Modified biochar-based catalysts, methods of making and using the same

Abstract

The application belongs to the technical field of biochar-based catalysts, and particularly relates to a modified biochar-based catalyst and a preparation method and application thereof. The preparation method comprises the following steps: first mixing a metal salt solution and a silane hydrolysate to obtain a complex solution; and second mixing the complex solution and biomass. The preparation of the metal salt solution comprises the following steps: mixing a magnesium source and anhydrous ethanol to form a magnesium saturated solution, mixing an iron source and anhydrous ethanol to form an iron saturated solution, and mixing the magnesium saturated solution and the iron saturated solution to obtain the metal salt solution. The preparation method of the modified biochar-based catalyst provided by the application first mixes magnesium ions and iron ions with silane for first mixing, so that the magnesium ions and the iron ions are coordinated and anchored with the silane to form a complex. The formed complex can be better fixed on the surface of the biochar base, thereby increasing the active sites of the modified biochar-based catalyst, and further improving the catalytic effect of the catalyst.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of biochar-based catalysts, and particularly relates to a modified biochar-based catalyst and a preparation method and application thereof. BACKGROUND

[0002] Mineral processing wastewater (MPW) usually contains a large amount of heavy metals, residual organic flotation agents and other pollutants. Among them, arsenic (As) and antimony (Sb) with high toxicity are the most common two kinds of associated minerals in metallurgy and mining. Arsenic (As) usually exists in the form of AsO4 3- and AsO3 3- in water. AsO3 3- has higher migration ability and toxicity, and is the main arsenic form in groundwater and surface water, which has high mobility in water bodies and is difficult to remove. Antimony (Sb) mainly exists in two oxidation states in the natural environment: under aerobic conditions, it mainly exists in the form of Sb(V) (such as Sb(OH)6 - ); under anaerobic conditions, it generally exists in the form of Sb(III) (such as Sb(OH)3), and the toxicity of Sb(III) is higher than that of Sb(V). In addition, the mineral processing wastewater also contains benzylhydroxamic acid (BHA), which is a typical mineral flotation agent, and contains a benzene ring in its molecular structure, which is a refractory and toxic pollutant. The mineral processing wastewater containing BHA enters the natural water body, which makes the water body toxic and the COD concentration rise, leading to water eutrophication, seriously endangering the survival of organisms in the water body, and ultimately damaging the water environment quality and affecting the ecological balance. Therefore, the removal of As, Sb and BHA in mineral processing wastewater is the key to water regeneration and protection of the water environment.

[0003] At present, the methods for removing As and Sb in mineral processing wastewater mainly include coagulation-flocculation, adsorption, ion exchange, membrane separation and oxidation, and the methods for removing BHA mainly include biological method, natural degradation method, precipitation method and chemical oxidation method; these methods have problems such as low efficiency, high cost and limited applicability when treating compound pollution. In view of this, the advanced oxidation technology of heterogeneous persulfate system is adopted, which has the advantages of low cost, stable and long-acting and wide application range, and is considered as a very potential water pollution treatment technology. Persulfate (PDS) is a strong oxidant, which mainly generates strong oxidizing active species such as sulfate radicals (SO4 •- ) and hydroxyl radicals (•OH) to degrade organic pollutants (BHA) in water treatment. At the same time, these active species can also oxidize As(III) / Sb(III) in water into As(V) / Sb(V), thereby improving the removal efficiency of arsenic / antimony. However, its oxidation efficiency of pollutants is low at room temperature, and a catalyst needs to be used for activation. SUMMARY

[0004] To solve the above problems, the application provides a modified biochar-based catalyst and a preparation method and application thereof.The modified biochar-based catalyst has the characteristics of large specific surface area and high porosity, thereby improving the catalytic activity and adsorption capacity of the biochar-based catalyst, further activating persulfate (PDS) to efficiently remove As(III) / Sb(III) and BHA in water, and having strong safety and realizing the separation and regeneration of the material and solution after the target pollutants are oxidized and degraded.

[0005] The application is implemented by the following technical solutions:

[0006] In a first aspect, the application provides a preparation method of a modified biochar-based catalyst, comprising the following steps:

[0007] The metal salt solution and the silane hydrolysate are first mixed to obtain a complexing solution;

[0008] The complexing solution is second mixed with biomass;

[0009] The preparation of the metal salt solution comprises the following steps:

[0010] After the magnesium source is mixed with anhydrous ethanol to form a magnesium saturated solution and the iron source is mixed with anhydrous ethanol to form an iron saturated solution, the magnesium saturated solution and the iron saturated solution are mixed to obtain the metal salt solution.

[0011] In some possible implementation manners, the mass molar ratio of the biomass, the magnesium source, the iron source and the silane is 250g-300g:1mol:2mol-3mol:4mol-10mol.

[0012] In some possible implementation manners, the biomass comprises at least one of planed wood flowers, straws and wood chips.

[0013] In some possible implementation manners, the particle size of the biomass is below 160μm.

[0014] In some possible implementation manners, the magnesium source comprises at least one of magnesium chloride, magnesium sulfate and magnesium nitrate.

[0015] In some possible implementation manners, the iron source comprises at least one of iron chloride, iron sulfate and iron nitrate.

[0016] In some possible implementation manners, the silane comprises at least one of (3-methacrylamidopropyl)triethoxysilane, N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane, γ-aminopropyltriethoxysilane and urea propyl triethoxysilane.

[0017] In some possible implementation manners, the preparation of the silane hydrolysate comprises the following steps:

[0018] After mixing the silane and the anhydrous ethanol under stirring, the pH value is adjusted to 4-5 to obtain a mixture, and the stirring is continued.

[0019] In some possible implementations, in the preparation of the silane hydrolysis solution, the stirring speed is 300 rpm-500 rpm.

[0020] In some possible implementations, in the preparation of the silane hydrolysis solution, the volume concentration of the silane is 5%-10%.

[0021] In some possible implementations, in the preparation of the silane hydrolysis solution, the time for the continued stirring is 30 min-120 min.

[0022] In some possible implementations, the particle size of the biomass is 100 μm-160 μm.

[0023] In some possible implementations, the first mixing comprises the following steps:

[0024] After mixing the metal salt solution and the silane hydrolysis solution under stirring, the reaction is continued for 12 h-24 h.

[0025] In some possible implementations, in the first mixing, the stirring speed is 100 rpm-200 rpm.

[0026] In some possible implementations, the step of mixing the metal salt solution and the silane hydrolysis solution comprises: dropping the metal salt solution into the silane hydrolysis solution at a dropping speed of 10 d / min-20 d / min.

[0027] In some possible implementations, the second mixing comprises the following steps:

[0028] The mixture of the complexing solution and the biomass is subjected to constant-temperature calcination treatment under a protective gas condition;

[0029] The step of the constant-temperature calcination treatment comprises:

[0030] The constant-temperature calcination is performed after heating to the constant-temperature temperature at a heating rate of 5 °C / min-10 °C / min.

[0031] In some possible implementations, the protective gas comprises one of nitrogen, argon, and helium.

[0032] In some possible implementations, the constant-temperature temperature is 700 °C-800 °C.

[0033] In some possible implementations, the time for the constant-temperature calcination is 2 h-3 h.

[0034] In a second aspect, the application provides a modified biochar-based catalyst prepared by the preparation method, and the preparation raw materials include biomass, a magnesium source, an iron source and silane;

[0035] The mass molar ratio of the biomass, the magnesium source, the iron source and the silane is 250g-300g:1mol:2mol-3mol:4mol-10mol.

[0036] In a third aspect, the application provides an application of the modified biochar-based catalyst in waste liquid treatment, wherein the waste liquid contains at least one of As(III), Sb(III) and BHA.

[0037] The preparation method of the modified biochar-based catalyst provided by the application has at least the following beneficial technical effects compared with the prior art:

[0038] The preparation method of the modified biochar-based catalyst provided by the application first mixes magnesium ions and iron ions with silane respectively to form a complex through coordination anchoring of the magnesium ions, the iron ions and the silane, and the formed complex can be better fixed on the surface of the biochar-based catalyst, thereby increasing the active sites of the modified biochar-based catalyst and improving the catalytic effect of the catalyst.

[0039] The modified biochar-based catalyst provided by the application has at least the following beneficial technical effects compared with the prior art:

[0040] (1) The modified biochar-based catalyst provided by the application can greatly improve the activation efficiency of PDS.

[0041] (2) The modified biochar-based catalyst provided by the application has good adsorption effect while catalyzing degradation, has good magnetism, is convenient for recycling and utilization, and saves cost.

[0042] (3) The modified biochar-based catalyst provided by the application has increased surface functional groups, can transfer electrons to PDS, forms active species to oxidize and remove heavy metals while degrading organic pollutants, and reduces the treatment cost. BRIEF DESCRIPTION OF DRAWINGS

[0043] In order to more clearly illustrate the technical solutions in the embodiments of the drawings or the prior art, the drawings needed in the following embodiment or prior art description will be briefly introduced. Obviously, the drawings in the following description are only some embodiments of the drawings, and other drawings can be obtained according to the structures shown in the drawings without creative labor for those skilled in the art.

[0044] Figure 1 It is a diagram of the degradation effect of different systems on BHA in solution in the experimental example 1 of the application.

[0045] Figure 2 Figure for degradation effect of different BHA initial concentrations in MgFe-BC / PDS system in experimental example 2 of the present application;

[0046] Figure 3 Figure for degradation effect of different PDS concentrations on BHA in MgFe-BC / PDS system in experimental example 3 of the present application;

[0047] Figure 4 Figure for degradation effect of different catalyst dosages on BHA in MgFe-BC / PDS system in experimental example 4 of the present application;

[0048] Figure 5 Figure for removal effect of different systems on As(III) in solution in experimental example 5 of the present application;

[0049] Figure 6 Figure for removal effect of different As(III) initial concentrations in MgFe-BC / PDS system in experimental example 6 of the present application;

[0050] Figure 7 Figure for removal effect of different PDS concentrations on As(III) in MgFe-BC / PDS system in experimental example 7 of the present application;

[0051] Figure 8 Figure for removal effect of different catalyst dosages on As(III) in MgFe-BC / PDS system in experimental example 8 of the present application;

[0052] Figure 9 Figure for treatment effect of As(III)-BHA composite pollution in MgFe-BC / PDS system in experimental example 9 of the present application;

[0053] Figure 10 Figure for treatment effect of Sb(III)-BHA composite pollution in MgFe-BC / PDS system in experimental example 10 of the present application.

[0054] The purposes, functional features and advantages of the present application will be further described with reference to the accompanying drawings. DETAILED DESCRIPTION

[0055] In order to make the purposes, technical solutions and advantages of the present application more clear, the present application will be described and explained below with reference to the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application, and are not used to limit the present application. Based on the embodiments provided by the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of the present application.

[0056] It is apparent that the following description is merely some examples or embodiments of the present application, and for those skilled in the art, the present application can also be applied to other similar situations without creative labor. In addition, it can be understood that although the efforts made in this development process can be complex and lengthy, some design, manufacture or production changes made on the basis of the disclosed technology of the present application are only routine technical means for those skilled in the art related to the disclosed content of the present application, and should not be understood as insufficient disclosure of the disclosed content of the present application.

[0057] However, unnecessary detailed description can be omitted. For example, there are cases where detailed description of well-known matters, repeated description of substantially the same structure are omitted. This is to avoid the following description unnecessarily becoming lengthy and to facilitate understanding by those skilled in the art. In addition, the following description is provided in order for those skilled in the art to fully understand the present application, and is not intended to limit the subject matter recited in the claims.

[0058] If not specifically stated, all embodiments and optional embodiments of the present application can be combined with each other to form new technical solutions, and all technical features and optional technical features of the present application can be combined with each other to form new technical solutions.

[0059] The term "BC" refers to biochar.

[0060] The term "PDS" refers to persulfate.

[0061] The term "MgFe-BC" refers to the modified biochar catalyst provided by the embodiments of the present application.

[0062] The term "MgFe-BC / PDS" refers to the mixed system of the modified biochar catalyst and persulfate (PDS) provided by the embodiments of the present application.

[0063] At room temperature, the direct oxidation of persulfate (PDS) on pollutants is limited, and the help of carbon-based materials is needed to achieve an efficient activation process. Compared with other carbon materials, biochar shows potential in the treatment of organic pollutants by activating persulfate due to its low cost, simple preparation, wide source of raw materials, environmental protection and other characteristics, but its catalytic performance still needs to be optimized.

[0064] The ferrite spinel is loaded on the biochar (BC) for the advanced oxidation process of catalyzing persulfate (PDS), which can maximize the number of aggregated magnetic particles while improving the catalytic performance, increase the electron transfer from the metal elements to the persulfate, and accelerate the removal of pollutants. However, in the acidic environment of PDS and waste liquid, the metal elements in the catalyst are easily leached out, the active sites are lost, and the catalytic cycle is interrupted. Further, the biochar collapses due to too many defects, the specific surface area decreases, and the active site exposure is reduced.

[0065] Therefore, in order to balance the structural stability and catalytic effect, the embodiment of the present application provides a modified biochar-based catalyst and a preparation method and application thereof. The preparation method of the modified biochar-based catalyst loads magnesium and iron on the biochar in situ, improves the structural stability of the modified catalyst, and ensures the catalytic effect of the catalyst.

[0066] The following is a detailed description of a modified biochar-based catalyst and a preparation method thereof according to an embodiment of the present application.

[0067] The first aspect of the embodiment of the present application provides a preparation method of a modified biochar-based catalyst, comprising the following steps:

[0068] S10. The metal salt solution is mixed with the silane hydrolysis solution to obtain a complexing solution, and the complexing solution is mixed with the biomass for the second time.

[0069] The metal salt solution contains a magnesium source and an iron source.

[0070] The preparation method of the modified biochar-based catalyst provided by the embodiment of the present application mixes the magnesium source, the iron source and the silane to obtain a complexing solution. In the complexing solution, the magnesium ions, the iron ions and the silane are coordinated and anchored to form a complex. When the complex is mixed with the biomass, the complex can be better fixed on the surface of the biochar-based catalyst, thereby increasing the active sites of the modified biochar-based catalyst and improving the catalytic effect of the catalyst.

[0071] In some embodiments, in the above step S10, the mass molar ratio of the biomass, the magnesium source, the iron source and the silane is (250g~300g):1mol:(2mol~3mol):(4mol~10mol).

[0072] In some embodiments, in the above step S10, the biomass includes at least one of planed wood flowers, straws and wood chips.

[0073] In some embodiments, in the above step S10, the particle size of the biomass is 160μm or less.

[0074] In some embodiments, in the above step S10, the particle size of the biomass is 100μm~160μm.

[0075] In some embodiments, in the step S10, the magnesium source includes at least one of magnesium chloride, magnesium sulfate, and magnesium nitrate.

[0076] In some embodiments, in the step S10, the iron source includes at least one of iron chloride, iron sulfate, and iron nitrate.

[0077] In some embodiments, in the step S10, the silane includes at least one of (3-methacrylamidopropyl)triethoxysilane, N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, and ureidopropyltriethoxysilane.

[0078] In some embodiments, the CAS number of the (3-methacrylamidopropyl)triethoxysilane is 109213-85-6.

[0079] In some embodiments, the CAS number of the N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane is 1760-24-3.

[0080] In some embodiments, the CAS number of the γ-aminopropyltriethoxysilane is 919-30-2.

[0081] In some embodiments, the CAS number of the ureidopropyltriethoxysilane is 23779-32-0.

[0082] In some embodiments, in the step S10, the preparation of the metal salt solution includes the following steps:

[0083] S101. After the magnesium source is mixed with the anhydrous ethanol to form the magnesium saturated solution, and after the iron source is mixed with the anhydrous ethanol to form the iron saturated solution, the magnesium saturated solution and the iron saturated solution are mixed to obtain the metal salt solution.

[0084] In some embodiments, in the step S10, the preparation of the silane hydrolyzate includes the following steps:

[0085] S102. After the silane and the anhydrous ethanol are mixed under stirring, the pH value is adjusted to 4-5 to obtain a mixture, and the stirring is continued.

[0086] In the preparation of the silane hydrolyzate, after the silane and the anhydrous ethanol are mixed, the pH value is adjusted to 4-5, the acidic condition can catalyze the hydrolysis of the silane in the anhydrous ethanol to generate reactive silanol, while inhibiting the condensation between the silanols, so as to obtain a relatively stable hydrolysis product. The mixture continues to be stirred to fully hydrolyze, and finally a clear and transparent hydrolyzate is obtained.

[0087] In some embodiments, in the step S102, the stirring speed is 300 rpm to 500 rpm. In this case, the vigorous stirring can promote the hydrolysis of silane in anhydrous ethanol.

[0088] In some embodiments, in the step S102, the volume concentration of silane is 5% to 10%.

[0089] In some embodiments, in the step S102, the pH value is adjusted to 4 to 5 by using dilute hydrochloric acid.

[0090] In some embodiments, the concentration of dilute hydrochloric acid is 0.5 mol / L to 1.5 mol / L.

[0091] In some embodiments, in the step S102, the stirring time is 30 min to 120 min.

[0092] In some embodiments, in the step S10, the first mixing comprises the following steps:

[0093] S103. After mixing the metal salt solution and the silane hydrolysis solution under stirring, the reaction is continued for 12 h to 24 h.

[0094] In this case, after mixing the metal salt solution and the silane solution, the reaction is continued for 12 h to 24 h. The long-time stirring reaction (12 h to 24 h) makes the metal ions (magnesium ions, iron ions) and silane form more stable complexes.

[0095] In some embodiments, in the step S103, the stirring speed is 100 rpm to 200 rpm.

[0096] In some embodiments, in the step S103, the step of mixing the metal salt solution and the silane hydrolysis solution comprises:

[0097] S1031. The metal salt solution is dropped into the silane hydrolysis solution at a dropping speed of 10 d / min to 20 d / min.

[0098] In the step of mixing, the metal salt solution is dropped into the silane hydrolysis solution at a dropping speed of 10 d / min to 20 d / min. Slow dropping can prevent rapid precipitation or gelation caused by too high local concentration.

[0099] In some embodiments, in the step S10, the preparation of biomass comprises the following steps:

[0100] After washing, drying and crushing the biomass raw material, it is sieved.

[0101] In some embodiments, in the step S10, the second mixing comprises the following steps:

[0102] S104. The mixture of the complexing solution and the biomass is subjected to isothermal calcination treatment under a protective gas.

[0103] In some embodiments, in the step S104, the protective gas comprises one of nitrogen, argon and helium.

[0104] In some embodiments, in the step S104, the isothermal calcination treatment comprises:

[0105] S1041. After heating to the isothermal temperature at a heating rate of 5 °C / min~10 °C / min, isothermal calcination is performed.

[0106] In some embodiments, in the step S1041, the isothermal temperature is 700 °C~800 °C.

[0107] In some embodiments, in the step S1041, the isothermal calcination is performed for 2h~3h.

[0108] The second aspect of the embodiment of the present application provides a modified biochar-based catalyst prepared by the preparation method, and the preparation raw materials comprise biomass, a magnesium source, an iron source and silane.

[0109] The mass molar ratio of the biomass, the magnesium source, the iron source and the silane is (250g~300g):1mol:(2mol~3mol):(4mol~10mol).

[0110] The modified biochar-based catalyst provided by the embodiment of the present application uses silane to coordinate and anchor magnesium ions and iron ions respectively, so that the magnesium ions and the iron ions are better fixed on the surface of the biochar base, thereby increasing the active sites of the modified biochar-based catalyst, and further improving the catalytic effect of the catalyst. Moreover, the silane also provides a carbon source, and carbonizes together with the biomass to form a biochar base.

[0111] The third aspect of the embodiment of the present application provides an application of the modified biochar-based catalyst in waste liquid treatment, wherein the waste liquid contains at least one of As(III), Sb(III) and BHA.

[0112] In some embodiments, the solid-liquid ratio of the modified biochar-based catalyst to the waste liquid is (0.1~0.8g):1L.

[0113] The following will be further described in combination with specific embodiments. For the convenience of description, the preparation steps of the biomass involved below are as follows:

[0114] The planer wood flower is washed, dried, crushed and then sieved through a 100-mesh sieve to obtain biomass with a particle size of 160μm or less.

[0115] The CAS number of (3-methacrylamidopropyl)triethoxysilane is 109213-85-6.

[0116] Example 1

[0117] The preparation method of the modified biochar-based catalyst provided in the present example is as follows:

[0118] E10. Select the raw materials for preparing the modified biochar-based catalyst: planer wood flower biomass, magnesium chloride, iron chloride, and (3-methacrylamidopropyl)triethoxysilane. According to the preset mass molar ratio of planer wood flower biomass, magnesium chloride, iron chloride, and (3-methacrylamidopropyl)triethoxysilane, which is 250 g:1 mol:2 mol:4 mol, select 5 g of biomass, 0.02 mol of magnesium chloride, 0.04 mol of iron chloride, and 0.08 mol of (3-methacrylamidopropyl)triethoxysilane.

[0119] E20. Preparation of the metal salt solution: after the magnesium saturated solution is formed by mixing magnesium chloride with anhydrous ethanol, and the iron saturated solution is formed by mixing iron chloride with anhydrous ethanol, the metal salt solution is obtained by mixing the magnesium saturated solution and the iron saturated solution.

[0120] E30. Preparation of the silane hydrolysis solution: under the condition of 300 rpm stirring, after (3-methacrylamidopropyl)triethoxysilane and anhydrous ethanol are mixed, dilute hydrochloric acid is used to adjust the pH value to 4, and the mixture is obtained, and the stirring is continued for 60 min. Among them, the volume concentration of silane is 8%, and the concentration of dilute hydrochloric acid is 1.5 mol / L.

[0121] E40. First mixing: under the condition of 100 rpm stirring, the metal salt solution is dropped into the silane hydrolysis solution at a dropping speed of 10 d / min, and after mixing, the reaction is continued for 12 h to obtain the complexing solution.

[0122] E50. Second mixing:

[0123] E501. Preparation of the mixture: the planer wood flower biomass is added into the complexing solution to form the mixture.

[0124] E502. The mixture is ground uniformly.

[0125] E503. After heating to 700℃ at a heating rate of 5 °C / min under the protection of nitrogen atmosphere, the modified biochar catalyst (MgFe-BC) is obtained by constant temperature calcination for 2 h.

[0126] Example 2

[0127] The preparation method of the modified biochar-based catalyst provided in the present example is as follows:

[0128] In step E10, the silane is N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane, and the mass molar ratio of the shavings flower biomass, magnesium chloride, ferric chloride and N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane is 300 g: 1 mol: 2 mol: 8 mol, and the biomass mass is selected as 5 g, the magnesium chloride is 0.02 mol, the ferric chloride is 0.04 mol, and the N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane is 0.16 mol.

[0129] Example 3

[0130] The present embodiment provides a preparation method of the modified biochar-based catalyst provided by the present embodiment, and the steps are basically the same as those of Example 1, except that:

[0131] In step E10, the silane is γ-aminopropyltriethoxysilane, and the mass molar ratio of the shavings flower biomass, magnesium chloride, ferric chloride and γ-aminopropyltriethoxysilane is 300 g: 1 mol: 3 mol: 10 mol, and the biomass mass is selected as 5 g, the magnesium chloride is 0.02 mol, the ferric chloride is 0.06 mol, and the γ-aminopropyltriethoxysilane is 0.2 mol.

[0132] Example 4

[0133] The present embodiment provides a preparation method of the modified biochar-based catalyst provided by the present embodiment, and the steps are basically the same as those of Example 1, except that:

[0134] In step E10, the silane is urea propyl triethoxysilane, and the mass molar ratio of the shavings flower biomass, magnesium chloride, ferric chloride and urea propyl triethoxysilane is 250 g: 1 mol: 3 mol: 7 mol, and the biomass mass is selected as 5 g, the magnesium chloride is 0.02 mol, the ferric chloride is 0.06 mol, and the urea propyl triethoxysilane is 0.14 mol.

[0135] Example 5

[0136] The present embodiment provides a preparation method of the modified biochar-based catalyst provided by the present embodiment, and the steps are basically the same as those of Example 1, except that:

[0137] In step E10, the silane is urea propyl triethoxysilane, and the mass molar ratio of the shavings flower biomass, magnesium chloride, ferric chloride and urea propyl triethoxysilane is 250 g: 1 mol: 3 mol: 7 mol, and the biomass mass is selected as 5 g, the magnesium chloride is 0.02 mol, the ferric chloride is 0.06 mol, and the urea propyl triethoxysilane is 0.14 mol.

[0138] Example 6

[0139] The embodiment provides a preparation method of the modified biochar-based catalyst, and steps are basically same to those in Embodiment 1, and the difference is that:

[0140] In step E30, the stirring speed is 400 rpm, the pH value is adjusted to 5, and the continuous stirring time is 120 min.

[0141] In step E40, the stirring speed of the first mixing is 200 rpm, the dropping speed is 20 d / min, and the reaction time is 24 h.

[0142] Embodiment 7

[0143] The embodiment provides a preparation method of the modified biochar-based catalyst, and steps are basically same to those in Embodiment 1, and the difference is that:

[0144] In step E503, the temperature rising rate is 10 °C / min, the constant temperature is 800 °C, and the constant temperature calcination time is 3 h.

[0145] Comparative Example 1

[0146] Comparative Example 1 provides a preparation method of biochar (BC), and steps are as follows:

[0147] Under the condition of nitrogen protection gas, the planer wood flower biomass is heated to 700 °C at a rate of 5 °C / min, and then is naturally cooled to obtain biochar (BC).

[0148] Comparative Example 2

[0149] Comparative Example 2 provides a preparation method of magnesium ferrite (MgFe2O4), and steps are as follows:

[0150] (1) 0.04 mol FeCl3·6H2O and 0.02 mol MgCl2·6H2O are respectively dissolved in 100 mL deionized water, and are magnetically stirred at room temperature for 0.5 h. After stirring, the pH of the suspension is adjusted to 10 by using NaOH, and the solution is dried in an electric heating air drying oven at 60 °C for 4 h, and then the solid is obtained by suction filtration, and the solid is dried in an electric heating air drying oven (80 °C) until the water is completely evaporated.

[0151] (2) Under the condition of nitrogen protection gas, the temperature is raised to 700 °C at a rate of 5 °C / min, and then is naturally cooled to obtain magnesium ferrite (MgFe2O4).

[0152] In order to verify the progressiveness of the modified biochar-based catalyst and the preparation method thereof provided in the embodiments of the present application, the modified biochar-based catalyst (MgFe-BC) prepared in Example 1, the biochar (BC) prepared in Comparative Example 1 and the magnesium ferrite (MgFe2O4) prepared in Comparative Example 2 are subjected to the following experimental catalytic effect experiments.

[0153] In the following experimental examples, the concentration of As(III) / Sb(III) / BHA is detected in real time as follows:

[0154] The samples are taken at regular time intervals by using a pipette, filtered by using a 0.22 μm microporous filter, and finally the concentrations of As(III) / Sb(III) in the samples are determined by using an inductively coupled plasma mass spectrometer, and the concentration of BHA solution in the samples is determined by using a high performance liquid chromatograph.

[0155] Experimental Example 1

[0156] A BHA solution with a concentration of 10 mg / L is prepared by using deionized water, and BC, MgFe2O4 and MgFe-BC materials are added at a solid-liquid ratio of 0.4 g / L, and then 1 mM PDS is added, so as to test the degradation effects of seven different combinations of PDS, BC, MgFe2O4, MgFe-BC, BC / PDS, MgFe2O4 / PDS and MgFe-BC / PDS on BHA.

[0157] The results are shown in Table 1. Figure 1 As shown in Table 1, within 60 min, the degradation effects of BHA in different systems from large to small are as follows: MgFe-BC / PDS > BC / PDS > MgFe-BC > BC > MgFe2O4 / PDS > MgFe2O4 > PDS. In the group without adding the oxidant PDS, the degradation effect of MgFe-BC on BHA is obviously better than that of BC and MgFe2O4. It is indicated that the degradation capacity of the modified biochar catalyst provided in the present application on BHA is better than that of BC and MgFe2O4 materials. In the group with adding the oxidant persulfate PDS, MgFe-BC / PDS and BC / PDS both have excellent degradation capacity on BHA. However, the degradation rate of the MgFe-BC / PDS system is significantly higher than that of the BC / PDS system, and the complete removal of BHA can be achieved only in 10 min.

[0158] Experimental Example 2

[0159] BHA solutions with concentrations of 5 mg / L, 10 mg / L, 20 mg / L and 30 mg / L are prepared by using deionized water, MgFe-BC materials are added at a solid-liquid ratio of 0.4 g / L, and then 1 mM PDS is added, so as to test the degradation effects of BHA with different initial concentrations in the MgFe-BC / PDS system.

[0160] As shown in the results Figure 2 , the BHA degradation rate decreased with the increase of initial concentration (5 mg / L-30 mg / L). Although the target pollutant was increased to 30 mg / L, the MgFe-BC / PDS system still achieved complete degradation of BHA within 10 min, indicating that the MgFe-BC material has excellent catalytic effect.

[0161] Experimental Example 3

[0162] A BHA solution with a concentration of 10 mg / L was prepared using deionized water, and MgFe-BC was added at a solid-liquid ratio of 0.4 g / L. Then 0.5 mM, 1 mM, 2 mM and 4 mM of PDS were added respectively, and no PDS was added as a control to test the degradation effect of BHA in the MgFe-BC / PDS system with different PDS concentrations.

[0163] As shown in the results Figure 3 , compared with the PDS addition group, the degradation effect of BHA by MgFe-BC alone was weak. In the MgFe-BC / PDS system, the BHA degradation rate showed an upward trend and then decreased with the increase of PDS concentration (0 mM-4 mM), and the best concentration of PDS was 1 mM as shown in the figure.

[0164] Experimental Example 4

[0165] A BHA solution with a concentration of 10 mg / L was prepared using deionized water, and MgFe-BC was added at a solid-liquid ratio of 0.4 g / L. Then 0.5 mM, 1 mM, 2 mM and 4 mM of PDS were added respectively, and no PDS was added as a control to test the degradation effect of BHA in the MgFe-BC / PDS system with different PDS concentrations.

[0166] As shown in the results Figure 4 , when the MgFe2O4-BC material dosage increased (0.1 g / L-0.8 g / L), the BHA degradation rate in the system also increased. Increasing the concentration of MgFe-BC material can provide more active sites, thereby promoting the activation of PDS to improve the degradation efficiency of BHA. Considering the economic problem of material use, the best dosage of MgFe-BC material was 0.4 g / L as shown in the figure.

[0167] Experimental Example 5

[0168] As(III) solution with a concentration of 10 mg / L was prepared using deionized water, and BC, MgFe2O4 and MgFe-BC material were added at a solid-liquid ratio of 0.4 g / L, and then 1 mM PDS was added. The removal effect of different systems (PDS, BC, MgFe2O4, MgFe-BC, BC / PDS, MgFe2O4 / PDS and MgFe-BC / PDS) on As(III) was tested.

[0169] As shown in Figure 5 , within 60 min, the removal effect of As(III) in different systems from large to small was: MgFe-BC / PDS > MgFe-BC > MgFe2O4 / PDS > BC / PDS > MgFe2O4 > PDS > BC. Thus, it is shown that MgFe-BC has excellent catalytic effect, and in the MgFe-BC / PDS system, only 10 min is needed to achieve complete removal of As(III).

[0170] Experimental Example 6

[0171] As(III) solutions with concentrations of 1 mg / L, 3 mg / L, 5 mg / L, 7 mg / L and 10 mg / L were prepared using deionized water, and MgFe-BC material was added at a solid-liquid ratio of 0.4 g / L, and then 1 mM PDS was added. The removal effect of different initial concentrations of As(III) in the MgFe-BC / PDS system was tested.

[0172] As shown in Figure 6 , although the removal rate of As(III) slightly decreased with the increase of initial concentration (1 mg / L~10 mg / L), the MgFe-BC / PDS system still achieved complete removal of As(III) within 10 min, again proving that the MgFe-BC material has excellent catalytic effect.

[0173] Experimental Example 7

[0174] As(III) solution with a concentration of 10 mg / L was prepared using deionized water, and MgFe-BC material was added at a solid-liquid ratio of 0.4 g / L, and then 0.5 mM, 1 mM, 2 mM and 4 mM PDS were added respectively, and no PDS was added as a control. The removal effect of different PDS concentrations on As(III) in the MgFe-BC / PDS system was tested.

[0175] As shown in Figure 7As shown, MgFe-BC itself has a good removal effect on As(III), and the removal efficiency of As(III) can reach more than 90% within 60 min. In the MgFe-BC / PDS system, the removal efficiency of As(III) shows a trend of rising and then falling with the increase of PDS concentration (0 mM-4 mM), and the optimal concentration of PDS is 1 mM as shown in the figure.

[0176] Experimental Example 8

[0177] An As(III) solution with a concentration of 10 mg / L was prepared using deionized water, and 0.1 g / L, 0.2 g / L, 0.4 g / L, 0.6 g / L, and 0.8 g / L of MgFe-BC material were added to the MgFe-BC / PDS system, followed by the addition of 1 mM PDS, to test the removal effect of different MgFe-BC material dosages on As(III) in the MgFe-BC / PDS system.

[0178] As shown in the results Figure 8 , when the MgFe-BC material dosage increases (0.1 g / L-0.8 g / L), the removal efficiency of As(III) in the system also increases. When the MgFe-BC material dosage is low (0.1 g / L), the reaction system has a slower start-up rate than the high dosage group, because the material is insufficient to provide enough active sites for reaction. When the MgFe-BC material dosage is between 0.2 g / L and 0.8 g / L, As(III) can be completely removed in 5 min. Therefore, the optimal dosage of MgFe-BC material is 0.2 g / L.

[0179] Experimental Example 9

[0180] An As(III)-BHA mixed solution (1 mg / L of As(III) and 10 mg / L of BHA) was prepared using deionized water, 0.2 g / L of MgFe-BC material was added to the MgFe-BC / PDS system, and then 1 mM of PDS was added, to test the removal effect of As(III)-BHA composite pollution in the MgFe-BC / PDS system.

[0181] As shown in the results Figure 9 , the MgFe-BC / PDS system can simultaneously remove As(III) and degrade BHA in As(III)-BHA composite pollution in only 5 min, with an effect of 100%.

[0182] Experimental Example 10

[0183] Sb(III)-BHA mixed solution was prepared by using deionized water: 1 mg / L of Sb(III) and 10 mg / L of BHA, and then 0.2 g / L of MgFe-BC material was added, and 1 mM of PDS was added to test the removal effect of Sb(III)-BHA composite pollution in the MgFe-BC / PDS system.

[0184] As shown in the results Figure 10 only 5 min is needed, and the MgFe-BC / PDS system can simultaneously achieve the removal of Sb(III) and the degradation of BHA in the Sb(III)-BHA composite pollution, and the effect can reach 100%.

[0185] It should be noted that the present application is not limited to the above-mentioned embodiments. The above-mentioned embodiments are only examples, and embodiments having the same technical idea and playing the same role within the scope of the technical solution of the present application are all included in the technical scope of the present application. In addition, within the scope of the main idea of the present application, various modifications that can be thought of by those skilled in the art are applied to the embodiments, and other ways constructed by combining part of the constituent elements in the embodiments are also included in the scope of the present application.

Claims

1. A method for preparing a modified biochar-based catalyst, characterized in that, Includes the following steps: A complex solution is obtained by first mixing a metal salt solution with a silane hydrolysate; The complexing solution is then mixed with the biomass in a second process. The preparation of the metal salt solution includes the following steps: After mixing a magnesium source with anhydrous ethanol to form a magnesium saturated solution, and then mixing an iron source with anhydrous ethanol to form an iron saturated solution, the magnesium saturated solution and the iron saturated solution are mixed to obtain a metal salt solution. The mass molar ratio of the biomass, the magnesium source, the iron source, and the silane is 250g~300g:1mol:2mol~3mol:4mol~10mol; The silane includes at least one of (3-methacrylamidopropyl)triethoxysilane, N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, and ureapropyltriethoxysilane; The first mixing includes the following steps: The metal salt solution and silane hydrolysate were mixed under stirring and the reaction was continued for 12-24 hours. The second mixing includes the following steps: Under protective gas conditions, the mixture of complexing liquid and biomass is subjected to isothermal calcination treatment; wherein the isothermal temperature is 700℃~800℃.

2. The method for preparing the modified biochar-based catalyst according to claim 1, characterized in that, It satisfies at least one of the following characteristics (1) to (4): (1) The biomass includes at least one of wood shavings, straw, and sawdust; (2) The particle size of the biomass is less than 160 μm; (3) The magnesium source includes at least one of magnesium chloride, magnesium sulfate, and magnesium nitrate; (4) The iron source includes at least one of ferric chloride, ferric sulfate, and ferric nitrate.

3. The method for preparing the modified biochar-based catalyst according to claim 1 or 2, characterized in that, The preparation of the silane hydrolysate includes the following steps: Under stirring conditions, silane and anhydrous ethanol are mixed, and the pH value is adjusted to 4-5 to obtain a mixture, which is then stirred continuously.

4. The method for preparing the modified biochar-based catalyst according to claim 3, characterized in that, It satisfies at least one of the following characteristics (1) to (4): (1) In the preparation of the silane hydrolysate, the stirring speed is 300 rpm to 500 rpm; (2) In the preparation of the silane hydrolysate, the volume concentration of silane is 5%~10%; (3) In the preparation of the silane hydrolysate, the stirring time is 30 min to 120 min; (4) The particle size of the biomass is 100μm~160μm.

5. The method for preparing the modified biochar-based catalyst according to claim 1, characterized in that, It satisfies at least one of the following characteristics (1) to (2): (1) In the first mixing, the stirring speed is 100 rpm to 200 rpm; (2) The step of mixing the metal salt solution with the silane hydrolysate includes: The metal salt solution was added dropwise to the silane hydrolysate at a rate of 10d / min to 20d / min.

6. The method for preparing the modified biochar-based catalyst according to any one of claims 1, 2, 4-5, characterized in that, The constant temperature calcination process includes the following steps: Heating to a constant temperature at a heating rate of 5 °C / min to 10 °C / min, followed by constant temperature calcination.

7. The method for preparing the modified biochar-based catalyst according to claim 6, characterized in that, It satisfies at least one of the following characteristics (1) to (2): (1) The protective gas includes one of nitrogen, argon, and helium; (2) The constant temperature calcination time is 2h~3h.

8. A modified biochar-based catalyst prepared by the method of any one of claims 1 to 7.

9. The application of the modified biochar-based catalyst as described in claim 8 in wastewater treatment, characterized in that, The waste liquid contains at least one of As(III), Sb(III), and BHA.

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