raw material, and leached by using a mixed acid solution of phosphoric acid and hydrochloric acid, the mass fraction of the phosphoric acid in the mixed acid is 30% (based on P 2 05 ), and the proportion of the hydrochloric acid is 30% (based on the mole number of anions), the liquid-to-solid ratio of the system is controlled at 3: 1, 300 mL of the mixed acid solution is added, a reaction is carried out for 1h at 1100C, and filtering is performed to obtain a mono-calcium phosphate solution and 24.7g rare earth phosphate containing slag. It is tested that the leaching rate of the rare earth in the phosphorite is 3.3% and the leaching rate of phosphorus is 95.7%. Sulfuric acid is added to the obtained mono-calcium phosphate solution to remove the calcium, and solid-liquid separation is performed to obtain a phosphorus containing solution and gypsum, phosphorus in the phosphorus containing solution is recovered. And a portion of the phosphorus containing solution is recycled and used for leaching phosphorite. Embodiment 17 100 g of phosphorite containing 6.5% rare earth and 8.2% monazite is used as a raw material, and leached by using a mixed acid solution of phosphoric acid and nitric acid, the mass fraction of the phosphoric acid in the mixed acid is 50% (based on P 2 05 ), and the proportion of the nitric acid is 2% (based on the mole number of anions), the liquid-to-solid ratio of the system is controlled at 4: 1, 400 mL of the mixed acid solution is added, a reaction is carried out for 0.5h at 1500C, and filtering is performed to obtain a mono-calcium phosphate solution and 19.5g rare earth phosphate containing slag. It is tested that the leaching rate of the rare earth in the phosphorite is 3.5% and the leaching rate of phosphorus is 95.0%. Sulfuric acid is added to the obtained mono-calcium phosphate solution to remove the calcium, and solid-liquid separation is performed to obtain a phosphorus containing solution and gypsum, phosphorus in the phosphorus containing solution is recovered. And a portion of the phosphorus containing solution is recycled and used for leaching phosphorite. Comparison example 1 100 g of phosphorite containing 9.0% rare earth and 11.9% monazite is used as a raw material, and leached by using a hydrochloric acid solution, the fraction of the hydrochloric acid is 20%, the liquid-to-solid ratio of the system is controlled at 6: 1, 600 mL of the hydrochloric acid is added, a reaction is carried out for 4h at 900C, and filtering is performed to obtain a CaCl 2 containing solution and 14.2g of a rare earth phosphate containing slag. It is tested that the leaching rate of the rare earth in the phosphorite is 78.2% and the leaching rate of phosphorus is 99.4%. Comparison example 2 100 g of phosphorite containing 9% rare earth and 11.9% monazite is used as a raw material, and leached by using a phosphoric acid solution, the mass fraction of the phosphoric acid is 25%, the liquid-to-solid ratio of the system is controlled at 6: 1, 600 mL of the hydrochloric acid is added, a reaction is carried out for 4h at 900C, and filtering is performed to obtain a mono-calcium phosphate solution and 43.1g of a rare earth phosphate containing slag. It is tested that the leaching rate of the rare earth in the phosphorite is 2.5% and the leaching rate of phosphorus is 85.0%. Sulfuric acid is added to the obtained mono-calcium phosphate solution to remove the calcium, and solid-liquid separation is performed to obtain a phosphorus containing solution and gypsum, phosphorus in the phosphorus containing solution is recovered. Embodiment 18 15 g of the rare earth phosphate containing slag obtained in Embodiment is used as a raw material, an iron containing slag is added according to the phosphorus content in the slag, the mass ratio of iron in the iron containing slag to phosphorus in the rare earth phosphate containing slag is controlled to be 2.5, and magnesium oxide is added according to the fluorine content in the slag, the mole ratio of Mg/F is controlled to be 1: 2, and then concentrated sulfuric acid is added and mixing is performed, the mass ratio of the concentrated sulfuric acid to the rare earth phosphate containing slag is 1: 1, enhanced bake is performed at 200 °C to obtain a calcination slag.
The calcination slag is leached with 200mL of water, and filtered to obtain a rare earth containing water leach solution and an water leach slag. Magnesium oxide is added to adjust the pH value of the rare earth containing water leach solution to 4.0, and filtering is performed to obtain an iron and thorium containing precipitate, and a rare earth sulfate solution (Fe 0.03g/L, P 0.005g/L, Th<0.06 mg/L); a carbonate is added into the rare earth sulfate solution to precipitate rare earth to obtain a rare earth carbonate, calcination is performed to obtain an rare earth oxide, the recovery rate of the rare earth is 91.5%. Embodiment 19 15 g of the rare earth phosphate containing slag obtained in Embodiment is used as a raw material, an iron containing slag is added according to the phosphorus content in the slag, the mass ratio of iron in the iron containing slag to phosphorus in the rare earth phosphate containing slag is controlled to be 2.5, and magnesium oxide is added according to the fluorine content in the slag, the mole ratio of Mg/F is controlled to be 1: 2, and then concentrated sulfuric acid is added and mixing is performed, the mass ratio of the concentrated sulfuric acid to the rare earth phosphate containing slag is 1: 1, enhanced bake is performed at 2500C to obtain a calcination slag. The calcination slag is leached with 200mL of water, and filtered to obtain a rare earth containing water leach solution and a water leach slag. Magnesium oxide is added to adjust the pH value of the rare earth containing water leach solution to 4.0, and filtering is performed to obtain an iron and thorium containing precipitate, and a rare earth sulfate solution (Fe 0.04g/L, P 0.005g/L, Th<0.05mg/L); a carbonate is added into the rare earth sulfate solution to precipitate rare earth to obtain a rare earth carbonate, calcination is performed to obtain an rare earth oxide, the recovery rate of the rare earth is 93.5%. Embodiment 20 15 g of the rare earth phosphate containing slag obtained in Embodiment is used as a raw material, an iron containing slag is added according to the phosphorus content in the slag, the mass ratio of iron in the iron containing slag to phosphorus in the rare earth phosphate containing slag is controlled to be 2.5, and magnesium oxide is added according to the fluorine content in the slag, the mole ratio of Mg/F is controlled to be 1: 2, and then concentrated sulfuric acid is added and mixing is performed, the mass ratio of the concentrated sulfuric acid to the rare earth phosphate containing slag is 1: 1, enhanced bake is performed at 5000C to obtain a calcination slag. The calcination slag is leached with 200mL of water, and filtered to obtain a rare earth containing water leach solution and a water leach slag. Magnesium oxide is added to adjust the pH value of the rare earth containing water leach solution to be 4.0, and filtering is performed to obtain an iron and thorium containing precipitate, and a rare earth sulfate solution (Fe 0.06g/L, P 0.005g/L, Th<0.05mg/L); a carbonate is added into the rare earth sulfate solution to precipitate rare earth to obtain a rare earth carbonate, calcination is performed to obtain an rare earth oxide, the recovery rate of the rare earth is 95.1%. Embodiment 21 15 g of the rare earth phosphate containing slag obtained in Embodiment is used as a raw material, an iron containing rare earth tailing is added according to the phosphorus content in the slag, the mass ratio of iron in the iron containing rare earth tailing to phosphorus in the rare earth phosphate containing slag is controlled to be 2, and dolomite is added according to the fluorine content in the slag, the mole ratio of (Ca+Mg)/F is controlled to be 1.5: 2, and then concentrated sulfuric acid is added and mixing is performed, the mass ratio of the concentrated sulfuric acid to the rare earth phosphate containing slag is 1.5: 1, enhanced bake is performed at 3500C to obtain a calcination slag. The calcination slag is leached with 200mL of water, and filtered to obtain a rare earth containing water leach solution and a water leach slag.
Caustic calcined dolomite is added to adjust the pH value of the rare earth containing water leach solution to 4.5, and filtering is performed to obtain an iron and thorium containing precipitate, and a rare earth sulfate solution (Fe 0.009g/L, P 0.005g/L, Th<0.05mg/L), a carbonate is added into the rare earth sulfate solution to precipitate rare earth to obtain a rare earth carbonate, calcination is performed to obtain an rare earth oxide, the recovery rate of the rare earth is 93.1%. Embodiment 22 15 g of the rare earth phosphate containing slag obtained in Embodiment is used as a raw material, an iron containing rare earth tailing is added according to the phosphorus content in the slag, the mass ratio of iron in the iron containing rare earth tailing to phosphorus in the rare earth phosphate containing slag is controlled to be 3, and dolomite is added according to the fluorine content in the slag, the mole ratio of (Ca+Mg)/F is controlled to be 1.5: 2, and then concentrated sulfuric acid is added and mixing is performed, the mass ratio of the concentrated sulfuric acid to the rare earth phosphate containing slag is 1.5: 1, enhanced bake is performed at 3500C to obtain a calcination slag. The calcination slag is leached with 200mL of water, and filtered to obtain a rare earth containing water leach solution and a water leach slag. Caustic calcined dolomite is added to adjust the pH value of the rare earth containing water leach solution to 4.5, and filtering is performed to obtain an iron and thorium containing precipitate, and a rare earth sulfate solution (Fe 0.02g/L, P 0.0009g/L, Th<0.03mg/L), a carbonate is added into the rare earth sulfate solution to precipitate rare earth, to obtain a rare earth carbonate, calcination is performed to obtain an rare earth oxide, the recovery rate of the rare earth is 95.4%. Embodiment 23 15 g of the rare earth phosphate containing slag obtained in Embodiment is used as a raw material, an iron containing rare earth tailing is added according to the phosphorus content in the slag, the mass ratio of iron in the iron containing rare earth tailing to phosphorus in the rare earth phosphate containing slag is controlled to be 4, and dolomite is added according to the fluorine content in the slag, the mole ratio of (Ca+Mg)/F is controlled to be 1.5: 2, and then concentrated sulfuric acid is added and mixing is performed, the mass ratio of the concentrated sulfuric acid to the rare earth phosphate containing slag is 1.5: 1, enhanced bake is performed at 3500C to obtain a calcination slag. The calcination slag is leached with 200mL of water, and filtered to obtain a rare earth containing water leach solution and a water leach slag. Caustic calcined dolomite is added to adjust the pH value of the rare earth containing water leach solution to 4.5, and filtering is performed to obtain an iron and thorium containing precipitate, and a rare earth sulfate solution (Fe 0.02g/L, P 0.0008g/L, Th<0.04mg/L); a carbonate is added into the rare earth sulfate solution to precipitate rare earth to obtain a rare earth carbonate, calcination is performed to obtain an rare earth oxide, the recovery rate of the rare earth is 96.2%. Embodiment 24 15 g of the rare earth phosphate containing slag obtained in Embodiment is used as a raw material, an iron containing tailing is added according to the phosphorus content in the slag, the mass ratio of iron in the iron containing tailing to phosphorus in the rare earth phosphate containing slag is controlled to be 3.5, and magnesite is added according to the fluorine content in the slag, the mole ratio of Mg/F is controlled to be 1, and then concentrated sulfuric acid is added and mixing is performed, the mass ratio of the concentrated sulfuric acid to the rare earth phosphate containing slag is 2: 1, enhanced bake is performed at 4000C to obtain a calcination slag. The calcination slag is leached with 200mL of water, and filtered to obtain a rare earth containing water leach solution and a water leach slag. Caustic calcined dolomite is added to adjust the pH value of the rare earth containing water leach solution to 3.8, and filtering is performed to obtain an iron and thorium containing precipitate, and a rare earth sulfate solution (Fe 0.05g/L, P 0.007g/L, Th<0.05mg/L), a carbonate is added into the rare earth sulfate solution to precipitate rare earth to obtain a rare earth carbonate, calcination is performed to obtain an rare earth oxide, the recovery rate of the rare earth is 96.1%. Embodiment 25 15 g of the rare earth phosphate containing slag obtained in Embodiment is used as a raw material, an iron containing tailing is added according to the phosphorus content in the slag, the mass ratio of iron in the iron containing tailing to phosphorus in the rare earth phosphate containing slag is controlled to be 3.5, and magnesite is added according to the fluorine content in the slag, the mole ratio of Mg/F is controlled to be 1, and then concentrated sulfuric acid is added and mixing is performed, the mass ratio of the concentrated sulfuric acid to the rare earth phosphate containing slag is 2: 1, enhanced bake is performed at 4000C to obtain a calcination slag. The calcination slag is leached with 200mL of water, and filtered to obtain a rare earth containing water leach solution and a water leach slag. Caustic calcined dolomite is added to adjust the pH value of the rare earth containing water leach solution to 4.3, and filtering is performed to obtain an iron and thorium containing precipitate, and a rare earth sulfate solution (Fe 0.04g/L, P 0.001g/L, Th<0.04mg/L), a carbonate is added into the rare earth sulfate solution to precipitate rare earth to obtain a rare earth carbonate, calcination is performed to obtain an rare earth oxide, the recovery rate of the rare earth is 95.8%. Embodiment 26 15 g of the rare earth phosphate containing slag obtained in Embodiment is used as a raw material, an iron containing tailing is added according to the phosphorus content in the slag, the mass ratio of iron in the iron containing tailing to phosphorus in the rare earth phosphate containing slag is controlled to be 3.5, and magnesite is added according to the fluorine content in the slag, the mole ratio of Mg/F is controlled to be 1, and then concentrated sulfuric acid is added and mixing is performed, the mass ratio of the concentrated sulfuric acid to the rare earth phosphate containing slag is 2: 1, enhanced bake is performed at 4000C to obtain a calcination slag. The calcination slag is leached with 200mL of water, and filtered to obtain a rare earth containing water leach solution and a water leach slag. Caustic calcined dolomite is added to adjust the pH value of the rare earth containing water leach solution to 5, and filtering is performed to obtain an iron and thorium containing precipitate, and a rare earth sulfate solution (Fe 0.01g/L, P 0.0008g/L, Th<0.04mg/L), a carbonate is added into the rare earth sulfate solution to precipitate rare earth to obtain a rare earth carbonate
, calcination is performed to obtain an rare earth oxide, the recovery rate of the rare earth is 95.0%. Embodiment 27 15 g of the rare earth phosphate containing slag obtained in Embodiment is used as a raw material, an iron containing slag is added according to the phosphorus content in the slag, the mass ratio of iron in the iron containing slag to phosphorus in the rare earth phosphate containing slag is controlled to be 3, and calcium oxide is added according to the fluorine content in the slag, the mole ratio of Ca/F is controlled to be 1.5: 2, and then concentrated sulfuric acid is added and mixing is performed, the mass ratio of the concentrated sulfuric acid to the rare earth phosphate containing slag is 1.5: 1, enhanced bake is performed at 4500 C to obtain a calcination slag. The calcination slag is leached with 200mL of water, and filtered to obtain a rare earth containing water leach solution and a water leach slag. Magnesium oxide is added to adjust the pH value of the rare earth containing water leach solution to 4, and filtering is performed to obtain an iron and thorium containing precipitate, and a rare earth sulfate solution (Fe 0.05g/L, P 0.002g/L, Th<0.05mg/L); a carbonate is added into the rare earth sulfate solution to precipitate rare earth to obtain a rare earth carbonate
, calcination is performed to obtain an rare earth oxide, the recovery rate of the rare earth is 95.8%. It may be seen from the foregoing description that the embodiments of the present application have implemented the following technical effect: the present disclosure leaches a rare earth containing phosphorite by using a mixed acid solution so that the phosphorus in the phosphorite forms highly-soluble mono-calcium phosphate, at the same time by performing regulation and control in the leaching process to precipitate and enrich the rare earth in the form of a rare earth phosphate in a slag, if the rare earth containing phosphorite further contains a monazite, the monazite and the rare earth phosphate are enriched in the slag, thereby separating the phosphorus and the rare earth. A hydrochloric acid or a nitric acid in the mixed acid solution is propitious to decompose apatite while ensuring that the rare earth is enriched in the slag in the form of a rare earth phosphate precipitate, thereby improving the leaching rate of the phosphorus in the apatite. Besides, the hydrochloric acid or the nitric acid can provide hydrogen ions H+, and can reduce the content of phosphate radicals and the viscosity of the system with the same acid content, thus facilitating leaching of the phosphorus; in the meanwhile, the existence of the chloride ions or the nitrate ions is propitious to increase the solubility of calcium ions in a solution and decomposition of the apatite. The rare earth and the phosphorus element in the rare earth containing phosphorite can be separated effectively by a filtering process, thus improving the respective recovery rate of the rare earth and the phosphorus. At the same time, the rare earth enters the slag in the form of the rare earth phosphate, and is enriched with the insoluble monazite during the acid leaching process so as to recover the rare earth collectively, thereby simplifying recovery steps, improving the recovery rate of the rare earth, and achieving the purpose of comprehensive recovery of the rare earth with low cost. The above are only preferred embodiments of the present disclosure, but are not used for limiting the present disclosure. For those skilled in the art, the present disclosure may have various modifications and changes. Any modifications, equivalent replacements, improvements and the like made within the spirit and principles of the present disclosure shall be included in the scope of protection of the present disclosure.
Throughout this specification and the claims which follow, unless the context requires otherwise, the word "comprise", and variations such as "comprises" and "comprising", will be understood to imply the inclusion of a stated integer or step or group of integers or steps but not the exclusion of any other integer or step or group of integers or steps.
The reference in this specification to any prior publication (or information derived from it), or to any matter which is known, is not, and should not be taken as an acknowledgment or admission or any form of suggestion that that prior publication (or information derived from it) or known matter forms part of the common general knowledge in the field of endeavor to which this specification relates.

Claims (20)

  1. THE CLAIMS DEFINING THE INVENTION ARE AS FOLLOWS: 1. A method for recovering phosphorus and rare earth from a rare earth containing phosphorite comprising the following steps: leaching the rare earth containing phosphorite at a leaching temperature of 70 °C to 150 °C and for a leaching time is 0.5 to 8 hours using a mixed acid solution, filtering and obtaining a mono-calcium phosphate solution and a rare earth phosphate containing slag, wherein the main component of the mixed acid solution is a phosphoric acid and the mixed acid solution further comprises a hydrochloric acid and/or a nitric acid; recovering (i) the phosphorus of the mono-calcium phosphate solution, and (ii) the rare earth of the rare earth phosphate containing slag.
  2. 2. The method according to claim 1, wherein the rare earth containing phosphorite contains a monazite.
  3. 3. The method according to claim 1 or 2, wherein based on a molar number of anions, a proportion of the hydrochloric acid and/or the nitric acid in the mixed acid solution is 1% to 30%.
  4. 4. The method according to claim 1 or 2, wherein a mass fraction of P205 in the mixed acid solution is 15% to 50%.
  5. 5. The method according to claim 4, wherein in the step of leaching the rare earth containing phosphorite by using the mixed acid solution, the mixed acid solution and the rare earth containing phosphorite are mixed at a liquid-to-solid ratio of 2L to 10L: 1kg.
  6. 6. The method according to claim 1 or 2, wherein the leaching temperature is 60°C to 90 °C and the leaching time is 2 to 5 hours.
  7. 7. The method according to claim 1 or 2, wherein the step of recovering the phosphorus of the mono-calcium phosphate solution includes: adding a sulfuric acid into the mono-calcium phosphate solution, performing solid-liquid separation and obtaining a phosphorus containing solution and a calcium sulfate gypsum, and then recovering the phosphorus of the phosphorus containing solution.
  8. 8. The method according to claim 7, wherein the step of recovering the phosphorus of the mono-calcium phosphate solution further includes: preparing a phosphoric acid from a portion of the phosphorus containing solution after impurities removal, then recycling the prepared phosphoric acid to the leaching step.
  9. 9. The method according to claim 1 or 2, wherein the step of recovering the rare earth of the rare earth phosphate containing slag includes: adding an iron containing compound, a compound containing magnesium and/or a calcium into the rare earth phosphate containing slag, then mixing with a concentrated sulfuric acid, and performing an enhanced bake to obtain a calcination slag; leaching the calcination slag by water to obtain a rare earth containing water leach solution and a water leach slag; adjusting the pH value of the rare earth containing water leach solution to 3.8 to 5, filtering and obtaining a rare earth sulfate solution and a slag containing iron and thorium; adding a carbonate or an oxalate into the rare earth sulfate solution to precipitate the rare earth, and obtaining a rare earth carbonate or a rare earth oxalate, calcining the rare earth carbonate and the rare earth oxalate to obtain a rare earth oxide; or extracting the rare earth sulfate solution by using an acidic phosphorus extractant to obtain a mixed rare earth chloride or single rare earth compounds.
  10. 10. The method according to claim 9, wherein the compound containing magnesium and/or calcium is at least one of an oxide, a carbonate or a mineral, and the iron containing compound is at least one of an iron containing tailing and an iron containing slag.
  11. 11. The method according to claim 9, wherein the molar ratio of the magnesium and/or calcium of the compound containing magnesium and/or calcium to the fluorine of the rare earth phosphate containing slag is 1 to 2: 2.
  12. 12. The method according to claim 9, wherein a mass ratio of the iron of the iron containing compound to the phosphorus of the rare earth phosphate containing slag is 2 to 4: 1.
  13. 13. The method according to claim 9, wherein during the enhanced bake, the concentrated sulfuric acid and the rare earth phosphate containing slag are mixed with a mass ratio of 1 to 2: 1; and the bake temperature during the enhanced bake step is 200°C to 500 °C.
  14. 14. The method according to claim 9, wherein in the step of adjusting the pH value of the rare earth containing water leach solution, the pH value of the rare earth containing water leach solution is adjusted by using a magnesium oxide and/or a caustic calcined dolomite, and the pH value of the rare earth containing water leach solution is adjusted to 4 to 4.5.
  15. 15. The method according to claim 1 or 2, wherein based on a molar number of anions, a proportion of the hydrochloric acid and/or the nitric acid in the mixed acid solution is 2% to 15%.
  16. 16.The method according to claim 1 or 2, wherein a mass fraction of P205 in the mixed acid solution is 15% to 30%.
  17. 17.The method according to claim 4, wherein in the step of leaching the rare earth containing phosphorite by using the mixed acid solution, the mixed acid solution and the rare earth containing phosphorite are mixed at a liquid-to-solid ratio of 4L to 8L: 1kg.
  18. 18.The method according to claim 10, wherein the iron containing compound is a tailing containing rare earth and iron.
  19. 19.The method according to claim 9, wherein a mass ratio of the iron of the iron containing compound to the phosphorus of the rare earth phosphate containing slag is 2.5 to 3.5: 1.
  20. 20.The method according to claim 13, wherein the bake temperature during the enhanced bake step is 250 °C to 400 °C.
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CN112074619A (en) 2018-05-03 2020-12-11 阿拉弗拉资源有限公司 Treatment of rare earth sulphate solutions
AU2019262097B2 (en) 2018-05-03 2023-12-14 Arafura Resources Limited Process for the recovery of rare earths
CN108467099A (en) * 2018-05-09 2018-08-31 内蒙古包钢和发稀土有限公司 Rare earth sulfuric acid ammonium waste water treatment oxalic acid circulation utilization method
CN108950188B (en) * 2018-05-25 2020-06-30 包头稀土研究院 Method for extracting phosphorus and rare earth step by roasting phosphorus-containing rare earth concentrate with concentrated sulfuric acid at low temperature
CN110872128A (en) * 2018-08-31 2020-03-10 贵州芭田生态工程有限公司 Control phosphorite preparation system of component balance among phosphorite
CN110196289B (en) * 2019-02-12 2021-08-24 紫金矿业集团股份有限公司 Method for diagnosing rare earth elements in phosphate ore
CN110004292B (en) * 2019-04-19 2020-12-29 湖南雅城新材料有限公司 Process for purifying waste manganese sulfate solution to reduce content of calcium and magnesium
CN110467168A (en) * 2019-09-19 2019-11-19 中南大学 The recovery method of titanium pigment in a kind of ardealite
CN113046578B (en) * 2021-02-08 2022-09-16 五矿(北京)稀土研究院有限公司 Preparation method of low-impurity rare earth feed liquid
CN114249308B (en) * 2021-11-19 2023-09-08 四川大学 Method for extracting phosphorus resources and rare earth resources in phosphorus-containing mixed rare earth concentrate
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