Filter cloth for hydrometallurgical purification and extraction

Abstract

The present application relates to the technical field of industrial filter cloth, and particularly relates to a special filter cloth for hydrometallurgical purification and extraction, which comprises the following raw materials in parts by weight: 30-45 parts of homopolymerized polypropylene, 15-21 parts of copolymerized polypropylene, 10-18 parts of maleic anhydride grafted polypropylene, 3-9 parts of modified carbon nanotube, 3-5 parts of polyvinylidene fluoride and 0.2-0.4 parts of antioxidant BHT; wherein the modified carbon nanotube is obtained by in-situ twice carbonization of carbon nanotube-cerium-phenanthroline complex, and the special filter cloth for hydrometallurgical purification and extraction prepared by the present application has excellent corrosion resistance at high temperature, and the preparation method is simple and easy to implement, the production cost is low, and the present application has good economic benefits.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of industrial filter cloth, and in particular to a filter cloth special for hydrometallurgy purification and extraction. BACKGROUND

[0002] Hydrometallurgy is a method of separating metal compounds from non-metallic impurities in a liquid phase (usually water). In the hydrometallurgy process, extraction is an important separation and purification technology that can separate target metal ions from other metal ions and impurities, and concentrate and extract the target metal. The special filter cloth for extraction is a key material in the extraction process, which is used to separate the liquid containing the target metal and solid impurities, and should have certain high-temperature corrosion resistance, because the hydrometallurgy process often needs to be treated at high temperature, and the liquid treated may also contain acidic, alkaline or other chemicals, which can corrode the filter cloth and cause its performance to decline or fail.

[0003] Chinese patent CN112206581B discloses a special industrial filter cloth for hydrometallurgy purification section, which comprises the following raw materials by weight: polypropylene 6-8 parts, polyethylene 3-4 parts, anhydrous ethanol 30-50 parts, PET 8-12 parts, component A 10-20 parts, component B 20-30 parts, diphenylsilicone diol 3-6 parts, deionized water 60-70 parts and antioxidant BHT 0.2-0.4 parts; wherein, component A has good electrical insulation and non-flammability, small thermal shrinkage and chemical corrosion resistance, component B introduces a hydrophilic group, and the prepared filter cloth has good adaptability under high temperature, acidic or alkaline conditions. However, the synthesis steps of component A and component B in the present application are complex, which is not suitable for industrial production, and the corrosion resistance under high temperature, acidic or alkaline conditions is poor. SUMMARY

[0004] Therefore, the present application aims to provide a special filter cloth for hydrometallurgy purification and extraction to solve the problem of poor corrosion resistance of traditional industrial filter cloth under high temperature, acidic or alkaline conditions.

[0005] Based on the above purpose, the present application provides a special filter cloth for hydrometallurgy purification and extraction, which comprises the following raw materials by weight: homopolymer polypropylene 30-45 parts, copolymer polypropylene 15-21 parts, maleic anhydride grafted polypropylene 10-18 parts, modified carbon nanotube 3-9 parts, polyvinylidene fluoride 3-5 parts and antioxidant BHT 0.2-0.4 parts.

[0006] The synthesis steps of the modified carbon nanotube are as follows:

[0007] S1: carbon nanotubes are heated at 300-350℃ for 3-5h, washed, dried, then immersed in concentrated nitric acid with a mass concentration of 60-70%, heated at 70-80℃ for 3-5h, then cleaned with deionized water until pH = 6.5-7, dried, to obtain acid-treated carbon nanotubes;

[0008] S2: acid-treated carbon nanotubes, cerium nitrate hexahydrate, and phenanthroline are added to anhydrous ethanol, heated and stirred at 50-60℃ for 4-6h to obtain a mixed solution, then the mixed solution is poured into a reaction kettle, heated at 100-110℃ for 6-8h, dried, to obtain carbon nanotube-cerium-phenanthroline complexes;

[0009] S3: the carbon nanotube-cerium-phenanthroline complexes are placed in a tube furnace for primary carbonization, carbonized at 300-400℃ under N2 atmosphere for 1-2h, then the primary carbonized carbon nanotube-cerium-phenanthroline complexes and potassium hydroxide are ground together for 2-4h to obtain a mixture, then the mixture is transferred to a tube furnace for secondary carbonization, carbonized at 800-900℃ under N2 atmosphere for 2-3h, washed, dried, to obtain modified carbon nanotubes.

[0010] The homopolymerized polypropylene has a melt flow rate of 2.5-4g / 10min under the action of a load of 2.16kg at 230℃.

[0011] The maleic anhydride grafted polypropylene has a melt flow rate of 3-6g / 10min under the action of a load of 2.16kg at 230℃.

[0012] The polyvinylidene fluoride has a melt flow rate of 1-2g / 10min under the action of a load of 2.16kg at 230℃.

[0013] The copolymerized polypropylene is an ethylene-propylene copolymer, the molar percentage content of ethylene groups is 3-4%, and the melt flow rate is 5-8g / 10min under the action of a load of 2.16kg at 230℃.

[0014] In step S1, the diameter of the carbon nanotubes is 10-20nm, and the length is 5-15μm.

[0015] In step S2, the mass ratio of acid-treated carbon nanotubes, cerium nitrate hexahydrate, phenanthroline, and anhydrous ethanol is 10:1-4:2-8:50-70.

[0016] The temperature rising rate of the once carbonization in the step S3 is 3-5 DEG C / min, the N2 flow rate is 1.5-2.5 L / min, the temperature rising rate of the twice carbonization is 1-2 DEG C / min, the temperature falling rate of the twice carbonization is 5-10 DEG C / min, and the N2 flow rate is 1.5-2.5 L / min.

[0017] The mass ratio of the carbon nanotube-cerium-phenanthroline complex and potassium hydroxide in the step S3 is 10:1-3.

[0018] Further, the application also provides a preparation method of the special filter cloth for hydrometallurgical purification and extraction, comprising the following steps:

[0019] S4: mixing the homopolypropylene, the copolypropylene, the maleic anhydride grafted polypropylene, the modified carbon nanotube and the polyvinylidene fluoride with the antioxidant BHT, heating and melting through a double screw extruder, then extruding the melt to a spinning box for spinning, cooling and setting the spun yarn to obtain a mesh;

[0020] S5: arranging the mesh along the warp and weft to weave the mesh to obtain the filter cloth, then setting the filter cloth at a high temperature of 160-190 DEG C, then calendering the filter cloth at a temperature of 130-150 DEG C and a pressure of 10 KPa to obtain a filter cloth with a air permeability of 50-100 L / m 2 / s, finally electrostatically treating to obtain a special filter cloth for hydrometallurgical purification and extraction.

[0021] The working temperature of the double screw extruder in the step S4 is 160-180 DEG C, and the working temperature of the spinning box is 160-170 DEG C, and the working pressure is 15-20 MPa.

[0022] The warp diameter is 0.135-0.23 mm, the weft diameter is 600-1500 D, the warp weaving density is 30-88 roots / cm, the weft weaving density is 12-23 roots / cm, and the organization structure of the prepared special filter cloth for hydrometallurgical purification and extraction is 8 harness twill.

[0023] The application has the following beneficial effects:

[0024] The application provides a filter cloth special for hydrometallurgical purification and extraction, wherein the modified carbon nanotubes are obtained by twice carbonization in situ of carbon nanotube-cerium-phenanthroline complex, the first carbonization causes the phenanthroline on the surface to form a uniform carbon layer on the surface of the carbon nanotube, and the second carbonization is after alkali treatment, wherein the alkali treatment and rare earth help to promote the formation of a uniform and dense carbon layer and the activation of nitrogen on the surface of the carbon layer in the subsequent high-temperature carbonization process, the uniform and dense carbon layer helps to improve the corrosion resistance of the carbon nanotube to the filter cloth at high temperature, and the rare earth improves the crystallinity of the polypropylene, further improving the corrosion resistance of the filter cloth at high temperature, and the filter cloth prepared by the application has excellent corrosion resistance at high temperature.

[0025] The application provides a filter cloth special for hydrometallurgical purification and extraction, wherein the added homopolymer polypropylene, copolymer polypropylene, maleic anhydride grafted polypropylene and polyvinylidene fluoride and the like can effectively improve the strength and durability of the filter cloth, the antioxidant BHT can reduce the aging and degradation degree of the filter cloth and prolong the service life, the preparation method of the application is simple and easy to implement, the production cost is low, and the application has good economic benefits. DETAILED DESCRIPTION

[0026] In order to make the purpose, technical scheme and advantages of the application clearer, the application is further described in detail below with specific examples.

[0027] The properties of the raw materials in the specific embodiment of the application are as follows:

[0028] The melt flow rate of the homopolymer polypropylene is 2.8 g / 10 min under the action of 230 DEG C and a load of 2.16 kg;

[0029] The melt flow rate of the maleic anhydride grafted polypropylene is 4.5 g / 10 min under the action of 230 DEG C and a load of 2.16 kg;

[0030] The melt flow rate of the polyvinylidene fluoride is 1.2 g / 10 min under the action of 230 DEG C and a load of 2.16 kg;

[0031] The copolymer polypropylene is an ethylene-propylene copolymer, the molar percentage content of ethylene group is 3.2%, and the melt flow rate is 6.3 g / 10 min under the action of 230 DEG C and a load of 2.16 kg;

[0032] The diameter of the carbon nanotube is 15 nm, and the length is 8 μm.

[0033] Example 1

[0034] A filter cloth special for hydrometallurgical purification and extraction, the preparation method thereof comprises the following steps:

[0035] S1: carbon nanotubes were heated at 300℃ for 3h, washed, dried, then immersed in concentrated nitric acid with a mass concentration of 60%, heated at 70℃ for 3h, then cleaned with deionized water until pH = 6.5, dried, to obtain acid-treated carbon nanotubes;

[0036] S2: 10g of acid-treated carbon nanotubes, 1g of cerium nitrate hexahydrate and 2g of phenanthroline were added to 50g of anhydrous ethanol, heated and stirred at 50℃ for 4h to obtain a mixed solution, then the mixed solution was poured into a reaction kettle, heated at 100℃ for 6h, dried to obtain a carbon nanotube-cerium-phenanthroline complex;

[0037] S3: 10g of the carbon nanotube-cerium-phenanthroline complex was placed in a tube furnace for primary carbonization, the heating rate was 3℃ / min, carbonized at 300℃ for 1h under N2 atmosphere, the N2 flow rate was 1.5L / min, then the primary carbonized carbon nanotube-cerium-phenanthroline complex and 1g of potassium hydroxide were ground together for 2h to obtain a mixture, then the mixture was transferred to a tube furnace for secondary carbonization, the heating rate was 1℃ / min, carbonized at 800℃ for 2h under N2 atmosphere, the N2 flow rate was 1.5L / min, washed, dried to obtain modified carbon nanotubes;

[0038] S4: 30g of homopolymer polypropylene, 15g of copolymer polypropylene, 10g of maleic anhydride grafted polypropylene, 3g of modified carbon nanotubes, 3g of polyvinylidene fluoride and 0.2g of antioxidant BHT were mixed, heated and melted by a double screw extruder, the working temperature was 160℃, then the melt was extruded into a spinning box for spinning, the working temperature of the spinning box was 160℃, the working pressure was 15MPa, the spinning was cooled and shaped to obtain a mesh;

[0039] S5: the mesh was arranged in warp and weft, the warp diameter was 0.16mm, the weft diameter was 1000D, the warp weaving density was 50 roots / cm, the weft weaving density was 18 roots / cm, then high temperature setting at 160℃ was carried out, then the filter cloth was calendered at 130℃ and 10KPa to obtain a permeability of 80L / m 2 / s, finally electrostatic treatment was carried out to obtain a wet metallurgical leaching purification special filter cloth with a structure of 8 harnesses.

[0040] Example 2

[0041] A wet metallurgical purification extraction special filter cloth, the preparation method comprising the following steps:

[0042] S1: carbon nanotubes were heated at 325℃ for 4h, washed, dried, then immersed in concentrated nitric acid with a mass concentration of 65%, heated at 75℃ for 4h, then cleaned with deionized water until pH = 6.8, dried, to obtain acid-treated carbon nanotubes;

[0043] S2: 10g of acid-treated carbon nanotubes, 2.5g of cerium nitrate hexahydrate and 5g of phenanthroline were added to 60g of anhydrous ethanol, heated and stirred at 55℃ for 5h to obtain a mixed solution, then the mixed solution was poured into a reaction kettle, heated at 105℃ for 7h, dried to obtain a carbon nanotube-cerium-phenanthroline complex;

[0044] S3: 10g of the carbon nanotube-cerium-phenanthroline complex was placed in a tube furnace for primary carbonization, the heating rate was 4℃ / min, carbonized at 350℃ for 1.5h under N2 atmosphere, the N2 flow rate was 2L / min, then the primary carbonized carbon nanotube-cerium-phenanthroline complex and 2g of potassium hydroxide were ground together for 3h to obtain a mixture, then the mixture was transferred to a tube furnace for secondary carbonization, the heating rate was 1.5℃ / min, carbonized at 850℃ for 2.5h under N2 atmosphere, the N2 flow rate was 2L / min, washed, dried to obtain modified carbon nanotubes;

[0045] S4: 37.5g of homopolymer polypropylene, 18g of copolymer polypropylene, 14g of maleic anhydride grafted polypropylene, 6g of modified carbon nanotubes, 4g of polyvinylidene fluoride and 0.3g of antioxidant BHT were mixed, heated and melted by a double screw extruder, the working temperature was 170℃, then the melt was extruded into a spinning box for spinning, the working temperature of the spinning box was 165℃, the working pressure was 17MPa, the spinning was cooled and shaped to obtain a mesh;

[0046] S5: the mesh was arranged in warp and weft, the warp diameter was 0.16mm, the weft diameter was 1000D, the warp weaving density was 50 roots / cm, the weft weaving density was 18 roots / cm, then high temperature setting at 175℃, then calendering the filter cloth at 140℃ and 10KPa to obtain a permeability of 80L / m 2 / s, finally electrostatic treatment, to obtain a wet metallurgical leaching purification special filter cloth with a structure of 8 harnesses.

[0047] Example 3

[0048] A wet metallurgical purification extraction special filter cloth, the preparation method comprising the following steps:

[0049] S1: carbon nanotubes were heated at 350℃ for 5h, washed, dried, then immersed in concentrated nitric acid with a mass concentration of 70%, heated at 80℃ for 5h, then cleaned with deionized water until pH = 7, dried, to obtain acid-treated carbon nanotubes;

[0050] S2: 10g of acid-treated carbon nanotubes, 4g of cerium nitrate hexahydrate and 8g of phenanthroline were added to 70g of anhydrous ethanol, heated and stirred at 60℃ for 6h to obtain a mixed solution, then the mixed solution was poured into a reaction kettle, heated at 110℃ for 8h, dried to obtain a carbon nanotube-cerium-phenanthroline complex;

[0051] S3: 10g of the carbon nanotube-cerium-phenanthroline complex was placed in a tube furnace for primary carbonization, the heating rate was 5℃ / min, carbonized at 400℃ under N2 atmosphere for 2h, the N2 flow rate was 2.5L / min, then the primary carbonized carbon nanotube-cerium-phenanthroline complex was ground together with 3g of potassium hydroxide for 4h to obtain a mixture, then the mixture was transferred to a tube furnace for secondary carbonization, the heating rate was 2℃ / min, carbonized at 900℃ under N2 atmosphere for 3h, the N2 flow rate was 2.5L / min, washed, dried to obtain modified carbon nanotubes;

[0052] S4: 45g of homopolymer polypropylene, 21g of copolymer polypropylene, 18g of maleic anhydride grafted polypropylene, 9g of modified carbon nanotubes, 5g of polyvinylidene fluoride and 0.4g of antioxidant BHT were mixed, heated and melted by a double screw extruder, the working temperature was 180℃, then the melt was extruded into a spinning box for spinning, the working temperature of the spinning box was 170℃, the working pressure was 20MPa, the spinning was cooled and shaped to obtain a mesh;

[0053] S5: the mesh was arranged in warp and weft, the warp diameter was 0.16mm, the weft diameter was 1000D, the warp weaving density was 50 roots / cm, the weft weaving density was 18 roots / cm, then high temperature setting at 190℃, then calendering the filter cloth at 150℃ and 10KPa to obtain a permeability of 80L / m 2 / s, finally electrostatic treatment, to obtain a wet metallurgical leaching purification special filter cloth with a structure of 8 harnesses.

[0054] Example 4

[0055] A wet metallurgical purification extraction special filter cloth, the preparation method comprising the following steps:

[0056] S1: same as example 2;

[0057] S2: 10 g of acid-treated carbon nanotubes, 1 g of cerium nitrate hexahydrate and 5 g of phenanthroline were added to 60 g of anhydrous ethanol, heated and stirred at 55°C for 5 h to obtain a mixed solution, and then the mixed solution was poured into a reaction kettle and heated at 105°C for 7 h, and dried to obtain a carbon nanotube-cerium-phenanthroline complex;

[0058] S3: the same as in Example 2; S4: the same as in Example 2; S5: the same as in Example 2.

[0059] Example 5

[0060] A filter cloth special for hydrometallurgical purification extraction, a preparation method thereof comprises the following steps:

[0061] S1: the same as in Example 2;

[0062] S2: 10 g of acid-treated carbon nanotubes, 4 g of cerium nitrate hexahydrate and 5 g of phenanthroline were added to 60 g of anhydrous ethanol, heated and stirred at 55°C for 5 h to obtain a mixed solution, and then the mixed solution was poured into a reaction kettle and heated at 105°C for 7 h, and dried to obtain a carbon nanotube-cerium-phenanthroline complex;

[0063] S3: the same as in Example 2; S4: the same as in Example 2; S5: the same as in Example 2.

[0064] Comparative Example 1

[0065] A filter cloth special for hydrometallurgical purification extraction, a preparation method thereof comprises the following steps:

[0066] S1: the same as in Example 1;

[0067] S2: 10 g of acid-treated carbon nanotubes and 5 g of phenanthroline were added to 60 g of anhydrous ethanol, heated and stirred at 55°C for 5 h to obtain a mixed solution, and then the mixed solution was poured into a reaction kettle and heated at 105°C for 7 h, and dried to obtain a carbon nanotube-phenanthroline mixture;

[0068] S3: 10 g of the carbon nanotube-phenanthroline mixture was placed in a tube furnace for primary carbonization, the temperature was raised at a rate of 4°C / min, and carbonization was carried out at 350°C for 1.5 h under N2 atmosphere, the N2 flow rate was 2 L / min, then the primary carbonized carbon nanotube-phenanthroline mixture was ground together with 2 g of potassium hydroxide for 3 h to obtain a mixture, and then the mixture was transferred to a tube furnace for secondary carbonization, the temperature was raised at a rate of 1.5°C / min, and carbonization was carried out at 850°C for 2.5 h under N2 atmosphere, the N2 flow rate was 2 L / min, and then the mixture was washed and dried to obtain modified carbon nanotubes;

[0069] S4: the same as in Example 2; S5: the same as in Example 2.

[0070] Comparative Example 2

[0071] A filter cloth for hydrometallurgical purification and extraction, the preparation method comprising the following steps:

[0072] S1: same as example 2;

[0073] S2: 10g of acid-treated carbon nanotubes and 2.5g of cerium nitrate hexahydrate were added to 60g of anhydrous ethanol, heated and stirred at 55℃ for 5h to obtain a mixed solution, and then the mixed solution was poured into a reaction kettle and heated at 105℃ for 7h, and then dried to obtain a carbon nanotube-cerium mixture;

[0074] S3: 10g of the carbon nanotube-cerium mixture was placed in a tube furnace for primary carbonization, the heating rate was 4℃ / min, carbonized at 350℃ for 1.5h under N2 atmosphere, the N2 flow rate was 2L / min, and then the primary carbonized carbon nanotube-cerium mixture was ground together with 2g of potassium hydroxide for 3h to obtain a mixture, and then the mixture was transferred to a tube furnace for secondary carbonization, the heating rate was 1.5℃ / min, carbonized at 850℃ for 2.5h under N2 atmosphere, the N2 flow rate was 2L / min, washed, and dried to obtain modified carbon nanotubes;

[0075] S4: same as example 2; S5: same as example 2.

[0076] Comparative example 3

[0077] A filter cloth for hydrometallurgical purification and extraction, the preparation method comprising the following steps:

[0078] S1: 37.5g of homopolymer polypropylene, 18g of copolymer polypropylene, 14g of maleic anhydride grafted polypropylene, 6g of carbon nanotubes, 4g of polyvinylidene fluoride, and 0.3g of antioxidant BHT were mixed, heated and melted by a double screw extruder, the working temperature was 170℃, and then the melt was extruded into a spinning box for spinning, the working temperature of the spinning box was 165℃, and the working pressure was 17MPa, and the spinning was cooled and shaped to obtain a mesh;

[0079] S2: the mesh was arranged in warp and weft, the warp diameter was 0.16mm, the weft diameter was 1000D, the warp weaving density was 50 roots / cm, the weft weaving density was 18 roots / cm, and then high temperature setting at 175℃ was carried out, and then the filter cloth was calendered at 140℃ and 10KPa to obtain a permeability of 80L / m 2 / s, and finally electrostatic treatment was carried out to obtain a hydrometallurgical leaching purification special filter cloth with a weave structure of 8 harnesses.

[0080] Comparative example 4

[0081] A filter cloth for hydrometallurgical purification and extraction, the preparation method comprising the following steps:

[0082] S1: same as example 2; S2: same as example 2;

[0083] S3: 10 g of carbon nanotube-cerium-phenanthroline complex was put into a tube furnace for primary carbonization, the heating rate was 4℃ / min, carbonization was carried out at 350℃ for 1.5 h under N2 atmosphere, the N2 flow rate was 2 L / min, then secondary carbonization was carried out, the heating rate was 1.5℃ / min, carbonization was carried out at 850℃ for 2.5 h under N2 atmosphere, the N2 flow rate was 2 L / min, washing, drying, to obtain modified carbon nanotubes;

[0084] S4: same as example 2; S5: same as example 2.

[0085] Comparative example 5

[0086] A filter cloth special for hydrometallurgical purification and extraction, and a preparation method thereof, the preparation method comprising the following steps:

[0087] S1: same as example 2;

[0088] S2: same as example 2;

[0089] S3: 10 g of carbon nanotube-cerium-phenanthroline complex was put into a tube furnace and 2 g of potassium hydroxide was ground together for 3 h to obtain a mixture, then the mixture was transferred into a tube furnace for carbonization, the heating rate was 1.5℃ / min, carbonization was carried out at 850℃ for 2.5 h under N2 atmosphere, the N2 flow rate was 2 L / min, washing, drying, to obtain modified carbon nanotubes;

[0090] S4: same as example 2; S5: same as example 2.

[0091] Performance test:

[0092] Tensile strength test: the filter cloths special for hydrometallurgical purification and extraction prepared in examples 1-5 and comparative examples 1-5 were subjected to performance test, initial tensile strength test was carried out at 25℃ first, then tensile strength test was carried out every 5℃, when the tensile strength retention rate of the filter cloth was lower than 90%, the temperature and the tensile strength retention rate at the temperature were recorded, and the data were recorded, the test results are shown in Table 1;

[0093] Corrosion resistance test: the filter cloths special for hydrometallurgical purification and extraction prepared in examples 1-5 and comparative examples 1-5 were respectively placed in 10% dilute hydrochloric acid and 10% sodium hydroxide solution at 25℃ and 80℃ for 7 days, then the tensile strength of the filter cloth was measured, the results are shown in Table 1;

[0094] Water permeability test: The examples 1-5 and comparative examples 1-5 were placed in a water solution with a pressure difference of 100 Pa on both sides, and the water permeability through the filter cloth per unit area was tested, and the test results are shown in Table 1 below.

[0095] Table 1 Performance test results of examples 1-5 and comparative examples 1-5

[0096]

[0097]

[0098] Data analysis: As can be seen from examples 1-5, the filter cloth prepared by the present application for hydrometallurgical purification and extraction has excellent corrosion resistance at high temperature, and has excellent tensile strength and water permeability. As can be seen from examples 2 and comparative examples 1-3, the rare earth and phenanthroline synergistically improve the tensile strength of the filter cloth and the corrosion resistance at high temperature, which may be due to the construction of the dense and uniform carbon layer and the improvement of the crystallinity of the polypropylene in the filter cloth. As can be seen from examples 2 and comparative examples 4-5, alkali treatment and twice carbonization are crucial for improving the corrosion resistance of the filter cloth at high temperature.

[0099] It should be understood by those skilled in the art that the above discussion of any of the embodiments is merely exemplary and is not intended to suggest the scope of the present application (including the claims) is limited to these examples; under the concept of the present application, the above embodiments or technical features between different embodiments can also be combined, the steps can be implemented in any order, and there are many other changes of different aspects of the present application as described above. In order to be brief, they are not provided in details.

[0100] The present application is intended to cover all such alternatives, modifications and variations as fall within the broad scope of the appended claims. Accordingly, any and all such modifications, variations, omissions, etc. that do not depart from the spirit and scope of the present application are intended to be encompassed by the claims.

Claims

1. A filter cloth specifically for purification and extraction in hydrometallurgical processes, characterized in that, The raw materials include the following parts by weight: 30-45 parts homopolymer polypropylene, 15-21 parts copolymer polypropylene, 10-18 parts maleic anhydride grafted polypropylene, 3-9 parts modified carbon nanotubes, 3-5 parts polyvinylidene fluoride, and 0.2-0.4 parts antioxidant BHT. The synthesis steps of the modified carbon nanotubes are as follows: S1: Heat carbon nanotubes at 300-350°C for 3-5 hours, wash and dry them, then soak them in concentrated nitric acid with a mass concentration of 60-70% and heat them at 70-80°C for 3-5 hours. Then clean the surface with deionized water until the pH = 6.5-7, and dry them to obtain acid-treated carbon nanotubes. S2: Add acid-treated carbon nanotubes, cerium nitrate hexahydrate and phenanthroline to anhydrous ethanol, heat and stir at 50-60°C for 4-6 hours to obtain a mixed solution, then pour the mixed solution into a reaction vessel, heat at 100-110°C for 6-8 hours, and dry to obtain carbon nanotube-cerium-phenanthroline complex. S3: The carbon nanotube-cerium-phenanthroline complex is placed in a tube furnace for primary carbonization at 300-400℃ for 1-2 hours under N2 atmosphere. Then, the primary carbonized carbon nanotube-cerium-phenanthroline complex and potassium hydroxide are ground together for 2-4 hours to obtain a mixture. The mixture is then transferred to a tube furnace for secondary carbonization at 800-900℃ for 2-3 hours under N2 atmosphere. After washing and drying, modified carbon nanotubes are obtained.

2. The filter cloth for hydrometallurgical purification and extraction according to claim 1, characterized in that, The homopolymer polypropylene has a melt flow rate of 2.5-4 g / 10 min at 230°C and 2.16 kg load; the maleic anhydride-grafted polypropylene has a melt flow rate of 3-6 g / 10 min at 230°C and 2.16 kg load; and the polyvinylidene fluoride has a melt flow rate of 1-2 g / 10 min at 230°C and 2.16 kg load.

3. The filter cloth for hydrometallurgical purification and extraction according to claim 1, characterized in that, The copolymer polypropylene is an ethylene-propylene copolymer with a vinyl content of 3-4% in molar percentage and a melt flow rate of 5-8 g / 10 min under a load of 2.16 kg at 230 °C.

4. The filter cloth for hydrometallurgical purification and extraction according to claim 1, characterized in that, In step S1, the carbon nanotubes have a diameter of 10-20 nm and a length of 5-15 μm.

5. The filter cloth for hydrometallurgical purification and extraction according to claim 1, characterized in that, In step S2, the mass ratio of acid-treated carbon nanotubes, cerium nitrate hexahydrate, phenanthroline and anhydrous ethanol is 10:(1-4):(2-8):(50-70).

6. The filter cloth for hydrometallurgical purification and extraction according to claim 1, characterized in that, In step S3, the heating rate for the first carbonization is 3-5℃ / min, and the N2 flow rate is 1.5-2.5L / min; the heating rate for the second carbonization is 1-2℃ / min, the cooling rate for the second carbonization is 5-10℃ / min, and the N2 flow rate is 1.5-2.5L / min.

7. The filter cloth for hydrometallurgical purification and extraction according to claim 1, characterized in that, In step S3, the mass ratio of carbon nanotube-cerium-phenanthroline complex to potassium hydroxide is 10:(1-3).

8. The method for preparing the special filter cloth for hydrometallurgical purification and extraction according to any one of claims 1-7, characterized in that, Includes the following steps: S4: Homopolymer polypropylene, copolymer polypropylene, maleic anhydride-grafted polypropylene, modified carbon nanotubes, polyvinylidene fluoride and antioxidant BHT are mixed, heated and melted through a twin-screw extruder, and then the melt is extruded into a spinning box for spinning. The spun yarn is cooled and shaped to obtain a mesh. S5: After arranging the warp and weft threads of the mesh, the mesh is woven to obtain the filter cloth, which is then subjected to high temperature setting at 160-190℃. Then, the filter cloth is calendered at 130-150℃ and 10KPa pressure until the air permeability is 50-100L / m2 / s. Finally, it is electrostatically treated to obtain a special filter cloth for wet metallurgical purification and extraction.

9. The method for preparing the special filter cloth for hydrometallurgical purification and extraction according to claim 8, characterized in that, In step S4, the operating temperature of the twin-screw extruder is 160-180℃; the operating temperature of the spinning box is 160-170℃, and the operating pressure is 15-20MPa.

10. The method for preparing the special filter cloth for hydrometallurgical purification and extraction according to claim 8, characterized in that, In step S5, the warp diameter is 0.135-0.23mm, the weft diameter is 600-1500D, the warp density is 30-88 threads / cm, and the weft density is 12-23 threads / cm. The resulting filter cloth for wet metallurgical purification and extraction has an 8-harness twill weave.

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