Method of processing phosphogypsum. RU patent 2504593.

FIELD: chemistry.

SUBSTANCE: method of processing phosphogypsum involves step-by-step agitation sulphuric-acid leaching of rare-earth metals and phosphorus while feeding sulphuric acid to the head step, using the obtained leaching solution of the head step at subsequent leaching steps, separating the undissolved residue from pulp of a tail step and washing with water, treating the leaching solution of the tail step to obtain a mother solution, using the mother solution and the washing solution for leaching. Leaching of the rare-earth metals and phosphorus at the second and subsequent steps is carried out from a mixture of phosphogypsum and the leached pulp from the previous step. Sulphuric acid is fed to the head leaching step in an amount which enables to extract rare-earth metals and phosphorus into the solution at the head step and subsequent steps at pH values at the tail leaching step not higher than pH at the onset of precipitation of rare-earth metal phosphates. The tail step for leaching rare-earth metals and phosphorus is carried out while simultaneously treating the leaching solution by extracting rare-earth metals by sorption with a cationite. The rare-earth metal-saturated cationite is separated from the mother pulp and taken for producing a rare-earth metal concentrate. A portion of the mother solution is pre-purified from phosphorus by precipitation thereof with a basic calcium compound. The obtained phosphorus-containing precipitate is fed for recycling.

EFFECT: invention increases extraction of rare-earth metals from phosphogypsum, reduces loss of rare-earth metals with a wet insoluble precipitate, reduces consumption of washing water and ensures full water recycling.

12 cl, 1 dwg, 3 ex

The invention relates to the chemical industry, in particular to the processing of phosphogypsum.

Phosphogypsum (PG) is a waste sulfuric acid processing of Apatite concentrate in the production of phosphate fertilizers, processing which allows to extract by leaching of rare earth metals (REM), which are defined as the lanthanides and yttrium, and to receive from the insoluble residue, construction and other products. Practical implementation requires optimization and intensification of the process, prevent contamination of the natural environment, the introduction of the turnover of consumable reagents, materials and water. For these purposes described various technical solutions. Thus, patent RU 2457267C2, Bashlykova and others, 27.07.2012, a method of refining FG extraction of rare-earth metals and phosphorus, in which the leaching of lead into Canova mode using a bacterial system based on acidophilus Tihonovich bacteria within 3 to 30 days. In the patent RU 2412265 C1, Abramov and others, 20.02.2011, it is recommended to activate the hydroacoustic effects of leaching of REE by a mixture of nitric and sulfuric acids in the subsequent sorption of REE on the cation exchanger. In the patent EA 014877 B1, Couderc and others, 28.02.2011, described is a method of obtaining from FY evenly-grained gypsum and concentrate REE by water and gravity separation associated with the separation of the receiving tetrafluoride silicon, and when cleaning the circulating water, a mixture of gypsum and superphosphate. There are other solutions for leaching of REE from FG (for example, CN 101440430 And from 27.05.2009 and CN 101597688 A dated 09.12.2009 (Guizhou Guanga Energy)). In the application PL 393552 A1, Palka, S., J. Szydlowski, offered the process of extracting rare-earth metals by leaching FG nanobody (nanowoda) without the use of any acids. However, in the presence of novelty feasibility of the above-mentioned method is not justified in part for optimal recovery of REE and technical-economic efficiency. Preference is given to traditional sulfuric acid to the processing methods consistent with the prior art are discussed below.

The method for extracting rare-earth metals from FG (EN 2225892 C1, Lokshin AL. and others, 20.03.2004), including sequential leaching of REE from some portions FY circulating solution 20-25%sulfuric acid at W:T=2-3 for 60 min, separating the insoluble residue from productive solution, crystallization of REE concentrate in the form of sulphates by bringing productive solution to the state supersaturated for rare earth metals, increasing the concentration of sulfuric acid to >30% at a temperature of 20-80°C. the Crystallization of sulfates REM carried out preferably in the presence of the seed of them at W:T not more than 100 within of 0.4-3 hours removing the REM in the concentrate is in the range of 50-60%. Concentrate REE separate filter is receiving from the fallopian ~30%-aqueous solution of H ₂SO₄one part is used for decomposition of Apatite concentrate, and the other after water dilution to 20-25% H₂SO₄- turnover for the leaching of REE from FG.

The disadvantages of the method are a significant number of technological operations at high pH and duration, as well as in the necessity of withdrawing from the process part of ~30% solution of H₂SO₄in the production of fertilizers, i.e. the decomposition of Apatite. It's not always possible, and in addition, is associated with a considerable turnover of REM, which inevitably reduces the extraction of REE from FG.

The method for extracting rare earth elements from FG (EN 2293781 C1, Lokshin AP and others, 20.02.2007), according to which FG is treated with a solution of sulfuric acid with a concentration of 22-30 wt.% if F:T=1.8 to 2.2 V for 20-30 min with the extraction of rare earth elements and sodium in solution, preventing with such duration of the process of spontaneous crystallization of rare earth elements from leaching solution prior to separation from the insoluble residue. After separation of the insoluble residue in the solution increases the degree of supersaturation of its rare earths by ensuring that the concentration of sodium in the range of 0.4-1.2 g/l using mainly sulfate or sodium carbonate.

The disadvantages of this method are the absence of the national technical decisions on the exclusion of a significant loss of rare earth elements, contained in the wet insoluble residue, and preparation for disposal and accumulation of impurities in the products of the process.

A method of refining FG - partially washed postopera, consisting mainly of bassanite 2CaSO₄·H₂O (see Lokshin AL, Kalinnikov V.T. Physico-chemical assessment and development of environmentally appropriate technologies for extraction of lanthanides from postopera // build the foundations of the modern strategies of natural resource management in the Euro-Asian region. Apatity: KSC RAS, 2005, s-269). Leaching of REE spend 26%solution of sulfuric acid at W:T=1.8 to 2.2 V for 20-25 minutes the resulting slurry for a period of not more than 5 min share (filtered) on the productive solution containing sulfates of rare-earth metals and insoluble residue.

From the pregnant solution crystallized double sulfates of rare-earth metals and sodium for 2 h at ensuring the concentration of sodium in the range of 0.4-1.2 g/l with the help of Na₂SO₄(or Na₂CO₃or lanthanides such as cerium sulfate. The resulting crystals of the double sulphates NaLn(SO₄)₂·H₂O, how concentrate Σ REM, separated by filtration from the sulfuric acid mother liquor, ≥98.3% of the volume of which is sent to the turnover on stage sulfuric acid leaching of REE, and 1.7% of the volume in the production of extraction the th phosphoric acid (EPA).

The insoluble residue is washed with water on the filter and after neutralization with limestone taken to the dump, and the washing solution containing REE, directed to the production of EPA. Further processing of the concentrate of double sulfates of rare-earth metals and sodium is carried out by conversion to carbonates REM with soda, which regenerate.

The disadvantages of this method are the output from a process in the production of EPA at least 10% leached REM with a wash water insoluble residue FG and from 1.7% productive solution, which reduces the degree of extraction of Σ REM in the concentrate, as well as the direction of the insoluble residue is not for recycling, and in the dump.

A method of refining FG containing phosphorus compounds and lanthanide (EN 2337879 C1, Lokshin AP and others, 10.11.2008). The method includes the leaching of phosphorus and rare earth metal sulfate solution (in particular, 22-30%solution of H₂SO₄within 20-25 min) to obtain supersaturated by lanthanides productive leaching solution and the insoluble residue. The selection of lanthanide concentrate of solution leaching is carried out by crystallization of the double sulphates of lanthanides and sodium while keeping sulfuric acid solution for at least 2 hours Control was obtained mother liquor of crystallization is conducted according to the value of the works is the obsession of phosphorus in solution and sludge moisture gypsum. Purification of the mother liquor from the phosphorus is carried out by introducing compounds of titanium (monohydrate titanylsulphate TiOSO₄·H₂O dry or 60%solution in 34%sulfuric acid solution).

The disadvantages of this method are significant (not less than 10%) loss of rare-earth metals with wet (20%) with deposits of gypsum (insoluble residue), expanding the range of reagents used - titanium compounds, and their regeneration will require the appropriate cost of chemical reagents and accessories, will complicate the process. In addition, the relatively high content of titanium in the sent to the step of leaching the mother solution crystallization (0,67 g/l in terms of TiO₂) leads to wasteful consumption of titanium.

The method for extracting rare-earth metals from FG (EN 2416654 C1, SOC NV and others, 20.04.2011), including its hillshade from phosphorus water carried out in a closed loop with its subsequent utilization by passing a washing solution through the layer of carbonaceous waste (chalk) and return (turnover) depleted in phosphorus water in the washing cycle framework. From washed FG lead leaching of rare earth metals with solutions of sulfuric acid at a concentration from 3 to 250 g/l mode heap leaching. The disadvantage of a very low RMSE is ity filtering water at wash FG from phosphorus, and pls through the layer of FG.

Described is a method of processing FG (see Lokshin EP, Kalinnikov V.T., Tareeva O.A. Extracting rare earth elements from commercial products and industrial waste Khibiny Apatite concentrate Tsvet. 2012. No. 3. P.75-80; and EN 2458999 C1, Lokshin AL. and others, 20.08.2012). The method involves the leaching of REE by filtering 1-5%solutions of sulfuric acid through the layer of FG with getting the leaching solution and the insoluble residue ("purified phosphogypsum"). The insoluble residue is neutralized (in particular, using CaCO₃and in the form of gypsum sent for recycling. From the leaching solution containing in addition to REM and a number of impurities including phosphorus, fluorine, sodium), extract REE sorption on sulfoxides the cation exchanger in the H⁺or. Accumulating sulfate in the mother solution sorption of REE phosphorus and fluorine is removed from the technological process by their precipitation in the form of poorly soluble compounds. After filtering the resulting precipitation sent for recycling, and the aqueous phase (filtrate) in turnover on stage leaching of REE.

There are disadvantages: considerable duration of the leaching of REE, due to very slow infiltration rate sulfate solutions through a layer of FG, and is also a longer duration of water washing the insoluble residue (gypsum) from the residual acidity, phosphorus and REM; the complexity of the operation neutralizing layers (heap) gypsum, particularly limestone.

Known batch leaching FY 5-20% solution of sulfuric acid at W:T=3:1 and a temperature of 20-50°C, and the solution is used for sequential leaching of several portions FG (see sparrows NI, Tatarenkov A.I., Language CENTURIES Extracting rare earth elements from phosphogypsum sulfuric acid // Proc of the Academy of Sciences of Belarus Ser. Hm. N. 1998. N 2. S-106). The disadvantages of the method is the relatively low extraction REM (30%) and the concentration of REE in the final leaching solution (1 g/l), and the need in certain cases to carry out the process by heating (50°C).

The closest in technical essence is the method of extraction of REE from FG (EN 2167105 C1, Lokshin AP and others, 20.05.2001 - prototype), including portions of the sulfuric acid agitation leaching, separation of mother liquor from the solid phase and its reuse for leaching of new portions FG, water washing of the United insoluble residue using a leaching solution during leaching. While leaching of REE from the first portion FG produce 2-6%solution of sulfuric acid at W:T=2-3. When the leaching of each subsequent portion FG of the sulfuric acid concentration in the leach solution will increase in accordance with the increment con is entrale phosphorus pentoxide in the leaching of the previous portion FG. The leaching solution is used at least three times, and the maximum concentration of sulfuric acid in the leaching solution is 24%. Before leaching FY crushed to particle sizes of 100 microns. This way you can reach 4-5 stages batch leaching on average, 32,65-38,68%REM extract from FG.

According to the patent, the method also includes processing solution leaching and his (mother liquor) subsequent use for dissection of Apatite concentrate, i.e. to obtain a wet-process phosphoric acid and leaching of REE.

The disadvantages of this method is the need for strong control and maintain the desired ratio of H₂SO₄and P₂O₅and relatively low extraction of REE from FG in the solution and the difficulty of washing the insoluble residue (gypsum) from moisture with a high concentration of sulphuric acid.

The invention aims to remedy these disadvantages and improve the efficient recovery of REE from FG.

A method of processing FG includes stage campaign sulfuric acid leaching of rare earth metals (REE) and phosphorus feeding sulfuric acid to the main stage, using the obtained solution leaching head stage to subsequent stages of leaching, separation of insoluble mod is and pulp tail stage and water washing, the processing solution leaching tail stage with obtaining a mother liquor, the use of uterine and washing solutions in circulation for leaching.

The difference method is that the REE leaching and phosphorus on the second and subsequent stages is carried out on a mixture of FG and leached slurry previous stage. Sulfuric acid is fed to the head stage leaching in an amount to provide extraction of rare-earth metals and phosphorus in the solution on the head and subsequent stages at pH values at the tail of the leaching step, not to exceed pH to begin precipitation of REE phosphates.

Tail stage leaching of REE and phosphorus lead simultaneously with the processing of the leaching solution by extracting REE sorption by cation; rich REE cation exchange resin is separated from the uterine pulp and is directed to the production of REM concentrate in a known manner.

Before using the mother liquor in the turnover part of pre-cleaned of phosphorus by precipitation of basic calcium compound, and the obtained phosphorus-containing sludge is sent for recycling.

The method can be characterized by the fact that the supply of FG at each stage leaching is performed in the form of a slurry, preferably in the same relation T:W=1:(2-3), and that the leaching process is conducted not less than three stages and what about the simultaneous leaching and sorption of REE are with respect to T:W=1:(2-3).

The method can be characterized by the fact that the REE leaching and phosphorus is carried out at an initial concentration of sulfuric acid in the slurry is in the range of 5-30 wt.% on the head stage and 1-5 wt.%, preferably 1-3 wt.%, on the rear stage, and the fact that the REE leaching, phosphorus is carried out in three stages by applying to each of them is equal to the number of FG in the form of a slurry at T:W=1:(2-3) and the initial concentration of sulfuric acid in the pulp of the head stage leaching within 3-15%, preferably 10-12%.

The method can be characterized also by the fact that on the head stage serves sulfuric acid in an amount to provide at the rear stage of the final acidity of the fallopian pulp in the range from 20 g/l to pH 2, and furthermore, the fact that the sorption of REE are in countercurrent movement of the pulp and of the cation in the cascade of apparatus, provided with a mesh filter to separate the cation exchange resin from the pulp.

The method can be characterized and the fact that in an apparatus for leaching and sorption of REE use type reactor "pacuk". As the cation exchange resin can be used in strongly acidic gel sulfonation marks KU-2-8h.

The method may be characterized, in addition, the fact that the amount allocated for the removal of phosphorus stock solution set of conditions ensuring the maximum concentrations of phosphorus in plants is the ora leaching below the concentration, which starts the deposition of REE phosphates, as well as the fact that as the primary calcium use limestone or quicklime, or hydrated lime, or mixtures thereof.

The technical result is improved efficiency (including leaching of REE from FG) due to more rational use (allocation) of sulfuric acid on the head and subsequent stages of leaching and holding on the tail stage sorption leaching at creating conditions for effective sorption of REE, the exclusion of a number of operations Department (filtering) of the leaching solution during sequential leaching portions FG, prevent the accumulation of phosphorus (and other impurities) by precipitating it from a portion of the circulating mother liquor (mother liquor sorption REM), reducing the loss of REM with moisture insoluble sludge and the reduction of the flow of wash water, ensuring full rotation.

In the patented method takes into account the results of independent experiments performed by the authors of patentable inventions, and AP Lokshin with co-authors described in the above sources, as well as in Art. Malikova, VA and other Extracting rare earth elements from phosphogypsum nitric and sulphuric acids, tzv, 2003, No. 4, p.63-64, and senior Smirnova DI and other Sorption extraction of rare earth elements, yttrium, and aluminum is I'm from a red slime, tzv, 2002, No. 8, p.64-68. They are as follows.

- Increasing the concentration of sulfuric acid in the solution to 22-30 wt.% in the leaching of REE from FG leads to a definite increase the degree of extraction of REE into solution. However, when simultaneous increased content in solution phosphorus and increase the duration of leaching extraction of rare-earth metals can be reduced, probably due to precipitation of dissolved REE in the form of double sulfates of rare-earth metals and sodium, and phosphate REM.

Leaching of REE from FY 22-30%-governmental solutions of H₂SO₄allows after separation of the insoluble residue to obtain a concentrate of REM by spontaneous crystallization of sparingly soluble double sulfates of rare-earth metals and sodium leached from FG and possibly added) during the maturation of the leaching solution according to the reaction:

(REM)₂(SO₄)₃+Na₂SO₄+2H₂O=2Na(REM)(SO₄)₂·H₂O.

However, the duration of the maturation of the solution is not less than 2 h, reaching up to 10-15 hours, when the concentration of sodium in the range of 0.4-1.2 g/l In some cases require the addition of sodium ions in solution, in the form of, for example, Na₂SO₄or soda (Na₂CO₃). The degree of crystallization of REE can be high enough (about 70%).

This reduces the effectiveness of leaching and the production of concentrate R Is M, requires for its crystallization equipment large volume, greatly complicates and increases the cost of water washing the insoluble residue, wet leaching solution with a high concentration of H₂SO₄and REE, leads to a significant watering technological scheme. The preferred concentration of H₂SO₄is 80-120 g/l Increase T:W from 1:1 to 1:5 leads to a certain increase in the extraction of REE from FG in sulfuric acid solution, however, increase the watering process and energy costs, complicated and same increase the separation of the insoluble precipitate. The preferred ratio of T:W=1:(2-3).

- By increasing the temperature to 50-60°C possible slight increase in the extraction of REE in solution, however, when t>60°C - it drops significantly at 5% and more, with increasing energy costs. Preferably the conducting leaching at a temperature in the range of 10-30°C.

- The duration of the leaching of REE from FG is determined by the acidity of the solution, the ratio of T:W, a desired degree of extraction and other parameters, taking into account delivery costs FY, chemicals, materials, water, energy and residue utilization and ranges from 20-30 minutes to 5-6 h, based on the need to achieve the best technical and economic indicators.

Duration is selecive impractical to increase more than 5-6 h in order to avoid spontaneous precipitation from solutions of sulfates REM.

When the concentration of H₂SO₄in leaching solutions in the range of 0.5-4 wt.% double sulfates of rare-earth metals with alkali metals, which are present in FG or can be formed during leaching at room temperature are sufficiently soluble (Epoxy, Vtilennia. About the recovery of REE when the sulfuric acid treatment of the Khibiny Apatite concentrate / Chemical technology, vol.12, No. 1, 2011, p.48-58). It should also be noted that the decrease in the concentration of H₂SO₄in solutions to <2% favorable sorption of REE cationic.

For sorption of REE from sulfuric acid media can be used sulfoxylate, carboxylic and phosphoric acid cation exchangers. However, the maximum capacity by the sum of the oxides of rare-earth metals have generally sulfoxylate cation exchangers, including the strongly acidic sulfonation gel patterns KU-2-8h - available mechanically strong cation exchanger Russian production with acceptable grain size, capacity and kinetic characteristics of the sorption of rare-earth metals from solutions and slurries.

- The optimum pH value of solutions by sorption of REE cation exchange resin KU-2-8h is in the range from 1.0 to 2.2, preferably in the range of 1.0 to 2.0. This eliminates the possibility of starting deposition of rare-earth metals due to hydrolysis (pH>2,2).

- The duration of the process of cation exchange Sorb the AI REM from slurries with achievement of at least 90%of their extraction in the cation exchanger is 6-8 h at t=10-30°C.

In the implementation of a continuous countercurrent sorption of REE can be quite 4-5 stages of sorption with the duration of each of 1.25 h at a ratio of cation:pulp until 3:10 at t=20°C.

- Prevent the accumulation of phosphorus (and other impurities) in the leaching solution is due to the use of treated uterine fluids in the quality of recycled water. This prevents the accumulation of it in the leaching solution to the critical concentration at which there is an appreciable selection in sediment REE.

The precipitate REM fluorides sulfuric acid leaching solutions FG when the real content of REE cations andand F^-anions unlikely. Purification of the circulating water from phosphorus allows, in addition, to reduce the residual fluoride concentration of moisture in the insoluble residue (gypsum). Be aware that in the leaching of REE in the solution passes phosphorus from relatively easily soluble compounds of Ca₅(PO₄)₃F, CaHPO₄, (REM)PO₄·nH₂O, whereas up to 0.3-0.4% of phosphorus in soluble form remains in the insoluble residue.

The figure presents a schematic diagram of processing for FY patent-pending method of implementation, as an example, three successive stages of leaching REE p the simultaneous sorption of REE in the third stage.

The method is as follows. From raw materials - waste FG - prepare the pulp for this purpose, the circulating water (mother solution).

Then cooked pulp (in particular, if T:W=1:(2-3)) goes on stage, for example, three-stage, agitation sulfuric acid leaching of REE. At each stage serves equal, in particular, the number of FG in the form of its original pulp. On the second and third tail stage also serves the pulp is leached in the previous phase. The REE leaching is carried out at an initial concentration of H₂SO₄in the pulp within 5-30% on the head stage and 1-5%, preferably 1-3%) at the rear stage. Leaching head on stage, with an upper limit of 30% of the initial concentration of H₂SO₄in the pulp are in a period of not more than 5 min, and the remaining stages within 15-60 minutes

The preferred initial concentration of sulfuric acid in the pulp of the head stage leaching within 3-15%, and most preferred in the range of 10-12% for the duration of leaching at each stage within 15-60 minutes

To the main stage serves sulfuric acid in an amount to provide a rational degree of leaching of REE from the FG, and the tail stage the pH of the uterine pulp, not exceeding pH to begin precipitation of REE phosphates. The final acid is th uterine pulp may be in the range of from 20 g/l to pH, equal 1-2, i.e. not exceeding the pH of the beginning of the deposition of REE phosphates.

In the pulp tail stage leaching add a cation exchanger, in particular a strongly acidic, gel sulfonation marks KU-2-8h, and carry out the stirring mixture formed in several, for example five hours. At the same time there is cation exchange sorption of not less than 90-95% of the dissolved amount of REM.

Thus, at the rear stage of the exercise REE leaching and phosphorus and simultaneously processing the final leaching solution by extracting REE sorption by cation with getting the mother liquor.

Sorption of REE are in countercurrent movement of the pulp and of the cation in the cascade-type reactors "pacuk"which has a mesh filter to separate the cation exchange resin from the pulp.

Together with REM in leaching solution (aqueous phase of the pulp into a number of related impurities (P, F, Al, Fe, kremachoclet and others), of which phosphorus is limited when disposing of insoluble residue (gypsum).

After the cation exchange sorption (sorption leaching REM) cation exchange resin is separated from the mother of the pulp in the strainer, then filter the pulp separating the insoluble residue (gypsum) and mother liquor. Wet insoluble residue is washed with water and then obrabecim who have a basic calcium compound to pH≈5,5 with its subsequent disposal in a known manner. Use preferably finely ground limestone can be used in anhydrous or hydrated lime, or their mixture.

Water washing of the insoluble precipitate is performed on the filter mode displacement solution that allows for a relatively small consumption of water at T:W=(0,15-0,50):1 - not less than 60-70% of the be removed from the insoluble residue residual acidity, soluble rare-earth metals, phosphorus and other impurities. Received the washing solution, and part of the stock solution used for leaching of REE and phosphorus.

Another part of the mother liquor pre-cleaned of phosphorus (passing from accompanying impurities (Al, Fe, F, kremachoclet etc.)) by processing the basic calcium compound. The obtained phosphorus-containing precipitate is separated, e.g. by filtration from the aqueous phase and sent for recycling in a known manner. The aqueous phase is used for leaching of REE and phosphorus and in the processing of a busy REE cation.

The amount allocated for the purification mother liquor is determined from the conditions prevent the increase of phosphorus concentrations in the leaching solutions above the limit (about 7-9 g/l), which begins with the deposition of REE phosphates. Rich REE cation exchanger is washed using water phase. Then desorbed REM and get them to concentrate known method is m

The achievement of the technical result is proved the following examples of the extraction of rare-earth metals and phosphorus, in which the raw material used FG long (>5 months) storage, which is a product of gray-white color in the form of aggregates of particles, lumps with megarectum cavities and containing, wt.%: 0,44 Σ REM; 1,29 P₂0₅; 0,05 Na; 0,31 Fe_total; 0,35 F.

Example 1. Prepare a starting slurry of phosphogypsum at T:W=1:2, which is mixed with 600 g of phosphogypsum with 1.2 l of a solution-imitant working solution with a concentration, g/l: ~4,6 H₂SO₄; 2,7 P₂O₅.

Conduct stage leaching of REE from the FG to the head (first) stage of leaching of REE for 20 min mix 1/3 the volume of the original slurry containing 200 g FG, while adding to the slurry 22 g H₂SO₄(13 cm³92%H₂SO₄) to bring its pH to 6% H₂SO₄.

The concentration of H₂SO₄and REE in the aqueous phase leached on the head stage of the pulp respectively of 4.75%, 1,38 g/l, and removing the REM - 62,8%.

The second stage leaching is performed due to residual acidity leached pulp first stage when adding 200 g FG in the form of 1/3 of the original volume of the slurry and stirring for 25 min obtained slurry with an initial concentration of H₂SO₄that accounted for the Commissioner to 2.55%.

The concentration of H₂SO₄and REE in the aqueous phase was leached in the second stage of the pulp, respectively 1,95% and 1.35 g/L. removing the REM is to 61.4%.

The third (tail) stage leaching of REE from FY carry out due to residual acidity leached pulp the second stage when adding 200 g FG in the form of 1/3 of the original volume of the slurry and stirring for 300 min obtained slurry with an initial concentration of sulfuric acid ~1.9 per cent. In the pulp type cation exchange resin KU-2-8h in the amount of ~120 cm³in the swollen state (~55 g of air dry). That is, the last stage hold sorption leaching of REE for their residual concentration in the aqueous phase of the slurry is not more than 10 mg/L.

The concentration of sulfuric acid, REE and P₂O₅in the aqueous phase leached pulp, respectively: 1,39%, 0,007 and 6.0 g/l

The REE content in the solid phase (insoluble residue) leached pulp after three stages of leaching was ~0,17%. The saturation of the cation exchange resin REM amounted to ~30 mg/kg

The degree of extraction of rare-earth metals in the leaching solution from the subjected to leaching 600 g FG is ~63,1%, and P₂O₅of 51.2%.

Share leached slurry by filtering the insoluble residue and the aqueous phase mother liquor, part of which is sent to the turnover for the preparation, is the source of pulp FG and so on leaching of REE and phosphorus. The number of stock solution is determined from the conditions prevent the accumulation of phosphorus in solution leaching, leading to the deposition therein of REE phosphates and higher phosphorus content (P₂O₅in the insoluble residue. For this us specific conditions permissible concentration of phosphorus in solution leaching is 7-9 g/l, which allows the use of turnover up to 40-50% sulfuric acid mother liquor.

The insoluble residue with humidity up to ~25% washed with water on the filter mode of the displacement solution at T:W=1:(0.3 to 0.5) for conditioning it for phosphorus and after neutralization with limestone to a pH of 5 is sent for recycling. The washing solution used to prepare the original pulp FG, i.e. leaching from FY REM and phosphorus.

The remaining 50-60% of the mother liquor pre-cleaned of phosphorus (and other impurities) by precipitation of basic calcium compound, in particular limestone and/or CaO. The resulting phosphorus-containing precipitate is filtered and sent for recycling, and the filtrate concentration of the P₂O₅~0.2 g/l used in the back (if necessary, part of it can be withdrawn from the process and disposed of).

Example 2. The process is conducted in accordance with the conditions of Example 1. The difference lies in the fact that lane on the stage leaching REM create in the pulp initial concentration of H ₂SO₄equal to ~8.0%, and by adding 30 g of H₂SO₄(18 cm³92%H₂SO₄).

Leachate concentrations of sulfuric acid and REM in the aqueous phase leached pulp, respectively:

- in the first stage: 6,5%; 1,43 g/l;

- in the second stage: 2,5%; 1,41 g/l;

- on the third (last) stage: 1,65%; 0.008 g/l

The concentration of P₂O₅in the leached pulp - 6.3 g/l, which corresponds to the extraction of P₂O₅from FG in the solution is equal to ~55.8 per cent.

The REE content in the solid phase (insoluble residue) after the first, second and third stages respectively of 0.15; 0.16 and 0.16 per cent, and the degree of recovery of REE from FG in the leaching solution after the first and second stages, respectively 66 and 63.7% and generally from 600 g FG ~63,7%.

Example 3. The process is conducted in accordance with the conditions of Example 1. The difference lies in the fact that prepared the original pulp using 800 g FG, and the leaching is carried out in 4 stages, feeding on every one of them 1/4 the volume of the original pulp. In the first stage leaching REM create a pulp concentration of H₂SO₄equal to 12%, by adding 46 g H₂SO₄(88 cm³92%-H₂SO₄).

Leachate concentrations of H₂SO₄and REE in the aqueous phase leached pulp, respectively:

- in the first stage: 105%; 1.56 g/l;

- in the second stage: 4,4%; 1,49 g/l;

- the third stage: 2,45%; 1,49 g/l;

- on the fourth (last) stage: 1,53%; 0.008 g/l

The content of P₂O₅in the leached slurry to 6.5 g/l, which corresponds to the extraction of R₂About₅from FG in the solution is equal to ~of 58.9%.

The REE content in the solid phase (insoluble residue) after the first, second, third and fourth stages, respectively: 0,13; 0,15; 0,15; 0,15%, the recovery of REE from FG in the leaching solution after the first, second, third stages, respectively, 71; ~66 ~66%, and generally from 800 g FG - 66%.

From the above examples, a patented process ensures the achievement of the technical result and allows you to:

- to increase the recovery of REE from FG by leaching to be carried out in a more rational distribution of H₂SO₄on the head and subsequent stages of leaching, providing no increase in specific consumption increase in the concentration of H₂SO₄on the head stage and reducing the acidity necessary for the implementation of sorption of REE on the tail stage;

- to speed up and simplify the process of extracting rare-earth metals in the solution of the FG due to the simultaneous leaching and sorption of REE, leading to shift the reaction equilibrium towards the formation of compounds of rare-earth metals contained in FG;

- exclude filtering solution is selecive sequential leaching portions FG;

to prevent an accumulation in solutions of phosphorus (and other impurities) by precipitating it from a portion of the circulating mother liquor with the possibility of effective utilization of phosphate sludge and ensure full rotation;

to reduce loss of REM and the flow of wash water due to a sharp decrease in the sorption of REE concentrations (up to <0,01 instead of ~1.5 g/l) moisture insoluble residue, and the residual content of sulphuric acid.

1. The method of processing of phosphogypsum, including stage campaign sulfuric acid leaching of rare earth metals (REE) and phosphorus feeding sulfuric acid to the main stage, using the obtained solution leaching head stage to subsequent stages of leaching, separation of the insoluble residue from the pulp tail stage and water washing, processing solution leaching tail stage with obtaining a mother liquor, the use of uterine and washing solutions in circulation for leaching,
characterized in that
leaching of REE and phosphorus on the second and subsequent stages is carried out on a mixture of phosphogypsum and leached slurry previous stage,
sulfuric acid is fed to the head stage leaching in an amount to provide extraction of rare-earth metals and phosphorus in the solution on the head and p is the following stages at pH values at the tail of the leaching step, do not exceed pH to begin precipitation of REE phosphates,
tail stage leaching of REE and phosphorus lead simultaneously with the processing of the leaching solution by extracting REE sorption by cation exchange resin, saturated REE cation exchange resin is separated from the uterine pulp and is directed to the production of REM concentrate in a known manner,
before using the mother liquor in the turnover part of pre-cleaned of phosphorus by precipitation of basic calcium compound, and the obtained phosphorus-containing sludge is sent for recycling.

2. The method according to claim 1, characterized in that the supply of phosphogypsum at each stage leaching is performed in the form of a slurry, preferably in the same relation T:W=1:(2-3).

3. The method according to claim 1, characterized in that the leaching process is conducted not less than three stages.

4. The method according to claim 1, characterized in that the simultaneous leaching and sorption of REE are with respect to T:W=1:(2-3).

5. The method according to claim 1, characterized in that the leaching of rare-earth metals, phosphorus is carried out at an initial concentration of sulfuric acid in the slurry is in the range of 5-30 wt.% on the head stage and 1-5 wt.%, preferably 1-3 wt.% on the rear stage.

6. The method according to claim 1, characterized in that the leaching of rare-earth metals, phosphorus is carried out in three stages by applying to each of them an equal amount of phosphogypsum in the form of a slurry at T:W=1:(2-3) and IP is one of concentration of sulfuric acid in the pulp of the head stage leaching within 3-15%, preferably 10-12%.

7. The method according to claim 1, characterized in that to the main stage serves sulfuric acid in an amount to provide at the rear stage of the final acidity of the fallopian pulp in the range from 20 g/l to a pH of not more than 2.

8. The method according to claim 1, characterized in that the sorption of REE are in countercurrent movement of the pulp and of the cation in the cascade of apparatus, provided with a mesh filter to separate the cation exchange resin from the pulp.

9. The method according to claim 1, characterized in that in an apparatus for leaching and sorption of REE use type reactor "pacuk".

10. The method according to claim 1, characterized in that the cation exchange resin using a strongly acidic, gel sulfonation marks KU-2-8h.

11. The method according to claim 1, characterized in that the amount allocated for the removal of phosphorus stock solution set of conditions provide the utmost phosphorus concentrations in the leaching solutions below the concentration at which begins the deposition of REE phosphates.

12. The method according to claim 1, characterized in that as the primary calcium use limestone or quicklime, or hydrated lime, or mixtures thereof.