CN104815609B - A kind of ferro manganese composite oxides and preparation method thereof and application - Google Patents
A kind of ferro manganese composite oxides and preparation method thereof and application Download PDFInfo
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Abstract
The invention discloses a kind of preparation method of ferro manganese composite oxides, step is as follows: (1) is added drop-wise to ferrous sulfate heptahydrate solution in liquor potassic permanganate, at 15-25 DEG C, react 1-1.5 hour, reaction obtains maroon suspension, and the pH of course of reaction regulator solution is 3.0-4.0; (2) maroon suspension step (1) being obtained is transferred in reactor, at 160-200 DEG C, reacts 5-7 hour, cooling, centrifugal, obtains maroon precipitation, and washing precipitation remains unchanged to the electrical conductivity of cleaning solution; (3) the maroon precipitation aged at room temperature 3.5-4.5 hour step (2) being obtained, dry, porphyrize, obtains the powder of ferro manganese composite oxides. The ferro manganese composite oxides rough surface preparing, specific area is large, forms pore structure comparatively uniformly between composite oxides surface detail granule, easily chromium ion in water is adsorbed wherein, be suitable for the processing of the chromate waste water of variable concentrations, clearance is high, and cost is lower.
Description
Technical field
The present invention relates to a kind of ferro manganese composite oxides and preparation method thereof and application, belong to water-treatment technology field.
Background technology
Chromium is very important metallic element in environment, and it is extensively distributed in the earth's crust. Along with the develop rapidly of workers and peasants' economy, byThe problem of environmental pollution that crome metal element causes is increasingly severe in the process of industrialization city, plating, process hides, mining, metal smeltingIn the manufacturing process of the industry such as refining and Treatment of Metal Surface, a large amount of chromium-containing ore, materials etc. of using, cause a large amount ofContaining chromium pollutant by all means (as industrial chromium-containing waste water discharge, chromium slag muck are put etc.) enter water body environment, and then cause waterBody environment heavy metal chromium in various degree pollutes, and therefore the great attention that is subject to Chinese scholars is administered in water body environment pollution of chromium. AdjustLook into and studies show that, the biological effectiveness of Cr (VI) will be higher than Cr (III), and toxicity is also larger, is approximately chromic 100 times. With much moneyBelonging to chromium can cause great harm to health, aquatile, ecological environment, and it not only has spread effect, can cause skinSkin pathology (as allergic phenomena), also has carcinogenesis. In addition, Long Term Contact, containing chromium environment, can cause the new of human body, biologyOld metabolic disorder.
Naturally occurring iron and manganese oxides is extensively thought that heavy metal ion is had to strong absorption and accumulation ability, main manifestationsIn the surface characteristic of oxide, there is fairly perfect duct in Mn oxide surface for example. In addition, iron, manganese are valence variation elements,Its (hydrogen) oxide has redox conventionally. Therefore, researcher extensively focuses on ferrimanganic oxygen both at home and abroad in the last few yearsThe adsorption/desorption behavior of compound to heavy metal ion and the discussion research of mechanism. For different heavy metal ion, ferrimanganic composite oxygenAll there is obvious difference in the adsorption capacity that compound shows and mechanism. ZHANG, the research iron and manganese oxides such as SofiaTresintsi are goneExcept the mechanism of As (III) in water body, result shows that the removal mechanism of As (III) is mainly Mn4+To As3+Oxidation and Fe coupleAs5+Suction-operated; Yuan Shikai's Tomb has been prepared ferro manganese composite oxides by test, and studies it to Pb2+、Cd2+Adsorption/desorptionPerformance, by ferro manganese composite oxides and Pb under the experimental conditions such as different pH values, ionic strength, temperature and competition2+、Cd2+Between relation inquire into find, ferro manganese composite oxides is to Pb2+、Cd2+Show very strong adsorption capacity, when both are in systemOne system, ferro manganese composite oxides tends to first adsorb Pb2+。
The preparation method of ferro manganese composite oxides and condition are key factors of research ferro manganese composite oxides absorption property, orderThe preparation method of front ferro manganese composite oxides mainly contains coprecipitation, hydro-thermal method and pyrolysismethod etc., but ferrimanganic prepared by coprecipitationThe character of composite oxides is unstable, and oxidizing process needs the long period, and need to carry out step by step in preparation process, has increasedCost; Hydro-thermal method is a kind of common method of preparation nano material, and material particle purity that it is prepared is high, good dispersion, crystalline substanceShape is good and can control, and production cost is low, but it is not suitable for preparation, some are easy to react with water or be easy to the compound of hydrolysis, decomposition,And ferriferous oxide is easily hydrolyzed. Ferriferous oxide and Mn oxide easy spontaneous reaction under normal temperature and pressure conditions generates compound, waterHot method is to carry out under high-temperature and high-pressure conditions, therefore, directly easily produces agglomeration by hydro-thermal legal system for ferro manganese composite oxides.
Summary of the invention
For above-mentioned the deficiencies in the prior art, the object of this invention is to provide a kind of ferro manganese composite oxides and preparation method thereof, adoptCombine and prepare nano level ferro manganese composite oxides by coprecipitation and hydro-thermal method, first by coprecipitation, two kinds of solution are filledDivide reaction, obtain micron order ferro manganese composite oxides, then change the crystal structure of ferro manganese composite oxides by hydro-thermal method, regulateThe size of its particle diameter and distribution.
Another object of the present invention is to provide the application in chromium (VI) ionic adsorption in water body of this ferro manganese composite oxides.
For achieving the above object, the present invention adopts following technical proposals:
A preparation method for ferro manganese composite oxides, step is as follows:
(1) by ferrous sulfate heptahydrate (FeSO4·7H2O) solution is added drop-wise in liquor potassic permanganate, reacts 1-1.5 at 15-25 DEG C littleTime, reaction obtains maroon suspension, and the pH of course of reaction regulator solution is 3.0-4.0;
(2) maroon suspension step (1) being obtained is transferred in reactor, at 160-200 DEG C, reacts 5-7 hour,Cooling, centrifugal, obtain maroon precipitation, washing precipitation, remains unchanged to the electrical conductivity of cleaning solution;
(3) the maroon precipitation aged at room temperature 3.5-4.5 hour step (2) being obtained, dry, porphyrize, obtains ferrimanganic compoundThe powder of oxide.
In step (1), in ferrous sulfate heptahydrate solution and liquor potassic permanganate, the mol ratio of iron ion and manganese ion is (1-5):1, be preferably 3:1.
In step (1), the rate of addition of ferrous sulfate heptahydrate solution is 1d/s.
In step (1), the dilute hydrochloric acid solution that the pH of course of reaction regulator solution solution used is 1mol/L.
In step (2), adopt low speed centrifuge to carry out centrifugal, centrifugal rotational speed is 2400rpm/min.
Preferably, in step (2), reaction temperature is 180 DEG C, and the reaction time is 6 hours.
Preferably, in step (3), ageing time is 4 hours.
The ferro manganese composite oxides that the method prepares, its specific area is 370-375m2/ g, for particle diameter be evenly distributed shortRod-like nano particle, particle diameter is long is 100-120nm, wide is 50-60nm;
Ferro manganese composite oxides rough surface, forms by tiny circular granular is densely arranged, and solid particle size is comparatively even, andAnd between composite surface fine particle, form pore structure comparatively uniformly, easily chromium in water (VI) ionic adsorption wherein, is enteredAnd pollution of chromium in reduction water.
The present invention further provides the application of ferro manganese composite oxides chromium (VI) ion in adsorbed water, concrete application process is:Ferro manganese composite oxides is joined in pending waste water, and in the pending waste water of every 1L, the addition of ferro manganese composite oxides is(2-4) g, the pH that adjusts pending waste water is 2-11.
The pH of solution and the adsorption effect of ferro manganese composite oxides are closely related, and in this main and solution, Cr (VI) ion exists shapeFormula is relevant, in the time that pH value is 2-7, mainly with Cr2O7 2-Exist, when pH > 7, be mainly CrO4 2-. In solution, be all divalence fromThe Cr of son2O7 2-Content be CrO4 2-One times, and Cr2O7 2-Hobby exists in strongly acidic solution more partially, therefore pH value of solution < 7Time Cr (VI) clearance higher, simultaneously the clearance of Cr (VI) reduces gradually. But in the time of pH < 3, ferrimanganicComposite oxides part can be dissolved by strongly acidic solution, and Fe, the Mn ion generation hydrolysis of formation form corresponding hydroxideCompound, can with chromate ion generation complex reaction, and then increased the clearance to Cr (VI) ion, on the other hand, withThe increase of pH, can there is deprotonation reaction in adsorbent surface, and the positive charge on surface can reduce, its Adsorption of Chromium fromThe ability of son reduces. In alkaline solution, there is a large amount of OH-Ion, can with solution in chromate ion form competition inhaleAttached system, so the clearance of Cr (VI) can reduce in the time of pH > 8.
Beneficial effect of the present invention:
(1) preparation method's reaction condition gentleness of ferro manganese composite oxides of the present invention, in reaction raw materials, ferriferous oxide holdsFacile hydrolysis, ferriferous oxide and Mn oxide easy spontaneous reaction under normal temperature and pressure conditions generates compound, is not suitable for adopting hydro-thermalMethod is directly prepared ferro manganese composite oxides, and the present invention combines by coprecipitation and hydro-thermal method, first makes two by coprecipitationPlant solution and fully react, obtain micron order ferro manganese composite oxides, then change the crystal knot of ferro manganese composite oxides by hydro-thermal methodStructure, regulates the size of its particle diameter and distributes, prepare particle size evenly, regular shape, good dispersion, specific area be largeCorynebacterium nano particle.
(2) the ferro manganese composite oxides rough surface that the present invention prepares, specific area is large, composite surface fine particle itBetween form pore structure comparatively uniformly, easily chromium ion in water is adsorbed wherein, be suitable for the locating of chromate waste water of variable concentrationsReason, clearance is high, and the cost of wastewater treatment is lower.
Brief description of the drawings
Fig. 1 is X-ray diffraction analysis chart;
Fig. 2 is infra-red sepectrometry analysis chart;
Fig. 3 is scanning electron microscope analysis figure;
Fig. 4 is transmission electron microscope analysis figure;
Fig. 5 is that the addition of ferro manganese composite oxides is on the result that affects of absorption Cr (VI);
Fig. 6 is the result that affects of pH value ferro manganese composite oxides absorption Cr (VI);
Fig. 7 is initial concentration adsorbs Cr (VI) result that affects on ferro manganese composite oxides;
Fig. 8 is coexisting ion adsorbs Cr (VI) result that affects on ferro manganese composite oxides.
Detailed description of the invention
Below in conjunction with embodiment, the present invention is further illustrated, should be noted that following explanation is only in order to explain thisBright, its content is not limited.
Embodiment 1: the preparation of ferro manganese composite oxides
Concrete preparation method is as follows:
(1) take the potassium permanganate (KMnO of certain mass4) and ferrous sulfate heptahydrate (FeSO4·7H2O) respectively ultrasonic dissolution in100mL redistilled water (iron is 3:1 with the ratio of manganese amount of substance), waits to recover 25 DEG C, by KMnO4Solution proceeds to 250mLAdd in the round-bottomed flask of magneton, be put on temperature control magnetic stirring apparatus and stir;
(2) by FeSO4·7H2O solution is transferred in 100mL constant pressure funnel, is added drop-wise to KMnO with the speed of 1d/s4In solution, obtain maroon suspension. In course of reaction, constantly use the dilute hydrochloric acid solution regulator solution pH to 3.0-of 1mol/L4.0. Under room temperature, reaction continues 1h;
(3) maroon suspension reaction in (2) being obtained proceeds in the reactor of 100mL, and puts it into electric heating perseveranceIn temperature air dry oven, under 180 DEG C of steady temperatures, react 6h;
(4) after cooling, carry out centrifugally with 2400rpm/min low speed centrifuge, obtain ferro manganese composite oxides maroon precipitation.With redistilled water rinse until suspension electrical conductivity remain unchanged;
(5), by the maroon sediment aged at room temperature 4h obtaining in (4), then put into 60 DEG C of electric heating constant-temperature blowing drying boxesCarry out vacuum constant temperature dry, finally obtain maroon solid. Use agate mortar by solid matter porphyrize, obtain ferrimanganic composite oxygenCompound powder.
Adopt respectively X-ray diffraction analysis (XRD), infra-red sepectrometry analysis (FT-IR), scanning electron microscope analysis (SEM),The test of transmission electron microscope analysis (TEM) and BET specific area is analyzed the ferro manganese composite oxides of preparation, processing method andResult of the test is as follows respectively:
1.X-x ray diffraction analysis x (XRD):
Adopt BrukerD8 type X-ray powder diffraction instrument to test. Testing sample processing: by sample dissolution in acetone,Make the sample powder formation suspension that is evenly distributed with ultrasonic wave processing in solution, draw a small amount of suspension with Dispette, allSpread on sheet glass evenly and make orienting piece, natural drying under room temperature, then put it into and fill the saturated Ca (NO of a cuvette3)In the drier of liquid, after placement 24.0h, make orientation film. Test condition is: graphite flake filtering, Cu target, λ=0.15418Nm, pipe is pressed 40kV, electric current 40mA, walking wide is 0.020(2 θ), sweep limits θ～2 θ.
XRD the results are shown in Figure 1, and as seen from the figure: ferro manganese composite oxides has good crystalline structure, characteristic peak peak shape is sharp-pointed.Obtain ferro manganese composite oxides by XRD analysis software jade5.0 analysis and contain three kinds of thing phases: ferro manganese composite oxides,α-Fe2O3、β-MnO2, and wherein a kind of characteristic peak intensity of thing phase relatively a little less than, this illustrates this material, and in compound, content isFew, or in composite oxides, exist crystal formation relevant with it.
2. infra-red sepectrometry analysis (FT-IR):
Experiment adopts Vertex70 type FTIS to test, and wave-number range is 400-4000cm-1。
FT-IR the results are shown in Figure 2, as seen from the figure: ferro manganese composite oxides is at 3000cm-1～3500cm-1And 1500cm-1～1700cm-1Between all there is characteristic absorption peak, deducibility is at 3228cm-1And 1627cm-1Be respectively-OH of the characteristic peak at two places (fromWater and iron hydroxide) stretching vibration peak and flexural vibrations peak, and 1123cm-1And 435cm-1Two place's characteristic peaks are goethitesAbsworption peak, and the rocking vibration characteristic peak of manganese-OH often appears at 1200cm-1Below.
Can be known by literature query, at 1202cm-1Near the less absworption peak of fluctuation existing wavelength is by hydroxyl in manganese dioxideBase causes, and at 515cm-1The characteristic peak at wavelength place has proved the existence of Mn-O key, and then exists in explanation course of reactionThe electrostatic attraction effect that Mn-O key causes participates in the removal of chromium in water. In addition, at 2359cm-1The characteristic peak that wavelength place existsThe eigen vibration of the carboxyl functional group that may exist with sorbing material surface is relevant. Therefore, can infer ferro manganese composite oxides pairThe adsorption mechanism of chromium is mainly between the complexing and surperficial Mn-O key and chromium ion of composite oxides surface hydroxyl, carboxylThe physical absorption that is combined into of electrostatic attraction effect.
3. scanning electron microscope analysis (SEM):
Experiment adopts the cold field emission scanning electron microscope of JSM-6700F to test, and observes sample surfaces rough trickleThe microscopic features such as size, pattern and the uniformity coefficient of structural change and crystal. Test condition is: accelerating potential: 5kV, amplifiesMultiple: 60000 times.
SEM the results are shown in Figure 3, as seen from the figure: ferro manganese composite oxides surface is very coarse, densely arranged by tiny circular granularForm, solid particle size is comparatively even, but occurs certain agglomeration. Between ferro manganese composite oxides surface detail granuleForm pore structure comparatively uniformly, easily chromium ion in water is adsorbed wherein, and then reduce pollution of chromium in water.
4. transmission electron microscope analysis (TEM):
Experiment adopts JEM-1011 low power transmission electron microscope to test. Get appropriate sample powder and evenly spread upon duplex copper meshMeasure. Test condition is: accelerating potential: 100kV.
TEM the results are shown in Figure 4, as seen from the figure: ferro manganese composite oxides is the corynebacterium nano particle that particle diameter is evenly distributed, and particle diameter is long100nm left and right, wide in 50-60nm interval. Dispersion of materials effect is not fine, there will be certain agglomeration, can roll into a ballBe polymerized to the petal shape nano particle that specific area is larger. This may be because ferrimanganic composite band itself is magnetic, and hasHigh surface energy.
The test of 5.BET specific area
The size of adsorbent specific area is an important indicator that affects sorbing material absorption property. In general, adsorbent is than tableArea is larger, and its adsorption capacity is just stronger. Experiment adopts ST-08A type specific surface area measuring instrument to test.
The test of BET specific area knows that the specific area of this ferro manganese composite oxides is 372.514m2/ g, therefore prepared by the present embodimentFerro manganese composite oxides is solid particle in adsorbed water environment preferably.
Embodiment 2: the adsorption test of ferro manganese composite oxides to chromium in water
1. the impact of the addition of ferro manganese composite oxides on absorption Cr (VI)
Under the certain condition of adsorption density, how many meetings that drop into adsorbent directly affect the height of adsorption efficiency, and for oneQuantitative adsorbent, in solution adsorbate number can directly affect again the degree that the adsorption site position of adsorbent is utilized, so throwThe number that adds adsorbent receives researchers' larger concern on the impact of absorption property. This test will be investigated adsorbent dosage and divideBe not 1.0,2.0,3.0,4.0, impact on ferro manganese composite oxides absorption property when five gradients of 5.0g/L. Concrete test behaviourDo as follows:
Under 25 DEG C of conditions of room temperature, get 5 tool plug conical flasks, add respectively 0.05,0.10,0.15,0.20,0.25g ferrimanganicComposite oxides, then add 50mL concentration of heavy metal ion be 100.0mg/L containing Cr (VI) solution, with concentration be 0.05Rare HCl regulator solution pH value of mol/L is 3.0, seals cyclotron oscillation 1 in 150r/min constant-temperature shaking incubatorH, reaction upon adsorption reaches balance, and then sampling is placed in supercentrifuge, after the centrifugal 5min of 12000rpm, gets supernatantAnalyze, be arranged under room temperature 250C condition, get 5 tool plug conical flasks, add respectively 0.05,0.10,0.15,0.20,0.25g ferro manganese composite oxides, then add 50mL concentration of heavy metal ion be 100.0mg/L containing Cr (VI) solution, useConcentration is that rare HCl regulator solution pH value of 0.05mol/L is 3.0, seals, at 150r/min constant-temperature shaking incubatorMiddle cyclotron oscillation 1h, reaction upon adsorption reaches balance, and then sampling is placed in supercentrifuge, the centrifugal 5min of 12000rpmAfter get supernatant analysis, arrange repeat for 3 times test. Measure the chromic concentration not being adsorbed in supernatant, and calculateCorresponding adsorbance.
Chromic mensuration adopts diphenyl carbazide spectrophotometry, and its general principle is under acid condition, and Cr VI can be withDiphenylcarbazide reaction, generates aubergine compound, and this compound can absorb ultraviolet light at maximum absorption wavelength 540nm place,Molar absorption coefficient is 4 × 104L·mol-1·cm-1. The method is applicable to chromic mensuration in industrial wastewater and surface water. AdoptLight path is the cuvette of 1cm, and its higher limit of measuring concentration is 1mg/L.
The results are shown in Figure 5, as seen from the figure: along with adding the increase of amount of adsorbent, the clearance of Cr (VI) increases gradually, by 61.32%Be increased to 93.29%, and substantially reach balance; And adsorbance reduces thereupon increasing, be reduced to 18.66mg/g by 61.32mg/g.This is mainly because when one timing of adsorbate in solution, along with the increase of quantity of sorbent, adsorbent can provide more adsorption sitePosition, thus the clearance of Cr (VI) promoted; Otherwise in amount one timing of the adsorbent adding, the adsorbate in solution can be along withAdsorbing constantly continuing and reducing, therefore causes the adsorbance of unit mass adsorbent to reduce. When binding equilibrium clearance andAdsorbance curve, can find out that adsorbent reaches capacity substantially in the time that adsorbent dosage is 0.15g, and its saturated extent of adsorption is30.83mg/g。
The impact of 2.pH value ferro manganese composite oxides absorption Cr (VI)
Actual chromate waste water comparison of ingredients complexity, can have Acidity of Aikalinity is not neutral situation, and the difference meeting of pHAffect number and the electronegativity of the surface charge of ferro manganese composite oxides, and then affect the performance of Adsorption heavy metal. This testTake the impact of unitary variant control method research pH on ferro manganese composite oxides absorption property, keep other conditions notBecome, only change the pH value of solution, to study its impact on Adsorption effect, to be future ferro manganese composite oxides existIndustrial application provides reference.
Concrete test procedure is: under 25 DEG C of conditions of room temperature, get some tool plug conical flasks, add 0.15g ferrimanganic combined oxidationThing, then add 50mL concentration of heavy metal ion be 100.0mg/L containing Cr (VI) solution, with rare HCl of 0.5mol/LRegulate pH value to be respectively 2.0,3.0,4.0,5.0,6.0,7.0,8.0,9.0,10.0,11.0,12.0 with NaOH solution,Seal, cyclotron oscillation in 150r/min constant-temperature shaking incubator, adsorption time is 1h, makes adsorption reaction reach balance,Then sampling is placed in supercentrifuge, after the centrifugal 5min of 12000rpm, gets supernatant analysis, arranges and repeats examination for 3 timesTest. Measure the chromic concentration not being adsorbed in supernatant, and calculate corresponding adsorbance.
The results are shown in Figure 6, as seen from the figure: the clearance of Cr (VI) is the same with the variation tendency of adsorbent adsorbance, along with moltenBoth all present reduction trend the increase of liquid pH value, and have small setback. In the time that pH value is increased to 7 gradually from 2, goExcept rate and all reductions rapidly of adsorbance, adsorbance drops to 19.84mg/g by 30.97mg/g; When pH value changes to 12 from 8Time, adsorbance is along with the increase of pH value first increases rear decline, but downward trend is comparatively smooth, and pH value is 12 o'clock, adsorbanceFor 16.85mg/g.
This is main relevant with Cr in solution (VI) ion existence form, in the time that pH value is 2-7, mainly with Cr2O7 2-There is pHWhen > 7, be mainly CrO4 2-. In solution, be all bivalent ions Cr2O7 2-Content be CrO4 2-One times, and Cr2O7 2-More inclined to one sideHobby exists in strongly acidic solution, and therefore the clearance of Cr (VI) is higher when pH value of solution < 7, and the clearance of Cr (VI) is simultaneouslyReduce gradually. But in the time of pH < 3, ferro manganese composite oxides part can be dissolved by strongly acidic solution, the Fe of formation,Mn ion generation hydrolysis forms corresponding oxyhydroxide, can with chromate ion generation complex reaction, and then increasedTo the clearance of Cr (VI) ion, so be less than at 3 o'clock at pH, there is maximum Cr (VI) ion remaval rate. On the other hand, withThe increase of pH, can there is deprotonation reaction in adsorbent surface, and the positive charge on surface can reduce, its Adsorption of Chromium fromThe ability of son reduces. In alkaline solution, there is a large amount of OH-Ion, can with solution in chromate ion form competition inhaleAttached system, so the clearance of Cr (VI) can reduce in the time of pH > 8.
3. initial concentration adsorbs the impact of Cr (VI) on ferro manganese composite oxides
The impact of research initial concentration on ferro manganese composite oxides absorption property, draws the song that is related to of clearance, adsorbance and timeLine, can more directly recognize the situation such as the rate of adsorption, adsorption equilibrium of different absorption systems, to for probing into better ironManganese composite oxide adsorption dynamics adsorption kinetics and adsorption isotherm feature provide Data support.
Concrete test procedure is: under 25 DEG C of conditions of room temperature, get some tool plug conical flasks, add 0.15g ferrimanganic combined oxidationThing, then adds respectively that 50mL initial concentration is 5.0,20.0,40.0,50.0,60.0,80.0, the containing of 100.0mg/LCr (VI) solution, regulating pH value with rare HCl solution of 0.5mol/L is 3.0, seals, at 150r/min constant temperature oscillationCyclotron oscillation in incubator, adsorption time is 1h, in adsorption process, samples once every 5min, then sampling is placed at a high speedIn centrifuge, after the centrifugal 5min of 12000rpm, get supernatant analysis, arrange and repeat test for 3 times. Measure in supernatantThe chromic concentration not being adsorbed, and calculate corresponding clearance and adsorbance.
The results are shown in Figure 7, as seen from the figure: along with the increase of initial concentration, the clearance of Cr (VI) can reduce gradually, but remainsThe higher rate of adsorption, and the adsorbance of unit mass adsorbent is increasing gradually. Initial concentration is increased to 100 from 20mg/LMg/L, Cr (VI) clearance drops to 92.5% from 99.13%, and corresponding, adsorbance is increased to 30.83mg/g by 6.61mg/g.This is mainly because the adsorption site position that adsorbent surface can provide is limited, along with the increase of adsorbate, and the formation between adsorbateKeen competition, causes the unit interval to remove the Efficiency Decreasing of Cr (VI) thereby extend adsorption time.
In the situation that hexavalent chromium concentration is 5mg/L, the clearance of Cr (VI) can reach 91.54%, but will be lower than initial concentrationClearance when 20mg/L, it be 5mg/L for concentration is excessive containing Cr (VI) solution that this explanation adds the adsorbent of 0.15g, the adsorption site position of adsorbent surface can not get sufficient utilization. Along with chromium initial concentration is increased to 100mg/L by 20mg/L,Adsorbance is in continuous increase, and chief reason may be that the adsorption activity point position of adsorbent surface is not fully utilized, and inhalesReaction enclosure does not reach balance.
4. coexisting ion adsorbs the impact of Cr (VI) on ferro manganese composite oxides
Cr VI exists with chromate anionic form in acid solution, and contains Cl in actual waste water-，SO4 2-，PO4 3-DengAnion, therefore inquires into Cl-，SO4 2-，PO4 3-Plasma is the impact on adsorption effect on ferro manganese composite oxides. Concrete testStep is as follows:
(1) under 25 DEG C of conditions of room temperature, get 3 tool plug conical flasks, change and add 0.15g ferro manganese composite oxides, thenAdd 50mL initial concentration be 100.0mg/L containing Cr (VI) solution, use respectively rare HCl, the H of 0.5mol/L2SO4、H3PO4It is 3.0 that solution regulates pH value;
(2) separately get 1 tool plug conical flask, adding successively 0.15g ferro manganese composite oxides and 50mL initial concentration is 100.0Mg/L containing Cr (VI) solution, adding the NH of 0.5mol4Cl solution, and regulate pH with the rare HCl solution of 0.5mol/LValue is 3.0;
(3) seal, cyclotron oscillation in 150r/min constant-temperature shaking incubator, adsorption time is 1h, in adsorption process,Sample once every 5min, then sampling is placed in supercentrifuge, gets supernatant and carry out after the centrifugal 5min of 12000rpmAnalyze, arrange and repeat test for 3 times. Measure the chromic concentration not being adsorbed in supernatant, and calculate corresponding clearance andAdsorbance.
The results are shown in Figure 8, as seen from the figure: be 3.0 at pH, chromium initial concentration is 100mg/L, and adsorbent dosage isUnder the condition of 3g/L, by with single Cl-Ion impact is compared, SO4 2-And PO4 3-All can reduce the suction of ferro manganese composite oxidesAttached speed, and its corresponding unit interval adsorbance reduces to some extent. SO4 2-As time goes on ion population trend be, composite oxygenCompound to the adsorbance of chromium in continuous increase, but all lower than there being Cl in solution-Adsorbance when ion; When there being PO in solution4 3-Time, in adsorbance 5min, reach maximum, adsorbance slightly declines thereafter, this may with chromium of adsorbent surface absorption fromThere is desorption in son, constantly departs from relevant from composite oxides surface. Can judge that accordingly counter anion is to adsorption effectInhibitory effect is SO4 2->PO4 3-. In addition, the NH that coexists4 +The trend that affects and the Cl of ion pair adsorption effect-The trend that affects substantiallyUnanimously, but it can increase the adsorbance of ferro manganese composite oxides to chromium.
5. the Exploration of Mechanism of ferro manganese composite oxides absorption Cr (VI)
Relevant characterization analysis result based on ferro manganese composite oxides and adsorption dynamics adsorption kinetics and thermoisopleth result of study, we are to ironThe mechanism of manganese composite oxide adsorbing hexavalent chromium is inferred, thinks that ferro manganese composite oxides shows as many to the adsorption process of chromiumMolecular layer physical absorption, and can occur protonated and go from the great amount of hydroxy group of composite oxides surface existence and carboxyl functional groupProtonation process, to adsorption mechanism deployment analysis, is embodied in:
In acid solution, the hydroxyl on ferro manganese composite oxides surface can with solution in H+In conjunction with, formation-OH2 +Functional group,These functional groups can with solution in chromate anion there is complex reaction on ferro manganese composite oxides surface, and then reachThe object of middle chromium dewaters. But along with the increase of pH, composite oxides surface-OH2 +Functional group is fewer and feweri, soThe effect of ferro manganese composite oxides absorption Cr (VI) decreases. When solution is under neutrality or alkali condition, ferrimanganic combined oxidationCan there is deprotonation reaction and form electronegative-COOH in the carboxyl functional group on thing surface-Functional group, and its electronegativity is along with solutionThe increase meeting of pH value constantly strengthens ,-COOH-Functional group can with solution in chromate anion form, form competitive Adsorption,And then inhibition ferro manganese composite oxides adsorbs chromate ion. In addition, also there is Mn-O key in ferro manganese composite oxides surface,It can and chromium ion between electrostatic attraction effect, and then play the object of removing chromium in water.
In sum, the mechanism of ferro manganese composite oxides Adsorption of Chromium is mainly by composite oxides surface hydroxyl and carboxyl functional groupThe polymolecular layer physical absorption causing is combined in electrostatic attraction effect between collaborative complexing and surperficial Mn-O key and chromium ionProcess.
Embodiment 3: cost accounting
(1) cost of material: 400 yuan/ton, ferrous sulfate; 10000 yuan/ton, potassium permanganate;
According to experiment showed, ferrous sulfate and and the mass ratio of potassium permanganate be 5:1, so cost of material is:
400 yuan, 1 ton of ferrous sulfate, 2000 yuan, 200kg potassium permanganate, totally 2400 yuan;
These raw materials can produce 1 ton, adsorbent, and the cost of 1 ton of adsorbent is 2400 yuan.
(2) 1g sorbent treatment 2.5L waste water, 1kg processes 2500L (2.5m3), process 2500m for 1 ton3Process 2500m for 2400 yuan3Water, 0.96 yuan process 1m3Waste water.
(3), in prior art, adopt conventional chemical Treatment 1kgCr6+Dosing and expense in table 1.
Table 1 is commonly used chemical Treatment 1kgCr6+Dosing and expense comparison
Table 1 data are drawn from Qiu Mingliang, Luo Dan, Ding Xiaojing, Liu Yingna. the cost compare of chemical precipitation method processing waste water containing chrome[J]. environmental protection and recycling economy, 2012,3:61-71.
Cr in pending chromate waste water6+Concentration be 100mg/L, now process 1m3Chromate waste water need 0.96 yuan of medicament expenseWith, process 0.1kgCr6+Reagent cost be 0.96 yuan, so adopt method of the present invention to process 1kgCr6+Medicament expenseWith being 9.6 yuan. Than the medicament expense use of chemical method processing waste water containing chrome conventional in prior art, iron prepared by the present inventionManganese composite oxide, as sorbent treatment chromate waste water, can reduce the expense of processing significantly.
Claims (9)
1. a preparation method for ferro manganese composite oxides, is characterized in that, step is as follows:
(1) ferrous sulfate heptahydrate solution is added drop-wise in liquor potassic permanganate, reacts 1-1.5 hour at 15-25 DEG C, reaction obtainsMaroon suspension, the pH of course of reaction regulator solution is 3.0-4.0;
(2) maroon suspension step (1) being obtained is transferred in reactor, at 160-200 DEG C, reacts 5-7 hour, coldBut, centrifugal, obtain maroon precipitation, washing precipitation, remains unchanged to the electrical conductivity of cleaning solution;
(3) the maroon precipitation aged at room temperature 3.5-4.5 hour step (2) being obtained, dry, porphyrize, obtains ferrimanganic compoundThe powder of oxide;
In step (1), the dilute hydrochloric acid solution that the pH of course of reaction regulator solution solution used is 1mol/L.
2. the preparation method of ferro manganese composite oxides as claimed in claim 1, is characterized in that, in step (1), and seven water sulphurIn acid ferrous iron solution and liquor potassic permanganate, the mol ratio of iron ion and manganese ion is (1-5): 1.
3. the preparation method of ferro manganese composite oxides as claimed in claim 2, is characterized in that, in step (1), and seven water sulphurIn acid ferrous iron solution and liquor potassic permanganate, the mol ratio of iron ion and manganese ion is 3:1.
4. the preparation method of ferro manganese composite oxides as claimed in claim 1, is characterized in that, in step (1), and seven water sulphurThe rate of addition of acid ferrous iron solution is 1d/s.
5. the preparation method of ferro manganese composite oxides as claimed in claim 1, is characterized in that, in step (2), adopts lowSpeed centrifuge carries out centrifugal, and centrifugal rotational speed is 2400rpm/min.
6. the preparation method of ferro manganese composite oxides as claimed in claim 1, is characterized in that, in step (2), and reaction temperatureDegree is 180 DEG C, and the reaction time is 6 hours.
7. the preparation method of ferro manganese composite oxides as claimed in claim 1, is characterized in that, in step (3), when agingBetween be 4 hours.
8. the ferro manganese composite oxides that the method described in claim 1 to 7 any one prepares, is characterized in that, ferrimanganic is multipleThe specific area of closing oxide is 370-375m2/ g, is the corynebacterium nano particle that particle diameter is evenly distributed, and particle diameter length is100-120nm, wide is 50-60nm.
9. the application of ferro manganese composite oxides claimed in claim 8 hexavalent chromium in adsorbing and removing water body, is characterized in that,Application process is: ferro manganese composite oxides is joined in pending waste water to ferro manganese composite oxides in the pending waste water of every 1LAddition is (2-4) g, and the pH that adjusts pending waste water is 2-11.
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