A sewage treatment catalyst prepared by using biomass waste and its application

Abstract

The present invention belongs to the technical field of sewage treatment, and specifically relates to a sewage treatment catalyst prepared from biomass waste and its application. The present invention uses furfural or xylose production waste residue as a preparation raw material, and obtains nitrogen-doped activated carbon with rich structural defects through steps such as washing, carbonization, and activation. It can be used to catalyze the advanced oxidation of persulfate to treat phenol wastewater and organic dye wastewater, and can also be used as a carrier to introduce metal elements through conventional catalyst preparation processes such as physical mixing, coprecipitation, and impregnation, so that it has new catalytic properties. The preparation process of the present invention has the advantages of being environmentally friendly and is particularly suitable for sewage treatment with a high organic content. The method provided by the present invention has the advantages of environmentally friendly raw material sources, high organic pollutant degradation rate, and simple preparation process, and is particularly suitable for industrial application. The preparation method of the catalyst of the present invention is simple and low-cost, and the prepared catalyst is not only environmentally friendly but also has a long service life.

Description

Technical Field

[0001] The present invention belongs to the technical field of sewage treatment, and specifically relates to a sewage treatment catalyst prepared by utilizing biomass waste and its application, and is particularly suitable for catalyzing PDS or PMS advanced oxidation treatment of sewage with high organic or inorganic content. Background Art

[0002] In recent years, with the increasing severity of environmental pollution and the increasing prominence of water pollution, it is particularly important to develop an efficient, economical and environmentally friendly water pollution treatment technology. In response to this problem, researchers have extensively studied various new water pollution treatment technologies and materials.

[0003] Among the numerous wastewater treatment methods, catalytically activated persulfate (permonosulfate (PMS) or peroxydisulfate (PDS)) advanced oxidation treatment technology is increasingly favored by technical personnel for its advantages such as high efficiency, cleanliness, and no secondary pollution. This method can catalyze persulfate, does not produce iron sludge compared to the Fenton method, and does not require the use of hydrogen peroxide. It is currently the most ideal wastewater treatment method.

[0004] At present, the main methods for catalytic activation of persulfate include thermal activation, photoactivation, activated carbon activation and transition metal activation, all of which have important applications in various sewage treatment fields. However, there are still problems such as expensive catalyst raw materials, poor catalyst stability and low treatment efficiency.

[0005] Based on this, the present invention provides a new method for preparing a catalyst, which utilizes the production waste residue of furfural or xylose as a preparation raw material. The waste residue has been reacted to extract most of the hemicellulose and has a rich microporous structure. After washing, carbonization, activation and other steps, a stable nitrogen-doped activated carbon with a suitable pore size is obtained. The activated carbon can be used to catalyze the advanced oxidation treatment of phenol wastewater and organic dye wastewater with persulfate. It can also be used as a carrier to introduce metal elements through catalyst preparation processes such as physical mixing, co-precipitation, and impregnation, so that it has new catalytic properties and is suitable for a variety of sewage treatment scenarios. Summary of the invention

[0006] The purpose of the present invention is to provide a sewage treatment catalyst prepared from biomass waste and suitable for a variety of sewage treatment scenarios, and a preparation method thereof. The present invention uses furfural or xylose production waste residue as a preparation raw material, and obtains nitrogen-doped activated carbon with rich structural defects through steps such as cleaning, carbonization, and activation. The activated carbon can be used to catalyze the advanced oxidation treatment of phenol wastewater and organic dye wastewater with persulfate, and can also be used as a carrier to introduce metal elements through conventional catalyst preparation processes such as physical mixing, coprecipitation, and impregnation, so that it has new catalytic properties.

[0007] Furthermore, the present invention also provides the use of a sewage treatment catalyst prepared from biomass waste in catalytic degradation of water pollutants.

[0008] Based on the above purpose, the present invention adopts the following technical solutions:

[0009] A method for preparing a sewage treatment catalyst comprises the following steps:

[0010] 1) washing the carbon source raw material with water or alkaline aqueous solution and adjusting the pH to neutral;

[0011] 2) After washing the carbon source raw material obtained in step 1) again with water or alkaline aqueous solution, the carbon source raw material is mixed with the nitrogen source raw material, and the temperature is raised to a certain temperature for carbonization, and then water vapor is activated under certain temperature conditions, and then crushed, mixed and pressed into a spherical product to obtain a nitrogen-doped activated carbon catalyst for sewage treatment.

[0012] Furthermore, the alkaline aqueous solution is an aqueous solution of sodium hydroxide or potassium hydroxide.

[0013] Furthermore, the carbon source raw material in step 1) is furfural residue or xylose residue.

[0014] Furthermore, the furfural residue or xylose residue in step 1) is prepared using biomass such as corn cobs, corn stalks, wheat straw, bagasse, tea husks, cottonseed husks, rice husks, straw or sunflower husks as raw materials.

[0015] Furthermore, the alkaline aqueous solution in step 1) may be one or more of ammonia water, sodium hydroxide, sodium carbonate, sodium acetate, potassium hydroxide and potassium carbonate, with a concentration (mass fraction) of 0.01% to 50%.

[0016] Furthermore, the nitrogen source raw material in step 2) is one or more of ammonia water, ammonia gas, urea, cyanamide and dicyandiamide; based on the actual nitrogen content, the amount of nitrogen source added is 0.1 to 50% of the total weight of the carbon source raw material and the nitrogen source raw material after mixing, preferably 1 to 30%, and more preferably 10 to 15%.

[0017] Furthermore, the carbonization in step 2) is specifically performed by heating the temperature to 150-190°C at a rate of 1-3°C / min, then continuing to heat the temperature to 550-650°C at a rate of 0.5-1°C / min, and then naturally cooling the temperature to room temperature (25±5°C) after keeping the temperature for 1-3 hours.

[0018] Furthermore, the specific operation of the steam activation in step 2) is to place the carbonized product in an activation furnace, introduce steam at 800-900° C. for activation for 10-25 hours, and then naturally cool down to room temperature (25±5° C.).

[0019] Furthermore, the pressure during pressing in step 2) is 20 to 35 MPa.

[0020] Further, based on a general inventive concept, the present invention also provides a method for preparing a composite catalyst for sewage treatment loaded with non-metallic elements or metal elements, comprising the following steps:

[0021] The nitrogen-doped activated carbon catalyst prepared above is used as a carrier, and is physically mixed with non-metallic elements or metal element oxides and pressed into shape to prepare a composite catalyst loaded with non-metallic elements or metal oxides for sewage treatment.

[0022] Specifically, the metal element is one or more of the transition metal elements scandium (Sc), titanium (Ti), vanadium (V), chromium (Cr), manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), copper (Cu), and zinc (Zn), or the metal element is aluminum (Ag); the non-metal element is silicon (Si).

[0023] Specifically, the specific process parameters of physical blending and compression molding are to mix the metal element oxide and the carrier according to a certain mass ratio at room temperature (25±5°C) for 30 to 60 minutes, and then use molding equipment to press them into spherical materials at a pressure of 20 to 30 MPa.

[0024] Wherein, the mass ratio of the metal element oxide to the carrier is 1:(8-10).

[0025] Specifically, the metal element oxides include oxides of transition metal elements such as titanium dioxide, iron trioxide, cobalt trioxide, zinc oxide, manganese dioxide, copper oxide, nickel oxide, and vanadium pentoxide.

[0026] Specifically, in the prepared composite catalyst loaded with non-metallic elements or metal oxides, the mass proportion of metal elements is 0.01-70%, preferably 10%, and the mass proportion of non-precious metal elements is 1-30%, preferably 10%.

[0027] Further, based on a general inventive concept, the present invention also provides a method for preparing a composite catalyst for sewage treatment loaded with precious metal elements, comprising the following steps:

[0028] a. preparing a solution of a certain concentration of a soluble salt of a precious metal, namely a precious metal salt solution; using the nitrogen-doped activated carbon catalyst or the loaded non-metallic element or metal oxide as a carrier, and preparing a carrier aqueous solution;

[0029] b. By impregnation or precipitation, the noble metal salt solution and the carrier aqueous solution are mixed to load the noble metal element onto the nitrogen-doped activated carbon catalyst or the composite catalyst loaded with non-metallic elements or metal oxides, thereby preparing a composite catalyst loaded with noble metals for sewage treatment.

[0030] Specifically, the precious metal element in step a is one or more of platinum (Pt), palladium (Pd), ruthenium (Ru), rhodium (Rh), and iridium (Ir).

[0031] Specifically, the soluble salt of the precious metal in step a is a hydrochloride, acetate or nitrate of the precious metal, preferably a hydrochloride.

[0032] Preferably, the soluble salt of the precious metal includes chloroplatinic acid hexahydrate, palladium chloride, ruthenium trichloride, hexachlororhodium salt, and iridium chloride.

[0033] Specifically, in step a, a soluble salt of a noble metal is prepared into an aqueous solution with a concentration (mass fraction) of 10 to 15%; a carrier and water are prepared into a carrier aqueous solution in a mass ratio of 1:(8 to 10).

[0034] Specifically, in step b, the composite catalyst is prepared by an impregnation method, and the specific steps are: adjusting the pH value of the carrier aqueous solution to 1-2 with 5-10% (mass fraction) hydrochloric acid, gradually dropping the noble metal salt solution into the carrier aqueous solution at 25±5°C while stirring (the whole dropping process is 1-2h), then adjusting the pH to 11-12 with sodium hydroxide, continuing to stir the reaction for 30-60min, filtering, and preparing the composite catalyst by an impregnation method, and washing the prepared composite catalyst solid with water to pH 7-8 to obtain a composite catalyst loaded with noble metals.

[0035] Specifically, in the prepared composite catalyst loaded with precious metals, the mass proportion of precious metal elements is 0.1-5%, preferably 0.5%.

[0036] Specifically, the present invention introduces one or more of the transition metal elements scandium (Sc), titanium (Ti), vanadium (V), chromium (Cr), manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), copper (Cu), zinc (Zn), or the metal element aluminum (Ag), or the non-metal element silicon (Si), or the precious metal elements platinum (Pt), palladium (Pd), ruthenium (Ru), rhodium (Rh), iridium (Ir) One or more; thereby obtaining a persulfate capable of activating and being used for catalytic degradation of organic or inorganic pollutants in water; the introduced transition metal element, non-metal element, or precious metal element may be in the form of its organic salt or inorganic salt, or in the form of its oxide; the introduced transition metal element, non-metal element, or precious metal element may exist in its reduced state or oxidized state.

[0037] Furthermore, the present invention also provides a nitrogen-doped activated carbon catalyst prepared by the above method, a composite catalyst loaded with non-metallic elements or metal oxides, or a sewage treatment composite catalyst loaded with precious metal elements. These catalysts can be used as persulfate activators for catalytic degradation of organic pollutants or inorganic pollutants in water bodies.

[0038] Furthermore, based on a general inventive concept, the present invention also provides the use of the nitrogen-doped activated carbon catalyst, the composite catalyst loaded with non-metallic elements or metal oxides, or the composite catalyst loaded with precious metal elements as a persulfate activator in the catalytic degradation of water pollutants.

[0039] Furthermore, based on a general inventive concept, the present invention also provides the use of the nitrogen-doped activated carbon catalyst, the composite catalyst loaded with non-metallic elements or metal oxides, or the composite catalyst loaded with precious metal elements as a persulfate activator in improving sewage quality.

[0040] Specifically, the persulfate is peroxymonosulfate (PMS) or peroxydisulfate (PDS).

[0041] Specifically, the water body is domestic sewage, industrial sewage, agricultural sewage, lake water, river water or aquaculture water.

[0042] Specifically, the pollutants are one or more of pharmaceutical pollutants, phenolic compounds and dyes.

[0043] Specifically, the drug can be a steroid hormone drug, or an anti-inflammatory drug, etc.

[0044] Specifically, the phenolic compound is one or more of phenol, bisphenol A, bisphenol F and bisphenol S.

[0045] Specifically, the dye may be one or more of azo dye AO7 (acid orange AO7), rhodamine (Rh B) and methylene blue (MB).

[0046] Further, based on a general inventive concept, the present invention also provides a method for catalytically activating persulfate to degrade pollutants in water using the nitrogen-doped activated carbon catalyst, the composite catalyst loaded with non-metallic elements or metal oxides, or the composite catalyst loaded with precious metal elements, comprising the following steps:

[0047] Irradiate the water containing pollutants with ultraviolet light or visible light, add persulfate and the above catalyst, mix evenly, and then react at 20-40°C for 5min-3h to achieve the degradation of pollutants in the water.

[0048] Specifically, the pollutant may be one or more of azo dye AO7 (acid orange AO7), rhodamine (Rh B) and methylene blue (MB).

[0049] Preferably, before the degradation reaction, the pH of the water containing pollutants can be adjusted to acidic. More preferably, the pH of the water containing pollutants can be adjusted to 3.5±0.1 using sulfuric acid solution.

[0050] Specifically, the initial concentration of the pollutant is 10 to 40 mg / L.

[0051] Specifically, the persulfate is peroxymonosulfate (PMS) or peroxydisulfate (PDS).

[0052] Specifically, the initial concentration of the catalyst in the water body is 0.1-0.6 g / L.

[0053] Specifically, the initial concentration of persulfate in the water body is 0.3-0.6 g / L, or the initial concentration of persulfate in the water body is 0.1-0.6 mmol / L.

[0054] Specifically, the wavelength of the visible light is 240 nm, and the wavelength of the ultraviolet light is 254 nm.

[0055] Alternatively, as another preferred technical solution, the present invention also provides a method for catalytically activating persulfate to degrade pollutants in water using the nitrogen-doped activated carbon catalyst, the composite catalyst loaded with non-metallic elements or metal oxides, or the composite catalyst loaded with precious metal elements, comprising the following steps:

[0056] The pollutants in the water can be degraded by shaking the water at a temperature of 25 to 40°C, adding persulfate and the above catalyst, mixing evenly, and then reacting at 20 to 40°C for 10 minutes to 3 hours.

[0057] Specifically, the shaking treatment is to place the water containing pollutants in a constant temperature water bath shaker and continuously shake it at a frequency of 30 to 60 r / min.

[0058] Specifically, the pollutant may be one or more of phenol, bisphenol A, bisphenol F and bisphenol S.

[0059] Specifically, the initial concentration of the pollutant is 400-550 mg / L.

[0060] Specifically, the persulfate is peroxymonosulfate (PMS) or peroxydisulfate (PDS).

[0061] Specifically, the initial concentration of the catalyst in the water body is 0.1-0.6 g / L.

[0062] Specifically, the initial concentration of persulfate in the water body is 0.3-0.6 g / L, or the initial concentration of persulfate in the water body is 0.1-0.6 mmol / L.

[0063] Compared with the prior art, the present invention has the following advantages:

[0064] 1. The present invention uses a simple method to load organic salts, inorganic salts or oxides of the main active elements scandium, titanium, vanadium, chromium, manganese, iron, cobalt, nickel, copper, zinc, platinum, palladium, ruthenium, rhodium, iridium, etc. onto nitrogen-doped activated carbon, and simultaneously prepares a high-efficiency catalyst by physical blending, compression molding, impregnation, precipitation, etc. Since the precious metal has a plasma resonance effect, the structure of the catalytic material is optimized by changing the electron distribution in the system, thereby significantly improving the photocatalytic efficiency of the catalyst;

[0065] The sewage treatment cost per ton of the catalyst is lower than the currently commonly used sewage treatment process, and the industrialization prospect is broad. The catalyst is particularly suitable for catalytic activation of persulfate advanced oxidation to treat sewage with a high organic matter content.

[0066] 2. The composite catalyst loaded with non-metallic elements or metal element oxides, or the composite catalyst loaded with precious metal elements prepared by the present invention can perform catalytic degradation in a variety of sewage treatment scenarios. During the degradation process, visible light and ultraviolet light are used for activation, and peroxymonosulfate (PMS) or peroxydisulfate (PDS) is catalyzed to degrade sewage and has high catalyst activity.

[0067] 3. The composite catalyst prepared by the present invention, especially after the introduction of precious metals, increases the catalytic activity of the catalyst, has the characteristics of high catalytic efficiency and good stability, and the preparation process of the present invention has the advantages of being environmentally friendly, and is particularly suitable for wastewater treatment with a high organic matter content.

[0068] 4. The method provided by the present invention has the advantages of environmentally friendly raw material sources, high organic pollutant degradation rate and simple preparation process, and is particularly suitable for industrial application. The preparation method of the catalyst of the present invention is simple and low-cost, and the prepared catalyst is not only environmentally friendly but also has a long service life. DETAILED DESCRIPTION

[0069] In order to make the technical purpose, technical scheme and beneficial effects of the present invention clearer, the technical scheme of the present invention is further described below in conjunction with specific embodiments. However, the embodiments are intended to explain the present invention and cannot be understood as limiting the present invention. If no specific technology or conditions are specified in the embodiments, the technology or conditions described in the literature in the field or the product manual shall be followed.

[0070] The raw materials used in the examples are all conventional reagents, water is laboratory-made deionized water, and furfural residue is provided by Puyang Hongye Biotechnology Co., Ltd. (the furfural residue is prepared from biomass such as corn cobs, corn stalks, wheat straw, sugarcane bagasse, tea husks, cottonseed husks, rice husks, straw or sunflower husks as raw materials, and can be produced by conventional corn cob sulfuric acid acid hydrolysis method, for example, it can be prepared by the method in the book (Li Xuewen. Furfural and its basic furan derivatives [M]. Shandong University Press, 2015.2), or it can also be prepared by the method in the patent document (CN2008101410239 Method for producing furfural by clean hydrolysis of biomass) using furfural to prepare furfural residue, the furfural residue particle size is 15 to 20 mm, and the effective ingredients in the furfural residue include furfural, acetic acid, lignin and cellulose, etc.).

[0071] Example 1

[0072] This embodiment provides a method for preparing an activated carbon catalyst, and the specific steps are as follows:

[0073] Take 50g of furfural residue and add it to 100g of deionized water, add 20% (mass fraction) of sodium hydroxide aqueous solution to adjust the pH to neutral, then rinse three times with 50ml of deionized water, place it in a carbonization furnace, heat it to 170℃ at a rate of 1℃ / min, then continue to heat it to 600℃ at a rate of 0.5℃ / min, keep it for 2h and naturally cool it to room temperature (25±5℃), then transfer it to an activation furnace and activate it with water vapor at 850℃ for 15h, then naturally cool it to room temperature (25±5℃) to obtain activated carbon, then crush and mix it, and press it into a spherical product with a diameter of 0.5mm under a pressure of 30MPa, which is an activated carbon catalyst, recorded as AC-0.

[0074] Example 2

[0075] This embodiment provides a method for preparing a nitrogen-doped activated carbon catalyst, and the specific steps are as follows:

[0076] Take 50g of furfural residue and add it to 100g of deionized water, add 20% (mass fraction) of sodium hydroxide aqueous solution to adjust the pH to neutral, then rinse with 50ml of deionized water for three times, add 21.4g of urea and mix evenly, place it in a carbonization furnace, heat it to 170℃ at a rate of 1℃ / min, then continue to heat it to 600℃ at a rate of 0.5℃ / min, keep it for 2h and naturally cool it to room temperature (25±5℃), then transfer it to an activation furnace and activate it with water vapor at 850℃ for 15h, then naturally cool it to room temperature (25±5℃) to obtain nitrogen-doped activated carbon, then crush and mix it, and press it into a spherical product with a diameter of 0.5mm under a pressure of 30MPa, that is, a nitrogen-doped activated carbon catalyst, recorded as N-AC-1.

[0077] Example 3

[0078] This embodiment provides a method for preparing a nitrogen-doped activated carbon catalyst, and the specific steps are as follows:

[0079] Take 50g of furfural residue and add it to 100g of deionized water, add 20% (mass fraction) of sodium hydroxide aqueous solution to adjust the pH to neutral, then rinse three times with 50ml of deionized water, add 40.0g of aminoacetonitrile and mix evenly, place it in a carbonization furnace, heat it to 170℃ at a rate of 1℃ / min, then continue to heat it to 600℃ at a rate of 0.5℃ / min, keep it for 2h and naturally cool it to room temperature (25±5℃), then transfer it to an activation furnace and activate it with water vapor at 850℃ for 15h, then naturally cool it to room temperature (25±5℃) to obtain nitrogen-doped activated carbon, then crush and mix it, and press it into a spherical product with a diameter of 0.5mm under a pressure of 30MPa to obtain nitrogen-doped activated carbon, which is recorded as N-AC-2.

[0080] Performance Test 1

[0081] The performance of the catalysts obtained in Examples 1 to 3 in catalyzing the degradation of azo dye AO7 (Acid Orange AO7) by persulfate activated was evaluated.

[0082] Conditions for catalytic degradation of azo dye AO7 by persulfate: prepare azo dye AO7 into a 20 mg / L aqueous solution, add PMS in a molar ratio of n (permonosulfate PMS): n (azo dye AO7) = 50:1, add a catalyst at a temperature of 40°C to a concentration of 200 mg / L, adjust the pH to about 9, and detect the AO7 removal rate after 30 minutes of degradation reaction.

[0083] The comparison results are shown in Table 1 below:

[0084] Table 1

[0085] Example Catalyst No. AO7 removal rate / % Example 1 AC-0 15.2 Example 2 N-AC-1 34.7 Example 3 N-AC-2 62.6

[0086] Performance Test 2

[0087] The performance of the catalysts obtained in Examples 1 to 3 in catalyzing the treatment of phenol-containing wastewater using persulfate activated catalysts was evaluated.

[0088] The evaluation conditions are as follows: a wastewater solution with a phenol concentration of 500 mg / L is prepared, and the wastewater solution is kept in an oscillating state in a constant temperature water bath oscillator at a temperature of 25°C and a vibration frequency of 50 r / min during the degradation treatment process. The catalyst and peroxymonosulfate PMS are placed in the above wastewater solution, and the initial concentration of the catalyst is 0.15 g / L, and the initial concentration of peroxymonosulfate PMS is 0.45 g / L. The treatment time is 40 min, and the catalytic degradation temperature is 25°C. The removal rate of phenol is determined by comparing the absorbance before and after using the spectrophotometer. The results are summarized in Table 2 below:

[0089] Table 2

[0090] Example Catalyst No. Phenol removal rate / % Example 1 AC-0 78.64 Example 2 N-AC-1 81.25 Example 3 N-AC-2 81.74

[0091] From Table 1 and Table 2, it can be concluded that the catalysts prepared in Examples 1 to 3 have certain effects on activating persulfate to degrade AO7 and phenol wastewater. In particular, the addition of elemental nitrogen can significantly improve the effect of the catalyst on activating persulfate to degrade AO7. The method of Example 3 is the best choice.

[0092] Embodiments 4 to 12

[0093] A nitrogen-doped activated carbon catalyst prepared in Example 3 was selected as a carrier (no molding is required after grinding), and oxides of transition metal elements such as titanium dioxide, ferric oxide, cobalt oxide, zinc oxide, manganese dioxide, copper oxide, nickel oxide, and vanadium pentoxide were physically blended with the carrier in a mass ratio of 1:9 at room temperature (25±5°C) for 30 minutes, and then entered into a spherical molding device for compression molding at a pressure of 30 MPa to obtain a series of transition metal oxide composite catalysts, wherein the loading amount (mass fraction) of the transition metal in the transition metal oxide composite catalyst is 10%, and the catalyst number and element ratio are shown in Table 3.

[0094] Performance Test 3

[0095] UV-activated persulfate was used to degrade AO7 (acid orange AO7) and its performance was evaluated. 1 kg of 20 mg / L AO7 wastewater was taken, and the pH was adjusted to 3.5±0.1 with 1 mol / L sulfuric acid solution. The water sample was irradiated with a 254 nm UV lamp, and a catalyst and permonosulfate (PMS) were added. The initial concentration of the catalyst was 0.5 g / L, the initial concentration of permonosulfate (PMS) was 0.5 mmol / L, and the catalytic degradation temperature was 25°C. The removal rate was measured after 10 minutes of adding PMS. The results are shown in Table 3 below:

[0096] Table 3

[0097]

[0098]

[0099] It can be concluded from Table 3 that the catalyst prepared in Example 3 has a good treatment effect on the degradation of wastewater containing AO7 after loading transition metals under ultraviolet-activated PMS, especially the catalyst loaded with metal elements such as titanium, iron, cobalt, copper, and zinc.

[0100] Embodiments 13 to 18

[0101] The catalyst prepared by the method described in Examples 3 and 4 is selected as a carrier to continue to load precious metals.

[0102] The specific steps are: a soluble salt of a precious metal (such as chloroplatinic acid hexahydrate, palladium chloride, ruthenium trichloride, hexachlororhodium salt, iridium chloride) is prepared into a 10% concentration (mass fraction) aqueous solution (i.e., a precious metal salt solution), a carrier and water are prepared into an aqueous solution at a mass ratio of 1:9, and then the pH value of the carrier aqueous solution is adjusted to 1-2 with 10% (mass fraction) hydrochloric acid, and the precious metal salt solution is gradually added dropwise to the carrier aqueous solution while stirring at about 25° C. (the whole dropping process is 2 hours), and then the pH is adjusted to 11-12 with sodium hydroxide, and the reaction is continued with stirring for 60 minutes, filtered, and a composite catalyst is prepared by an impregnation method, and the prepared composite catalyst solid is washed with deionized water to pH 7-8 to obtain a series of composite catalysts loaded with precious metals, wherein the loading amount (mass fraction) of the precious metal in the composite catalyst loaded with precious metals is 0.5%, and the catalyst number and element ratio are shown in Table 4.

[0103] Performance Test 4

[0104] UV-activated persulfate was used to degrade various pollutants and the performance was evaluated. 1 kg of sewage containing pollutants (acid orange 7, rhodamine B and methylene blue) was taken, wherein the concentration of the pollutants was 20 mg / L, the pH was adjusted to 3.5±0.1 with 1 mol / L sulfuric acid solution, the water sample was irradiated with a 254 nm ultraviolet lamp, and a catalyst and permonosulfate (PMS) were added, so that the initial concentration of the catalyst was 0.5 g / L, the initial concentration of permonosulfate (PMS) was 0.5 mmol / L, the catalytic degradation temperature was 25°C, the time was counted from the addition of PMS, and the removal (color) rate was detected after sampling for 5 minutes. The results are shown in Table 4 below:

[0105] Table 4

[0106]

[0107]

[0108] It can be concluded from Table 4 that the addition of precious metals increases the absorption capacity of ultraviolet rays and greatly enhances the activation effect of persulfate. In addition, the series of precious metal-loaded composite catalysts prepared in this application activate PMS to degrade wastewater containing dyes such as AO7 and rhodamine (Rh B) or wastewater containing photosensitive dyes such as methylene blue (MB), and have good treatment effects.

[0109] It should be noted that the embodiments described above are only used to explain the present invention and do not constitute any limitation to the present invention. The present invention has been described with reference to typical embodiments, but it should be understood that the words used therein are descriptive and explanatory words, rather than restrictive words. The present invention may be modified as specified within the scope of the claims of the present invention, and the present invention may be revised without departing from the scope and spirit of the present invention. Although the present invention described therein relates to specific methods, materials and embodiments, it does not mean that the present invention is limited to the specific examples disclosed therein, on the contrary, the present invention can be extended to all other methods and applications with the same functions.

Claims

1. A method for preparing a composite catalyst loaded with non-metallic elements or metal element oxides for sewage treatment, characterized in that: The steps include: 1) Wash the carbon source raw material with water or alkaline aqueous solution and adjust the pH to neutral; 2) After washing the carbon source raw material obtained in step 1) again with water or alkaline aqueous solution, the carbon source raw material is mixed with the nitrogen source raw material, and the temperature is raised to a certain temperature for carbonization, and then water vapor is activated under a certain temperature condition, and then crushed, mixed and pressed into a spherical product to obtain a nitrogen-doped activated carbon catalyst for sewage treatment; 3) The nitrogen-doped activated carbon catalyst is used as a carrier, and is physically mixed with non-metallic elements or metal element oxides and pressed into shape to prepare a composite catalyst loaded with non-metallic elements or metal element oxides.

2. The preparation method according to claim 1, characterized in that: The carbon source raw material in step 1) is furfural residue or xylose residue; the alkaline aqueous solution in step 1) is one or more of ammonia water, sodium hydroxide, sodium carbonate, sodium acetate, potassium hydroxide and potassium carbonate, with a mass fraction of 0.01% to 50%.

3. The preparation method according to claim 1, characterized in that: The nitrogen source raw material in step 2) is one or more of ammonia water, ammonia gas, urea, cyanamide and dicyandiamide; based on the actual nitrogen content, the amount of nitrogen source added is 0.1-50% of the total weight of the carbon source raw material and the nitrogen source raw material after mixing; Step 2) The carbonization is specifically performed by heating the mixture to 150-190°C at a rate of 1-3°C / min, then heating the mixture to 550-650°C at a rate of 0.5-1°C / min, and then cooling the mixture to room temperature naturally after keeping the temperature for 1-3 hours. Step 2) The specific operation of the water vapor activation is to introduce water vapor into the carbonized product for activation at 800-900° C. for 10-25 hours, and then naturally cool it down to room temperature.

4. The preparation method according to claim 1, characterized in that: In step 3), the metal element is one or more of the transition metal elements scandium, titanium, vanadium, chromium, manganese, iron, cobalt, nickel, copper, and zinc, or the metal element is aluminum; the non-metal element is silicon; In the composite catalyst loaded with non-metallic elements or metal element oxides in step 3), the mass proportion of metal elements is 0.01 to 70%, and the mass proportion of non-precious metal elements is 1 to 30%.

5. A nitrogen-doped activated carbon catalyst for sewage treatment or a composite catalyst loaded with non-metallic elements or metal element oxides for sewage treatment prepared by the method according to any one of claims 1 to 4.

6. A method for preparing a composite catalyst loaded with precious metals for sewage treatment, characterized in that: The steps include: a. The soluble salt of a precious metal is formulated into a solution of a certain concentration, namely a precious metal salt solution; the nitrogen-doped activated carbon catalyst or the non-metallic element or metal element oxide loaded as a carrier according to claim 5, and the carrier aqueous solution is prepared; b. By impregnation or precipitation, the noble metal salt solution and the carrier aqueous solution are mixed to achieve the loading of the noble metal element onto the nitrogen-doped activated carbon catalyst or the composite catalyst loaded with non-metallic elements or metal element oxides as claimed in claim 5, to prepare a composite catalyst loaded with noble metals for wastewater treatment.

7. The preparation method according to claim 6, characterized in that: In step a, the noble metal element is one or more of platinum, palladium, ruthenium, rhodium and iridium.

8. The preparation method according to claim 6, characterized in that: In step b, in the prepared composite catalyst loaded with precious metals, the mass proportion of precious metal elements is 0.1 to 5%.

9. A composite catalyst loaded with precious metals for sewage treatment prepared by the method according to any one of claims 6 to 8.

10. Use of the nitrogen-doped activated carbon catalyst or the composite catalyst loaded with non-metallic elements or metal element oxides as claimed in claim 5 or the composite catalyst loaded with noble metals as claimed in claim 9 as a persulfate activator in catalytic degradation of water pollutants, characterized in that: The persulfate is peroxymonosulfate or peroxydisulfate; the pollutant is one or more of pharmaceutical pollutants, phenolic compounds and dyes; the phenolic compounds are one or more of phenol, bisphenol A, bisphenol F and bisphenol S; the dye is one or more of azo dye AO7, rhodamine and methylene blue.

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