CN108246110A - A kind of attapulgite modified PVDF ultrafiltration membrane, preparation method and its application in protein solution filtration - Google Patents

A kind of attapulgite modified PVDF ultrafiltration membrane, preparation method and its application in protein solution filtration Download PDF

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CN108246110A
CN108246110A CN201810015083.XA CN201810015083A CN108246110A CN 108246110 A CN108246110 A CN 108246110A CN 201810015083 A CN201810015083 A CN 201810015083A CN 108246110 A CN108246110 A CN 108246110A
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attapulgite
pvdf
modified
ultrafiltration membrane
film
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CN108246110B (en
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薛爱莲
周守勇
赵宜江
李梅生
王蓉
邢卫红
许家兴
胡磊
杨大伟
张艳
张莉莉
黄进
张玉洁
吴飞跃
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Huaiyin Normal University
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D61/00—Processes of separation using semi-permeable membranes, e.g. dialysis, osmosis or ultrafiltration; Apparatus, accessories or auxiliary operations specially adapted therefor
    • B01D61/14—Ultrafiltration; Microfiltration
    • B01D61/145—Ultrafiltration
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D61/00—Processes of separation using semi-permeable membranes, e.g. dialysis, osmosis or ultrafiltration; Apparatus, accessories or auxiliary operations specially adapted therefor
    • B01D61/14—Ultrafiltration; Microfiltration
    • B01D61/18—Apparatus therefor
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D67/00—Processes specially adapted for manufacturing semi-permeable membranes for separation processes or apparatus
    • B01D67/0079—Manufacture of membranes comprising organic and inorganic components
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D69/00—Semi-permeable membranes for separation processes or apparatus characterised by their form, structure or properties; Manufacturing processes specially adapted therefor
    • B01D69/02—Semi-permeable membranes for separation processes or apparatus characterised by their form, structure or properties; Manufacturing processes specially adapted therefor characterised by their properties
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D71/00—Semi-permeable membranes for separation processes or apparatus characterised by the material; Manufacturing processes specially adapted therefor
    • B01D71/02—Inorganic material
    • B01D71/024—Oxides
    • B01D71/027—Silicium oxide
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D71/00—Semi-permeable membranes for separation processes or apparatus characterised by the material; Manufacturing processes specially adapted therefor
    • B01D71/06—Organic material
    • B01D71/30—Polyalkenyl halides
    • B01D71/32—Polyalkenyl halides containing fluorine atoms
    • B01D71/34—Polyvinylidene fluoride
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D71/00—Semi-permeable membranes for separation processes or apparatus characterised by the material; Manufacturing processes specially adapted therefor
    • B01D71/06—Organic material
    • B01D71/76—Macromolecular material not specifically provided for in a single one of groups B01D71/08 - B01D71/74
    • B01D71/82—Macromolecular material not specifically provided for in a single one of groups B01D71/08 - B01D71/74 characterised by the presence of specified groups, e.g. introduced by chemical after-treatment
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2325/00—Details relating to properties of membranes
    • B01D2325/02—Details relating to pores or porosity of the membranes

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  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Engineering & Computer Science (AREA)
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  • Separation Using Semi-Permeable Membranes (AREA)

Abstract

The invention discloses a kind of attapulgite modified PVDF ultrafiltration membrane, preparation method and its applications in the pollution of anti-protein adsorption.Using triethyl phosphate as solvent, by a certain amount of polymethylacrylic acid N, the attapulgite ultrasonic disperse that N dimethylaminoethyls PDMAEMA was modified is wherein, it adds in Kynoar powder and vigorous mechanical agitation extremely dissolves, it adds pore-foaming agent polyethylene glycol to stir evenly, last standing and defoaming obtains casting solution；Using water as coagulating bath, ultrafiltration membrane is made using immersion precipitation phase inversion process.The present invention is by by polymethylacrylic acid N, the attapulgite that N dimethylaminoethyls were modified is introduced into polyvinylidene fluoride (PVDF) ultrafiltration membrane, both the unique nanofibrous structures of attapulgite can be utilized to form tridimensional network with polyvinylidene fluoride material, so as to be effectively improved the structure of pure polyvinylidene fluoride (PVDF) ultrafiltration membrane and intensity；Permeability of the membrane and hydrophily are improved using the high-hydrophilic of attapulgite again, realizes resistance tocrocking and easy cleaning.

Description

A kind of attapulgite modified PVDF ultrafiltration membrane, preparation method and its in protein solution Application in filtering
Technical field
The present invention relates to a kind of attapulgite modified PVDF ultrafiltration membrane, preparation method and its in protein solution filtration Using belonging to separation membrane technical field.
Background technology
Kynoar is a kind of material of preparing of function admirable, has good chemical stability, high temperature resistant, oxytolerant The advantages that change, corrosion-resistant, good toughness, high intensity, is widely used in the fields such as food, medicine and sewage disposal.However, gather inclined fluorine The low-surface-energy of ethylene so that film surface hydrophobicity is stronger, adsorbed in oil-water separation or protein solution containing system it is seriously polluted, Flux decline speed is fast, and organic matter is liable to stick to film surface, causes Pore Blocking, forms fouling membrane, and the performance of film is difficult to fill Distribution is waved.It is current popular research direction to develop pollution-resistant membrane.The hydrophily raising of film can reduce solute retention, special It is not that contact between protein and non-directional combine, the especially absorption of biological pollution substance.Therefore, the hydrophilic of film is improved Property, fouling membrane is reduced, it is the direction that current scholar studies always to make it have permeation flux that is higher and stablizing.
Mainly there are surface modification and two major class of blending and modifying to the method for Kynoar membrane modifying at present.Surface is modified master There are surface coating and surface grafting.The former is easy to run off easy to operate but modifying agent during film use, and the modification to come off Substance can also pollute film；The latter need to post-process and be modified not uniform enough or even can block die hole, damage film properties.
Blending and modifying refers to hydroaropic substance and Kynoar matrix material carrying out physical blending, filming technology letter It is single, complicated pre-treatment and post processing are not needed to, it is easy to operate efficient, it is most common polymeric membrane method of modifying.Blending The compatibility of material and Kynoar matrix directly affects the formation of film, and common intermingling material includes having containing hydrophilic segment Machine copolymer and inorganic nano-particle etc..
It is presently used for the inorganic nano-particle TiO of intermingling material2、SiO2、Al2O3Etc. being graininess, these nanoscales Inorganic particulate easily come off in inversion of phases film forming procedure, influence the performance of film.In contrast, the 1-dimention nanos such as carbon nanotube Material has superpower mechanical property, high length-width ratio and high-ratio surface, and the 1-dimention nano material being dispersed in polymeric membrane Material, its stability in membrane material can be effectively improved by the spiral winding of macromolecular chain.However, carbon nanotube etc. is artificial Synthesizing one-dimensional nano material manufacturing cost is high, under purity and low output, it is difficult to disperse, which greatly limits it in film blending and modifying In scale application.
Attapulgite is the main composition of non-metal clay mineral attapulgite clay, is a kind of typical layer chain structure Alumina magnesia silicate containing Shuifu County.Attapulgite is in rhabdolith combination, a diameter of 20~70 nm of single stick crystalline substance, length About 0.5 ~ 5 μm.Due to the special 1-dimention nano fibrous structure of attapulgite, and surface can be into rich in great amount of hydroxy group The progress of one step is macromolecule modified, therefore attapulgite can be as a kind of excellent pvdf membrane material blending additive.
Invention content
The object of the present invention is to provide a kind of pollution-resistant polyvinylidene fluoride (PVDF) ultrafiltration membranes, utilize the unique nanometer of attapulgite The tridimensional network that fibre structure and Kynoar are formed is so as to be effectively improved the structure of polyvinylidene fluoride (PVDF) ultrafiltration membrane and by force Degree improves permeability of the membrane and hydrophily using attapulgite high-hydrophilic, realizes resistance tocrocking and easy cleaning.
The first aspect of the invention provides：
A kind of modified attapulgite, the surface of the modified attapulgite have such as formula（I）Shown structure：
（I）；
Wherein, n is the arbitrary integer between 1~10000.
The second aspect of the invention provides：
A kind of attapulgite is modified PVDF ultrafiltration membrane, and above-mentioned modified attapulgite is also mixed in PVDF ultrafiltration membrane.
In one embodiment, the weight ratio between the modified attapulgite and PVDF is 1~10:20.
The second aspect of the invention provides：
A kind of attapulgite is modified the preparation method of PVDF ultrafiltration membrane, includes the following steps：
The coupling agent of the key containing C=C is grafted on the surface of attapulgite by the 1st step；
2nd step, by methacrylic acid N, the attapulgite of coupling agent grafting that N- dimethylaminoethyls are obtained with the 1st step is gathered Close reaction；
The modified attapulgite that 2nd step obtains is added in into PVDF casting solutions, is prepared by phase conversion method by the 3rd step Ultrafiltration membrane.
In one embodiment, in the 1st step, the coupling agent of the key containing C=C is silane coupling agent MPS；Concave convex rod The w/v of stone and the coupling agent of the key containing C=C is 12g：5~15mL, graft reaction carry out under the conditions of organic solvent, institute The organic solvent stated is toluene, and 55~70 DEG C, 2~6h of reaction time of reaction temperature, product need to be washed, dry after reaction Processing.
In one embodiment, in the 2nd step, methacrylic acid N, N- dimethylaminoethyl and coupling agent grafting The weight ratio of attapulgite be 0.5~6：2；Polymeric reaction temperature is 75~85 DEG C, and the reaction time is 1~5h, and reaction terminates Product needs washed, drying process afterwards.
In one embodiment, in the 3rd step, PVDF, organic solvent, pore-foaming agent are contained in PVDF casting solutions, The mass ratio of modified attapulgite and PVDF, organic solvent, pore-foaming agent is：0.05~0.42：10~14：1~5：30~60；Institute The organic solvent stated is triethyl phosphate；The pore-foaming agent is PEG.
In one embodiment, in the 3rd step, phase conversion method is by scratching PVDF casting solutions in tablet It is upper to be formed a film by immersion precipitation phase inversion process.
The third aspect of the invention provides：
Above-mentioned attapulgite is modified application of the PVDF ultrafiltration membrane in liquid filtering.
In one embodiment, contain protein in the liquid.
The fourth aspect of the invention provides：
Application of the modified attapulgite in polymer film preparation.
In the application, modified attapulgite for reducing polymer film to the absorption of protein, reduce in polymer Big hole defect, reduction pore-size distribution width, improve porosity, improve thermal stability, improve tensile strength, improve break elongation Rate improves hydrophily, improves water flux, improves to dirty containing flux, the reduction filter process film during protein solution filtration Irreversible membrane pollutes in flux recovery rate or reduction filter process after staining index MFI, raising Membrane cleaning.
Advantageous effect
1. the pollution-resistant polyvinylidene fluoride (PVDF) ultrafiltration membrane is both using the typical nanofibrous structures of attapulgite and its with gathering inclined fluorine The tridimensional network that ethylene is formed effectively improves the structure and intensity of polyvinylidene fluoride (PVDF) ultrafiltration membrane, and utilizes attapulgite High-hydrophilic effectively improves the permeability and hydrophily of polyvinylidene fluoride film, realizes its antipollution easy cleaning.2. with tradition Inorganic nano-particle is compared, and attapulgite is a kind of typical monodimension nanometer material, internal multichannel, high-specific surface area, and China's large storage capacity, of low cost, to environment without negative effect, cost performance is substantially better than artificial synthesized 1-dimention nano undulation degree Material.3. attapulgite surface is rich in hydroxyl, this provides convenience for the further functional modification in surface, and with it is unmodified recessed Convex stick stone is compared, by its surface grafting polymethylacrylic acid N, N- dimethylaminoethyl, improve inorganic nano-particle with Compatibility between macromolecule improves the dispersibility of attapulgite, and can improve it in film by the winding of macromolecular chain Stability.
Description of the drawings
Fig. 1 is the infrared spectrogram of modified attapulgite；
Fig. 2 is the XRD spectrum of modified attapulgite；
Fig. 3 is material SEM figures；Wherein, a regions are PGS；B regions are PGS-MPS；C regions are PGS-g-PDMAEMA；
Fig. 4 is the EDX elemental analysis results of modified attapulgite；
Fig. 5 is the Adsorption experimental results comparison diagram of albumen；
Fig. 6 is the upper surface infrared spectrum of film；
Cortex, bottom surface and the cross-section diagram of the pure pvdf membranes of Fig. 7 and hybrid films；
The graph of pore diameter distribution of Fig. 8 difference films；
Fig. 9 is the thermogravimetric curve figure of pure PVDF ultrafiltration membrane and hybrid films；
Figure 10 is the contact angle comparison diagram of the PGS-g-PDMAEMA films of different content；
The starting of the film of Figure 11 difference modifier contents and the contact angle comparison diagram after 200 s；
Figure 12 is the dynamic contact angle comparison diagram of the PGS-g-PDMAEMA films of different content；
Figure 13 is the pure water flux comparison diagram of the PGS-g-PDMAEMA films of different content；
Figure 14 is adsorbance comparison diagram of the film to BSA；
Figure 15 membrane filtration BSA permeation fluxes change over time curve graph；
The rejection of Figure 16 films and steady seepage flux vs figure；
Figure 17 films are to the dynamic adsorbance comparison diagram of BSA；
Figure 18 index of membrane fouling comparison diagrams；
The flux recovery rate comparison diagram of PVDF/P0 and PVDF/P4 under Figure 19 difference cleaning ways；
The steady seepage flux of Figure 20 films and flux recovery rate comparison diagram；
The pollution resistance analysis comparison diagram of Figure 21 films.
Specific embodiment
Attapulgite（Attapulgite, ATP）It is the main composition of non-metal clay mineral attapulgite clay.1980 Recommend its English entitled Palygorskite years Bailey（PGS）.Attapulgite belongs to sepiolite group, is a kind of typical layer chain The alumina magnesia silicate containing Shuifu County of shape structure, common structural formula are Mg5(Si4O10)2(OH)2(OH2)4·4H2O.Concave convex rod Stone is in rhabdolith combination, and brilliant a diameter of 20 ~ 70 nm of single stick, length is about 0.5 ~ 5 μm.Each 2:1 type chain stratiform In structure sheaf, 180 ° are overturn along y-axis tetrahedron top, you can form the link layer for being parallel to x-axis every some cycles.This spy Different structure feature causes attapulgite to meet the feature of monodimension nanometer material, can form the one-dimensional of the nm of 0.38 nm × 0.63 Duct.The special diameter and duct that attapulgite has, interior Extra specific surface area is big, and possesses special surface charge distribution and more Remaining positive and negative charge, the high-specific surface area that attapulgite has, distribution of charges are uneven；Due to attapulgite surface be rich in it is big Negative electrical charge and silicone hydroxyl are measured, organic modification can be carried out to it with coupling agent and polymer etc..
Attapulgite surface polymethylacrylic acid N, N- dimethylaminoethyls（PDMAEMA）Grafting and modifying is divided into two steps, stream Journey is as follows, and first attapulgite is modified with silane coupling agent MPS, its surface is made then to draw rich in carbon-carbon double bond Send out agent potassium peroxydisulfate（KPS）Under the action of using free yl graft polymerization method in modified attapulgite surface grafting PDMAEMA.
The preparation of 1 modified attapulgite of embodiment
The preparation of PGS-MPS
In the four-neck flask of 500 mL, dry 12 g attapulgites and 200 mL toluene are sequentially added, 60 are protected in nitrogen Mechanical agitation is sufficiently mixed it under DEG C oil bath, and 10 mL silane coupling agent MPS are added dropwise after 30 min dropwise, are added dropwise subsequent 4 h of continuous reaction.After the completion of reaction, product is centrifuged, is washed three times with absolute ethyl alcohol, to remove unreacted silicon in dereaction The product finally obtained at 60 DEG C is dried in vacuo, is ground after 5 h by alkane coupling agent and solvent, you can obtains first step modification Product PGS-MPS.
The preparation of PGS-g-PDMAEMA
250 mL four-neck flasks, sequentially add 2 g PGS-MPS and 80 mL deionized waters, after 2 h of ultrasonic disperse, in 80 DEG C of oil The lower mechanical agitation of bath is added dropwise 0.06 g KPS solution with dropping funel after 30 min, is slowly added dropwise after 1 h after removing polymerization inhibitor DMAEMA, respectively 0.5 g, 2 g, 4 g, 6 g, the reaction was continued under nitrogen protection 3 h.Product centrifugation point after the completion of reaction From being washed with deionized three times later, monomer and initiator extra in solution are removed, is ground after being finally freeze-dried 24 h Obtain final product PGS-g-PDMAEMA.
The characterization of modified attapulgite
（1）Infrared spectrum measurement（FTIR）：The solid powder and potassium bromide that will be obtained after reaction（KBr）Solid mixed grinding, grinds Transparent thin slice is made, using infrared spectrometer AVATAR 360FT-IR to attapulgite and modified attapulgite（PGS、 PGS-MPS、PGS-g-PGS）Infrared spectrum analysis is carried out, scanning accuracy is sets 4, and scanning times are set as 32 times, and scanning range is set For 4000 cm-1~500 cm-1.As shown in Figure 1, by curve（a）（b）It is found that（b）In 1305 cm-1Nearby there is new peak, it is right C-O stretching vibration peaks are answered, in 1708 cm of wavelength-1There is the stretching vibration peak of C=O-O ester bonds in place, in 2970 cm-1Nearby go out - CH is showed2The characteristic peak of methylene, after this illustrates that the first step is modified, silane coupling agent is successfully grafted on attapulgite. Observation（b）（c）Curve,（c）Curve is in 1727 cm of wavelength-1There is obvious characteristic peak in place, and C=O carbonyls feature is inhaled in corresponding ester group Receive peak, 2722 cm of wavelength-1, 2822 cm-1Neighbouring appearance-N (CH3)2The stretching vibration absworption peak of c h bond in tertiary amino group, And 2970 cm-1Locate corresponding methylene absorption peak strength to be remarkably reinforced.This illustrates that monomer DMAEMA is successfully grafted on concave convex rod Shi Shang.
（2）X-ray diffraction spectra is analyzed（XRD）：Crystalline form analysis, pipe electricity are carried out to attapulgite using X-ray diffractometer Stream is set as 40 mA, and tube voltage is set as 45 kV, and scanning model is 5 °< 2θ < 80 °.Attapulgite is analyzed using X difraction spectrums Whether crystal form generates variation after before modification.As shown in Fig. 2, attapulgite PGS and modified attapulgite PGS-MPS, PGS-g- There is strong characteristic peak when 2 θ are 8.3 °, 13.8 °, 16.4 °, 19.8 °, 27.5 ° and 35.4 ° in PDMAEMA, 110 crystal faces, 200 crystal faces, 130 crystal faces, 040 crystal face, 400 crystal faces and 161 crystal faces of attapulgite are corresponded to respectively.It is wherein most strong Corresponding 110 crystal face of characteristic peak be attapulgite hydroxyl diffraction maximum, observe modified attapulgite XRD curves and find not There are other characteristic peaks, this illustrates that attapulgite crystal structure of in modifying process itself is not destroyed, monomer DMAEMA is grafted on attapulgite surface.
（3）Thermogravimetric analysis（TG）：In a nitrogen atmosphere, thermogravimetric analysis is carried out using thermogravimetric analyzer, heating rate is set as 10 DEG C/min, Range of measuring temp is 20 DEG C ~ 800 DEG C.Grafting rate is calculated using the following formula.
GR represents grafting rate（%）；ΔW 1 The attapulgite modified for the first step（PGS-MPS）It is warming up to from 300 DEG C Weightlessness at 700 DEG C（%）；ΔW 2 Represent the attapulgite after modified grafting（PGS-g-PDMAEMA）It is warming up to from 300 DEG C Weightlessness during 700 DEG C；W p For PGS-g-PDMAEMA when temperature is 700 DEG C remaining weight (%).
（4）Scanning electron microscope and energy spectrum analysis（SEM、EDX）：Attapulgite is observed using cold field emission scanning electron microscope Topographical property, after analyzing it before modification pattern variation.Attapulgite is placed under infrared lamp dry 10min, is vacuumized Voltage under high vacuum pattern, is set as 10kV by metal spraying 90s after 1min.Using cold field emission scanning electron microscopic observation PGS, PGS-MPS With the pattern of PGS-g-PDMAEMA, energy spectrum analysis sample surfaces element composition and content are utilized.As shown in figure 3, compared with PGS, PGS-MPS, PGS-g-PDMAEMA surface become uneven and more loose, the product that especially final step is modified The surface of PGS-g-PDMAEMA is the most coarse, this is primarily due to attapulgite surface grafting organic matter.It can be with from Fig. 4 It was found that PGS-g-PDMAEMA has compared more than PGS-MPS N element, content 4.98%；The content of C is risen to by 13.19% 32.59%, the content of other elements O, Mg, Si etc. have different degrees of reduction, absolutely prove that monomer PDMAEMA is successfully grafted Attapulgite surface is arrived.
（5）Attapulgite is to the adsorption experiment of albumen
The drafting of BSA solution standard curves：The BSA solution of accurate configuration different quality concentration, with visible spectrophotometer most The absorbance of various concentration is measured under 278 nm of big absorbing wavelength.
Adsorption experiment：The attapulgite for weighing 30 mg is poured into the conical flask of 250 mL, molten with the phosphoric acid buffer of pH=7.4 The BSA solution of 0.1 g/L is configured in liquid, and pipettes the solution that 30 mL have been configured with pipette and be transferred in conical flask, after sealing Conical flask be put into the shaking table of 25 DEG C of water-baths, taken out after 300 min, the mixture in conical flask poured into centrifuge tube.Turning Speed takes supernatant liquor, with visible ray photometer in absorbing wavelength to be surveyed at 278 nm to centrifuge 5 min under 4500 r/min Determine absorbance, corresponding mass concentration is calculated using standard working curve, adsorbance is calculated using following formula.
qAdsorbance (mg/g) for sample after 300 min；VVolume (L) for BSA solution；mQuality (g) for sample；C 0 Initial concentration (g/L) for BSA solution；C f Concentration (g/L) for BSA solution after absorption.
Tri- kinds of samples of PGS, PGS-MPS and PGS-g-PDMAEMA are at 25 DEG C, it is to bovine serum albumin after adsorbing 300 min （BSA）Adsorbance it is as shown in Figure 5.As can be seen from the figure PGS is to the adsorbance very little of BSA, about 23.89 mg/g；PGS- The adsorbance of MPS is maximum, reaches 65.12 mg/g；And the adsorbance of PGS-g-PDMAEMA is minimum, only 5.03 mg/g.Explanation PGS-g-PDMAEMA will not increase the absorption to albumen as the blending additive of polyvinylidene fluoride (PVDF) ultrafiltration membrane, will not cause straight Connect pollution.
The preparation of 2 ultrafiltration membrane of embodiment
It is prepared by casting solution：48 g triethyl phosphates are added in screw thread reagent bottle（TEP）As solvent, certain mass is added Modified attapulgite adds in 12 g Kynoar after 2 h of ultrasonic disperse（PVDF）Powder, the mechanical agitation under 80 DEG C of oil baths 24 h add the PEG-400 of 3 g as pore-foaming agent, then proceed to 24 h of stirring, mixture is made to form uniform casting solution.
Casting solution deaeration：The casting solution being configured is put into vacuum drying chamber, 3 h deaerations are vacuumized at 80 DEG C.
Knifing forms a film：Using 4340 type knifing machines of Elcometer, set temperature is 80 DEG C, and it is 200 to adjust scraper registration μm, it by casting solution curtain coating on clean glass plate, is formed a film using immersion precipitation phase inversion process, the air evaporation time is 5 s, is coagulated Gu bath temperature is 20 DEG C.
The preparation of dry film：Wet film is immersed in absolute ethyl alcohol, shifts being positioned over hexane solution after 6 h, is taken out after 4 h Naturally dry.
The casting solution composition of different PGS-g-PDMAEMA additive amounts is as shown in the table：
The characterization of ultrafiltration membrane
（1）Film surface FTIR-ATR is analyzed：Film surface chemical composition is analyzed using infrared spectrometer, scanning accuracy is set as 4, scanning times are set as 32 times, and scanning range is set as 4000 cm-1~500 cm-1.Infrared analysis is carried out to film surface, such as Fig. 6 institutes Show, with the increase of modifying agent additive amount, PVDF hybrid films are in 1650 cm-1The peak intensity at place gradually increases, and C in corresponding ester group= O carbonyl characteristic absorption peaks[88].This illustrates that modifying agent PGS-g-PDMAEMA is successfully mixed into film.
（2）Electron microscope, the aperture analysis of porosity of film：Scanning electron microscope analysis（SEM）：It is scanned using cold field emission Electron microscope analyzes the pattern of film surface and section, sample need to be quenched in liquid nitrogen when shooting section Electronic Speculum disconnected, with Clap to obtain complete clearly cross-section diagram.Fig. 7 is cortex, bottom surface and the cross-section diagram of pure pvdf membrane and hybrid films, can be with from cortex figure Find out, PVDF/P0 film surfaces contain a large amount of defective holes, and there are many quantity of macropore；The defects of PVDF/P1 films, hole significantly reduced, hole Size than more uniform,；The big hole number on PVDF/P4 and PVDF/P7 surfaces gradually increases, and be added to modifier particles Hybrid films, defect hole number are respectively less than pure film.From graph of pore diameter distribution as can be seen that PVDF/P0 size distribution compared with Extensively, average pore size proportion only has 35 %, and the hybrid films average pore size proportion after modifying agent has been added to be substantially improved, PVDF/P1 mean pore size percentages are about 76%.This explainable modifier particles can be with PVDF matrix mixed phase well Hold, the macromolecular chain on PGS-g-PDMAEMA particles can mutually tangle with PVDF strands, therefore mix what ultrafiltration membrane was formed Big hole count is less than pure film.Can be seen that from film ground plan with the increase of PGS-g-PDMAEMA particle weights, the nucleus of film by Decrescence few, quantity gradually increases, and the gap between nucleus also gradually increases.This is because the increase of modifier particles makes precipitation fast Degree is accelerated, and then accelerates the process of PVDF crystallizations.As can be seen that the section of film is in unsymmetric structure from cross-section diagram, by Cortex, finger-like pore, spongy hole composition.Its finger-like hole length of the hybrid films of modifying agent is added to less than pure film, skin thickness is small In pure film.This is because the addition of modifying agent makes the viscosity of casting solution become larger, during inversion of phases, between solvent and non-solvent Kinetic exchange process significantly slow down, therefore postpone phase separation the phenomenon that it is more obvious, be unfavorable for the generation of finger-like pore.Separately Outside, crystallizing the quickening of process can cause the split-phase speed of film surface to be accelerated, and the hymeniderm layer thickness of generation reduces.In gel process In, casting solution film-forming, organic phase contraction causes to generate interfacial stress between organic and inorganic phase, can increase the porosity of film, Appropriate pore structure is formed, therefore the increase of PGS-g-PDMAEMA particles also functions to pore effect to a certain extent, makes film Porosity is improved.
（3）Opening size test：Liquid-liquid displacement method is taken to analyze the aperture of film and its distribution using membrane aperture analyzer, Experiment is using isobutyl alcohol-water system, using saturation water phase as mobile phase.Need to cut the diaphragm of certain diameter before test, in saturation It is tested again after being impregnated one day in alcohol phase solution, each film at least tests 5 samples, is averaged.
（4）Porosity test：Membrane porosity is analyzed using wet-dry change.A certain size wet film of clip, uses filter paper The quick water for wiping film surface attachment away, obtains wet film quality after weighing, wet film is placed at least two days in air, until wet film is complete It is complete to spontaneously dry, dry film quality is obtained after weighing.To reduce error, each film at least tests 9 samples, and calculating is averaged.Profit Porosity calculating is carried out with following formula.
εRefer to the porosity of film（%）,m 1 Withm 2 The quality of wet film and dry film is respectively referred to,ρ w Density for pure water（20 DEG C, 1 g/cm3）；ρ m Density for film（Proportion and respective density depending on PVDF and PGS, whereinρ PVDF = 1.79 g/cm3；ρ PGS = 2.05 g/cm3）.
Corresponding totality film thickness, skin thickness, average pore size, porosity data are as shown in the table：
Fig. 8 is the pore-size distribution of different films.
（5）The thermal stability of film：Pass through thermogravimetric analysis（TG）, thermal stability analysis is carried out to film using thermogravimetric analyzer, Using nitrogen as protective atmosphere, heating rate is 10 DEG C/min, and temperature range is 25 DEG C ~ 1000 DEG C.
Fig. 9 is the thermogravimetric curve figure of pure PVDF ultrafiltration membrane and hybrid films.It can be seen from the figure that the residue of PVDF/P0 contains Amount percentage is minimum, and the remaining percentage composition of PVDF/P1 is maximum, and the remaining percentage composition of PVDF/P4 is slightly less than PVDF/ P1.This may be because with the increase of modified dosage, and split-phase speed is accelerated, more PVDF- in casting solution phase process G-PDMAEMA particles are carried over membrane pore structure with the outflow of solvent, form large hole.Residual mass is mainly derived from PVDF materials, so residual mass difference and property-modifying additive PVDF-g-PDMAEMA between PVDF/P0 and other composite membranes The content of particle is related.
（6）Film mechanical strength test：Mechanical strength test includes elongation and tensile strength is tested, and dry film is cut into centainly Film both ends are respectively fixed on puller system by the rectangle of size, are at nature straight condition.Sample actual test size For the mm of 10 mm × 50, puller system tensile speed is set as 10 mm/min.Elongation and tensile strength meter are carried out using the following formula It calculates.Each film at least prepares 5 samples and is tested, and as a result takes its average value.
WhereinσtFor tensile strength (MPa)；FFor peak load (N)；bFor membrane sample width (mm)；dFor membrane sample sample thickness It spends (mm)（It is obtained by section Electronic Speculum measurement）；ΔcLength (mm) of moment when being stretched is broken in drawing process for sample；L 0 Initial length (mm) for sample.
Following table is pure pvdf membrane and the mechanical strength test data of hybrid films.
From table it can be found that with the increase of modified dosage, the tensile strength and elongation of film increase, The tensile strength of PVDF/P7 hybrid films is maximum, reaches 1.898 MPa, and the elongation of PVDF/P4 is maximum, is 52.4 %.This may Be because be added to inorganic particulate, and the PDMAEMA strands of attapulgite surface grafting in film forming process with PVDF Strand mutually tangles, therefore the toughness of hybrid films is stronger than pure film, and the tensile strength of film becomes larger, and the addition of inorganic particulate is simultaneously Film can be made to become fragile, so the elongation of hybrid films can decrease down to a certain degree.
（7）The contact angle of film：Contact angle is the important measurement for weighing wetness degree, and contact angle is whether measurement substance is hydrophilic Major criterion.From General Principle, water can form a θ angle, as contact angle in film surface.It is carried out using sessile drop method Film surface static contact angle is tested, and dynamic contact angle test is carried out with DropMeter A-100p, and drop size is 2 μ L, is moved The state contact angle testing time is 200 s, and to reduce error, each film at least takes 5 different locations to be tested.To pure PVDF and Hybrid films carry out contact angle test, and as shown in Figure 10, the contact angle of PVDF/P0 is 91.46 °, adds in PGS-g-PDMAEMA After son, the contact angle of hybrid films is declined, and the hydrophily of film is improved.The contact angle of wherein PVDF/P1 films is minimum, is 75.81 ° hydrophily is best.Further film into Mobile state is tested, studies its permeance property, Figure 11 is to measure dynamic contact angle Sectional drawing in the process can obtain corresponding contact angular data by software analysis.In figure 12 it can be seen that it is doped with PGS-g- The contact angle decrease speed of the mixing ultrafiltration membrane of PDMAEMA particles is faster than pure film, illustrates that permeability of the membrane can be improved.200 After s, the contact angle of PVDF/P1 films is 20 ° about lower than PVDF/P0, illustrates that modified film hydrophily obtains larger carry again It is high.This is because during inversion of phases, due to the inductive effect of water, the phenomenon that the oriented film surface isolation of hydrophilic chain and enrichment, The dimethylamino hydrophilic radical that PGS-g-PDMAEMA possesses partly is enriched in film surface during inversion of phases, so as to make film Hydrophily is enhanced.
（8）Pure water flux is tested：Using dead-end filtration mode, carried out with the cup type ultrafiltration cup of 8400 types of Millipore pure Water flux is tested.At 25 DEG C, with 0.2 MPa pressure then 30 min of film precompressed is carried out under 0.1 MPa pressure first Test, measures penetrating fluid volume per minute and calculates its pure water flux.Pure water flux calculation formula is as follows：
WhereinJRepresent pure water flux (Lm-2·h-1)；VRepresent penetrating fluid volume (L)；ARepresent effective membrane area (m2)；tTable Show filtration time (h).
Figure 13 is the pure water flux of hybrid films under pure pvdf membrane and Different adding amount, it can be seen from the figure that PVDF/P0 films Pure water flux it is minimum about 123.28 L/ (m2H), with the addition of modifying agent PGS-g-PDMAEMA particles, pure water flux by Gradually rise, the pure water flux of PVDF/P7 films is maximum, about 271.23 L/ (m2H), it is twice of PVDF/P0 films.With reference to Electronic Speculum Map analysis, it is smaller that PVDF/P0 film surfaces contain a large amount of defective hole fenestra quantity, and is doped with the film of PGS-g-PDMAEMA particles Aperture ratio is more uniform, and fenestra quantity increases.After adding in PGS-g-PDMAEMA particles, the viscosity of casting solution increases, inversion of phases film forming Mass transfer velocity slows down between solvent and non-solvent in the process, between PVDF and PGS-g-PDMAEMA particles since contraction is different The increase of fenestra and porosity can be caused, so as to improve permeability of the membrane energy.Also, due to the parent of PGS-g-PDMAEMA particles Aqueous, during inversion of phases, the dimethylamino hydrophilic radical part that PGS-g-PDMAEMA possesses is enriched in film surface, so as to make The hydrophily and permeability of film are enhanced.
（9）BSA Static Adsorptions：It is carried out with the BSA solution of the phosphate buffer solution 1 g/L mass concentrations of configuration of pH=7.4 quiet State adsorption experiment.Wet film is cut into the rectangle of the mm sizes of 15 mm × 60, is immersed in phosphate buffer solution and balances film surface Charge takes out after half an hour and is transferred in the plastic test tube equipped with 20 mL BSA solution.By 25 DEG C of plastic test tube sealing merging Shaking bath in wavelength is solution absorbance in testing tube at 278 nm after absorption 5 hours.Film under the conditions of each is at least tested Four samples.Adsorbance is calculated using the following formula.
Wherein,q s Represent static adsorbance (the μ gcm of sample to be tested-2)；C 0 WithC’BSA under original state is represented respectively The concentration (g/L) of solution after the concentration and Static Adsorption of solution；ARepresent the area (m of wet film sample2)。
Figure 14 is pure pvdf membrane and the Static Adsorption of hybrid films.As can be seen from the figure the PVDF for being added to modifying agent is compound The adsorbance of ultrafiltration membrane is respectively less than pure pvdf membrane, this shows that the addition of modifying agent enhances the antifouling property of film.This is mainly Because during Static Adsorption, modified attapulgite PGS-g-PDMAEMA is gradually migrated during inversion of phases to film surface, Hydrophilic layer is formed on film surface layer, therefore water layer as the destruction of hydrophobic BSA solutes needs certain energy, film surface absorption BSA amounts are reduced.The adsorbance of wherein PVDF/P1 is minimum, about 256.06 mgcm-2；The static adsorbance of PVDF/P7 films omits Less than PVDF/P4, this may be since during inversion of phases, PGS-g-PDMAEMA particles are lost in the outflow of solvent, The modifying agent PGS-g-PDMAEMA for moving to film surface is reduced, this is consistent with the thermogravimetric result of film.
（10）Membrane filtration BSA is tested：Experiment uses the cup type ultrafilter of 8400 types of Model of Millipore companies of the U.S.. After wet film is fitted into ultrafilter, with heartily pure water, precompressed half an hour, adjusting pressure to 0.1 MPa are incited somebody to action under 0.2 MPa The BSA solution that feeding liquid changes 100 mL into carries out Ultrafiltration experiment（Mass concentration is 1 g/L, and solvent is the phosphoric acid buffer of pH=7.4 Solution）, penetrating fluid volume is collected in different time, terminates protein filtering after 60 min, penetrating fluid and residue BSA is taken respectively Sample measures absorbance value, determine protein concentration.
Rate and protein retention is calculated by following formula：
WhereinRRepresent rejection (%)；C p Represent the penetrating fluid concentration (g/L) after filtering one hour；C 0 For material liquid initial concentration (g/L)
The amount of BSA that dynamic adsorbance is adsorbed by unit membrane area through every milliliter of penetrating fluid is defined, it can reflect filtering egg Film, also can side reflection cake layer and hole plug situation to the absorption situation of albumen in white solution.Dynamic is calculated using following formula to inhale Attached amount.
Whereinq d Represent dynamic adsorbance (μ gcm-2·mL-1)；C 0 、C p WithC 2 Respectively represent material liquid initial concentration, The concentration of penetrating fluid and residue BSA solution concentrations (g/L)；V、V 1 WithV 2 Initial volume, the penetrating fluid volume of material liquid are represented respectively With surplus solution volume in ultrafiltration cup；ARepresent the area (m of membrane sample2)。
Using pollution index MFI is corrected come further analyzing film pollution situation, it can reflect that film is got dirty in separation process The trend of dye, value is bigger, and the contaminated trend of explanation is bigger.First made according to formula the following formulat/V - VCurve, then Calculate MFI.
AFor membrane area；VFor penetrating fluid volume；ΔpFor transmembrane pressure；R m For the resistance of film in itself；R c For film surface pollution object Drag overall；μFor viscosity of sludge；tFor filtration time.
Film is filtered using BSA as pollutant, permeation flux in experimentation is investigated and changes with time.Such as Figure 15 Shown, all in all, the permeation flux of film is decayed with time change, is finally intended to stablize, 5 min before filtering, flux Decline most fast, during to 20 min, permeation flux attenuation is slow, and last 30 min is the flux stabilized phase.There is it can be seen from the figure that, The permeation flux rate of decay of hybrid films is less than pure PVDF ultrafiltration membrane, and with the increase of modifying agent additive amount, steady seepage Flux gradually increases, and flux decline speed is slow.This is because with the variation of time, film surface meeting absorbed portion BSA, And it blocks fenestra and gradually forms cake layer, and the addition of modified attapulgite PGS-g-PDMAEMA can improve and improve film Hydrophily enhances the antifouling property of film.With the increase of PGS-g-PDMAEMA additive amounts, the aperture of film and porosity also phase The increase answered.Figure 16 is the steady seepage flux of membrane filtration BSA, the PVDF composite hyperfiltration membranes under PVDF/P0 and Different adding amount Rejection be 100 %, twice of the stabilized flux nearly PVDF/P0 films of PVDF/P7 films, ensureing the constant feelings of rejection Water flux is increased under condition.In above filtering, each pvdf membrane is all 100% to the rejection of BSA.
Figure 17 is the BSA dynamic adsorbances of the film surface during BSA is filtered.It can be seen from the figure that pure pvdf membrane Dynamic adsorbance is apparently higher than the mixed-matrix ultrafiltration membrane after addition modified attapulgite, this explanation is in filtering BSA solution processes In, pure pvdf membrane hole and film surface are easier BSA adsorption molecule, and Pore Blocking is accumulated more serious with film surface.This is inhaled with static state Attached trend is similar.
Pollution index analysis is carried out to film using pollution index MFI is corrected, as shown in figure 18, using permeation flux V as horizontal stroke Coordinate pair t/V maps, and the slope in the range of linearity is to correct pollution index, represents that film is contaminated during pollutant is detached Trend size.From the graph, it is apparent that the maximum slope of pure PVDF ultrafiltration membrane, MFI indexes are maximum, and contaminated trend is most Greatly.With the increase of modified attapulgite additive amount, MFI indexes are gradually reduced, the contaminated trend during separating and filtering BSA Be gradually reduced, this further illustrates modified attapulgite addition can reduce ultrafiltration membrane during pollutant is detached by Pollution level.
（11）The comparative experiments of the performance easy to clean of film：The cleaning way of film：The difference for investigating polluted membrane after BSA is filtered is clear Influence of the clean mode to flux recovery, experiment using 8400 filters of ultrafiltration cup Millipore, respectively to the film after pollution into The solution of row pure water, pH=10.35 and pH=4.03 respectively three times, with different pH solution cleaned and be aided with ultrasonic cleaning by cleaning.Every time with 20 Three times, each 10 min, filter rotating speed is set as 600 r/min to mL liquid rinses, and ultrasonic time is 3 min, and intensity is 40 %. Flux recovery rate after cleaning is calculated using the following formula.
FRR Represent flux recovery rate (%);J w1WithJ w2Preceding pure water flux (the Lm with cleaning caudacoria of filtering is represented respectively-2·h-1)。
The easy cleaning performance of film is investigated, is cleaned with pure water, is cleaned with the alkali of pH=10.35 respectively, it is clear with the acid of pH=4.03 It washes, adjust different pH value and is aided with the mode of ultrasound, be 4% modified attapulgite mixed base to pure PVDF ultrafiltration membrane and additive amount Matter ultrafiltration membrane PVDF/P4 is cleaned.As shown in figure 19, flux recovery rate of the PVDF/P4 films after Membrane cleaning under different modes Pure pvdf membrane is all higher than, and adjusts different pH and is aided with the best results that the cleaning way of ultrasound obtains.The result shows that pure film exists It adjusts different pH to clean and be aided with flux recovery rate highest under the mode of ultrasound, reaches 24 %, and PVDF/P4 mixed-matrix ultrafiltration Membrane flux can be restored to 43.19 %, close to twice of pure film.Using the highest cleaning way of flux recovery rate, to pure pvdf membrane It is cleaned with the mixed-matrix ultrafiltration membrane under different modifying agent additive amounts, tests its flux recovery rate, as a result as shown in figure 20. It can be seen from the figure that the flux recovery rate of mixing ultrafiltration membrane is all higher than PVDF/P0, the flux recovery rate of PVDF/P1 is maximum, reaches To 54.17 %, this is because the contact angle of PVDF/P1 is minimum, hydrophily is best, and the roughness of film surface is smaller, therefore Antifouling property is best, this is consistent with the trend of film Dynamic Adsorption.
（12）Membrane pollution resistance is analyzed：Introduce protein solution permeation fluxJp, filtering before with cleaning caudacoria pure water lead to AmountJ w1WithJ w2, gross contamination resistanceR t , reversible membrane fouling resistanceR r With irreversible membrane fouling resistanceR ir , carry out membrane pollution resistance analysis. Filtration protein solution carries out Membrane cleaning later, and the pollution that can be removed in cleaning process is known as reversible membrane fouling, this partial contamination Object is mainly deposited on the organic macromolecule and protein of film surface, and it is remaining be referred to as irreversible membrane fouling, mainly due to Strong hydrophobic effect and adsorb film surface denatured protein and be blocked in the protein of fenestra.
Gross contamination resistanceR t
Reversible membrane fouling resistanceR r
Irreversible membrane fouling resistanceR ir
It can be seen from figure 21 that the composite membrane gross contamination resistance difference under pure film and Different adding amount is little, and pure pvdf membrane Irreversible membrane fouling index occupy ratio maximum, account for about 73.81 %, this explanation during BSA is filtered pure film mainly by can not Inverse pollution effect, flux recovery rate are minimum.The mixed-matrix ultrafiltration membrane of modifying agent PGS-g-PDMAEMA is added to, it can not Inverse pollution index ratio is respectively less than PVDF/P0, is conducive to flux recovery.The irreversible membrane fouling index of wherein PVDF/P1 is minimum, about For 44.17 %, flux recovery rate maximum.

Claims (10)

1. a kind of modified attapulgite, which is characterized in that the surface of the modified attapulgite has such as formula（I）Shown knot Structure：
（I）；
Wherein, n is the arbitrary integer between 1~10000.
2. a kind of attapulgite is modified PVDF ultrafiltration membrane, which is characterized in that claim 1 institute is also mixed in PVDF ultrafiltration membrane The modified attapulgite stated；Weight ratio between the modified attapulgite and PVDF is 1~10:20.
3. a kind of attapulgite is modified the preparation method of PVDF ultrafiltration membrane, which is characterized in that includes the following steps：
The coupling agent of the key containing C=C is grafted on the surface of attapulgite by the 1st step；
2nd step, by methacrylic acid N, the attapulgite of coupling agent grafting that N- dimethylaminoethyls are obtained with the 1st step is gathered Close reaction；
The modified attapulgite that 2nd step obtains is added in into PVDF casting solutions, is prepared by phase conversion method by the 3rd step Ultrafiltration membrane.
4. attapulgite according to claim 3 is modified the preparation method of PVDF ultrafiltration membrane, which is characterized in that described the In 1 step, the coupling agent of the key containing C=C is silane coupling agent MPS；The w/v of attapulgite and the coupling agent of the key containing C=C is 12g：5~15mL, graft reaction carry out under the conditions of organic solvent, and the organic solvent is toluene, reaction temperature 55~70 DEG C, 2~6h of reaction time, product need to washed, drying process after reaction.
5. attapulgite according to claim 3 is modified the preparation method of PVDF ultrafiltration membrane, which is characterized in that described the In 2 steps, the weight ratio of the attapulgite of methacrylic acid N, N- dimethylaminoethyl and coupling agent grafting is 0.5~6：2；Polymerization Reaction temperature is 75~85 DEG C, and the reaction time is 1~5h, and product needs washed, drying process after reaction.
6. attapulgite according to claim 3 is modified the preparation method of PVDF ultrafiltration membrane, which is characterized in that described the In 3 steps, PVDF, organic solvent, pore-foaming agent, modified attapulgite and PVDF, organic solvent, pore-foaming agent are contained in PVDF casting solutions Mass ratio be：0.05~0.42：10~14：1~5：30~60；The organic solvent is triethyl phosphate；The cause Hole agent is PEG；In 3rd step, phase conversion method be by by PVDF casting solutions blade coating in passing through immersion precipitation on tablet Forming film with phase transformation method.
7. the attapulgite described in claim 2 is modified application of the PVDF ultrafiltration membrane in liquid filtering.
8. application according to claim 7, which is characterized in that contain protein in the liquid.
9. application of the modified attapulgite described in claim 1 in polymer film preparation.
10. application according to claim 9, which is characterized in that modified attapulgite is for reducing polymer film to albumen The absorption of matter, reduction pore-size distribution width, improves porosity, improves thermal stability, improves the big hole defect in reduction polymer Tensile strength improves elongation rate of tensile failure, improves hydrophily, improve water flux, improve to during containing protein solution filtration It can not in flux recovery rate or reduction filter process after flux, reduction filter process index of membrane fouling MFI, raising Membrane cleaning Inverse fouling membrane.
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