CN107961811B - Supported catalyst for deeply degrading industrial dye wastewater and preparation method thereof - Google Patents
Supported catalyst for deeply degrading industrial dye wastewater and preparation method thereof Download PDFInfo
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- B01J29/04—Catalysts comprising molecular sieves having base-exchange properties, e.g. crystalline zeolites
- B01J29/041—Mesoporous materials having base exchange properties, e.g. Si/Al-MCM-41
- B01J29/045—Mesoporous materials having base exchange properties, e.g. Si/Al-MCM-41 containing arsenic, antimony, bismuth, vanadium, niobium, tantalum, polonium, chromium, molybdenum, tungsten, manganese, technetium or rhenium
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- C02F2101/00—Nature of the contaminant
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- C02F2101/308—Dyes; Colorants; Fluorescent agents
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Abstract
The invention discloses a supported catalyst for deeply degrading industrial dye wastewater and a preparation method thereof, belonging to the technical field of catalysts. The supported catalyst comprises a Fe and/or Mn supported MCM-41 mesoporous molecular sieve catalyst, and the preparation method comprises the immersion pretreatment of carrier powder and a supported active component; then preparing the metal supported catalyst by a one-step solvothermal method. The preparation process is simple, efficient, high in repeatability and easy for large-scale synthesis; meanwhile, the synergistic effect of bimetal Fe and Mn is utilized, the efficiency of oxidizing methyl orange by ozone is greatly improved, the dye wastewater methyl orange is efficiently and deeply degraded, and the reusability is good.
Description
Technical Field
The invention belongs to the technical field of catalysts, and particularly relates to a supported catalyst for deeply degrading industrial dye wastewater and a preparation method thereof, belonging to one of high-grade oxidation technologies in an industrial wastewater degradation technology.
Background
The yield of the dye industry in China is kept between 67 and 76 ten thousand tons, and the dye industry accounts for about 70 percent of the total amount of the world; the outlet amount of the dye is kept between 23 and 28 ten thousand tons. The dye industry continues to maintain a steadily growing state. The dye industry is an important component in the fields of textile, light industry, chemical industry and the like in China, and is also an industrial wastewater discharge household. The dye wastewater has the following three main characteristics that (1) the dye has large discharge amount and complex components; (2) large toxicity, large pH change and high chroma; (3) it is poor in biochemistry. Therefore, the treatment of the dye wastewater before discharge is necessary and needs to be researched and solved urgently for effective decolorization, reduction of COD and TOC values, improvement of biodegradability and reduction of residues of toxic and harmful substances.
The treatment of the dye wastewater comprises various methods, and common treatment methods comprise a Fenton chemical oxidation method, an activated carbon adsorption method, an ozone oxidation method, a catalytic oxidation method, a biological method and the like. The treatment method can be largely classified into a physical adsorption method, a chemical oxidation method and a biological method according to the treatment principle. The physical adsorption method is that porous block materials or powder and microparticles commonly used in the industry such as activated carbon, clay and the like are mixed and stirred with industrial wastewater, so that dye molecules in the wastewater are adsorbed on the surface of the porous material and are removed through filtration; the chemical oxidation method is to treat dye organic matters in the wastewater by a chemical oxidation reaction principle and a chemical oxidation method to obtain harmless reaction products or directly carry out deep treatment to completely mineralize the wastewater. Common methods of biological treatment are classified into an aerobic treatment method, an anaerobic treatment method, and a combined aerobic-anaerobic treatment method. Firstly, destroying chromophoric functional groups in the dye, and changing the concentration of target dye molecules through observation and judgment of a fading phenomenon; and secondly, carrying out deep mineralization and degradation treatment on the dye wastewater, and mainly utilizing technologies such as TOC/COD and the like to represent related mineralization degrees.
In recent years, ozone oxidation technology has been continuously studied for application to water treatment processes, such as domestic water disinfection and sterilization treatment processes and industrial wastewater advanced treatment processes. Compared with the traditional oxidation treatment mode, the ozone oxidation method has the advantages of no pollutant residue, low degree of harm to human bodies, high fading and advanced treatment efficiency, deep degree and the like, and is used for removing the dye industrial wastewater in recent years, thereby achieving remarkable effect. However, ozone oxidation still has the following problems in treating industrial wastewater: (1) the pure ozone oxidation reaction efficiency is not high, and the ozone utilization rate is low; (2) the ozone reaction catalyst is applicable to the wastewater treatment environment and is not matched with the actual industrial wastewater pH value, reaction temperature and the like; (3) the degree of mineralization of the dye wastewater during ozone oxidation treatment is not deep, and the reaction pollutant residue is difficult to treat; (4) the reaction catalyst is not high in repetition rate and reusability. The development of the technology for treating the industrial dye wastewater by ozone oxidation is severely restricted by the existence of the problems. In the preparation of industrial catalysts, a micro-nano MCM-41 powder catalyst carrier with high specific surface area and high stability is a research focus in recent years, and the powder catalyst carrier is combined with transition metal with high catalytic activity in ozone oxidation to prepare a novel supported catalyst with high use value.
Disclosure of Invention
The invention aims to solve the problem that the pure ozone oxidation reaction efficiency is not high when the dye wastewater is industrially treated; the utilization rate of ozone is low; the pH condition of the ozone reaction is severe; the degree of mineralization of the dye wastewater is low; the problems related to low repeatability and reusability of the reaction catalyst and the like are solved, and the supported catalyst for deeply degrading the industrial dye wastewater and the preparation method thereof are provided.
The invention provides a supported catalyst for deeply degrading industrial dye wastewater, which comprises a Fe-supported MCM-41 mesoporous molecular sieve catalyst, a Mn-supported MCM-41 mesoporous molecular sieve catalyst and a Fe-Mn bimetal supported MCM-41 mesoporous molecular sieve composite catalyst, wherein the MCM-41 mesoporous molecular sieve is purchased from Nanjing Xiancheng nanometer material company, the pore diameter of the MCM-41 mesoporous molecular sieve is 3-5nm, and the specific surface area is more than 800m2/g。
The invention also provides a preparation method of the supported catalyst for deeply degrading the industrial dye wastewater, which adopts an improved one-step solvothermal method and comprises the steps of pretreatment for early-stage impregnation, mixing, stirring and adsorption, surface loading by the solvothermal method and drying preparation, and the preparation method specifically comprises the following steps:
firstly, carrying out impregnation pretreatment on carrier powder and loaded active components;
firstly, placing MCM-41 mesoporous molecular sieve (hereinafter, referred to as MCM-41 or molecular sieve) powder in an ethanol solution for ultrasonic oscillation so as to be beneficial to full separation and uniform distribution of molecular sieve powder and reduce agglomeration phenomenon as much as possible to obtain a solution A with uniformly distributed molecular sieves; and simultaneously dissolving Fe and/or Mn precursor powder in high-purity water for ultrasonic oscillation to obtain a solution B containing a Fe source and/or a Mn source.
Then, the solution a and the solution B were mixed and stirred, and sufficiently stirred for 24 hours under magnetic stirring, to obtain a mixed solution C. Simultaneously mixing concentrated ammonia water and high-purity water in proportion and ultrasonically vibrating for 5min to obtain an ammonia water solution D; dropwise adding the aqueous ammonia solution D into the mixed solution C by using a separating funnel, keeping the mixture fully stirred, and continuing stirring for 1 hour after the aqueous ammonia solution D is completely added to obtain a mixed solution E.
The concentrated ammonia water used in the above steps is a commercial ammonia water solution with a mass percent concentration of 25%.
Secondly, preparing a metal supported catalyst by a one-step solvothermal method;
transferring the mixed solution E into a hydrothermal reaction kettle, carrying out solvothermal reaction in an oven A for 8 hours, after the solution is cooled, transferring the solution in the hydrothermal reaction kettle into a centrifugal tube, carrying out centrifugal treatment, and pouring out supernatant in the centrifugal tube to obtain a precipitate F; and (3) centrifuging and washing the precipitate F for several times by using high-purity water and ethanol respectively until the pH value of a supernatant is higher than 5, and considering that the prepared Fe and/or Mn metal-loaded molecular sieve is not loaded with other ions basically to obtain a precipitate G. And transferring the precipitate G into a watch glass, placing the watch glass in an oven B for drying to obtain the supported catalyst, and placing the supported catalyst in a dryer for storage under a drying condition for later use.
In the second step, the temperature of an oven A used by the solvothermal method is 180 ℃; the temperature of oven B when drying precipitate G was 80 deg.C, and kept drying for 12 hours.
The solution A is prepared according to the proportion that 1.000g of molecular sieve powder is added into each 20mL of ethanol. The volume of the high-purity water in the solution B is the same as that of the ethanol in the solution A; adding Fe source and/or Mn source precursor powder into the solution B according to the following mass ratio:
M(Fe)：m(MCM-41)＝10:100，m(Mn)：m(MCM-41)＝5：100。
wherein m (Fe) represents the mass of the Fe source precursor powder, m (Mn) represents the mass of the Mn source precursor powder, and m (MCM-41) represents the mass of the MCM-41 powder in the solution A.
The Fe source precursor powder selects a medicine Fe (NO)3)3·9H2O, the Mn source precursor powder selects Mn (CH)3COO)2·H2O。
The ammonia water solution D is prepared from concentrated ammonia water: high purity water 1.5 mL: 8.5 mL.
The invention has the advantages that:
(1) the invention selects the MCM-41 mesoporous molecular sieve as the growth substrate of the active groups of Fe and Mn, can obviously improve the specific surface area of the prepared supported catalyst, is beneficial to the uniform dispersion of the active groups of Fe and Mn, and achieves the aims of fully utilizing ozone molecules and deeply degrading methyl orange. Meanwhile, the chemical component of the MCM-41 mesoporous molecular sieve is SiO2The structure is stable, and the catalyst is a novel catalyst.
(2) The invention adopts a one-step solvothermal method to prepare the metal loaded MCM-41 mesoporous molecular sieve catalyst, has simple preparation process, high efficiency and high repeatability, and is easy for large-scale synthesis. Meanwhile, the synergistic effect of bimetal Fe and Mn is utilized, the efficiency of oxidizing methyl orange by ozone is greatly improved, and the dye wastewater methyl orange is efficiently and deeply degraded.
(3) When the Fe and Mn bimetallic loaded MCM-41 mesoporous molecular sieve catalyst obtained by the invention is used for carrying out a catalytic ozone oxidation methyl orange experiment, the TOC percentage of the high-concentration MO wastewater with initial TOC of 168mg/L can be degraded to 77.5% in 150min, and is improved by 33.9% compared with the TOC percentage of pure ozone oxidation degradation. The catalyst provided by the invention can keep fading of 1mM methyl orange solution within 50min in three times of cyclic use, and has good reusability.
Drawings
FIG. 1a is an SEM image of an iron and manganese bimetallic mixed oxide catalyst prepared in example 4;
FIG. 1b is an SEM image of a pure MCM-41 type mesoporous molecular sieve;
FIG. 1c is an SEM image of an iron and manganese bimetallic supported catalyst prepared in example 1 of the present invention;
FIG. 2a is a TEM image of a bimetallic supported catalyst prepared in example 1;
FIG. 2b is a TEM image of a pure molecular sieve;
FIG. 3a illustrates α -Fe prepared in example 52O3Metal oxide catalyst and Standard card α -Fe2O3XRD contrast pattern of (a);
FIG. 3b shows Mn as prepared in example 63O4Metal oxide catalyst and standard Mn3O4XRD contrast pattern of (a);
FIG. 3c shows Fe/MCM-41 prepared in example 2 and α -Fe prepared in example 52O3And XRD contrast of pure MCM-41;
FIG. 3d shows Mn/MCM-41 from example 3 and Mn from example 63O4And XRD contrast of pure MCM-41;
FIG. 3e is a XRD contrast of MCM-41, Fe/MCM-41, Mn/MCM-41, Fe-Mn/MCM-41;
FIG. 4 is a graph showing the relationship between the change in the concentration of methyl orange influenced by each catalyst and the reaction time under the same experimental conditions for the catalytic performance test;
FIG. 5 is a comparative graph of tests for degrading methyl orange by selecting different amounts of Fe-Mn/MCM-41 catalysts under the same experimental conditions;
FIG. 6 is a graph of a reuse test profile for a Fe-Mn/MCM-41 catalyst;
FIG. 7 is a graph showing the efficiency of catalytic ozone oxidation degradation of methyl orange under different initial reaction pH conditions with a catalyst addition of 1.0 g/L;
fig. 8 under experimental conditions: the oxygen flow flux is 20mL/min, and the ozone test concentration is: 34.8mg/L, the addition amount of the catalyst is 1.0g/L, the initial pH is 5.0, and the Fe-Mn/MCM-41 catalyst, the pure ozone catalyst and the catalyst with the mass ratio of 2: comparative graph of TOC change of reaction of degrading methyl orange solution by Fe/MCM-41 and Mn/MCM-41 mixed catalyst of 1.
Detailed Description
The present invention will be described in further detail with reference to the accompanying drawings and examples.
The invention provides a supported catalyst for deeply degrading industrial dye wastewater and a preparation method thereof, wherein the catalyst comprises a Fe and Mn double transition metal loaded MCM-41 mesoporous molecular sieve catalyst, a Fe loaded MCM-41 mesoporous molecular sieve catalyst and a Mn loaded MCM-41 mesoporous molecular sieve catalyst, and the preparation method comprises the following steps:
firstly, carrying out impregnation pretreatment on carrier powder and loaded active components;
placing molecular sieve powder in an ethanol solvent for ultrasonic oscillation to obtain a solution A; the volume-mass ratio of the ethanol to the molecular sieve is 20 mL: 1g of the total weight of the composition.
Fe source and Mn source precursor Fe (NO)3)3·9H2O and Mn (CH)3CO2)2·H2And dissolving O in high-purity water simultaneously or respectively according to the proportion, and performing ultrasonic oscillation to obtain a solution B. Wherein m (Fe): m (MCM-41) 10:100, m (mn): m (MCM-41) ═ 5: 100. m (Fe) represents the mass of the Fe source precursor powder, m (Mn) represents the mass of the Mn source precursor powder, and m (MCM-41) represents the mass of the MCM-41 powder in the solution A. The volume of high purity water was equal to the volume of ethanol in solution a.
And mixing and stirring the solution A and the solution B, and fully stirring for 24 hours under the magnetic stirring to obtain a mixed solution C.
1.5mL of concentrated ammonia water and high-purity water in a volume ratio of 1.5 mL: 8.5mL of the mixture was mixed and subjected to ultrasonic oscillation for 5min to obtain an ammonia solution D.
Dropwise adding the aqueous ammonia solution D into the mixed solution C by using a separating funnel, keeping the mixed solution fully stirred, and continuing stirring for 1 hour after completely adding the aqueous ammonia solution D to obtain a mixed solution E.
The strong ammonia water is a commercial ammonia water solution with the mass percentage concentration of 25%.
Secondly, preparing a supported catalyst by a one-step solvothermal method;
transferring the mixed solution E into a hydrothermal reaction kettle, carrying out solvothermal reaction in an oven A at 180 ℃ for 8 hours, after the solution is cooled, transferring the solution in the hydrothermal reaction kettle into a centrifugal tube, carrying out centrifugal treatment, and pouring out supernatant in the centrifugal tube to obtain a precipitate F; and (3) centrifuging and washing the precipitate F for several times by using high-purity water and ethanol respectively until the pH value of the supernatant is higher than 5, loading Fe and/or Mn on a molecular sieve without loading other ions, and pouring out the supernatant to obtain a precipitate G.
And transferring the precipitate G into a watch glass, and drying in an oven B at 80 ℃ for 12 hours to obtain the supported catalyst. And placing the obtained supported catalyst in a dryer for storage under a dry condition for later use.
A laboratory-scale self-built ozone reaction device is adopted to test the catalytic performance of metal loaded MCM-41 mesoporous molecular sieve for catalytic ozone oxidation degradation of MO methyl orange, the selected ozone generation device is a 3S-A10 type ozone generator of Beijing Tonglin scientific and technological company, the ozone reaction device is a glass columnar reactor, and the size specification is that
And meanwhile, the ozone concentration monitoring device is connected with a real-time monitoring ozone concentration monitor made by Guangzhou Limei science and technology company, and the model of the ozone concentration monitoring device is UV 300B. The reaction process is as follows: the catalyst of the present invention and several comparative example catalyst powders prepared above were dispersed and dissolved in 150mL of wastewater containing methyl orange, and uniformly dispersed by ultrasonic. And then putting the wastewater containing the catalyst into a columnar reactor, and carrying out a test on the catalytic efficiency and an advanced treatment experiment of the catalytic ozone oxidation of methyl orange under the condition of the same operating parameters. Specific examples are given below.
Example 1:preparation of Fe-Mn/MCM-41 catalyst:
firstly, a carrier powder and an active component loaded impregnation pretreatment process;
weighing 1.0g of molecular sieve in a 50mL beaker A, adding 20mL of pure ethanol into the beaker A, stirring with a glass rod to uniformly distribute the molecular sieve, performing ultrasonic oscillation for 5min,solution a was obtained. Simultaneously weighing Fe (NO)3)3·9H2O powder medicine 482.68mg and Mn (CH)3COO)2·H2Placing 222.81mg of O powder medicine into a 50mL beaker B, adding 20mL of high-purity water into the beaker B, stirring the powder medicine by a glass rod to fully dissolve the powder medicine, and carrying out ultrasonic oscillation for 5min to obtain a solution B. And mixing the solution A and the solution B in a 100ml beaker C, and performing magnetic stirring for 24 hours to ensure that Fe and Mn ions are fully adsorbed on the surface of the MCM-41 mesoporous molecular sieve to obtain a mixed solution C. 1.5mL of concentrated ammonia water and 8.5mL of high-purity water are selected and mixed to obtain an ammonia water solution D, and the ammonia water solution D is added into the mixed solution C dropwise after stirring is finished and is mixed with Fe adsorbed on the surface of the molecular sieve3+And Mn2+And (3) reacting to obtain Fe oxide and hydroxide and Mn oxide and hydroxide which are adsorbed on the surface of the molecular sieve, and continuously stirring for one hour after the ammonia water solution D is completely added to keep the uniform distribution of the molecular sieve powder in the solution, thereby obtaining a mixed solution E.
The concentrated ammonia water used in the above steps is a commercial ammonia water solution with the mass percentage of 25%.
Secondly, preparing a Fe and Mn bimetal supported catalyst by a one-step solvothermal method;
and transferring the mixed solution E into a hydrothermal reaction kettle, putting the mixed solution into an oven A to perform a solvothermal reaction for 8 hours, wherein the solvothermal reaction temperature is 180 ℃. And after the reaction is finished, taking the hydrothermal reaction kettle out of the oven A and cooling the hydrothermal reaction kettle in air for about two hours. And after the solution is cooled, transferring the solution in the hydrothermal reaction kettle into a centrifugal tube for centrifugal treatment, centrifuging at the speed of 5000rpm for 5min, and pouring out the supernatant in the centrifugal tube to obtain a precipitate F. And then centrifuging and washing the precipitate F with high-purity water and ethanol for three times respectively, wherein the prepared Fe and Mn bimetallic loaded MCM-41 mesoporous molecular sieve is considered to be basically free of other ions, and thus obtaining a precipitate G. And transferring the precipitate G into a watch glass, placing the watch glass in an oven B for drying (80 ℃ and 12 hours) to obtain the bimetallic supported catalyst, and placing the bimetallic supported catalyst in a dryer for storage under a drying condition for later use.
Example 2:preparation of Fe/MCM-41 catalyst:
firstly, a carrier powder and an active component loaded impregnation pretreatment process;
weighing 1.0g of MCM-41 mesoporous molecular sieve in a 50mL beaker, adding 20mL of pure ethanol into the beaker, stirring with a glass rod to uniformly distribute the molecular sieve, and performing ultrasonic oscillation for 5min to obtain a solution A. Weighing Fe (NO)3)3·9H2Placing 482.68mg of O powder medicine into a 50mL beaker, adding 20mL of high-purity water into the beaker, stirring the powder medicine by a glass rod to be fully dissolved, and carrying out ultrasonic oscillation for 5min to obtain a solution B. And mixing the solution A and the solution B in a 100ml beaker, and performing magnetic stirring for 24 hours to ensure that Fe ions are fully adsorbed on the surface of the MCM-41 mesoporous molecular sieve to obtain a mixed solution C. Preparing 1.5mL of concentrated ammonia water: 8.5mL of highly pure aqueous ammonia solution D, after stirring, dropwise adding the aqueous ammonia solution D into the mixed solution C, and mixing with Fe adsorbed on the surface of the molecular sieve3+And (3) adsorbing the oxide and the hydroxide of Fe obtained by reaction on the surface of the MCM-41 mesoporous molecular sieve, and continuously stirring for one hour after the ammonia water solution D is completely added to keep the uniform distribution of the molecular sieve powder in the solution, thereby obtaining a mixed solution E.
The concentrated ammonia used in the above step was a commercial 25 wt.% aqueous ammonia solution.
In the second step, a Fe metal-supported catalyst was obtained in the same manner as in example 1.
Example 3:preparation of Mn/MCM-41 catalyst:
firstly, a carrier powder and an active component loaded impregnation pretreatment process;
weighing 1.0g of MCM-41 mesoporous molecular sieve in a 50mL beaker, adding 20mL of pure ethanol solution into the beaker, stirring the molecular sieve by a glass rod to be uniformly distributed, and performing ultrasonic oscillation for 5min to obtain a solution A. Simultaneously weighing Mn (CH)3COO)2·H2Placing 222.81mg of O powder medicine into a 50mL beaker, adding 20mL of high-purity water into the beaker, stirring the powder medicine by a glass rod to be fully dissolved, and carrying out ultrasonic oscillation for 5min to obtain a solution B. And mixing the solution A and the solution B in a 100mL beaker, and performing magnetic stirring for 24 hours to ensure that Mn ions are fully adsorbed on the surface of the MCM-41 mesoporous molecular sieve. The preparation proportion is 1.5mL of concentrated ammonia water: 8.5mL of highly purified aqueous ammonia solution D, ammonia was added after completion of the stirringDropwise adding the aqueous solution D into the mixed solution C, and reacting with Mn adsorbed on the surface of the molecular sieve2+And (3) adsorbing Mn oxide and hydroxide on the surface of the MCM-41 mesoporous molecular sieve through reaction, and continuously stirring for one hour after the ammonia water solution D is completely added to keep the uniform distribution of molecular sieve powder in the solution to obtain a mixed solution E.
The concentrated ammonia used in the above step was a commercial 25 wt.% aqueous ammonia solution.
In the second step, a Mn metal supported catalyst was obtained in the same manner as in example 1.
Example 4:preparing a Fe-Mn bimetal mixed oxide catalyst:
firstly, preparing a dipping pretreatment process for a Fe and Mn bimetal mixed oxide catalyst;
20mL of absolute ethanol was added to a 50mL beaker to obtain solution A. Weighing Fe (NO)3)3·9H2O powder medicine 482.68mg and Mn (CH)3COO)2·H2Placing 222.81mg of O powder medicine into a 50mL beaker, adding 20mL of high-purity water into the beaker, stirring the powder medicine by a glass rod to be fully dissolved, and carrying out ultrasonic oscillation for 5min to obtain a solution B. The two solutions A, B were mixed in a 100mL beaker and magnetically stirred for 24 hours to fully dissolve and uniformly disperse Fe and Mn ions, resulting in a mixed solution C. The preparation proportion is 1.5mL of concentrated ammonia water: 8.5mL of highly pure aqueous ammonia solution D, after stirring, adding the aqueous ammonia solution D dropwise into the mixed solution C, and mixing with Fe3+And Mn2+And (3) reacting to obtain Fe oxide and hydroxide and Mn oxide and hydroxide, and continuously stirring for one hour after the ammonia water solution D is completely added to obtain a mixed solution E.
In the second step, a Fe, Mn mixed bimetal oxide catalyst was obtained in the same manner as in example 1.
Example 5:preparation of Fe metal oxide catalyst:
the first step, dipping pretreatment process;
20mL of absolute ethanol was added to a 50mL beaker to obtain solution A. Weighing Fe (NO)3)3·9H2O powder drug 482.68mg was placed in a 50mL beaker and charged into the beakerAdding 20mL of high-purity water, stirring the powder medicine by a glass rod, fully dissolving, and carrying out ultrasonic oscillation for 5min to obtain a solution B. The two solutions A, B were mixed in a 100mL beaker and subjected to magnetic stirring for 24 hours to sufficiently dissolve and uniformly disperse Fe ions, resulting in a mixed solution C. The preparation proportion is 1.5mL of concentrated ammonia water: 8.5mL of highly pure aqueous ammonia solution D, after stirring, adding the aqueous ammonia solution D dropwise into the mixed solution C, and mixing with Fe3+And (3) reacting to obtain an oxide and a hydroxide of Fe, and continuously stirring for one hour after the ammonia water solution D is completely added to obtain a mixed solution E.
In the second step, an Fe metal oxide catalyst was obtained in the same manner as in example 1.
Example 6:preparation of Mn metal oxide catalyst:
the first step, dipping pretreatment process;
20mL of absolute ethanol was added to a 50mL beaker to obtain solution A. Weighing Mn (CH)3COO)2·H2Placing 222.81mg of O powder medicine into a 50mL beaker, adding 20mL of high-purity water into the beaker, stirring the powder medicine by a glass rod to be fully dissolved, and carrying out ultrasonic oscillation for 5min to obtain a solution B. The two solutions A, B were mixed in a 100mL beaker and subjected to magnetic stirring for 24 hours to sufficiently dissolve and uniformly disperse Mn ions, resulting in a mixed solution C. The preparation proportion is 1.5mL of concentrated ammonia water: 8.5mL of highly pure aqueous ammonia solution D, after stirring, dropwise adding the aqueous ammonia solution D into the mixed solution C, and mixing with Mn2+And (3) reacting to obtain Mn oxide and Mn hydroxide, and continuously stirring for one hour after the ammonia water solution D is completely added to obtain a mixed solution E.
In the second step, a Mn metal oxide catalyst was obtained in the same manner as in example 1.
The catalysts prepared in examples 1-6 above were tested for performance and compared as follows.
As shown in fig. 1a, which is an SEM image of the bimetal mixed oxide catalyst of iron and manganese prepared in example 4, the catalyst particles are irregular and have non-uniform sizes, and the agglomeration phenomenon is relatively obvious. Comparing FIGS. 1b and 1c, it can be seen that the scanning electron microscope images of the Fe and Mn supported catalyst are compared with the scanning electron microscope images of the pure molecular sieveThe particles are all micro-nano granular small balls which are agglomerated into large particles, which shows that the ferro-manganese bimetallic load does not damage SiO in the molecular sieve2The skeleton structure of (1).
Fig. 2a and 2b show transmission electron microscope images (TEM images) of Fe — Mn/molecular sieve and pure molecular sieve, which maintain a uniform and ordered pipe structure near the surface while maintaining an ordered pipe structure near the surface after loading a certain amount of iron and manganese metals, and the width of the pipe structure before and after loading does not change significantly, which also indicates that the molecular sieve itself does not change its structure before and after loading bimetal.
FIG. 3a is a comparison of XRD test results for iron oxide prepared in example 5 with a standard card showing most of the diffraction peaks as Hematite α -Fe shown below2O3Standard crystal planes correspond to each other, indicating that the iron oxide catalyst component prepared in example 5 is Hematite α -Fe of ultrafine powder crystals2O3. FIG. 3b is a comparison of XRD test results of the manganese oxide catalyst prepared in example 6 with those of a standard card, wherein most of the diffraction peaks have the peak patterns shown below the Mn values actually3O4The standard crystal faces correspond to each other, and Hausmanite Mn of which the component of the prepared manganese oxide catalyst is ultrafine powder crystal is shown3O4. Both FIGS. 3c and 3d show that the monometallic iron supported catalyst or the monometallic manganese supported catalyst did not show diffraction peaks of the relevant metal oxides, and both showed SiO after supporting as in pure MCM-412(ii) an amorphous diffuse reflection peak; figure 3e shows that the XRD pattern after bimetallic loading is consistent with that of pure MCM-41 and shows no diffraction peaks for the relevant metals and their oxides.
The catalytic performance of the Fe and Mn bimetallic loaded MCM-41 molecular sieve prepared in example 1 for catalyzing ozone oxidation to degrade methyl orange is tested, and FIG. 4 shows that Fe-Mn/MCM-41, MCM-41 and α -Fe are respectively added under the same experimental conditions (the oxygen airflow flux is 20ml/min, the ozone test concentration is 34.8mg/L, the initial pH is 5.0, the degraded methyl orange concentration is 1.0mmol/L, and the catalyst addition is 1.0g/L)2O3With Mn3O4Compared with the pure ozone oxidation methyl orange, the bimetal mixed oxide, the Fe/MCM-41 and the Mn/MCM-41 catalyst participate in the ozone oxidation degradation of the methyl orange, compared with the single ozone oxidation degradation of the methyl orange solution to form a methyl orange solution concentration change curve 1, the addition of the Fe/MCM-41 catalyst to form a curve 5 after the methyl orange degradation in a certain range falls behind, and compared with the pure ozone oxidation, the other added catalysts can improve the efficiency of degrading the methyl orange. And the oxidation degradation performance of the Fe-Mn/MCM-41 type catalyst added represented by the curve 2 is improved fastest, the methyl orange solution with the same high concentration can be degraded in 30 minutes in advance, and the other types of catalysts are consistent with the pure ozone oxidation and can be completely degraded in 80 minutes.
FIG. 5 shows the experimental conditions for the Fe-Mn/MCM-41 catalyst prepared in example 1 of the invention with an oxygen flux of 20ml/min and ozone test concentrations of: 34.8mg/L, initial pH 5.0, and concentration of degraded methyl orange at 1.0mmol/L in the test curves of the degraded methyl orange in different addition concentrations of Fe-Mn/MCM-41 type catalyst, wherein the concentrations of the three groups of catalysts in FIG. 5 are respectively 1.0g/L, 2.0g/L and 0.5g/L, which respectively correspond to curve 1, curve 2 and curve 3 in the figure. It can be seen from curve 1 that the fading rate of catalytic degradation is fastest when the catalyst is added at 1.0g/L, methyl orange is completely degraded at 50 minutes, and the change of curve 2 when 2.0g/L catalyst is added indicates that the fading of methyl orange is not accelerated but reduced, which may be related to the interaction of active oxide groups generated in the reaction, and the fading rate of methyl orange when 0.5g/L catalyst is added at curve 3 is slowed, which is also related to the reduction of catalytic efficiency caused by insufficient catalyst. It can be concluded that the highest catalytic activity can be achieved by adding a suitable amount of catalyst.
In FIG. 6, curve 1, curve 2 and curve 3 represent a group of Fe-Mn/MCM-41 catalysts prepared in example 1 of the present invention at a concentration of 1.0g/L under reaction conditions of an oxygen flow rate of 20ml/min and ozone test concentrations: 34.8mg/L, the initial pH value is 5.0, the concentration of the degraded methyl orange is 1.0mmol/L, and the addition amount of the catalyst is 1.0g/L, and the degradation efficiency chart of a continuous three-group cycle experiment shows that the Fe-Mn/MCM-41 type catalyst has strong cycle reusability and can keep high catalytic activity after being used for many times.
FIG. 7 shows the reaction solution of Fe-Mn/MCM-41 catalyst prepared in example 1 of the present invention at different pH values, and other reaction conditions were that the oxygen flow rate was 20ml/min, and the ozone test concentration was: 34.8mg/L, the concentration of degraded methyl orange is 1.0mmol/L, and the degradation efficiency curve at the addition of the catalyst is 1.0g/L, it can be seen that under the slightly alkaline environment (pH 9) represented by curve 4, the concentration of methyl orange is reduced most rapidly in the first 30 minutes, and the high catalytic activity is shown, which is consistent with the higher activity of ozone under the alkaline condition. It is also known that under slightly acidic (pH 5) and neutral (pH 7) conditions, which are common in the industry, the methyl orange concentration change appears as curves 3 and 2 in the figure, also maintaining a higher degradation activity, consistent with slightly basic (pH 9) conditions, which completely discolors the methyl orange within 50 minutes. The acidic environment represented by curve 1 (pH 3) has some effect on the efficiency of ozone oxidation. Therefore, in industrial application, Fe-Mn/MCM-41 is used for catalyzing ozone decomposition of methyl orange under weak acid or weak base and neutral conditions.
FIG. 8 shows the experiment of pure ozone oxidation degradation of methyl orange in a mixed catalyst composed of Fe-Mn/MCM-41 catalyst prepared in example 1 of the present invention and single metal supported molecular sieve based on the iron and manganese precursor amounts. The change in Total Organic Carbon (TOC) of the reaction solution at each stage of the reaction with time is shown in FIG. 8, and the addition of the Fe-Mn/MCM-41 catalyst under the same conditions as compared with the pure ozone oxidation can be compared from curves 1 and 3: at 60 minutes, the Total Organic Carbon (TOC) is degraded by 13.3 percent, and the methyl orange solution is degraded for a long time of 150 minutes, the Total Organic Carbon (TOC) is degraded by 33.9 percent, so that the capability of deeply degrading organic matters in wastewater is higher. Meanwhile, compared with the Fe-Mn/MCM-41 catalyst, the mixed catalyst with the mass ratio of Fe/MCM-41 to Mn.MCM-41 being 2:1 is added for degradation experiment: the Total Organic Carbon (TOC) degradation amount is improved by 11.5% when the reaction time is 60 minutes, the Fe-Mn/MCM-41 catalyst is obviously improved compared with the mixed catalyst in the long-time degradation of 150 minutes, and the Total Organic Carbon (TOC) degradation amount is improved by 24%. 5%, which also indicates that the Fe-Mn/MCM-41 bimetal supported catalyst does not catalyze the ozone oxidation of two metals independently, but the Fe and Mn bimetal have a synergistic effect and catalyze the ozone oxidation simultaneously, so that higher catalytic efficiency is obtained.
Claims (4)
1. A preparation method of a supported catalyst for deeply degrading industrial dye wastewater is characterized by comprising the following steps: the specific steps are as follows,
firstly, carrying out impregnation pretreatment on carrier powder and loaded active components;
firstly, placing MCM-41 mesoporous molecular sieve powder in an ethanol solution for ultrasonic oscillation to obtain a solution A with uniformly distributed molecular sieve powder; dissolving Fe and/or Mn precursor powder in high-purity water for ultrasonic oscillation to obtain a solution B containing a Fe source and/or a Mn source;
then, mixing and stirring the solution A and the solution B, and fully stirring for 24 hours under magnetic stirring to obtain a mixed solution C; mixing concentrated ammonia water and high-purity water in proportion, and ultrasonically oscillating for 5min to obtain an ammonia water solution D;
dropwise adding the ammonia water solution D into the mixed solution C by using a separating funnel, keeping fully stirring, and continuously stirring for 1 hour after completely adding the ammonia water solution D to obtain a mixed solution E;
the ammonia water solution D is prepared from concentrated ammonia water: high purity water 1.5 mL: 8.5 mL;
the used strong ammonia water is a commercial ammonia water solution with the mass percentage concentration of 25 percent;
the solution A is prepared according to the proportion that 1.000g of molecular sieve powder is added into each 20mL of ethanol; the volume of the high-purity water in the solution B is the same as that of the ethanol in the solution A; adding Fe source and/or Mn source precursor powder into the solution B according to the following mass ratio:
M(Fe):m(MCM-41)＝10:100，m(Mn):m(MCM-41)＝5:100；
wherein, m (Fe) represents the mass of the Fe source precursor powder, m (Mn) represents the mass of the Mn source precursor powder, and m (MCM-41) represents the mass of the molecular sieve powder in the solution a;
selecting Fe (NO) from the Fe source precursor powder3)3·9H2O, the Mn source precursor powder is selectedSelecting Mn (CH)3COO)2·H2O；
Secondly, preparing a metal loaded MCM-41 mesoporous molecular sieve catalyst by a one-step solvothermal method;
transferring the mixed solution E into a hydrothermal reaction kettle, carrying out solvothermal reaction in an oven A for 8 hours, after the solution is cooled, transferring the solution in the hydrothermal reaction kettle into a centrifugal tube, carrying out centrifugal treatment, and pouring out supernatant in the centrifugal tube to obtain a precipitate F; centrifuging and washing the precipitate F with high-purity water and ethanol respectively until the pH value of the supernatant is higher than 5 to obtain a precipitate G; transferring the precipitate G into a watch glass, placing the watch glass in an oven B for drying to obtain the loaded MCM-41 mesoporous molecular sieve catalyst, and placing the loaded MCM-41 mesoporous molecular sieve catalyst in a dryer for storage under a drying condition for later use;
the temperature of an oven A used in the solvothermal method is 180 ℃; the temperature of oven B when drying precipitate G was 80 deg.C, and kept drying for 12 hours.
2. The preparation method of the supported catalyst for deeply degrading the industrial dye wastewater according to claim 1, characterized in that: the obtained loaded MCM-41 mesoporous molecular sieve catalyst is a MCM-41 mesoporous molecular sieve catalyst loaded by Fe and Mn double transition metals, or a MCM-41 mesoporous molecular sieve catalyst loaded by Fe, or a MCM-41 mesoporous molecular sieve catalyst loaded by Mn.
3. The preparation method of the supported catalyst for deeply degrading the industrial dye wastewater according to claim 1, characterized in that: the obtained MCM-41 mesoporous molecular sieve-loaded catalyst is SiO of a molecular sieve2The skeleton structure of (1).
4. The preparation method of the supported catalyst for deeply degrading the industrial dye wastewater according to claim 1, characterized in that: when the obtained MCM-41 mesoporous molecular sieve-loaded catalyst is used for a catalytic ozone oxidation methyl orange experiment, when high-concentration MO wastewater with initial TOC of 168mg/L is degraded, the TOC degradation percentage can reach 77.5% in 150min, and the TOC degradation percentage is improved by 33.9% compared with that of pure ozone oxidation; in three-cycle use, the fading of 1mM methyl orange solution within 50min is kept, and the reusability is good.
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