通過優化式非溶劑誘導及快速蒸汽誘導相分離法研究高性能分離膜的綠色製程

Study on the green production of high performance separation membranes by modified NIPS and FVIPS processes

何兆全(Chao-Chuan Ho)

指導教授 ： 鄭廖平

淡江大學/工學院/化學工程與材料工程學系博士班/博士(2021年)

https://doi.org/10.6846/TKU.2021.00631

摘要

本研究用濕式相轉換法由聚醚碸(PES)/聚乙烯吡咯烷酮(PVP)/γ-丁內酯(GBL)/水製備交穿型多孔薄膜，添加水的研究，膜皆非對稱結構，上表面為緊緻皮層，皮層下為雙連續層，孔隙由小而大，接著是巨孔結構; 隨著水的添加，上表面孔洞數量逐漸增加，膜之純水通量提升，結構中巨孔向下延伸至底部，添加水1.5 phr時，巨孔尺寸大幅縮小型態為孔洞互穿雙連續結構，孔隙度約為77~80 %；上表面接觸角不隨水添加而下降接近74~80。拉伸強度隨水添加量，呈先降後升趨勢。膜用BSA過濾時移除率在70~98%。
添加不同分子量PVP(K15及K30)研究，膜皆非對稱結構，K15比例提升，上表面孔洞的數量及尺寸先升後降，內部結構K5P8時胞孔結構出現，K0P13胞孔佔膜大部分區域，各膜孔隙度約為79%;上表面接觸角約為73%，拉伸強度隨K15提升呈先降後升。純水通量隨K15量增高通量先升後降。膜用Blue dextran過濾時移除率在97-99%範圍。
曝氣時間的研究，膜皆非對稱結構，曝氣時間的增加，上表面孔洞數量及尺寸逐漸增加，結構中巨孔呈縮小趨勢，膜孔隙度為77~78%，上表面接觸角在曝氣3/5/8秒時，介於70~74，過度曝氣表面會開出微米孔洞，接觸角為0。膜拉伸強度落在5.1~5.9 N/mm2。純水通量隨著曝氣時間增長呈上升趨勢。膜作Blue dextran過濾時移除率在97~98%範圍。
通過快速蒸汽誘導相分離(FVIPS)製備用於直接接觸式膜蒸餾(DCMD)脫鹽高度多孔聚偏二氟乙烯(PVDF)疏水對稱平板膜。製膜液由PVDF/磷酸三乙酯(TEP)/水及甘油成分組成，研究聚合物溶解溫度、沉澱槽溫度、甘油添加量及曝氣時間的影響。DCMD通過水循環通量和脫鹽實驗評估膜的滲透性和分離效能。不添加甘油時經過15秒的蒸汽誘導，膜的上表面從不曝氣的緻密光滑變為多孔和粗糙，膜橫截面均保持對稱的雙連續結構。更長蒸汽誘導時間的膜表現出更高的孔隙率，接觸角，厚度和純水通量，拉伸強度小幅度下降。孔徑大小與蒸汽誘導時間的增加無關。
添加甘油會減少開孔所需之曝氣時間及平均孔徑減小。孔隙率，接觸角，厚度隨著曝氣時間的增加而增加。拉伸強度相反。
使用去離子水和鹽水在DCMD測試各種製備疏水膜的性能。 3.5％ 鹽水溶液，0.7 L/min循環流量和35 oC的溫差進行操作時，孔徑0.2/0.5/0.6 µm的膜其滲透通量分別為7.87/12.25/14.66 LMH。孔徑0.22和0.45 µm市售膜，通量分別為9.63和10.99 LMH。所有測試膜的脫鹽率均達到約100％。
長時間72小時測試，溫度差為35°C，鹽溶液3.5%，顯示截留率高達99.3％且滲透通量在5小時後達到平穩狀態，表明在進料過程中幾乎沒有潤濕現象。

關鍵字

聚醚碸 ； 聚乙烯吡咯烷酮 ； 多孔型薄膜 ； 濕式相轉換法 ； 雙連續結構 ； 聚偏二氟乙烯膜 ； 膜蒸餾 ； 快速蒸汽誘導相分離

並列摘要

In this study, a wet phase inversion method was employed to prepare a highly porous membrane from PES/polyvinylpyrrolidone(PVP)/gamma-butyrolactone(GBL)/water dope solution. In the addition of water dosage, the results showed that the fabricated membranes had an asymmetric structure, with a dense skin layer on the top surface then a bi-continuous layer with orientations from small to large, followed by a macroporous structure. Pores number and size increased with increasing of water content, resulting pure water flux increased. The macropores in the structure was extended to the bottom. With 1.5 phr of water addition, the size of the macropores is reduced and converted into a bi-continuous structure, the porosity is about 77~80%. Upper surface contact angel close to 74~80 , tensile strength drop then up. On BSA filtration removal rate within the range of 70~98%.
In the effect PVP (K15 and K30) experiments, the results show membrane had an asymmetric structure. As the ratio of K15 increases, the number and size of pore on the top surface first increase and then decrease. The internal structure at K5P8, the cell structure has appeared, at K0P13, the cells occupy most of the film area, the porosity of each membrane is about 79%, contact angle of the top surface is about 73%, tensile strength with increasing K15, which generally decreases first and increase thereafter , pure water flux as the addition of K15 in the dope solution increased, the flux first rose and then decreased. On Blue dextran filtration removal rate within the range of 97-99%.
In the effect exposure time experiments, the results show membranes had an asymmetric structure. With the increase of exposure time, the number and size of pores on the top surface gradually increase. The macropores in the structure was extended to decrease with exposure time, porosity about 77~78%, contact angle of the top surface at 3/5/8 seconds of exposure time is between 70o~74o . Too long exposure time will caused pore size turn to micron size and structure collapses, contact angle close to 0o . The tensile strength falls within 5.1~5.9 N/mm2. The pure water flux increased with increase exposure time. On Blue dextran filtration removal rate within the range of 97~98% .
The fast vapor-induced phase separation (FVIPS), a highly porous polyvinylidene fluoride (PVDF) hydrophobic symmetric flat membrane for direct contact membrane distillation desalination (DCMD) was successfully prepared. Tthe effects of polymer dissolution and water bath temperature, addition of glycerin as an additive and exposure time were explored. The DCMD process was used to evaluate the permeability and wettability of the membrane through water flux and desalination experiments. Without adding glycerin, after 15 seconds of steam induction time, the top surface of the membrane changed from dense to porous and rough, the cross-sections of membranes are symmetrical sponge-like structure. The membrane after longer exposure time showed higher porosity, contact angle, thickness and pure water flux, but the tensile strength dropped. The pore size has no big difference with increase exposure time.
The addition of glycerin reduces the exposure time and also reduces poze size. The porosity, contact angle, thickness increased and tensile strength decreased with exposure time increases.
The fabricated membranes and commercial membranes tested under the DCMD configuration using deionized water and brine. Using 3.5% NaCl, circulation flow of 0.7 L/min and temperature difference of 35 oC for the DCMD process, membranes with pore diameters of 0.2/0.5/0.6 µm, the permeation fluxes for fabricated membranes are 7.87/12.25/14.66 LMH. The commercial membranes with 0.22 and 0.45 um, fluxes were 9.63 and 10.99 LMH, respectively. The salt rejection rate with all membranes reached about 100%.
The 72 hours long run test with 3.5% NaCl, temperature different of 35°C, high rejection rate 99.3% and permeate flux reached a plateau after 5 hours, showed that there was hardly any wetting during the DCMD process, and the membrane performs better in desalination than commercial membranes.

並列關鍵字

Poly(ether sulfone) ； Polyvinylpyrrolidone ； Porous Membrane ； Wet phase inversion method ； Bi-continuous structure ； PVDF membrane ； Membrane distillation ； FVIPS

參考文獻

[1] World Resources Institute. Aqueduct Project, (2013).

[2] M.A. Shannon, P.W. Bohn, M. Elimelech, J.G. Georgiadis, B.J. Marinas, A.M. Mayes, Science and technology for water purification in the coming decades, Nanosci. Technol. a Collect. Rev. from Nat. Journals. (2010) 337–346.

[3] C.A. Quist-Jensen, F. Macedonio, E. Drioli, Membrane technology for water production in agriculture: Desalination and wastewater reuse, Desalination. 364 (2015) 17–32.

[4] WHO, World Health Organization — Water, Fact Sheet 391, (2014).

[5] G. Amy, N. Ghaffour, Z. Li, L. Francis, R.V. Linares, T. Missimer, S. Lattemann, Membrane-based seawater desalination: Present and future prospects, Desalination. 401 (2017) 16–21.