本文選題：膜蒸餾 + 表面修飾　； 參考：《哈爾濱工業(yè)大學(xué)》2017年碩士論文

【摘要】：膜蒸餾(MD)作為一種熱驅(qū)動(dòng)的新型膜分離技術(shù),在海水淡化、廢水處理和濃縮減排等方面都有著廣泛的應(yīng)用前景,但是傳統(tǒng)的膜蒸餾用膜,如聚偏氟乙烯(PVDF)、聚四氟乙烯(PTFE)和聚丙烯(PP)等,都存在膜通量較低、疏水效果差、膜孔容易被堵塞和膜表面容易被潤(rùn)濕等問(wèn)題。因此,開(kāi)發(fā)出一種膜通量大、疏水性能好、鹽分截留率高且運(yùn)行穩(wěn)定的膜蒸餾用膜,對(duì)膜蒸餾工業(yè)化起著極為重要的推進(jìn)作用。本論文以雙重仿生超疏水化的改性方法為核心,結(jié)合靜電紡絲制膜技術(shù),制備出超疏水聚酰亞胺納米纖維膜作為膜蒸餾用膜,應(yīng)用于直接接觸式膜蒸餾(DCMD)實(shí)驗(yàn),研究不同實(shí)驗(yàn)條件下膜蒸餾效能,并對(duì)改性后聚酰亞胺(PI)纖維膜進(jìn)行應(yīng)用潛能分析。膜蒸餾用膜的微孔結(jié)構(gòu)和疏水性能決定了膜通量和鹽分截留率的大小,目前傳統(tǒng)用膜存在孔隙率低、孔道曲折等缺陷,因此考慮使用靜電紡絲技術(shù)來(lái)制備纖維直徑小、孔隙率高、比表面積大且纖維交聯(lián)互通的基膜;另外,對(duì)于基膜的疏水改性是延緩蒸餾過(guò)程中發(fā)生膜潤(rùn)濕的有效措施之一,目前獲得疏水膜結(jié)構(gòu)的方法有原位方法和后處理法,本文采用的是在基膜上進(jìn)行后處理,首先利用多巴胺(DA)與聚乙烯亞胺(PEI)在水中能夠發(fā)生交聯(lián)反應(yīng),形成一層仿生物膠的帶電層(C-PDA/PEI),在不破壞PI纖維膜表面的同時(shí)構(gòu)建了正電荷粘性層;然后將帶有負(fù)電的二氧化硅納米顆粒(Si O2 NPs)通過(guò)靜電吸附組裝到納米纖維表面,重新構(gòu)造膜表面結(jié)構(gòu),加大了纖維表面的粗糙度;最后通過(guò)氟化來(lái)降低纖維膜的表面能,形成仿荷葉表面的超疏水聚酰亞胺多孔纖維膜(152°)。將改性后的PI膜進(jìn)行了膜蒸餾測(cè)試,與改性各階段的PI膜和不同孔徑的PTFE膜進(jìn)行了對(duì)比,可以看出改性后的PI膜不但在穩(wěn)定性上占據(jù)優(yōu)勢(shì),而且膜通量和鹽分截留率也比相同孔徑PTFE膜高;為了測(cè)試膜的抗污染性能,分別將改性后的PI膜應(yīng)用于處理含有表面活性劑(SDBS)、腐殖酸(HA)、甲基藍(lán)染料作為有機(jī)污染物代表的Na Cl鹽水中,記錄實(shí)驗(yàn)過(guò)程中膜通量和電導(dǎo)率隨時(shí)間的變化情況,證實(shí)了改性后的PI膜具備良好的耐污染性能。接著將改性后的PI膜進(jìn)行反滲透(RO)濃水的濃縮減量實(shí)驗(yàn),發(fā)現(xiàn)在進(jìn)料液的體積濃縮到原來(lái)的1/4后,還能保持較高的膜通量的鹽分截留率,說(shuō)明改性后的PI膜能夠在進(jìn)料液濃度很高的情況下保證一定的抗污染和自潔性能;最后將改性后的PI膜進(jìn)行了模擬海水淡化的膜蒸餾實(shí)驗(yàn),對(duì)膜蒸餾海水淡化工藝進(jìn)行技術(shù)評(píng)價(jià)和經(jīng)濟(jì)分析,為膜蒸餾工藝在海水淡化中的用膜選擇提供了另一種可能。
[Abstract]:As a new heat-driven membrane separation technology, membrane distillation (MD) has a wide application prospect in seawater desalination, wastewater treatment and concentration reduction, but traditional membrane for membrane distillation. For example, PVDF (polyvinylidene fluoride), PTFE (tetrafluoroethylene) and PP) all have some problems, such as low membrane flux, poor hydrophobic effect, easy clogging of membrane pore and easy wetting of membrane surface. Therefore, a kind of membrane for membrane distillation with high flux, good hydrophobicity, high salt rejection and stable operation plays an extremely important role in promoting the industrialization of membrane distillation. In this paper, superhydrophobic polyimide nanofiber membrane was prepared by using double bionic superhydrophobic modification method and electrospinning technology to prepare superhydrophobic polyimide nanofiber membrane for membrane distillation, and was applied to direct contact membrane distillation (DCMD) experiment. The effectiveness of membrane distillation under different experimental conditions was studied, and the potential application of modified polyimide (Pi) fiber membrane was analyzed. The micropore structure and hydrophobicity of membrane for membrane distillation determine the membrane flux and salt rejection. At present, the traditional membrane has some defects, such as low porosity and winding pore channel, so it is considered to use electrostatic spinning technology to prepare fiber with small diameter. In addition, the hydrophobic modification of the base membrane is one of the effective measures to delay the membrane wetting in the distillation process. At present, the methods of obtaining the hydrophobic membrane structure are in situ method and post-treatment method. In this paper, a post-treatment was carried out on the base film. Firstly, the dopamine (DA) and polyimide (PEI) could be crosslinked in water. A charged layer of biofilm, C-PDA-p-PEI, was formed, and a positively charged viscous layer was constructed without destroying the surface of the Pi fiber film, and then the negatively charged silica nanoparticles, Sio _ 2, NPs) were assembled on the surface of the nanofibers by electrostatic adsorption. The surface structure of the membrane was reconstructed, and the roughness of the fiber surface was increased. Finally, the surface energy of the fiber membrane was reduced by fluorination, and the superhydrophobic polyimide porous fiber membrane was formed on the surface of lotus leaf. The modified Pi membrane was tested by membrane distillation and compared with the Pi membrane and the PTFE membrane with different pore sizes. It can be seen that the modified Pi membrane not only occupies the advantage in stability. Moreover, the membrane flux and salt retention rate are also higher than those of PTFE membrane with the same pore size; in order to test the anti-fouling performance of the membrane, The modified Pi membrane was used to treat NaCl brine containing surfactant, humic acid, methyl blue dyes as organic pollutants, respectively. The flux and conductivity of the membrane were recorded during the experiment. It was proved that the modified Pi membrane had good resistance to pollution. Then the modified Pi membrane was concentrated and reduced by reverse osmosis (RO) concentrated water. It was found that after the volume of the feed solution was concentrated to the original 1 / 4, the salt retention rate of the membrane flux could be maintained. The results show that the modified Pi membrane can guarantee a certain anti-pollution and self-cleaning performance when the feed concentration is very high. Finally, the modified Pi membrane is used to simulate seawater desalination by membrane distillation. The technical evaluation and economic analysis of membrane distillation seawater desalination process provide another possibility for membrane selection of membrane distillation process in seawater desalination.
【學(xué)位授予單位】：哈爾濱工業(yè)大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2017
【分類號(hào)】：TQ051.893

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