A method for co-producing nano calcium sulfate whiskers by using calcium-containing solid waste and high-acid wastewater

Abstract

A method for co-producing nano-calcium sulfate whiskers by using calcium-containing solid waste and high-acid wastewater belongs to the field of environmental protection, and the steps are as follows: The calcium-containing waste residue is ground into powder, mixed and stirred with arsenic-containing high-acid wastewater, and reacted at room temperature. After the reaction is completed, gypsum products and filtrate A are obtained; After adding calcium-containing waste residue to filtrate A and reacting completely, suction filtration is carried out to obtain the post-impurity liquid; An extractant is added to the post-impurity liquid, and after mixing evenly, it is left to age to obtain filtrate B and filter residue A; After the filter residue A is washed with the pre-washing liquid, it is vacuum dried to obtain nano-calcium sulfate whisker products and the post-washing liquid. The post-washing liquid and filtrate B can be returned through the regeneration process for reuse as an extractant or pre-washing liquid. The preparation method of the present invention is simple and fast. The calcium-containing solid waste is recycled, reducing the solid waste stockpile. The high-acid wastewater is treated by resource utilization, greatly reducing its acidity and hardness. Moreover, the prepared nano-scale calcium sulfate whiskers and gypsum products can be continuously utilized, realizing the reduction and resource utilization of waste residue and wastewater.

Description

Technical Field

[0001] The invention belongs to the field of environmental protection, and in particular relates to a method for co-producing nano calcium sulfate whiskers by utilizing calcium-containing solid waste and high-acid wastewater. Background Art

[0002] At present, high-acid wastewater generated by mining development and metal smelting is mostly treated by neutralization with calcium-containing waste slag. The neutralization process produces a large amount of neutralization slag. The main component of the neutralization slag is gypsum, which is mixed with metal hydroxides and calcium carbonate. The neutralization slag has problems such as low gypsum purity and high impurity content, resulting in its low quality and difficulty in reuse. Most of the neutralization slag is still treated by stockpiling, which not only takes up a lot of space, but also has the risk of secondary pollution.

[0003] Therefore, it is the goal of the majority of scientific and technological workers to make calcium-containing solid waste and arsenic-containing high-acid wastewater harmless, reduced in volume, and recycled. If the waste residues and wastewater can be turned into treasure and recycled while being treated, it will not only solve the increasingly severe environmental problems, but also greatly reduce production costs and improve economic benefits.

[0004] Patent CN114314927A discloses a method for co-treating arsenic-containing waste acid and iron-arsenic waste residue; the arsenic concentration in the arsenic-containing waste acid is greater than 4 g / L, and the pH value is less than 1; iron-arsenic waste residue is used instead of iron salt to treat the arsenic-containing waste acid; the arsenic in the arsenic-containing waste acid and the iron-arsenic waste residue is fixed in a stable scorodite precipitate; at room temperature, a calcium hydroxide solution is added to the arsenic-containing waste acid to carry out a precipitation reaction until the pH value of the arsenic-containing waste acid reaches 0.6, and solid-liquid separation is carried out to obtain gypsum (calcium sulfate precipitate) and an arsenic-containing solution; hydrogen peroxide is added to the arsenic-containing solution to carry out an oxidation reaction to obtain a solution containing pentavalent arsenic; the solution system containing pentavalent arsenic is heated to 80-95° C. under mechanical stirring conditions, and iron-arsenic waste residue slurry is added to carry out a co-precipitation reaction, followed by solid-liquid separation to obtain a mixed precipitate of scorodite and calcium sulfate and a filtrate; a sodium sulfide aqueous solution is added to the filtrate to adjust the pH value of the system to 7, and a precipitation reaction is carried out under mechanical stirring to obtain a heavy metal sulfide precipitate. The oxidant used in the invention is hydrogen peroxide, which has a relatively high cost, and the arsenic removal stage is not suitable for normal temperature test environment, and the waste residue and wastewater resource utilization are not achieved.

[0005] Patent CN104674333A discloses a method for preparing nano-scale calcium sulfate whiskers from anhydrite; after modifying and removing impurities from anhydrite using 98% sulfuric acid solution, calcium sulfate whiskers are obtained by autoclaving and crystallization under high temperature and high pressure conditions, and then the nano-calcium sulfate whiskers are obtained by drying at 600°C. The invention has high requirements on experimental conditions, and more impurities in the obtained whiskers are distributed on the surface of the whiskers. In the present invention, nano-calcium sulfate whiskers are obtained under normal pressure conditions during the coordinated treatment of wastewater and waste residue. The surface of the whiskers is smooth and free of impurities, and the hardness of the liquid after the whiskers are obtained is reduced.

[0006] Patent CN116657253A discloses a method for preparing hemihydrate calcium sulfate whisker brushes in an alcohol-water system; soluble calcium salts and soluble sulfates are respectively added to an alcohol-water solution, heated separately, and then the two solutions are mixed evenly. The mixed solution is kept warm and static, and after the reaction is completed, the product is quickly filtered and dried to obtain hemihydrate calcium sulfate whisker brushes. This invention is a method for synthesizing calcium sulfate whiskers from calcium salts and sulfates in an alcohol solution. This invention obtains calcium sulfate whiskers from the treated liquid during the co-treatment process of wastewater and waste residues, enabling the rational and efficient utilization of the treated liquid and realizing the resource utilization of wastewater and waste residues.

[0007] Starting from the reduction and resource utilization of waste residues and wastewater, this invention uses the combined treatment of calcium-containing waste residues and highly acidic wastewater to enable the secondary utilization of calcium-containing solid waste and highly acidic wastewater. At the same time, nano-calcium sulfate whiskers and gypsum products are prepared. The gypsum products can be applied in fields such as soil improvement, road construction, and filling of polymer materials. While obtaining nano-calcium sulfate whiskers, the hardness of the treated liquid is greatly reduced and can be recycled, achieving waste treatment with waste and turning waste into treasure. Summary of the Invention

[0008] Aiming at the deficiencies of the prior art, this invention obtains gypsum products and nano-calcium sulfate whisker products while treating arsenic-containing highly acidic wastewater from gold ore roasting products with calcium-containing waste residues. The hardness of the treated liquid is greatly reduced, and the reagents involved in the invention can be recycled in the process.

[0009] To achieve the above object, this invention is realized by adopting the following technical solutions:

[0010] A method for co-producing nano-calcium sulfate whiskers from calcium-containing solid waste and highly acidic wastewater, specifically including the following steps:

[0011] (1) Grind the calcium-containing waste residue to form calcium-containing waste residue powder;

[0012] (2) Mix and stir the calcium-containing waste residue powder obtained in step (1) with arsenic-containing highly acidic wastewater, react at room temperature, and consider the reaction completed when the pH value is stable to obtain gypsum products and filtrate A;

[0013] (3) In the filtrate A obtained in step (2), after adding calcium-containing waste residue and reacting completely, perform suction filtration to obtain impurities and purified liquid;

[0014] (4) Add an extractant to the purified liquid obtained in step (3), mix evenly and let it stand for aging to obtain filtrate B and filter residue A;

[0015] (5) Wash the filter residue A obtained in step (4) with pre-washing liquid and then vacuum dry to obtain nano-calcium sulfate whisker products and post-washing liquid.

[0016] Further, the washing solution in step (5) and the filtrate B in step (4) undergo a regeneration process. After evaporation and separation, a regenerated solution and an extractant vapor are obtained. The extractant vapor is dehumidified and then returned to step (4) as the extractant or to step (5) as the pre-washing solution for reuse.

[0017] Among them:

[0018] In the said step (1), the calcium oxide content in the calcium-containing waste residue is not less than 60%, and it is selected from one or more of carbide slag, acetylene purification waste residue, fly ash, white mud, green mud, and lime slag. When multiple calcium-containing waste residues are selected, the total amount is the same as that when one calcium-containing waste residue is selected, and the multiple calcium-containing waste residues are in any proportion; the particle size of the calcium-containing waste residue powder is not higher than 200 mesh.

[0019] In the said step (2), the arsenic-containing highly acidic wastewater is highly sulfuric acid wastewater with a pH ≤ 2, an arsenic content of 0.5 - 4000 mg / L, and a sulfate content of 5 - 100 g / L generated after the oxidative roasting of gold ore. After the reaction, the pH is 1.8 - 2.5.

[0020] In the said step (2), the solid-liquid ratio of the calcium-containing waste residue powder to the arsenic-containing highly acidic wastewater is (0.2 - 1) : 200 g / mL.

[0021] In the said step (3), the solid-liquid ratio of the calcium-containing waste residue to the filtrate A is (0.8 - 1.5) : 200 g / mL, and the pH of the slurry should be maintained between 8 and 10 after complete reaction.

[0022] In the said step (4), the extractant is one of anhydrous methanol, anhydrous ethanol, and anhydrous isopropanol. The volume of the extractant is 0.5 - 2.5 times that of the hot filtrate, and the aging time is 0 - 4 h.

[0023] In the said step (5), the pre-washing solution has the same composition and concentration as the extractant in step (4), and the volume of the pre-washing solution is 10% - 20% of the volume of the filtrate B.

[0024] In the said step (5), the prepared nano-calcium sulfate whiskers have a diameter of 0.02 - 0.1 μm, a whisker length of 0.6 - 2.3 μm, and a whisker aspect ratio of 10 - 45.

[0025] The evaporation temperature of the said regeneration process is 60 - 80°C.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] The present invention provides a method for jointly treating waste residue and waste water while preparing nano-calcium sulfate whiskers. The preparation method is simple and rapid, the calcium-containing solid waste is reused, the stacking of solid waste is reduced, the highly acidic waste water is treated after resource utilization, its acidity and hardness are greatly reduced, and the prepared nano-calcium sulfate whiskers and gypsum products can be further utilized, realizing the reduction and resource utilization of waste residue and waste water.

[0028] 1. Co-treat the calcium-containing waste residue and the arsenic-containing highly acidic waste water from the gold ore roasting product to achieve waste treatment with waste, prepare neutralized slag gypsum products and nano-calcium sulfate whiskers, and rationally utilize the calcium-containing waste residue and the arsenic-containing highly acidic waste water to turn waste into treasure;

[0029] 2. Realize the integrated process of co-treating the calcium-containing waste residue and the arsenic-containing highly acidic waste water and preparing nano-calcium sulfate whisker products;

[0030] 3. Produce soft water after preparing nano-calcium sulfate whiskers to realize the reuse of water resources. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 XRD spectrum of the gypsum product prepared in Example 3 of the present invention;

[0032] Figure 2 XRD spectrum of the nano-calcium sulfate whiskers prepared in Example 8 of the present invention;

[0033] Figure 3 Scanning electron microscope image of the nano-calcium sulfate whiskers prepared in Example 8 of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0034] To enable those skilled in the art to better understand the technical solutions of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings.

[0035] Example 1

[0036] A method for co-producing nano-calcium sulfate whiskers using calcium-containing solid waste and highly acidic waste water specifically includes the following steps:

[0037] (1) Grind the lime slag with a calcium oxide content of 60% to form calcium-containing waste residue powder with a particle size not higher than 200 mesh;

[0038] (2) Mix and stir the calcium-containing waste residue powder obtained in step (1) with arsenic-containing highly acidic waste water at a solid-liquid ratio of 0.2:200 g / mL, react at room temperature, and the pH is 1.8 after the reaction to obtain a gypsum product and filtrate A; among them, the arsenic-containing highly acidic waste water is highly sulfuric acid waste water with a pH = 0.9, an arsenic content of 2000 mg / L, and a sulfate content of 10.8 g / L generated after the oxidation roasting of gold ore;

[0039] (3) adding calcium-containing waste residue to the filtrate A obtained in step (2) at a solid-liquid ratio of 0.8:200 g / mL, wherein the pH of the slurry after complete reaction is 8.4, and filtering to obtain impurities and impurity-free liquid;

[0040] (4) adding an equal volume of anhydrous methanol solution to the impurity-removed liquid obtained in step (3), mixing evenly and then standing for 1 hour to obtain filtrate B and residue A;

[0041] (5) washing the filter residue A obtained in step (4) with anhydrous methanol solution, the volume of the anhydrous methanol solution being 10% of the volume of the filtrate B, and vacuum drying to obtain a nano calcium sulfate whisker product and a washing liquid, wherein the obtained nano calcium sulfate whisker has a diameter of 0.02 to 0.09 μm, a whisker length of 0.6 to 1.8 μm, and a whisker aspect ratio of 25 to 35.

[0042] Furthermore, the post-washing liquid in step (5) and the filtrate B in step (4) are subjected to a regeneration and dehumidification process, and evaporated and separated at 65° C. to obtain a regenerated liquid and an extractant vapor. The extractant vapor is dehumidified and returned to step (4) as an extractant or is reused as a pre-washing liquid in step (5).

[0043] Example 2

[0044] A method for co-producing nano calcium sulfate whiskers by using calcium-containing solid waste and high-acid wastewater, specifically comprising the following steps:

[0045] (1) mixing carbide slag, acetylene purification waste residue, fly ash, white mud, green mud and lime slag in any proportion to obtain calcium-containing waste residue with a calcium oxide content of 73%, and grinding the mixture to form calcium-containing waste residue powder with a particle size of not more than 200 meshes;

[0046] (2) mixing the calcium-containing waste residue powder obtained in step (1) with the arsenic-containing high-acid wastewater at a solid-liquid ratio of 1:200 g / mL, and reacting at room temperature. After the reaction, the pH is 2.39, and a gypsum product and a filtrate A are obtained; wherein the arsenic-containing high-acid wastewater is high-sulfuric acid wastewater with a pH of 0.9, an arsenic content of 2000 mg / L, and a sulfate content of 10.8 g / L generated after oxidative roasting of gold ore;

[0047] (3) adding calcium-containing waste residue to the filtrate A obtained in step (2) at a solid-liquid ratio of 1.5:200 g / mL, and the pH of the slurry after complete reaction is 9.86, and filtering to obtain impurities and impurity-free liquid;

[0048] (4) adding 0.5 times the volume of anhydrous methanol solution to the impurity-removed liquid obtained in step (3), mixing evenly and then standing for 1 hour to obtain filtrate B and residue A;

[0049] (5) Wash the filter residue A obtained in step (4) with an anhydrous methanol solution. The volume of the anhydrous methanol solution is 10% of the volume of filtrate B. Vacuum dry to obtain nano calcium sulfate whisker products and the post-washing solution. The diameter of the prepared nano calcium sulfate whiskers is 0.04 - 0.09 μm, the whisker length is 0.7 - 2 μm, and the aspect ratio of the whiskers is 25 - 30.

[0050] Further, the post-washing solution in step (5) and filtrate B in step (4) go through a regeneration and dehumidification process. Evaporate and separate at 60 °C to obtain the regenerated solution and the extractant vapor. After dehumidification, the extractant vapor returns to step (4) as the extractant or to step (5) as the pre-washing solution for reuse.

[0051] Example 3

[0052] A method for co-producing nano calcium sulfate whiskers using calcium-containing solid waste and high-acid wastewater, specifically including the following steps:

[0053] (1) Mix carbide slag, acetylene purification waste residue, and lime slag in any proportion to obtain a calcium-containing waste residue with a calcium oxide content of 78%. Grind it to form a calcium-containing waste residue powder with a particle size not higher than 200 mesh.

[0054] (2) Mix the calcium-containing waste residue powder obtained in step (1) with arsenic-containing high-acid wastewater at a solid-liquid ratio of 1:200 g / mL and stir. React at room temperature. After the reaction, the pH is 2.5 to obtain gypsum products and filtrate A. Among them, the arsenic-containing high-acid wastewater is high-sulfuric acid wastewater with a pH = 0.9, an arsenic content of 2000 mg / L, and a sulfate content of 10.8 g / L generated after the oxidation roasting of gold ore.

[0055] Among them, the full-element analysis of the prepared gypsum products is shown in Table 1, and the XRD pattern of the gypsum products is as Figure 1 shown, and the impurity content of this gypsum product is less than 4%.

[0056] Table 1 Full-element analysis of gypsum products

[0057]

[0058] (3) In the filtrate A obtained in step (2), add calcium-containing waste residue at a solid-liquid ratio of 1.5:200 g / mL. After complete reaction, the pH of the slurry is 9.97. Filter to obtain impurities and the post-impurity-removal solution.

[0059] (4) Add 2.5 times the volume of anhydrous methanol solution to the post-impurity-removal solution obtained in step (3). Mix evenly and let it stand for aging for 4 h to obtain filtrate B and filter residue A.

[0060] (5) Wash the filter residue A obtained in step (4) with an anhydrous methanol solution. The volume of the anhydrous methanol solution is 10% of the volume of filtrate B. Vacuum dry to obtain a nano-calcium sulfate whisker product and a post-wash solution. The prepared nano-calcium sulfate whiskers have a diameter of 0.08 - 0.1 μm, a whisker length of 1.5 - 2 μm, and a whisker aspect ratio of 10 - 25.

[0061] Further, the post-wash solution in step (5) and filtrate B in step (4) undergo a regeneration and dehumidification process. Evaporate and separate at 65°C to obtain a regenerated solution and an extractant vapor. After dehumidification, the extractant vapor is returned to step (4) as an extractant or to step (5) as a pre-wash solution for reuse.

[0062] Example 4

[0063] A method for co-producing nano-calcium sulfate whiskers using calcium-containing solid waste and high-acid wastewater, specifically including the following steps:

[0064] (1) Mix carbide slag, acetylene purification waste residue, and lime slag in any proportion to obtain a calcium-containing waste residue with a calcium oxide content of 67%. Grind it, and grind the lime slag to form a calcium-containing waste residue powder with a particle size not higher than 200 mesh.

[0065] (2) Mix the calcium-containing waste residue powder obtained in step (1) with arsenic-containing high-acid wastewater at a solid-liquid ratio of 0.2:200 g / mL and stir. React at room temperature. After the reaction, the pH is 2.18 to obtain a gypsum product and filtrate A. Among them, the arsenic-containing high-acid wastewater is high-sulfuric acid wastewater with a pH = 1.92, an arsenic content of 0.5 mg / L, and a sulfate content of 5 g / L generated after gold ore oxidative roasting.

[0066] (3) In the filtrate A obtained in step (2), add calcium-containing waste residue at a solid-liquid ratio of 1:200 g / mL. After complete reaction, the pH of the slurry is 8.07. Filter to obtain impurities and a post-impurity-removal solution.

[0067] (4) Add an anhydrous ethanol solution with a volume 0.5 times that of the post-impurity-removal solution obtained in step (3), mix evenly, and let it stand for aging for 1 h to obtain filtrate B and filter residue A.

[0068] (5) Wash the filter residue A obtained in step (4) with an anhydrous ethanol solution. The volume of the anhydrous ethanol solution is 10% of the volume of filtrate B. Vacuum dry to obtain a nano-calcium sulfate whisker product and a post-wash solution. The prepared nano-calcium sulfate whiskers have a diameter of 0.02 - 0.05 μm, a whisker length of 0.6 - 1.5 μm, and a whisker aspect ratio of 15 - 35.

[0069] Further, the washing solution in step (5) and the filtrate B in step (4) undergo a regeneration and dehumidification process. At 65°C, they are evaporated and separated to obtain a regenerated solution and extractant vapor. The extractant vapor is dehumidified and then returned to step (4) as the extractant or to step (5) as the pre-washing solution for reuse.

[0070] Example 5

[0071] A method for co-producing nano calcium sulfate whiskers from calcium-containing solid waste and high-acid wastewater specifically comprises the following steps:

[0072] (1) Mix carbide slag, fly ash, white mud, and lime slag in any proportion to obtain a calcium-containing waste residue with a calcium oxide content of 69%. Grind it to form a calcium-containing waste residue powder with a particle size not higher than 200 mesh.

[0073] (2) Mix the calcium-containing waste residue powder obtained in step (1) with arsenic-containing high-acid wastewater at a solid-liquid ratio of 1:200 g / mL, stir, and react at room temperature. After the reaction, the pH is 2.48 to obtain a gypsum product and filtrate A. Among them, the arsenic-containing high-acid wastewater is high-sulfuric acid wastewater with a pH of 0.6, an arsenic content of 4000 mg / L, and a sulfate content of 100 g / L generated after gold ore oxidative roasting.

[0074] (3) In the filtrate A obtained in step (2), add calcium-containing waste residue at a solid-liquid ratio of 1.5:200 g / mL. After complete reaction, the pH of the slurry is 9.89. Perform suction filtration to obtain impurities and post-impurity removal liquid.

[0075] (4) Add an equal volume of anhydrous isopropanol solution to the post-impurity removal liquid obtained in step (3), mix evenly, and let it stand for aging for 1 h to obtain filtrate B and filter residue A.

[0076] (5) Wash the filter residue A obtained in step (4) with anhydrous isopropanol solution. The volume of the anhydrous isopropanol solution is 20% of the volume of filtrate B. Perform vacuum drying to obtain nano calcium sulfate whisker products and washing solution. The diameter of the prepared nano calcium sulfate whiskers is 0.03 - 0.07 μm, the whisker length is 1.5 - 2.3 μm, and the whisker aspect ratio is 35 - 45.

[0077] Further, the washing solution in step (5) and the filtrate B in step (4) undergo a regeneration and dehumidification process. At 80°C, they are evaporated and separated to obtain a regenerated solution and extractant vapor. The extractant vapor is dehumidified and then returned to step (4) as the extractant or to step (5) as the pre-washing solution for reuse.

[0078] Example 6

[0079] A method for co-producing nano calcium sulfate whiskers from calcium-containing solid waste and high-acid wastewater specifically comprises the following steps:

[0080] (1) Grind the carbide slag with 61% calcium oxide content to form calcium-containing waste residue powder with a particle size not higher than 200 mesh;

[0081] (2) Mix and stir the calcium-containing waste residue powder obtained in step (1) with arsenic-containing high-acid wastewater at a solid-liquid ratio of 1:200 g / mL, and react at room temperature. After the reaction, the pH is 2.31 to obtain gypsum products and filtrate A; among them, the arsenic-containing high-acid wastewater is high-sulfuric acid wastewater with a pH = 0.6, arsenic content of 4000 mg / L, and sulfate content of 100 g / L generated after gold ore oxidation roasting;

[0082] (3) In the filtrate A obtained in step (2), add calcium-containing waste residue at a solid-liquid ratio of 1.5:200 g / mL. After complete reaction, the pH of the slurry is 9.59, and filter to obtain impurities and purified liquid;

[0083] (4) Add twice the volume of anhydrous isopropyl alcohol solution to the purified liquid obtained in step (3), mix evenly and let it stand for aging for 2 h to obtain filtrate B and filter residue A;

[0084] (5) Wash the filter residue A obtained in step (4) with anhydrous isopropyl alcohol solution. The volume of the anhydrous isopropyl alcohol solution is 20% of the volume of filtrate B, and vacuum dry to obtain nano-calcium sulfate whisker products and washed liquid. The diameter of the nano-calcium sulfate whiskers is 0.07 - 0.1 μm, the whisker length is 1.8 - 2.3 μm, and the whisker aspect ratio is 15 - 33.

[0085] Furthermore, the washed liquid in step (5) and the filtrate B in step (4) go through a regeneration and dehumidification process. Evaporate and separate at 80°C to obtain a regenerated liquid and an extractant vapor. The extractant vapor is dehumidified and returned to step (4) as an extractant or to step (5) as a pre-washing liquid for reuse.

[0086] Example 7

[0087] A method for co-producing nano-calcium sulfate whiskers using calcium-containing solid waste and high-acid wastewater, specifically including the following steps:

[0088] (1) Mix carbide slag, fly ash, white mud and green mud in any proportion to obtain calcium-containing waste residue with 72% calcium oxide content, and grind it to form calcium-containing waste residue powder with a particle size not higher than 200 mesh;

[0089] (2) Mix and stir the calcium-containing waste residue powder obtained in step (1) with arsenic-containing high-acid wastewater at a solid-liquid ratio of 1:200 g / mL, and react at room temperature. After the reaction, the pH is 2.5 to obtain gypsum products and filtrate A; among them, the arsenic-containing high-acid wastewater is high-sulfuric acid wastewater with a pH = 0.6, arsenic content of 2000 mg / L, and sulfate content of 20.7 g / L generated after gold ore oxidation roasting;

[0090] (3) In the filtrate A obtained in step (2), calcium-containing waste residue is added according to a solid-liquid ratio of 1.2:200 g / mL. After complete reaction, the pH of the slurry is 9.2, and impurities and post-impurity removal liquid are obtained by suction filtration;

[0091] (4) An equal volume of anhydrous isopropanol solution is added to the post-impurity removal liquid obtained in step (3). After mixing evenly, it is left to age for 2 h to obtain filtrate B and filter residue A;

[0092] (5) The filter residue A obtained in step (4) is washed with anhydrous isopropanol solution. The volume of the anhydrous isopropanol solution is 20% of the volume of filtrate B. After vacuum drying, nano-calcium sulfate whisker products and post-washing liquid are obtained. The diameter of the nano-calcium sulfate whiskers is 0.05 - 0.09 μm, the whisker length is 1.5 - 2.2 μm, and the aspect ratio of the whiskers is 19 - 33.

[0093] Furthermore, the post-washing liquid in step (5) and filtrate B in step (4) undergo a regeneration and dehumidification process. At 80 °C, evaporation separation is carried out to obtain a regenerated liquid and an extractant vapor. After dehumidification, the extractant vapor is returned to step (4) as an extractant or to step (5) as a pre-washing liquid for reuse.

[0094] Example 8

[0095] A method for co-producing nano-calcium sulfate whiskers using calcium-containing solid waste and high-acid wastewater specifically includes the following steps:

[0096] (1) Pulverize fly ash with a calcium oxide content of 67% to form calcium-containing waste residue powder with a particle size not higher than 200 mesh;

[0097] (2) Mix and stir the calcium-containing waste residue powder obtained in step (1) with arsenic-containing high-acid wastewater according to a solid-liquid ratio of 1:200 g / mL, and carry out the reaction at room temperature. After the reaction ends, the pH is 1.92 to obtain gypsum products and filtrate A; among them, the arsenic-containing high-acid wastewater is high-sulfuric acid wastewater with a pH = 0.6, an arsenic content of 2000 mg / L, and a sulfate content of 86 g / L generated after gold ore oxidative roasting;

[0098] (3) In the filtrate A obtained in step (2), calcium-containing waste residue is added according to a solid-liquid ratio of 1.5:200 g / mL. After complete reaction, the pH of the slurry is 8.59, and impurities and post-impurity removal liquid are obtained by suction filtration;

[0099] (4) An equal volume of anhydrous isopropanol solution is added to the post-impurity removal liquid obtained in step (3). After mixing evenly, suction filtration is immediately carried out to obtain filtrate B and filter residue A;

[0100] (5) Wash the filter residue A obtained in step (4) with an anhydrous isopropanol solution. The volume of the anhydrous methanol solution is 20% of the volume of filtrate B. Vacuum dry to obtain the nano-calcium sulfate whisker product and the post-wash solution. The XRD pattern of the prepared nano-calcium sulfate whiskers is as shown in Figure 2 shown, and the scanning electron microscope image is as shown in Figure 3 shown. Its diameter is 0.02 - 0.08 μm, the whisker length is 0.6 - 2.1 μm, and the aspect ratio of the whiskers is 30 - 45.

[0101] Furthermore, the post-wash solution in step (5) and filtrate B in step (4) undergo a regeneration and dehumidification process. Evaporation separation is carried out at 80°C to obtain the regenerated solution and the extractant vapor. After dehumidification, the extractant vapor is returned to step (4) as the extractant or to step (5) as the pre-wash solution for reuse.

Claims

1. A method for co-producing nano calcium sulfate whiskers by using calcium-containing solid waste and high-acid wastewater, characterized in that, Specifically, it includes the following steps: (1) Grind the calcium-containing waste residue to form calcium-containing waste residue powder; (2) Mix and stir the calcium-containing waste residue powder obtained in step (1) with the arsenic-rich acidic wastewater, react at room temperature, and consider the reaction ended when the pH value is stable, to obtain gypsum products and filtrate A; (3) In the filtrate A obtained in step (2), after adding the calcium-containing waste residue and reacting completely, perform suction filtration to obtain impurities and the liquid after impurity removal; (4) Add an extractant to the liquid after impurity removal obtained in step (3), mix evenly and then stand for aging to obtain filtrate B and filter residue A; (5) After washing the filter residue A obtained in step (4) with the liquid before washing, perform vacuum drying to obtain nano calcium sulfate whisker products and the liquid after washing; The solid-liquid ratio of the calcium-containing waste residue to the filtrate A is (0.8 - 1.5):200 g / mL, and the pH of the slurry should be maintained between 8 and 10 after complete reaction; The extractant is one of anhydrous methanol, anhydrous ethanol, and anhydrous isopropanol. The volume of the extractant is 0.5 - 2.5 times that of the hot filtrate, and the aging time is 0 - 1 h; The diameter of the nano calcium sulfate whisker is 0.02 - 0.1 μm, the whisker length is 0.6 - 2.3 μm, and the aspect ratio of the whisker is 10 - 45.

2. The method for co-producing nano calcium sulfate whiskers by using calcium-containing solid waste and high-acid wastewater according to claim 1, characterized in that, It also includes the following steps: The liquid after washing in step (5) and the filtrate B in step (4) go through a regeneration process, and after evaporation and separation, a regenerated liquid and extractant vapor are obtained. The extractant vapor is dehumidified and then returned to step (4) as the extractant or to step (5) as the liquid before washing for reuse.

3. A method for co-producing nano calcium sulfate whiskers by using calcium-containing solid waste and high-acid wastewater according to claim 1, characterized in that, In step (1), the calcium oxide content in the calcium-containing waste residue is not less than 60%, and it is selected from one or more of carbide slag, acetylene purification waste residue, fly ash, white mud, green mud, and lime slag. When multiple calcium-containing waste residues are selected, the total amount is the same as when one calcium-containing waste residue is selected, and the multiple calcium-containing waste residues are in any proportion; the particle size of the calcium-containing waste residue powder is not higher than 200 mesh.

4. A method for co-producing nano calcium sulfate whiskers by using calcium-containing solid waste and high-acid wastewater according to claim 1, characterized in that, In step (2), the arsenic-rich acidic wastewater is high-sulfuric acid wastewater with pH ≤ 2, arsenic content of 0.5 - 4000 mg / L, and sulfate content of 5 - 100 g / L generated after gold ore oxidation roasting. The pH after the reaction ends is 1.8 - 2.

5.

5. A method for co-producing nano-calcium sulfate whiskers by using calcium-containing solid waste and high-acid wastewater according to claim 1, characterized in that, In step (2), the solid-liquid ratio of the calcium-containing waste residue powder to the arsenic-rich acidic wastewater is (0.2 - 1):200 g / mL.

6. A method for co-producing nano calcium sulfate whiskers by using calcium-containing solid waste and high-acid wastewater according to claim 1, characterized in that, In step (5), the liquid before washing has the same composition and concentration as the extractant in step (4), and the volume of the liquid before washing is 10% - 20% of the volume of the filtrate B.

7. A method for co-producing nano calcium sulfate whiskers by using calcium-containing solid waste and high-acid wastewater according to claim 2, characterized in that, The evaporation temperature of the regeneration process is 60 - 80 °C.

Images