Method for removing sulfate radicals from high-sulfate-radical ionic rare earth concentrate

Abstract

The invention discloses a method for removing sulfate radicals from high-sulfate-radical ionic rare earth concentrate. Belongs to the technical field of rare earth concentrate smelting separation. The method is characterized by comprising the following steps: (1) washing; (2) primary filter pressing; (3) acid dissolution; (4) crystallizing calcium sulfate; (5) secondary filter pressing; (6) adding barium chloride; (7) carrying out third filter pressing; (8) drying at low temperature to obtain dried acid soluble slag; according to the method for removing the sulfate radicals from the high-sulfate-radical ionic rare earth concentrate, materials and equipment are easy to obtain, the cost is low, and the utilization rate of intermediate products can be increased. The method is used for removing sulfate radicals from high-sulfate-radical ion type rare earth ore concentrate.

Description

Technical Field

[0001] This invention relates to a method for removing sulfate from rare earth concentrates, and more specifically, to a method for removing sulfate from rare earth concentrates with high sulfate ion content. Background Technology

[0002] Due to the problem of excessive ammonia nitrogen in soil, magnesium sulfate is gradually replacing ammonium sulfate as the leaching agent for in-situ leaching of ion-adsorption rare earth ores. However, current industrial practice shows that to obtain the same quality of ion-adsorption rare earth concentrate, the amount of magnesium sulfate required is more than twice that of ammonium sulfate, and the residual sulfate content in the concentrate is increased. Ion-adsorption rare earth concentrates are either ion-adsorption rare earth oxides or ion-adsorption rare earth carbonates. When the sulfate content in ion-adsorption rare earth oxides is greater than 2.5%, and the sulfate content in ion-adsorption rare earth carbonates is greater than 0.5%, they are also called high-sulfate ion-adsorption rare earth concentrates.

[0003] Sulfate ions are ubiquitous in brine, industrial wastewater, and domestic and industrial water, and their concentration has a significant impact on subsequent chemical operations and human health. In the rare earth smelting industry, sulfate ions are present in rare earth concentrates and enter the feed solution during the acid dissolution process. Rare earth oxide products have strict limits on sulfate content (less than 50 mg / L), making the removal of sulfate ions from rare earth feed solutions particularly important. Common methods for sulfate removal include sparingly soluble salt precipitation, double salt precipitation, and adsorption.

[0004] (1) Precipitation method of sparingly soluble salts

[0005] Currently, the precipitation method using sparingly soluble salts is widely used to reduce sulfate levels in brine and sulfate-containing wastewater. The main precipitants include calcium chloride, barium chloride, and barium carbonate. Calcium salts significantly affect sulfate removal rates; under suitable reaction conditions, the sulfate concentration in brine solutions can be reduced to less than 5 g / L. This process involves simple equipment and low investment costs. The barium chloride method removes sulfate from solutions; this process is simple and has a high removal rate. The barium carbonate method removes sulfate from wastewater. By controlling the ratio of barium carbonate to sulfate, the reaction temperature, and the stirring rate, the sulfate content can be reduced to below 250 mg / L. Furthermore, barium carbonate is cheaper than barium chloride, thus lowering the cost of removing sulfate from brine.

[0006] (2) Double salt precipitation method

[0007] Electro-driven membrane precipitation involves adding a single salt or a mixture of salts to a solution to form a double salt precipitate with the sulfate in the solution, thereby reducing the sulfate ion content. Currently, calcium sulfate double salt and ettringite double salt are the most studied methods. This study investigated the application of calcium sulfate double salt extraction in old brine. By examining the concentration of the old brine solution, the amount of gypsum added, and the reaction temperature, the advantages of this process are that the gypsum can be reused and the sulfate can be recovered. The ettringite double salt method was also applied to wastewater and mine water, and it was found that under suitable reaction conditions, the sulfate removal rate can reach over 90%. The use of alkaline sludge produced in the ammonia-soda process to remove sulfate from the solution is also explored. In brine or industrial brine with sulfate levels greater than 10 g / L, adding 20-30% of the total solution volume of alkaline sludge can reduce the sulfate ion concentration to below 5 g / L.

[0008] (3) Adsorption method

[0009] The NDS method utilizes inorganic zirconium hydroxide as an adsorbent, achieving a sulfate removal rate of over 90% in brine. Furthermore, by adjusting the adsorbent dosage, it can remove sulfate from brine of any concentration, generates no solid waste, and does not affect the metal anode. Commonly used adsorption methods in China include the lime and PAC combination method, the roasted hydrotalcite adsorption method, the goethite adsorption method, and the ferric hydroxide adsorption method. Due to their low preparation cost and short processing cycle, these methods have significant practical value in treating high-concentration sulfate solutions.

[0010] In the rare earth smelting and separation industry, the common method for removing sulfate ions is by adding barium chloride during the acid dissolution process. This method utilizes the poor solubility of barium sulfate, causing sulfate ions to combine with barium ions to form a precipitate, thus achieving separation. However, this method has significant limitations, especially when processing rare earth concentrates with high sulfate ion content. When using barium chloride to treat rare earth concentrates with high sulfate ion content, not only are large amounts of barium chloride reagent used, but trace amounts of radioactive elements also co-precipitate, resulting in a large amount of radioactive solid waste. The high cost of using large quantities of barium chloride and the need to treat large amounts of low-radioactive acid dissolution slag place a huge economic burden and environmental pressure on rare earth production enterprises. Summary of the Invention

[0011] The purpose of this invention is to address the shortcomings of the prior art by providing a method for removing sulfate from high sulfate ion rare earth concentrates. The materials and equipment used in this invention are readily available and inexpensive, which can reduce the amount of barium chloride reagent used, comprehensively recycle intermediate products, and significantly reduce the weight of low-level radioactive solid waste, thereby reducing the subsequent treatment cost of acid-soluble slag.

[0012] The technical solution of this invention is implemented as follows: a method for removing sulfate ions from high sulfate ion-type rare earth concentrates, characterized in that the method includes the following steps:

[0013] (1) Washing: Add 0.5-5 mg of the high sulfate ion type rare earth concentrate to the concentrate. 3 / t of clean water is used for stirring and washing for 10-120 minutes at a stirring rate of 100-500 rpm to obtain concentrate slurry;

[0014] (2) First-time filter press: The concentrate slurry obtained in step (1) is subjected to filter press treatment to separate the washed concentrate and the wash water;

[0015] (3) Acid dissolution: Slowly add concentrated hydrochloric acid to the washed concentrate obtained in step (2) to adjust the pH to 1-3 and stabilize it, with a stirring speed of 100-500 rpm;

[0016] (4) Calcium sulfate crystallization: Slowly add calcium salt and flocculant to the solution obtained in step (3) and carry out dissolution and crystallization reaction for 1-6 hours. Stir at 100-500 rpm and adjust the pH to 3-5.

[0017] (5) Secondary pressure filtration: The solution obtained in step (4) is subjected to pressure filtration to separate calcium sulfate residue and filtrate;

[0018] (6) Add barium chloride: Add barium chloride to the filtrate obtained in step (5) while stirring and observe the formation of a white precipitate. Stop adding barium chloride when no white precipitate is formed.

[0019] (7) Three-stage pressure filtration: The solution obtained in step (6) is subjected to pressure filtration to separate the acid residue and acid solution;

[0020] (8) Low-temperature drying: The acid soluble residue obtained in step (7) is dried at a low temperature of 50-200 degrees and for 1-12 hours to obtain dried acid soluble residue.

[0021] The above-mentioned method for removing sulfate from high sulfate ion-type rare earth concentrate, wherein the high sulfate ion-type rare earth concentrate in step (1) is an ion-type oxide rare earth or an ion-type carbonate rare earth, and the sulfate content in the ion-type oxide rare earth is greater than 2.5%, or the sulfate content in the ion-type carbonate rare earth is greater than 0.5%.

[0022] In the above-mentioned method for removing sulfate from high sulfate ion-type rare earth concentrate, in step (2), magnesium sulfate with a mass fraction of 3-10% is added to the washing water and stirred to dissolve and prepare a leaching agent for ion-type rare earth ore.

[0023] In the above-mentioned method for removing sulfate from high sulfate ion rare earth concentrate, the calcium salt mentioned in step (4) is any one of calcium hydroxide, calcium chloride, calcium carbonate and calcium oxide.

[0024] In the above-mentioned method for removing sulfate from high sulfate ion rare earth concentrate, the flocculant in step (4) is an organic acid, which is any one of malic acid, gluconic acid, citric acid, lactic acid, tartaric acid, acetic acid and succinic acid.

[0025] In the above-mentioned method for removing sulfate from high sulfate ion rare earth concentrate, the calcium salt concentration in step (4) is set at 0.02-0.1 mol / L, and the flocculant concentration is set at 0.005-0.05 mol / L.

[0026] The above-mentioned method for removing sulfate from high sulfate ion rare earth concentrate, the main components of the calcium sulfate slag in step (5) are calcium sulfate and insoluble minerals, and the calcium sulfate slag will be used as a raw material for gypsum production.

[0027] The above-mentioned method for removing sulfate from high sulfate ion rare earth concentrates, wherein the acid solution in step (7) meets the standards for subsequent rare earth extraction and will be directly used for extraction and separation to obtain a single rare earth solution.

[0028] After adopting the above process, the washing of the concentrate with water can dissolve some of the magnesium sulfate particles on the surface of the concentrate. Therefore, the main component of the washing water is low-concentration magnesium sulfate, which can be used for leaching of ion-adsorption rare earth minerals after adding magnesium sulfate reagent.

[0029] Calcium and sulfate ions can form solid calcium sulfate, so calcium sulfate crystallization is used to remove sulfate ions from the solution. However, in actual production, it was found that in high-concentration rare earth solutions, calcium salts and low-concentration sulfate ions only form colloidal calcium sulfate, which clogs the filter cloth and hinders solid-liquid separation. Therefore, organic acids are added to help calcium sulfate form large-particle crystals, thus facilitating solid-liquid separation. Because organic acids are rich in functional groups such as carboxyl and hydroxyl groups, they can reduce the crystallization ability of calcium sulfate through complexation; organic acids also form rare earth organic acids, reducing the rare earth contact sites on the surface of calcium sulfate colloids, regulating the rare earth concentration on the surface of calcium sulfate, and increasing the crystallization rate. In addition, radioactive elements hardly accompany the crystallization and precipitation of calcium sulfate, thus greatly reducing the yield of low-radioactive solid waste, and the calcium sulfate residue obtained from secondary pressure filtration can be further utilized to obtain gypsum.

[0030] Thermogravimetric analysis revealed that the water content of the acid-soluble residue was as high as 50%, proving that low-temperature drying can further reduce the weight of the acid-soluble residue by 30-50%, thereby reducing the treatment cost of low-radioactive solid waste by 30-50%. Attached Figure Description

[0031] The present invention will be further described in detail below with reference to the embodiments shown in the accompanying drawings, but this does not constitute any limitation on the present invention.

[0032] Figure 1 This is a process flow diagram of the present invention.

[0033] Figure 2 These are X-ray diffraction patterns of the dried acid-soluble residue and calcium sulfate residue obtained during the preparation process of this invention. Detailed Implementation

[0034] See Figure 1 As shown, the present invention discloses a method for removing sulfate ions from high sulfate ion-type rare earth concentrates, characterized in that the method comprises the following steps:

[0035] (1) Washing: Add 0.5-5 mg of the high sulfate ion type rare earth concentrate to the concentrate. 3 Use 1 / t of clean water to stir and wash for 10-120 minutes at a stirring rate of 100-500 rpm to obtain a concentrate slurry. The high sulfate ion-adsorption rare earth concentrate is an ion-adsorption rare earth oxide or an ion-adsorption rare earth carbonate, and the sulfate content in the ion-adsorption rare earth oxide is greater than 2.5%, or the sulfate content in the ion-adsorption rare earth carbonate is greater than 0.5%.

[0036] (2) First-stage pressure filtration: The concentrate slurry obtained in step (1) is subjected to pressure filtration to separate the washed concentrate and the wash water. Magnesium sulfate with a mass fraction of 3-10% is added to the wash water and stirred to dissolve it to prepare a leaching agent for ion-type rare earth ores, which can be used for leaching of ion-type rare earth ores and reduce the cost of raw materials.

[0037] (3) Acid dissolution: Slowly add concentrated hydrochloric acid to the washed concentrate obtained in step (2) to adjust the pH to 1-3 and stabilize it, and stir at a speed of 100-500 rpm.

[0038] (4) Calcium sulfate crystallization: Slowly add calcium salt and flocculant to the solution obtained in step (3) and carry out dissolution and crystallization reaction for 1-6 hours. Stir at 100-500 rpm and adjust the pH to 3-5.

[0039] The calcium salt mentioned therein is any one of calcium hydroxide, calcium chloride, calcium carbonate, and calcium oxide.

[0040] The settling aid is an organic acid, which is any one of malic acid, gluconic acid, citric acid, lactic acid, tartaric acid, acetic acid, and succinic acid.

[0041] The set concentration of the calcium salt is 0.02-0.1 mol / L, and the set concentration of the flocculant is 0.005-0.05 mol / L.

[0042] (5) Secondary pressure filtration: The solution obtained in step (4) is subjected to pressure filtration to separate calcium sulfate residue and filtrate. The main components of the calcium sulfate residue are calcium sulfate and sparingly soluble minerals. The calcium sulfate residue will be used as a raw material for the production of gypsum.

[0043] (6) Add barium chloride: Add barium chloride to the filtrate obtained in step (5) while stirring and observe the formation of a white precipitate. Stop adding barium chloride when no white precipitate is formed.

[0044] (7) Three-stage pressure filtration: The solution obtained in step (6) is subjected to pressure filtration to separate the acid-soluble residue and the acid-soluble liquid. The acid-soluble liquid meets the standards for subsequent rare earth extraction and will be directly used for extraction and separation to obtain a single rare earth liquid.

[0045] (8) Low-temperature drying: The acid soluble residue obtained in step (7) is dried at a low temperature of 50-200 degrees Celsius for 1-12 hours to obtain dried acid soluble residue. The mass of the dried acid soluble residue is reduced by 30-50% compared to the acid soluble residue, and it will be handed over to a professional organization for treatment as low-radioactive solid waste.

[0046] Example 1:

[0047] One ton of ionic rare earth oxides with a sulfate content of 2.7% was subjected to the following treatment, yielding a rare earth acid solution, 62 kg of calcium sulfate slag, and 34 kg of dried acid solution residue. As a control, the same one ton of ionic rare earth oxides underwent conventional sulfate removal treatment, namely, acid dissolution with stirring, addition of barium chloride to remove sulfate, and pressure filtration to obtain an acid solution and acid solution residue, with a residue mass of 128 kg.

[0048] Washing: Add 0.5 mg of the high sulfate ion rare earth concentrate. 3 / t of clean water is used for stirring and washing for 120 minutes at a stirring rate of 110 rpm to obtain concentrate slurry.

[0049] Primary filtration: The obtained concentrate slurry is subjected to pressure filtration to separate the washed concentrate and wash water.

[0050] Acid dissolution: Slowly add concentrated hydrochloric acid to the obtained washed concentrate to adjust the pH to 1 and stabilize it, while stirring at 110 rpm.

[0051] Calcium sulfate crystallization: Slowly add 0.05 mol / L calcium carbonate and 0.02 mol / L malic acid to the solution obtained in the previous step, and carry out the dissolution and crystallization reaction for 5.5 h with a stirring rate of 280 rpm and adjust the pH value to 4.2.

[0052] Secondary pressure filtration: The obtained solution is subjected to pressure filtration to separate calcium sulfate residue and filtrate.

[0053] Add barium chloride: Add barium chloride to the obtained filtrate while stirring and observe the formation of a white precipitate. Stop adding barium chloride when no white precipitate is formed.

[0054] Three-stage pressure filtration: The obtained solution is subjected to pressure filtration to separate the acid-soluble residue and acid-soluble liquid.

[0055] Low-temperature drying: The obtained acid-soluble residue was dried at a low temperature of 150 degrees Celsius for 3 hours to obtain dried acid-soluble residue with a weight reduction of 49%.

[0056] Example 2:

[0057] One ton of ionic rare earth oxides with a sulfate content of 3.0% was subjected to the following treatment to obtain rare earth acid solution, 72 kg of calcium sulfate slag, and 36 kg of dried acid solution residue. As a control, the same one ton of ionic rare earth oxides was subjected to conventional sulfate removal treatment, namely, acid dissolution by stirring, addition of barium chloride to remove sulfate, and pressure filtration to obtain acid solution and acid solution residue, with a mass of 142 kg of acid solution residue.

[0058] Washing: Add 4.8 mg of the high sulfate ion rare earth concentrate. 3 / t of clean water is used for stirring and washing for 15 minutes at a stirring speed of 470 rpm to obtain concentrate slurry.

[0059] Primary filter press: The obtained concentrate slurry is subjected to filter press treatment to separate the washed concentrate and wash water.

[0060] Acid dissolution: Concentrated hydrochloric acid was slowly added to the obtained washed concentrate to adjust the pH to 1.8 and stabilize it, while stirring at a speed of 480 rpm.

[0061] Calcium sulfate crystallization: Slowly add 0.09 mol / L calcium chloride and 0.03 mol / L gluconic acid to the solution obtained in the previous step, and carry out the dissolution and crystallization reaction for 5 hours with a stirring rate of 170 rpm and adjust the pH value to 4.7.

[0062] Secondary pressure filtration: The obtained solution is subjected to pressure filtration to separate calcium sulfate residue and filtrate.

[0063] Add barium chloride: Add barium chloride to the obtained filtrate while stirring and observe the formation of a white precipitate. Stop adding barium chloride when no white precipitate is formed.

[0064] Three-stage pressure filtration: The obtained solution is subjected to pressure filtration to separate the acid-soluble residue and acid-soluble liquid.

[0065] Low-temperature drying: The obtained acid-soluble residue was dried at a low temperature of 90 degrees Celsius for 11 hours to obtain dried acid-soluble residue with a weight reduction of 34%.

[0066] Example 3:

[0067] One ton of ionic rare earth oxides with a sulfate content of 5.2% was subjected to the following treatment, yielding a rare earth acid solution, 82 kg of calcium sulfate slag, and 54 kg of dried acid solution residue. As a control, the same one ton of ionic rare earth oxides underwent conventional sulfate removal treatment, namely, acid dissolution with stirring, addition of barium chloride to remove sulfate, and pressure filtration to obtain an acid solution and acid solution residue, with a residue mass of 228 kg.

[0068] Washing: Add 4.2 mg of the high sulfate ion rare earth concentrate. 3 / t of clean water was used for stirring and washing for 90 minutes at a stirring speed of 120 rpm to obtain concentrate slurry.

[0069] Primary filtration: The obtained concentrate slurry is subjected to pressure filtration to separate the washed concentrate and wash water.

[0070] Acid dissolution: Concentrated hydrochloric acid was slowly added to the obtained washed concentrate to adjust the pH to 2.9 and stabilize it, while stirring at 230 rpm.

[0071] Calcium sulfate crystallization: Slowly add 0.08 mol / L calcium hydroxide and 0.042 mol / L citric acid to the solution obtained in the previous step, and carry out the dissolution and crystallization reaction for 4 hours with a stirring rate of 450 rpm and adjust the pH value to 3.9.

[0072] Secondary pressure filtration: The obtained solution is subjected to pressure filtration to separate calcium sulfate residue and filtrate.

[0073] Add barium chloride: Add barium chloride to the obtained filtrate while stirring and observe the formation of a white precipitate. Stop adding barium chloride when no white precipitate is formed.

[0074] Three-stage pressure filtration: The obtained solution is subjected to pressure filtration to separate the acid-soluble residue and acid-soluble liquid.

[0075] Low-temperature drying: The obtained acid-soluble residue was dried at a low temperature of 120 degrees Celsius for 8 hours to obtain dried acid-soluble residue with a weight reduction of 46%.

[0076] Example 4:

[0077] One ton of ionic rare earth carbonates with a sulfate content of 0.7% was subjected to the following treatment to obtain rare earth acid solution, 21 kg of calcium sulfate slag, and 10 kg of dried acid solution residue. As a control, the same one ton of ionic rare earth oxides was subjected to conventional sulfate removal treatment, namely, acid dissolution by stirring, addition of barium chloride to remove sulfate, and pressure filtration to obtain acid solution and acid solution residue, with a mass of 36 kg of acid solution residue.

[0078] Washing: Add 0.8 mg of the high sulfate ion rare earth concentrate.3 / t of clean water was used for stirring and washing for 60 minutes at a stirring rate of 230 rpm to obtain a concentrate slurry.

[0079] Primary filtration: The obtained concentrate slurry is subjected to pressure filtration to separate the washed concentrate and wash water.

[0080] Acid dissolution: Concentrated hydrochloric acid was slowly added to the obtained washed concentrate to adjust the pH to 2.2 and stabilize it, while stirring at 370 rpm.

[0081] Calcium sulfate crystallization: Slowly add 0.3 mol / L calcium oxide and 0.035 mol / L lactic acid to the solution obtained in the previous step, and carry out the dissolution and crystallization reaction for 3 hours with a stirring rate of 340 rpm and adjust the pH value to 3.2.

[0082] Secondary pressure filtration: The obtained solution is subjected to pressure filtration to separate calcium sulfate residue and filtrate.

[0083] Add barium chloride: Add barium chloride to the obtained filtrate while stirring and observe the formation of a white precipitate. Stop adding barium chloride when no white precipitate is formed.

[0084] Three-stage pressure filtration: The obtained solution is subjected to pressure filtration to separate the acid-soluble residue and acid-soluble liquid.

[0085] Low-temperature drying: The obtained acid-soluble residue was dried at a low temperature of 170 degrees Celsius for 4 hours to obtain dried acid-soluble residue with a weight reduction of 40%.

[0086] Example 5:

[0087] One ton of ionic rare earth carbonates with a sulfate content of 0.9% was subjected to the following treatment, yielding a rare earth acid solution, 27 kg of calcium sulfate slag, and 14 kg of dried acid solution residue. As a control, the same one ton of ionic rare earth oxides underwent conventional sulfate removal treatment, namely, acid dissolution with stirring, addition of barium chloride to remove sulfate, and pressure filtration to obtain an acid solution and acid solution residue, with a residue mass of 42 kg.

[0088] Washing: Add 2.3 mg of the high sulfate ion rare earth concentrate. 3 / t of clean water was used for stirring and washing for 70 minutes at a stirring rate of 340 rpm to obtain a concentrate slurry.

[0089] Primary filtration: The obtained concentrate slurry is subjected to pressure filtration to separate the washed concentrate and wash water.

[0090] Acid dissolution: Concentrated hydrochloric acid was slowly added to the obtained washed concentrate to adjust the pH to 2.6 and stabilize it, while stirring at 410 rpm.

[0091] Calcium sulfate crystallization: Slowly add 0.07 mol / L calcium carbonate and 0.025 mol / L tartaric acid to the solution obtained in the previous step, and carry out the dissolution and crystallization reaction for 2 hours with a stirring rate of 210 rpm and adjust the pH value to 4.9.

[0092] Secondary pressure filtration: The obtained solution is subjected to pressure filtration to separate calcium sulfate residue and filtrate.

[0093] Add barium chloride: Add barium chloride to the obtained filtrate while stirring and observe the formation of a white precipitate. Stop adding barium chloride when no white precipitate is formed.

[0094] Three-stage pressure filtration: The obtained solution is subjected to pressure filtration to separate the acid-soluble residue and acid-soluble liquid.

[0095] Low-temperature drying: The obtained acid-soluble residue was dried at a low temperature of 80 degrees Celsius for 6 hours to obtain dried acid-soluble residue with a weight reduction of 35%.

[0096] Example 6:

[0097] One ton of ionic rare earth oxides with a sulfate content of 4.2% was subjected to the following treatment, yielding a rare earth acid solution, 83 kg of calcium sulfate slag, and 39 kg of dried acid solution residue. As a control, the same one ton of ionic rare earth oxides underwent conventional sulfate removal treatment, namely, acid dissolution with stirring, addition of barium chloride to remove sulfate, and pressure filtration to obtain an acid solution and acid solution residue, with a residue mass of 164 kg.

[0098] Washing: Add 3.6 mg of the high sulfate ion rare earth concentrate. 3 / t of clean water is used for stirring and washing for 40 minutes at a stirring speed of 400 rpm to obtain concentrate slurry.

[0099] Primary filtration: The obtained concentrate slurry is subjected to pressure filtration to separate the washed concentrate and wash water.

[0100] Acid dissolution: Slowly add concentrated hydrochloric acid to the obtained washed concentrate to adjust the pH to 1.5 and stabilize it, while stirring at 180 rpm.

[0101] Calcium sulfate crystallization: Slowly add 0.02 mol / L calcium chloride and 0.05 mol / L acetic acid to the solution obtained in the previous step, and carry out the dissolution and crystallization reaction for 1 hour with a stirring rate of 490 rpm and adjust the pH value to 4.3.

[0102] Secondary pressure filtration: The obtained solution is subjected to pressure filtration to separate calcium sulfate residue and filtrate.

[0103] Add barium chloride: Add barium chloride to the obtained filtrate while stirring and observe the formation of a white precipitate. Stop adding barium chloride when no white precipitate is formed.

[0104] Three-stage pressure filtration: The obtained solution is subjected to pressure filtration to separate the acid-soluble residue and acid-soluble liquid.

[0105] Low-temperature drying: The obtained acid-soluble residue was dried at a low temperature of 200 degrees Celsius for 1.5 hours to obtain dried acid-soluble residue with a weight reduction of 48%.

[0106] Example 7:

[0107] One ton of ionic rare earth carbonates with a sulfate content of 1.2% was subjected to the following treatment, yielding a rare earth acid solution, 29 kg of calcium sulfate slag, and 18 kg of dried acid solution residue. As a control, the same one ton of ionic rare earth oxides underwent conventional sulfate removal treatment, namely, acid dissolution with stirring, addition of barium chloride to remove sulfate, and pressure filtration to obtain an acid solution and acid solution residue, with a residue mass of 63 kg.

[0108] Washing: Add 1.5 mg of the high sulfate ion rare earth concentrate. 3 / t of clean water is used for stirring and washing for 50 minutes at a stirring speed of 220 rpm to obtain concentrate slurry.

[0109] Primary filtration: The obtained concentrate slurry is subjected to pressure filtration to separate the washed concentrate and wash water.

[0110] Acid dissolution: Concentrated hydrochloric acid was slowly added to the obtained washed concentrate to adjust the pH to 1.3 and stabilize it, while stirring at 320 rpm.

[0111] Calcium sulfate crystallization: Slowly add 0.1 mol / L calcium hydroxide and 0.005 mol / L succinic acid to the solution obtained in the previous step, and carry out the dissolution and crystallization reaction for 5 hours with a stirring rate of 120 rpm and adjust the pH value to 3.5.

[0112] Secondary pressure filtration: The obtained solution is subjected to pressure filtration to separate calcium sulfate residue and filtrate.

[0113] Add barium chloride: Add barium chloride to the obtained filtrate while stirring and observe the formation of a white precipitate. Stop adding barium chloride when no white precipitate is formed.

[0114] Three-stage pressure filtration: The obtained solution is subjected to pressure filtration to separate the acid-soluble residue and acid-soluble liquid.

[0115] Low-temperature drying: The obtained acid-soluble residue was dried at a low temperature of 60 degrees Celsius for 12 hours to obtain dried acid-soluble residue with a weight reduction of 32%.

[0116] The above-described embodiments are preferred embodiments of the present invention and are only used to facilitate the illustration of the present invention. They are not intended to limit the present invention in any way. Any person skilled in the art who makes local modifications or alterations to the technical content disclosed in the present invention without departing from the scope of the technical features of the present invention shall still fall within the scope of the technical features of the present invention.

Claims

1. A method for removing sulfate ions from high sulfate ion-type rare earth concentrates, characterized in that, The method includes the following steps: (1) Washing: Add 0.5-5 mg of the high sulfate ion type rare earth concentrate to the concentrate. 3 / t of clean water is used for stirring and washing for 10-120 minutes at a stirring rate of 100-500 rpm to obtain concentrate slurry; (2) First-time filter press: The concentrate slurry obtained in step (1) is subjected to filter press treatment to separate the washed concentrate and the wash water; (3) Acid dissolution: Slowly add concentrated hydrochloric acid to the washed concentrate obtained in step (2) to adjust the pH to 1-3 and stabilize it, with a stirring speed of 100-500 rpm; (4) Calcium sulfate crystallization: Slowly add calcium salt and flocculant to the solution obtained in step (3) and carry out dissolution and crystallization reaction for 1-6 hours. Stir at 100-500 rpm and adjust the pH to 3-5. (5) Secondary pressure filtration: The solution obtained in step (4) is subjected to pressure filtration to separate calcium sulfate residue and filtrate; (6) Add barium chloride: Add barium chloride to the filtrate obtained in step (5) while stirring and observe the formation of a white precipitate. Stop adding barium chloride when no white precipitate is formed. (7) Three-stage pressure filtration: The solution obtained in step (6) is subjected to pressure filtration to separate the acid residue and acid solution; (8) Low-temperature drying: The acid soluble residue obtained in step (7) is dried at a low temperature of 50-200 degrees and for 1-12 hours to obtain dried acid soluble residue.

2. The method for removing sulfate from high sulfate ion-type rare earth concentrate according to claim 1, characterized in that, The high sulfate ion-type rare earth concentrate in step (1) is an ion-type oxide rare earth or an ion-type carbonate rare earth, and the sulfate content in the ion-type oxide rare earth is greater than 2.5%, or the sulfate content in the ion-type carbonate rare earth is greater than 0.5%.

3. The method for removing sulfate from high sulfate ion-type rare earth concentrate according to claim 1, characterized in that, In step (2), magnesium sulfate with a mass fraction of 3-10% is added to the washing water and stirred to dissolve and prepare a leaching agent for ionic rare earth minerals.

4. The method for removing sulfate from high sulfate ion-type rare earth concentrate according to claim 1, characterized in that, The calcium salt mentioned in step (4) is any one of calcium hydroxide, calcium chloride, calcium carbonate and calcium oxide.

5. The method for removing sulfate from high sulfate ion-type rare earth concentrate according to claim 1, characterized in that, The flocculant mentioned in step (4) is an organic acid, which is any one of malic acid, gluconic acid, citric acid, lactic acid, tartaric acid, acetic acid and succinic acid.

6. A method for removing sulfate from high-sulfate ion-type rare earth concentrates according to claim 1, 4, or 5, characterized in that, The set concentration of the calcium salt in step (4) is 0.02-0.1 mol / L, and the set concentration of the flocculant is 0.005-0.05 mol / L.

7. The method for removing sulfate from high sulfate ion-type rare earth concentrate according to claim 1, characterized in that, The main components of the calcium sulfate slag mentioned in step (5) are calcium sulfate and insoluble minerals. The calcium sulfate slag will be used as a raw material for the production of gypsum.

8. The method for removing sulfate from high sulfate ion-type rare earth concentrate according to claim 1, characterized in that, The acid solution described in step (7) meets the standards for subsequent rare earth extraction and will be directly used for extraction and separation to obtain a single rare earth solution.

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