A Pt-CuO-Fe3O4 composite catalyst based on potassium feldspar extraction residue and its preparation method and application

Abstract

The present invention provides a Pt-CuO-Fe3O4 composite catalyst based on potassium feldspar potassium extraction residue and its preparation method and application, the preparation method adds potassium extraction residue and copper salt of potassium feldspar to a surfactant solution in sequence to obtain A solution; iron salt is added to the A solution, stirred at room temperature for reaction, and dried and calcined to obtain a CuO-Fe3O4 / residue composite material; H2PtCl6 is added to the aqueous solution of the CuO-Fe3O4 / residue composite material, stirred and mixed to obtain a B solution, a mixed solution of NaOH and NaBH4 is added to the B solution, oscillated and reduced, and the product is dried and calcined to obtain the Pt-CuO-Fe3O4 composite catalyst based on potassium feldspar potassium extraction residue. The present invention utilizes potassium extraction residue as a catalyst carrier, effectively avoids the agglomeration of metal oxides, increases reactive sites, and the obtained composite catalyst has higher catalytic activity.

Description

Technical Field

[0001] The present invention belongs to the technical field of comprehensive resource utilization of potassium feldspar, and relates to a Pt-CuO-Fe3O4 composite catalyst based on potassium extraction residue from potassium feldspar, and a preparation method and application thereof. Background Art

[0002] Volatile organic compounds (VOCs) are important precursors of secondary organic aerosols and ozone in the atmosphere, and pose potential hazards to environmental quality and human health. Among them, toluene, as a typical aromatic VOCs pollutant, has a stable structure and a wide range of sources. Thermal catalytic oxidation technology is an effective way to eliminate toluene pollution from industrial sources. It can completely oxidize and degrade toluene at a certain temperature (about 200-400°C). Catalysts can significantly reduce the reaction temperature for complete oxidation of VOCs. Among them, transition metal oxides (copper, iron, etc.) have good thermal catalytic properties for toluene, but there is still a T 100 The problem of high temperature (the temperature required for 100% toluene conversion) is that it consumes a lot of energy. For example, Huang Yu et al. (Chinese invention patent, CN109985520B) prepared a porous CuO / CuFe2O4 catalyst with a toluene conversion rate of T 100 360℃; Zhu et al. (DD Zhu et al. Environ. Sci. Technol. 2023, 57(45), 17598–17609) developed a CuO-Fe3O4 composite material, which still has a high T 100 (320℃). Precious metals (Pt, Pd, etc.) have excellent thermal catalytic properties. Loading precious metals on transition metal oxides can effectively reduce the T 100 For example, Li et al. (LMLi et al.ACS Appl.NanoMater.2021,4(7),6637–6647) prepared Pt-modified Pt-CuMnO x Catalyst, its toluene conversion T 100 At 240℃, compared with CuMnO x decreased by 40℃, but after loading Pt, T 100 It is still relatively high and there is room for further reduction. The use of precious metals leads to high catalyst costs. How to further reduce T 100 and catalyst costs are still issues that need to be urgently addressed in the field of VOCs thermal catalysis.

[0003] In the field of thermal catalysis of VOCs, thermal catalytic inert materials are often used as carriers (such as silica, cordierite, palygorskite, etc.) to disperse and fix metal nanoparticles and enhance the stability of the catalyst. Usually, the metal dispersed by the carrier has more active sites. In addition, the use of the carrier reduces the amount of catalyst used and reduces costs. For example, Zhao Qiuna et al. (Zhao Qiuna et al. Acta Petrolei Sinica (Petroleum Processing), 2022, 38(05): 1052-1063.) loaded Co3O4 catalyst on silica nanospheres. Co3O4 is highly dispersed on the silica nanospheres. 100 Compared with unsupported Co3O4, the temperature is reduced to 280℃. More importantly, the actual amount of Co3O4 is greatly reduced. Zhu et al. (AMZhu et al. J. Rare Earths. 2018, 36(12), 1272-1277.) loaded Pt-CuMnCe on cordierite, and the amount of Pt-CuMnCe in the catalyst was reduced, but T 100 The temperature is 250℃, which is still relatively high, and the loading process is complicated, and cordierite needs acid treatment.

[0004] Potash feldspar is a potassium resource with abundant reserves in my country. Extracting potassium from potassium feldspar for use as potash fertilizer is an effective means of addressing my country's potash fertilizer shortage. Among current potassium extraction technologies, high-temperature pyrolysis has attracted widespread attention due to its simple operation, easy reaction control, and lack of strong alkali corrosion. However, high-temperature calcination methods for potassium extraction still face challenges such as low extraction efficiency, energy waste caused by excessively high calcination temperatures, high costs due to the use of large amounts of additives, and the inability to effectively utilize the extraction residue. For example, Wu Qiusheng et al. (Wu Qiusheng et al. Nonmetallic Minerals, 2019, 42(5): 24-27.) used limestone and dolomite as additives, and NaHCO3 and Fe2O3 as additives. When the calcination temperature was 1175℃ and the temperature was kept for 1 hour, the potassium extraction rate was 85%; Hu Tianxi et al. (Chinese invention patent, CN101831561A) mixed potassium feldspar, CaCl2, and NaCl after ball milling at a mass ratio of 10:10:5, and after calcination at 900℃ for 7 hours, the potassium extraction rate was 98.36%. The use of a large amount of additives and the high calcination temperature resulted in excessively high costs and energy consumption, and a low potassium extraction rate. Summary of the Invention

[0005] In view of the problems existing in the prior art, the present invention provides a Pt-CuO-Fe3O4 composite catalyst based on potassium feldspar extraction residue and its preparation method and application, thereby solving the problems of VOCs thermal catalytic oxidant T in the prior art. 100 The catalyst carrier preparation process is too high and the cost is complicated. At the same time, the present invention also solves the technical problems in the prior art that potassium feldspar residue cannot be effectively utilized and the high energy consumption of high-temperature pyrolysis method for potassium extraction is high.

[0006] The present invention is achieved through the following technical solutions:

[0007] A method for preparing a Pt-CuO-Fe3O4 composite catalyst based on potassium feldspar potassium extraction residue comprises the following steps:

[0008] S1: adding potassium extraction residue of potassium feldspar and copper salt to surfactant solution in sequence to obtain solution A;

[0009] S2: adding iron salt to the solution A, stirring the mixture at room temperature, and drying and calcining the mixture to obtain a CuO-Fe3O4 / residue composite material;

[0010] S3: Add H2PtCl6 to the suspension of the CuO-Fe3O4 / residue composite material, ultrasonically oscillate to obtain solution B, add a mixed solution of NaOH and NaBH4 to solution B, oscillate and reduce, dry and calcine the product to obtain the Pt-CuO-Fe3O4 composite catalyst based on potassium feldspar extraction residue.

[0011] Preferably, in step S1, the potassium extraction residue is obtained by mixing potassium feldspar, sodium salt and calcium salt, ball milling the mixture, and then calcining the mixture under an air atmosphere to obtain a solid product, and washing the solid product with water to obtain the potassium extraction residue.

[0012] Preferably, in step S1, during ball milling, the rotation speed is 200-600 r / min, the ball milling time is 0.5-4 h, the ball milling beads are a mixed system with particle sizes of 1 mm, 3 mm, 6 mm and 10 mm, and the mass ratio of the 1 mm, 3 mm, 6 mm and 10 mm ball milling beads is (1-5):(1-6):(4-10):(4-10).

[0013] Preferably, in step S1, the mass ratio of the surfactant to the potassium extraction residue is 1:(0.2-1), and the molar ratio of the surfactant to the copper salt is 1:(0.5-2).

[0014] Preferably, in step S2, the speed of adding the iron salt to the solution A is 5 to 15 mL / min.

[0015] Preferably, in step S2, the calcination temperature is 350-650°C, the calcination time is 1-4 hours, and the heating rate is 2-10°C.

[0016] Preferably, in step S3, the concentration of the suspension of the CuO-Fe3O4 / residue composite material is 50-500 g / L, the ultrasonic time is 10-60 min, and the oscillation time is 0.5-3 h.

[0017] Preferably, in step S3, the calcination temperature is 150-450° C., and the calcination time is 1-4 hours.

[0018] A Pt-CuO-Fe3O4 composite catalyst based on potassium feldspar potassium extraction residue is prepared by the above method.

[0019] The above-mentioned Pt-CuO-Fe3O4 composite catalyst based on potassium feldspar extraction residue is used in the field of VOCs thermal catalytic oxidation.

[0020] Compared with the prior art, the present invention has the following beneficial technical effects:

[0021] The present invention discloses a preparation method of a Pt-CuO-Fe3O4 composite catalyst based on potassium feldspar extraction residue. The potassium extraction residue is used as a substrate, and the Pt-CuO-Fe3O4 composite catalyst is loaded on the substrate. The potassium extraction residue contains a large amount of SiO2, as well as albite and anorthite. The SiO2 in the component can bond with the Fe3O4 in the catalytic active component to form Si-O-Fe bonds, thereby inhibiting the agglomeration of the catalytic active component and providing more reaction active sites. Compared with the case before the potassium feldspar residue is loaded, the T 100 At the same time, under the action of equal mass of Pt-CuO-Fe3O4 and Pt-CuO-Fe3O4 / residue catalysts, the T 100 Lower (220°C), less precious metals and transition metals are required, and the cost is lower. In addition, most of the currently used thermal catalytic inert carriers need to be modified by adding additives, strong acids, high temperatures and other conditions, and the preparation process is complicated and the cost is high. In the present invention, potassium feldspar residue is used directly as a carrier without additional treatment, and the comprehensive utilization of potassium feldspar is achieved. That is, the present invention uses the residue after potassium extraction as a carrier of the thermal catalyst, loading the Pt-CuO-Fe3O4 composite catalyst, on the one hand, utilizing the excellent thermal stability of potassium feldspar residue and the large amount of SiO2 in the component to provide more active sites and reduce T 100 To 220 ° C. At the same time, the residue is used as a carrier to promote the effective utilization of potassium extraction residues and reduce the use of metals, especially precious metals, in the catalyst material.

[0022] Furthermore, when extracting potassium feldspar residue, this method uses sodium salt and calcium salt as auxiliary agents, and the potassium feldspar and the auxiliary agents are ball-milled and then calcined. Ball milling helps the auxiliary agents and potassium feldspar to mix evenly, which promotes the Ca 2+ / Na + Entering the potassium feldspar lattice, replacing K +In this process, the combination of ball milling and high-temperature calcination improves the efficiency of potassium extraction while reducing the use of additives and lowering the calcination temperature, making the reaction cost lower and the reaction conditions milder. Compared with acid leaching, water is used to leach potassium ions, avoiding the generation of waste acid.

[0023] Furthermore, during ball milling, the rotation speed is 200-600 r / min and the ball milling time is 0.5-4 h, which can ensure sufficient grinding contact between potassium feldspar and the additive. The ball milling beads are a mixed system with particle sizes of 1 mm, 3 mm, 6 mm and 10 mm. The mass ratio of the 1 mm, 3 mm, 6 mm and 10 mm ball milling beads is (1-5): (1-6): (4-10): (4-10), which is conducive to further uniform mixing of the three and making more Ca 2+ and Na + Able to enter the potassium feldspar lattice and replace K + , which is beneficial to the extraction of potassium ions from potassium feldspar.

[0024] Furthermore, in step S1, the mass ratio of surfactant to potassium feldspar residue is 1:(0.2-1), and the molar ratio of surfactant to copper salt is 1:(0.5-2), which can prevent the surfactant micelles from Cu2+ and Cu2+ from being absorbed by the surfactant due to the steric effect. 2+ Coordinate with organic ligands to prevent the aggregation of Cu3[Fe(CN)6]2 crystal nuclei and control the particle size of the obtained composite catalyst.

[0025] Furthermore, in step S2, the iron salt is added to the solution A at a rate of 5 to 15 mL / min, which can slow down the growth rate of the Cu3[Fe(CN)6]2 crystal nuclei and effectively control the crystallinity of the Cu3[Fe(CN)6]2 crystals.

[0026] Furthermore, in step S3, the calcination temperature is 350-650°C, the calcination time is 1-4 hours, and the heating rate is 2-10°C, so that the residual carbon in the precursor CTAB can be calcined and Cu3[Fe(CN)6]2 can be reduced to form CuO-Fe3O4.

[0027] Furthermore, in step S3, the ultrasonic time is 10 to 60 minutes and the oscillation time is 0.5 to 3 hours, which can make the CuO-Fe3O4 and the residue fully dispersed in the aqueous solution, which is conducive to fully reducing H2PtCl6 to metallic Pt.

[0028] Furthermore, in step S3, the calcination temperature is 150-450°C and the calcination time is 1-4 hours, so that the metal oxide partially reduced by NaBH4 can be reformed into CuO-Fe3O4, and finally a Pt-CuO-Fe3O4 / residue composite catalyst is obtained. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments. It should be understood that the following drawings only illustrate certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other relevant drawings can be obtained based on these drawings without paying any creative work.

[0030] Figure 1 Schematic diagram of a process for preparing a Pt-CuO-Fe3O4 composite catalyst based on potassium feldspar extraction residue in the present invention;

[0031] Figure 2 is the XRD pattern of potassium feldspar used in the present invention;

[0032] Figure 3 is the XRD pattern of the potassium feldspar residue after water washing in the present invention;

[0033] Figure 4 The SEM and EDS images of the potassium feldspar residue in the present invention are shown;

[0034] Figure 5 is the XRD pattern of Pt-CuO-Fe3O4 (Comparative Example 4) in the present invention;

[0035] Figure 6 This is the Pt 4d XPS fine spectrum of Pt-CuO-Fe3O4 (Comparative Example 4) in the present invention;

[0036] Figure 7 Graph showing the toluene conversion and CO2 yield of Pt-CuO-Fe3O4 / residue (sample in Example 1) and Pt-CuO-Fe3O4 (Comparative Example 4). DETAILED DESCRIPTION

[0037] To facilitate understanding of the features and effects of the present invention by those skilled in the art, the following provides a general description and definition of the terms and expressions used in the specification and claims. Unless otherwise indicated, all technical and scientific terms used herein have the ordinary meanings as understood by those skilled in the art regarding the present invention. In the event of conflict, the definitions in this specification shall prevail.

[0038] The theories or mechanisms described and disclosed herein, whether correct or incorrect, should not limit the scope of the present invention in any way, that is, the present invention can be implemented without being limited by any specific theory or mechanism.

[0039] Herein, all features such as values, amounts, amounts, and concentrations defined in numerical ranges or percentage ranges are for brevity and convenience only. Accordingly, the description of numerical ranges or percentage ranges should be considered to include and specifically disclose all possible subranges and individual values ​​within the range (including integers and fractions).

[0040] In this document, unless otherwise specified, “include,” “including,” “contains,” “has” or similar terms cover the meanings of “consisting of” and “mainly consisting of,” for example, “A includes a” covers the meanings of “A includes a and other” and “A only includes a.”

[0041] In this document, for the sake of brevity, not all possible combinations of the various technical features in each embodiment or example are described. Therefore, as long as there are no contradictions in the combination of these technical features, the various technical features in each embodiment or example can be combined in any way, and all possible combinations should be considered to be within the scope of this specification.

[0042] like Figure 1 As shown, the present invention provides a method for preparing a Pt-CuO-Fe3O4 composite catalyst based on potassium feldspar potassium extraction residue, comprising the following steps:

[0043] S1: Potassium feldspar, calcium salt and sodium salt are ball-milled and mixed in a certain proportion, and then calcined in a muffle furnace under air atmosphere. The obtained solid product is washed with water for 2 hours and then vacuum filtered to obtain a soluble potassium ion solution and a potassium extraction residue. The acquisition of the soluble potassium ion solution in this process effectively realizes the extraction of potassium from the insoluble potassium feldspar, and the obtained potassium extraction residue can be used as a carrier substrate for the subsequent preparation of catalysts.

[0044] Among them, the mass ratio of potassium feldspar, sodium salt and calcium salt is 1: (0.1 ~ 0.6): (0.1 ~ 0.7), which can make different ratios of Ca 2+ and Na + Can synergistically promote K + During ball milling, the rotation speed is 200-600 r / min, the ball milling time is 0.5-4 h, and the ball milling beads are a mixed system with particle sizes of 1 mm, 3 mm, 6 mm and 10 mm. The mass ratio of the 1 mm, 3 mm, 6 mm and 10 mm ball milling beads is (1-5): (1-6): (4-10): (4-10), which is conducive to further mixing of the three and making more Ca 2+ and Na + Able to enter the potassium feldspar lattice and replace K +, which is beneficial for extracting potassium ions from potassium feldspar. In this step, the calcination temperature in an air atmosphere is 650-950°C, the calcination time is 0.5-3 hours, and the heating rate is 2-10°C / min. This can increase the reactivity of the potassium feldspar and improve the potassium extraction efficiency. The ball mill beads used in the present invention are agate beads.

[0045] The sodium salt is any one of NaCl, Na2CO3, Na2SO4, NaNO3 and NaHCO3, and the calcium salt is any one of CaCl2·2H2O, CaBr2·2H2O, Ca(NO3)2 and Ca(HCO3)2.

[0046] S2: Pre-dissolve a surfactant with a mass concentration of 800-1200 g / L to form surfactant micelles, add potassium extraction residue and copper salt in sequence, and stir evenly; add Fe4[Fe(CN)6]3 or K3Fe(CN)6 solution with a molar concentration of 0.01-0.08 mol / L to the above solution at a rate of 5-15 mL / min, stir continuously for 8-24 h at room temperature, centrifuge, wash, and dry, and then calcine in air atmosphere at a calcination temperature of 350-650°C, a calcination time of 1-4 h, and a heating rate of 2-10°C / min to obtain a CuO-Fe3O4 / residue complex; add 1-6 mL of 2 mg / mL H2PtCl6 solution to a suspension of 50-500 g / L CuO-Fe3O4 / residue complex, ultrasonicate for 10-60 min, then oscillate for 0.5-3 h, and add 1-5 mL of The catalyst is reduced with NaOH / NaBH4, centrifuged, washed, dried, and then calcined in an air atmosphere at a temperature of 150-450°C for 1-4 hours to obtain a Pt-CuO-Fe3O4 / residue catalyst, i.e., a Pt-CuO-Fe3O4 composite catalyst based on potassium feldspar extraction residue.

[0047] The surfactant is cetylpyridinium chloride (CPC) or cetyltrimethylammonium bromide (CTAB), the mass ratio of the surfactant to the potassium extraction residue is 1:(0.2-1), and the molar ratio of the surfactant to the copper salt is 1:(0.5-2).

[0048] Wherein, the copper salt is any one of CuCl2·2H2O, CuNO3·3H2O, Cu(CH3COO)2·H2O and CuSO4·5H2O.

[0049] In this step, the concentration of the surfactant is 800-1200 g / L, which can prevent the surfactant micelles from blocking the Cu 2+ Coordinated with organic ligands.

[0050] The molar concentration of the iron salt is 0.01 to 0.08 mol / L, which can effectively control the crystallinity of the formed Cu3[Fe(CN)6]2 precursor.

[0051] The iron salt addition rate is 5 to 15 mL / min, and the continuous stirring time is 8 to 24 h, which can slow down the growth rate of Cu3[Fe(CN)6]2 crystal nuclei and effectively control the crystallinity of Cu3[Fe(CN)6]2.

[0052] In addition, when adding the mixed solution of NaOH and NaBH4, a dropwise addition method is adopted, with a specific dropwise addition speed of 2 to 10 mL / min and an oscillation reduction time of 10 to 40 min, which can fully reduce H2PtCl6 to metallic Pt to form a Pt-CuO-Fe3O4 / residue composite catalyst.

[0053] The present invention discloses a method for preparing a Pt-CuO-Fe3O4 composite catalyst based on potassium feldspar extraction residue, achieving comprehensive utilization of the potassium extraction residue from potassium feldspar. This method involves ball-milling potassium feldspar, calcium salt, and sodium salt in a specific proportion to uniformly mix them, calcining them in a muffle furnace under an air atmosphere, and washing the resulting solid product with water and vacuum filtration to obtain soluble potassium ions. The potassium feldspar residue is used as a carrier to load the Pt-CuO-Fe3O4 catalyst, improving its dispersibility and increasing reactive sites, resulting in excellent catalytic performance for toluene oxidation.

[0054] The method of the present invention is to ball-mill the potassium extraction residue of potassium feldspar and the auxiliary agent and then calcine, which helps to mix the auxiliary agent and potassium feldspar evenly and promotes the Ca 2+ / Na + Entering the potassium feldspar lattice, replacing K + In the process of potassium extraction, the process is simple, the amount of additives added is small, the cost is lower, the reaction conditions are mild, and the potassium extraction efficiency is higher. Using the residue as a carrier of the Pt-CuO-Fe3O4 catalyst effectively avoids the agglomeration of metal oxides and increases the number of reaction active sites. Compared with Pt-CuO-Fe3O4, the T of Pt-CuO-Fe3O4 / residue is 100 Reducing the temperature by 40°C is beneficial to saving energy consumption and has good application prospects; the more active Pt-CuO-Fe3O4 / residue catalyst uses less precious metals and transition metals, has lower costs, and is conducive to further promotion and use; the potassium extraction technology of ball milling followed by calcination proposed in the present invention has a higher potassium extraction rate when using less additives and a lower calcination temperature, and uses the potassium extraction residue as a Pt-CuO-Fe3O4 carrier to achieve the comprehensive utilization of potassium feldspar.

[0055] Below in conjunction with specific embodiment, further set forth the present invention.Should be understood that these embodiments are only used to illustrate the present invention and are not used in limiting the scope of the present invention.In addition, should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms fall equally within the scope limited by the appended claims of the application.

[0056] The following examples were prepared using conventional instruments and equipment in the art. Experimental methods in the following examples, where specific conditions are not specified, were generally performed under conventional conditions or according to the conditions recommended by the manufacturer. The various raw materials used in the following examples, unless otherwise specified, were conventional commercially available products, with specifications conventional in the art. In the present specification and the following examples, unless otherwise specified, "%" indicates percentage by weight, "part" indicates parts by weight, and "ratio" indicates weight ratio.

[0057] Example 1

[0058] A method for preparing a Pt-CuO-Fe3O4 composite catalyst based on potassium feldspar potassium extraction residue comprises the following steps:

[0059] S1: Potash feldspar, CaCl2·2H2O and NaCl are mixed in a mass ratio of 1:0.4:0.6 and ball-milled uniformly. During ball milling, the speed is 400 r / min, the ball milling time is 0.5 h, the ball milling beads are a mixed system with particle sizes of 1 mm, 3 mm, 6 mm and 10 mm, and the mass ratio of the 1 mm, 3 mm, 6 mm and 10 mm ball milling beads is 2:1:5:5. The mixture is then placed in a muffle furnace and calcined at 850°C in an air atmosphere for 1 h at a heating rate of 2°C / min. The resulting solid product is washed with water for 2 h and then vacuum filtered to obtain a soluble potassium ion solution and a potassium extraction residue.

[0060] S2: A surfactant with a mass concentration of 1200 g / L was pre-dissolved to form surfactant micelles, and potassium extraction residue and CuNO3·3H2O were added successively and stirred evenly; a Fe4[Fe(CN)6]3 solution with a molar concentration of 0.08 mol / L was added dropwise to the above solution at a rate of 5 mL / min, and the mixture was stirred continuously for 8 h at room temperature, centrifuged, washed, and dried, and then calcined in air atmosphere at a calcination temperature of 350°C, a calcination time of 4 h, and a heating rate of 2°C / min to obtain CuO-Fe3O4 / residue; 1 mL of 2 mg / mL H2PtCl6 solution was added to a suspension of 50 g / L CuO-Fe3O4 / residue complex, ultrasonicated for 10 min, then oscillated for 0.5 h, and 1 mL of The catalyst was reduced by oscillation with NaOH / NaBH4 for 15 min, centrifuged, washed, dried, and then calcined in air at 150°C for 1 h to obtain a Pt-CuO-Fe3O4 / residue composite catalyst.

[0061] The surfactant is cetyltrimethylammonium bromide (CTAB), the mass ratio of the surfactant to the potassium extraction residue is 1:0.4, and the molar ratio of the surfactant to CuNO3·3H2O is 1:1.

[0062] Example 2

[0063] A method for preparing a Pt-CuO-Fe3O4 composite catalyst based on potassium feldspar potassium extraction residue comprises the following steps:

[0064] S1: Potash feldspar, CaCl2·2H2O and NaCl are mixed in a mass ratio of 1:0.1:0.7 and ball-milled uniformly. During ball milling, the speed is 200 r / min, the ball milling time is 1 h, the ball milling beads are a mixed system with particle sizes of 1 mm, 3 mm, 6 mm and 10 mm, and the mass ratio of the 1 mm, 3 mm, 6 mm and 10 mm ball milling beads is 1:6:10:10. Then, the mixture is placed in a muffle furnace and calcined at 650°C in an air atmosphere for 2 h at a heating rate of 5°C / min. The obtained solid product is washed with water for 2 h and then vacuum filtered to obtain a soluble potassium ion solution and a potassium extraction residue.

[0065] S2: A surfactant with a mass concentration of 800 g / L was pre-dissolved to form surfactant micelles, and potassium extraction residue and CuCl2·2H2O were added successively and stirred evenly; a K3Fe(CN)6 solution with a molar concentration of 0.05 mol / L was added dropwise to the above solution at a rate of 15 mL / min, and the mixture was continuously stirred for 16 h at room temperature, centrifuged, washed, and dried, and then calcined in air atmosphere at a calcination temperature of 450°C, a calcination time of 2.5 h, and a heating rate of 5°C / min to obtain CuO-Fe3O4 / residue; 2 mL of 2 mg / mL H2PtCl6 solution was added to a suspension of 100 g / L CuO-Fe3O4 / residue complex, ultrasonicated for 30 min, then oscillated for 3 h, and 2 mL of The catalyst was reduced by oscillation with NaOH / NaBH4 for 10 min, centrifuged, washed, dried, and then calcined in air at a temperature of 200°C for 2 h to obtain a Pt-CuO-Fe3O4 / residue composite catalyst.

[0066] The surfactant is cetylpyridinium chloride (CPC), the mass ratio of the surfactant to the potassium extraction residue is 1:0.8, and the molar ratio of the surfactant to CuCl2·2H2O is 1:1.5.

[0067] Example 3

[0068] A method for preparing a Pt-CuO-Fe3O4 composite catalyst based on potassium feldspar potassium extraction residue comprises the following steps:

[0069] S1: Potash feldspar, CaCl2·2H2O and Na2CO3 are mixed in a mass ratio of 1:0.6:0.1 and ball-milled uniformly. During ball milling, the rotation speed is 600 r / min, the ball milling time is 3 h, the ball milling beads are a mixed system with particle sizes of 1 mm, 3 mm, 6 mm and 10 mm, and the mass ratio of the 1 mm, 3 mm, 6 mm and 10 mm ball milling beads is 5:6:10:10. Then, the mixture is placed in a muffle furnace and calcined at 950°C in an air atmosphere for 3 h at a heating rate of 10°C / min. The obtained solid product is washed with water for 2 h and then vacuum filtered to obtain a soluble potassium ion solution and a potassium extraction residue.

[0070] S2: A surfactant with a mass concentration of 900 g / L was pre-dissolved to form surfactant micelles, and potassium extraction residue and CuSO4·5H2O were added successively and stirred evenly; a K3Fe(CN)6 solution with a molar concentration of 0.01 mol / L was added dropwise to the above solution at a rate of 8 mL / min, and the mixture was continuously stirred for 10 h at room temperature, centrifuged, washed, and dried, and then calcined in air atmosphere at a calcination temperature of 550°C, a calcination time of 1 h, and a heating rate of 10°C / min to obtain CuO-Fe3O4 / residue; 2 mL of 2 mg / mL H2PtCl6 solution was added to a suspension of 200 g / L CuO-Fe3O4 / residue complex, ultrasonicated for 40 min, then oscillated for 2 h, and 3 mL of The catalyst was reduced by oscillation with NaOH / NaBH4 for 20 min, centrifuged, washed, dried, and then calcined in air at a temperature of 300°C for 2 h to obtain a Pt-CuO-Fe3O4 / residue composite catalyst.

[0071] The surfactant is CTAB, the mass ratio of the surfactant to the potassium extraction residue is 1:0.2, and the molar ratio of the surfactant to CuSO4·5H2O is 1:0.5.

[0072] Example 4

[0073] A method for preparing a Pt-CuO-Fe3O4 composite catalyst based on potassium feldspar potassium extraction residue comprises the following steps:

[0074] S1: Potash feldspar, CaBr2·2H2O and NaHCO3 are mixed in a mass ratio of 1:0.5:0.5 and ball-milled uniformly. During ball milling, the rotation speed is 500 r / min, the ball milling time is 4 h, the ball milling beads are a mixed system with particle sizes of 1 mm, 3 mm, 6 mm and 10 mm, and the mass ratio of the 1 mm, 3 mm, 6 mm and 10 mm ball milling beads is 1:1:10:10. Then, the mixture is placed in a muffle furnace and calcined at 800°C in an air atmosphere for 2.5 h at a heating rate of 5°C / min. The obtained solid product is washed with water for 2 h and vacuum filtered to obtain a soluble potassium ion solution and a potassium extraction residue.

[0075] S2: A surfactant with a mass concentration of 1000 g / L was pre-dissolved to form surfactant micelles, and potassium extraction residue and CuCl2·2H2O were added successively and stirred evenly; Fe4[Fe(CN)6]3 solution with a molar concentration of 0.06 mol / L was added dropwise to the above solution at a rate of 10 mL / min, and the mixture was continuously stirred at room temperature for 24 h, centrifuged, washed, and dried, and then calcined in air atmosphere at a calcination temperature of 650°C, a calcination time of 3 h, and a heating rate of 10°C / min to obtain CuO-Fe3O4 / residue; 6 mL of 2 mg / mL H2PtCl6 solution was added to a suspension of 500 g / L CuO-Fe3O4 / residue complex, ultrasonicated for 60 min, and then oscillated for 3 h, and 5 mL of The catalyst was reduced by oscillation with NaOH / NaBH4 for 30 min, centrifuged, washed, dried, and then calcined in air at a temperature of 450°C for 1 h to obtain a Pt-CuO-Fe3O4 / residue composite catalyst.

[0076] The surfactant is CPC, the mass ratio of the surfactant to the potassium extraction residue is 1:1, and the molar ratio of the surfactant to CuCl2·2H2O is 1:2.

[0077] Example 5

[0078] A method for preparing a Pt-CuO-Fe3O4 composite catalyst based on potassium feldspar potassium extraction residue comprises the following steps:

[0079] S1: Potash feldspar, Ca(HCO3)2 and NaHCO3 are mixed in a mass ratio of 1:0.6:0.7 and ball-milled evenly. During ball milling, the rotation speed is 300r / min, the ball milling time is 0.5h, the ball milling beads are a mixed system with particle sizes of 1mm, 3mm, 6mm and 10mm, and the mass ratio of the 1mm, 3mm, 6mm and 10mm ball milling beads is 1:1:4:10. Then, the mixture is placed in a muffle furnace and calcined at 750°C in an air atmosphere for 3h with a heating rate of 10°C / min. The obtained solid product is washed with water for 2h and then vacuum filtered to obtain a soluble potassium ion solution and a potassium extraction residue.

[0080] S2: A surfactant with a mass concentration of 1100 g / L was pre-dissolved to form surfactant micelles, and potassium extraction residue and CuSO4·5H2O were added successively and stirred evenly; a K3Fe(CN)6 solution with a molar concentration of 0.04 mol / L was added dropwise to the above solution at a rate of 6 mL / min, and the mixture was stirred continuously for 20 h at room temperature, centrifuged, washed, and dried, and then calcined in an air atmosphere at a calcination temperature of 400°C, a calcination time of 3 h, and a heating rate of 5°C / min to obtain CuO-Fe3O4 / residue; 5 mL of 2 mg / mL H2PtCl6 solution was added to a suspension of 300 g / L CuO-Fe3O4 / residue complex, ultrasonicated for 30 min, and then oscillated for 1 h, and 2 mL of The catalyst was reduced by oscillation with NaOH / NaBH4 for 40 min, centrifuged, washed, dried, and then calcined in air at a temperature of 200°C for 4 h to obtain a Pt-CuO-Fe3O4 / residue composite catalyst.

[0081] The surfactant is CTAB, the mass ratio of the surfactant to the potassium extraction residue is 1:1, and the molar ratio of the surfactant to CuSO4·5H2O is 1:2.

[0082] Example 6

[0083] A method for preparing a Pt-CuO-Fe3O4 composite catalyst based on potassium feldspar potassium extraction residue comprises the following steps:

[0084] S1: Potash feldspar, CaCl2·2H2O and NaCl are mixed in a mass ratio of 1:0.1:0.1 and ball-milled uniformly. During ball milling, the rotation speed is 200 r / min, the ball milling time is 0.5 h, the ball milling beads are a mixed system with particle sizes of 1 mm, 3 mm, 6 mm and 10 mm, and the mass ratio of the 1 mm, 3 mm, 6 mm and 10 mm ball milling beads is 1:1:4:4. The mixture is then placed in a muffle furnace and calcined at 650°C in an air atmosphere for 0.5 h with a heating rate of 2°C / min. The obtained solid product is washed with water for 2 h and then vacuum filtered to obtain a soluble potassium ion solution and a potassium extraction residue.

[0085] S2: A surfactant with a mass concentration of 800 g / L was pre-dissolved to form surfactant micelles, and potassium extraction residue and CuCl2·2H2O were added successively and stirred evenly; a K3Fe(CN)6 solution with a molar concentration of 0.01 mol / L was added dropwise to the above solution at a rate of 5 mL / min, and the mixture was continuously stirred at room temperature for 8 h, centrifuged, washed, and dried, and then calcined in air atmosphere at a calcination temperature of 350°C, a calcination time of 4 h, and a heating rate of 2°C / min to obtain a CuO-Fe3O4 / residue complex; 1 mL of 2 mg / mL H2PtCl6 solution was added to a suspension of 50 g / L CuO-Fe3O4 / residue complex, ultrasonicated for 10 min, then oscillated for 0.5 h, and 1 mL of The catalyst was reduced by oscillation with NaOH / NaBH4 for 10 min, centrifuged, washed, dried, and then calcined in air at a temperature of 150°C for 4 h to obtain a Pt-CuO-Fe3O4 / residue composite catalyst.

[0086] The surfactant is cetylpyridinium chloride (CPC), the mass ratio of the surfactant to the potassium extraction residue is 1:0.2, and the molar ratio of the surfactant to CuCl2·2H2O is 1:0.5.

[0087] Example 7

[0088] A method for preparing a Pt-CuO-Fe3O4 composite catalyst based on potassium feldspar potassium extraction residue comprises the following steps:

[0089] S1: Potash feldspar, CaBr2·2H2O and Na2CO3 are mixed in a mass ratio of 1:0.3:0.3 and ball-milled uniformly. During ball milling, the rotation speed is 400 r / min, the ball milling time is 2 h, the ball milling beads are a mixed system with particle sizes of 1 mm, 3 mm, 6 mm and 10 mm, and the mass ratio of the 1 mm, 3 mm, 6 mm and 10 mm ball milling beads is 2:1:5:5. Then, the mixture is placed in a muffle furnace and calcined at 700°C in an air atmosphere for 2 h at a heating rate of 5°C / min. The obtained solid product is washed with water for 2 h and vacuum filtered to obtain a soluble potassium ion solution and a potassium extraction residue.

[0090] S2: A surfactant with a mass concentration of 1000 g / L was pre-dissolved to form surfactant micelles, and potassium extraction residue and CuNO3·3H2O were added successively and stirred evenly; a K3Fe(CN)6 solution with a molar concentration of 0.05 mol / L was added dropwise to the above solution at a rate of 6 mL / min, and the mixture was stirred continuously for 10 h at room temperature, centrifuged, washed, and dried, and then calcined in an air atmosphere at a calcination temperature of 400 ° C, a calcination time of 2 h, and a heating rate of 5 ° C / min to obtain a CuO-Fe3O4 / residue complex; 5 mL of 2 mg / mL H2PtCl6 solution was added to a suspension of 100 g / L CuO-Fe3O4 / residue complex, ultrasonicated for 20 min, and then oscillated for 2 h, and 2 mL of The catalyst was reduced by oscillation with NaOH / NaBH4 for 20 min, centrifuged, washed, dried, and then calcined in air at 250°C for 2 h to obtain a Pt-CuO-Fe3O4 / residue composite catalyst.

[0091] The surfactant is cetyltrimethylammonium bromide (CTAB), the mass ratio of the surfactant to the potassium extraction residue is 1:0.5, and the molar ratio of the surfactant to CuNO3·3H2O is 1:1.5.

[0092] Example 8

[0093] A method for preparing a Pt-CuO-Fe3O4 composite catalyst based on potassium feldspar potassium extraction residue comprises the following steps:

[0094] S1: Potash feldspar, Ca(NO3)2 and Na2SO4 are mixed in a mass ratio of 1:0.5:0.6 and ball-milled uniformly. During ball milling, the rotation speed is 600r / min, the ball milling time is 3h, the ball milling beads are a mixed system with particle sizes of 1mm, 3mm, 6mm and 10mm, and the mass ratio of the 1mm, 3mm, 6mm and 10mm ball milling beads is 4:3:6:5. Then, the mixture is placed in a muffle furnace and calcined at 900°C in an air atmosphere for 2h with a heating rate of 8°C / min. The obtained solid product is washed with water for 2h and then vacuum filtered to obtain a soluble potassium ion solution and a potassium extraction residue.

[0095] S2: A surfactant with a mass concentration of 1000 g / L was pre-dissolved to form surfactant micelles, and potassium extraction residue and Cu(CH3COO)2·H2O were added successively and stirred evenly; a Fe4[Fe(CN)6]3 solution with a molar concentration of 0.06 mol / L was added dropwise to the above solution at a rate of 10 mL / min, and the mixture was continuously stirred at room temperature for 20 h, centrifuged, washed, and dried, and then calcined in air atmosphere at a calcination temperature of 600 ° C, a calcination time of 3 h, and a heating rate of 8 ° C / min to obtain a CuO-Fe3O4 / residue complex; 5 mL of 2 mg / mL H2PtCl6 solution was added to a suspension of 300 g / L CuO-Fe3O4 / residue complex, ultrasonicated for 50 min, and then oscillated for 3 h, and 2 mL of The catalyst was reduced by oscillation with NaOH / NaBH4 for 30 min, centrifuged, washed, dried, and then calcined in air at a temperature of 350°C for 3 h to obtain a Pt-CuO-Fe3O4 / residue composite catalyst.

[0096] The surfactant is cetylpyridinium chloride (CPC), the mass ratio of the surfactant to the potassium extraction residue is 1:1, and the molar ratio of the surfactant to Cu(CH3COO)2·H2O is 1:1.

[0097] Example 9

[0098] A method for preparing a Pt-CuO-Fe3O4 composite catalyst based on potassium feldspar potassium extraction residue comprises the following steps:

[0099] S1: Potash feldspar, Ca(HCO3)2 and NaHCO3 are mixed in a mass ratio of 1:0.6:0.7 and ball-milled uniformly. During ball milling, the rotation speed is 600 r / min, the ball milling time is 0.5 h, the ball milling beads are a mixed system with particle sizes of 1 mm, 3 mm, 6 mm and 10 mm, and the mass ratio of the 1 mm, 3 mm, 6 mm and 10 mm ball milling beads is 5:6:10:9. Then, the mixture is placed in a muffle furnace and calcined at 950°C in an air atmosphere for 0.5 h. The heating rate during the process is 10°C / min. The obtained solid product is washed with water for 2 h and then vacuum filtered to obtain a soluble potassium ion solution and a potassium extraction residue.

[0100] S2: A surfactant with a mass concentration of 1200 g / L was pre-dissolved to form surfactant micelles, and potassium extraction residue and CuSO4·5H2O were added successively and stirred evenly; a K3Fe(CN)6 solution with a molar concentration of 0.08 mol / L was added dropwise to the above solution at a rate of 15 mL / min, and the mixture was continuously stirred at room temperature for 24 h, centrifuged, washed, and dried, and then calcined in an air atmosphere at a calcination temperature of 650°C, a calcination time of 1 h, and a heating rate of 9°C / min to obtain a CuO-Fe3O4 / residue complex; 6 mL of a 2 mg / mL H2PtCl6 solution was added to a 500 g / L suspension of the CuO-Fe3O4 / residue complex, ultrasonicated for 60 min, and then oscillated for 3 h, and 1 mL of The catalyst was reduced by oscillation with NaOH / NaBH4 for 40 min, centrifuged, washed, dried, and then calcined in air at a temperature of 450°C for 1 h to obtain a Pt-CuO-Fe3O4 / residue composite catalyst.

[0101] The surfactant is cetyltrimethylammonium bromide (CTAB), the mass ratio of the surfactant to the potassium extraction residue is 1:1, and the molar ratio of the surfactant to CuSO4·5H2O is 1:2.

[0102] Comparative Example 1

[0103] The difference from Example 1 is that a single auxiliary agent (calcium salt) is used. Specifically:

[0104] S1: Potash feldspar and CaCl2·2H2O are mixed in a mass ratio of 1:0.4 and ball-milled uniformly. During ball milling, the rotation speed is 400 r / min, the ball milling time is 0.5 h, the ball milling beads are a mixed system with particle sizes of 1 mm, 3 mm, 6 mm and 10 mm, and the mass ratio of the 1 mm, 3 mm, 6 mm and 10 mm ball milling beads is 2:1:5:5. The mixture is then placed in a muffle furnace and calcined at 850°C in an air atmosphere for 1 h at a heating rate of 2°C / min. The resulting solid product is washed with water for 2 h and then vacuum filtered to obtain a soluble potassium ion solution and a potassium extraction residue.

[0105] Comparative Example 2

[0106] The difference from Example 1 is that a single auxiliary agent (sodium salt) is used. Specifically:

[0107] S1: Potash feldspar and NaCl are mixed in a mass ratio of 1:0.6 and ball-milled uniformly. During ball milling, the rotation speed is 400 r / min, the ball milling time is 0.5 h, the ball milling beads are a mixed system with particle sizes of 1 mm, 3 mm, 6 mm and 10 mm, and the mass ratio of the 1 mm, 3 mm, 6 mm and 10 mm ball milling beads is 2:1:5:5. Then, the mixture is placed in a muffle furnace and calcined at 850°C in an air atmosphere for 1 h. The heating rate during the process is 2°C / min. The obtained solid product is washed with water for 2 h and then vacuum filtered to obtain a soluble potassium ion solution and a potassium extraction residue.

[0108] Comparative Example 3

[0109] The difference from Example 1 is that ball milling is not used, and the mixture is directly calcined. Specifically:

[0110] S1: Potash feldspar, CaCl2·2H2O, and NaCl were stirred and uniformly mixed in a mass ratio of 1:0.4:0.6, and then calcined in a muffle furnace at 850°C in air atmosphere for 1 h at a heating rate of 2°C / min. The resulting solid product was washed with water for 2 h and then vacuum filtered to obtain a soluble potassium ion solution and a potassium extraction residue.

[0111] Comparative Example 4

[0112] The difference from Example 1 is that the potassium extraction residue is not used as a carrier, and the catalyst is prepared directly. Specifically:

[0113] A surfactant with a mass concentration of 1200 g / L was pre-dissolved to form surfactant micelles, and CuNO3·3H2O was added and stirred uniformly; a Fe4[Fe(CN)6]3 solution with a molar concentration of 0.08 mol / L was added dropwise to the above solution at a rate of 5 mL / min, and the mixture was continuously stirred at room temperature for 8 hours, centrifuged, washed, and dried. The mixture was then calcined in an air atmosphere at a temperature of 350°C, a calcination time of 4 hours, and a heating rate of 2°C / min to obtain CuO-Fe3O4; 1 mL of 2 mg / mL H2PtCl6 solution was added to a 50 g / L CuO-Fe3O4 suspension, ultrasonicated for 10 minutes, and then oscillated for 0.5 hours. 1 mL of NaOH / NaBH4 was added at a dropwise rate of 2 mL / min and oscillated for reduction for 15 minutes. The mixture was centrifuged, washed, and dried, and then calcined in an air atmosphere at a temperature of 150°C and a calcination time of 1 hour to obtain a Pt-CuO-Fe3O4 catalyst.

[0114] The surfactant is cetyltrimethylammonium bromide (CTAB), and the molar ratio of the surfactant to CuNO3·3H2O is 1:1.

[0115] Potassium extraction rate and toluene conversion T in the examples and comparative examples 100The experimental results are shown in Table 1. As shown in Table 1, compared with a single additive (calcium salt or sodium salt), the dual additive has a higher potassium extraction rate; in addition, calcination after ball milling helps to further extract potassium, because ball milling can further mix potassium feldspar, calcium salt and sodium salt, which helps Ca 2+ and Na + Entering into potassium feldspar, replacing K + As shown in Table 2, the potassium extraction residue in the present invention contains a large amount of SiO2, with a content greater than 50%, which can form a Si-O-Fe bond with Fe3O4 in the catalytic active component, thereby inhibiting the agglomeration of the catalytic active component and providing more reactive sites. Compared with the potassium feldspar residue before loading, the T 100 .

[0116] Figure 2 and Figure 3 The XRD patterns of potassium feldspar and the residue after high-temperature pyrolysis and potassium extraction are shown. It can be seen that potassium feldspar mainly consists of potassium feldspar, SiO2, and albite. The residue after high-temperature pyrolysis and potassium extraction mainly consists of SiO2, albite, and anorthite. A comparison shows that the diffraction peak intensity attributable to potassium feldspar in the residue has decreased significantly, indicating that high-temperature calcination causes the potassium ions in the potassium feldspar to dissolve, destroying its structure.

[0117] Figure 4 The SEM and EDS images of the potassium feldspar residue show that the residue still presents an irregular block structure with raised particles on the surface. Secondly, after potassium extraction, the K content in the potassium feldspar residue is significantly reduced.

[0118] Figure 5 The XRD pattern of Pt-CuO-Fe3O4 shows that Fe3O4 and CuO coexist in Pt-CuO-Fe3O4, but no Pt diffraction peak is observed, which is mainly due to the low Pt loading;

[0119] Figure 6 The Pt 4d XPS fine spectrum of Pt-CuO-Fe3O4 shows that the Pt 4d peak can be divided into two convolution peaks, corresponding to the Pt at 315eV. 0 and Pt at 317.3 eV δ+ , proving the existence of Pt in Pt-CuO-Fe3O4. At the same time, the material has a high concentration of Pt δ+ , which can promote the adsorption and activation of toluene on the catalyst, thereby improving the conversion rate of toluene.

[0120] Figure 7The toluene conversion rate (a) and CO2 yield rate (b) of Pt-CuO-Fe3O4 / residue composite catalyst (Example 1) and Pt-CuO-Fe3O4 (Comparative Example 4) are shown in the figure. As can be seen from the figure, the toluene conversion rate T of Pt-CuO-Fe3O4 / residue is 100 At 220℃, the toluene conversion T of Pt-CuO-Fe3O4 100 Close to 260℃, therefore, when adding the same mass of catalyst, Pt-CuO-Fe3O4 / residue has a lower T 100 (220℃). For catalysts of the same mass, the amount of core catalyst (Pt-CuO-Fe3O4) used is less because Pt-CuO-Fe3O4 / residue contains residue. Therefore, the toluene complete conversion temperature of the Pt-CuO-Fe3O4 / residue composite catalyst is lower, and it has better toluene thermal catalytic performance.

[0121] Table 1 Potassium extraction rate and toluene conversion T in the embodiment 100 Experimental results

[0122]

[0123] Table 2 Proportion of each element in potassium feldspar residue (EDS results)

[0124]

[0125] The present invention discloses a Pt-CuO-Fe3O4 composite catalyst based on potassium feldspar extraction residue, as well as its preparation method and application. This technology involves ball-milling potassium feldspar, calcium salt, and sodium salt in a certain proportion to uniformly mix them, placing them in a muffle furnace and calcining them in an air atmosphere. The resulting solid product is washed with water and vacuum filtered to obtain soluble potassium ions. The potassium feldspar residue is used as a carrier to load the Pt-CuO-Fe3O4 catalyst, thereby improving the dispersibility of the Pt-CuO-Fe3O4, increasing the number of reactive sites, and effectively reducing the T of toluene degradation. 100 The present invention proposes a technology for comprehensive utilization of potassium feldspar, which has the advantages of simple process flow, high potassium extraction efficiency, lower cost, mild reaction conditions, energy saving, and effective utilization of residues.

[0126] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A method for preparing a Pt-CuO-Fe3O4 composite catalyst based on potassium feldspar potassium extraction residue, characterized in that: The following steps are involved: S1: adding potassium extraction residue of potassium feldspar and copper salt to surfactant solution in sequence to obtain solution A; S2: adding iron salt to the solution A, stirring the mixture at room temperature, and drying and calcining the mixture to obtain a CuO-Fe3O4 / residue composite material; S3: Add H2PtCl6 to the suspension of the CuO-Fe3O4 / residue composite material, ultrasonically oscillate to obtain solution B, add a mixed solution of NaOH and NaBH4 to solution B, oscillate and reduce, dry and calcine the product to obtain the Pt-CuO-Fe3O4 composite catalyst based on potassium feldspar extraction residue.

2. The method for preparing a Pt-CuO-Fe3O4 composite catalyst based on potassium feldspar potassium extraction residue according to claim 1, characterized in that: In step S1, the potassium extraction residue is obtained by ball-milling potassium feldspar, sodium salt and calcium salt, and then calcining them under air atmosphere to obtain a solid product, and washing the solid product with water to obtain the potassium extraction residue.

3. The method for preparing a Pt-CuO-Fe3O4 composite catalyst based on potassium feldspar potassium extraction residue according to claim 2, characterized in that: During ball milling, the rotation speed is 200-600 r / min, the ball milling time is 0.5-4 h, the ball milling beads are a mixed system with particle sizes of 1 mm, 3 mm, 6 mm and 10 mm, and the mass ratio of the 1 mm, 3 mm, 6 mm and 10 mm ball milling beads is (1-5):(1-6):(4-10):(4-10).

4. The method for preparing a Pt-CuO-Fe3O4 composite catalyst based on potassium feldspar potassium extraction residue according to claim 1, characterized in that: In step S1, the mass ratio of the surfactant to the potassium extraction residue is 1:(0.2-1), and the molar ratio of the surfactant to the copper salt is 1:(0.5-2).

5. The method for preparing a Pt-CuO-Fe3O4 composite catalyst based on potassium feldspar potassium extraction residue according to claim 1, characterized in that: In step S2, the iron salt is added to the solution A at a rate of 5 to 15 mL / min.

6. The method for preparing a Pt-CuO-Fe3O4 composite catalyst based on potassium feldspar potassium extraction residue according to claim 1, characterized in that: In step S2, the calcination temperature is 350-650°C, the calcination time is 1-4 hours, and the heating rate is 2-10°C.

7. The method for preparing a Pt-CuO-Fe3O4 composite catalyst based on potassium feldspar potassium extraction residue according to claim 1, characterized in that: In step S3, the concentration of the suspension of the CuO-Fe3O4 / residue composite material is 50-500 g / L, the ultrasonic time is 10-60 min, and the oscillation time is 0.5-3 h.

8. The method for preparing a Pt-CuO-Fe3O4 composite catalyst based on potassium feldspar potassium extraction residue according to claim 1, characterized in that: In step S3, the calcination temperature is 150-450° C., and the calcination time is 1-4 hours.

9. A Pt-CuO-Fe3O4 composite catalyst based on potassium feldspar potassium extraction residue, characterized in that: It is prepared by the method according to any one of claims 1 to 8.

10. Use of the Pt-CuO-Fe3O4 composite catalyst based on potassium feldspar extraction residue as claimed in claim 9 in the field of thermal catalytic oxidation of VOCs.

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