- 學位論文
聚二甲基矽氧烷/羧甲基纖維素鈉多孔性膜材之製備及其於油水分離之應用
Preparation of Polydimethylsiloxane and Sodium Carboxymethyl Cellulose Porous Membrane for Oil-Water Separation
摘要
因近年來人類對於石化燃料之龐大需求導致石油開採量大幅上升，使得大規模油汙洩漏意外頻傳，海洋環境遭受嚴重破壞，對於快速處理油汙洩漏意外之方式與方便製備使用之材料是目前較為迫切的需求。 本研究主要以聚二甲基矽氧烷(PDMS)、經聚乙二醇-b-聚二甲基矽氧烷(PDMS-b-PEO)修飾後的聚乙二醇-聚二甲基矽氧烷(PEO-PDMS)與羧甲基纖維素鈉(NaCMC)為基材，以類似溶劑澆注-顆粒溶出(Solvent Casting–Particle Leaching)與冷凍乾燥的方式製備疏水與親水多孔性薄膜；PDMS疏水多孔性膜材與PEO-PDMS親水性膜材的製備方式主要是使用PDMS高分子與PDMS-b-PEO嵌段共聚物搭配已知粒徑範圍與重量比例之砂糖顆粒以簡易混合與熱固化方式進行製備，並利用去離子水將混合物內部之砂糖顆粒溶出形成多孔性材料；PDMS-b-PEO共聚物主要作為添加劑，將其與PDMS預聚物與交聯劑混合形成親水的PEO-PDMS材料；修飾後的PEO-PDMS材料其孔洞表面具有PEO親水支鏈，高表面能之PEO支鏈相較於空氣而言較傾向與水接觸，若將水滴置於PEO-PDMS膜材表面則水滴會逐漸滲入膜材內部使整體表面能量下降，而未經修飾之PDMS多孔性膜材其表面之水滴則無法成功滲入膜材內。 實驗中透過油水溶液分離測試比較各條件樣品單位厚度下之分離時間與阻透係數，對於PDMS疏水多孔性膜材而言，分離時間隨著砂糖使用粒徑增加而下降亦隨著砂糖重量比例上升而下降，而各樣品之去離子水阻透係數(Water Rejection Coefficient, Rw(%))則皆可達到99.354 %以上；對於PEO-PDMS親水多孔性膜材而言，分離時間隨著砂糖使用粒徑增加而下降，但隨著砂糖重量比例上升而上升，而各樣品之柴油阻透係數(Oil Rejection Coefficient, Ro(%))則可達到99.990%以上；於膜材重複使用的測試中，PDMS膜材因澎潤後體積變化程度較大而會導致膜材受損，故僅能重複使用3 ~ 5次，而對於PEO-PDMS膜材則能重複使用5次以上，可見其具重複使用之特性。 然而，因PEO-PDMS親水多孔性膜材於完成分離後，測試油品會部分滲入膜材內部，故後續則研究以羧甲基纖維素鈉(NaCMC)作為主要材料並添加BDDE作為交聯劑以冷凍乾燥的方式製備NaCMC親水多孔性膜材；將多孔性膜材置於水中時，無添加交聯劑之樣品於2小時內即分散於水中，而添加交聯劑之樣品於水中一週後亦可保有其完整結構；研究中藉由調整交聯劑的重量比例使膜材內部孔洞產生差異，於油水溶液分離的測試中可見，交聯劑使用量越多則樣品內部孔徑越小導致油水溶液分離時間拉長，在分離效果的表現上，NaCMC親水膜材相較於PEO-PDMS膜材則具有較高的柴油阻透係數，最高可達99.9983 %；在連續分離的測試上，分離初期因膜材上方柴油所產生的壓力隨著分離體積的增加而上升使得分離時間縮短，分離中後期柴油於膜材表面結垢的影響程度逐漸變大，進而抵銷了壓力增加對於分離時間縮短的增益，使得分離時間上升，對於分離效果而言，增加分離體積並不會使柴油阻透係數下降，即便總分離體積達3000毫升其柴油阻透係數依然能維持在99.998%以上。 研究中亦使用TEMPO氧化法製備奈米纖維素，藉由氧化反應將纖維素上的伯醇氧化成羧基，並透過機械降解的方式製備出奈米纖維素；由TEM的結果可見，製備完成的奈米纖維素其寬度範圍約為6 ~ 50 nm，最小可達5.58 nm，而其長度則可達2.6 μm以上。
並列摘要
Due to the demand for petrochemical fuels in recent years, the amount of the petroleum extraction has risen rapidly, which has led to unexpected large-scale oil spill accidents, cause serious damages to the environment and marine life. There is an urgent need for a quick way to deal with the oil spill accidents and materials that are easy to prepare and use. In this study, polydimethylsiloxane(PDMS), PDMS material modified by poly (dimethylsiloxane-b-ethylene oxide) (PDMS-b-PEO) and sodium carboxymethyl cellulose (NaCMC) were used as substrates to prepare hydrophobic and hydrophilic porous membrane through a simple mixing approach, which is similar to solvent casting-particle leaching method, and freeze-dried method. The hydrophobic PDMS and hydrophilic PEO-PDMS porous membrane were mainly fabricated by curing the polymer blend which contains PDMS polymer, PDMS-b-PEO block copolymer and sanding sugar particles of known particle size range and weight ratio and then washing off the sugar particles. The poly(dimethylsiloxane-b-ethylene oxide) (PDMS-b-PEO) was used in this process as an additive to be added into the PDMS prepolymer and curing agent mixture during polymerization and to create a hydrophilic PEO-PDMS. The surface of the PEO-PDMS material has PEO hydrophilic branches, and the PEO branches with high surface energy are more incline to contact with water than air. If water droplets were placed on the surface of the PEO-PDMS membrane, the water droplets will gradually penetrate into the membrane and the overall surface energy will decrease, while the water droplets on the surface of the PDMS porous membrane cannot successfully penetrate into the membrane. In the experiment, we compared the separation time per unit thickness and rejection coefficient of each sample through the oil-water separation test. For hydrophobic PDMS porous membrane, the separation time decreases with the increase in the particle size of the sugar and also with the increase of the weight ratio of the sugar, and the water rejection coefficient can reach more than 99.354 %. For hydrophilic PEO-PDMS porous membrane, the separation time decreases with the increase in the particle size of the sugar, but increases with the weight ratio of the sugar, and the diesel rejection coefficient can reach more than 99.990%. In the test of membrane reuse, PDMS membrane can only be reused 3 to 5 times due to the large volume change after swelling which would cause the damage of the membrane, while for PEO-PDMS membrane it can be reused more than 5 times, which shows that the membrane is reusable. However, because some of the test oil permeated into the PEO-PDMS membrane after oil-water separation, the follow-up study used the sodium carboxymethyl cellulose (NaCMC) as substrate and added BDDE as crosslinking agent to prepare hydrophilic NaCMC porous membrane by freeze-dried method. When we put the porous membrane in water, the sample without crosslinking agent was dispersed in water within 2 hours, and the sample with crosslinking agent was retain its whole structure after 3 days in water. In the experiment, we adjusted the weight ratio of the crosslinking agent to prepare porous membrane with different pore size and compared the separation time and rejection coefficient of each sample through the oil-water separation test. The experiment results showed that the greater the amount of crosslinking agent used, the smaller the pore size of the sample, resulting in a longer separation time of the oil-water solution. In terms of separation performance, NaCMC porous membranes have a higher diesel rejection coefficient than PEO-PDMS membranes, up to 99.9983%. In the continuous separation test, the pressure generated by the diesel above the membrane increases with the increase of the separation volume in the initial stage of test, which shortens the separation time. The effect of the diesel fouling on the membrane gradually increased in the middle and final stage of test, which increase the separation time. For the separation performance, the separation volume did not affect the diesel rejection coefficient. Even if the total separation volume reached 3000 milliliters, the diesel rejection coefficient remains above 99.998%. In the study, TEMPO-mediated oxidation was also used to prepare nanocellulose. The primary alcohol on the bleached never-dried pulp was oxidized to carboxyl group through oxidation reaction, and nanocellulose was prepared by mechanical degradation. From the results of TEM, it can be seen that the width of the prepared nanocellulose is about 6 ~ 50 nm, the smallest can reach 5.58 nm, and the length can reach more than 2.6 μm.