Rare earth recovery method of ionic rare earth acid soluble slag

Abstract

The invention discloses a rare earth recovery method of ionic rare earth acid-soluble slag, which comprises the following steps: adding water into ionic rare earth concentrate acid-soluble slag for size mixing to obtain mixed slurry; adding a sodium hydroxide solution with the concentration of 50-100g / L into the mixed slurry for alkaline conversion, filtering and washing to obtain first wastewater and an alkaline cake; water is added into the alkali cake for size mixing, alkali cake slurry is obtained, the solid-liquid weight ratio of the alkali cake to the water is 1: (1-2), the alkali cake slurry is heated for acid dissolution, the pH is controlled to be 0.5-1.0, and a rare earth crude product solution is obtained after filtering and water washing; precipitating the rare earth crude product solution with an oxalic acid solution, filtering, and washing to obtain second wastewater and an oxalic acid rare earth mixture; and firing the oxalic acid rare earth mixture at a high temperature to obtain the mixed rare earth oxide. The process is simple in technology, short in flow, less in three wastes, stable and reliable in operation and low in cost, and the rare earth recovery rate reaches 90% or above.

Description

Technical Field

[0001] The invention relates to the technical field of comprehensive utilization and treatment of ionic rare earth solid waste, and in particular to a rare earth recovery method of ionic rare earth acid slag. Background Art

[0002] During the production process of the separation plant, the ionic rare earth concentrate is first dissolved with hydrochloric acid to form a high-concentration mixed rare earth liquid, which contains slag that is not dissolved by dilute hydrochloric acid and additives added for impurity removal, called acid slag. Acid slag contains mechanical impurities such as heavy metals, fluorides, silicates, barium sulfate, sand and gravel, as well as radioactive substances containing trace amounts of uranium and thorium. In the acid slag, impurity particles will adsorb and entrain a small amount of rare earth ions, and rare earth ions will form acid-insoluble substances such as fluorides; in addition, during the washing, filtration and dehydration process of the acid slag, a small amount of liquid rich in rare earth elements will be retained in the slag, causing the loss of rare earth elements. The dry slag of the acid slag contains a high content of rare earth (REO), and contains a high proportion of rare earth elements such as praseodymium, neodymium, terbium, dysprosium, holmium, erbium, and lutetium, which has a high economic value. The rare earth elements in the acid slag have become important rare earth resources. Rare earths are important non-renewable strategic resources. Failure to recycle acid-soluble slag will reduce the rare earth production yield and affect corporate profitability. Research on technical methods for recovering rare earth elements from acid-soluble slag will have a significant impact on the rare earth separation industry.

[0003] Ionic rare earth concentrate acid slag is the insoluble residue after the concentrate is dissolved in hydrochloric acid, as well as impurities such as barium sulfate precipitate produced when barium chloride is added to remove sulfate ions and aluminum hydroxide formed after aluminum removal. The rare earth elements in the acid slag are mainly rare earth ions adsorbed by particulate impurities during precipitation, some rare earth fluorides and trace rare earth compounds in other forms. The entrained rare earth ions can be recovered by water washing or acid washing, but since the filtration equipment cannot fully recover the solution during solid-liquid separation, some rare earth element-containing solutions still remain in the impurities, causing a small amount of rare earth loss; and rare earth fluoride is insoluble in ordinary low-boiling acid such as hydrochloric acid and nitric acid. It needs to use an acid with a higher boiling point and stronger acidity to remove fluorine at high temperature to recover the rare earth. Therefore, ordinary single acid can only dissolve a small amount of soluble rare earth, and it is difficult to dissolve the rare earth fluoride, and it is impossible to recover the rare earth elements in the acid slag to the maximum extent.

[0004] The existing technical solution process is: acid dissolution of ionic rare earth concentrate → strong acid activation acid dissolution → multi-stage countercurrent acid washing of filter residue + countercurrent water washing → solid-liquid separation → filtrate plus oxalic acid precipitation → oxalate rare earth enrichment → high temperature calcination → mixed rare earth oxide. In the above process, the strong acid or mixed acid used for the activation acid dissolution of the ionic rare earth concentrate acid dissolution has high requirements for reaction conditions, incomplete and insufficient defluorination of fluorinated rare earths, and low rare earth recovery rate; and the use of highly corrosive and oxidizing sulfuric acid and highly corrosive and explosive perchloric acid has harsh and strict requirements for on-site production conditions, and there are great safety and environmental risks. Summary of the invention

[0005] (I) Purpose of the invention

[0006] The purpose of the present invention is to provide a rare earth recovery method for ionic rare earth acid slag, which solves the problem of low rare earth element recovery rate in the existing ionic rare earth concentrate acid slag, and has good impurity removal effect, safe production process, environmental protection and low cost.

[0007] (II) Technical solution

[0008] In order to solve the above problems, the first aspect of the present invention provides a rare earth recovery method from ionic rare earth acid slag, comprising the following steps:

[0009] S1, adding water to the ionic rare earth concentrate acid slag to prepare a slurry to obtain a mixed slurry, wherein the solid-liquid weight ratio of the ionic rare earth concentrate acid slag to water is 1:1-2;

[0010] S2, adding sodium hydroxide solution to the mixed slurry for alkali conversion, filtering and washing to obtain first wastewater and alkali cake, wherein the concentration of the sodium hydroxide solution is 50-100 g / L;

[0011] S3, adding water to the alkali cake to prepare a slurry to obtain an alkali cake slurry, wherein the solid-liquid weight ratio of the alkali cake to water is 1:1-2, the alkali cake slurry is heated and acid-dissolved, the pH value is controlled to be 0.5-1.0, and the crude rare earth product solution is obtained after filtering and washing;

[0012] S4, precipitating the crude rare earth product solution with an oxalic acid solution, filtering and washing with water to obtain a second wastewater and an oxalate rare earth mixture;

[0013] S5, calcining the rare earth oxalate mixture at high temperature to obtain mixed rare earth oxides.

[0014] Furthermore, the mass fraction of rare earth in the ionic rare earth concentrate acid slag is 3-15wt%.

[0015] Furthermore, in the step S2, the mixed slurry is heated and alkali-converted in an alkali-resistant enamel reactor, and the alkali-conversion reaction temperature is controlled to be 100-110° C. and the alkali-conversion reaction time is 1-2 hours.

[0016] Furthermore, the step S2 further comprises: performing sedimentation treatment on the first wastewater:

[0017] Add lime milk solution to the first wastewater for defluorination precipitation, then add sodium metaphosphate and aluminum salt for further defluorination precipitation, and after the precipitate is precipitated, adjust the pH value of the first wastewater to meet the standard before discharging.

[0018] Furthermore, in step S3, the acid dissolution includes: adding hydrochloric acid, controlling the acid dissolution heating temperature to 90-95° C., and controlling the stirring time to 1-2 h.

[0019] Furthermore, the pH value of the first wastewater is controlled to be 6-9.

[0020] Furthermore, in the step S3, the alkali cake slurry is heated and acid-dissolved in a glass fiber reinforced plastic reaction tank.

[0021] Furthermore, the content of oxalic acid substance in the oxalic acid solution is 100-200 g / L.

[0022] Furthermore, the molar ratio of the oxalic acid substance in the oxalic acid solution to the rare earth substance in the crude rare earth solution is 3 to 5:1.

[0023] Furthermore, in step S5, the burning temperature is 900-1000° C., and the burning time is controlled to be 1-2 hours.

[0024] (III) Beneficial effects

[0025] The above technical scheme of the present invention has the following beneficial technical effects: adding water to the acid-soluble slag of the ionic rare earth concentrate to prepare a slurry, first adding a sodium hydroxide solution to perform alkaline conversion to remove fluorine, and preparing a sodium hydroxide concentration of 50-100 g / L to ensure sufficient fluorine removal, a safe and environmentally friendly production process, and avoiding the use of highly corrosive and highly oxidizing sulfuric acid and highly corrosive and explosive perchloric acid. At the same time, part of the aluminum and silicon impurities are converted into soluble acid radicals and the like and are removed by filtering and washing with water, and the rare earth and the calcium, thorium, iron, etc. in the slag are retained in the solid precipitate in the form of hydroxides to form an alkali cake, and then the alkali cake slurry is acid-dissolved, and the pH is controlled to be 0.5-1.0. During the acid dissolution process, the rare earth and impurities such as calcium, thorium, iron, etc. are dissolved to obtain a rare earth crude product solution, and an oxalic acid solution is added to the rare earth crude product solution for precipitation to obtain an insoluble oxalic acid rare earth mixture, and finally calcined at a high temperature of 900-1000° C. to obtain a mixed rare earth oxide. The process technology of the present invention is simple, the process is short, the rare earth recovery rate is more than 90%, the three wastes are less, the operation is stable and reliable, and the cost is low (the cost of recovering rare earths from acid slag is less than 40,000 yuan / ton REO). Calculated at a price of 140,000 to 200,000 yuan / ton REO, for every ton of REO recovered, a profit of about 100,000 to 160,000 yuan can be obtained, the economic benefit is considerable, the process is safe and environmentally friendly, and the output and quality are guaranteed. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a process technology schematic diagram of a rare earth recovery method from ionic rare earth acid slag provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0027] In order to make the purpose, technical scheme and advantages of the present invention clearer, the present invention is further described in detail below in conjunction with specific embodiments and with reference to the accompanying drawings. It should be understood that these descriptions are only exemplary and are not intended to limit the scope of the present invention. In addition, in the following description, the description of well-known structures and technologies is omitted to avoid unnecessary confusion of the concept of the present invention.

[0028] The present invention provides a rare earth recovery method from ionic rare earth acid slag, comprising the following steps:

[0029] S1, adding water to the ionic rare earth concentrate acid slag to prepare a slurry to obtain a mixed slurry, wherein the solid-liquid weight ratio of the ionic rare earth concentrate acid slag to water is 1:1-2. In this step: the mass fraction of rare earth in the ionic rare earth concentrate acid slag is 3-15wt%, and the content of the ionic rare earth concentrate acid slag slurry material is 500-1000g / L, and the slurry concentration is maintained so that the reaction can be fully carried out and the slurry will not be formed, and the subsequent addition of sodium hydroxide solution can also reach a certain concentration;

[0030] S2, adding sodium hydroxide solution to the mixed slurry for alkali conversion, filtering and washing to obtain the first wastewater and alkali cake, wherein the concentration of the sodium hydroxide solution is 50-100g / L, and the ratio of the amount of solid slag in the mixed slurry to the solid amount of sodium hydroxide is 5-10:1, because the appropriate alkali content ratio can keep the slurry at a certain alkali concentration, this concentration can make the fluorine removal more thorough, reaching a defluorination rate of more than 90%, in this step: the alkali cake is an alkali cake for removing soluble fluoride, and in addition, the concentration of the sodium hydroxide solution is set to 50-100g / L because the fluorine content of 0.1%-1% in the acid slag is relatively low. The concentration can dissolve as much fluoride ions as possible, the defluorination effect will be better, and the defluorination rate reaches more than 90%. The present invention is to heat the mixed slurry for alkali conversion by an alkali-resistant enamel reactor, the enamel reactor is alkali-resistant and high-temperature-resistant, and is equipped with a steam heating function. The heating can promote the chemical reaction faster and can meet the reaction requirements to the greatest extent. The alkali conversion reaction temperature is set to 100-110°C (in a boiling state at this temperature), and the alkali conversion reaction time is controlled to be 1-2h. By maintaining the reaction temperature and duration to ensure full reaction, the defluorination rate reaches more than 90%. In addition, the present invention also absorbs the volatilized gas of the heating reaction by setting a spray absorption tower, and the volatile gas includes the acidic gas brought in by the rare earth acid slag and the alkaline gas formed by sodium hydroxide to prevent air pollution; when washing, the solid-liquid weight ratio is 1:2-4, the number of washings is 3-4 times, and the washing water is kept in countercurrent use. The solid-liquid ratio uses less water, and by controlling the number of washings, the best defluorination washing effect can be achieved; the sodium hydroxide in step S2 can also be replaced by sodium carbonate, potassium hydroxide or potassium carbonate, etc.

[0031] S3, adding water to the alkali cake to prepare a slurry to obtain an alkali cake slurry, wherein the solid-liquid weight ratio of the alkali cake to water is 1:1-2, the alkali cake slurry is heated and acid-dissolved, the pH value is controlled to be 0.5-1.0, and a crude rare earth solution is obtained after filtering and washing. In this step: the solid-liquid ratio of the alkali cake slurry to the acid solution is 2:1-1.5, and the crude rare earth solution is a rare earth acid solution containing partially soluble hydroxides (the crude rare earth solution contains RE 3+ , Fe 3+ ,Th 4+ , Ca 2+ The rare earth in hydroxide state has been dissolved into ionic form, but a very small part of rare earth in other forms cannot be dissolved, so it is called rare earth containing partially soluble hydroxide). The substance content of the alkali cake slurry is 500-1000g / L, because when the concentration of the sodium hydroxide solution is set to 50-100g / L, the concentration of the alkali cake slurry can be maintained, the reaction can be fully carried out, and the slurry will not be solidified, and the subsequent addition of acidic substances can reach a certain concentration (if the alkali concentration is too high, the alkali is excessive, then the subsequent addition of acid will consume more acid and increase the cost). Acid dissolution includes: adding hydrochloric acid, the concentration of hydrochloric acid is 1-3mol / L, because the rare earth content is relatively low, the increase in the acid content ratio can make the mixing more uniform, and the rare earth dissolution effect will be better; under the condition of high concentration acid solution, the rare earth dissolution chemical reaction can be more fully carried out, and the dissolution rate reaches more than 95%, so the hydrochloric acid concentration is set to 1-3mol / L, which can dissolve soluble hydroxide rare earth and other substances, and the rare earth ion dissolution rate is high. In this step, the acid dissolution heating temperature is controlled to be 90-95°C, and the stirring time is controlled to be 1-2h. By maintaining the reaction temperature and the stirring time to ensure that the acid dissolution is fully reacted, the rare earth dissolution rate reaches more than 95%. In addition, the alkali cake slurry is heated and acid-dissolved by a glass fiber reinforced plastic reaction tank. The glass fiber reinforced plastic reaction tank is acid-resistant and high-temperature-resistant, and is equipped with a steam heating function. The heating can promote the chemical reaction faster and meet the reaction requirements. In addition, the gas volatilized by the heating reaction is absorbed by a spray absorption tower. The volatile gas includes the acid gas volatilized by the acid dissolution reaction and other gases such as carbon dioxide generated to prevent atmospheric pollution. When washing with water, the solid-liquid weight ratio is 1:2-4, the number of water washings is 3-4 times, and the washing water is kept in countercurrent use. The principle is the same as above.

[0032] S4, the crude rare earth solution is precipitated with oxalic acid solution, filtered and washed to obtain the second wastewater and oxalic acid rare earth mixture, in this step: the content of oxalic acid substance in the oxalic acid solution is 100-200g / L, the temperature during precipitation is set to 60-80℃, stirring for 1-2h, and under this stirring time, maintaining the precipitation reaction temperature can ensure sufficient reaction, and the precipitation rate can reach 100%. The molar ratio of oxalic acid in the oxalic acid solution to the rare earth in the crude rare earth solution is 3-5:1. The rare earth content is relatively low, and the oxalic acid content ratio is increased to make the mixing more uniform, and the precipitation effect will be better; under high concentration oxalic acid conditions, the rare earth ion precipitation chemical reaction can be more fully carried out, and the precipitation rate can reach 100%. In step S4, the mixed slurry is heated and precipitated by an acid-resistant glass fiber reinforced plastic reaction tank. When washing with water, the solid-liquid weight ratio is 1:2-4, the number of washings is 3-4, and the washing water is kept in countercurrent, and the principle is the same as above. The volatile gases generated by the heating reaction are absorbed by a spray absorption tower, including acidic gases generated by rare earth precipitation, to prevent the acidic gases from polluting the atmosphere.

[0033] S5, calcining the rare earth oxalate mixture at high temperature to obtain mixed rare earth oxides. In this step: the calcination temperature is 900-1000°C, and the calcination time is controlled to be 1-2 hours, so that the rare earth oxalate is completely converted into rare earth oxide, and the rare earth recovery rate is maximized, REO ≥ 92%, and the rare earth recovery rate is > 90%.

[0034] Furthermore, the step S2 further comprises: performing sedimentation treatment on the first wastewater:

[0035] Add lime milk solution to the first wastewater for defluorination precipitation, generate calcium fluoride precipitation, then add sodium metaphosphate and aluminum salt as precipitation flocculants, further defluorination precipitation, make fluoride ions react to precipitate fluoroaluminum phosphate, add 1% flocculant (mass volume ratio) to make the calcium fluoride precipitate settle better. After the precipitation is completely precipitated, adjust the pH value of the first wastewater to 6-9, so that the calcium fluoride is completely precipitated, and the solution is neutral, the first wastewater is clear, does not contain harmful substances, and meets the discharge standards.

[0036] Furthermore, the step S4 further comprises: neutralizing the second wastewater:

[0037] Lime milk solution is added to the second wastewater to react with oxalate ions to precipitate calcium oxalate. After precipitation, the pH value of the first wastewater is adjusted to 6-9, the solution is neutral, and the second wastewater is clear, does not contain harmful substances, and meets the emission standards.

[0038] The reaction principles and chemical reaction formulas of each step are as follows:

[0039] 1. Step S2-Alkali conversion process: In the present invention, the ionic rare earth acid slag has a fluorine content of about 0.1% to 1wt%. The ionic rare earth acid slag (acid slag) mainly contains mechanical impurities such as aluminum hydroxide, fluoride, calcium salt, heavy metal, silicate, barium salt, radioactive material, sand and gravel. Alkali reacts with rare earth fluoride and other fluoride (such as calcium fluoride, magnesium fluoride, etc.), and rare earth fluoride is mainly REF 3 It exists in the form of acid slag of rare earth concentrate, slurryed with water and then mixed evenly with sodium hydroxide solution. Under boiling conditions of 100-110°C, insoluble fluoride in the slag is converted into soluble sodium fluoride. At the same time, part of aluminum and silicon are converted into soluble metaaluminate and silicate. Then, it is filtered and washed, and the solid-liquid is separated. The rare earth and calcium, thorium, iron, etc. in the slag are left in the solid precipitate in the form of hydroxide, and part of aluminum, silicon, and fluoride ions are removed with the solution. The acid slag mixed with alkali at 100-110°C has the following reactions:

[0040]

[0041] The first wastewater treatment process (the first wastewater contains NaF, aluminum, silicon, fluoride ions, etc.):

[0042] The acid residue of ionic rare earth concentrate is mixed with sodium hydroxide solution, heated and alkali-converted, and then filtered and washed to produce sodium and fluoride-containing wastewater. At room temperature, lime milk solution is added to the wastewater to precipitate fluoride ions as calcium fluoride, and then sodium metaphosphate and aluminum salt are added as precipitation flocculants to further precipitate fluoride into fluoroaluminum phosphate. After adjusting the pH value to 6-9, it meets the discharge standards. The chemical reaction formula for fluorine precipitation is:

[0043] Ca(OH) 2 +2NaF=CaF 2 ↓+2NaOH; (4)

[0044] NaPO 3 +Al 3+ +3F － =NaPO 3 ·AlF 3 ↓; (5)

[0045] NaOH + HCl = NaCl + H 2 O; (6)

[0046] 2. Step S3-acid dissolution of alkali cake: After slurrying the alkali cake with water, mix it evenly with hydrochloric acid. Under heating conditions of 90-95°C, the rare earth hydroxide is converted into rare earth ions and enters the solution to separate from the undecomposed insoluble impurities. At the same time, Th(OH) is also dissolved. 4 、Fe(OH) 3 、Fe(OH) 2 、Al(OH) 3, Ca(OH) 2 , the chemical reaction is as follows:

[0047]

[0048] 3. Step S4-oxalic acid precipitation: Oxalic acid is used to react with the rare earth in the rare earth crude solution to generate insoluble oxalate precipitates, while impurities such as calcium and iron remain in the precipitation mother liquor, thereby achieving the purpose of separation. The chemical reaction is as follows:

[0049]

[0050] Second wastewater treatment process (the second wastewater contains RE 3+ , Fe 3+ , Ca 2+ 、Al 3+ , hydrochloric acid and oxalic acid, etc.):

[0051] The wastewater after oxalic acid precipitation of rare earth contains high acid (pH ≤ 1.5), mainly hydrochloric acid and oxalic acid. It is neutralized with waste alkali solution or lime emulsion. The wastewater after neutralization is clear, pH = 6-9, does not contain harmful substances, and meets the discharge standards. The reaction is as follows:

[0052] Ca(OH) 2 +2H + →CaCl 2 +2H 2 O; (14)

[0053] Ca(OH) 2 +H 2 C 2 O 4 →CaC 2 O 4 ↓+2H 2 O ; (15)

[0054] 2. Step S5- Calcination of Rare Earth Oxalate

[0055] Rare earth oxalate is burned at 900-1000℃ for 1-2h to transform into mixed rare earth oxides. During the burning process, rare earth oxalate decomposes to produce water vapor and carbon dioxide which is discharged. The chemical reaction is as follows:

[0056]

[0057] In the above steps, the treatment process of waste gas and waste residue is as follows:

[0058] Waste gas treatment: The waste gas generated by the acid slag of ionic rare earth concentrate and sodium hydroxide heating to alkali conversion and the waste gas generated by the acid dissolution of alkali cake and acid solution and the volatilization of oxalic acid precipitation are collected in an organized manner, absorbed and treated in a spray absorption tower, and then discharged into the air after meeting the standards.

[0059] Waste residue treatment: The reduced tailings after acid dissolution contain barium sulfate, insoluble precipitates, trace radioactive elements and other mechanical impurities. They are low-level radioactive solid waste. After being temporarily stored in a low-level radioactive residue warehouse (using ground anti-seepage and radiation protection treatment), they are handed over to units with low-level radioactive waste disposal qualifications for treatment.

[0060] Please refer to Figure 1 , a complete description of the process technology for recovering rare earths from acid slag of ionic rare earth concentrate is given:

[0061] First, at 6m 3 Alkali-resistant enamel reactor, add water to prepare acid slag slurry (mixed slurry) with a concentration of 500-1000g / L according to the weight ratio of ionic rare earth concentrate acid slag to water solid-liquid 1:1-2; add alkaline substance (sodium hydroxide solution) to the acid slag slurry, adjust the concentration of sodium hydroxide solution to 50-100g / L, mix the slurry, heat the reaction at an adjustable temperature of 100-110℃, and continue the alkali conversion for 1-2h; secondly, use 10m 2 After filtering with a belt vacuum filter or other filtering and washing device, wash 3 to 4 times with water at a solid-liquid weight ratio of 1:2 to 4; then, the filtrate (first wastewater) is sent to the environmental protection process for slaked lime precipitation treatment, and after the alkali conversion is completed, an alkali cake with soluble fluoride removed is obtained (corresponding to the filter cake on the left side of the hydrochloric acid in the figure). Add water at a solid-liquid weight ratio of 1:1 to 2 to prepare an alkali cake slurry with a concentration of 500 to 1000 g / L; at 15 m 3 Add a certain proportion of hydrochloric acid to the glass fiber reinforced plastic reaction tank and other devices, adjust the concentration of hydrochloric acid to 1-3 mol / L, mix the slurry, heat the reaction at 90-95℃, and the acid dissolution lasts for 1-2 hours; secondly, use 10m 2 After filtering with a belt vacuum filter or other filtering and washing device, wash 3 to 4 times with water at a solid-liquid weight ratio of 1:2 to 4; again, send the filter residue to the residue warehouse for temporary storage, and after the acid dissolution is completed, a rare earth acid-dissolved feed solution (rare earth crude product solution) containing partially soluble hydroxides is obtained. According to the molar ratio of oxalic acid content to rare earth content of partially soluble hydroxides in the rare earth acid-dissolved feed solution of 3 to 5:1, add water to prepare oxalic acid concentration of 100 to 200 g / L, and simmer at 15 m 3 The glass fiber reinforced plastic reaction tank and other devices are mixed with the above rare earth acid solution, heated to react at an adjustable temperature of 60-80°C, and the precipitation lasts for 1-2 hours; secondly, a 10m 2After filtering by belt vacuum filter and other filtering and washing devices, it is washed 3-4 times with water at a solid-liquid weight ratio of 1:2-4; again, the filtrate (second wastewater) is sent to the environmental protection process for slaked lime precipitation treatment, and after the precipitation is completed, an oxalate rare earth mixture is obtained. Finally, the oxalate rare earth mixture is calcined at 900-1000℃ to obtain a mixed rare earth oxide (REO≥92%), and the rare earth recovery rate is greater than 90%. The generated wastewater is treated with slaked lime and adjusted to a fluoride ion of ≤8mg / L and a pH of 6-9; compared with other treatment processes, the rare earth recovery rate is high, which reduces costs and reduces three wastes. Specific embodiments

[0063] Example 1

[0064] Acid slag of ionic rare earth concentrate containing rare earth (REO = 3.4%) (solid-liquid weight ratio of 1:2) → Mix with water for slurry → Add 50g / L sodium hydroxide (the ratio of solid slag to solid sodium hydroxide in the mixed slurry is 10:1) → Alkali conversion at 100℃ for 1h → Filter cake → Wash with tap water 3 times (solid-liquid weight ratio of 1:2) → Filter cake → Alkali cake (solid-liquid weight ratio of 1:2) → Mix with water for slurry → Add hydrochloric acid (1mol / L) (solid-liquid ratio of alkaline cake slurry to acid solution is 2:1.1) → Acid dissolution at 90℃ for 1h → Filter Cake filtration → 3 times of tap water washing (solid-liquid weight ratio 1:2) → rare earth crude solution → add oxalic acid solution (the molar ratio of oxalic acid content in oxalic acid solution to rare earth content in rare earth crude solution is 3:1) → 60℃ precipitation → filtration → 3 times of tap water washing (solid-liquid weight ratio 1:2) → filtration → rare earth oxalate (rare earth oxalate mixture) → 900℃ calcination → mixed rare earth oxide; filtrate (including the first wastewater and the second wastewater) → lime milk precipitation → adjust pH to 6~9 → the wastewater is clear, does not contain harmful substances, and meets the discharge standards.

[0065] After the above treatment process, the rare earth recovery rate is 91.58%.

[0066] Example 2

[0067] Acid slag of ionic rare earth concentrate containing rare earth (REO = 5.2%) (solid-liquid weight ratio 1:2) → Mix with water for slurry → Add 80g / L sodium hydroxide (the ratio of solid slag to solid sodium hydroxide in the mixed slurry is 6.3:1) → Alkali conversion at 103℃ for 1.5h → Filter cake filtration → 4 tap water washing (solid-liquid weight ratio 1:3) → Filter cake filtration → Alkali cake (solid-liquid weight ratio 1:1) → Mix with water for slurry → Add hydrochloric acid (2mol / L) (solid ratio of alkaline cake slurry to acid solution) Liquid ratio is 2:1.3) → 92℃ acid dissolution for 2h → filter cake filtration → 3 tap water washing (solid-liquid weight ratio is 1:4) → rare earth crude solution → add oxalic acid solution (the molar ratio of oxalic acid content to rare earth content is 4:1) → 70℃ precipitation → filtration → 4 tap water washing (solid-liquid weight ratio is 1:3) → filtration → rare earth oxalate → 950℃ calcination → mixed rare earth oxide; filtrate → lime milk precipitation → adjust pH to 6~9 → the wastewater is clear, does not contain harmful substances, and meets the discharge standards.

[0068] After the above treatment process, the rare earth recovery rate is 92.27%.

[0069] Example 3

[0070] Acid slag of ionic rare earth concentrate containing rare earth (REO = 6.0%) (solid-liquid weight ratio 1:1) → Mix with water for slurry → Add 100g / L sodium hydroxide (the ratio of solid slag to solid sodium hydroxide in the mixed slurry is 5:1) → Alkali conversion at 110℃ for 2h → Filter cake filtration → 3 times of tap water washing (solid-liquid weight ratio 1:4) → Filter cake filtration → Alkali cake (solid-liquid weight ratio 1:2) → Mix with water for slurry → Add hydrochloric acid (3mol / L) (solid-liquid ratio of alkaline cake slurry to acid solution 2:1.5) → 95℃ acid dissolution for 1h → filter cake filtration → 4 tap water washing (solid-liquid weight ratio 1:3) → rare earth crude solution → add oxalic acid solution (the molar ratio of oxalic acid content to rare earth content is 5:1) → 80℃ precipitation → filtration → 3 tap water washing (solid-liquid weight ratio 1:4) → filtration → rare earth oxalate → 1000℃ calcination → mixed rare earth oxide; filtrate → lime milk precipitation → readjust pH = 6~9 → wastewater is clear, does not contain harmful substances, and meets discharge standards.

[0071] After the above treatment process, the rare earth recovery rate is 93.31%.

[0072] Example 4

[0073] Acid slag of ionic rare earth concentrate containing rare earth (REO = 7.1%) (solid-liquid weight ratio 1:1) → Mix with water for slurry preparation → Add 60g / L sodium hydroxide (the ratio of solid slag to solid sodium hydroxide in the mixed slurry is 8.3:1) → Alkali conversion at 102℃ for 1.5h → Filter cake → Wash with tap water 3 times (solid-liquid weight ratio 1:2) → Filter cake → Alkali cake (solid-liquid weight ratio 1:2) → Mix with water for slurry preparation → Add hydrochloric acid (2mol / L) (solid ratio of alkaline cake slurry to acid solution) Liquid ratio is 2:1.2) → 93℃ acid dissolution for 2h → filter cake filtration → 3 tap water washes (solid-liquid weight ratio is 1:1) → rare earth crude solution → add oxalic acid solution (the molar ratio of oxalic acid content to rare earth content is 5:1) → 75℃ precipitation → filtration → 4 tap water washes (solid-liquid weight ratio is 1:2) → filtration → rare earth oxalate → 930℃ calcination → mixed rare earth oxide; filtrate → lime milk precipitation → adjust pH to 6~9 → the wastewater is clear, does not contain harmful substances, and meets the discharge standards.

[0074] After the above treatment process, the rare earth recovery rate is 90.44%.

[0075] Example 5

[0076] Acid slag of ionic rare earth concentrate containing rare earth (REO=8.0%) (solid-liquid weight ratio 1:2) → Mix with water for slurry → Add 90g / L sodium hydroxide (the ratio of solid slag to solid sodium hydroxide in the mixed slurry is 5.6:1) → Alkali conversion at 109℃ for 1h → Filter cake filtration → 3 times tap water washing (solid-liquid weight ratio 1:4) → Filter cake filtration → Alkali cake (solid-liquid weight ratio 1:2) → Mix with water for slurry → Add hydrochloric acid (3mol / L) (solid-liquid ratio of alkaline cake slurry to acid solution) ratio is 2:1.4) → acid dissolution at 94℃ for 1h → filter cake filtration → 4 tap water washing (solid-liquid weight ratio is 1:2) → rare earth crude solution → add oxalic acid solution (the molar ratio of oxalic acid content to rare earth content is 4:1) → 70℃ precipitation → filtration → 3 tap water washing (solid-liquid weight ratio is 1:3) → filtration → rare earth oxalate → 980℃ calcination → mixed rare earth oxide; filtrate → lime milk precipitation → adjust pH to 6~9 → the wastewater is clear, does not contain harmful substances, and meets the discharge standards.

[0077] After the above treatment process, the rare earth recovery rate is 94.57%.

[0078] Example 6

[0079] Acid slag of ionic rare earth concentrate containing rare earth (REO = 9.4%) (solid-liquid weight ratio 1:2) → Mix with water for slurry → Add 50g / L sodium hydroxide (the ratio of solid slag to solid sodium hydroxide in the mixed slurry is 10:1) → Alkali conversion at 100℃ for 2h → Filter cake filtration → 4 tap water washing (solid-liquid weight ratio 1:3) → Filter cake filtration → Alkali cake (solid-liquid weight ratio 1:1) → Mix with water for slurry → Add hydrochloric acid (2mol / L) (solid-liquid ratio of alkaline cake slurry to acid solution is 2:1.1)→90℃ acid dissolution for 1.5h→filter cake filtration→4 tap water washing (solid-liquid weight ratio 1:3)→rare earth crude solution→add oxalic acid solution (the molar ratio of oxalic acid content to rare earth content is 5:1)→80℃ precipitation→filtration→3 tap water washing (solid-liquid weight ratio 1:4)→filtration→rare earth oxalate→920℃ calcination→mixed rare earth oxide; filtrate→lime milk precipitation→adjust pH=6~9→wastewater is clear, does not contain harmful substances, and meets discharge standards.

[0080] After the above treatment process, the rare earth recovery rate is 90.09%.

[0081] Example 7

[0082] Acid slag of ionic rare earth concentrate containing rare earth (REO = 10.8%) (solid-liquid weight ratio 1:1) → Mix with water for slurry → Add 70g / L sodium hydroxide (the ratio of solid slag to solid sodium hydroxide in the mixed slurry is 7.1:1) → Alkali conversion at 104℃ for 1h → Filter cake → Wash with tap water 3 times (solid-liquid weight ratio 1:2) → Filter cake → Alkali cake (solid-liquid weight ratio 1:1) → Mix with water for slurry → Add hydrochloric acid (1mol / L) (solid ratio of alkaline cake slurry to acid solution) Liquid ratio is 2:1) → 95℃ acid dissolution for 2h → filter cake filtration → 3 tap water washings (solid-liquid weight ratio is 1:4) → rare earth crude solution → add oxalic acid solution (the molar ratio of oxalic acid content to rare earth content is 3:1) → 60℃ precipitation → filtration → 4 tap water washings (solid-liquid weight ratio is 1:2) → filtration → rare earth oxalate → 990℃ calcination → mixed rare earth oxides; filtrate → lime milk precipitation → readjustment pH = 6~9 → wastewater is clear, does not contain harmful substances, and meets discharge standards.

[0083] After the above treatment process, the rare earth recovery rate is 92.16%.

[0084] Example 8

[0085] Acid slag of ionic rare earth concentrate containing rare earth (REO = 14.6%) (solid-liquid weight ratio 1:2) → Mix with water for slurry → Add 100g / L sodium hydroxide (the ratio of solid slag to solid sodium hydroxide in the mixed slurry is 5:1) → Alkali conversion at 108℃ for 1.5h → Filter cake filtration → 4 tap water washing (solid-liquid weight ratio 1:3) → Filter cake filtration → Alkali cake (solid-liquid weight ratio 1:2) → Mix with water for slurry → Add hydrochloric acid (2mol / L) (solid-liquid ratio of alkaline cake slurry to acid solution) ratio is 2:1.2) → 94℃ acid dissolution for 1h → filter cake filtration → 4 tap water washing (solid-liquid weight ratio is 1:3) → rare earth crude solution → add oxalic acid solution (the molar ratio of oxalic acid content to rare earth content is 5:1) → 70℃ precipitation → filtration → 3 tap water washing (solid-liquid weight ratio is 1:3) → filtration → rare earth oxalate → 1000℃ calcination → mixed rare earth oxide; filtrate → lime milk precipitation → adjust pH to 6~9 → the wastewater is clear, does not contain harmful substances, and meets the discharge standards.

[0086] After the above treatment process, the rare earth recovery rate is 91.95%.

[0087] Comparative Example 1

[0088] Acid dissolution residue of ionic rare earth concentrate containing rare earth (REO=12.5%) → strong acid activation acid dissolution (solid-liquid weight ratio 1:1) → 3-stage countercurrent pickling + countercurrent water washing of filter residue → solid-liquid separation → oxalic acid (molar ratio of oxalic acid content to rare earth content is 5:1, 140g / L) precipitation of pickling filtrate → oxalate rare earth concentrate → 980℃ calcination → oxidation of rare earth concentrate.

[0089] After the above treatment process, the rare earth recovery rate is 88.64%.

[0090] The acid slag of the ionic rare earth concentrate containing rare earth (REO=11.7%) is mixed evenly with alkaline substances (sodium hydroxide or sodium carbonate or potassium hydroxide or potassium carbonate, etc.) (weight ratio 1:1) → high temperature roasting at 850°C → acid leaching with acid solution (solid-liquid weight ratio 1:1) → washing and filtering 3 times → extracting thorium and uranium from the filtrate → removing sulfate from the rare earth raffinate to recover rare earth metals. After the above treatment process, the rare earth recovery rate is 80.52%.

[0091] The present invention converts the ionic rare earth concentrate acid slag into alkali and then adds hydrochloric acid for acid dissolution treatment, and then precipitates the rare earth with oxalic acid, and obtains mixed oxides with less impurity content after burning, so as to recover rare earth elements to the maximum extent. The process technology is simple and the flow is short. Based on the above-mentioned ionic rare earth concentrate acid slag recovery rare earth process technology, the capacity of treating ionic rare earth concentrate acid slag 2000 tons / year can be achieved; the quality of the recovered rare earth product is mixed rare earth oxide ≥ 92%, and the rare earth (REO) content in the rare earth concentrate acid slag is reduced from 3-15% to < 1%; the rare earth recovery rate is > 90%, and the generated wastewater is treated with slaked lime and adjusted to fluorine ions ≤ 8mg / L, pH = 6-9; compared with other treatment methods, the rare earth recovery rate is high, energy consumption is reduced, and three wastes are reduced. In addition, the operation is stable and reliable, the cost is low (the cost of acid slag recovery of rare earth treatment is < 40,000 yuan / ton REO), the economic benefit is considerable, the process is safe and environmentally friendly, and the output and quality are guaranteed.

Claims

1. A rare earth recovery method for ionic rare earth acid slag, characterized in that: The following steps are involved: S1, adding water to the ionic rare earth concentrate acid slag to prepare a slurry to obtain a mixed slurry, wherein the solid-liquid weight ratio of the ionic rare earth concentrate acid slag to water is 1:1-2; S2, adding sodium hydroxide solution to the mixed slurry for alkali conversion, filtering and washing to obtain first wastewater and alkali cake, wherein the concentration of the sodium hydroxide solution is 50-100 g / L; S3, adding water to the alkali cake to prepare a slurry to obtain an alkali cake slurry, wherein the solid-liquid weight ratio of the alkali cake to water is 1:1-2, the alkali cake slurry is heated and acid-dissolved, the pH value is controlled to be 0.5-1.0, and the crude rare earth product solution is obtained after filtering and washing; S4, precipitating the crude rare earth product solution with an oxalic acid solution, filtering and washing with water to obtain a second wastewater and an oxalate rare earth mixture; S5, calcining the rare earth oxalate mixture at high temperature to obtain mixed rare earth oxides.

2. The method for recovering rare earth from ionic rare earth acid slag according to claim 1, characterized in that: The mass fraction of rare earth in the acid slag of the ionic rare earth concentrate is 3-15wt%.

3. The method for recovering rare earth from ionic rare earth acid slag according to claim 1, characterized in that: In the step S2, the mixed slurry is heated and alkali-converted in an alkali-resistant enamel reactor, and the alkali-conversion reaction temperature is controlled to be 100-110° C. and the alkali-conversion reaction time is 1-2 hours.

4. The method for recovering rare earth from ionic rare earth acid slag according to claim 1, characterized in that: The step S2 further comprises: performing a sedimentation treatment on the first wastewater: Add lime milk solution to the first wastewater for defluorination precipitation, then add sodium metaphosphate and aluminum salt for further defluorination precipitation, and after the precipitate is precipitated, adjust the pH value of the first wastewater to meet the standard before discharging.

5. The method for recovering rare earth from ionic rare earth acid slag according to claim 1, characterized in that: In the step S3, the acid dissolution includes: adding hydrochloric acid, controlling the acid dissolution heating temperature to 90-95° C., and controlling the stirring time to 1-2 hours.

6. The method for recovering rare earth from ionic rare earth acid slag according to claim 4, characterized in that: The pH value of the first wastewater is controlled to be 6-9.

7. The method for recovering rare earth from ionic rare earth acid slag according to claim 1, characterized in that: In the step S3, the alkali cake slurry is heated and acid-dissolved in a glass fiber reinforced plastic reaction tank.

8. The method for recovering rare earth from ionic rare earth acid slag according to claim 1, characterized in that: The content of oxalic acid substance in the oxalic acid solution is 100-200 g / L.

9. The method for recovering rare earth from ionic rare earth acid slag according to claim 1, characterized in that: The molar ratio of the oxalic acid substance in the oxalic acid solution to the rare earth substance in the crude rare earth solution is 3 to 5:

1.

10. The method for recovering rare earth from ionic rare earth acid slag according to claim 1, characterized in that: In the step S5, the burning temperature is 900-1000° C., and the burning time is controlled to be 1-2 hours.

Images