Classifications

• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
  • C22B59/00—Obtaining rare earth metals
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01F—COMPOUNDS OF THE METALS BERYLLIUM, MAGNESIUM, ALUMINIUM, CALCIUM, STRONTIUM, BARIUM, RADIUM, THORIUM, OR OF THE RARE-EARTH METALS
  • C01F17/00—Compounds of rare earth metals
  • C01F17/20—Compounds containing only rare earth metals as the metal element
  • C01F17/206—Compounds containing only rare earth metals as the metal element oxide or hydroxide being the only anion
• • Y—GENERAL 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
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
  • Y02P10/00—Technologies related to metal processing
  • Y02P10/20—Recycling

Definitions

• the invention relates to the field of disposal of industrial waste and environmental protection and can be used in the chemical industry, in the production of building materials, as well as in other manufacturing sectors associated with the use of gypsum binders and rare-earth elements.
• REM rare-earth metals
• a known method for the extraction of rare-earth metals from phosphogypsum including the processing of phosphogypsum with a solution of sulfuric acid, filtration and the absorption of the sum of rare-earth metals from the resulting solution [1].
• the degree of extraction of rare-earth metals from solution does not exceed 71%.
• the disadvantages of the method are the low degree of extraction of rare-earth metals from the sulfate solution after processing of phosphogypsum, the high cost of the ion exchanger, the duration of the process and large material flows, which does not allow us to recommend it for industrial use.
• the presence of active silicon impurities in the sulfuric acid filtrate from washing phosphogypsum leads to rapid clogging of the pores of the sorbent and its frequent replacement.
• An increase in the degree of supersaturation of the solution is achieved by providing the sodium content in the solution of 0.4-1.2 g / l.
• a known method for the extraction of rare-earth metals from phosphogypsum by leaching with sulfuric acid solutions, followed by neutralization with a mixture of gaseous ammonia with air with the release of phosphates of rare-earth metals [3].
• This method of processing provides extraction of rare-earth metals in an amount of only 15%.
• the injected crude phosphate concentrate contains not more than 70% rare-earth metals, a significant amount of impurities of calcium fluorides and phosphates, silicon oxide, etc., which complicates its further processing to obtain commercial-grade rare-earth metals.
• the main disadvantage of this method is to obtain a finely dispersed poorly thickened and filtered low-quality concentrate of REM fluorides, which complicates its processing to a product of commercial purity and leads to significant capital and operational costs.
• the reagent used for the precipitation of rare-earth metals - hydrofluoric acid is a relatively expensive reagent and, according to its toxic properties, belongs to the first hazard class.
• the use of the mother liquor after separation of the fluoride precipitate as a sulfuric acid solution for treating phosphogypsum is also limited due to the accumulation of fluorides, phosphates and other impurities in it, which contribute to a decrease in the degree of rare-earth metal extraction into the solution. That is, that part of the sulfuric acid solution must be removed from the process of washing phosphogypsum from rare-earth metals and disposed of.
• oxalic acid or its soluble salts in the amount of 250-300% of the stoichiometry on rare-earth metals as a precipitating reagent when neutralizing the sulfuric acid solution to a pH value of 1.0–2.5 makes it possible to isolate rare earth oxalates from the sulfuric acid solution after processing phosphogypsum in the form of a well formed crystalline precipitates that are easily separated from the mother liquors by thickening and filtration and after washing, drying and calcining contain 95-98% of rare earth oxides (REO) and can be used in as a marketable product or in the technology for the separation of a group of rare-earth concentrate to produce individual rare-earth elements.
• the filtrate after separation of the solid phase - REM oxalates can be used for the production of gypsum binder.
• Phosphogypsum was dried in an oven at 120 ° C to constant weight and analyzed for impurities.
• the filtrate was collected in a beaker, the yield, sulfuric acid content, concentration of cerium, rare-earth metals, fluorine and phosphorus pentoxide were determined. The results of the analysis are shown in table 1.
• Table 1 The composition of the filtrate obtained after processing phosphogypsum solution
• the content of REO in the concentrate is 95.7%.
• the filtration capacity of the pulp is 0.150 m 3 / m 2 per hour, the sediment humidity is 20%.
• the degree of extraction of REE from the solution is 96.7%.
• Example 2 To determine the lower boundary of the claimed consumption range of the precipitant, 400 ml of the sulfate filtrate obtained in Example 1 were taken, placed in a beaker, 1.5 g of oxalic acid (150% of stoichiometry to REO) was added and stirred on a magnetic stirrer at a temperature of 25 -30 ° C until complete dissolution, after which the precipitation of RZK was carried out in the sequence and mode of example 1. Then repeated the experiment with a rate of precipitation of 200%. The experimental results are shown in table 3.
• oxalic acid 150% of stoichiometry to REO
• Example 3 To determine the upper limit of the claimed range of precipitant consumption, 400 ml of the sulfate filtrate obtained in experiment 2 were taken, placed in a beaker, 4.0 g of oxalic acid (400% mol.) was added from stoichiometry to REO) and stirred on magnetic stirrer at a temperature of 25-30 ° C until complete dissolution, after which the REM deposition was carried out in the sequence and according to the parameters of test mode 2. The experimental results are also shown in Table 3. Table 3 — Dependence of the degree of REM extraction and the composition of REM on the rate of precipitator consumption.
• the optimal consumption rate should be considered 250-300% (mol.) Of precipitant - oxalic acid or its salts to the amount of rare-earth metals.
• 95.3-96.7% of rare-earth metals are precipitated in rare-earth metals, and the resulting rare-earth metals contain more than 95.0% rare-earth metals.
• An increase in the rate of consumption of the precipitant up to 400% does not lead to a significant increase in the degree of REE extraction, but at the same time co-precipitation of associated impurities occurs, which reduces the quality of the REE and leads to additional costs for its production.
• Example 4 To determine the lower boundary of the pH of the precipitation of rare-earth metals, 400 ml of the sulfate filtrate obtained in Example 1 were taken, placed in a beaker, 3.0 g of oxalic acid (300% (mol.) From stoichiometry to REO) were added and stirred on a magnetic stirrer at a temperature of 25-30 ° C until complete dissolution, after which an aqueous solution of ammonia neutralized the solution to a pH of 0.90 and then carried out precipitation of RZK in the sequence and according to the parameters of test mode 2. Then the experiment was repeated with a pH of 1.0 precipitation of RZK. The experimental results are shown in table 4.
• Example 5 To determine the upper boundary of the claimed pH range of RZK deposition, 400 ml of the sulfate filtrate obtained in Example 1 were taken, placed in a beaker, 3.0 g of oxalic acid (300% (mol.) From stoichiometry to REO was added and mixed on magnetic stirrer at a temperature of 25-30 ° C until complete dissolution, after which an aqueous solution of ammonia neutralized the solution to a pH of 2.5 and then carried out the precipitation of the rare-earth metals in the sequence and mode parameters of example 1. The results are shown in table 4.
• the inventive region of the pH of the precipitation of REE - 1.0-2.5 provides a fairly complete and selective selection of REE in the solid phase.
• the degree of extraction of rare-earth metals sharply decreases, with an increase in the selectivity of the process of separation of rare-earth metals, which is accompanied by coprecipitation of related impurities in the rare-earth metals and a decrease in the quality of the commercial product.
• the degree of extraction into solution is up to 99.9%, and the REO content in the concentrate is up to 95-98%.
• an even more important factor is the increase in the rate of filtration of RZK sediments.
• the sludge sedimentation rate (1.5 - 4.0 m / m-hour) for the recommended regime is much higher than the sedimentation rate with the known deposition method. This indicator is important in industrial technology management, as allows for large volumes of solutions to provide the required performance at a relatively low capital cost using known filtering equipment.
• the consumption of fresh sulfuric acid for the treatment of phosphogypsum can be significantly reduced if the solid phase of phosphogypsum is washed with water after separation from the sulfuric acid solution and at least part of the wash water washed with residual sulfuric acid from phosphogypsum is returned to the processing of the next load of phosphogypsum.
• up to 50% of the sulfuric acid spent on the treatment of phosphogypsum can be added as part of the circulating wash water.
• Example 6 1379 g dump phosphogypsum of the Gomel chemical plant composition in terms of dry matter, in%: F o6m - 0.34; REO - 0.493; P 2 0 5 ° bsch- - 0.46, moisture 27.5 treated with 108 g of 98% sulfuric acid with the introduction in 1410 g promvody obtained after washing the filter cake with water phosphogypsum experience in the previous cycle. Then the production pulp was filtered and the resulting 1669 g wet cake was washed on the filter with 1405 ml of water. The resulting promoter in the amount of 1410 g was left to return to phosphogypsum treatment in the next cycle.
• the washed phosphogypsum cake in an amount of 1665 g was dried in an oven at 120 ° C to constant weight and analyzed for the content of rare-earth metals and other impurities.
• the main filtrate was collected in a beaker, the yield was determined and analyzed for components. The results are shown in summary table 5.
• Example 7 1379 g of dump phosphogypsum of the Gomel chemical plant with a moisture content of 27.5% of the previous composition was treated as in example 6, the washing solution was prepared from 77 g of 98% sulfuric acid, introduced into 1410 g of the product obtained after washing the filtered phosphogypsum cake with water in the previous cycle of example 7, and 321 g of a circulating sulfate solution left from the previous cycle of experience. Then the production pulp was filtered, the resulting wet cake (1670 g) was washed on the filter with 1406 ml of water. Wash water in an amount of 1410 g was left for return to phosphogypsum treatment in the next cycle.
• the washed phosphogypsum cake in an amount of 1665 g was dried in an oven at 120 ° C to constant weight and analyzed for the content of REE and other impurities.
• the main filtrate was collected in a beaker, the yield was determined and analyzed. Then 321 g of the main filtrate was separated and left as a circulation solution for the next cycle of Example 7, and the remaining 1010 g was used as a production solution for the isolation of RZK from it.
• the results of example 7 for the processing of phosphogypsum are shown in summary table 5.
• Example 8 1379 g of dump phosphogypsum of the previous composition was treated as in the previous examples.
• the wash solution was prepared from 55 g of 98% sulfuric acid introduced into 1410 g of the stain obtained after washing the filtered phosphogypsum cake with water in the previous cycle of Example 8 and 626 g of the circulating sulfate solution left from the previous cycle of Example 8. Then, the production pulp was filtered. The resulting wet cake in the amount of 1668 g was washed on the filter with 1404 ml of water, the industrial dressing in the amount of 1408 g was left to return to phosphogypsum treatment in the next cycle.
• the washed cake of phosphogypsum - 1666 g was dried in an oven at 120 ° C to constant weight and analyzed for the content of REE and other impurities.
• the main filtrate was collected, the yield was determined and analyzed.
• 626 g of the main filtrate was separated and left as a circulating solution for the next cycle of Example 8, and the remaining part in the amount of 705 g was used as a production solution at the stage of separation of RZK from it.
• the results of experiment 4 on the processing of phosphogypsum are shown in summary table 5.
• Table 7 The results of experiments on the treatment of phosphogypsum with sulfuric acid and circulating solutions with the incorporation of rare-earth oxalates from production solutions.
• the proposed method for the extraction of rare-earth metals from phosphogypsum using recycled sulfuric acid with a circulating sulfuric acid solution allows, in addition to saving acid (up to 50%) and improving the quality of rare-earth metals, to reduce the volume of production sulfate solution by more than 2 times, which plays a significant role in the isolation RZK from a solution of ammonium sulfate, as well as during further processing of this solution.
• Patent RU J4 "2293781, C 22 V 59/00, 2007;

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