本文選題：平板超濾膜　切入點：聚偏氟乙烯　出處：《東北林業(yè)大學(xué)》2015年碩士論文　論文類型：學(xué)位論文

【摘要】：膜技術(shù)是21世紀(jì)最受關(guān)注的研究領(lǐng)域之一,應(yīng)用于環(huán)保、電子、能源和生物等眾多領(lǐng)域。隨著水資源問題的日益嚴(yán)峻,應(yīng)用于水處理領(lǐng)域的膜技術(shù)吸引了眾多研究者的目光。限制膜技術(shù)發(fā)展的一個最重要因素是膜污染,平板超濾膜相比其他超濾膜能更好的抗污染,機械強度更好,維護清洗也非常簡單,因此,平板膜可以長時間穩(wěn)定的運行。聚偏氟乙烯(PVDF)因為其優(yōu)異的特性,非常適合作為制備平板膜的材料。平板膜往往應(yīng)用在大型水處理設(shè)備中,這就需要提高平板膜的透過性能,本研究以二甲基乙酰胺為溶劑,通過非溶劑致相轉(zhuǎn)化法制備PVDF平板膜,在鑄膜液中加入不同的添加劑,對膜孔的孔徑和分布進行控制,并對聚合物質(zhì)量分?jǐn)?shù)、不同溶劑、添加劑組分和質(zhì)量分?jǐn)?shù)等因素對膜通過性能的影響進行研究。結(jié)果表明,鑄膜液中聚合物質(zhì)量分?jǐn)?shù)越低,水通量越大,當(dāng)PVDF質(zhì)量分?jǐn)?shù)為16%時,在15kPa壓力下,膜通量可達92.7L.m-2.h。高分子量親水性添加劑PVP的致孔能力很強,當(dāng)其質(zhì)量分?jǐn)?shù)為5%時,膜通量達到152.1L·m-2·h,而未添加PVP的原始膜通量只有69.7L.m-2.h,應(yīng)該將其質(zhì)量分?jǐn)?shù)控制在2%以下,含量過高會導(dǎo)致膜孔結(jié)構(gòu)過于疏松,大大降低出水SDI。PEG-400則是低分子量的添加劑,可以與PVP組合,控制膜孔的孔徑及分布。經(jīng)過實驗發(fā)現(xiàn),PVDF質(zhì)量分?jǐn)?shù)為18%的情況下,以2%的PVP作為致孔劑,并配合甘油控制膜表面孔結(jié)構(gòu),可以在保證出水SDI的情況下,將通量提升至97.4L·m-2·h (15kPa壓力下)。膜污染主要作用于膜的表面,所以通過對膜表面進行改性,可以有效的提高膜污染性能。紫外光引發(fā)接枝又是一項簡單溫和,效果穩(wěn)定的表面改性方式。通過共混添加劑提高了膜通過性能之后,本研究通過常見紫外光源照射,以高鈰離子為引發(fā)劑,N,N-亞甲基雙丙烯酰胺和聚乙烯吡咯烷酮為單體,對PVDF進行了表面接枝改性�？疾炝斯庹諘r間、單體濃度、引發(fā)劑濃度對膜抗污染性能的影響。結(jié)果表明,光照時間不宜過長,以3mmin為宜,光照太久會造成膜通量的明顯下降：MBA單體濃度不宜過高,達到0.07 mol·L/1就可以獲得很好的接枝效果；由于高鈰離子引發(fā)劑會發(fā)生水解,引發(fā)劑濃度不能過低,0.04 mol·L-1是最佳濃度。在以上實驗條件下制備的膜片具備優(yōu)秀的抗污染性能,膜片通量恢復(fù)率得到明顯提升,由未改性前的40%,提升到91.3%。膜表面接觸角由77.7°下降到50.0°。通過掃描電鏡和表面全反射紅外表征后發(fā)現(xiàn),經(jīng)過改性后,膜表面更加光滑,引入了具有親水性的酰胺基團。本研究采用的兩步改性方法,簡單高效,能夠很好的穩(wěn)固提升膜通量和抗污染性能,對高性能PVDF膜的大規(guī)模生產(chǎn)有重要參考價值。
[Abstract]:In 21th century, membrane technology is one of the most concerned research fields, which is used in many fields, such as environmental protection, electronics, energy and biology. Membrane technology applied in the field of water treatment has attracted the attention of many researchers. One of the most important factors limiting the development of membrane technology is membrane fouling. Plate ultrafiltration membrane has better anti-fouling and better mechanical strength than other ultrafiltration membranes. Maintenance and cleaning is also very simple, so the flat membrane can run steadily for a long time. PVDF is very suitable for the preparation of flat membrane because of its excellent characteristics. Plate membrane is often used in large water treatment equipment. It is necessary to improve the permeability of the membrane. In this study, PVDF flat membrane was prepared by non-solvent phase inversion method with dimethyl acetamide as solvent. Different additives were added to the casting solution to control the pore size and distribution of the membrane. The effects of polymer mass fraction, different solvents, additive composition and mass fraction on the membrane permeability were studied. The results showed that the lower the polymer mass fraction in the cast membrane solution, the greater the water flux, when the mass fraction of PVDF was 16. Under the pressure of 15kPa, the membrane flux can reach 92.7L 路m-2.h. the high molecular weight hydrophilic additive PVP has very strong pore-forming ability. When the mass fraction is 5, the membrane flux reaches 152.1 L 路m-2 路h, while the original membrane flux without PVP is only 69.7 L 路m-2.h. the mass fraction of PVP should be controlled below 2%. Too much content will lead to the porous membrane structure, greatly reduce the effluent SDI.PEG-400 is a low molecular weight additive, can be combined with PVP to control the pore size and distribution. It is found by experiments that the mass fraction of SDI.PEG-400 is 18%, Using 2% PVP as pore-forming agent and glycerol controlling membrane surface pore structure, the flux can be increased to 97.4L 路m-2 路h ~ (-1) 路h ~ (-1) KPA under the condition of guaranteed effluent SDI. Membrane fouling mainly acts on the surface of the membrane, so the membrane surface is modified. UV-induced grafting is a simple, mild and stable way of surface modification. The surface grafting modification of PVDF was carried out using cerium ion as initiator N- N- methylene bisacrylamide and polyvinylpyrrolidone as monomers. The effects of illumination time, monomer concentration and initiator concentration on the antifouling properties of PVDF were investigated. If the illumination time is not too long, the suitable light time is 3mmin, and the membrane flux will decrease obviously when the illumination time is too long, and the monomer concentration should not be too high, and the grafting effect can be very good when the monomer concentration reaches 0.07 mol 路L / 1, because the cerium ion initiator will be hydrolyzed. The best concentration was 0.04 mol 路L ~ (-1) of initiator. The membrane prepared under the above experimental conditions had excellent anti-pollution performance, and the recovery rate of membrane flux was improved obviously. The contact angle of the film surface decreased from 77.7 擄to 50.0 擄. The surface of the film was more smooth after the modification, which was characterized by scanning electron microscope (SEM) and surface total reflection infrared spectroscopy (FTIR). A hydrophilic amide-group was introduced. The two-step modification method adopted in this study is simple and efficient, and can improve the flux and anti-fouling performance of the membrane. It has important reference value for large-scale production of high-performance PVDF membrane.
【學(xué)位授予單位】：東北林業(yè)大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2015
【分類號】：TQ051.893

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