CN102580551A

CN102580551A - Method for modifying membrane material in membrane bioreactor

Info

Publication number: CN102580551A
Application number: CN2012100634559A
Authority: CN
Inventors: 魏永; 董良飞; 杨乾; 张凤娥; 陈雪丹
Original assignee: Changzhou University
Current assignee: Changzhou University
Priority date: 2012-03-13
Filing date: 2012-03-13
Publication date: 2012-07-18

Abstract

The invention discloses a method for modifying a membrane material in a membrane bioreactor in the field of sewage treatment, which comprises the following steps: preparing membrane liquid by using polyvinylidene fluoride as the membrane material, using polyvinylpyrrolidone as a porogen, using N-Methyl-2-pyrrolidinone as an organic solvent, using sodium hexametaphosphate as a dispersing agent and using deionized water with the temperature of 25 DEG C as coagulating bath, heating the membrane liquid to the temperature of 50 DEG C and carrying out deaeration for 30 minutes under the vacuum condition of minus 50kPa after stirring so as to form uniform cast membrane liquid; uniformly adding nano TiO2 particles into the cast membrane liquid to prepare an organic-inorganic hybrid membrane by a blending method through adopting an L-S phase conversion method, wherein the added nano TiO2 particles account for 3 to 5 percent by weight of the polyvinylidene fluoride; and preparing the organic-inorganic hybrid membrane into a flat membrane or a hollow fiber membrane. The modified membrane shows obvious hydrophilcity, has excellent membrane flux and membrane separation performance and can effectively improve the problem of membrane pollution in the membrane bioreactor.

Description

Membrane material modified method in a kind of membrane bioreactor

Technical field

The present invention relates to a kind of method of technical field of sewage, specifically is to utilize nano-TiO ₂Membrane material in the membrane bioreactor is carried out modification.

Background technology

Membrane bioreactor (MBR) is a kind of novel sewage disposal technology that utilizes traditional membrane separation technique to combine with biologic treating technique, utilizes membrane module to separate and holds back product and organism, thereby make effluent quality good, is beneficial to water reuse in the realization.Membrane bioreactor owing to separated material produces reasons such as absorption or fenestra obstruction on film surface, is prone to cause film to pollute in actual use, cause its energy consumption high, be prone to stop up and the life-span short.At present, prevent that the method that film pollutes to improve membrane flux from having three major types: (1) increases the cleaning of film, comprises waterpower cleaning and Chemical cleaning, makes and recovers membrane flux; (2) increase the preliminary treatment measure, like coagulation, charcoal absorption, methods such as granular active carbon filtration; (3) develop resistant to pollution membrane material, or through means such as physics and chemical methodes membrane material itself is carried out modification and improve its contamination resistance; Wherein when adopting waterpower cleaning and Chemical cleaning, filter course must regularly stop.In addition, the Chemical cleaning result of film can increase cost of water treatment and produce unnecessary discarded object.And the employing coagulation, preliminary treatment measures such as charcoal absorption need corresponding increase cost of investment.

At present; The MBR membrane material all is to adopt this high-molecular organic material of Kynoar (PVDF) basically, and the most outstanding characteristics of PVDF are to have extremely strong hydrophobicity, when being applied to the aspects such as separation of aqueous phase separation systems such as protein medicaments, food and drink and water purification; Being prone to produce absorption pollutes; Make two of membrane flux and rejection mainly separate index and descend, in the service life of having reduced film, increased operating cost.Thereby, in order to reduce pollution, life-saving and raising flux, make it be more suitable for the use in fields such as biochemistry, medicine, beverage, water purification, need carry out modification to pvdf membrane and widen its application.Improve the common method of polymer separation film material property surface-modification method and body modification method are arranged.Surface modification is to reach the modification purpose through introducing hydrophilic radical on the surface of finished film, and its defective is the modified effect that can not keep the long period, modified effect stability, poor durability, and also the coat of modification can have influence on membrane pore structure and film properties; Body modification method is to improve film properties through casting solution is carried out hydrophilicity-imparting treatment, comprises copolymerization and blending and modifying.Modification by copolymerization needs a plurality of steps to carry out, and technical process is complicated, and uncertain factor is a lot, the difficult control of process; Blending and modifying be a kind of on the basis of current material, learn from other's strong points to offset one's weaknesses improve the short-cut method of film properties.With a kind of polymer and other organic matter or inorganic matter blend, can eliminate the weakness on each single polymers component property, the performance of each component of aggregative equilibrium obtains the comparatively desirable membrane material of combination property.

Nano-TiO ₂Be one of the most active inorganic nano material of research at present, have nontoxic, chemical stability good, antiultraviolet, Superhydrophilic, photocatalytic, is easy to advantages such as preparation.Nano-TiO ₂Membrane permeability and antifouling property have been widely used in improving in recent years.Because its chemical stability is good, its Superhydrophilic, and nontoxic, an amount of interpolation can improve the contamination resistance of film.As one Chinese patent application number be 200710173870.9, name is called " method of modifying of membrane material in the membrane bioreactor ", employing be spraying TiO on the surface ₂The liquid modification belongs to the surface-coated method.Though surface-coated method processing procedure is fairly simple; But be merely physisorption between hydrophilic layer and the pvdf membrane; Grafting of adding or applying or block copolymer are prone to break away from from macromolecule surface; The modified effect that can not keep the long period, the stability of modification and poor durability, and also the coat of modification can have influence on membrane pore structure and film properties.

Summary of the invention

The objective of the invention is for the defective that overcomes above-mentioned prior art provides method membrane material modified in a kind of membrane bioreactor, through the inorganic TiO of blend ₂Nano particle changes film surface and internal physical chemical property, improves the antifouling property of film, improves chemical stability, mechanical strength and the heat endurance of membrane material itself.

For realizing above-mentioned purpose; The technical scheme that the present invention adopts is to comprise the steps: that it is that membrane material, polyvinylpyrrolidone are that pore-foaming agent, N-methyl pyrrolidone are that organic solvent, Sodium Meta Hexa Phosphate 62 and 67 P2O5 contents are that the deionized water of dispersant and 25 ℃ is a coagulating bath preparation film forming liquid that Kynoar is adopted in (1); Heating film liquid to 50 ℃; Stir back deaeration 30min under the vacuum of-50kPa, form uniform casting solution; The weight percentage that Kynoar, polyvinylpyrrolidone, N-methyl pyrrolidone account for said casting solution is respectively 20%, 3%, 77%, and the weight percentage that Sodium Meta Hexa Phosphate 62 and 67 P2O5 contents accounts for Kynoar is 1%; (2) adopt the L-S phase inversion, the method through blend in said casting solution is evenly added nano-TiO ₂Particle preparation becomes organic and inorganic heterozygosis film, the nano-TiO of interpolation ₂It is 3～5% that particle accounts for said Kynoar weight percentage; (3) said organic and inorganic heterozygosis film is processed flat sheet membrane or hollow-fibre membrane.

The present invention adopts has following beneficial effect after the technique scheme:

1, through blend inorganic nano TiO ₂The method of particle changes film surface and internal physical chemical property and since the surface distributed of film TiO ₂Nano particle, the membrane change after the modification surface nature of organic film, show obvious TiO ₂Hydrophily, significantly improved hydrophily; Simultaneously because TiO ₂Interfacial stress between nano particle and the polymer has reduced the roughness on film surface.The surface of film is smooth more, and hydrophily is good more, helps improving the antifouling property of film more, has good membrane flux and membrane separating property, can effectively improve the operating membrane pollution problem of membrane bioreactor.

2, can enlarge the membrane material range of choice; Both possessed that hydrophobic material PVDF is high temperature resistant, characteristics such as favorable mechanical performance and chemical stability; The water-wet behavior that possesses second material again, the excellent combination property of film, and simple with respect to membrane material chemical treatment modifying process, efficient is high.

Description of drawings

Fig. 1 be in the embodiment of the invention 1 under AFM the graphics of non-modified membrane;

Fig. 2 be in the embodiment of the invention 1 under AFM the graphics of modified membrane.

The specific embodiment

At first prepare casting solution.To adopt Kynoar (PVDF) be membrane material, polyvinylpyrrolidone (PVP) for pore-foaming agent, N-methyl pyrrolidone (NMP) be that the deionized water of dispersant and 25 ℃ is that film forming liquid is prepared in coagulating bath for organic solvent, Sodium Meta Hexa Phosphate 62 and 67 P2O5 contents; Heating film liquid to 50 ℃; Behind powerful stirring 24h; Deaeration 30min under the vacuum of-50kPa forms uniform casting solution.Keeping indoor environment temperature is 25 ℃, and humidity adopts conventional operation to film or the spinning film forming about 50%.Wherein, The weight percentage that the weight percentage that the weight of Kynoar accounts for casting solution is 20%, the weight of polyvinylpyrrolidone accounts for casting solution is 3%; The weight of N-methyl pyrrolidone accounts for the weight percentage 77% of casting solution, and the weight percentage that the weight of Sodium Meta Hexa Phosphate 62 and 67 P2O5 contents accounts for Kynoar is 1%.

Then, adopt L-S (liquid-solid; Liquid-solid) phase inversion is called the immersion precipitation phase inversion again and prepares organic and inorganic heterozygosis film.In the preparation process, the method through blend in casting solution is evenly added TiO ₂Nano particle, nano-TiO ₂Adopt Degussa P25 level, the TiO of interpolation ₂The weight percentage that the weight of nano particle accounts for Kynoar is 3～5%.

At last, organic and inorganic heterozygosis film is processed flat sheet membrane or hollow-fibre membrane, promptly be used for the PVDF milipore filter of membrane bioreactor.

Embodiment 1

The weight percentage that earlier to adopt the weight percentage that accounts for casting solution is Kynoar 20%, polyvinylpyrrolidone 3%, N-methyl pyrrolidone 77%, account for Kynoar is 1% Sodium Meta Hexa Phosphate 62 and 67 P2O5 contents and 25 ℃ deionized water preparation film forming liquid; Heating film liquid to 50 ℃; Stir behind the 24h deaeration 30min under the vacuum of-50kPa through powerful, form uniform casting solution.Adopt the L-S phase inversion to prepare organic and inorganic heterozygosis film then, prepare in the process in casting solution that evenly to add the weight percentage that accounts for Kynoar through the method for blend be 3% nano-TiO ₂Particle is processed hollow-fibre membrane with organic and inorganic heterozygosis film at last, is used for membrane bioreactor.

Fig. 1 is the graphics of original non-modified membrane under AFM; Fig. 2 is through the graphics of the hollow-fibre membrane that present embodiment is processed (M-4) under AFM; The surface sweeping scope is 2.0um * 2.0um, and the surface roughness parameter of film can obtain through the AFM analysis software.Can find out that by Fig. 1 and Fig. 2 purity PVDF milipore filter (M-0) has higher roughness value than hollow-fibre membrane (M-4), this shows that the modified membrane of processing through present embodiment has more closely knit top layer, more smooth surface.Simultaneously because TiO ₂The existence of hydroxyl, add TiO ₂After the heterozygosis film have hydrophily preferably, membrane flux and antifouling property thereof can be improved in hydrophilic nmature that modified membrane strengthens and smooth surface.

Embodiment 2

Embodiment 2 and embodiment 1 are different is that in casting solution, evenly to add the weight percentage that accounts for Kynoar through the method for blend be 4% nano-TiO ₂Particle.All the other steps are all identical with embodiment 1.

Embodiment 3

Embodiment 3 and embodiment 1 are different is that in casting solution, evenly to add the weight percentage that accounts for Kynoar through the method for blend be 4% nano-TiO ₂Particle is in the end processed flat sheet membrane with organic and inorganic heterozygosis film.All the other steps are all identical with embodiment 1.

Film with the membrane bioreactor of the hollow-fibre membrane of the modification of embodiment 2-3 gained and flat sheet membrane and non-modification; All be placed on and carry out sewage disposal in the membrane bioreactor under the same operating mode; Result is: the hollow-fibre membrane of modification and flat sheet membrane have better hydrophily; Its resistance tocrocking and membrane flux improve, and behind the operation 90d, run duration is spoil disposal not all.Under different film swabbing pressures and different aeration intensities; Survey its membrane flux and resistance of membrane filtration respectively; The result is: the hollow-fibre membrane of modification and the membrane flux of flat sheet membrane are all greater than the membrane flux of the membrane bioreactor of non-modification more than 35%, and resistance of membrane filtration is less than below 1/3 simultaneously.

Claims

1. membrane material modified method in the membrane bioreactor is characterized in that comprising the steps:

(1) adopting Kynoar is that membrane material, polyvinylpyrrolidone are that pore-foaming agent, N-methyl pyrrolidone are that organic solvent, Sodium Meta Hexa Phosphate 62 and 67 P2O5 contents are that the deionized water of dispersant and 25 ℃ is a coagulating bath preparation film forming liquid; Heating film liquid to 50 ℃; Stir back deaeration 30min under the vacuum of-50kPa, form uniform casting solution; The weight percentage that Kynoar, polyvinylpyrrolidone, N-methyl pyrrolidone account for said casting solution is respectively 20%, 3%, 77%, and the weight percentage that Sodium Meta Hexa Phosphate 62 and 67 P2O5 contents accounts for Kynoar is 1%;

(2) adopt the L-S phase inversion, the method through blend in said casting solution is evenly added nano-TiO ₂Particle preparation becomes organic and inorganic heterozygosis film, the nano-TiO of interpolation ₂It is 3～5% that particle accounts for said Kynoar weight percentage;

(3) said organic and inorganic heterozygosis film is processed flat sheet membrane or hollow-fibre membrane.