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聚偏氟乙烯/凹凸棒石复合超滤膜结构调控及其性能
论文作者:童鞋论文网  论文来源:www.txlunwenw.com  发布时间:2019/10/26 13:36:47  

摘要:纳米复合膜已成为膜材料研究领域的热点,不同纳米材料的引入 使得纳米复合膜在机械强度、热稳定性、抗污染能力、渗透性和选择性等方面得到了不同程度的提升。本文将聚偏氟乙烯(PVDF)与纳 米凹凸棒石(PGS)共混制备复合超滤膜,主要研究了凹凸棒石表面化学组成及其棒晶长径比对复合膜形成过程、微结构、渗透分离及抗 污染性能的影响。 凹凸棒石表面氨基、羧基、季铵化及磺酸化修饰改性。利用凹凸 棒石表面丰富的羟基,对其进行氨基(-NH2)、羧基(-COOH)、季 铵化(-CTAB)和磺酸化(-SO3H)改性,调控其表面化学组成。分 别制备出 PGS-NH2、PGS-COOH、PGS-CTAB及 PGS-SO3H 改性凹凸 棒石,其表面的有机接枝率依次为9.36%、19.48%、8.89%和 6.54%, 即 PGS-COOH 的接枝率最高。PGS-NH2的等电点(pH 5.2)高于凹 凸棒石的等电点(pH 4.4), 且在相同 pH 值下,其所带正电荷的量无 明显差异,而 PGS-NH2 所带负电荷的量低于凹凸棒石;相反, PGS-COOH、PGS-CTAB 和 PGS-SO3H 的等电点(pH 依次为 2.2、3.1 和 4.2)均低于凹凸棒石的等电点,且在相同 pH 值下,这三种改性 凹凸棒石所带正电荷的量均低于凹凸棒石,而其所带负电荷的量有所增加;在 pH 7.4 时,PGS-COOH 所带负电荷最多,使其对呈负电性的牛血清白蛋白(BSA)吸附量最低。 凹凸棒石表面化学组成对纳米复合超滤膜结构和性能的影响。分 别将 PGS-NH2、PGS-COOH、PGS-CTAB及 PGS-SO3H 共混到 PVDF 铸膜液中制备了 P4-NH2、P4-COOH、P4-CTAB和 P4-SO3H 纳米复合 超滤膜,考察凹凸棒石表面化学组成对复合膜形成过程、微结构、渗 透分离及抗污染性能的影响。P4-CTAB 膜的膜厚和皮层厚度最小, 其厚度变化情况为P4-NH2>P4-COOH>P4-SO3H>P4-CTAB。P4-CTAB 膜的表面粗糙度最大,P4-SO3H、P4-NH2和P4-COOH 膜的表面粗糙 度依次减小。改性凹凸棒石的添加对膜孔隙率无明显影响,孔隙率均 在 78.50%左右。P4-CTAB 膜的平均孔径最大(26.92 ± 1.87 nm),P4-COOH、P4-SO3H 和P4-NH2膜的平均孔径依次减小,分别为 25.65 ± 3.69 nm、22.89 ± 2.21 nm 和 22.08 ± 2.55 nm。P4-CTAB 膜的亲水性 最好,纯水通量最大,为 269.35 L∙m-2∙h-1,其它三种复合膜的纯水通 量略低。P4-NH2、P4-COOH 和 P4-CTAB 膜对BSA 的截留率都达到 99.7%以上;P4-SO3H 膜过滤 BSA 溶液时稳定通量最高(15.83 L∙m-2∙h-1)。 凹凸棒石长径比对纳米复合超滤膜结构和性能的影响。使用两种 不同棒晶长度的凹凸棒石与 PVDF 共混制备纳米复合超滤,考察凹凸 棒石长径比对复合膜微结构、渗透和分离性能的影响。凹凸棒石长径 比对 PVDF 的晶体结构无明显影响;共混短棒晶凹凸棒石(PGS-S) 制备的纳米复合超滤膜(PVDF/PGS-S)具有较高的孔隙率,较低的 膜厚和皮层厚度;而添加长棒晶凹凸棒石(PGS-L)的纳米复合超滤膜(PVDF/PGS-L)具有更高的热稳定性,更强的表面亲水性,其表 面粗糙度更大,孔隙率较低,机械强度更大。此外,PVDF/PGS-S 膜 的纯水通量、BSA 渗透通量和截留率以及通量恢复率均高于 PVDF/PGS-L 膜,展现出更好的渗透分离和抗污染性能。

Nanocomposite membrane has become a hottopic in the research field of membrane materials. The mechanical strength,thermal stability, anti-fouling property, permeability and selectivity ofnanocomposite membrane can be improved to different degrees with theintroduction of different nano-materials. In this paper, the compositeultrafiltration membrane was prepared by mixing polyvinylifluoride (PVDF) withnano palygorskite (PGS). The surface chemical composition of PGS and the effectof the length-diameter ratio of nanorods on the formation process,microstructure, permeation, separation and anti-fouling performance of thecomposite membrane were studied. Amino, carboxyl, quaternary ammonium andsulfonation modification on the surface of PGS. Aminogroup (-NH2), carboxylgroup (-COOH), quaternization (-CTAB) and sulfonation (-SO3H) were used tomodify the surface of PGS with abundant hydroxyl groups. PGS-NH2, PGS-COOH,PGS-CTAB and PGS-SO3H were prepared respectively, and the organic grafting rateon their surfaces was 9.36%, 19.48%, 8.89% and 6.54%, respectively, indicatingthat the grafting rate of PGS-COOH was the highest. The isoelectric point ofPGS-NH2 (pH 5.19) was higher than that of PGS (pH 4.4), and there was nosignificant difference in the amount of positive charge at the same pH value,while the amount of negative charge of PGS-NH2 was lower than that of PGS. Onthe contrary, the isoelectric points of PGS-COOH, PGS-CTAB, and PGS-SO3H (pH2.2, 3.06, and 4.16 respectively) were all lower than those of PGS. The amountof positive charge of the three modified PGS was lower than that of PGS at thesame pH value, while the amount of negative charge was increased. PGS-COOH hasthe highest negative charge at pH 7.4, leading to the lowest adsorptionquantity of the negative bovine serum albumin (BSA). 

Effect of surface chemical composition ofPGS on the structure and properties of nanocomposite ultrafiltration membrane.P4-NH2, P4-COOH, P4-CTAB and P4-SO3H nanocomposite ultrafiltration membraneswere prepared by blending PGS-NH2, PGS-COOH, PGS-CTAB, and PGS-SO3H into PVDFcasting solution, respectively. The effects of the surface chemical compositionof PGS on the formation process, microstructure, permeability, separation andanti-fouling performance of the composite membrane were investigated. P4-CTABhas the smallest membrane thickness and skin layer thickness, and its variationof the membrane thickness is P4-NH2 > P4-COOH > P4-SO3H > P4-CTAB. Thesurface roughness of P4-CTAB is the highest, and the surface roughness ofP4-SO3H, P4-NH2 and P4-COOH decrease successively. The addition of modified PGShad no significant effect on the porosity of the membrane, which was about78.50%. The average pore size of P4-CTAB was the largest (26.92 ± 1.87 nm), andthe average pore size of P4-COOH, P4-SO3H and P4-NH2 decreased successively,which were 25.65 ± 3.69 nm, 22.89 ± 2.21 nm and 22.08 ± 2.55 nm, respectively.P4-CTAB has the best hydrophilicity and the largest pure water flux (269.35 L∙m-2∙h-1), while the pure water flux of the otherthree composite membranes is slightly lower. The BSA rejections of P4-NH2,P4-COOH and P4-CTAB were all above 99.7%. The stable BSA flux was the highest(15.83 L∙m-2∙h-1) when P4-SO3H was usedto filter BSA solution.  Effect of thelength-diameter ratio of PGS on the structure and properties of nanocompositeultrafiltration membrane. Nanocomposite ultrafiltration membrane was preparedby mixing different length-diameter ratio of PGS with PVDF matrix. The effectsof the length-diameter ratio of PGS on the microstructure, permeability andseparation properties of the composite membrane were investigated. Thelength-diameter ratio of PGS has no obvious effect on the crystal structure ofPVDF. The nanocomposite ultrafiltration membrane (PVDF/PGS-S) prepared byblending short rod-crystal PGS (PGS-S) has higher porosity, lower membranethickness and skin layer thickness.

关键词:聚偏氟乙烯;凹凸棒石;纳米复合膜;结构调控;抗污染性能

polyvinylidenefluoride; palygorskite;nanocomposite membrane; structure regulation; antifouling property

上一篇:3DOM-TiO2的可控合成、表面修饰及光催化性能研究     下一篇:新型硅-氟渗透汽化膜的制备及醇/水分离性能研究
 
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