Method for preparing calcium hydroxide from solid waste

Abstract

The invention discloses a method for preparing calcium hydroxide from solid waste, and relates to the technical field of calcium hydroxide preparation, industrial solid waste ardealite is firstly deacidified by limestone, then heavy metals and other impurities are removed by modified zeolite, then calcium oxide is obtained by calcination, and finally calcium hydroxide is prepared by digestion reaction of calcium oxide and water. According to the method, after acid removal, the modified zeolite is used, impurities such as acid and heavy metal in the ardealite solid waste are effectively removed through complexation and magnetic adsorption, the problem of difficult separation is solved, calcium oxide with high purity is obtained through calcination, and calcium hydroxide with high purity is obtained after the calcium oxide and water are subjected to a digestion reaction. The preparation method provided by the invention recycles calcium in solid wastes, and has strong environmental protection property and economic value.

Description

Technical Field

[0001] This invention relates to the field of calcium hydroxide preparation technology, and more specifically to a method for preparing calcium hydroxide from solid waste. Background Technology

[0002] Solid waste generated from industrial production contains a significant amount of calcium. How to recover the calcium from solid waste and use the recovered calcium in the preparation of calcium oxide, calcium hydroxide, etc., thereby reducing the mining of natural limestone, lowering carbon emissions in production, and avoiding environmental pollution caused by solid waste dumping, is an urgent problem to be solved.

[0003] Phosphogypsum is an acidic solid waste produced during the wet-process phosphoric acid production process. Its main component is calcium sulfate dihydrate, and it also contains small amounts of free phosphoric acid, phosphorus pentoxide, and other acidic impurities, as well as low levels of heavy metals. To convert calcium sulfate dihydrate in phosphogypsum into calcium hydroxide, it is necessary to remove the acidic and heavy metal impurities to improve the purity of the calcium hydroxide.

[0004] Therefore, it is necessary to develop suitable methods to remove acidic impurities and heavy metal impurities from phosphogypsum solid waste before using it to prepare calcium hydroxide, so as to obtain high-purity calcium hydroxide and reduce environmental pollution caused by solid waste. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention provides a method for preparing calcium hydroxide from solid waste.

[0006] The objective of this invention can be achieved through the following technical solutions: A method for preparing calcium hydroxide from solid waste includes the following steps: Step (1): Crush the solid waste to obtain pretreated solid waste; mix the pretreated solid waste, limestone powder, and activated carbon, and heat and stir to obtain mixture a; Step (2): Mix mixture a, water and ethanol, stir at room temperature, add modified zeolite, heat and stir, centrifuge, dry the lower solid layer, and then use a magnet to adsorb it to obtain mixture b; Step (3): Place the mixture b in a rotary kiln, heat and keep it warm, then transfer it to a vertical cooler, cool it to room temperature, grind it, and sieve it to obtain product 1; Step (4): Add product 1 to a digester, add water, carry out the digestion reaction, concentrate, spray dry, grind, and sieve to obtain calcium hydroxide.

[0007] The method for preparing calcium hydroxide from solid waste includes the following specific steps: Step (1): Crush the solid waste using a jaw crusher to obtain pretreated solid waste; mix the pretreated solid waste, limestone powder, and activated carbon, and stir for 3-4 hours at a temperature of 30-50℃ and a speed of 200-300rpm to obtain mixture a; Furthermore, the solid waste is phosphogypsum solid waste; the feed particle size of the jaw crusher is no more than 100mm, the eccentric shaft speed is 250-300rpm, and the output particle size after crushing is 10-20mm; the ratio of pretreated solid waste, limestone powder, and activated carbon is 100-105g: 15-17g: 5-7g; In step (1), a jaw crusher is used to crush the solid waste to obtain pretreated solid waste; the calcium carbonate in the limestone powder reacts with the acidic impurities in the pretreated solid waste to reduce the acidity and obtain mixture a. Step (2): Mix mixture a, water and ethanol, stir at room temperature for 1-1.2 h, add modified zeolite, heat to 30-35℃, stir at 200-300 rpm for 1.5-1.7 h, centrifuge, dry the lower solid at 100-110℃ for 4-4.5 h, and then use a magnet to adsorb for 35-45 min to obtain mixture b; Furthermore, the ratio of mixture a, water, ethanol, and modified zeolite is 100-105g: 210-220mL: 50-60mL: 10-12g; the volume fraction of ethanol is 95%. In step (2), the modified zeolite adsorbs and complexes the heavy metal ions in mixture a, and then removes them by magnetic adsorption to obtain mixture b; Step (3): Place the mixture b in a rotary kiln, heat it to 1000-1050℃, keep it at that temperature for 35-45 minutes, transfer it to a vertical cooler, cool it to room temperature, grind it, and sieve it to obtain product 1; Furthermore, the sieve used for sieving has a mesh size of 200-300. In step (3), calcium sulfate in mixture b is calcined to obtain calcium oxide, resulting in product 1; Step (4): Add product 1 to a digester, add water, stir at 500-600 rpm and 80-100℃ for 2-2.5 h, concentrate, spray dry at 100-110℃ for 7-8 h, grind, sieve, and obtain calcium hydroxide; Furthermore, an 800-1250 mesh sieve is used for screening; In step (4), product 1 undergoes a digestion reaction with water to obtain calcium hydroxide.

[0008] Furthermore, the modified zeolite described in step (2) is prepared by the following steps: Step A1: After mixing and stirring benzotriazole and DMAC, epichlorohydrin and catalyst are added, reflux is turned on, the mixture is heated and stirred, then cooled and potassium hydroxide solution is added, and stirring is continued to obtain product a; under a protective gas atmosphere, nitroquinoline, ethanol and DMSO are mixed and stirred, a reducing agent is added, and the mixture is heated and stirred under reflux to obtain product b. Step A2: After mixing and stirring products a, b, DMF, and acetonitrile, triethylamine was added, and the mixture was heated and stirred to obtain product c; after mixing and stirring thiophene carboxylic acid and DMF, thionyl chloride was added, and the mixture was heated and stirred to obtain product d; Step A3: Mix product c, DMSO, methanol, and potassium carbonate solution and stir. Add the mixture containing product d in an ice-water bath and heat and stir to obtain product e. Mix product e, DMSO, and ethyl acetate, introduce protective gas, stir, add sodium hydrosulfite, adjust the pH, heat and reflux and stir to obtain product f. Step A4: After drying and cooling the zeolite powder, add it to the hydrolysate m, disperse it by ultrasonication, heat and stir, and centrifuge to obtain product g; mix product g, surface-modified nano-ferric oxide and anhydrous ethanol, disperse them by ultrasonication, add pyridine, heat and stir to obtain product h; mix product f, methanol and DMF, stir, add product h, and react with temperature and pressure to obtain modified zeolite.

[0009] The preparation method of the modified zeolite includes the following specific steps: Step A1: Mix benzotriazole and DMAC and stir for 25-35 min, add epichlorohydrin and catalyst, turn on reflux, stir and heat to 110-120℃, stir for 4-4.5 h, cool to 40-45℃, add potassium hydroxide solution, and continue stirring for 3-3.5 h to obtain product a; Under a protective gas atmosphere, mix nitroquinoline, ethanol and DMSO and stir for 10-15 min, add reducing agent, and reflux and stir at 50-60℃ for 6-6.5 h to obtain product b; Further, the ratio of benzotriazole, DMAC, epichlorohydrin, catalyst, and potassium hydroxide solution is 6.5-8.5g:30-40mL:6-7g:0.15-0.20g:10-15mL; the benzotriazole is 4-methyl1H-benzotriazole or 1,2,3-benzotriazole; the catalyst is tetrabutylammonium bromide or tetrabutylammonium chloride; the mass fraction of potassium hydroxide solution is 25-30%; the ratio of nitroquinoline, ethanol, DMSO, and reducing agent is 9-10g:20-25mL:10-15mL:4.5-8.5g; the nitroquinoline is 5-nitroquinoline or 8-nitroquinoline; the volume fraction of ethanol is 95%; the reducing agent is sodium hydrosulfite or sodium sulfide. In step A1, the secondary amino group of benzotriazole undergoes a ring-opening and ring-closing reaction with epichlorohydrin to give product a containing an epoxy group; the nitro group of nitroquinoline is reduced to an amino group to give product b. Step A2: Mix and stir products a, b, DMF, and acetonitrile for 30-35 min, add triethylamine, stir and heat to 60-70℃, continue stirring for 5-5.5 h to obtain product c; mix and stir thiophene carboxylic acid and DMF for 10-15 min, add thionyl chloride, heat to 40-45℃, stir and react for 3-3.5 h to obtain product d; Further, the ratio of product a, product b, DMF, acetonitrile, and triethylamine is 26-28g: 8.5-9.5g: 35-40mL: 5-10mL: 0.04-0.06g; the ratio of thiophene carboxylic acid, DMF, and thionyl chloride is 9-10g: 35-45mL: 7-8g; and the thiophene carboxylic acid is 5-nitrothiophene-3-carboxylic acid. In step A2, the epoxy group of product a undergoes a ring-opening reaction with the amino group of product b to generate product c containing an alcohol hydroxyl group; thiophene carboxylic acid reacts with thionyl chloride to generate acyl chloride, yielding product d. Step A3: Mix product c, DMSO, methanol, and potassium carbonate solution and stir for 40-45 min. Add the mixture containing product d in an ice-water bath, then heat to 30-35℃ and stir for 8-8.5 h to obtain product e. Mix product e, DMSO, and ethyl acetate, introduce a protective gas, stir for 1-1.2 h, add sodium hydrosulfite, adjust the pH to 7.5-8, heat to 65-75℃, and reflux and stir for 10-10.5 h to obtain product f. Further, the ratio of product c, DMSO, methanol, potassium carbonate solution, and the mixture containing product d is 35-37g:60-65mL:10-15mL:13-15mL:70-75mL; the mass fraction of potassium carbonate solution is 25-30%; the mixture containing product d is obtained by mixing product d and DMSO at a ratio of 11-12g:25-30mL and stirring for 20-25min; the ratio of product e, DMAC, ethyl acetate, and sodium hydrosulfite is 58-60g:120-140mL:40-50mL:20-22g. In step A3, product d reacts with the alcohol hydroxyl group of product c to obtain grafted products containing nitro groups of benzotriazole, quinoline and thiophene, namely product e; the nitro group of product e is reduced to amino group to obtain product f. Step A4: Dry the zeolite powder at 90-100℃ for 5-6 hours, cool it, add it to the hydrolysate m, ultrasonically disperse it for 30-40 minutes, heat it to 85-95℃, stir it for 8-9 hours, and centrifuge it to obtain product g; mix product g, surface-modified nano-ferric oxide, and anhydrous ethanol and ultrasonically disperse it for 1-1.2 hours, add pyridine, heat it to 50-60℃, and stir it for 9-9.5 hours to obtain product h; mix product f, methanol, and DMF and stir it for 30-40 minutes, add product h, heat it to 130-150℃, and react it under a pressure of 2-3 MPa for 12-13 hours to obtain modified zeolite; Further, the ratio of zeolite powder to hydrolysate m is 10-12g:8-10mL; hydrolysate m is obtained by mixing KH792, anhydrous ethanol, and deionized water in a ratio of 12-13g:8-10mL:18-20mL and stirring at room temperature for 4-4.5h; the ratio of product g, surface-modified nano-ferric oxide, anhydrous ethanol, and pyridine is 13-15g:8-10g:110-120mL:0.4-0.6g; the ratio of product f, methanol, DMF, and product h is 6-8g:5-7mL:18-20mL:50-60g. In step A4, the porous zeolite is modified with hydrolysate m to obtain zeolite with amino groups on the surface, i.e., product g. Product g reacts with surface-modified nano-ferric oxide through a ring-opening reaction of amino and epoxy groups to obtain hydroxyl groups. The nano-ferric oxide is then grafted onto the porous zeolite to obtain product h. The surface-modified nano-ferric oxide is KH560-modified nano-ferric oxide. Under high temperature and pressure conditions, the amino groups in product f interact with the polar groups such as hydroxyl groups in product h, promoting the entry of product f into product h, i.e., product f is firmly loaded into the porous zeolite grafted with nano-ferric oxide.

[0010] The beneficial effects of this invention are as follows: This invention discloses a method for preparing calcium hydroxide from solid waste. The method involves first removing the acid from industrial solid waste phosphogypsum with limestone, then removing heavy metals and other impurities with modified zeolite, followed by calcination to obtain calcium oxide, and finally using calcium oxide to react with water to produce calcium hydroxide. This method avoids environmental pollution from accumulated solid waste and also recovers and utilizes a large amount of calcium from solid waste, reducing carbon emissions. It has strong environmental protection and high economic value.

[0011] The modified zeolite used in this invention is obtained by loading product f, obtained from the reaction of benzotriazole, nitroquinoline, and thiophene carboxylic acid, onto product h. Product h is a porous zeolite grafted with nano-ferric oxide. By combining benzotriazole, nitroquinoline, and thiophene carboxylic acid, stable complexes are formed with heavy metal ions in phosphogypsum solid waste through intramolecular synergistic effects, which also helps to remove organic pollutants from phosphogypsum solid waste. Furthermore, by combining nano-ferric oxide, heavy metal ions and organic pollutants are further removed through magnetic adsorption, solving the problem of difficult separation and effectively reducing impurity content. After calcination, high-purity calcium oxide is obtained, which is then digested with water to obtain high-purity calcium hydroxide. Detailed Implementation

[0012] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0013] Example 1 A modified zeolite, the preparation method of which includes the following steps: Step A1: Mix 4-methyl-1H-benzotriazole and DMAC and stir for 25 min. Add epichlorohydrin and tetrabutylammonium bromide, turn on reflux, stir and heat to 110℃, stir for 4 h, cool to 40℃, add potassium hydroxide solution, and continue stirring for 3 h to obtain product a; Under a nitrogen atmosphere, mix 5-nitroquinoline, ethanol, and DMSO and stir for 10 min. Add sodium hydrosulfite and reflux at 50℃ for 6 h to obtain product b; The ratio of 4-methyl-1H-benzotriazole, DMAC, epichlorohydrin, tetrabutylammonium bromide, and potassium hydroxide solution is 6.5 g: 30 mL: 6 g: 0.15 g: 10 mL; the mass fraction of potassium hydroxide solution is 25%; the ratio of 5-nitroquinoline, ethanol, DMSO, and sodium hydrosulfite is 9 g: 20 mL: 10 mL: 4.5 g; the volume fraction of ethanol is 95%. Step A2: Mix and stir products a, b, DMF, and acetonitrile for 30 min, add triethylamine, stir and heat to 60℃, continue stirring for 5 h to obtain product c; mix and stir 5-nitrothiophene-3-carboxylic acid and DMF for 10 min, add thionyl chloride, heat to 40℃, stir and react for 3 h to obtain product d; the molar ratio of product a, product b, DMF, acetonitrile, and triethylamine is 26 g: 8.5 g: 35 mL: 5 mL: 0.04 g; the molar ratio of 5-nitrothiophene-3-carboxylic acid, DMF, and thionyl chloride is 9 g: 35 mL: 7 g; Step A3: Mix product c, DMSO, methanol, and potassium carbonate solution and stir for 40 min. Add the mixture containing product d in an ice-water bath, heat to 30°C, and stir for 8 h to obtain product e. Mix product e, DMSO, and ethyl acetate, purge with nitrogen, stir for 1 h, add sodium hydrosulfite, adjust the pH to 7.5, heat to 65°C, and reflux and stir for 10 h to obtain product f. The ratio of product c, DMSO, methanol, potassium carbonate solution, and the mixture containing product d is 35 g: 60 mL: 10 mL: 13 mL: 70 mL; the mass fraction of potassium carbonate solution is 25%; the mixture containing product d is obtained by mixing product d and DMSO at a ratio of 11 g: 25 mL and stirring for 20 min; the ratio of product e, DMAC, ethyl acetate, and sodium hydrosulfite is 58 g: 120 mL: 40 mL: 20 g. Step A4: Zeolite powder (supplier: Xinyang Mingyou Industrial Co., Ltd., 70 mesh) was dried at 90℃ for 5 hours. After cooling, it was added to hydrolysate m and ultrasonically dispersed at 100W for 30 minutes. The mixture was then heated to 85℃ and stirred for 8 hours. Centrifugation was performed to obtain product g. Product g, surface-modified nano-ferric oxide (supplier: Hangzhou Jiayou New Materials Co., Ltd., 25kg / bag), and anhydrous ethanol were mixed and ultrasonically dispersed for 1 hour. Pyridine was added, and the mixture was heated to 50℃ and stirred for 9 hours to obtain product h. Product f, methanol, and DMF were mixed and stirred for 30 minutes. Product h was added, heated to 130℃, and reacted at 2MPa pressure for 12h to obtain modified zeolite; the ratio of zeolite powder to hydrolysate m was 10g:8mL; hydrolysate m was obtained by mixing KH792, anhydrous ethanol, and deionized water in a ratio of 12g:8mL:18mL and stirring at room temperature for 4h; the ratio of product g, surface-modified nano-ferric oxide, anhydrous ethanol, and pyridine was 13g:8g:110mL:0.4g; the ratio of product f, methanol, DMF, and product h was 6g:5mL:18mL:50g.

[0014] Example 2 A modified zeolite, the preparation method of which includes the following steps: Step A1: Mix 1,2,3-benzotriazole and DMAC and stir for 30 min. Add epichlorohydrin and tetrabutylammonium chloride, turn on reflux, stir and heat to 115℃, stir for 4.3 h, cool to 43℃, add potassium hydroxide solution, and continue stirring for 3.3 h to obtain product a; Under a nitrogen atmosphere, mix 8-nitroquinoline, ethanol, and DMSO and stir for 13 min. Add sodium sulfide, reflux and stir at 55℃ for 6.3 h to obtain product b; The molar ratio of 1,2,3-benzotriazole, DMAC, epichlorohydrin, tetrabutylammonium chloride, and potassium hydroxide solution is 7.5 g: 35 mL: 6.5 g: 0.18 g: 13 mL; the mass fraction of potassium hydroxide solution is 28%; the molar ratio of 8-nitroquinoline, ethanol, DMSO, and sodium sulfide is 9.5 g: 23 mL: 13 mL: 6.5 g; the volume fraction of ethanol is 95%. Step A2: Mix and stir products a, b, DMF, and acetonitrile for 33 min, add triethylamine, stir and heat to 65°C, continue stirring for 5.3 h to obtain product c; mix and stir 5-nitrothiophene-3-carboxylic acid and DMF for 13 min, add thionyl chloride, heat to 43°C, stir and react for 3.3 h to obtain product d; the molar ratio of product a, product b, DMF, acetonitrile, and triethylamine is 27 g: 9.0 g: 38 mL: 8 mL: 0.05 g; the molar ratio of 5-nitrothiophene-3-carboxylic acid, DMF, and thionyl chloride is 9.5 g: 40 mL: 7.5 g; Step A3: Mix product c, DMSO, methanol, and potassium carbonate solution and stir for 43 min. Add the mixture containing product d in an ice-water bath, then heat to 33℃ and stir for 8.3 h to obtain product e. Mix product e, DMSO, and ethyl acetate, purge with nitrogen, stir for 1.1 h, add sodium hydrosulfite, adjust the pH to 7.7, heat to 70℃, and reflux and stir for 10.3 h to obtain product f. The ratio of product c, DMSO, methanol, potassium carbonate solution, and the mixture containing product d is 36 g: 63 mL: 13 mL: 14 mL: 73 mL; the mass fraction of potassium carbonate solution is 28%; the mixture containing product d is obtained by mixing product d and DMSO at a ratio of 11.5 g: 28 mL and stirring for 23 min; the ratio of product e, DMAC, ethyl acetate, and sodium hydrosulfite is 59 g: 130 mL: 45 mL: 21 g. Step A4: Zeolite powder (supplier: Xinyang Mingyou Industrial Co., Ltd., 100 mesh) was dried at 95℃ for 5.5h, cooled, and added to hydrolysate m. It was ultrasonically dispersed at 120W for 35min, heated to 90℃, stirred for 8.5h, and centrifuged to obtain product g. Product g, surface-modified nano-ferric oxide (supplier: Hangzhou Jiayou New Materials Co., Ltd., 25kg / bag), and anhydrous ethanol were mixed and ultrasonically dispersed for 1.1h. Pyridine was added, and the mixture was heated to 55℃ and stirred for 9.3h to obtain product h. Product f, methanol, and DMF were mixed and stirred for 35min. Product h was added, the temperature was raised to 140℃, and the reaction was carried out at a pressure of 2.5MPa for 12.5h to obtain modified zeolite; the ratio of zeolite powder to hydrolysate m was 11g:9mL; hydrolysate m was obtained by mixing KH792, anhydrous ethanol, and deionized water in a ratio of 12.5g:9mL:19mL and stirring at room temperature for 4.3h; the ratio of product g, surface-modified nano-ferric oxide, anhydrous ethanol, and pyridine was 14g:9g:115mL:0.5g; the ratio of product f, methanol, DMF, and product h was 7g:6mL:19mL:55g.

[0015] Example 3 A modified zeolite, the preparation method of which includes the following steps: Step A1: Mix 1,2,3-benzotriazole and DMAC and stir for 35 min. Add epichlorohydrin and tetrabutylammonium bromide, turn on reflux, stir and heat to 120℃, stir for 4.5 h, cool to 45℃, add potassium hydroxide solution, and continue stirring for 3.5 h to obtain product a; Under a nitrogen atmosphere, mix 8-nitroquinoline, ethanol, and DMSO and stir for 15 min. Add sodium sulfide, reflux and stir at 60℃ for 6.5 h to obtain product b; The molar ratio of 1,2,3-benzotriazole, DMAC, epichlorohydrin, tetrabutylammonium bromide, and potassium hydroxide solution is 8.5 g: 40 mL: 7 g: 0.20 g: 15 mL; the mass fraction of potassium hydroxide solution is 30%; the molar ratio of 8-nitroquinoline, ethanol, DMSO, and sodium sulfide is 10 g: 25 mL: 15 mL: 8.5 g; the volume fraction of ethanol is 95%. Step A2: Mix and stir products a, b, DMF, and acetonitrile for 35 min, add triethylamine, stir and heat to 70°C, continue stirring for 5.5 h to obtain product c; mix and stir 5-nitrothiophene-3-carboxylic acid and DMF for 15 min, add thionyl chloride, heat to 45°C, stir and react for 3.5 h to obtain product d; the molar ratio of product a, product b, DMF, acetonitrile, and triethylamine is 28 g: 9.5 g: 40 mL: 10 mL: 0.06 g; the molar ratio of 5-nitrothiophene-3-carboxylic acid, DMF, and thionyl chloride is 10 g: 45 mL: 8 g; Step A3: Mix product c, DMSO, methanol, and potassium carbonate solution and stir for 45 min. Add the mixture containing product d in an ice-water bath, then heat to 35℃ and stir for 8.5 h to obtain product e. Mix product e, DMSO, and ethyl acetate, purge with nitrogen, stir for 1.2 h, add sodium hydrosulfite, adjust the pH to 8, heat to 75℃, and reflux and stir for 10.5 h to obtain product f. The ratio of product c, DMSO, methanol, potassium carbonate solution, and the mixture containing product d is 37 g: 65 mL: 15 mL: 15 mL: 75 mL; the mass fraction of potassium carbonate solution is 30%; the mixture containing product d is obtained by mixing product d and DMSO at a ratio of 12 g: 30 mL and stirring for 25 min; the ratio of product e, DMAC, ethyl acetate, and sodium hydrosulfite is 60 g: 140 mL: 50 mL: 22 g. Step A4: Zeolite powder (supplier: Xinyang Mingyou Industrial Co., Ltd., 120 mesh) was dried at 100℃ for 6 hours. After cooling, it was added to hydrolysate m and ultrasonically dispersed at 150W for 40 minutes. The mixture was then heated to 95℃ and stirred for 9 hours. After centrifugation, product g was obtained. Product g, surface-modified nano-ferric oxide (supplier: Hangzhou Jiayou New Materials Co., Ltd., 25kg / bag), and anhydrous ethanol were mixed and ultrasonically dispersed for 1.2 hours. Pyridine was added, and the mixture was heated to 60℃ and stirred for 9.5 hours to obtain product h. Product f, methanol, and DMF were mixed and stirred for 40 minutes. Product h was added, the temperature was raised to 150℃, and the reaction was carried out at a pressure of 3MPa for 13h to obtain modified zeolite; the ratio of zeolite powder to hydrolysate m was 12g:10mL; hydrolysate m was obtained by mixing KH792, anhydrous ethanol, and deionized water in a ratio of 13g:10mL:20mL and stirring at room temperature for 4.5h; the ratio of product g, surface-modified nano-ferric oxide, anhydrous ethanol, and pyridine was 15g:10g:120mL:0.6g; the ratio of product f, methanol, DMF, and product h was 8g:7mL:20mL:60g.

[0016] Example 4 A method for preparing calcium hydroxide from solid waste includes the following steps: Step (1): The solid waste is crushed using a jaw crusher (supplier: Shandong Ruinachuang Machinery Equipment Co., Ltd., model EP100*125) to obtain pretreated solid waste; the pretreated solid waste, limestone powder (supplier: Lingshou County Ningbo Mineral Products Co., Ltd., 200 mesh), and activated carbon (supplier: Xinghua Carbon Industry Technology Jiangsu Co., Ltd., specification 20kg / piece) are mixed and stirred for 3 hours at 30℃ and 200rpm to obtain mixture a; the solid waste is phosphogypsum solid waste (supplier: Anhui Luyang Building Materials Co., Ltd.); the feed particle size of the jaw crusher is 90mm, the eccentric shaft speed is 250rpm, and the output particle size after crushing is 10-20mm; the ratio of pretreated solid waste, limestone powder, and activated carbon is 100g:15g:5g; Step (2): Mix mixture a, water, and ethanol, stir at room temperature for 1 hour, add the modified zeolite obtained in Example 1, heat to 30°C, stir at 200 rpm for 1.5 hours, centrifuge, dry the lower solid layer at 100°C for 4 hours, and then adsorb it with a magnet for 35 minutes to obtain mixture b; the ratio of mixture a, water, ethanol, and modified zeolite is 100 g: 210 mL: 50 mL: 10 g; the volume fraction of ethanol is 95%; Step (3): Place the mixture b in a rotary kiln (supplier: Hebei Beishang Energy Saving Technology Co., Ltd., electromagnetic heating rotary kiln), heat to 1000℃, keep warm for 35 minutes, transfer to a vertical cooler (supplier: Zhengzhou Mining Machinery, model: LSF36), cool to room temperature, grind, and sieve to obtain product 1; the mesh size of the sieve used for sieving is 200 mesh; Step (4): Add product 1 to a digester, add water, stir at 500 rpm and 80°C for 2 hours, concentrate, spray dry at 100°C for 7 hours, grind, and sieve to obtain calcium hydroxide; use an 800-mesh sieve for sieving; use chemical titration (using a standard hydrochloric acid solution with a concentration of 0.1 mol / L as the titrant and phenolphthalein as the indicator) to test the purity of the obtained calcium hydroxide as 96.4%.

[0017] Example 5 A method for preparing calcium hydroxide from solid waste includes the following steps: Step (1): The solid waste is crushed using a jaw crusher (supplier: Shandong Ruinachuang Machinery Equipment Co., Ltd., model EP100*125) to obtain pretreated solid waste; the pretreated solid waste, limestone powder (supplier: Lingshou County Ningbo Mineral Products Co., Ltd., 200 mesh), and activated carbon (supplier: Xinghua Carbon Industry Technology Jiangsu Co., Ltd., specification 20kg / piece) are mixed and stirred at 40℃ and 250rpm for 3.5h to obtain mixture a; the solid waste is phosphogypsum solid waste (supplier: Anhui Luyang Building Materials Co., Ltd.); the feed particle size of the jaw crusher is 80mm, the eccentric shaft speed is 270rpm, and the output particle size after crushing is 10-20mm; the ratio of pretreated solid waste, limestone powder, and activated carbon is 103g:16g:6g; Step (2): Mix mixture a, water, and ethanol, stir at room temperature for 1.1 h, add the modified zeolite obtained in Example 2, heat to 33°C, stir at 250 rpm for 1.6 h, centrifuge, dry the lower solid layer at 105°C for 4.3 h, and then adsorb it with a magnet for 40 min to obtain mixture b; the ratio of mixture a, water, ethanol, and modified zeolite is 103 g: 215 mL: 55 mL: 11 g; the volume fraction of ethanol is 95%; Step (3): Place the mixture b in a rotary kiln (supplier: Hebei Beishang Energy Saving Technology Co., Ltd., electromagnetic heating rotary kiln), heat to 1020℃, keep warm for 40min, transfer to a vertical cooler (supplier: Zhengzhou Mining Machinery, model: LSF36), cool to room temperature, grind, and sieve to obtain product 1; the sieve used for sieving is 250 mesh. Step (4): Add product 1 to the digester, add water, stir at 550 rpm and 90°C for 2.3 h, concentrate, spray dry at 105°C for 7.5 h, grind, and sieve to obtain calcium hydroxide; sieve using a 1000 mesh sieve; test the purity of the obtained calcium hydroxide using chemical titration (using a standard hydrochloric acid solution with a concentration of 0.1 mol / L as the titrant and phenolphthalein as the indicator) and it is 96.8%.

[0018] Example 6 A method for preparing calcium hydroxide from solid waste includes the following steps: Step (1): The solid waste is crushed using a jaw crusher (supplier: Shandong Ruinachuang Machinery Equipment Co., Ltd., model EP100*125) to obtain pretreated solid waste; the pretreated solid waste, limestone powder (supplier: Lingshou County Ningbo Mineral Products Co., Ltd., 200 mesh), and activated carbon (supplier: Xinghua Carbon Industry Technology Jiangsu Co., Ltd., specification 20kg / piece) are mixed and stirred at 50℃ and 300rpm for 4 hours to obtain mixture a; the solid waste is phosphogypsum solid waste (supplier: Anhui Luyang Building Materials Co., Ltd.); the feed particle size of the jaw crusher is 90mm, the eccentric shaft speed is 300rpm, and the output particle size after crushing is 10-20mm; the ratio of pretreated solid waste, limestone powder, and activated carbon is 105g:17g:7g; Step (2): Mix mixture a, water, and ethanol, stir at room temperature for 1.2 h, add the modified zeolite obtained in Example 3, heat to 35°C, stir at 300 rpm for 1.7 h, centrifuge, dry the lower solid layer at 110°C for 4.5 h, and then adsorb it with a magnet for 45 min to obtain mixture b; the ratio of mixture a, water, ethanol, and modified zeolite is 105 g: 220 mL: 60 mL: 12 g; the volume fraction of ethanol is 95%; Step (3): Place the mixture b in a rotary kiln (supplier: Hebei Beishang Energy Saving Technology Co., Ltd., electromagnetic heating rotary kiln), heat to 1050℃, keep warm for 45min, transfer to a vertical cooler (supplier: Zhengzhou Mining Machinery, model: LSF36), cool to room temperature, grind, and sieve to obtain product 1; the mesh size of the sieve used for sieving is 300 mesh; Step (4): Add product 1 to a digester, add water, stir at 600 rpm and 100°C for 2.5 h, concentrate, spray dry at 110°C for 8 h, grind, and sieve to obtain calcium hydroxide; sieve using a 1250 mesh sieve; test the purity of the obtained calcium hydroxide using chemical titration (using a standard hydrochloric acid solution with a concentration of 0.1 mol / L as the titrant and phenolphthalein as the indicator) and it is 96.6%.

[0019] Comparative Example 1 Compared with Example 6, the product f used in the modified zeolite was replaced with a mixture of 1,2,3-benzotriazole, 8-nitroquinoline, and 5-nitrothiophene-3-carboxylic acid in a molar ratio of 1:2:2, while the rest remained the same as in Example 6, to obtain solid calcium hydroxide. The purity of the obtained calcium hydroxide was 87.4% as determined by chemical titration (using a 0.1 mol / L standard hydrochloric acid solution as the titrant and phenolphthalein as the indicator).

[0020] Comparative Example 2 Compared with Example 6, modified zeolite was used in step (1) to prepare mixture a-1, and then mixture a-1 was calcined to obtain product 1-1. Finally, calcium hydroxide was obtained by digestion reaction. Specifically, the solid waste was crushed using a jaw crusher (supplier: Shandong Ruinachuang Machinery Equipment Co., Ltd., model EP100*125) to obtain pretreated solid waste; the pretreated solid waste, limestone powder (supplier: Lingshou County Ningbo Mineral Products Co., Ltd., 200 mesh), activated carbon (supplier: Xinghua Carbon Industry Technology Jiangsu Co., Ltd., specification 20kg / piece), and modified zeolite from Example 3 were mixed and stirred at 50℃ and 300rpm for 4 hours to obtain mixture a-1; the solid waste was phosphogypsum solid waste (supplier: Anhui Luyang Building Materials Co., Ltd.); the feed particle size of the jaw crusher was 90mm, the eccentric shaft speed was 300rpm, and the output particle size after crushing was 10-20mm; the ratio of pretreated solid waste, limestone powder, activated carbon, and modified zeolite was 105g:17g:7g:12g; Mixture a-1 was placed in a rotary kiln (supplier: Hebei Beishang Energy Saving Technology Co., Ltd., electromagnetic heating rotary kiln), heated to 1050℃, held for 45 minutes, transferred to a vertical cooler (supplier: Zhengzhou Mining Machinery, model: LSF36), cooled to room temperature, ground, and sieved to obtain product 1-1; the sieve used for sieving was 300 mesh. Product 1-1 was added to a digester, water was added, and the mixture was stirred at 600 rpm and 100°C for 2.5 h. The mixture was then concentrated, spray-dried at 110°C for 8 h, ground, and sieved to obtain calcium hydroxide. A 1250-mesh sieve was used for sieving. The purity of the obtained calcium hydroxide was determined to be 61.3% by chemical titration (using a 0.1 mol / L standard hydrochloric acid solution as the titrant and phenolphthalein as the indicator).

[0021] Comparative Example 3 Compared with Example 6, all the modified zeolite used was replaced with activated carbon, while the rest was exactly the same as in Example 6, to obtain solid calcium hydroxide. The purity of the obtained calcium hydroxide was 83.6% when tested by chemical titration (using a standard hydrochloric acid solution with a concentration of 0.1 mol / L as the titrant and phenolphthalein as the indicator).

[0022] The above description is merely an example and illustration of the concept of the present invention. Those skilled in the art can make various modifications or additions to the specific embodiments described or use similar methods to replace them, as long as they do not deviate from the concept of the invention or exceed the scope defined in the claims, they should all fall within the protection scope of the present invention.

Claims

1. A method for preparing calcium hydroxide from solid waste, characterized in that: Includes the following steps: Step (1): Crush the solid waste to obtain pretreated solid waste; mix the pretreated solid waste, limestone powder, and activated carbon, and heat and stir to obtain mixture a; Step (2): Mix mixture a, water and ethanol, stir at room temperature, add modified zeolite, heat and stir, centrifuge, dry the lower solid layer, and then use a magnet to adsorb it to obtain mixture b; Step (3): Place the mixture b in a rotary kiln, heat and keep it warm, then transfer it to a vertical cooler, cool it to room temperature, grind it, and sieve it to obtain product 1; Step (4): Add product 1 to a digester, add water, carry out the digestion reaction, concentrate, spray dry, grind, and sieve to obtain calcium hydroxide.

2. The method for preparing calcium hydroxide from solid waste according to claim 1, characterized in that: In step (1), the solid waste is phosphogypsum solid waste; a jaw crusher is used for crushing, the feed particle size of the jaw crusher is no more than 100mm, the eccentric shaft speed is 250-300rpm, and the output particle size after crushing is 10-20mm.

3. The method for preparing calcium hydroxide from solid waste according to claim 1, characterized in that: In step (3), the mesh size of the sieve used for sieving is 200-300 mesh.

4. The method for preparing calcium hydroxide from solid waste according to claim 1, characterized in that: In step (4), the sieving is performed using an 800-1250 mesh sieve.

5. The method for preparing calcium hydroxide from solid waste according to claim 1, wherein the modified zeolite in step (2) is prepared by the following steps: Step A1: After mixing and stirring benzotriazole and DMAC, epichlorohydrin and catalyst are added, reflux is turned on, the mixture is heated and stirred, then cooled and potassium hydroxide solution is added, and stirring is continued to obtain product a; under a protective gas atmosphere, nitroquinoline, ethanol and DMSO are mixed and stirred, a reducing agent is added, and the mixture is heated and stirred under reflux to obtain product b. Step A2: After mixing and stirring products a, b, DMF, and acetonitrile, triethylamine was added, and the mixture was heated and stirred to obtain product c; after mixing and stirring thiophene carboxylic acid and DMF, thionyl chloride was added, and the mixture was heated and stirred to obtain product d; Step A3: Mix product c, DMSO, methanol, and potassium carbonate solution and stir. Add the mixture containing product d in an ice-water bath and heat and stir to obtain product e. Mix product e, DMSO, and ethyl acetate, introduce protective gas, stir, add sodium hydrosulfite, adjust the pH, heat and reflux and stir to obtain product f. Step A4: After drying and cooling the zeolite powder, add it to the hydrolysate m, disperse it by ultrasonication, heat and stir, and centrifuge to obtain product g; mix product g, surface-modified nano-ferric oxide and anhydrous ethanol, disperse them by ultrasonication, add pyridine, heat and stir to obtain product h; mix product f, methanol and DMF, stir, add product h, and react with temperature and pressure to obtain modified zeolite.

6. The method for preparing calcium hydroxide from solid waste according to claim 5, characterized in that: In step A1, the benzotriazole is 4-methyl1H-benzotriazole or 1,2,3-benzotriazole.

7. A method for preparing calcium hydroxide from solid waste according to claim 5, characterized in that: In step A1, the nitroquinoline is 5-nitroquinoline or 8-nitroquinoline.

8. A method for preparing calcium hydroxide from solid waste according to claim 5, characterized in that: In step A2, the thiophenic acid is 5-nitrothiophen-3-carboxylic acid.