Recovery method of solid waste containing calcium sulfate, magnesium element and rare earth element

Abstract

The invention provides a method for recycling solid waste containing calcium sulfate, magnesium element and rare earth elements, which comprises the following steps: firstly, separating the magnesium element from the solid waste through carbonization, then separating the rare earth elements from carbonized slag by adopting a rare earth separating agent, and then separating calcium sulfate and calcium carbonate through a solid-solid separator; or the magnesium element and the rare earth element are separated from the solid waste through a rare earth separating agent and carbonization, then the magnesium element is separated from the solid waste through pyrolysis, and the calcium sulfate and the calcium carbonate are separated through a solid-solid separator. The method is low in cost, simple and easy to implement, high in magnesium yield and capable of efficiently and comprehensively recycling waste residues, and has industrial application value.

Description

Technical Field

[0001] The invention belongs to the technical field of solid waste treatment, and in particular relates to a method for recovering solid waste containing calcium sulfate, magnesium elements and rare earth elements. Background Art

[0002] As people pay more and more attention to the ecological environment, the need to treat the "three wastes" generated in the process of non-ferrous metal mining and smelting is becoming increasingly urgent. The new Law on the Prevention and Control of Environmental Pollution by Solid Waste in 2020 has put forward stricter requirements on corporate environmental protection standards.

[0003] Solid waste containing calcium sulfate, magnesium and rare earth elements is a type of solid waste generated during the production process. For example, white slag from rare earth smelting usually comes from the process of neutralizing magnesium sulfate wastewater generated during the rare earth smelting process with lime. It is a solid waste with calcium sulfate as the main component, and also contains valuable elements such as magnesium, calcium, and rare earths. The comprehensive resource utilization of this type of solid waste has always been an industry problem. There are problems such as large production volume and high and complex operating costs of the existing reported recycling and treatment processes. At present, only stockpiling treatment is done, which not only occupies land resources, but also causes waste of valuable elements and increases environmental pressure. Therefore, there is an urgent need for a simple and easy low-cost treatment method that can not only reduce the stockpile volume of slag, but also effectively recycle the valuable elements it contains, in order to effectively improve environmental pressure. Summary of the invention

[0004] In view of the above technical status, the present invention aims to provide a method for recycling solid waste containing calcium sulfate, magnesium and rare earth elements, which is simple and easy to implement and can achieve efficient separation and recycling of magnesium, calcium and rare earth elements.

[0005] A technical solution provided by the present invention is: a method for recycling solid waste containing calcium sulfate, magnesium and rare earth elements, comprising the following steps:

[0006] (1) mixing the solid waste with water to obtain a first slurry;

[0007] (2) introducing carbon dioxide gas into the first slurry for reaction, and performing solid-liquid separation after the reaction to obtain a carbonized liquid and a carbonized slag, wherein the carbonized liquid is a magnesium-containing solution;

[0008] (3) mixing the carbonized slag with water to obtain a second slurry; using a rare earth separator to make the rare earth elements in the second slurry enter the liquid phase, and then separating them with a solid-solid separator to obtain an upper slurry and a lower slurry;

[0009] (4) subjecting the sizing material to solid-liquid separation, wherein the obtained upper filter residue is mainly calcium carbonate, and the obtained upper filtrate is mainly a rare earth-containing feed liquid;

[0010] The lower slurry is subjected to solid-liquid separation, the obtained lower filter residue is mainly calcium sulfate, and the obtained lower filtrate is mainly a rare earth-containing feed liquid.

[0011] In the step (1), the source of the solid waste is not limited, and it can be white slag from rare earth smelting.

[0012] In the step (1), the mass ratio of the solid waste to water is preferably 1:(1-10), more preferably 1:(1-6).

[0013] In the step (1), preferably, the solid waste is pulped, crushed, sieved and then mixed with water, and the particle size of the sieved solid waste is preferably below -100 mesh.

[0014] In the step (2), the purity of the carbon dioxide gas is not limited, but is preferably higher than 20% by mass.

[0015] In the step (2), the magnesium in the solid waste is separated from the calcium and rare earth elements by carbonization. In order to further improve the separation effect, preferably, carbon dioxide gas is introduced to react until the pH is 6-9, and more preferably until the pH is 6.5-7.5.

[0016] In the step (2), preferably, the carbide slag mainly comprises calcium carbonate, calcium sulfate and rare earth elements;

[0017] In the step (2), preferably, the main component of the carbonized liquid is magnesium bicarbonate, which can generally be directly reused in the industrial production link, or it can be prepared into basic magnesium carbonate solid by pyrolysis and then reused. In the pyrolysis method, the pyrolysis temperature is preferably 50°C-90°C; it can be pyrolyzed at normal pressure or at reduced pressure. In order to reduce operating costs and equipment requirements, pyrolysis at normal pressure is preferred; the liquid phase obtained by pyrolysis is preferably incorporated into the first slurry in step (1) for repeated recovery.

[0018] In step (2), if the magnesium content in the carburized slag is detected to be higher than 2%, preferably, the carburized slag is incorporated into the first slurry in step (1), and carbonization is repeated through step (2) until the magnesium content is lower than 2%, so as to increase the recovery rate of the magnesium element.

[0019] In the step (3), the mass ratio of carbonized slag to water is preferably 1:(1-50).

[0020] In the step (3), the rare earth separator can be added after the carbide slag and water are mixed and slurried, or the rare earth separator can be added to the carbide slag and water simultaneously for slurrying.

[0021] In the step (3), after the rare earth separation agent is added, the reaction temperature is preferably 20° C.-100° C., and the reaction time is preferably 10 minutes-2 hours.

[0022] In the step (3), the rare earth separation agent is not limited and can be selected from one or more of dibasic and higher carboxylic acids and their salts, aminocarboxylic acid complexes and their salts. The dibasic and higher carboxylic acids are not limited and can be selected from one or more of citric acid, succinic acid, hydroxysuccinic acid, etc. The aminocarboxylic acid complex is not limited and can be selected from one or more of ethylenediaminetetraacetic acid, diethylenetriaminepentaacetic acid, nitrilotriacetic acid, cyclohexanetetraacetic acid, ethylene glycol diethyl ether diaminetetraacetic acid, etc.

[0023] In the step (3), the solid-solid separator is a device for physically separating particles of different densities and / or different particle sizes, and is preferably a hydrocyclone.

[0024] Preferably, in step (4), the upper filter residue can be directly reused in the production process (for example, it can be directly reused in the magnesium sulfate wastewater treatment process, etc.), or it can be dried and reused.

[0025] Preferably, in step (4), the upper filtrate can be combined with the second slurry in step (3) for repeated separation and recovery.

[0026] Preferably, in step (4), the lower filter residue can be used as a raw material for preparing calcium sulfate whiskers, or as a calcium fertilizer for soil improvement in saline-alkali land. When the lower filter residue is used as a raw material for preparing calcium sulfate whiskers, in order to prevent the influence of a small amount of calcium carbonate therein on the final product, the pH value can be adjusted to acidic with sulfuric acid in advance, preferably to 1-4, and then adjusted to 8-10, and then the calcium sulfate whiskers are prepared by hydrothermal method.

[0027] In the step (1), if the rare earth element content in the solid waste is less than 1%, the rare earth element may not be recovered. In this case, in the step (3), no rare earth separation agent may be added for reaction, and solid-solid separation may be performed directly.

[0028] Preferably, in step (3), after the rare earth ions in the second slurry are detected to reach a certain concentration (for example, 10 g / L or more), the rare earth elements can be first recovered by precipitation, and then the rare earth separation agent is used to make the remaining rare earth elements enter the liquid phase, and then separated by a solid-solid separator to obtain an upper slurry and a lower slurry. The reagent used in the precipitation method is preferably oxalic acid.

[0029] Another technical solution provided by the present invention is: a method for recycling solid waste containing calcium sulfate, magnesium and rare earth elements, comprising the following steps:

[0030] (A) mixing the solid waste with water to obtain a first slurry;

[0031] Using a rare earth separation agent to make the rare earth elements in the first slurry enter the liquid phase; then, introducing carbon dioxide gas to react, and after the reaction, performing solid-liquid separation to obtain carbonized liquid and carbonized slag;

[0032] The carbonized liquid mainly includes magnesium bicarbonate and rare earth elements; the carbonized slag mainly includes calcium carbonate and calcium sulfate;

[0033] (B) mixing the carbonized slag with water to obtain a second slurry, and then separating the slurry using a solid-solid separator to obtain an upper slurry and a lower slurry;

[0034] The upper slurry is subjected to solid-liquid separation to obtain an upper filter residue and an upper filtrate, wherein the upper filter residue is mainly calcium carbonate; the lower slurry is subjected to solid-liquid separation to obtain a lower filter residue and a lower filtrate, wherein the lower filter residue is mainly calcium sulfate;

[0035] The carbonized liquid is pyrolyzed by pyrolysis, and then solid-liquid separation is performed, and the obtained solid slag is mainly magnesium carbonate, and the filtrate mainly contains rare earth elements; preferably, the filtrate is incorporated into the first slurry in step (A) and repeatedly recovered.

[0036] Preferably, when the rare earth elements in the filtrate reach a certain concentration (for example, above 10 g / L), the rare earths can be first recovered by precipitation (the rare earth elements are precipitated), and then the liquid phase obtained by filtration is incorporated into the first slurry in step (A) for repeated recovery.

[0037] In the step (A), the source of the solid waste is not limited, and can be white slag from rare earth smelting.

[0038] In the step (A), the mass ratio of the solid waste to water is preferably 1:(1-10), more preferably 1:(1-6).

[0039] In the step (A), the solid waste is preferably pulped, crushed, sieved and then mixed with water, and the particle size of the sieved solid waste is preferably less than -100 mesh.

[0040] In the step (A), the solid waste and water may be mixed and slurried before adding the rare earth separation agent, or the rare earth separation agent may be simultaneously added to the solid waste and water for slurrying.

[0041] In the step (A), after the rare earth separation agent is added, the reaction temperature is preferably 20° C.-100° C., and the reaction time is preferably 10 minutes-2 hours.

[0042] In the step (A), the rare earth separation agent is not limited and can be selected from one or more of dibasic and higher carboxylic acids and their salts, aminocarboxylic complexes and their salts. The dibasic and higher carboxylic acids are not limited and can be selected from one or more of citric acid, succinic acid, hydroxysuccinic acid, etc. The aminocarboxylic complex is not limited and can be selected from one or more of ethylenediaminetetraacetic acid, diethylenetriaminepentaacetic acid, nitrilotriacetic acid, cyclohexanetetraacetic acid, ethylene glycol diethyl ether diaminetetraacetic acid, etc.

[0043] In the step (A), the purity of the carbon dioxide gas is not limited, but is preferably higher than 20% by mass.

[0044] In the step (A), preferably, carbon dioxide gas is introduced to react until the pH is 6-9, more preferably until the pH is 6.5-7.5.

[0045] In the step (A), when the magnesium content in the carbided slag is higher than 2%, preferably, the carbided slag is incorporated into the first slurry for repeated recovery until the magnesium content is lower than 2%, so as to increase the recovery rate of the magnesium element.

[0046] In the step (B), the mass ratio of the carbonized slag to water is preferably 1:(1-50).

[0047] In the step (B), in the pyrolysis method, the pyrolysis temperature is preferably 50°C-90°C. The pyrolysis can be performed at normal pressure or reduced pressure. In order to reduce operating costs and equipment requirements, pyrolysis at normal pressure is preferred.

[0048] In the step (B), the solid-solid separator is a device for physically separating particles of different densities and / or different particle sizes, and is preferably a hydrocyclone.

[0049] Preferably, in step (B), the upper filter residue can be directly reused in the production process, or can be dried and reused.

[0050] Preferably, in step (B), the upper filtrate can be combined with the second slurry for repeated separation and recovery.

[0051] Preferably, in step (B), the lower filter residue can be used as a raw material for preparing calcium sulfate whiskers, and can also be used as a calcium fertilizer for soil improvement in saline-alkali land. When the lower filter residue is used as a raw material for preparing calcium sulfate whiskers, in order to prevent the influence of a small amount of calcium carbonate present therein on the final product, the pH value can be adjusted to acidic with sulfuric acid in advance, preferably to 1-4, and then adjusted to 8-10, and then the calcium sulfate whiskers are prepared by hydrothermal method.

[0052] Compared with the prior art, the present invention has the following beneficial effects:

[0053] (1) The present invention uses carbon dioxide, the main culprit of greenhouse gases and an industrial by-product, as the main medium to achieve comprehensive recycling of solid waste containing calcium sulfate, magnesium and rare earth elements at ambient temperature, thereby reducing carbon emissions and achieving efficient separation of valuable elements such as calcium, magnesium and rare earth elements with a simple and easy process.

[0054] (2) A recovery method provided by the present invention first separates magnesium from the solid waste by carbonization, then separates rare earth elements from the carbonized slag using a rare earth separator, and then separates calcium sulfate and calcium carbonate using a solid-solid separator;

[0055] Another recovery method provided by the present invention first separates magnesium and rare earth elements from the solid waste by using a rare earth separator and carbonization, then separates magnesium from the solid waste by pyrolysis, and separates calcium sulfate and calcium carbonate by using a solid-solid separator;

[0056] Both methods are simple and easy.

[0057] (3) The present invention converts part of the low-value calcium sulfate into calcium carbonate through reaction and efficient separation processes, thus achieving high-value conversion and utilization of calcium element to a certain extent.

[0058] (4) The present invention has the advantages of low recovery cost, easy operation and high separation efficiency, especially the magnesium yield is greater than 80%, the solid slag content is reduced by more than 60% after treatment, and the main component of the solid slag is calcium sulfate. The whole process not only achieves the purpose of reducing the slag amount and harm of solid waste containing calcium sulfate, magnesium and rare earth elements, solves the problems of land occupation and environmental pollution, but also realizes the full resource utilization of various valuable elements, and has the value of large-scale application.

[0059] (5) The water used in the present invention can be recycled in the entire process, and almost no wastewater is discharged, thus avoiding environmental pollution.

[0060] (6) The solid waste containing calcium sulfate, magnesium and rare earth elements of the present invention can be rare earth smelting white slag, thereby realizing the comprehensive recycling and utilization of rare earth smelting white slag. BRIEF DESCRIPTION OF THE DRAWINGS

[0061] Figure 1 This is a flow chart of the comprehensive recovery and treatment of white slag from rare earth smelting in Example 1.

[0062] Figure 2 This is a flow chart of the comprehensive recovery and treatment of rare earth smelting white slag in Example 3.

[0063] Figure 3 is an optical microscope image of the calcium sulfate whisker prepared in Example 2.

[0064] Figure 41 is a scanning electron microscope image of the calcium sulfate whisker prepared in Example 2.

[0065] Figure 5 It is the XRD spectrum of the calcium sulfate whisker prepared in Example 2.

[0066] Figure 6 This is the curve showing the change in magnesium yield in the carbonized liquid at different solid-to-liquid ratios in Example 4.

[0067] Figure 7 This is the change curve of magnesium yield in the carbonization liquid at different termination pH in Example 4. DETAILED DESCRIPTION

[0068] The present invention is further described in detail below in conjunction with the embodiments and drawings. It should be pointed out that the embodiments described below are intended to facilitate the understanding of the present invention and do not have any limiting effect on the present invention.

[0069] Embodiment 1:

[0070] The composition analysis results of rare earth smelting white slag provided by a certain enterprise are shown in Table 1. The magnesium, calcium and rare earth elements in the rare earth smelting white slag are recycled and reused as follows:

[0071] (1) Carburization separation of magnesium

[0072] 100 g of rare earth smelting white slag was ground and sieved with a 100-mesh sample sieve. The sieved rare earth smelting white slag was charged into a series carbonization tower, and water was added to slurry according to the mass ratio of rare earth smelting white slag to water (rare earth smelting white slag: water = 1:10) to obtain a first slurry.

[0073] Carbon dioxide was introduced into the first slurry, and the reaction was carried out at 20°C until the pH value was 6.95. After the reaction was completed, the slurry was filtered and washed three times with water to obtain 1L of carbonized liquid and 63g of carbonized slag. The component analysis results of the carbonized liquid and the carbonized slag are shown in Table 2. According to the magnesium content in the carbonized slag, the recovery rate of magnesium in the rare earth smelting white slag was as high as 88.97%. The carbonized liquid is a magnesium-containing solution, which is directly incorporated into the transformation process.

[0074] (2) Separation of calcium carbonate and calcium sulfate

[0075] 60g of carbide slag and water were mixed and slurried at a mass ratio of carbide slag: water = 1:10 to obtain a second slurry. Calcium ethylenediaminetetraacetate was added to the second slurry at a mass ratio of (lanthanum + cerium): calcium ethylenediaminetetraacetate = 1:9, and stirred at 90°C for 2 hours; after the reaction was completed, it was cooled to room temperature and pumped into a multi-stage hydrocyclone for solid-solid separation to obtain an upper slurry flowing out of the upper part of the cyclone and a lower slurry flowing out of the bottom.

[0076] The upper slurry was centrifuged to obtain 26g of solid calcium carbonate (see Table 3). The calcium carbonate can be directly reused in the magnesium sulfate wastewater treatment process. The lower slurry was filtered and separated to obtain about 33g of solid calcium sulfate. The solid calcium sulfate can be used as a soil conditioner.

[0077] The upper filtrate and the lower filtrate obtained by separation of the upper slurry and the lower slurry are combined and returned to the carbonized slag beating process in step (2) for recycling.

[0078] (3) Separation of rare earth

[0079] When the accumulation of rare earth ions is detected to be above 10 g / L during the recycling of the upper filtrate and the lower filtrate, the filtrate is transferred to a reactor, heated to 80°C, and rare earth is precipitated with saturated oxalic acid. The pH value of the solution obtained by precipitating rare earth is adjusted to 1, and ethylenediaminetetraacetic acid is recovered. The ethylenediaminetetraacetic acid is reacted with lime water to produce calcium ethylenediaminetetraacetate for reuse. The recovered solution is adjusted to a pH value of 6-7 with lime water, filtered, and returned to step (2) of the carbonized slag pulping process.

[0080] Table 1. Element analysis results of rare earth smelting white slag

[0081]

[0082] Table 2. Carbonization analysis results

[0083]

[0084] Table 3. Solid-solid separation efficiency of calcium carbonate and calcium sulfate in carbonized slag

[0085]

[0086] Embodiment 2:

[0087] The component analysis results of the rare earth smelting white slag are shown in Table 4, wherein the rare earth content is less than 1%, and there is no recovery value. The magnesium and calcium elements in the rare earth smelting white slag are recovered and reused as follows:

[0088] (1) Carburization separation of magnesium

[0089] The rare earth smelting white slag is ground and sieved with a 100-mesh sample sieve, and the sieved rare earth smelting white slag is charged into a series carbonization tower, and water is added to slurry according to the mass ratio of rare earth smelting white slag to water (rare earth smelting white slag: water = 1:10) to obtain a first slurry.

[0090] Carbon dioxide was introduced into the first slurry, and the reaction was carried out at 15°C until the pH value was 6.88; after the reaction was completed, the slurry was filtered and washed with water three times to obtain carbonized liquid and carbonized slag. The component analysis results of the carbonized liquid and the carbonized slag are shown in Table 5. The carbonized liquid is a magnesium-containing solution, which is directly incorporated into the transformation process.

[0091] (2) Separation of calcium carbonate and calcium sulfate

[0092] The carbonized slag and water are mixed and slurried in a mass ratio of carbonized slag: water = 1:20 to obtain a second slurry. The second slurry is pumped into a multi-stage hydrocyclone for solid-solid separation to obtain an upper slurry flowing out of the upper part of the cyclone and a lower slurry flowing out of the bottom.

[0093] The upper slurry is centrifuged to obtain solid calcium carbonate. The calcium carbonate can be directly reused in the magnesium sulfate wastewater treatment process. The lower slurry is filtered and separated to obtain solid calcium sulfate. The upper filtrate and the lower filtrate obtained by separating the upper slurry and the lower slurry are combined and returned to the carbonized slag pulping process in step (2) for recycling.

[0094] (3) Preparation of calcium sulfate whiskers

[0095] The calcium sulfate solid separated from the lower slurry was adjusted to pH 2.20 with 0.1 mol / L sulfuric acid, filtered, and the filter residue was prepared into slurry with water at a mass ratio of filter residue: water = 1:20, the pH value was adjusted to 9.10, and a hydrothermal reaction was carried out at 120° C. for 180 min. The calcium sulfate whiskers were obtained after natural cooling and filtration.

[0096] The optical microscope of the calcium sulfate whiskers Figure 3 As shown in the scanning electron microscope Figure 4 As shown, the obtained calcium sulfate whiskers have a complete appearance, a perfect structure, a diameter of about 1-2um, good uniformity, and an aspect ratio close to 100, which meets the requirements of subsequent industrial applications, indicating that this treatment method has no obvious side effects on the preparation of calcium sulfate whiskers. Figure 5 As shown, the obtained calcium sulfate whiskers are calcium sulfate dihydrate with high crystallinity, and no obvious impurity phase peak is observed, which is consistent with the results of scanning electron microscopy and optical microscopy observations.

[0097] Table 4. Element analysis results of rare earth smelting white slag

[0098]

[0099] Table 5. Carbonization analysis results

[0100]

[0101] Embodiment 3:

[0102] The rare earth smelting white slag is the same as in Example 1. The magnesium element, calcium element and rare earth element in the rare earth smelting white slag are recycled and reused as follows:

[0103] (1) Carburization separation of magnesium

[0104] The rare earth smelting white slag is ground and sieved with a 100-mesh sample sieve, and the sieved rare earth smelting white slag is charged into a series carbonization tower, and water is added to slurry according to the mass ratio of rare earth smelting white slag to water (rare earth smelting white slag: water = 1:6) to obtain a first slurry.

[0105] Add calcium ethylenediaminetetraacetate in the first slurry at a mass ratio of (lanthanum + cerium): calcium ethylenediaminetetraacetate = 1:10, stir and react at 95°C for 2 hours; then cool to room temperature, introduce carbon dioxide, react at room temperature until the pH value is 7.01; filter after the reaction is completed, wash three times with water to obtain carbonized liquid and carbonized slag. The carbonized liquid is transferred to a pyrolysis kettle, pyrolyzed at 90°C and normal pressure for 2 hours, cooled naturally, filtered to obtain basic magnesium carbonate solid, and the liquid phase obtained by pyrolysis is incorporated into the rare earth smelting white slag pulping process, that is, incorporated into the first slurry.

[0106] (2) Separation of calcium carbonate and calcium sulfate

[0107] The carbonized slag and water are mixed and slurried in a mass ratio of carbonized slag: water = 1:20 to obtain a second slurry. The second slurry is pumped into a multi-stage hydrocyclone for solid-solid separation to obtain an upper slurry flowing out of the upper part of the cyclone and a lower slurry flowing out of the bottom. The upper slurry is centrifuged to obtain solid calcium carbonate. Calcium carbonate can be used to calcine calcium oxide. The lower slurry is filtered and separated to obtain solid calcium sulfate. The upper filtrate and the lower filtrate obtained by separating the upper slurry and the lower slurry are combined and returned to the carbonized slag slurrying process, that is, incorporated into the second slurry for recycling.

[0108] (3) Separation of rare earth

[0109] When rare earth ions are detected to accumulate to more than 10g / L during the recycling of carbonized liquid, it is transferred to a reactor, heated to 80°C, and precipitated with saturated oxalic acid. The precipitate is washed with 2% nitric acid and pure water, filtered and dried, and burned at 800°C to form rare earth oxides. The pH value of the mother liquor obtained by precipitating rare earth is then adjusted to 1, and ethylenediaminetetraacetic acid is recovered. EDTA reacts with lime water to form EDTA calcium for reuse. The recovered solution is adjusted to a pH value of 6-8 with lime water, filtered, and returned to the rare earth smelting white slag pulping process.

[0110] Table 6. Carbonization analysis results

[0111]

[0112] Table 7. Solid-solid separation efficiency of calcium carbonate and calcium sulfate in carbonized slag

[0113]

[0114] Embodiment 4:

[0115] The rare earth smelting white slag is the same as in Example 2. The magnesium and calcium elements in the rare earth smelting white slag are recycled and reused, and the specific method is basically the same as in Example 2, except that the step (1) is as follows:

[0116] (1) Control the mass ratio of rare earth smelting white slag to water (i.e. Figure 6 The solid-to-liquid ratio in the mixture is adjusted to obtain a first slurry.

[0117] Carbon dioxide is introduced into the first slurry, and the reaction is carried out at 15°C until the pH value is 6.88; after the reaction is completed, the slurry is filtered and washed with water three times to obtain a carbonized liquid and a carbonized slag, wherein the carbonized liquid is a magnesium-containing solution, and the magnesium yield is as follows: Figure 6 As shown, it is shown that the magnesium yield increases with the increase of water content in the first slurry.

[0118] Embodiment 5:

[0119] The rare earth smelting white slag is the same as in Example 2. The magnesium and calcium elements in the rare earth smelting white slag are recycled and reused, and the specific method is basically the same as in Example 2, except that the step (1) is as follows:

[0120] (1) According to the mass ratio of rare earth smelting white slag to water (i.e. Figure 6 Solid-liquid ratio in the mixture) Rare earth smelting white slag: water = 1:10 Add water for slurrying to obtain the first slurry.

[0121] Carbon dioxide is introduced into the first slurry, reacted at 15°C and the pH value is controlled; after the reaction is completed, the slurry is filtered and washed with water three times to obtain a carbonized liquid and a carbonized slag, wherein the carbonized liquid is a magnesium-containing solution, and the magnesium yield is as follows: Figure 7 As shown, it is shown that the magnesium yield decreases with increasing pH.

[0122] The embodiments described above provide a detailed description of the technical solutions of the present invention. It should be understood that the above are only specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, supplements or similar substitutions made within the scope of the principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for recovering solid waste containing calcium sulfate, magnesium and rare earth elements, characterized in that: The steps include: (1) mixing the solid waste with water to obtain a first slurry; (2) introducing carbon dioxide gas into the first slurry for reaction, and performing solid-liquid separation after the reaction to obtain a carbonized liquid and a carbonized slag; the carbonized liquid is a magnesium-containing solution; (3) mixing the carbonized slag with water to obtain a second slurry; Using a rare earth separator to make the rare earth elements in the second slurry enter the liquid phase, and then using a solid-solid separator to separate them to obtain an upper slurry and a lower slurry; (4) subjecting the sizing material to solid-liquid separation, wherein the obtained upper filter residue is mainly calcium carbonate, and the obtained upper filtrate is mainly a rare earth-containing feed liquid; The lower slurry is subjected to solid-liquid separation, the obtained lower filter residue is mainly calcium sulfate, and the obtained lower filtrate is mainly a rare earth-containing feed liquid.

2. The recycling method according to claim 1, characterized in that: In the step (1), the solid waste is white slag from rare earth smelting.

3. The recycling method according to claim 1, characterized in that: In the step (1), the mass ratio of the solid waste to water is 1:(1-10), preferably 1:(1-6); Preferably, in the step (1), the solid waste is pulped, crushed, sieved and then mixed with water, and the particle size of the sieved solid waste is preferably below -100 mesh.

4. The recycling method according to claim 1, characterized in that: In the step (2), the purity of the carbon dioxide gas is higher than 20%; Preferably, in step (2), carbon dioxide gas is introduced to react until the pH is 6-9, more preferably until the pH is 6.5-7.5; Preferably, in step (2), the carbide slag mainly comprises calcium carbonate, calcium sulfate and rare earth elements; Preferably, in step (2), the main component of the carbonized liquid is magnesium bicarbonate, and the carbonized liquid is used directly, or is prepared into basic magnesium carbonate solid by pyrolysis; Preferably, in the pyrolysis method, the pyrolysis temperature is 50°C-90°C; Preferably, the liquid phase obtained by pyrolysis in the pyrolysis method is incorporated into the first slurry in step (1) and is repeatedly recovered; Preferably, in step (2), when the magnesium content in the carburized slag is higher than 2%, the carburized slag is incorporated into the first slurry in step (1), and carbonization is repeated through step (2) until the magnesium content is lower than 2%.

5. The recycling method according to claim 1, characterized in that: In the step (3), the mass ratio of the carbonized slag to water is 1:(1-50); Preferably, in the step (3), the carbide slag and water are mixed and slurried, and then a rare earth separation agent is added, or the rare earth separation agent is simultaneously added to the carbide slag and water for slurrying; Preferably, in step (3), the reaction temperature after the rare earth separation agent is added is 20°C-100°C; Preferably, in step (3), the reaction time after the rare earth separation agent is added is 10 minutes to 2 hours; Preferably, in step (3), the rare earth separation agent is selected from one or more of divalent or higher carboxylic acids and their salts, aminocarboxylic acid complexes and their salts; Preferably, the dibasic or higher carboxylic acid is selected from one or more of citric acid, succinic acid, hydroxysuccinic acid, etc.; Preferably, the aminocarboxyl type complex is selected from one or more of ethylenediaminetetraacetic acid, diethylenetriaminepentaacetic acid, nitrilotriacetic acid, cyclohexanetetraacetic acid, and ethylene glycol diethyl ether diaminetetraacetic acid; Preferably, in step (3), the solid-solid separator is a hydrocyclone.

6. The recycling method according to claim 1, characterized in that: In the step (4), the upper filtrate is combined with the second slurry in step (3) for repeated separation and recovery; Preferably, in step (4), the lower filtrate is combined with the second slurry in step (3) for repeated separation and recovery; Preferably, in step (4), the lower filter residue is used as a raw material for preparing calcium sulfate whiskers, or as a calcium fertilizer for soil improvement in saline-alkali land; Preferably, in step (4), when the lower filter residue is used as a raw material for preparing calcium sulfate whiskers, the pH value is adjusted to acidic with sulfuric acid in advance, preferably to 1-4, and then the pH value is adjusted to 8-10, and then the calcium sulfate whiskers are prepared by a hydrothermal method.

7. The recycling method according to claim 1, characterized in that: In the step (1), if the rare earth content in the solid waste is less than 1%, no rare earth separation agent is added in the step (3), and solid-solid separation is directly performed; Preferably, in step (3), after the rare earth ions in the second slurry reach a certain concentration, the rare earth is first recovered by precipitation method, and then the rare earth separator is used to make the remaining rare earth elements enter the liquid phase, and then separated by a solid-solid separator to obtain an upper slurry and a lower slurry.

8. A method for recovering solid waste containing calcium sulfate, magnesium and rare earth elements, characterized in that: The steps include: (A) mixing the solid waste with water to obtain a first slurry; Using a rare earth separation agent to make the rare earth elements in the first slurry enter the liquid phase; then, introducing carbon dioxide gas to react, and after the reaction, performing solid-liquid separation to obtain carbonized liquid and carbonized slag; The carbonized liquid mainly includes magnesium bicarbonate and rare earth elements; the carbonized slag mainly includes calcium carbonate and calcium sulfate; (B) mixing the carbonized slag with water to obtain a second slurry, and then separating the slurry using a solid-solid separator to obtain an upper slurry and a lower slurry; The upper slurry is subjected to solid-liquid separation to obtain an upper filter residue and an upper filtrate, wherein the upper filter residue is mainly calcium carbonate; the lower slurry is subjected to solid-liquid separation to obtain a lower filter residue and a lower filtrate, wherein the lower filter residue is mainly calcium sulfate; The carbonized liquid is pyrolyzed by a pyrolysis method, and then solid-liquid separation is performed, and the obtained solid slag is mainly magnesium carbonate, and the filtrate mainly contains rare earth elements.

9. The recycling method as claimed in claim 8, characterized in that: In the step (A), the solid waste is white slag from rare earth smelting.

10. The recycling method according to claim 8, characterized in that: In the step (A), when the rare earth elements in the filtrate are detected to reach a certain concentration, the rare earth elements are firstly recovered by precipitation method, and then the liquid phase obtained by filtration is incorporated into the first slurry in the step (A) for repeated recovery.

11. The recycling method according to claim 8, characterized in that: In the step (A), the mass ratio of the solid waste to water is 1:(1-10), preferably 1:(1-6); Preferably, in the step (A), the solid waste is pulped, crushed, sieved and then mixed with water, and the particle size of the sieved solid waste is preferably less than -100 mesh; Preferably, in the step (A), the solid waste and water are mixed and slurried and then a rare earth separation agent is added, or the rare earth separation agent is simultaneously added to the solid waste and water for slurrying; Preferably, in the step (A), the reaction temperature after the rare earth separation agent is added is 20°C-100°C; Preferably, in the step (A), the reaction time after the rare earth separation agent is added is 10 minutes to 2 hours; Preferably, in step (A), the rare earth separation agent is selected from one or more of divalent and higher carboxylic acids and their salts, aminocarboxylic acid complexes and their salts; Preferably, the dibasic or higher carboxylic acid is selected from one or more of citric acid, succinic acid, hydroxysuccinic acid, etc.; Preferably, the aminocarboxyl type complex is selected from one or more of ethylenediaminetetraacetic acid, diethylenetriaminepentaacetic acid, nitrilotriacetic acid, cyclohexanetetraacetic acid, ethylene glycol diethyl ether diaminetetraacetic acid and the like.

12. The recycling method according to claim 8, characterized in that: In the step (A), the purity of the carbon dioxide is higher than 20%; Preferably, in step (A), carbon dioxide gas is introduced to react until the pH is 6-9, more preferably until the pH is 6.5-7.5; Preferably, in the step (A), when the magnesium content in the carbided slag is higher than 2%, the carbided slag is incorporated into the first slurry for repeated recovery until the magnesium content is lower than 2%.

13. The recycling method according to claim 8, characterized in that: In the step (B), the mass ratio of the carbonized slag to water is 1:(1-50); Preferably, in the step (B), the pyrolysis temperature in the pyrolysis method is 50°C-90°C; Preferably, in step (B), the solid-solid separator is a hydrocyclone; Preferably, in the step (B), the upper filtrate is combined with the second slurry for repeated separation and recovery; Preferably, in step (B), the lower filter residue is used as a raw material for preparing calcium sulfate whiskers, or The latter can be used as calcium fertilizer for soil improvement in saline-alkali land; Preferably, in the step (B), the filtrate is incorporated into the first slurry in the step (A) for repeated recovery; Preferably, in step (B), when the lower filter residue is used as a raw material for preparing calcium sulfate whiskers, the pH value is adjusted to acidic with sulfuric acid in advance, preferably to 1-4, and then the pH value is adjusted to 8-10, and then the calcium sulfate whiskers are prepared by hydrothermal method.

Images