本文關(guān)鍵詞： 聚偏氟乙烯 超濾涂覆 刻蝕 膜 超疏水　出處：《天津工業(yè)大學(xué)》2017年碩士論文　論文類型：學(xué)位論文

【摘要】：聚偏氟乙烯(PVDF)具有良好的化學(xué)穩(wěn)定性和抗污染性能,被廣泛的應(yīng)用于膜分離過程中。在膜蒸餾過程中,良好的物理化學(xué)性能使PVDF成為理想的材料。但是膜蒸餾過程對材料的疏水性要求極高,PVDF由于其疏水性有限,在膜蒸餾過程的應(yīng)用受到制約。本文結(jié)合刻蝕法和超濾涂覆法對聚偏氟乙烯(PVDF)中空纖維膜表面進(jìn)行疏水化處理,并通過直接接觸膜蒸餾(DCMD)過程探究了膜性能的變化。首先采用不同比例的DMAc和無水乙醇配制刻蝕劑,對PVDF粒子進(jìn)行刻蝕�？涛g目的是使微米級PVDF粒子光滑的表面粗糙化,出現(xiàn)更小尺寸的粗糙結(jié)構(gòu),有助于粒子在膜表面構(gòu)建出類荷花結(jié)構(gòu)。結(jié)果表明在25 ℃下,刻蝕時(shí)間為60min時(shí),最佳刻蝕劑溶解度參數(shù)為25.60(J/cm3)1/2,可得到刻蝕效果最佳的PVDF粒子。用超濾涂覆的方式,使PVDF刻蝕粒子沉積在中空纖維膜外表面形成涂覆層,構(gòu)筑微納米粗糙結(jié)構(gòu),制備超疏水表面。通過調(diào)節(jié)分散液的溶解度參數(shù),使粒子和基膜發(fā)生溶脹,溶脹的粒子與基膜發(fā)生粘接,可提高粒子涂覆層的牢固性。實(shí)驗(yàn)發(fā)現(xiàn)在最佳分散液溶解度參數(shù)為25.87(J/cm3)1/2,在此分散液中進(jìn)行超濾不會使基膜發(fā)生溶解,并且得到的改性膜涂覆層牢固性明顯提高。粒子最佳涂覆量為18 g/m2,改性膜表面接觸角可達(dá)163.8°,達(dá)到超疏水,同時(shí)不會堵塞膜孔。粒子涂覆法使PVDF中空纖維膜外表面出現(xiàn)超疏水粒子涂覆層,通過SEM觀察到膜表面的涂覆層呈現(xiàn)類荷花狀,具有微納米多層次的粗糙結(jié)構(gòu)。在DCMD測試中,SDBS溶液需要先潤濕粒子涂覆層才能與PVDF基膜接觸并使其潤濕。粒子涂覆層增加了 SDBS溶液潤濕PVDF中空纖維膜的路徑,延長了潤濕時(shí)間,間接提供了一定的潤濕深度,延長了膜的抗親水化時(shí)間,同時(shí)使膜的臨界潤濕深度增大。DCMD過程中熱側(cè)料液在中空纖維膜外表面蒸發(fā),蒸汽透過中空纖維膜在冷側(cè)冷凝,因此產(chǎn)生通量。刻蝕粒子在膜表面構(gòu)建出的微納米結(jié)構(gòu)可為DCMD提供更大的蒸發(fā)面積,所以通量更高。改性膜的貫通潤濕時(shí)間由40 min提高到180 min,DCMD純水通量由26.0提高到29.9 kg·m-2·h-1,同時(shí)臨界潤濕深度值由22.5 μm提高到37.5 μm。結(jié)果說明結(jié)合粒子刻蝕和超濾涂覆的方法,顯著提高了疏水膜的抗親水化能力。
[Abstract]:Polyvinylidene fluoride PVDF (PVDF) has good chemical stability and antifouling property. It is widely used in membrane separation process and membrane distillation process. Good physical and chemical properties make PVDF an ideal material, but the hydrophobicity of PVDF is very high in the process of membrane distillation because of its limited hydrophobicity. The application of PVDF in membrane distillation process was restricted. In this paper, the surface of PVDF hollow fiber membrane was treated by hydrophobicity combined with etching method and ultrafiltration coating method. The change of membrane properties was investigated by direct contact membrane distillation. Firstly, different proportion of DMAc and anhydrous ethanol were used to prepare etching agent. Etching of PVDF particles. The purpose of etching is to roughen the smooth surface of micron PVDF particles, resulting in a smaller size of rough structure. The results show that the optimum solubility parameter of the etchant is 25.60 J / cm 3 / 2 at 25 鈩，

本文編號：1475707