CN103952758A - Birnessite as microwave degradation catalyst as well as synthesis and application thereof - Google Patents
Birnessite as microwave degradation catalyst as well as synthesis and application thereof Download PDFInfo
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- CN103952758A CN103952758A CN201410195379.6A CN201410195379A CN103952758A CN 103952758 A CN103952758 A CN 103952758A CN 201410195379 A CN201410195379 A CN 201410195379A CN 103952758 A CN103952758 A CN 103952758A
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Abstract
The invention discloses birnessite as a microwave degradation catalyst as well as synthesis and an application thereof. The method can stably control the molar ratio of Mn(III) and Mn(IV) in a birnessite product so as to control the regular crystal structure in birnessite. The birnessite with continuously changing molar ratio of Mn(III) and Mn(IV) in a certain range is prepared by the method. The birnessite has a remarkable degrading effect to methylene blue under the microwave-induced condition.
Description
Technical field
The present invention relates to the synthetic and application of mineral, particularly as birnessite and the synthetic and application thereof of microwave degradation catalyzer.
Background technology
In recent years, microwave irradiation technology has become a kind of efficient processing organic pollutant " green " technology.Manganese mineral has good microwave absorbing property, and its structural framework great majority are by [MnO
6] octahedra with common drift angle or altogether the form of rib interconnect and form, be mainly frame shape and laminate structure type.Can be divided into and there is (1 × n) pyrolusite-ramsdellite family of pore passage structure, (2 × n) hollandite-romanechite family of pore passage structure, (3 × n) todorokite family and (1 × ∞) laminate structure manganese oxide mineral of pore passage structure.Manganese mineral is often applied to environmentally conscious materials, can serve as sorbent material, oxygenant and catalyzer.Can there is the polarization of moment and stronger active centre in manganese mineral, and then induced oxidation agent is in its surface generation oxidizing reaction, forms active oxidation material, thereby the oxidative degradation of organic pollutant is had to potential effect under the effect of microwave.
In prior art, there is the method for synthetic birnessite, as Chinese patent CN103553848A, a kind of preparation method of birnessite is disclosed, this preparation method is taking potassium permanganate and hydrochloric acid as raw material, through high temperature ageing filtering and washing again, solid matter freeze-drying is ground and sieved make birnessite.The birnessite that the method makes, wherein the Mn of manganese element (III) is difficult to control with the mol ratio of Mn (IV), poor reproducibility, the product catalytic efficiency difference that different batches makes is large, has randomness factor.
At present, not yet there is the preparation method's of the birnessite of the stable Mn of control (III) and Mn (IV) mol ratio report.
Summary of the invention
In order to address the above problem, the inventor has carried out research with keen determination, found that: birnessite is along with wherein contained Mn (III) is different from the mol ratio of Mn (IV), degradation effect difference to water methylene blue under microwave action, select the manganese element of different valence state as reaction raw materials, the mol ratio of Mn (III) and Mn (IV) in the birnessite that regulates and controls to make by control raw material ratio and reaction conditions, and carry out structure regulating to birnessite, thereby make the birnessite making there is stable degradation efficiency and degradation rate to methylene blue.
The object of the present invention is to provide following aspect:
First aspect, the invention provides a kind of preparation method of the birnessite as microwave degradation catalyzer, it is characterized in that, the method comprises the following steps:
(1) be in molar ratio MnCl
2: KMnO
4: NaOH=1:(0.41～0.63): 12.5 ratio, takes respectively MnCl
2or MnCl
24H
2o, KMnO
4and NaOH, be mixed with respectively the MnCl that volumetric molar concentration is 0.4mol/L
2the KMnO of solution, 0.19mol/L～0.22mol/L
4the NaOH solution of solution and 5mol/L;
(2) the NaOH solution of preparation in step 1 is added to MnCl under the condition of vigorous stirring
2solution, stirs 1～5min, then continues to drip KMnO
4solution, dropwises rear continuation and stirs 30～60min, obtains pre-sample preparation;
(3) by the pre-sample preparation making in step 2 ageing 24～72 hours under 15～45 DEG C of conditions, obtain ageing product;
(4) by the ageing product making in step 3 centrifugal 1～5min under the condition of 2000～7000r/min, be preferably 3000～5000r/min, as 3600r/min, by the solids wash obtaining after centrifugal 6～15 times, preferably washing 8～12 times, as wash 10 times, make wet product;
(5) by the wet product vacuum-drying at 50～80 DEG C obtaining in step 4.
Second aspect, the present invention also provides above-mentioned preparation method, it is characterized in that, and mol ratio described in step 1 is MnCl
2: KMnO
4: NaOH=1:(0.41～0.50): 12.5.
The third aspect, the present invention also provides above-mentioned preparation method, it is characterized in that, and products obtained therefrom is single-phase birnessite, and its molecular formula is Na
0.55mn
2o
41.5H
2o, wherein Mn (III) is 0.5:1～1.2:1 with the mol ratio of Mn (IV); The peak value interlamellar spacing of its (001) crystal face is:
in XRD spectrum, be 7.13 °, 3.56 ° and 2.44 ° at diffraction angle 2 θ and locate to exist diffraction peak; Wherein the electron spinning magnetic moment of Mn (III) is 4 μ B, and the electron spinning magnetic moment of Mn (IV) is 3 μ B.
Fourth aspect, the present invention also provides a kind of birnessite as microwave degradation catalyzer, it is characterized in that, and the molecular formula of this birnessite is: Na
0.55mn
2o
41.5H
2o, wherein, Mn (III) is 0.6:1～1.5:1 with the mol ratio of Mn (IV).
The 5th aspect, the present invention also provides above-mentioned birnessite, it is characterized in that, and the peak value interlamellar spacing of (001) crystal face of this birnessite is:
The 6th aspect, the present invention also provides above-mentioned birnessite, it is characterized in that, is 7.13 °, 3.56 ° and 2.44 ° locates to exist diffraction peak in the XRD spectrum of this birnessite in diffraction angle.
The 7th aspect, the present invention also provides above-mentioned birnessite, it is characterized in that, and the electron spinning magnetic moment of Mn in this birnessite (III) is 4 μ B, and the electron spinning magnetic moment of Mn (IV) is 3 μ B.
Eight aspect, the present invention also provides above-mentioned birnessite, it is characterized in that, and this birnessite is single-phase birnessite.
The 9th aspect, the present invention also provides the application of a kind of birnessite as microwave degradation catalyzer as microwave induced degradation of methylene blue catalyzer.
The tenth aspect, the present invention also provides above-mentioned application, it is characterized in that, and the power of described microwave is 300～800W, and the microwave induced time is 30～50min, and the addition of birnessite in methylene blue is 400g birnessite/100g methylene blue.
Brief description of the drawings
Fig. 1 illustrates the XRD spectra of embodiment 1～6 and comparative example 1 prepared sample;
Fig. 2 illustrates the reaction Kinetics Model figure of microwave catalysis system;
Fig. 3 a illustrates the XPS figure of the birnessite making in embodiment 1;
Fig. 3 b illustrates the XPS figure of the birnessite making in embodiment 1 after microwave treatment;
Fig. 3 c illustrates the XPS figure of birnessite after degradation of methylene blue;
Fig. 3 d illustrates the XPS figure of the birnessite of the methylene blue of degrading after microwave treatment;
The Degradation of the birnessite that Fig. 4 illustrates different Mn (III) and Mn (IV) mol ratio to methylene blue;
The ultraviolet full wavelength scanner figure of system when Fig. 5 illustrates the different microwave induced time;
Fig. 6 illustrates the liquid-matter coupling mensuration figure of birnessite to methylene blue degraded product.
Embodiment
Below by the present invention is described in detail, the features and advantages of the invention will become more clear, clear and definite along with these explanations.
Birnessite is a kind of manganese oxide mineral that occurring in nature extensively exists, and is the mixed valence Mn oxide being made up of manganic and tetravalence manganese, and structure composition is complicated, and it is often used as environmentally conscious materials, can serve as sorbent material, oxygenant and catalyzer.Birnessite is under the effect of microwave, can there is the polarization of moment and produce stronger active centre, and then the manganese that induction has oxidisability is in its surface generation oxidizing reaction, form active oxidation material, organic pollutant is carried out to oxidative degradation, this character and its structure of birnessite are closely related, in its structure, and [MnO
6] octahedra in ab plane by the common edge formation lamella that interconnects.By this [MnO
6] octahedra lamella along c-axis direction pile up form layered crystal structure, at two [MnO
6] filling Na between octahedral layer
+and water molecule layer, but often there are many textural defect in the birnessite existing at occurring in nature, as at two-layer [MnO
6] between filling two-layer water molecules, make [MnO
6] interlamellar spacing increase, thereby make the performance of birnessite be difficult to ensure.
The inventor finds through research, in microwave induction catalytic degradation of methylene blue system, Mn (III) plays an important role to degradation efficiency and degradation rate with the mol ratio of Mn (IV), Mn (III) mol ratio increases, it strengthens in the microwave induced lower Degradation to methylene blue, therefore, the inventor is taking Manganous chloride tetrahydrate or six water Manganous chloride tetrahydrates and potassium permanganate as raw material, according to transfer transport law of conservation by controlling the feed ratio of Mn (II) and Mn (VII) in raw material, and be controlled at and under alkaline condition, make single-phase birnessite, there is stable Mn (III) and Mn (IV) mol ratio and regular crystalline structure, avoid the textural defect of birnessite, make it there is higher degradation efficiency and degradation rate to methylene blue down microwave induced.
To the third aspect, the invention provides a kind of preparation method of the birnessite as microwave degradation catalyzer according to provided by the invention first, the method comprises the following steps:
Step 1 is MnCl in molar ratio
2: KMnO
4: NaOH=1:(0.41～0.63): 12.5 take respectively MnCl
2or MnCl
24H
2o, KMnO
4and NaOH, preferably MnCl
2: KMnO
4: NaOH=1:0.50:12.5,1:0.48:12.5,1:0.46:12.5,1:0.45:12.5,1:0.43:12.5,1:0.42:12.5,1:0.41:12.5, is mixed with respectively the MnCl that volumetric molar concentration is 0.4mol/L
2the KMnO of solution, 0.19mol/L～0.22mol/L
4the NaOH solution of solution and 5mol/L.
For making the birnessite of there is Mn (III) and Mn (IV), the present invention selects the compound of contain+divalent manganese element and+7 valency manganese elements as reaction raw materials, that redox reaction can occur the compound that contains these two kinds of valence state manganese elements mutually on the one hand, easily generate the compound of valence state manganese element in the middle of containing, and can well avoid the generation of side reaction, avoid the generation of other valence state manganese element; On the other hand, the compound that contains these two kinds of valence state manganese elements is more common, easily obtain, thereby can reduce preparation cost, in the compound of contain+divalent manganese element and+7 valency manganese elements, under normal condition, stable and inexpensive compound is Manganous chloride tetrahydrate or four hydration Manganous chloride tetrahydrates, potassium permanganate, therefore, the present invention selects above-claimed cpd as the raw material of preparing birnessite.
For Mn (III) in the birnessite product that makes to make is 0.6:1～1.5:1 with the mol ratio of Mn (IV), control MnCl in raw material
2or MnCl
24H
2o and KMnO
4mol ratio be 1:(0.63～0.41), preferably MnCl
2or MnCl
24H
2o and KMnO
4mol ratio be 1:(0.5～0.41), for example 1:0.45, making Mn (III) in prepared birnessite product is (0.6～1.5) with the mol ratio of Mn (IV): 1, be preferably (0.6～1.2): and 1, as 0.9:1.
Selective reaction condition of the present invention is alkaline condition, because the oxidation capacity of potassium permanganate under alkaline condition increases, can react with Manganous chloride tetrahydrate fast, generate Mn (III) and Mn (IV), meanwhile, the alkali that the present invention selects is sodium hydroxide, and it can be that birnessite provides sodium element and without using other compounds containing sodium as sodium source, thereby reduce raw material, reduced preparation cost.Therefore, the present invention selects MnCl
2or MnCl
24H
2o, KMnO
4with the mol ratio of NaOH be 1:(0.41～0.63): 12.5, preferably MnCl
2or MnCl
24H
2o, KMnO
4, with the mol ratio of NaOH be 1:(0.41～0.50): 12.5, for example 1:0.45:12.5.
In the time that reaction solution concentration is excessive, the crystallization velocity of product is too fast, causes crystal morphology inhomogeneous; In the time that reaction solution concentration is too small, the crystallization velocity of product is too small, even separates out without crystal because the concentration of product in reaction system is too low, and therefore, the present invention selects MnCl
2the concentration of solution is 0.4mol/L, KMnO
4the concentration of solution is that 0.19mol/L～0.22mol/L and NaOH strength of solution are 5mol/L.
Step 2 adds MnCl by the NaOH solution of preparation in step 1 under the condition of vigorous stirring
2solution, stirs 1～5min under room temperature, then continues to drip KMnO
4solution, dropwises rear continuation and stirs 30～60min, makes pre-sample preparation.
Sodium hydroxide is added to manganese chloride solution, make Manganous chloride tetrahydrate generate manganous hydroxide, simultaneously vigorous stirring, the manganous hydroxide generating is uniformly dispersed in reaction system, drip wherein again potassium permanganate, avoid potassium permanganate oxidation to cross strong and cause other side reaction, generate the by product of value Mn.
After potassium permanganate dropwises, continue to stir 30～60min, Manganous chloride tetrahydrate is fully reacted with potassium permanganate, generate birnessite.
Step 3, at 15～45 DEG C, as ageing at ambient temperature 24～72 hours, preferably 36～48 hours, makes ageing product by the pre-sample preparation making in step 2.
Pre-sample preparation, at 15～45 DEG C, as ageing at ambient temperature, is made to its even crystallization, and digestion time is selected 24～72 hours, and preferably 36～48 hours, can make the birnessite crystal making concentrate, be convenient to subsequent purification processing.
Step 4, by the ageing product making in step 3 centrifugal 1～5min under the condition of 2000～7000r/min, is preferably 3000～5000r/min, as 3600r/min, by the solids wash obtaining after centrifugal 6～15 times, preferably wash 8～12 times, as wash 10 times, make wet product.
By ageing product centrifuge washing, residual raw material and other water-soluble impurity in can eccysis product birnessite, along with the increase of washing times, products therefrom birnessite is purer, but its yield also can decline thereupon, therefore, the present invention selects to wash 6～15 times, preferably 8～12 times, as wash 10 times.
The present invention is not particularly limited centrifugal speed and centrifugation time, ageing product fully separated with washings, and be 2000～7000r/min as selected centrifugal speed, be preferably 3000～5000r/min, as 3600r/min, centrifugation time is 1～5min, as 3min.
Step 5, by the wet product vacuum-drying at 50～80 DEG C obtaining in step 4.
By the vacuum-drying at 50～80 DEG C of the product of above-mentioned centrifugal rear gained, can reduce on the one hand the boiling point of solvent, product can be completed at short notice dry, on the other hand, the needed drying temperature of vacuum-drying is lower, and therefore, the crystalline structure of product birnessite can not destroy.
The birnessite being made by above-mentioned preparation method, by XRD analysis, measuring its molecular formula is Na
0.55mn
2o
41.5H
2o, wherein Mn (III) is 0.6:1～1.5:1 with the mol ratio of Mn (IV); Its XRD diffraction spectra is known, and it is 7.13 °, 3.56 ° and 2.44 ° at diffraction angle 2 θ and locates to exist diffraction peak, and the peak value interlamellar spacing of its (001) crystal face is:
wherein the electron spinning magnetic moment of Mn (III) is 4 μ B, and the electron spinning magnetic moment of Mn (IV) is 3 μ B.
Birnessite provided by the invention is the birnessite of synthetic, by controlling synthesis condition, and manually controlled its microtexture, and the mol ratio of Mn (III) in birnessite and Mn (IV).
The inventor finds after deliberation, in the time that Mn in birnessite (III) increases with the mol ratio of Mn (IV), its Degradation to methylene blue strengthens, and in the time that Mn (III) is greater than 1.5 with the mol ratio of Mn (IV), in the birnessite making, there will be stray crystal, be that crystal is impure, therefore, in the water sodium manganese making in the present invention, Mn (III) is 0.6:1～1.5:1 with the mol ratio of Mn (IV), be preferably 0.6:1～1.2:1, as 0.9:1.
According to the of the present invention the 4th to eight aspect, the present invention also provides a kind of birnessite as microwave degradation catalyzer, this birnessite is single-phase birnessite, it is 7.13 °, 3.56 ° and 2.44 ° at diffraction angle 2 θ and locates to exist diffraction peak in XRD spectrum, and the peak value interlamellar spacing on (001) crystal face is:
wherein the electron spinning magnetic moment of Mn (III) is 4 μ B, and the electron spinning magnetic moment of Mn (IV) is 3 μ B.
According to the 9th, the tenth aspect provided by the invention, the present invention also provides the application of a kind of birnessite as microwave degradation catalyzer as microwave induced degradation of methylene blue catalyzer.
The power of described microwave is 300～800W,
The microwave induced time of microwave time is 30～50min
The addition of birnessite in methylene blue is 400g birnessite/100g methylene blue.
In birnessite crystalline structure, crystal face interlamellar spacing is less, illustrate that wherein Mn (III) is larger with the mol ratio of Mn (IV), and by Fig. 1 obviously visible (specifically referring to experimental example 1), the birnessite that the present invention makes has less crystal face interlamellar spacing, wherein Mn (III) is large with Mn (IV) mol ratio, and the microwave catalysis performance of the birnessite that known the present invention makes is good.
Be not bound by any theory, the inventor thinks that birnessite thing is inseparable with its structure to the microwave degradation performance of methylene blue.Under the high frequency of alternating electromagnetic field changes, the microcosmic particles such as atom in birnessite thing, molecule, ion can absorb rapidly micro-wave energy, make the surface temperature of birnessite sharply increase thereby make part micro-wave energy be converted into heat energy, there is good responding microwave performance.
The responding microwave ability of birnessite may come from that Mn in octahedron does not overlap with O positive and negative charge center and the natural dipole moment that produces or the electron spinning magnetic moment of center Mn ion.But, in the bright birnessite of reckoner, because Mn (III) increases greatly, make [MnO
6] octahedra generation Jahn-Teller distortion, causing the distortion of lattice, the calculation formula of polyhedron degreeof tortuosity is as follows, wherein △ × 10
3and σ
2represent respectively the degreeof tortuosity of polyhedron bond distance and bond angle:
Wherein,
D
i-polyhedron bond distance;
D
m-show average bond length;
θ
i-polyhedron bond angle;
(in the time that polyhedron is tetrahedron, this angle is 109.47 ° and substitutes 90-octahedra average bond angle; In the time that polyhedron is trilateral, this angle is 120 ° and substitutes).
But because the lattice distortion of birnessite has centre symmetry, therefore, its natural dipole moment is also 0, thus the turning losses of the electron spinning magnetic moment that the suction microwave that judges birnessite mainly comes from mn ion in microwave electromagnetic field.
Ultimate analysis shows, the birnessite at a middle or low price mol ratio of manganese is large, therefore infers that the more excellent reason of birnessite responding microwave ability is in its structure, to contain the compare great center manganese moment of dipole that spins, and makes action effect better.
In addition, Mn (III) skin has more unpaired electron, thereby increasing its electron spinning magnetic moment increases, and then cause it to there is good microwave absorption capacity, can increase its activity on the one hand, can improve greatly on the other hand birnessite particle surface temperature, its surface temperature can be up to 1000 DEG C of left and right, far above system macroscopic view temperature, this high surface temperature can promote the decomposition of methylene blue.
The inventor finds after deliberation, with the invention provides birnessite by microwave degradation method provided by the invention, can be micromolecular compound C by methylene blue catalyzed degradation
14h
13n
2oS, C
13h
11n
2oS, C
12h
8nO
2s and C
12h
9n
2oS (specifically referring to experimental example 7 and experimental example 8), these compounds are easy to natural degradation in environment, and environmental pollution is little, that is, and without secondary environmental pollution.
According to the birnessite as microwave degradation catalyzer provided by the invention and synthetic and application thereof, have the following advantages:
(1) birnessite provided by the invention is single-phase birnessite, has stable Mn (III) and Mn (IV) ratio, and it is microwave induced lower stable to the Degradation of methylene blue;
(2) birnessite provided by the invention has higher Mn (III) and Mn (IV) ratio, there is higher wave-sucking performance, the mechanical energy of microwave can be converted into Mn (III) and be converted into the chemical energy of Mn (IV), in the process of chemical conversion, being attended by birnessite particle surface temperature raises, can rise to 1000 DEG C of left and right, thereby improve the Degradation of birnessite to methylene blue;
(3) birnessite provided by the invention is remarkable to the Degradation of methylene blue, and degradation efficiency can be stabilized in 10% left and right, and degradation rate is more than 99%;
(4) method is simple for the above-mentioned birnessite of preparation provided by the invention, and mild condition is easy to control;
(5), under microwave induced, by the oxygenizement degradation of organic substances of surperficial value Mn ion, meanwhile, value Mn ion is reduced; Under microwave action, at a low price manganese is oxidized again, and making redox processes is that the process of catalyzed degradation methylene blue is continued.Embodiment
embodiment 1
(1) take respectively 3.9582g (20mmol) MnCl
24H
2o, 10.0000g (250mmol) NaOH, 1.2958gKMnO
4(8.2mmol), be dissolved in respectively in 50ml deionized water;
(2) pour NaOH solution into MnCl
2in solution, be placed on vigorous stirring 1min on magnetic stirring apparatus, more slowly drip KMnO under the condition stirring
4solution, after dropwising, continues violent stirring 30min;
(3) by room temperature ageing 48h of products therefrom;
(4) by ageing product centrifugal 1min under 3600r/min condition, use deionized water wash 2min, repeat above operation 10 times, then in 60 DEG C of vacuum drying ovens, dry and obtain birnessite, this birnessite is designated as to Bir-OH1.
As calculated, in sample Bir-OH1, Mn (III)/Mn (IV) is 1.2:1.
embodiment 2
The present embodiment is identical with embodiment 1 method therefor, and difference is only to take in step 1 KMnO
4quality be 1.3275g (8.4mmol), prepared sample is designated as Bir-OH2.
As calculated, in sample Bir-OH2, Mn (III)/Mn (IV) is 1.0:1.
embodiment 3
The present embodiment is identical with embodiment 1 method therefor, and difference is only to take in step 1 KMnO
4quality be 1.3591g (8.6mmol), prepared sample is designated as Bir-OH3.
As calculated, in sample Bir-OH3, Mn (III)/Mn (IV) is 0.9:1.
embodiment 4
The present embodiment is identical with embodiment 1 method therefor, and difference is only to take in step 1 KMnO
4quality be 1.4223g (9.0mmol), prepared sample is designated as Bir-OH4.
As calculated, in sample Bir-OH4, Mn (III)/Mn (IV) is 0.8:1.
embodiment 5
The present embodiment is identical with embodiment 1 method therefor, and difference is only to take in step 1 KMnO
4quality be 1.4539g (9.2mmol), prepared sample is designated as Bir-OH5.
As calculated, in sample Bir-OH5, Mn (III)/Mn (IV) is 0.7:1.
embodiment 6
The present embodiment is identical with embodiment 1 method therefor, and difference is only to take in step 1 KMnO
4quality be 1.5171g (9.6mmol), prepared sample is designated as Bir-OH7.
As calculated, in sample Bir-OH6, Mn (III)/Mn (IV) is 0.6:1.
Comparative example
comparative example 1
(1) take respectively 3.9582g (20mmol) MnCl
24H
2o, 10.0000g (250mmol) NaOH, 1.5803KMnO
4(10.0mmol), be dissolved in respectively in 50ml deionized water;
(2) pour NaOH solution into MnCl
2in solution, be placed on stirring at room temperature 5min on magnetic stirring apparatus, more slowly drip KMnO under the condition stirring
4solution, after dropwising, continues violent stirring 10min;
(3) by products therefrom ageing 24h at 50 DEG C;
(4) by ageing product centrifugal 1min under 8000r/min condition, use deionized water wash 3min, repeat above operation 10 times, then at room temperature dry and obtain birnessite, this birnessite is designated as to Bir-OH-d1.
As calculated, in sample Bir-OH-d1, Mn (III)/Mn (IV) is 0.5:1.
Experimental example
the XRD test of experimental example 1 sample
Sample prepared by embodiment 1～6 and comparative example 1 carries out XRD detection, and test condition is CuK α-irradiation, 40 kilovolts of tube voltages, tube current 100mA, 0.02 ° of 8 °/minute of sweep velocitys and step-length.Result as shown in Figure 1.
As shown in Figure 1, the prepared birnessite of embodiment 1～6 is single-phase birnessite, the birnessite that kind method makes thus has the space lattice of C2/m, the water sodium manganese that itself and comparative example 1 make there are differences in (001) crystal face interlamellar spacing, and in embodiment 1～6, the sample of preparation in (001) crystal face interlamellar spacing is
, and in comparative example 1, the sample of preparation in (001) crystal face interlamellar spacing is
, and crystal face interlamellar spacing is less, illustrates that the shared mol ratio of Mn in birnessite (III) is larger, therefore, the shared mol ratio of Mn in the birnessite of preparing in known embodiment (III) is large.
the ultimate analysis of experimental example 2 samples
The sample of preparation in comparative example 1 is carried out to ultimate analysis test, and result is as shown in table 1.
As shown in Table 1, the purity of birnessite is 95.52% left and right, and wherein the content of Mn is 54.1% left and right, and the content of O is 36.4% left and right, and the content of Na is 5.02% left and right.
Can infer thus in birnessite structure and contain more interlayer Na ion, illustrate that Mn in birnessite structure (III) and Mn (IV) coexist.
The ultimate analysis of table 1 birnessite
3 microwave action times of experimental example and the impact of different catalysts on catalytic effect
The sample that this experimental example is prepared using embodiment 1 is as test specimens.The addition of catalyzer is 400g catalyzer/100g methylene blue.
Microwave induced when not adopting, and while using catalyzer merely, methylene blue also has a certain amount of minimizing, supposition is that the low price manganese existing in the birnessite due to stratiform makes its surface have electronegativity, and methylene blue aobvious positive polarity in the aqueous solution, thereby be easy to be adsorbed by birnessite, i.e. the minimizing of methylene blue is that birnessite adsorption causes.
Different microwave action time of table 2 and the clearance/removal of catalyst loading to methylene blue
Efficiency
the reaction kinetics research of experimental example 4 microwave catalysis systems
This experimental example specimen in use is prepared by embodiment 1.
Experiment condition:
Microwave power: 400W; The addition of catalyzer is 400g catalyzer/100g methylene blue.
The kinetic equation of reaction is expressed as dC/dt=-kC
0 p(1)
Wherein,
C----methylene blue concentration;
P----reaction order;
K----reaction rate constant;
The t----reaction times.
For first order reaction, (1) formula can be changed into ln (C/C
0the kt of)=-(2).
To ln (C/C
0)-t mapping, by ln (C/C
0) the one-level regression equation of analyzing known microwave/birnessite+methylene blue system with the dependency of time t is: y=-0.0403x-1.3643, R
2=0.9938 (Fig. 2), relation conefficient is greater than critical relation conefficient (R>0.95), so under certain reaction conditions, this reaction system meets first order reaction kinetics pattern.
This shows that the microwave induced birnessite that makes continues to carry out to the degraded of methylene blue.
According to First-order kinetics equation, actual removal amount is carried out to matching, as shown in Figure 2, the first order kinetics reactional equation matching actual numerical value well of removal amount after microwave action 10min, microwave action 10min is poor with interior effect, this may be to be the starting stage of effect due to microwave during this period of time, raise gradually and do not reach stable in the temperature on this one-phase birnessite surface, therefore removal efficiency outline is lower than the Fitting Calculation of general trend.
experimental example 5X ray electronic spectrum (XPS) detects
This experimental example specimen in use is prepared by embodiment 1.
Sample is carried out to XPS detection, and detected result is as shown in Fig. 3 a～3d, and from Fig. 3 a～3d, the electron binding energy of birnessite is 642.25eV (Fig. 3 a), the Mn2p of birnessite after microwave treatment
3/2electron binding energy raises, and for 642.45eV, (Fig. 3 b); Mn2p after reacting with methylene blue again
3/2electron binding energy is reduced to 642.12eV, and (Fig. 3 c); Mn2p after microwave treatment again
3/2electron binding energy raises again, and into 642.27eV, (Fig. 3 d).
The electron binding energy of mn ion is respectively Mn (II): 641eV, Mn (III): 642.1eV, Mn (IV) 643eV, Mn (VI): 644.2eV and Mn (VII): 645.6eV, the therefore Mn2p to birnessite
3/2carrying out multispectral matching, there is the manganese of Mn (II), Mn (III), three kinds of valence states of Mn (IV) in birnessite surface; From Fig. 3 a～Fig. 3 d obviously, electron binding energy spectrum is triplet, this triplet is split visible, in the birnessite making in embodiment 1 taking Mn (III) as main, after microwave treatment, increase with Mn (IV) content, when after birnessite and methylene blue processing, Mn (II) content increases, again after microwave treatment, Mn (III) and Mn (IV) content all increase to some extent, there is the trend being transformed to value Mn by low price manganese in birnessite surface after microwave treatment, and change larger; After reacting with methylene blue, its surperficial value Mn is reduced again; After microwave treatment, the valence state of its surface manganese raises again again.
Birnessite oxidation methylene blue, its surperficial value Mn is reduced into manganese at a low price; Microwave induced its surface low price manganese that makes is oxidized to again value Mn, and so iterative cycles carries out, and birnessite serves as microwave degradation catalyzer, and induced reaction efficiency is improved gradually, and reaction continues to carry out.
Electron binding energy raises to the average oxidisability of high-end mobile explanation Mn, in conjunction with the average oxidisability reduction that can move to low side explanation Mn.Hence one can see that, and birnessite has stronger responding microwave performance, and microwave induced effect can make the average oxidisability of birnessite raise; Methylene blue reacts with birnessite and can make the average oxidisability of manganese element in birnessite reduce.
the birnessite of the different Mn of experimental example 6 (III) and Mn (IV) mol ratio is to methylene blue
degraded
This experimental example specimen in use is preparation in embodiment 1～6.
Be 700W according to microwave power respectively by the sample of preparation in embodiment 1～6; The addition of catalyzer be the condition of 400g catalyzer/100g methylene blue to the methylene blue solution 30min that degrades, then the solution after degraded is carried out to visible ray full wavelength scanner, result as shown in Figure 4.
As shown in Figure 4, in 500～550nm section, along with the reduction of birnessite oxidisability, the absorbancy of certain wavelength is along with Mn (III) mol ratio increases and reduces, the degradation effect that is methylene blue strengthens gradually, therefore be not subject to any constraint, the inventor thinks because the difference of the electron spinning dipole moment size of the birnessite Mn of central authorities ion causes its responding microwave ability different.
experimental example 7 ultraviolet-visible spectrophotometries are to degraded product analysis
This experimental example specimen in use is that embodiment 1 is prepared.
Experiment condition:
Microwave power is 700W; The addition of catalyzer is 400g catalyzer/100g methylene blue.
The visible full spectrogram of 500～700nm to above-mentioned system in the time that the microwave action time is 0s (curve 1), 30s (curve 2), 1min (curve 3), 2min (curve 4), 5min (curve 5), 10min (curve 6), 30min (curve 7) and 50min (curve 8) as shown in Figure 5.
As shown in Figure 5, the maximum absorption wavelength of methylene blue is in 665nm left and right, along with the increase of microwave induced time, the maximum absorption intensity of catalysate reduces gradually, maximum absorption wavelength is blue shift gradually, in the time that the microwave induced time is 5min, the maximum absorption wavelength of product is 618nm, shows that methylene blue macromole is degraded into small molecules; In the time that the microwave induced time is increased to 30min, product maximum absorption wavelength blue shift, to 600nm, shows to have new small molecules product to generate.
The visible absorbance peak of microwave induced 180min after product no longer moves, and infers the final product that product is now catalyst system.
the coupling of experimental example 8 liquid-matter is measured degraded product
This experimental example is measured its molecular weight to the product of different microwave induced times in experimental example 6 by liquid-matter method for combined use, and result is as shown in Fig. 6 a and Fig. 6 b.
As shown in Figure 6 a, the molecular weight of methylene blue is 284.3 (compounds 1), the molecular weight of birnessite former state is 257.07 as shown in Figure 6 b, when microwave induced 2min, the molecular weight of product is 243.05, when microwave induced 10min the molecular weight of product be 230.02 and when microwave induced 180min the molecular weight of product be 229.04, infer that through high resolution search its molecular formula is respectively C
14h
13n
2oS (compound 5), C
13h
11n
2oS (compound 4), C
12h
8nO
2s (compound 3) and C
12h
9n
2oS (compound 2).
In conjunction with embodiment and exemplary example, the present invention is had been described in detail above, but these explanations can not be interpreted as limitation of the present invention.It will be appreciated by those skilled in the art that in the situation that not departing from spirit and scope of the invention, can carry out multiple replacement of equal value, modify or improve technical solution of the present invention and embodiment thereof, these all fall within the scope of the present invention.Protection scope of the present invention is as the criterion with claims.
Claims (10)
1. as a preparation method for the birnessite of microwave degradation catalyzer, it is characterized in that, the method comprises the following steps:
(1) be in molar ratio MnCl
2: KMnO
4: NaOH=1:(0.41～0.63): 12.5 ratio, takes respectively MnCl
2or MnCl
24H
2o, KMnO
4and NaOH, be mixed with respectively the MnCl that volumetric molar concentration is 0.4mol/L
2the KMnO of solution, 0.19mol/L～0.22mol/L
4the NaOH solution of solution and 5mol/L;
(2) the NaOH solution of preparation in step 1 is added to MnCl under the condition of vigorous stirring
2solution, stirs 1～5min, then continues to drip KMnO
4solution, dropwises rear continuation and stirs 30～60min, obtains pre-sample preparation;
(3) by the pre-sample preparation making in step 2 ageing 24～72 hours under 15～45 DEG C of conditions, obtain ageing product;
(4) by the ageing product making in step 3 centrifugal 1～5min under the condition of 2000～7000r/min, be preferably 3000～5000r/min, as 3600r/min, by the solids wash obtaining after centrifugal 6～15 times, preferably washing 8～12 times, as wash 10 times, make wet product;
(5) by the wet product vacuum-drying at 50～80 DEG C obtaining in step 4.
2. method according to claim 1, is characterized in that, mol ratio described in step 1 is MnCl
2: KMnO
4: NaOH=1:(0.41～0.50): 12.5.
3. method according to claim 1, is characterized in that, products obtained therefrom is single-phase birnessite, and its molecular formula is Na
0.
55mn
2o
41.5H
2o, wherein Mn (III) is 0.6:1～1.5:1 with the mol ratio of Mn (IV); In XRD spectrum, be 7.13 °, 3.56 ° and 2.44 ° at diffraction angle 2 θ and locate to exist diffraction peak; The peak value interlamellar spacing of its (001) crystal face is:
wherein the electron spinning magnetic moment of Mn (III) is 4 μ B, and the electron spinning magnetic moment of Mn (IV) is 3 μ B.
4. as a birnessite for microwave degradation catalyzer, it is characterized in that, the molecular formula of this birnessite is: Na
0.55mn
2o
41.5H
2o, wherein, Mn (III) is 0.6:1～1.5:1 with the mol ratio of Mn (IV).
5. birnessite according to claim 4, is characterized in that, the peak value interlamellar spacing of (001) crystal face of this birnessite is:
6. birnessite according to claim 4, is characterized in that, is 7.13 °, 3.56 ° and 2.44 ° locates to exist diffraction peak in the XRD spectrum of this birnessite in diffraction angle.
7. birnessite according to claim 4, is characterized in that, the electron spinning magnetic moment of Mn in this birnessite (III) is 4 μ B, and the electron spinning magnetic moment of Mn (IV) is 3 μ B.
8. birnessite according to claim 4, is characterized in that, this birnessite is single-phase birnessite.
9. the birnessite as microwave degradation catalyzer is as the application of microwave induced degradation of methylene blue.
10. application according to claim 9, is characterized in that, the power of described microwave is 300～800W, and the microwave induced time is 30～50min, and the addition of birnessite in methylene blue is 400g birnessite/100g methylene blue.
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