Preparation method of sediment-based catalyst for strengthening oxidation efficiency of calcium peroxide

Abstract

The invention relates to the technical field of river and lake sediment treatment, in particular to a preparation method of a sediment-based catalyst for strengthening oxidation efficiency of calcium peroxide, which comprises the following steps: S1, drying, grinding and screening biogas residue to obtain powdery biogas residue; s2, drying, grinding and screening the river and lake bottom mud to obtain powdery bottom mud; s3, obtaining biochar rich in mineral substances; s4, the obtained biochar is subjected to nano-iron doping treatment, nano-iron-doped biochar is obtained, and the bottom mud-based catalyst is obtained. Biogas residues adopted by the method contain a large amount of organic matter, humic acid and micronutrient elements, the dehydrated bottom mud conditioned through the method is applied to agricultural land, the good effect of improving soil can be achieved, and the soil quality is improved; in addition, the biogas residues and the river and lake bottom mud contain plant nutrient elements such as nitrogen, phosphorus and potassium, and the requirements of crop growth can be met. The biogas residues and the river and lake bottom mud are used for preparing the biochar, waste is used for treating waste, and recycling of the waste is achieved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of river and lake sediment treatment, in particular to a preparation method of a sediment-based catalyst for enhancing the oxidation efficiency of calcium peroxide. BACKGROUND

[0002] River and lake sediments generally have high water content, complex pollution components, and low permeability, making sediment treatment difficult. Sediment dewatering is a necessary step to reduce the volume of sludge, reduce the cost of subsequent treatment and disposal, and improve the safety of subsequent treatment and final disposal. Due to the small size of sediment particles, strong hydrophilicity, and high compressibility, dewatering is difficult, so the sediment needs to be conditioned before dewatering to improve its dewatering performance. Antibiotics and antiviral drugs and other new pollutants have been detected in river and lake sediments to varying degrees. These new pollutants have structural stability and environmental persistence, and are poorly biodegradable, easily remaining in the environment for a long time, and harming the ecosystem and human health. The commonly used coagulant / flocculant improves the dewatering performance of the sediment through charge neutralization and adsorption bridging, but cannot effectively destroy the hydrophilic groups, limiting the release of bound water. Therefore, it is necessary to destroy the hydrophilic film, reduce the compressibility, and promote the release of bound water to achieve deep dewatering of the sediment. In addition, coagulation / flocculation does not effectively remove the new pollutants contained in the sediment, which are currently of great concern, and advanced oxidation technology is needed, which is economically costly.

[0003] Calcium peroxide, as a thermally stable, multifunctional and environmentally friendly peroxide, can slowly release oxygen and hydrogen peroxide, and has dual functions of oxidation and flocculation. However, the rate of hydrogen peroxide release from calcium peroxide is very slow, and a suitable catalyst is needed to activate and promote its decomposition. Biogas production generates a large amount of residual biogas residue, which is rich in humic acid and other macromolecular organic matter. The biochar prepared by pyrolysis and carbonization of the biogas residue has abundant organic functional groups, which can catalyze the calcium peroxide to produce strong oxidizing free radicals and improve the oxidation efficiency of calcium peroxide. However, the specific surface area of single biochar is not large enough, and the pore adsorption capacity is low, so the structure and properties of the biochar need to be optimized. River and lake sediments contain a large amount of mineral components that can further promote the decomposition of calcium peroxide. Therefore, the present application uses river and lake sediments to prepare biochar to catalyze calcium peroxide for treating sediment, achieving waste-to-waste and recycling and utilization of waste. SUMMARY

[0004] The purpose of the present application is to overcome the shortcomings of the prior art, and to provide a preparation method of a sediment-based biochar. The prepared catalyst is used to catalyze calcium peroxide for treating sediment, which has high catalytic efficiency, is simple to operate, and is low in cost, and also realizes the resource utilization of waste.

[0005] The specific technical solution is as follows: a preparation method of a sediment-based catalyst for enhancing the oxidation efficiency of calcium peroxide, comprising the following steps:

[0006] S1. Dry, grind and sieve the biogas residue to obtain a powder;

[0007] S2. Dry, grind and sieve the river and lake sediment to obtain a powder;

[0008] S3. Mix the powder of biogas residue and sediment in a certain proportion, add 2 mol / L KOH solution for activation, adjust the pH of the mixture to alkaline, and then perform ultrasonic treatment, stirring, centrifugation, vacuum drying at 60℃, high-temperature calcination pyrolysis in a tube furnace, cooling to room temperature, grinding and sieving, and washing with deionized water and ethanol until neutral, and vacuum drying at 60℃ to obtain mineral-rich biochar;

[0009] S4. Perform nano-iron doping treatment on the obtained biochar to obtain nano-iron doped biochar, i.e., a sediment-based catalyst.

[0010] Nano-iron can promote the decomposition of calcium peroxide to produce more active oxygen species through electron transfer effect, while enhancing the adsorption performance of the biochar surface, thereby synergistically improving the oxidative degradation efficiency of pollutants in the sediment.

[0011] As a further technical solution, in step S1, the biogas residue is the residue after anaerobic fermentation of straw or kitchen waste at a temperature of 30-40℃ for 30-60 days.

[0012] As a further technical solution, in step S1, the drying temperature of the biogas residue is 70℃, and the ground biogas residue is sieved with a 100-300 mesh sieve.

[0013] As a further technical solution, in step S2, the typical river and lake sediment contains mineral components mainly including SiO2, Al2O3, Fe2O3 and CaO, with contents of 15-22%, 8-15%, 2-9% and 2-7%, respectively, and an organic matter content of 1-10%.

[0014] As a further technical solution, in step S2, the drying temperature of the river and lake sediment is 70℃, and the ground river and lake sediment is sieved with a 100-300 mesh sieve.

[0015] As a further technical solution, in step S3, the addition ratio of the powder of biogas residue and river and lake sediment is 10-20:1, and the addition amount of KOH solution is such that the pH of the mixture is 9-11.

[0016] As a further technical solution, in step S3, the ultrasonic power is 30-100W, the ultrasonic time is 1-3h, the stirring speed is 100-300rpm / min, the stirring time is 6-12h, the centrifugal speed is 1000-3000g, and the centrifugal time is 10-30min.

[0017] As a further technical solution, in step S3, during high-temperature calcination of the tube furnace, the pyrolysis temperature is 500-900 DEG C, inert gas is used as the protective gas, the pyrolysis process is started at a heating rate of 10-30 DEG C / min and a pyrolysis time of 2-5 h, and the ground biochar is sieved through a 200-400 mesh sieve.

[0018] As a further technical solution, in step S4, the specific steps of the nano-iron doping treatment are as follows: the biochar is added to a 0.1-0.5 mol / L ferrous sulfate solution, the solid-liquid ratio of the biochar to the ferrous sulfate solution is 1:15-18, stirring is carried out under nitrogen protection for 30-60 min, then a 0.2-1 mol / L sodium borohydride solution is added dropwise, the molar ratio of the sodium borohydride to the ferrous sulfate is 2-4:1, stirring is continued for 1-2 h, centrifugal separation is carried out, washing is carried out with deionized water until neutral, vacuum drying is carried out at 60-80 DEG C, and nano-iron doped biochar is obtained.

[0019] The concentration of the ferrous sulfate solution is 0.2-0.4 mol / L, the solid-liquid ratio of the biochar to the ferrous sulfate solution is 1:20-26, the concentration of the sodium borohydride solution is 0.4-0.8 mol / L, and the molar ratio of the sodium borohydride to the ferrous sulfate is 2.9-3.5:1.

[0020] As a further technical solution, the use method of the sediment-based catalyst is as follows: the obtained nano-iron doped biochar is uniformly mixed with river and lake sediment, is placed in a reactor, and calcium peroxide is added for sediment treatment.

[0021] The dosage of the nano-iron doped biochar is 100-400 mg / g DS, and the dosage of the calcium peroxide is 10-100 mg / g DS.

[0022] After treatment, the water content of the dewatered sediment is 30%-40%, antibiotics and antiviral drugs are used as target new pollutants, the removal rate of the antibiotics is 60%-80%, and the removal rate of the antiviral drugs is 50%-70%.

[0023] The beneficial effects are as follows:

[0024] The purpose of the present application is achieved through the following working principle:

[0025] Firstly, calcium peroxide is dissolved in water to slowly release hydrogen peroxide; the biochar prepared from the biogas residue and the river and lake sediment has a large specific surface area, which provides more adsorption sites for the sediment and calcium peroxide molecules, promotes the decomposition of the calcium peroxide and the contact reaction between the calcium peroxide and the sediment particles; the biogas residue contains a large amount of organic matter and humic acid, which catalyzes the generation of singlet oxygen (1O2) from hydrogen peroxide. 1O2) and other free radicals; the river and lake sediment contains rich minerals and metal oxides, which increases the catalytic calcium peroxide active sites on the surface of the biochar, and the catalytic calcium peroxide generates strong oxidizing (·OH) and other free radicals; under the action of active oxidizing species, the sediment hydrophilic film is destroyed, intracellular water is released, and a large number of hydrophilic groups are oxidized and degraded, reducing the hydrophilicity of the sediment, and the water of hydration is converted into free water, promoting the separation of the sediment and water; calcium ions have coagulation effect, and the sediment fragments generated after oxidation are coagulated to form large particle aggregates, facilitating the dewatering of the sediment; the biochar acts as a skeleton building block, which builds a rigid and porous structure, and can provide a channel for the discharge of water during pressure filtration dewatering, thereby significantly improving the dewatering performance of the sediment; finally, under the action of strong oxidizing free radicals, the covalent bonds and structures of antibiotics and antiviral drugs are destroyed, so that they are oxidized and degraded.

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

[0027] (1) The biogas residue contains a large amount of organic matter, humic acid and trace nutrients, and the dewatered sediment treated by this method can improve the soil when applied to agricultural land, and the biogas residue and river and lake sediment contain nitrogen, phosphorus, potassium and other plant nutrients, which can meet the needs of crop growth.

[0028] (2) The biogas residue and river and lake sediment are used to prepare biochar, which realizes the recycling and utilization of waste, and the prepared catalyst does not have adverse effects on the subsequent use of the sediment.

[0029] (3) The biochar catalyst prepared by the present application has high catalytic activity, and has the triple effects of strengthening calcium peroxide oxidation, coagulation and skeleton building, achieving the effects of strengthening sediment dewatering and removing new pollutants. BRIEF DESCRIPTION OF DRAWINGS

[0030] Figure 1 The scanning electron microscope SEM image of the biochar prepared in Example 3 of the present application. DETAILED DESCRIPTION

[0031] The technical solutions in the embodiments of the present application will be described clearly and completely below. Obviously, the described embodiments are only a part of the embodiments of the present application, not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0032] Example 1

[0033] The straw biogas residue and organic matter, SiO2, Al2O3, Fe2O3 and CaO contents of 1%, 15%, 10%, 6% and 5% of the river and lake sediment were dried, ground and sieved with a 100 mesh sieve respectively; the obtained powder-like biogas residue and river and lake sediment were mixed in a mass ratio of 20:1, 2 mol / L KOH solution was added to adjust the pH value of the mixture to 9, and the mixture was subjected to ultrasonic treatment at a power of 30 W for 1 h, and stirred at a speed of 100 rpm / min for 6 h, and then centrifuged at a centrifugal speed of 1000 g for 10 min; the solid after centrifugation was calcined in a tubular furnace at high temperature, with nitrogen as the protective gas, the pyrolysis temperature was 500℃, the heating rate was 10℃ / min, the pyrolysis time was 2h, after cooling to room temperature, grinding, sieving with a 200 mesh sieve, washing with ethanol and deionized water several times until neutral, vacuum drying at 60℃ to obtain mineral-rich biochar;

[0034] The mineral-rich biochar was added to a 0.1 mol / L ferrous sulfate solution, the solid-liquid ratio of biochar to ferrous sulfate solution was 1:15, stirred under nitrogen protection for 30 min, then 0.2 mol / L sodium borohydride solution was added dropwise, the molar ratio of sodium borohydride to ferrous sulfate was 2:1, and the stirring was continued for 1 h, then centrifugal separation was performed, and the product was washed with deionized water until neutral, and vacuum dried at 60℃ to obtain nano-iron doped biochar;

[0035] The concentration of the ferrous sulfate solution was 0.2 mol / L, the solid-liquid ratio of the biochar to the ferrous sulfate solution was 1:20, the concentration of the sodium borohydride solution was 0.4 mol / L, and the molar ratio of sodium borohydride to ferrous sulfate was 2.9:1.

[0036] The electron donating capacity (EDC), electron accepting capacity (EAC) and electron exchange capacity (EEC) of the biochar were 0.613, 0.152 and 0.765 meq / e·g respectively, the number of Lewis acid sites was 60.78 μmol / g, and the biochar had good catalytic activity; 200 mL of river and lake sediment with a water content of 93% was mixed with 100 mg / gDS of biochar, and then 10 mg / gDS of calcium peroxide was added and reacted for 10 min, the treated sediment was mechanically pressure-filtered to obtain dewatered sediment with a water content of 40%, and the removal rates of antibiotics and antiviral drugs were 61% and 53% respectively.

[0037] Example 2

[0038] The straw biogas residue and organic matter, SiO2, Al2O3, Fe2O3 and CaO contents of the river and lake sediment were respectively 10%, 22%, 8%, 2% and 7% at 40°C for 30 days of anaerobic fermentation, respectively dried, ground, and sieved with a 200 mesh sieve; the obtained powder-like biogas residue and river and lake sediment were mixed in a mass ratio of 15:1, 2 mol / L KOH solution was added to adjust the pH value of the mixture to 10, and the mixture was subjected to ultrasonic treatment at a power of 30 W for 1 h, and stirred at a speed of 100 rpm / min for 6 h, then centrifuged at a centrifugal speed of 2000 g for 20 min; the solid after centrifugation was calcined in a tubular furnace at high temperature, with nitrogen as the protective gas, the pyrolysis temperature was 900°C, the heating rate was 25°C / min, the pyrolysis time was 4 h, after cooling to room temperature, grinding, sieving with a 300 mesh sieve, washing with ethanol and deionized water several times until neutral, vacuum drying at 60°C to obtain mineral-rich biochar;

[0039] The mineral-rich biochar was added to a 0.3 mol / L ferrous sulfate solution, the solid-liquid ratio of biochar to ferrous sulfate solution was 1:16, stirred under nitrogen protection for 40 min, then 0.5 mol / L sodium borohydride solution was added dropwise, the molar ratio of sodium borohydride to ferrous sulfate was 3:1, and the stirring was continued for 1-2 h, then centrifugal separation was performed, and the product was washed with deionized water until neutral, and vacuum dried at 70°C to obtain nano-iron doped biochar;

[0040] The concentration of the ferrous sulfate solution was 0.3 mol / L, the solid-liquid ratio of the biochar to the ferrous sulfate solution was 1:24, the concentration of the sodium borohydride solution was 0.6 mol / L, and the molar ratio of sodium borohydride to ferrous sulfate was 3.2:1.

[0041] The EDC, EAC and EEC of the biochar were 0.596, 0.247 and 0.843 meq / e·g, respectively, the number of Lewis acid sites was 66.12 μmol / g, and the biochar had good catalytic activity; 200 mL of river and lake sediment with a water content of 96% was mixed with 400 mg / gDS of biochar, and then placed in a reactor, 100 mg / gDS of calcium peroxide was added and reacted for 10 min, the treated sediment was mechanically pressure-filtered to obtain dewatered sediment with a water content of 35%, and the antibiotic removal rate was 78%, and the antiviral drug removal rate was 67%.

[0042] Example 3

[0043] The straw biogas residue and organic matter, SiO2, Al2O3, Fe2O3 and CaO contents of the river and lake sediment were dried, ground and sieved with a 300 mesh sieve after anaerobic fermentation at 35℃ for 45d; the obtained powder-like biogas residue and river and lake sediment were mixed in a mass ratio of 10:1, 2mol / L KOH solution was added to adjust the pH value of the mixture to 11, and the mixture was subjected to ultrasonic treatment at a power of 100W for 3h, and stirred at a speed of 300rpm / min for 12h, then centrifuged at a centrifugal speed of 3000g for 30min; the solid after centrifugation was calcined in a tubular furnace at high temperature, with argon as the protective gas, the pyrolysis temperature was 750℃, the heating rate was 30℃ / min, the pyrolysis time was 5h, after cooling to room temperature, grinding, sieving with a 400 mesh sieve, washing with ethanol and deionized water several times until neutral, vacuum drying at 60℃ to obtain mineral-rich biochar;

[0044] The mineral-rich biochar was added to a 0.5mol / L ferrous sulfate solution, the solid-liquid ratio of biochar to ferrous sulfate solution was 1:18, stirred under nitrogen protection for 60min, then 1mol / L sodium borohydride solution was added dropwise, the molar ratio of sodium borohydride to ferrous sulfate was 4:1, and the stirring was continued for 2h, then centrifugal separation was performed, and the product was washed with deionized water until neutral, and vacuum dried at 80℃ to obtain nano-iron doped biochar;

[0045] The concentration of the ferrous sulfate solution was 0.4mol / L, the solid-liquid ratio of the biochar to the ferrous sulfate solution was 1:26, the concentration of the sodium borohydride solution was 0.8mol / L, and the molar ratio of sodium borohydride to ferrous sulfate was 3.5:1.

[0046] The EDC, EAC and EEC of the biochar were 0.601, 0.208 and 0.809meq / e·g respectively, the number of Lewis acid sites was 65.04μmol / g, and the biochar had good catalytic activity; 200mL of river and lake sediment with a water content of 98% was mixed with 300mg / gDS of biochar, and then placed in a reactor, 50mg / gDS of calcium peroxide was added and reacted for 10min, the treated sediment was mechanically pressure-filtered to obtain dewatered sediment with a water content of 38%, the antibiotic removal rate was 70%, and the antiviral drug removal rate was 59%.

[0047] Comparative Example 1

[0048] Under the condition of no biochar addition, 200 mL of river and lake sediment with 98% moisture content, 10% SiO2, 22% Al2O3, 8% Fe2O3 and 7% CaO, was put into the reactor, 50 mg / gDS of calcium peroxide was added and reacted for 10 min, and the treated sediment was mechanically pressure filtered to obtain dewatered sediment with 56% moisture content, 38% antibiotic removal rate and 24% antiviral drug removal rate.

[0049] Comparative Example 2

[0050] The straw biogas residue anaerobically fermented at 35℃ for 45d was dried, ground and sieved with a 300 mesh sieve; 2 mol / L KOH solution was added to adjust the pH of the mixture to 11, and the mixture was subjected to ultrasonic treatment at a power of 100W for 3h, and then stirred at a speed of 300 rpm / min for 12h, and then centrifuged at a centrifugal speed of 3000g for 30min; the solid after centrifugation was calcined at high temperature in a tube furnace with argon as the protective gas, the pyrolysis temperature was 750℃, the heating rate was 30℃ / min, and the pyrolysis time was 5h; after cooling to room temperature, the mixture was ground and sieved with a 400 mesh sieve, washed with ethanol and deionized water several times until neutral, and then vacuum dried at 60℃ to obtain the mineral-enriched biochar; the EDC, EAC and EEC of the biochar were 0.528, 0.057 and 0.585 meq / e·g respectively, the number of Lewis acid sites was 33.62 μmol / g, and the catalytic activity was lower than that of the biochar prepared by mixing biogas residue and river and lake sediment; 200 mL of river and lake sediment with 98% moisture content was mixed with 300 mg / gDS of biochar, and then put into the reactor and reacted for 10 min; the treated sediment was mechanically pressure filtered to obtain dewatered sediment with 52% moisture content, 34% antibiotic removal rate and 21% antiviral drug removal rate.

[0051] Comparative Example 3

[0052] The straw biogas residue anaerobically fermented at 35℃ for 45d was dried, ground and sieved with a 300 mesh sieve; 2 mol / L KOH solution was added to adjust the pH of the mixture to 11, and the mixture was subjected to ultrasonic treatment at a power of 100W for 3h, and then stirred at a speed of 300 rpm / min for 12h, and then centrifuged at a centrifugal speed of 3000g for 30min; the solid after centrifugation was calcined at high temperature in a tube furnace with argon as the protective gas, the pyrolysis temperature was 750℃, the heating rate was 30℃ / min, and the pyrolysis time was 5h; after cooling to room temperature, the mixture was ground and sieved with a 400 mesh sieve, washed with ethanol and deionized water several times until neutral, and then vacuum dried at 60℃ to obtain the mineral-enriched biochar;

[0053] The mineral-enriched biochar is added into a 0.5 mol / L ferrous sulfate solution, the solid-liquid ratio of the biochar and the ferrous sulfate solution is 1:18, stirring is carried out under nitrogen protection for 60 min, then a 1 mol / L sodium borohydride solution is added drop by drop, the molar ratio of the sodium borohydride and the ferrous sulfate is 4:1, and stirring is continuously carried out for 2 h, centrifugal separation is carried out, washing is carried out with deionized water until neutral, and vacuum drying is carried out at 80 DEG C, so as to obtain the nano-iron doped biochar;

[0054] The concentration of the ferrous sulfate solution is 0.4 mol / L, the solid-liquid ratio of the biochar and the ferrous sulfate solution is 1:26, the concentration of the sodium borohydride solution is 0.8 mol / L, and the molar ratio of the sodium borohydride and the ferrous sulfate is 3.5:1.

[0055] The EDC, the EAC and the EEC of the biochar are 0.528, 0.057 and 0.585 meq / e.g respectively, the number of Lewis acid sites is 33.62 μmol / g, and the catalytic activity is lower than that of the biochar prepared by mixing the biogas residue and the river and lake sediment; 200 mL of the river and lake sediment with a water content of 98% is uniformly mixed with 300 mg / gDS of the biochar, and then is put into a reactor, 50 mg / gDS of calcium peroxide is added, and reaction is carried out for 10 min, and then the treated sediment is subjected to mechanical pressure filtration, so as to obtain the dewatered sediment with a water content of 45%, an antibiotic removal rate of 52% and an antiviral drug removal rate of 40%.

[0056] Biochar electrochemical performance and acid site test experiment

[0057] Test method

[0058] Electron donation capacity (EDC), electron acceptance capacity (EAC) and electron exchange capacity (EEC) test: referring to the "Biochar electrochemical property determination method" (non-national standard method, based on the commonly used method in the literature), an electrochemical workstation (such as CHI660E) is used, a glassy carbon electrode is used as a working electrode, a platinum electrode is used as a counter electrode, and Ag / AgCl is used as a reference electrode, and the electron transfer amount is calculated by cyclic voltammetry in a 0.1 mol / L Na2SO4 electrolyte.

[0059] Lewis acid site number test: referring to the "Solid catalyst surface acidity determination method" (non-national standard method, pyridine adsorption-infrared spectroscopy method), a Fourier transform infrared spectrometer (such as Nicolet iS50) is used to measure the pyridine adsorption peak area of the biochar surface, and the number of Lewis acid sites is calculated.

[0060] The specific test data results are as follows:

[0061] Table 1

[0062]

[0063] As can be seen from Table 1, the biochar of Examples 1-3 is prepared by mixing biogas residue and river and lake sediment. The organic matter in the biogas residue provides abundant electron transfer sites, and the minerals (such as Fe2O3 and Al2O3) in the sediment increase the Lewis acid sites. Therefore, the number of EDC, EAC, EEC and Lewis acid sites is significantly higher than that of the comparative examples. Higher electron exchange capacity and acid sites can efficiently activate calcium peroxide, promote the generation of free radicals, and improve the catalytic performance.

[0064] Reasons for poor performance of comparative examples: The biochar of Comparative Examples 2 and 3 is prepared only from single biogas residue, which lacks the supplement of minerals in river and lake sediment, resulting in weak electron transfer capacity and low number of Lewis acid sites. Therefore, it cannot effectively activate calcium peroxide, and the catalytic activity is limited.

[0065] Sediment treatment effect test experiment

[0066] Test method

[0067] Moisture content test: According to GB / T 21814-2008 "Soil Testing-Determination of Soil Moisture", the treated sediment is dried at 105°C to constant weight by drying method, and the moisture content is calculated.

[0068] Antibiotic removal rate test: According to GB / T 33891-2017 "Determination of 16 Sulfonamide Antibiotics in Water by High Performance Liquid Chromatography", the concentration of antibiotics in the sediment before and after treatment is determined by high performance liquid chromatograph (such as Agilent 1260), and the removal rate is calculated.

[0069] Antiviral drug removal rate test: According to HJ 1240-2022 "Determination of Antiviral Drugs in Water by Solid Phase Extraction / High Performance Liquid Chromatography-Tandem Mass Spectrometry", the concentration before and after treatment is determined by solid phase extraction combined with liquid chromatography-tandem mass spectrometer (such as AB Sciex Triple Quad 4500), and the removal rate is calculated.

[0070] The specific test data results are as follows:

[0071] Table 2

[0072]

[0073] As can be seen from Table 2, in Examples 1-3, the biochar and calcium peroxide synergistically act: the biochar provides adsorption sites and catalytic activity, promotes the decomposition of calcium peroxide to generate free radicals, destroys the hydrophilic film of the sediment and degrades pollutants; calcium ions play a coagulation role, and biochar constructs a dehydration channel. Therefore, the moisture content after treatment is low, and the pollutant removal rate is high.

[0074] Comparative Example 1: Only calcium peroxide slowly releases hydrogen peroxide, and the generation of free radicals is insufficient in the absence of catalyst, which cannot effectively destroy the hydrophilic structure, and the moisture content is as high as 56%, and the pollutant removal rate is low.

[0075] Comparative Example 2: Only biochar adsorption is limited, and cannot oxidize and degrade pollutants, and has no coagulation aid, water content is 52%, and the pollutant removal rate is only about 34%.

[0076] Comparative Example 3: The biochar activity is insufficient, and the activation of calcium peroxide is low, resulting in lower water content and removal rate than the examples, verifying the necessity of mixing biogas residue and sediment to prepare biochar.

[0077] The preferred embodiments of the application disclosed above are only used to help illustrate the application. The preferred embodiments do not describe all the details, nor limit the application to the specific embodiments described. Obviously, many modifications and variations can be made according to the content of the specification.

Claims

1. A method for preparing a sediment-based catalyst to enhance the oxidation efficiency of calcium peroxide, characterized in that, Includes the following steps: S1. Dry, grind, and sieve the biogas residue to obtain powdered biogas residue; S2. Dry, grind, and sieve the river and lake bottom sediment to obtain powdered bottom sediment; S3. Mix powdered biogas residue and bottom mud in a certain proportion, add 2 mol / L KOH solution for activation, adjust the pH of the mixture to alkaline, sonicate, stir, centrifuge, and dry the resulting solid under vacuum at 60°C. Then, calcine and pyrolyze it in a tube furnace at high temperature. After cooling to room temperature, grind and sieve it, wash it several times with deionized water and ethanol until neutral, and dry it under vacuum at 60°C to obtain biochar rich in minerals. S4. The obtained biochar is subjected to nano-iron doping treatment to obtain nano-iron doped biochar, i.e., sediment-based catalyst.

2. The method for preparing a sediment-based catalyst with enhanced calcium peroxide oxidation efficiency according to claim 1, characterized in that, In step S1, the biogas residue is the residue after mesophilic anaerobic fermentation of straw or kitchen waste, with a fermentation temperature of 30-40℃ and a fermentation time of 30-60 days.

3. The method for preparing a sediment-based catalyst with enhanced calcium peroxide oxidation efficiency according to claim 1, characterized in that, In step S1, the biogas residue drying temperature is 70℃, and the ground biogas residue is sieved using a 100-300 mesh sieve.

4. The method for preparing a sediment-based catalyst with enhanced calcium peroxide oxidation efficiency according to claim 1, characterized in that, In step S2, the typical river and lake sediment contains mainly SiO2, Al2O3, Fe2O3 and CaO, with contents of 15-22%, 8-15%, 2-9% and 2-7% respectively, and an organic matter content of 1-10%.

5. The method for preparing a sediment-based catalyst with enhanced calcium peroxide oxidation efficiency according to claim 1, characterized in that, In step S2, the drying temperature of the river and lake bottom sediment is 70℃, and the ground river and lake bottom sediment is screened using a 100-300 mesh screen.

6. The method for preparing a sediment-based catalyst with enhanced calcium peroxide oxidation efficiency according to claim 1, characterized in that, In step S3, the ratio of powdered biogas residue to river and lake bottom sediment is 10-20:1, and the amount of KOH solution added makes the pH value of the mixture reach 9-11.

7. The method for preparing a sediment-based catalyst with enhanced calcium peroxide oxidation efficiency according to claim 1, characterized in that, In step S3, the ultrasonic power is 30-100W, the ultrasonic time is 1-3h, the stirring speed is 100-300rpm / min, the stirring time is 6-12h, the centrifugation speed is 1000-3000g, and the centrifugation time is 10-30min.

8. The method for preparing a sediment-based catalyst with enhanced calcium peroxide oxidation efficiency according to claim 1, characterized in that, In step S3, during high-temperature calcination in the tubular furnace, the pyrolysis temperature is 500-900℃, with inert gas as the protective gas, and the pyrolysis process is started at a heating rate of 10-30℃ / min and a pyrolysis time of 2-5h. The ground biochar is then sieved through a 200-400 mesh sieve.

9. The method for preparing a sediment-based catalyst with enhanced calcium peroxide oxidation efficiency according to claim 1, characterized in that, In step S4, the specific steps of the nano-iron doping treatment are as follows: biochar is added to a 0.1-0.5 mol / L ferrous sulfate solution, with a solid-liquid ratio of 1:15-18 between biochar and ferrous sulfate solution. The mixture is stirred for 30-60 min under nitrogen protection. Then, a 0.2-1 mol / L sodium borohydride solution is added dropwise, with a molar ratio of 2-4:1 between sodium borohydride and ferrous sulfate solution. The mixture is stirred for 1-2 h, centrifuged, washed with deionized water until neutral, and vacuum dried at 60-80℃ to obtain nano-iron doped biochar. The concentration of the ferrous sulfate solution is 0.2-0.4 mol / L, the solid-liquid ratio of biochar to ferrous sulfate solution is 1:20-26, the concentration of sodium borohydride solution is 0.4-0.8 mol / L, and the molar ratio of sodium borohydride to ferrous sulfate is 2.9-3.5:

1.

10. A method for preparing a sediment-based catalyst with enhanced calcium peroxide oxidation efficiency according to claim 1, characterized in that, The method of using the sediment-based catalyst is as follows: the obtained nano-iron-doped biochar is mixed evenly with river and lake sediment, placed in a reactor, and calcium peroxide is added for sediment treatment. The dosage of nano-iron-doped biochar is 100-400 mg / gDS, and the dosage of calcium peroxide is 10-100 mg / gDS.

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