【摘要】：膜蒸餾(membrane distillation,MD)就是把膜應(yīng)用到蒸餾裝置中,利用膜兩側(cè)的溫度差所引起的傳遞組分的蒸汽壓力差為傳質(zhì)驅(qū)動(dòng)力以達(dá)到物質(zhì)分離的目的。膜蒸餾裝置根據(jù)應(yīng)用不同可以分為直接接觸膜蒸餾、真空膜蒸餾、氣掃式膜蒸餾、氣隙式膜蒸餾等,在本文中主要研究的是直接接觸膜蒸餾用PVDF平板膜的制備、改性及分離性能。在PVDF平板膜制備過(guò)程中,分別考察了凝膠浴溫度、停留時(shí)間及添加劑用量對(duì)所制備膜結(jié)構(gòu)和性能的影響。通過(guò)正交實(shí)驗(yàn)可以得出如下結(jié)果:三個(gè)因素對(duì)PVDF平板膜結(jié)構(gòu)和性能的影響順序?yàn)樘砑觿┯昧客Ａ魰r(shí)間凝膠浴溫度。在該實(shí)驗(yàn)條件下,制備PVDF平板膜的最佳方案為:添加劑用量為3%(W/W),停留時(shí)間(5s),凝膠浴溫度為(50℃)。本文使用了兩種不同的方法(即共混改性和表面改性)進(jìn)行改性實(shí)驗(yàn):a、以共混改性制備PVDF平板膜的過(guò)程中,本論文設(shè)置了兩組對(duì)比:Si O2與Ti O2,Al2O3與Ti O2分別共混;甘油/Ti O2,PMMA/Ti O2分別共混改性。在共混改性實(shí)驗(yàn)中通過(guò)控制混合添加劑的比例去考察所制的膜的性能,結(jié)果表明甘油/Ti O2共混后制得的膜效果較好,并且最佳用量為T(mén)i O23%(W/W)、甘油0.4g。b、在表面改性的過(guò)程中,考察了PEG-600的用量、溫度、硬脂酸丙酮溶液的濃度、納米Ti O2粉末顆粒的加入量、在硬脂酸丙酮溶液中的浸泡時(shí)間等因素對(duì)所制得的PVDF平板膜結(jié)構(gòu)和性能的影響。結(jié)果表明在該實(shí)驗(yàn)條件下的最佳改性方案為:在硬脂酸丙酮溶液中浸泡時(shí)間為3h,硬脂酸丙酮溶液的濃度為0.05mol/L,PEG-600的加入量為6ml,納米顆粒Ti O2粉末的加入添加量為0.2g,溫度為50℃。最后通過(guò)超濾杯、掃描電鏡(SEM)、傅里葉紅外光譜分析儀(FTIR)、接觸角測(cè)量?jī)x等儀器對(duì)制備的改性PVDF膜進(jìn)行分析測(cè)試,得到如下結(jié)論:改性后的PVDF平板膜通量高于改性前,截留率比改性前也要高,并且改性后膜表面呈現(xiàn)的是微米結(jié)構(gòu),此結(jié)構(gòu)是導(dǎo)致疏水的原因,從而說(shuō)明改性是可行的。最后把改性后的膜應(yīng)用到直接接觸膜蒸餾裝置中,研究料液溫度、料液濃度和料液流速等因素對(duì)蒸餾過(guò)程的影響。通過(guò)實(shí)驗(yàn)得到膜蒸餾運(yùn)行中最優(yōu)的實(shí)驗(yàn)條件如下:料液溫度為50℃左右最為適宜;考慮到濃差極化對(duì)膜污染的影響,選取料液濃度為15g/L;而料液流速對(duì)膜蒸餾通量的影響比較顯著,因此實(shí)驗(yàn)選取5L/h作為實(shí)驗(yàn)的一個(gè)最優(yōu)選擇。同時(shí)在較優(yōu)的實(shí)驗(yàn)條件(料液溫度50℃、料液濃度15g/L和料液流速5L/h)下對(duì)所制得的膜應(yīng)用脫鹽實(shí)驗(yàn)去分析性能,冷卻水側(cè)冷卻水的電導(dǎo)率值基本沒(méi)有變化,表面改性后PVDF平板膜的脫鹽率可以達(dá)到90%左右。
[Abstract]:Membrane distillation (membrane distillation MD) is the application of membrane to the distillation unit. The steam pressure difference caused by the temperature difference between the two sides of the membrane is used as the driving force for mass transfer to achieve the purpose of material separation. The membrane distillation unit can be divided into direct contact membrane distillation, vacuum membrane distillation, air-sweep membrane distillation, air gap membrane distillation, etc. In this paper, the preparation of PVDF flat membrane for direct contact membrane distillation is studied. Modification and separation properties. The effects of gel bath temperature, residence time and the amount of additives on the structure and properties of PVDF flat membrane were investigated. The results are as follows: the order of influence of three factors on the structure and properties of PVDF flat membrane is the residence time gel bath temperature. Under the experimental conditions, the best method for preparing PVDF flat membrane is as follows: the dosage of additive is 3% (W / W), the residence time (5 s), and the gel bath temperature (50 鈩，

本文編號(hào)：2131186