Sludge-based amino acid / phosphoric acid modified copper oxide and preparation method and application thereof

Abstract

The invention discloses a sludge-based amino acid / phosphoric acid modified copper oxide and a preparation method and application thereof, and relates to the technical field of electro-catalysis, solid waste recycling and carbon neutralizer.The preparation method comprises the following steps that 1, sludge-based phosphoric acid and sludge-based copper oxide are subjected to a hydrothermal reaction, filtering and drying, and the sludge-based phosphoric acid modified copper oxide is obtained; and (2) under the action of a cross-linking agent and a surfactant, carrying out hydrothermal reaction on the sludge-based phosphoric acid modified copper oxide and sludge-based amino acid, filtering, extracting by using a Soxhlet extractor, and drying to obtain the sludge-based amino acid / phosphoric acid modified copper oxide. According to the sludge-based amino acid / phosphoric acid modified copper oxide, the activity of the low-concentration CO2 electrocatalytic reduction reaction in industrial flue gas can be remarkably improved, the competitive oxygen reduction reaction is inhibited, and the application potential of the CO2 electrocatalytic reduction technology in the industrial field is improved.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of electrocatalysis and solid waste resource utilization, and in particular to a sludge-based amino acid / phosphoric acid modified copper oxide as well as a preparation method and application thereof. BACKGROUND

[0002] Carbonate decomposition reaction inevitably occurs in the cement production process, and about 0.8 tons of CO2 are emitted per ton of cement clinker produced. Therefore, carbon capture and conversion (CCUS) technology is an inevitable choice for low-carbon or zero-carbon production of cement. Among them, electrochemical reduction of CO2 (eCO2RR) is an extremely advantageous CCUS technology route. The device for electrochemical reduction of CO2 can be modularized, facilitating installation and disassembly. Electrochemical reduction of CO2 can utilize "waste electricity" that cannot be connected to the grid, and is a kind of energy storage method.

[0003] At present, some enterprises in the cement industry have carried out oxygen-enriched (full) combustion technology transformation, and the flue gas CO2 concentration can reach more than 70%, greatly improving the feasibility of electrochemical reduction of flue gas CO2. Direct CO2 electrochemical reduction of cement kiln flue gas will shorten the traditional flue gas CCUS process flow of "flue gas carbon capture + purification + CO2 conversion and utilization", and has great significance for the popularization of CCUS technology in the cement and even building material fields.

[0004] However, electrochemical reduction of flue gas CO2 faces two technical bottlenecks: first, the CO2 concentration in the flue gas is not 100%, and even after oxygen-enriched combustion, the concentration can only reach 70%, and direct electrochemical reduction of flue gas CO2 needs to solve the problem of diffusion limitation of low-concentration CO2 to the surface of the electrocatalyst; second, the flue gas contains a certain amount of O2, and the overpotential of O2 electrochemical reduction is relatively low compared with CO2, and it is easier to be reduced, and there is a competitive relationship with CO2 reduction, and direct electrochemical reduction of flue gas CO2 needs to solve the problem of competitive reduction of O2.

[0005] At present, some mainstream methods are to modify the electrocatalyst with amine groups, the principle of which is that amine groups belong to basic groups and can strengthen the adsorption of acidic gas CO2, and the chemical components with amine groups used are mainly monoethanolamine, diethanolamine, etc. The prices of these reagents are generally expensive, resulting in high modification cost of the electrocatalyst. Therefore, in view of the high cost of the amine group modification method for the flue gas CO2 electrochemical reduction catalyst, a low-cost electrocatalyst capable of strengthening CO2 adsorption and O2 resistance needs to be developed. SUMMARY

[0006] The present application makes full use of the characteristics of sludge rich in protein, phosphorus, copper and other non-metallic / metallic elements, and obtains sludge-based phosphoric acid, sludge-based amino acid and sludge-based copper oxide through acid-base conditioning, calcination and hydrolysis, forming a "core-shell" structure with a porous amino acid shell layer, a phosphoric acid group modified copper oxide core layer. Copper oxide serves as the active site for the electrocatalytic reduction of CO2, the phosphoric acid group enhances the resistance of the electrocatalyst to oxygen, the amino group of the amino acid strengthens the adsorption of the electrocatalyst to CO2, and the special porous structure of the amino acid shell layer also helps to preliminarily separate O2 in the flue gas, reducing the contact concentration of O2 on the surface of copper oxide; at the same time, the sludge-based phosphoric acid extracted from the sludge "contains" various trace "impurities" such as calcium and magnesium ions. These metal ions undergo a doping reaction with copper oxide on the surface of the phosphoric acid group modified copper oxide, adjusting the electronic structure of the copper oxide and significantly improving the electrocatalytic CO2 reduction efficiency of the electrocatalyst under the condition of low-concentration CO2 industrial flue gas containing oxygen. The present application has the advantages of low cost, green environmental protection and realizes waste treatment with waste.

[0007] The technical problems solved by the present application are solved by the following technical solutions: The first object of the present application is to provide a preparation method of sludge-based amino acid / phosphoric acid modified copper oxide, comprising the following steps: (1) performing a hydrothermal reaction of sludge-based phosphoric acid and sludge-based copper oxide, filtering and drying to obtain sludge-based phosphoric acid modified copper oxide; (2) performing a hydrothermal reaction of sludge-based phosphoric acid modified copper oxide and sludge-based amino acid under the action of a crosslinking agent and a surfactant, filtering, extracting using a Soxhlet extractor and drying to obtain sludge-based amino acid / phosphoric acid modified copper oxide.

[0008] Further, the amount ratio of the sludge-based phosphoric acid to the sludge-based copper oxide is (1-5) mL: 1 g. Preferably, the amount ratio of the sludge-based phosphoric acid to the sludge-based copper oxide is 2 mL: 1 g.

[0009] Further, in step (1), the reaction temperature of the hydrothermal reaction is 60-100℃, and the reaction time is 0.5-4h. Preferably, the temperature of the hydrothermal reaction is 80℃, and the time is 2h. The phosphoric acid group is grafted to the surface of the copper oxide through the hydrothermal reaction.

[0010] Further, the surfactant includes but is not limited to at least one of cetyltrimethylammonium bromide (CTAB), polyethylene oxide-polypropylene oxide-polyethylene oxide triblock copolymer F127, polyethylene oxide-polypropylene oxide-polyethylene oxide triblock copolymer P123 and tetradecylamine.

[0011] Further, the cross-linking agent is preferably glutaraldehyde. Using glutaraldehyde as the cross-linking agent has the advantages of high cross-linking efficiency and mild reaction conditions.

[0012] Further, the mass ratio of the sludge-based phosphoric acid modified copper oxide to the sludge-based amino acid is (5-8) : (2-5). Preferably, the mass ratio of the sludge-based phosphoric acid modified copper oxide to the sludge-based amino acid is 2 : 1.

[0013] Further, the mass ratio of the surfactant to the sludge-based amino acid is (0.1-0.5) : 1. Preferably, the mass ratio of the surfactant to the sludge-based amino acid is 0.3 : 1.

[0014] Further, in step (2), the reaction temperature of the hydrothermal reaction is 30-50℃, and the reaction time is 2-8 h. Preferably, the reaction temperature of the hydrothermal reaction is 40℃, and the reaction time is 4 h.

[0015] During the hydrothermal reaction, the surfactant forms micelles, the hydrophilic end of which combines with the polar part of the sludge-based amino acid, and the hydrophobic end of which faces inward as a pore-forming template; glutaraldehyde, as a cross-linking agent, reacts with the sludge-based amino acid and forms a firm cross-linked network that coats the particles; finally, the Soxhlet extractor is used to continuously extract and remove the surfactant, forming pores in the sludge-based amino acid shell.

[0016] Further, the extraction agent extracted by the Soxhlet extractor is preferably ethanol. Ethanol has the advantages of low boiling point, easy volatilization, and low toxicity.

[0017] Further, the preparation method of the sludge-based amino acid is as follows: the municipal sludge is adjusted to a pH value of less than 2 with an acid, heated, filtered, the filtrate is taken, the pH is adjusted to 7-7.5 with a base, filtered, the filter residue is taken, and dried to obtain the sludge-based amino acid. Further, the acid is preferably dilute hydrochloric acid with a concentration of 0.1-0.3 mol / L. One of the purposes of adding acid is to hydrolyze long-chain proteins in the sludge into small molecules of amino acids; the second purpose is to inhibit the activity of sludge microorganisms and prevent the degradation of amino acids. The heating temperature is 90-120℃, and the heating time is 2-8 h; preferably, the heating temperature is 100℃, and the heating time is 4 h. The base is preferably sodium hydroxide or potassium hydroxide, and the aqueous solution has a concentration of 0.5-1 mol / L. The drying is one of oven drying, vacuum drying, and freeze drying. The purpose of drying is to remove water.

[0018] Further, the preparation method of the sludge-based phosphoric acid is as follows: municipal sludge is calcined into sludge ash, the pH value is adjusted to below 2 by using acid, filtration is performed to obtain filtrate 1; the pH value of the filtrate 1 is adjusted to 4-5 by using alkali, filtration is performed to obtain filtrate 2; the pH value of the filtrate 2 is adjusted to 8-10 by using alkali, filtration is performed, the filter residue is taken, and drying is performed; the dried filter residue is mixed with concentrated sulfuric acid, filtration is performed, and filtrate 3 is obtained, which is the sludge-based phosphoric acid. Further, the calcination temperature is 550-750 DEG C, and the time is 1-3 h; preferably, the calcination temperature is 650 DEG C, and the time is 2 h. The acid is preferably dilute hydrochloric acid, and the concentration is 0.1-0.3 mol / L. The alkali is preferably sodium hydroxide or potassium hydroxide, and the concentration of the aqueous solution is 0.5-1 mol / L. The use amount ratio of the filter residue to concentrated sulfuric acid is 1 g :(2-4) mL; preferably, the use amount ratio of the filter residue to concentrated sulfuric acid is 1 g :2 mL. The drying is one of oven drying, vacuum drying and freeze drying. The purpose of drying is to remove water.

[0019] In the preparation process of the sludge-based phosphoric acid, the purpose of calcining the sludge into sludge ash is to convert the phosphorus element into inorganic phosphorus which is easier to extract; the purpose of mixing the sludge ash with acid and adjusting the pH value is to dissolve the inorganic phosphate components and separate the insoluble impurities, and the main components of the filtrate 1 are phosphate, dihydrogen phosphate and ions such as iron, aluminum, calcium and magnesium; the purpose of adjusting the pH value of the filtrate 1 to 4-5 by adding alkali and performing filtration is to remove iron phosphate and aluminum phosphate, and the main components of the filtrate 2 are phosphate, dihydrogen phosphate and ions such as calcium and magnesium; the purpose of adjusting the pH value of the filtrate 2 to 8-10 by adding alkali is to precipitate calcium phosphate, and the main component of the filter residue is calcium phosphate; the purpose of mixing the filter residue with concentrated sulfuric acid and performing filtration is to obtain the sludge-based phosphoric acid through acid-base reaction.

[0020] Further, the preparation method of the sludge-based copper oxide is as follows: reacting municipal sludge with acid and keeping pH at 1.5-2.5, filtering to obtain filtrate 1; adding an oxime-based extractant to the filtrate 1, extracting, separating the extractant, and obtaining an extract separation liquid rich in copper ions; adding sulfuric acid to the extract separation liquid, back-extracting, and obtaining a back-extraction separation liquid rich in copper ions; adding alkali to the back-extraction separation liquid to adjust pH to 7-8, filtering, washing the filter residue with water, drying, calcining, and obtaining the sludge-based copper oxide. Preferably, the acid is dilute hydrochloric acid with a concentration of 0.1-0.3 mol / L; preferably, the use amount ratio of the municipal sludge to the acid is 1 g :(10-30) mL, and the reaction time is 1-3 h; more preferably, the use amount ratio of the municipal sludge to the acid is 1 g:20 mL, and the reaction time is 2 h; preferably, the oxime-based extractant is at least one of LIX84-I and LIX984N, and the volume concentration is 10-20%, and the diluent is kerosene; more preferably, the volume concentration of the oxime-based extractant is 15%. Preferably, the volume ratio of the filtrate 1 to the oxime-based extractant is 1:(0.5-2), and the extraction time is 3-6 min; more preferably, the volume ratio of the filtrate 1 to the oxime-based extractant is 1:1, and the extraction time is 5 min. Preferably, the concentration of the sulfuric acid is 1-3 mol / L. Preferably, the volume ratio of the extract separation liquid to the sulfuric acid is 1:(0.5-2), and the back-extraction time is 3-6 min; more preferably, the volume ratio of the extract separation liquid to the sulfuric acid is 1:1, and the back-extraction time is 5 min. Preferably, the alkali is sodium hydroxide or potassium hydroxide. The calcination temperature is 400-600℃, and the time is 1-3 h; preferably, the calcination temperature is 500℃, and the time is 2 h. The drying is one of oven drying, vacuum drying, and freeze drying. The purpose of drying is to remove water.

[0021] In the preparation process of the sludge-based copper oxide, the purpose of reacting municipal sludge with acid is to dissolve copper elements in the sludge; the purpose of extraction is to combine the copper ions with the extractant to enrich the copper ions from the aqueous phase of the filtrate to the extraction phase, and to exclude the interference of aluminum, iron, calcium and other ions in the filtrate; the purpose of back-extraction using sulfuric acid is to use strong acid to "recover" the copper in the organic phase to the aqueous phase to obtain a pure and high-concentration copper sulfate solution; the purpose of adding alkali to the back-extraction separation liquid to adjust pH to 7-8 and filtering is to precipitate copper elements; the purpose of calcination is to obtain copper oxide; and the purpose of drying is to remove water.

[0022] A second object of the present application is to provide a sludge-based amino acid / phosphoric acid modified copper oxide obtained by the aforementioned preparation method.

[0023] A third object of the present application is to provide the use of the sludge-based amino acid / phosphoric acid modified copper oxide in the electrocatalytic reduction of low-concentration CO2 in industrial flue gas.

[0024] The present application has the following beneficial effects: the present application makes full use of nitrogen, phosphorus and copper elements in sludge, and converts them into material components with special functions by acidolysis and hydrothermal methods, and makes them have special spatial structures. The components include sludge-based amino acid, sludge-based phosphoric acid and sludge-based copper oxide, and the spatial structure is a "core-shell" structure with a porous amino acid shell layer and a phosphoric acid group modified copper oxide core layer. The basic amine groups in the sludge-based amino acid can play a role in enriching acid gas CO2, further strengthening the electrocatalytic reduction of industrial flue gas low-concentration CO2 reaction activity of copper-based active sites, and the carboxyl groups have partial hydrophilic properties, which can also strengthen the adsorption and separation of polar molecules CO2 from low-concentration industrial flue gas. At the same time, the sludge-based amino acid as an external shell layer with a pore structure can also preliminarily separate O2 in the flue gas, reducing the concentration of O2 contacting the phosphoric acid group modified copper oxide core layer with catalytic effect. The sludge-based phosphoric acid extracted from sludge "contains" a variety of trace "impurities" such as calcium and magnesium metal ions, which have a doping reaction with copper oxide on the surface of the phosphoric acid group modified copper oxide, adjusting the electronic structure of the copper oxide. Therefore, the sludge-based amino acid / phosphoric acid modified copper oxide of the present application can significantly improve the electrocatalytic reduction reaction activity of industrial flue gas low-concentration CO2, inhibit the competitive oxygen reduction reaction, and improve the application potential of the electrocatalytic reduction CO2 technology in the industrial field. DETAILED DESCRIPTION

[0025] In order to make the technical means, creative features, purposes and effects achieved by the present application easy to understand, the present application will be further described below in conjunction with specific embodiments.

[0026] Example 1 Preparation of sludge-based amino acid / phosphoric acid modified nickel copper oxide: Step 1: Take 1 g of municipal sludge, add 0.1 mol / L dilute hydrochloric acid to adjust the pH to 1, and heat to 100℃ and stir for 4h, cool, filter, take the filtrate; add 0.5 mol / L sodium hydroxide solution to the filtrate to adjust the pH to 7, filter, take the filter residue, dry in a 70℃ oven for 12h to obtain sludge-based amino acid.

[0027] Step 2, 2 g of municipal sludge was calcined at 650℃ for 2 h to obtain sludge ash; 0.1 mol / L dilute hydrochloric acid was added to the sludge ash to adjust the pH value to 1, and filtration was performed to obtain filtrate 1; 0.5 mol / L aqueous sodium hydroxide solution was added to the filtrate 1 to adjust the pH to 4, and filtration was performed to obtain filtrate 2; 0.5 mol / L aqueous sodium hydroxide solution was added to the filtrate 2 to adjust the pH to 8, and filtration was performed, and the filter residue was dried in an oven at 70℃ for 12 h; 1 g of the dried filter residue was mixed with 2 mL of concentrated sulfuric acid, and filtration was performed to obtain filtrate 3, which was sludge-based phosphoric acid.

[0028] Step 3, 1 g of municipal sludge was added to 20 mL of 0.1 mol / L dilute hydrochloric acid and reacted for 2 h, and filtration was performed to obtain filtrate 1; 20 mL of oxime extractant LIX84-I with a volume concentration of 15% was added to the filtrate 1, and extraction was performed for 5 min to obtain an extract; 20 mL of 2 mol / L sulfuric acid was added to the extract, and back extraction was performed for 5 min to obtain a back-extracted liquid; 0.1 mol / L sodium hydroxide solution was added to the back-extracted liquid to adjust the pH to 8, and filtration was performed, and the filter residue was washed with water, dried in an oven at 70℃ for 12 h, and calcined at 500℃ for 2 h to obtain sludge-based copper oxide.

[0029] Step 4, 2 mL of sludge-based phosphoric acid, 1 g of sludge-based copper oxide, and 10 mL of water were mixed, and hydrothermal reaction was performed at 80℃ for 2 h to obtain phosphoric acid group modified copper oxide.

[0030] Step 5, 2 g of phosphoric acid group modified copper oxide, 1 g of sludge-based amino acid, 0.3 g of CTAB, and 10 mL of water were mixed, and hydrothermal reaction was performed at 40℃ for 4 h, and Soxhlet extractor was used for continuous extraction for 24 h with ethanol as the extractant to obtain sludge-based amino acid / phosphoric acid modified nickel copper oxide.

[0031] Performance test of sludge-based amino acid / phosphoric acid modified nickel copper oxide as an electrocatalyst: The test process adopts a standard three-electrode system and is performed on a Chenhua CHI7600E electrochemical workstation. An H-type electrolytic cell is used, with a Nafion 117 proton exchange membrane serving as a separator. 10 mg of the sludge-based amino acid / phosphoric acid modified nickel-copper oxide prepared in this embodiment is taken as an electrocatalyst, dispersed in 1 mL of isopropanol, and 40 μL of a 5 wt% Nafion solution is added, followed by ultrasonic dispersion to obtain a dispersion liquid. 100 μL of the dispersion liquid is dropped onto a carbon paper with a size of 1 cm x 1 cm as a working electrode, and a platinum sheet and an Ag / AgCl electrode are used as a counter electrode and a reference electrode, respectively. The cathode region of the electrolytic cell is a 0.1 mol / L potassium bicarbonate solution. Before the electrochemical test, pure CO2 and 15% CO2 / 8% O2 / 77% N2 simulated flue gas are respectively introduced into the potassium bicarbonate solution for 30 min. The electrolysis experiment is performed using the electrochemical workstation, with an electrolysis potential of -2.0 V vs Ag / AgCl and an electrolysis time of 2 h. The electrolyte in the cathode region of the reactor is detected using an ion chromatograph, and the formic acid Faraday efficiency is calculated. The results show that the formic acid Faraday efficiency is 79.1% under a pure CO2 atmosphere, and the formic acid Faraday efficiency is 60.8% under a simulated flue gas condition, with a decrease of 23.1%.

[0032] Example 2 In this embodiment, the preparation method of the electrocatalyst is the same as that in Example 1, except that in step 1, 1 g of municipal sludge is taken, 0.3 mol / L dilute hydrochloric acid is added to adjust the pH to 1, and heating to 90°C is performed for 8 h of stirring, cooling, filtration, taking the filtrate, adding 1 mol / L sodium hydroxide aqueous solution to the filtrate to adjust the pH to 7, filtering, taking the filter residue, and drying in a 70°C oven for 12 h to obtain a sludge-based amino acid.

[0033] In this embodiment, the performance test method of the electrocatalyst is the same as that in Example 1. The results show that the formic acid Faraday efficiency is 77.2% under a pure CO2 atmosphere, and the formic acid Faraday efficiency is 58.8% under a simulated flue gas condition, with a decrease of 23.8%.

[0034] Example 3 In this embodiment, the preparation method of the electrocatalyst is the same as that in Example 1, except that in step 1, 1 g of municipal sludge is taken, 0.2 mol / L dilute hydrochloric acid is added to adjust the pH to 1, and heating to 120°C is performed for 2 h of stirring, cooling, filtration, taking the filtrate, adding 0.5 mol / L sodium hydroxide aqueous solution to the filtrate to adjust the pH to 7.5, filtering, taking the filter residue, and drying in a 70°C oven for 12 h to obtain a sludge-based amino acid.

[0035] The performance test method of the electrocatalyst in this example is the same as that in Example 1. The results show that the formic acid Faraday efficiency is 76.4% under the pure CO2 atmosphere condition; the formic acid Faraday efficiency is 57.8% under the simulated flue gas condition, and the reduction range is 24.3%.

[0036] Example 4 The preparation method of the electrocatalyst in this example is the same as that in Example 1, except that step 2: 2 g of municipal sludge is calcined at 550 ℃ for 3 h to obtain sludge ash; 0.2 mol / L dilute hydrochloric acid is added to the sludge ash to adjust the pH value to 1, and filtration is performed to obtain filtrate 1; 1 mol / L sodium hydroxide aqueous solution is added to the filtrate 1 to adjust the pH to 5, and filtration is performed to obtain filtrate 2; 1 mol / L sodium hydroxide aqueous solution is added to the filtrate 2 to adjust the pH to 9, and filtration is performed, and the filter residue is dried in a 70 ℃ oven for 12 h; 1 g of the dried filter residue is mixed with 3 mL of concentrated sulfuric acid, and filtration is performed to obtain filtrate 3, which is the sludge-based phosphoric acid.

[0037] The performance test method of the electrocatalyst in this example is the same as that in Example 1. The results show that the formic acid Faraday efficiency is 76.8% under the pure CO2 atmosphere condition; the formic acid Faraday efficiency is 58.2% under the simulated flue gas condition, and the reduction range is 24.2%.

[0038] Example 5 The preparation method of the electrocatalyst in this example is the same as that in Example 1, except that step 2: 2 g of municipal sludge is calcined at 750 ℃ for 1 h to obtain sludge ash; 0.1 mol / L dilute hydrochloric acid is added to the sludge ash to adjust the pH value to 1, and filtration is performed to obtain filtrate 1; 0.5 mol / L sodium hydroxide aqueous solution is added to the filtrate 1 to adjust the pH to 4, and filtration is performed to obtain filtrate 2; 0.5 mol / L sodium hydroxide aqueous solution is added to the filtrate 2 to adjust the pH to 9, and filtration is performed, and the filter residue is dried in a 70 ℃ oven for 12 h; 1 g of the dried filter residue is mixed with 4 mL of concentrated sulfuric acid, and filtration is performed to obtain filtrate 3, which is the sludge-based phosphoric acid.

[0039] The performance test method of the electrocatalyst in this example is the same as that in Example 1. The results show that the formic acid Faraday efficiency is 76.9% under the pure CO2 atmosphere condition; the formic acid Faraday efficiency is 58.4% under the simulated flue gas condition, and the reduction range is 24.1%.

[0040] Example 6 The preparation method of the electrocatalyst in this example is the same as that in Example 1, except that step 3: 1 g of municipal sludge is taken, 20 mL of 0.1 mol / L dilute hydrochloric acid is added, and the mixture is reacted for 2 h, filtered to obtain filtrate 1; 20 mL of oxime extractant LIX84-I with a volume concentration of 15% is added to the filtrate 1, and the mixture is extracted for 5 min to obtain an extract; 20 mL of 2 mol / L sulfuric acid is added to the extract, and the mixture is back-extracted for 5 min to obtain a back-extract solution; 0.1 mol / L sodium hydroxide solution is added to the back-extract solution to adjust the pH to 8, the mixture is filtered, the filter residue is taken, washed with water, dried in a 70°C oven for 12 h, and calcined at 400°C for 3 h to obtain sludge-based copper oxide.

[0041] The performance test method of the electrocatalyst in this example is the same as that in Example 1. The results show that under a pure CO2 atmosphere, the formic acid faradic efficiency is 75.9%; under a simulated flue gas atmosphere, the formic acid faradic efficiency is 57.4%, and the decrease is 24.4%.

[0042] Example 7 The preparation method of the electrocatalyst in this example is the same as that in Example 1, except that step 3: 1 g of municipal sludge is taken, 20 mL of 0.1 mol / L dilute hydrochloric acid is added, and the mixture is reacted for 2 h, filtered to obtain filtrate 1; 20 mL of oxime extractant LIX84-I with a volume concentration of 15% is added to the filtrate 1, and the mixture is extracted for 5 min to obtain an extract; 20 mL of 2 mol / L sulfuric acid is added to the extract, and the mixture is back-extracted for 5 min to obtain a back-extract solution; 0.1 mol / L sodium hydroxide solution is added to the back-extract solution to adjust the pH to 8, the mixture is filtered, the filter residue is taken, washed with water, dried in a 70°C oven for 12 h, and calcined at 600°C for 1 h to obtain sludge-based copper oxide.

[0043] The performance test method of the electrocatalyst in this example is the same as that in Example 1. The results show that under a pure CO2 atmosphere, the formic acid faradic efficiency is 75.1%; under a simulated flue gas atmosphere, the formic acid faradic efficiency is 56.8%, and the decrease is 24.4%.

[0044] Example 8 The preparation method of the electrocatalyst in this example is the same as that in Example 1, except that step 4: 1 mL of sludge-based phosphoric acid, 1 g of sludge-based copper oxide, and 10 mL of water are mixed, and the mixture is hydrothermally reacted at 80°C for 1 h to obtain phosphoric acid group modified copper oxide.

[0045] The performance test method of the electrocatalyst in this example is the same as that in Example 1. The results show that under a pure CO2 atmosphere, the formic acid faradic efficiency is 75.1%; under a simulated flue gas atmosphere, the formic acid faradic efficiency is 55.6%, and the decrease is 25.9%.

[0046] Example 9 The preparation method of the electrocatalyst in this example is the same as that in Example 1, except that step 4: 5 mL of sludge-based phosphoric acid, 1 g of sludge-based copper oxide, and 10 mL of water are mixed, and hydrothermal reaction is carried out at 60°C for 4 h to obtain phosphoric acid group modified copper oxide.

[0047] The performance test method of the electrocatalyst in this example is the same as that in Example 1. The results show that under the condition of pure CO2 atmosphere, the formic acid faradic efficiency is 76.3%; under the condition of simulated flue gas, the formic acid faradic efficiency is 56.6%, and the reduction amplitude is 25.8%.

[0048] Example 10 The preparation method of the electrocatalyst in this example is the same as that in Example 1, except that step 5: 4 g of phosphoric acid group modified copper oxide, 1 g of sludge-based amino acid, 0.3 g of CTAB, and 10 mL of water are mixed, and hydrothermal reaction is carried out at 40°C for 4 h, and a Soxhlet extractor is used for continuous extraction for 24 h with ethanol as the extraction agent to obtain sludge-based amino acid / phosphoric acid modified nickel copper oxide.

[0049] The performance test method of the electrocatalyst in this example is the same as that in Example 1. The results show that under the condition of pure CO2 atmosphere, the formic acid faradic efficiency is 76.6%; under the condition of simulated flue gas, the formic acid faradic efficiency is 55.1%, and the reduction amplitude is 28.1%.

[0050] Example 11 The preparation method of the electrocatalyst in this example is the same as that in Example 1, except that step 5: 1 g of phosphoric acid group modified copper oxide, 1 g of sludge-based amino acid, 0.5 g of F127, and 10 mL of water are mixed, and hydrothermal reaction is carried out at 50°C for 2 h, and a Soxhlet extractor is used for continuous extraction for 24 h with ethanol as the extraction agent to obtain sludge-based amino acid / phosphoric acid modified nickel copper oxide.

[0051] The performance test method of the electrocatalyst in this example is the same as that in Example 1. The results show that under the condition of pure CO2 atmosphere, the formic acid faradic efficiency is 74.3%; under the condition of simulated flue gas, the formic acid faradic efficiency is 54.6%, and the reduction amplitude is 26.5%.

[0052] Example 12 The preparation method of the electrocatalyst in this example is the same as that in Example 1, except that step 5: 2 g of phosphoric acid group modified copper oxide, 1 g of sludge-based amino acid, 0.3 g of CTAB, and 10 mL of water are mixed, and hydrothermal reaction is carried out at 30°C for 8 h, and a Soxhlet extractor is used for continuous extraction for 24 h with ethanol as the extraction agent to obtain sludge-based amino acid / phosphoric acid modified nickel copper oxide.

[0053] The performance test method of the electrocatalyst in this example is the same as that in Example 1. The results show that the formic acid faradic efficiency is 77.2% under the pure CO2 atmosphere condition; the formic acid faradic efficiency is 58.5% under the simulated flue gas condition, and the reduction amplitude is 24.2%.

[0054] Comparative Example 1 The preparation method of the electrocatalyst in this comparative example is the same as that in Example 1, except that no sludge-based phosphoric acid is added in step 4.

[0055] The performance test method of the electrocatalyst in this comparative example is the same as that in Example 1. The results show that the formic acid faradic efficiency is 73.4% under the pure CO2 atmosphere condition; the formic acid faradic efficiency is 42.1% under the simulated flue gas condition, and the reduction amplitude is 42.6%.

[0056] Comparative Example 2 The preparation method of the electrocatalyst in this comparative example is the same as that in Example 1, except that no sludge-based amino acid is added in step 5.

[0057] The performance test method of the electrocatalyst in this comparative example is the same as that in Example 1. The results show that the formic acid faradic efficiency is 72.1% under the pure CO2 atmosphere condition; the formic acid faradic efficiency is 49.5% under the simulated flue gas condition, and the reduction amplitude is 31.3%.

[0058] Comparative Example 3 The preparation method of the electrocatalyst in this comparative example is the same as that in Example 1, except that no surfactant is added in step 5.

[0059] The performance test method of the electrocatalyst in this comparative example is the same as that in Example 1. The results show that the formic acid faradic efficiency is 69.8% under the pure CO2 atmosphere condition; the formic acid faradic efficiency is 46.5% under the simulated flue gas condition, and the reduction amplitude is 33.3%.

[0060] Comparative Example 4 The preparation method of the electrocatalyst in this comparative example is the same as that in Example 1, except that no sludge-based phosphoric acid is added in step 4, and no sludge-based amino acid and surfactant are added in step 5.

[0061] The performance test method of the electrocatalyst in this comparative example is the same as that in Example 1. The results show that the formic acid faradic efficiency is 61.8% under the pure CO2 atmosphere condition; the formic acid faradic efficiency is 23.5% under the simulated flue gas condition, and the reduction amplitude is 61.9%.

[0062] The above shows and describes the basic principles and main features of the present application and the advantages of the present application. Those skilled in the art should understand that the present application is not limited to the above embodiments, and the above embodiments and descriptions in the specification are only to illustrate the principles of the present application. Without departing from the spirit and scope of the present application, various changes and improvements can be made to the present application, and these changes and improvements all fall within the scope of the claimed present application. The scope of protection of the present application is defined by the appended claims and their equivalents.

Claims

1. A method for preparing a sludge-based amino acid / phosphoric acid-modified copper oxide, characterized by, The method comprises the following steps: (1) performing a hydrothermal reaction on sludge-based phosphoric acid and sludge-based copper oxide, filtering, drying, and obtaining sludge-based phosphoric acid modified copper oxide; (2) under the action of a crosslinking agent and a surfactant, performing a hydrothermal reaction on the sludge-based phosphoric acid modified copper oxide and sludge-based amino acid, filtering, extracting by using a Soxhlet extractor, drying, and obtaining sludge-based amino acid / phosphoric acid modified copper oxide.

2. The method of claim 1, wherein: The ratio of the amount of the sludge-based phosphoric acid to the amount of the sludge-based copper oxide is (1-5) mL:1 g; preferably, the ratio of the amount of the sludge-based phosphoric acid to the amount of the sludge-based copper oxide is 2 mL:1 g. In step (1), the temperature of the hydrothermal reaction is 60-100 DEG C, and the reaction time is 0.5-4 h; preferably, the temperature of the hydrothermal reaction is 80 DEG C, and the reaction time is 2 h.

3. The method of claim 1, wherein: The surfactant is at least one of cetyltrimethylammonium bromide, polyethylene oxide-polypropylene oxide-polyethylene oxide triblock copolymer F127, polyethylene oxide-polypropylene oxide-polyethylene oxide triblock copolymer P123, and tetradecylamine; Preferably, the crosslinking agent is glutaraldehyde; Preferably, the extractant for the Soxhlet extractor extraction is ethanol.

4. The method of claim 1, wherein: The mass ratio of the sludge-based phosphoric acid modified copper oxide to the sludge-based amino acid is (5-8):(2-5); preferably, the mass ratio of the sludge-based phosphoric acid modified copper oxide to the sludge-based amino acid is 2:

1. The mass ratio of the surfactant to the sludge-based amino acid is (0.1-0.5):1; preferably, the mass ratio of the surfactant to the sludge-based amino acid is 0.3:

1.

5. The method of claim 1, wherein: In step (2), the temperature of the hydrothermal reaction is 30-50 DEG C, and the reaction time is 2-8 h; preferably, the temperature of the hydrothermal reaction is 40 DEG C, and the reaction time is 4 h.

6. The method of claim 1, wherein, The preparation method of the sludge-based amino acid is as follows: municipal sludge is adjusted to a pH value of less than 2 by using an acid, heated, filtered, the filtrate is obtained, the pH value is adjusted to 7-7.5 by using a base, filtered, the filter residue is obtained, and dried to obtain sludge-based amino acid; Preferably, the acid is dilute hydrochloric acid, and the concentration is 0.1-0.3 mol / L; Preferably, the heating temperature is 90-120 DEG C, and the heating time is 2-8 h; more preferably, the heating temperature is 100 DEG C, and the heating time is 4 h; Preferably, the base is sodium hydroxide or potassium hydroxide, and the concentration of the aqueous solution is 0.5-1 mol / L; Preferably, the drying is one of oven drying, vacuum drying, and freeze drying.

7. The preparation method according to claim 1, characterized in that, The preparation method of the sludge-based phosphoric acid is as follows: municipal sludge is calcined into sludge ash, the pH value is adjusted to less than 2 by using an acid, filtered to obtain filtrate 1, the pH value of the filtrate 1 is adjusted to 4-5 by using a base, filtered to obtain filtrate 2, the pH value of the filtrate 2 is adjusted to 8-10 by using a base, filtered, the filter residue is obtained, and dried; the dried filter residue is mixed with concentrated sulfuric acid, filtered, and filtrate 3 is obtained, which is sludge-based phosphoric acid; Preferably, the calcination temperature is 550-750 DEG C, and the calcination time is 1-3 h; more preferably, the calcination temperature is 650 DEG C, and the calcination time is 2 h. Preferably, the acid is dilute hydrochloric acid with a concentration of 0.1-0.3 mol / L; Preferably, the base is sodium hydroxide or potassium hydroxide with a concentration of 0.5-1 mol / L in aqueous solution; Preferably, the ratio of the filter residue to concentrated sulfuric acid is 1 g :(2-4) mL; more preferably, the ratio of the filter residue to concentrated sulfuric acid is 1 g:2 mL; Preferably, the drying is one of oven drying, vacuum drying, and freeze drying.

8. The production method according to claim 1, characterized by, The preparation method of the sludge-based copper oxide is as follows: reacting municipal sludge with an acid and maintaining pH at 1.5-2.5, filtering to obtain filtrate 1; adding an oxime-based extractant to the filtrate 1, extracting, separating the extractant, and obtaining an extraction separation liquid rich in copper ions; adding sulfuric acid to the extraction separation liquid, back-extracting, and obtaining a back-extraction separation liquid rich in copper ions; adjusting the pH of the back-extraction separation liquid to 7-8 by adding a base, filtering, water-washing the filter residue, drying, and calcining to obtain the sludge-based copper oxide; Preferably, the acid is dilute hydrochloric acid with a concentration of 0.1-0.3 mol / L; Preferably, the ratio of the municipal sludge to the acid is 1 g :(10-30) mL, and the reaction time is 1-3 h; more preferably, the ratio of the municipal sludge to the acid is 1 g:20 mL, and the reaction time is 2 h; Preferably, the oxime-based extractant is at least one of LIX84-I and LIX984N, and the volume concentration is 10-20%, and the diluent is kerosene; more preferably, the volume concentration of the oxime-based extractant is 15%; Preferably, the volume ratio of the filtrate 1 to the oxime-based extractant is 1 :(0.5-2), and the extraction time is 3-6 min; more preferably, the volume ratio of the filtrate 1 to the oxime-based extractant is 1:1, and the extraction time is 5 min; Preferably, the concentration of the sulfuric acid is 1-3 mol / L; Preferably, the volume ratio of the extraction separation liquid to the sulfuric acid is 1 :(0.5-2), and the back-extraction time is 3-6 min; more preferably, the volume ratio of the extraction separation liquid to the sulfuric acid is 1:1, and the back-extraction time is 5 min; Preferably, the base is sodium hydroxide or potassium hydroxide; Preferably, the calcination temperature is 400-600°C, and the time is 1-3 h; more preferably, the calcination temperature is 500°C, and the time is 2 h; Preferably, the drying is one of oven drying, vacuum drying, and freeze drying.

9. A sludge-based amino acid / phosphoric acid modified copper oxide obtained by the preparation method of any one of claims 1-8.

10. Use of the sludge-based amino acid / phosphoric acid modified copper oxide of claim 9 in electrocatalytic reduction of oxygen-containing low-concentration industrial flue gas CO2.