CN111974395B - Red mud-based heterogeneous catalyst, preparation method and pollutant degradation method - Google Patents
Red mud-based heterogeneous catalyst, preparation method and pollutant degradation method Download PDFInfo
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Abstract
The invention discloses a red mud-based heterogeneous catalyst, a preparation method and a pollutant degradation method, belongs to the technical field of heterogeneous catalysts, and solves the problems of high catalyst cost and low degradation efficiency for degrading organic pollutants in the prior art. The red mud heterogeneous catalyst is prepared by adopting red mud and biomass carbonization reaction, and the mass ratio of the red mud to the biomass is 5:1-1:2. The preparation method comprises the steps of uniformly mixing red mud and biomass; and (3) heating and carbonizing the mixture, and sequentially cooling, cleaning and drying the reaction product to obtain the red mud heterogeneous catalyst. The degradation method is to mix the red mud heterogeneous catalyst, the organic pollutant aqueous solution and the oxidant, and stir the mixture for reaction, so that the organic pollutants in the organic pollutant aqueous solution are degraded. The red mud-based heterogeneous catalyst, the preparation method and the pollutant degradation method can be used for degrading organic pollutants.
Description
Technical Field
The invention belongs to the technical field of heterogeneous catalysts, and particularly relates to a red mud-based heterogeneous catalyst, a preparation method and a pollutant degradation method.
Background
The red mud is a strong alkaline solid waste produced by the alumina industry, and 1.0-2.5 tons of red mud can be produced per 1 ton of alumina produced, and the stockpiling amount of the red mud in China is about 4-8 hundred million tons. The red mud has fine particles, strong alkalinity and heavy metal content, and has great harm to the environment. From the perspective of resources, the red mud contains valuable metals such as iron, aluminum, titanium, rare earth and the like, but the grade of the metals is lower, the recycling economy is poorer, and the development of high-value functional materials has important significance for the comprehensive utilization of the red mud.
By utilizing the physicochemical properties of red mud, for example, the red mud contains metal elements, has large specific surface area and the like, the functional materials with high added value such as adsorbent, catalyst and the like can be prepared. The red mud is modified to prepare an adsorbent for adsorbing heavy metal ions in wastewater and soil. The red mud with strong alkalinity can be used for adsorbing sulfur dioxide in industrial waste gas, and can be used for adsorbing harmful substances in tail gas after active components are loaded by the red mud. The red mud is also widely studied as a catalyst or a catalyst carrier for biomass pyrolysis to prepare biomass energy.
Industrial wastewater and urban wastewater contain a large amount of organic pollutants, and the organic pollutants have the characteristics of difficult degradation, high toxicity and the like, so that the organic pollutants are seriously harmful to ecological environment and human health, and active free radicals with strong oxidability are generated by the reaction of the catalyst and the oxidant, so that organic pollutant molecules can be effectively degraded. However, existing catalysts for degradation of organic pollutants are relatively costly and have relatively low degradation efficiency.
Disclosure of Invention
In view of the analysis, the invention aims to provide a red mud-based heterogeneous catalyst, a preparation method and a pollutant degradation method, and solves the problems of higher cost and lower degradation efficiency of a catalyst for degrading organic pollutants in the prior art.
The aim of the invention is mainly realized by the following technical scheme:
the invention provides a red mud heterogeneous catalyst which is prepared by a carbonization reaction of red mud and biomass, wherein the mass content of ferric oxide in the red mud is 10-30%, and the mass ratio of the red mud to the biomass is 5:1-1:2.
Further, the biomass is a lignocellulosic waste biomass.
Further, the biomass is straw, wood chips, fallen leaves, bagasse, coconut shells and/or livestock manure, and the total mass content of lignin, cellulose and hemicellulose in the biomass is more than 70%.
The invention also provides a preparation method of the red mud heterogeneous catalyst, which comprises the following steps:
step 1: uniformly mixing red mud and biomass to obtain a mixture;
step 2: heating the mixture, and carrying out carbonization reaction under inert atmosphere to obtain a reaction product;
step 3: and cooling, cleaning and drying the reaction product in sequence to obtain the red mud heterogeneous catalyst.
Further, the inert atmosphere is nitrogen or argon, and the inert atmosphere is mainly used for preventing the reduced iron phase in the carbonization process from being oxidized.
Further, in the step 1, the particle size of the red mud is 0.125-0.25 mm, and the particle size of the biomass is 0.125-0.25 mm.
Further, in the step 1, the step of uniformly mixing the red mud and the biomass comprises the following steps: adding biomass into red mud for multiple times, and sieving a mixture of the biomass and the red mud after each time of adding the biomass, so that the red mud and the biomass are uniformly mixed.
Further, the pore diameter of the sieve is larger than the particle diameter of the biomass and the particle diameter of the red mud, so that all the biomass particles and the red mud particles pass through the sieve pores, and in the sieving process, the red mud particles and the biomass particles randomly pass through, so that the red mud and the biomass are uniformly mixed.
Further, the mass of biomass added each time gradually decreases.
Further, the uniformly mixing of the red mud and the biomass comprises the following steps: the biomass is divided into 10 times, the mass of the biomass added each time is 19%, 17%, 15%, 13%, 11%, 9%, 7%, 5%, 3% and 1% of the total mass of the biomass in sequence, firstly, the red mud and 19% of the biomass are mixed and screened, the undersize mixture and 17% of the biomass are mixed and screened again, and the steps are repeated until the biomass is fully added into the red mud.
Further, in the step 2, the heating temperature is 600-1000 ℃, and the heating rate of heating is 5-10 ℃/min.
Further, for hydrogen peroxide or peracetic acid systems, step 2 above includes the steps of:
step 21: heating to 150-250 ℃ at a heating rate of 5-10 ℃/min, heating the mixture once, and preserving heat for 1-2 h, wherein the acid product generated by biomass pyrolysis can neutralize the alkalinity of red mud at the stage;
step 22: heating to 800-1000 ℃ at a heating rate of 5-10 ℃/min, heating the mixture after primary heating for a second time, and preserving heat for 1-2 hours, wherein at the stage, mainly biomass is carbonized into porous biochar with benzene ring structure, and ferric oxide in red mud is reduced into a low-valence iron phase.
Further, for persulfate systems, the above step 2 includes the steps of:
heating to 800-1000 ℃ at a heating rate of 8-10 ℃/min, heating and maintaining the mixture, and preserving the temperature for 2-4 hours, so that more ferric oxide in the red mud is reduced into a low-valence iron phase at high temperature.
Further, in the step 3, the cleaning includes the following steps: and cleaning the cooled reaction product by sequentially adopting a cleaning solvent and deionized water.
Further, the cleaning solvent is one or more of methanol, ethanol and acetone mixed in any proportion.
The invention also provides a pollutant degradation method, which comprises the following steps:
step a: mixing a red mud heterogeneous catalyst, an organic pollutant aqueous solution and an oxidant;
step b: and c, stirring the mixture obtained in the step a for reaction so that the organic pollutants in the organic pollutant aqueous solution are degraded.
Further, the oxidant is hydrogen peroxide, peracetic acid or persulfate.
Further, the persulfate is ammonium persulfate, potassium persulfate, sodium persulfate or potassium monopersulfate.
Further, the organic pollutants comprise pesticides, antibiotics, dyes, polychlorinated biphenyl and/or phenolic compounds, and the concentration of the organic pollutants in the aqueous solution of the organic pollutants is 10-200 mg/L.
Further, the step a includes the steps of: adding the red mud heterogeneous catalyst into the organic pollutant water solution, stirring for 10-60 min, and adding the oxidant into the red mud heterogeneous catalyst and the organic pollutant water solution.
Further, the dosage of the red mud heterogeneous catalyst in each liter of organic pollutant aqueous solution is 0.5-5 g.
Further, the oxidant is hydrogen peroxide, and the dosage of the hydrogen peroxide is 0.02-0.2 mol in each liter of the organic pollutant aqueous solution.
Further, hydrogen peroxide is added in steps.
Further, part of hydrogen peroxide is added into the red mud heterogeneous catalyst and the organic pollutant aqueous solution, and then the rest hydrogen peroxide is added into the red mud heterogeneous catalyst and the organic pollutant aqueous solution.
Further, the oxidant is peroxyacetic acid, and the consumption of the peroxyacetic acid is 0.5-5.0 mmol in each liter of the organic pollutant water solution.
Further, the peroxyacetic acid is added in steps.
Further, part of the peracetic acid is added into the red mud heterogeneous catalyst and the organic pollutant aqueous solution, and then the rest hydrogen peroxide is added into the red mud heterogeneous catalyst and the organic pollutant aqueous solution.
Further, the oxidant is persulfate, and the consumption of the persulfate is 0.1-2.0 mmol in each liter of the organic pollutant water solution.
Further, in the step b, the stirring reaction time is 20 to 200 minutes.
Compared with the prior art, the invention has at least one of the following beneficial effects:
a) The red mud heterogeneous catalyst provided by the invention is prepared by using industrial waste residue (red mud) and waste biomass as raw materials through a co-carbonization reaction. Specifically, ferric ions in ferric oxide which is a main component of red mud are ferric ions, the catalytic activity of the ferric ions is low, and in the process of co-carbonization of the red mud and biomass, the biomass carbonization can reduce the ferric ions in part of ferric oxide into ferric ions in a low valence state, so that the catalytic activity of the red mud is improved, and the red mud heterogeneous catalyst is obtained.
b) The red mud heterogeneous catalyst provided by the invention adopts waste substances (red mud and waste biomass) as raw materials, so that the red mud heterogeneous catalyst has the characteristics of low cost, environmental friendliness and the like.
c) According to the preparation method of the red mud heterogeneous catalyst, the biomass is added into the red mud for multiple times, so that the contact probability of the biomass and the red mud can be improved, and the uniform mixing of the biomass and the red mud is promoted.
d) According to the pollutant degradation method provided by the invention, the low-valence iron in the red mud heterogeneous catalyst is utilized to react with the oxidant to generate the hydroxyl free radical or the sulfate radical with strong oxidability, so that the organic pollutants in water are oxidatively degraded, the free radical is non-selective to the degradation of the organic pollutants, the strong oxidability free radical can basically degrade most of the organic pollutants, and the mineralization degree of the organic pollutants is larger.
Additional features and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention may be realized and attained by the structure particularly pointed out in the written description and drawings.
Drawings
The drawings are only for purposes of illustrating particular embodiments and are not to be construed as limiting the invention, like reference numerals being used to refer to like parts throughout the several views.
FIG. 1 is a scanning electron microscope image of a red mud heterogeneous catalyst prepared in example 1 of the present invention;
FIG. 2 is an infrared spectrum of the heterogeneous catalyst of red mud prepared in example 1 of the present invention;
FIG. 3 is a spectrum of ultraviolet and visible spectrum of rhodamine b dye degradation of example 6 of the present invention;
FIG. 4 is a spectrum of the degradation ultraviolet visible spectrum of methylene blue dye of example 6 of the present invention.
Detailed Description
Preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings, which form a part hereof, and which together with embodiment 1 thereof serve to explain the principles of the invention.
The invention provides a red mud heterogeneous catalyst which is prepared by a carbonization reaction of red mud and biomass, wherein the mass content of ferric oxide in the red mud is 10-30%, and the mass ratio of the red mud to the biomass is 5:1-1:2.
Biomass refers to lignocellulose-based waste biomass, such as straw, wood chips, fallen leaves, bagasse, coconut shells, and/or livestock manure, and the total mass content of lignin, cellulose, and hemicellulose in the waste biomass exceeds 70%.
Compared with the prior art, the red mud heterogeneous catalyst provided by the invention is prepared by using industrial waste residues (red mud) and waste biomass as raw materials through a co-carbonization reaction. Specifically, ferric ions in ferric oxide which is a main component of red mud are ferric ions, the catalytic activity of the ferric ions is low, and in the process of co-carbonization of the red mud and biomass, the biomass carbonization can reduce the ferric ions in part of ferric oxide into ferric ions in a low valence state, so that the catalytic activity of the red mud is improved, and the red mud heterogeneous catalyst is obtained.
Taking the reaction of ferric ion and hydrogen peroxide as an example, as shown in the reaction formula, the reaction rate of ferrous ion and hydrogen peroxide is three orders of magnitude higher than that of ferric ion.
Fe 2+ +H 2 O 2 →Fe 3+ +OH - +·OH，k＝76M -1 S -1
Fe 3+ +H 2 O 2 →Fe 2+ +H + +·OOH，k＝0.02M -1 S -1
In addition, the red mud heterogeneous catalyst adopts waste substances (red mud and waste biomass) as raw materials, so that the red mud heterogeneous catalyst has the characteristics of low cost, environmental friendliness and the like.
The invention also provides a preparation method of the red mud heterogeneous catalyst, which comprises the following steps:
step 1: uniformly mixing red mud and biomass to obtain a mixture;
step 2: heating the mixture, and carrying out carbonization reaction under inert atmosphere (such as nitrogen or argon) to obtain a reaction product;
step 3: and cooling, cleaning and drying the reaction product in sequence to obtain the red mud heterogeneous catalyst.
The reaction formula involved in the preparation method is as follows:
C+Fe 2 O 3 →Fe 3 O 4 +CO
CO+3Fe 2 O 3 →2Fe 3 O 4 +CO 2
C+Fe 3 O 4 →3Fe 0 +4CO
compared with the prior art, the preparation method of the red mud heterogeneous catalyst has the advantages that the preparation method is basically the same as the preparation method of the red mud heterogeneous catalyst, and the preparation method is not repeated here.
In order to improve the catalytic activity of the red mud heterogeneous catalyst, in the step 1, the particle size of the red mud is 0.125-0.25 mm, and the particle size of the biomass is 0.125-0.25 mm. The method is characterized in that the particle sizes of the red mud and the biomass are too large, the specific surface areas of the red mud and the biomass are small, the contact of the red mud and the biomass is reduced, the carbonization reaction is insufficient, the red mud and the biomass with large particles are used as raw materials, the specific surface area of the prepared red mud heterogeneous catalyst is relatively small, and the catalytic activity is low; the particle size of the red mud and the particle size of the biomass are too small, and the prepared red mud heterogeneous catalyst is too small, so that the separation and recovery of the red mud heterogeneous catalyst are difficult in the using process. The particle sizes of the red mud and the biomass are limited in the range, so that the carbonization reaction sufficiency of the red mud and the biomass can be further increased and the catalytic activity of the red mud heterogeneous catalyst can be improved on the basis that the red mud heterogeneous catalyst can be effectively separated and recovered.
In order to achieve uniform mixing of the red mud and the biomass, in the step 1, the uniform mixing of the red mud and the biomass comprises the following steps: adding biomass into red mud for multiple times, and sieving a mixture of the biomass and the red mud after each time of adding the biomass, so that the red mud and the biomass are uniformly mixed. By adding the biomass into the red mud for multiple times, the contact probability of the biomass and the red mud can be improved, so that uniform mixing of the biomass and the red mud is promoted.
The method is characterized in that the mixture of the biomass and the red mud is sieved after the biomass is added each time, the aperture diameter of the sieve is larger than the particle size of the biomass and the particle size of the red mud, so that all the biomass particles and the red mud particles pass through the sieve aperture, and in the sieving process, the red mud particles and the biomass particles randomly pass through, so that the red mud and the biomass are uniformly mixed.
In order to further improve the mixing uniformity of the red mud and the biomass, the mass of the biomass added each time is gradually reduced according to the sequence of adding the biomass. The method is characterized in that the red mud content in the mixture is higher in the initial mixing stage, the biomass can be added to be in contact with most of the red mud to realize uniform mixing, the quality of the mixture is increased along with the mixing, the red mud content in the mixture is reduced, the adding amount of each biomass is reduced, and the mixing uniformity of the red mud and the biomass can be further improved on the basis of ensuring the mixing efficiency.
Illustratively, the uniformly mixing of red mud and biomass comprises the following steps: the biomass is divided into 10 times, the mass of the biomass added each time is 19%, 17%, 15%, 13%, 11%, 9%, 7%, 5%, 3% and 1% of the total mass of the biomass, firstly, the red mud and 19% of the biomass are mixed, the mixture is added into a 60-mesh sieve (with the mesh size of 0.25 mm) for one-time sieving, the mixture after one-time sieving and 17% of the biomass are mixed and are added into the 60-mesh sieve (with the mesh size of 0.25 mm) for the second sieving, and the steps are repeated until the biomass is completely added into the red mud, so that the mixture of the red mud and the biomass which are uniformly mixed is obtained.
In order to control the reaction rate of the carbonization reaction, in the step 2, the heating temperature is 600-1000 ℃, and the heating temperature rising rate of heating is 5-10 ℃/min.
It should be noted that the above-mentioned heterogeneous catalyst of red mud is mainly used for degradation of organic pollutants, in the degradation process of organic pollutants, it is necessary to generate free radicals by being matched with hydrogen peroxide, peracetic acid or persulfate, and for the subsequent application (hydrogen peroxide or peracetic acid), different carbonization processes are required to be performed in step 2.
Specifically, for hydrogen peroxide or peracetic acid systems, step 2 above includes the steps of:
step 21: heating to 150-250 ℃ at a heating rate of 5-10 ℃/min, heating the mixture once, and preserving heat for 1-2 h, wherein the acid product generated by biomass pyrolysis can neutralize the alkalinity of red mud at the stage;
step 22: heating to 800-1000 ℃ at a heating rate of 5-10 ℃/min, heating the mixture after primary heating for a second time, and preserving heat for 1-2 hours, wherein in the stage, mainly biomass is carbonized into porous biochar with benzene ring structure, and ferric oxide in red mud is reduced into a low-valence iron phase (ferroferric oxide or zero-valence iron).
For persulfate systems, step 2 above includes the steps of:
heating to 800-1000 ℃ at a heating rate of 8-10 ℃/min, heating and maintaining the mixture, and preserving the temperature for 2-4 hours, so that more ferric oxide in the red mud is reduced into a low-valence iron phase (ferroferric oxide or zero-valence iron) at high temperature.
In order to remove biomass pyrolysis products and soluble salts (for example, sodium salts) remained on the surface of the prepared red mud heterogeneous catalyst, the washing in the step 3 comprises the following steps: and cleaning the cooled reaction product by sequentially adopting a cleaning solvent and deionized water, wherein the cleaning solvent is one or more of methanol, ethanol and acetone which are mixed in any proportion.
The invention also provides a pollutant degradation method, which comprises the following steps:
step a: mixing a red mud heterogeneous catalyst, an organic pollutant aqueous solution and an oxidant, wherein the oxidant is one of hydrogen peroxide, peracetic acid and persulfates (such as ammonium persulfate, potassium persulfate, sodium persulfate and potassium peroxymonosulfate);
step b: and c, stirring the mixture obtained in the step a for reaction so that the organic pollutants in the organic pollutant aqueous solution are degraded.
Compared with the prior art, the beneficial effects of the pollutant degradation method provided by the invention are basically the same as those of the red mud heterogeneous catalyst, and are not described in detail herein.
In the pollutant degradation method, the low-valence iron in the red mud heterogeneous catalyst is reacted with the oxidant to generate hydroxyl free radicals or sulfate free radicals with strong oxidability, so that organic pollutants in water are oxidatively degraded, the free radicals are non-selective to the degradation of the organic pollutants, the strong-oxidability free radicals can basically degrade most of the organic pollutants, and the mineralization degree of the organic pollutants is high.
For example, the organic contaminants include pesticides, antibiotics, dyes, polychlorinated biphenyls and/or phenolic compounds, and the concentration of the organic contaminants in the aqueous solution of the organic contaminants is 10 to 200mg/L.
For the mixing sequence of the red mud heterogeneous catalyst, the organic pollutant aqueous solution and the oxidant, specifically, the step a comprises the following steps: adding the red mud heterogeneous catalyst into the organic pollutant water solution, stirring for 10-60 min, and adding the oxidant into the red mud heterogeneous catalyst and the organic pollutant water solution. This is because the red mud heterogeneous catalyst has a large specific surface area, contains porous biochar, has an adsorption effect on organic pollutants, and can effectively promote the surface catalytic degradation of the organic pollutants.
The dosage of the red mud heterogeneous catalyst is specifically 0.5-5 g per liter of organic pollutant aqueous solution. The method is characterized in that the consumption of the red mud heterogeneous catalyst is too small, the catalytic effect is poor, the consumption of the red mud heterogeneous catalyst is large, the red mud heterogeneous catalyst can consume part of active free radicals, the catalytic efficiency is reduced, and the process cost is increased due to the large consumption of the red mud heterogeneous catalyst.
Illustratively, the oxidizing agent is hydrogen peroxide, which is used in an amount of 0.02 to 0.2mol per liter of the aqueous solution of the organic contaminant. This is because the amount of hydrogen peroxide is small, the catalytic effect is poor, and the amount of hydrogen peroxide is large, and self-decomposition into water and oxygen occurs, and the substantial catalytic effect cannot be produced.
In order to further increase the amount of hydrogen peroxide, the hydrogen peroxide is added stepwise, specifically, a part of hydrogen peroxide (for example, 60% of the total mass of hydrogen peroxide) is added to the red mud heterogeneous catalyst and the organic pollutant aqueous solution, and then the rest of hydrogen peroxide is added to the red mud heterogeneous catalyst and the organic pollutant aqueous solution, so that the hydrogen peroxide utilization rate is increased.
The oxidant is peroxyacetic acid, the consumption of the peroxyacetic acid is 0.5-5.0 mmol in each liter of organic pollutant aqueous solution, the consumption of the peroxyacetic acid is small, the catalytic effect is poor, the consumption of the peroxyacetic acid is large, and the utilization efficiency of the peroxyacetic acid is low due to side reaction.
Similarly, in order to increase the utilization of the peracetic acid, the peracetic acid is added stepwise, specifically, a part of the peracetic acid (for example, 60% of the total mass of hydrogen peroxide) is added to the red mud heterogeneous catalyst and the organic pollutant aqueous solution, and then the remaining hydrogen peroxide is added to the red mud heterogeneous catalyst and the organic pollutant aqueous solution, thereby increasing the utilization of the peracetic acid.
The oxidant (hydrogen peroxide or peracetic acid) is added stepwise, a part of the oxidant (high concentration and/or large addition amount) is added to the red mud heterogeneous catalyst and the organic pollutant aqueous solution, and then the rest of the hydrogen peroxide (low concentration and/or small addition amount) is added to the red mud heterogeneous catalyst and the organic pollutant aqueous solution. Because the initial concentration of the organic pollutants in the solution is larger, more oxidant is needed to react to generate active free radicals for oxidative degradation, the concentration of the organic pollutants is obviously reduced after the reaction is carried out to a certain extent, and the oxidant with low concentration or smaller addition amount is added to fully degrade the residual organic pollutants in the solution. The oxidant is added step by step, so that the utilization rate of the oxidant can be improved, and the influence of residual oxidant in the solution after the reaction on water quality is reduced.
For example, in the prior art, the same amount of organic pollutants is degraded, the amount of the oxidant is required to be 100ml by adopting a mode of adding the oxidant in one step, and only 80ml is required by adopting a mode of adding the oxidant in steps, and the specific adding mode is as follows: 60 percent (namely 48 ml) of the total mass of the oxidant is added into the red mud heterogeneous catalyst and the organic pollutant water solution, and then 40 percent (namely 32 ml) of the total mass of the rest oxidant is added into the red mud heterogeneous catalyst and the organic pollutant water solution, so that the step-by-step addition of the oxidant is completed.
The oxidant is persulfate, and the consumption of the persulfate is 0.1-2.0 mmol in each liter of the organic pollutant water solution. This is because the amount of persulfate is small, the catalytic effect is poor, and the amount of persulfate is large, and side reactions occur, resulting in low persulfate utilization efficiency.
In order to further improve the degradation of the organic pollutants, in the step b, the stirring reaction time is 20-200 min. The stirring reaction time is limited in the range, so that the stirring reaction time can be properly shortened on the basis of ensuring the full degradation of organic pollutants, and the process running cost can be reduced.
Example 1
The particle size of the red mud adopted by the red mud heterogeneous catalyst in the embodiment is 0.125mm, the particle size of the biomass is 0.15mm, and the preparation method of the red mud heterogeneous catalyst comprises the following steps:
step 1: uniformly mixing red mud and biomass to obtain a mixture, wherein the mass ratio of the red mud to the biomass is 5:1;
step 2: heating to 200 ℃ at a heating rate of 5 ℃/min, heating the mixture once, and preserving heat for 1h; heating to 1000 ℃ at a heating rate of 10 ℃/min, carrying out secondary heating on the mixture after primary heating, and preserving heat for 1.5h to obtain a reaction product;
step 3: and (3) cooling the reaction product in sequence, cleaning by adopting ethanol and deionized water, and drying to obtain the red mud heterogeneous catalyst. The productivity of the catalyst is 83.67 percent, and the particle size of the catalyst is 0.125-0.15 mm. The catalyst has a larger specific surface area and a porous structure (see figure 1), and infrared spectroscopic analysis of the catalyst shows that the biochar has rich oxygen-containing functional groups (see figure 2), and the larger specific surface area and the oxygen-containing functional groups have a certain promotion effect on the surface adsorption of organic pollutants.
Example 2
The particle size of the red mud adopted by the red mud heterogeneous catalyst in the embodiment is 0.15mm, the particle size of the biomass is 0.25mm, and the preparation method of the red mud heterogeneous catalyst comprises the following steps:
step 1: uniformly mixing red mud and biomass to obtain a mixture, wherein the mass ratio of the red mud to the biomass is 1:1;
step 2: heating to 250 ℃ at a heating rate of 10 ℃/min, heating the mixture once, and preserving heat for 1.5h; heating to 800 ℃ at a heating rate of 8 ℃/min, carrying out secondary heating on the mixture after primary heating, and preserving heat for 2 hours to obtain a reaction product;
step 3: and (3) cooling the reaction product in sequence, cleaning by adopting methanol and deionized water, and drying to obtain the red mud heterogeneous catalyst. The productivity of the catalyst is 67.48 percent, and the particle size of the catalyst is 0.125-0.15 mm.
Example 3
The particle size of the red mud adopted by the red mud heterogeneous catalyst in the embodiment is 0.25mm, the particle size of the biomass is 0.125mm, and the preparation method of the red mud heterogeneous catalyst comprises the following steps:
step 1: uniformly mixing red mud and biomass to obtain a mixture, wherein the mass ratio of the red mud to the biomass is 1:2;
step 2: heating to 150 ℃ at a heating rate of 7 ℃/min, heating the mixture once, and preserving heat for 2 hours; heating to 920 ℃ at a heating rate of 5 ℃/min, carrying out secondary heating on the mixture after primary heating, and preserving heat for 1h to obtain a reaction product;
step 3: and (3) cooling the reaction product in sequence, cleaning by adopting ethanol and deionized water, and drying to obtain the red mud heterogeneous catalyst. The productivity of the catalyst is 58.34%, and the particle size of the catalyst is 0.125-0.15 mm.
Example 4
The particle size of the red mud adopted by the red mud heterogeneous catalyst in the embodiment is 0.23mm, the particle size of the biomass is 0.20mm, and the preparation method of the red mud heterogeneous catalyst comprises the following steps:
step 1: uniformly mixing red mud and biomass to obtain a mixture, wherein the mass ratio of the red mud to the biomass is 3:1;
step 2: heating to 980 ℃ at a heating rate of 8 ℃/min, heating and maintaining the mixture, and preserving the temperature for 2 hours to obtain a reaction product;
step 3: and (3) cooling the reaction product in sequence, cleaning by adopting ethanol and deionized water, and drying to obtain the red mud heterogeneous catalyst. The productivity of the catalyst is 81.64 percent, and the particle size of the catalyst is 0.2-0.23 mm.
Example 5
The particle size of the red mud adopted by the red mud heterogeneous catalyst in the embodiment is 0.2mm, the particle size of the biomass is 0.15mm, and the preparation method of the red mud heterogeneous catalyst comprises the following steps:
step 1: uniformly mixing red mud and biomass to obtain a mixture, wherein the mass ratio of the red mud to the biomass is 2:1;
step 2: heating to 800 ℃ at a heating rate of 10 ℃/min, heating and maintaining the mixture, and preserving the temperature for 1h to obtain a reaction product;
step 3: and (3) cooling the reaction product in sequence, cleaning by adopting ethanol and deionized water, and drying to obtain the red mud heterogeneous catalyst. The productivity of the catalyst is 57.66 percent, and the particle size of the catalyst is 0.15-0.2 mm.
Example 6
The pollutant degradation method of the embodiment adopts the red mud heterogeneous catalyst of the embodiment 1, and comprises the following steps:
step a: firstly, adding part of hydrogen peroxide into a red mud heterogeneous catalyst and an organic pollutant aqueous solution, and then adding the rest of hydrogen peroxide into the red mud heterogeneous catalyst and the organic pollutant aqueous solution, wherein the dosage of the red mud heterogeneous catalyst is 1g and the dosage of the hydrogen peroxide is 0.05mol per liter of the organic pollutant aqueous solution;
step b: and d, stirring the mixture obtained in the step a for reaction for 50min, so that the organic pollutants in the organic pollutant aqueous solution are degraded. Wherein, the degradation rate of the acid orange dye (the concentration is 10 mg/L) is 90.46%; rhodamine b dye (concentration is 10 mg/L) degradation rate is 98.79%; the degradation rate of methylene blue dye (concentration is 10 mg/L) is 99.77%; the total organic carbon removal rate is more than 78.4 percent. The maximum characteristic adsorption peaks of acid orange, rhodamine b and methylene blue dyes were significantly reduced, indicating that the dye molecules were degraded (see fig. 3-4).
Example 7
The pollutant degradation method of the embodiment adopts the red mud heterogeneous catalyst of the embodiment 1, and comprises the following steps:
step a: firstly, adding part of hydrogen peroxide into a red mud heterogeneous catalyst and an organic pollutant aqueous solution, and then adding the rest of hydrogen peroxide into the red mud heterogeneous catalyst and the organic pollutant aqueous solution, wherein the dosage of the red mud heterogeneous catalyst is 4.5g and the dosage of the hydrogen peroxide is 0.18mol per liter of the organic pollutant aqueous solution;
step b: and d, stirring the mixture obtained in the step a for reaction for 150min, so that the organic pollutants in the organic pollutant aqueous solution are degraded. The degradation rate of the tetracycline (with the concentration of 10 mg/L) is 89.86 percent, and the degradation rate of the carbamazepine (with the concentration of 10 mg/L) is 86.54 percent; the degradation rate of the methylene blue dye (the concentration is 200 mg/L) is 86.12 percent; the total organic carbon removal rate is more than 50.8 percent.
Example 8
The pollutant degradation method of this embodiment adopts the heterogeneous catalyst of red mud of embodiment 2, and the pollutant degradation method includes the following steps:
step a: firstly, adding part of peracetic acid into a red mud heterogeneous catalyst and an organic pollutant aqueous solution, and then adding the rest of hydrogen peroxide into the red mud heterogeneous catalyst and the organic pollutant aqueous solution, wherein the dosage of the red mud heterogeneous catalyst is 3.2g and the dosage of the peracetic acid is 0.8mol per liter of the organic pollutant aqueous solution;
step b: and d, stirring the mixture obtained in the step a for reaction for 200min, so that the organic pollutants in the organic pollutant aqueous solution are degraded. The degradation rate of the tetracycline (with the concentration of 10 mg/L) is 87.24 percent, and the degradation rate of the 4-chlorobiphenyl (with the concentration of 10 mg/L) is 91.24 percent; rhodamine b dye (concentration is 40 mg/L) degradation rate is 95.75%; the total organic carbon removal rate is more than 65.8 percent.
Example 9
The pollutant degradation method of this embodiment adopts the heterogeneous catalyst of red mud of embodiment 2, and the pollutant degradation method includes the following steps:
step a: firstly, adding part of peracetic acid into a red mud heterogeneous catalyst and an organic pollutant aqueous solution, and then adding the rest of hydrogen peroxide into the red mud heterogeneous catalyst and the organic pollutant aqueous solution, wherein the dosage of the red mud heterogeneous catalyst is 2.0g and the dosage of the peracetic acid is 4.5mol per liter of the organic pollutant aqueous solution;
step b: and c, stirring the mixture obtained in the step a for 30min to degrade the organic pollutants in the organic pollutant aqueous solution. The degradation rate of ofloxacin (concentration is 20 mg/L) is 96.47%; the degradation rate of ciprofloxacin (concentration is 10 mg/L) is 98.47%; the degradation rate of phenol (with the concentration of 50 mg/L) is 95.44%; the degradation rate of tribromophenol (with the concentration of 10 mg/L) is 92.15%; the total organic carbon removal rate is more than 68.34 percent.
Example 10
The pollutant degradation method of this embodiment adopts the heterogeneous catalyst of red mud of embodiment 5, and the pollutant degradation method includes the following steps:
step a: mixing a red mud heterogeneous catalyst, an organic pollutant aqueous solution and sodium persulfate, wherein the dosage of the red mud heterogeneous catalyst is 4.1g and the dosage of peracetic acid is 0.2mol in each liter of the organic pollutant aqueous solution;
step b: and c, stirring the mixture obtained in the step a for reaction for 100min, so that the organic pollutants in the organic pollutant aqueous solution are degraded. Methylene blue (concentration 80 mg/L) degradation rate is 98.27%; atrazine (concentration is 10 mg/L) degradation rate is 96.49%; the degradation rate of phenol (with the concentration of 20 mg/L) is 99.34 percent; the total organic carbon removal rate is more than 72.14 percent.
Example 11
The pollutant degradation method of this embodiment adopts the heterogeneous catalyst of red mud of embodiment 5, and the pollutant degradation method includes the following steps:
step a: mixing a red mud heterogeneous catalyst, an organic pollutant aqueous solution and ammonium persulfate, wherein the dosage of the red mud heterogeneous catalyst is 3.5g and the dosage of the peracetic acid is 1.6mol in each liter of the organic pollutant aqueous solution;
step b: and d, stirring the mixture obtained in the step a for reaction for 150min, so that the organic pollutants in the organic pollutant aqueous solution are degraded. Rhodamine b (concentration is 30 mg/L) degradation rate is 95.77%; carbamazepine (concentration 20 mg/L) degradation rate is 87.99%; the degradation rate of 4-chlorobiphenyl (concentration is 20 mg/L) is 92.67%; the total organic carbon removal rate is more than 62.94 percent.
The foregoing is only a preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any changes or substitutions easily contemplated by those skilled in the art within the technical scope of the present invention should be included in the scope of the present invention.
Claims (6)
1. The preparation method of the red mud heterogeneous catalyst used for degrading organic pollutants and matched with a hydrogen peroxide or peracetic acid system is characterized by comprising the following steps:
step 1: adding biomass into red mud for multiple times, and sieving a mixture of the biomass and the red mud after each time of adding the biomass to uniformly mix the red mud and the biomass to obtain a mixture;
the mass content of ferric oxide in the red mud is 10% -30%, and the mass ratio of the red mud to the biomass is 5:1-1:2;
the pore diameter of the sieved sieve is larger than the particle diameter of the biomass and the particle diameter of the red mud, so that all the biomass particles and the red mud particles pass through the sieve pores, and in the sieving process, the red mud particles and the biomass particles randomly pass through, so that the red mud and the biomass are uniformly mixed;
step 2: the carbonization process is as follows: heating to 150-250 ℃ at a heating rate of 5-10 ℃/min, heating the mixture once, and preserving heat for 1-2 h, wherein the acid product generated by biomass pyrolysis can neutralize the alkalinity of red mud;
heating to 800-1000 ℃ at a heating rate of 5-10 ℃/min, carrying out secondary heating on the mixture after primary heating, and preserving heat for 1-2 hours, carbonizing biomass into porous biochar with benzene ring structure, and reducing ferric oxide in red mud into a low-valence iron phase to obtain a reaction product;
step 3: cooling, cleaning and drying the reaction product in sequence to obtain a red mud heterogeneous catalyst;
the biomass is lignocellulose waste biomass, and the total mass content of lignin, cellulose and hemicellulose in the waste biomass exceeds 70%;
iron ions in ferric oxide which is a main component of the red mud are ferric ions, and in the process of the co-carbonization of the red mud and biomass, the biomass carbonization reduces the ferric ions in part of the ferric oxide into iron ions in a low valence state;
in the step 1, the particle size of the red mud is 0.125-0.25 mm, and the particle size of the biomass is 0.125-0.25 mm.
2. The method for preparing the heterogeneous catalyst of red mud for degrading organic pollutants, which is used in combination with hydrogen peroxide or peroxyacetic acid system according to claim 1, wherein in the step 1, the red mud and biomass are uniformly mixed, and the method comprises the following steps: the biomass is divided into 10 times, the mass of the biomass added each time is 19%, 17%, 15%, 13%, 11%, 9%, 7%, 5%, 3% and 1% of the total mass of the biomass in sequence, firstly, the red mud and 19% of the biomass are mixed and screened, the undersize mixture and 17% of the biomass are mixed and screened again, and the steps are repeated until the biomass is fully added into the red mud.
3. A method for degrading pollutants, characterized in that the red mud heterogeneous catalyst prepared by the preparation method of claim 1 or 2 is adopted, and the degradation method comprises the following steps:
step a: mixing a red mud heterogeneous catalyst, an organic pollutant aqueous solution and an oxidant;
step b: and c, stirring the mixture obtained in the step a for reaction so that the organic pollutants in the organic pollutant aqueous solution are degraded.
4. The pollutant degradation method according to claim 3, wherein the amount of the red mud heterogeneous catalyst used is 0.5-5 g per liter of the organic pollutant aqueous solution.
5. A contaminant degradation method according to claim 3, wherein the oxidizing agent is hydrogen peroxide or peracetic acid.
6. The pollutant degradation method according to claim 5, wherein the oxidant is hydrogen peroxide, and the amount of hydrogen peroxide is 0.02-0.2 mol per liter of the organic pollutant aqueous solution;
or the oxidant is peracetic acid, and the consumption of the peracetic acid in each liter of the organic pollutant aqueous solution is 0.5-5.0 mmol.
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