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根据浓差极化模型和非平衡热力学模型,对4种品牌的纳滤膜(NF40膜、NTR7450膜、Desal5膜和G20膜)在醇类和糖类中性溶质体系的透过实验数据进行回归计算,求得膜定数(即膜的反射系数和溶质透过系数),再由这些膜定数结果根据细孔模型估算了4种品牌的纳滤膜的细孔结构参数,这4种膜的细孔半径范围在0.4~0.8nm。结果讨论表明细孔模型适用于纳滤膜的结构评价。 相似文献
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选择纳滤膜NF270对双甘膦和NaCl自配混合溶液进行分离试验研究和理论分析.探讨了pH、操作压力、氯化钠浓度、双甘膦浓度对纳滤膜分离性能的影响.结果表明,由于纳滤膜NF270截留分子量小于双甘膦分子量,孔径筛分效应成为双甘膦截留率的决定性因素,截留率均稳定在97%左右.电荷效应对NaCl截留率与膜通量有着显著的影响,在pH为6.2,压力为0.7 MPa时NaCl截留率达到最低值4.5%,而高浓度氯化钠不利于分离,高浓度双甘膦却有助于二者的分离.结论认为运用NF270在适宜的操作条件下可实现双甘膦和氯化钠的最大分离. 相似文献
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采用NF270纳滤膜进行饮用水中微量邻苯二甲酸二甲酯(DMP)、邻苯二甲酸二乙酯(DEP)、邻苯二甲酸正二丁酯( DnBP)和苯二甲酸异二丁酯(DiBP)等4种邻苯二甲酸酯(PAEs)去除的试验研究,分析了NF270纳滤膜对PAEs的吸附动力学行为,考察了PAEs的辛醇/水分配系数和分子量对其NF270纳滤膜吸附性能和截留特性的影响.结果表明,Freundlich吸附方程能较好地描述NF270纳滤膜对PAEs的动态吸附行为;在饮用水中微量PAEs去除过程中,NF270纳滤膜对DMP、DEP、DnBP和DiBP的截留特性开始表现为膜面吸附作用和膜孔筛分效应,吸附达到平衡后截留机理取决于膜孔的筛分效应,此时DMP、DEP、DnBP、DiBP的截留率分别为44%、68%、92%、93%(0.5 MPa,30℃,PAEs质量浓度为100 μg·L-1),表明NF270纳滤膜能高效截留饮用水中的DnBP、DiBP. 相似文献
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根据浓差极化模型和非平衡热力学模型,对4种纳滤膜(NF40膜、NTR7450膜、Desal5膜和G20膜)在不同浓度(10~500mol/m3)的电解质(NaCl)溶液体系的透过实验数据进行回归计算,求得膜的反射系数和溶质透过系数。根据TeorelMeyerSievers模型从膜的反射系数估算这些纳滤膜的有效电荷密度并对其进行了电解质浓度的经验关联。结果讨论同时证明了TeorelMeyerSievers模型适用于纳滤膜的带电特性评价 相似文献
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选用具有不同特性的2种纳滤膜NF90和NF270,采用错流试验研究了被天然有机质污染前后纳滤膜对水中邻苯二甲酸酯的去除效率和渗透通量。结果表明,NF90对邻苯二甲酸二甲酯(DMP)、邻苯二甲酸二乙酯(DEP)和邻苯二甲酸二丁酯(DBP)具有较高的截留率,分别为87.9%、95.3%和100%,且截留率随着有机物分子量的增大而增大;NF270对DMP、DEP和DBP的截留率分别为32.1%、50.4%和50%,较NF90的截留率低,且对分子量较大、较疏水的DBP未呈现较高的截留率。在进料液中添加海藻酸钠后,2种纳滤膜的渗透通量明显下降;污染后2种纳滤膜对DMP的截留率分别提高了5.9%和2.4%,对DEP的截留率略有下降,对DBP没有显著影响。改变离子强度(10 mmol/L到20 mmol/L)使NF270对DMP、DEP和DBP的截留率分别下降了2.4%、1.5%和1.5%,而NF90对3种邻苯二甲酸酯的截留率没有明显变化。 相似文献
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1 纳滤膜概述及原理
纳滤是在压差推动力作用下,盐及小分子物质透过纳滤膜,而截留大分子物质的一种液液分离方法,又称选择性反渗透。纳滤膜截留分子量范围为200~1000/MWCO,介于超滤和反渗透之间,主要应用于溶液中大分子物质的浓缩、分离和纯化。 相似文献
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浙江省农村饮用水存在安全隐患,以超滤/纳滤膜为核心建立饮用水净化工艺,考察纳滤膜对水质的提升效果.结果表明:纳滤膜对TOC、CODMn和TDS有较好的去除效果,出水CODMn质量浓度均稳定在1 mg/L以下,NF90和NF270的出水TOC质量浓度分别为1.63 mg/L和0.17 mg/L;NF90的出水TDS优于NF270,NF270的平均去除率为55.87%,NF90的平均去除率为96.97%;这两款膜对于不同分子量有机农药去除具有差异性,膜出水微囊藻毒素-LR的去除率都在90%以上,且出水质量浓度符合饮用水的标准(1μg/L).这两款纳滤膜对蛋白类物质有较好的去除效果,NF270对于分子量小于3 kDa有机物的去除存在局限性. 相似文献
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以脱硫废水为处理对象,提出了软化预处理后的纳滤-电渗析深度处理组合工艺。考察了纳滤分盐特性及电渗析浓缩工艺特性。实验结果表明:纳滤膜 NF270 相比于 NF90 膜接触角较小,膜通量更大。同时 NF270 对 SO42-的截留率为 90% 以上,对 Cl-的截留率仅为 4%,可以实现良好的分盐效果。两段式纳滤膜处理进一步降低了杂质离子的干扰,提高了 Cl-的纯度。电压对电渗析浓缩 Cl-的相对浓缩率影响较大,而温度影响相对较小。经 7次浓缩,Cl-浓度从77.6 mmol/L提升至1 201.2 mmol/L,可以满足制次氯酸钠的生产标准(GB 19106-2013)。 相似文献
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The effects of log-normal pore size distributions on the rejection of uncharged solutes and NaCl at hypothetical nanofiltration membranes have been assessed theoretically. The importance of pore radius-dependent properties such as solvent viscosity and dielectric constant is increased by the introduction of a pore size distribution in calculations. However, the effect of porewise variation in viscosity is less apparent when considered at a defined applied pressure rather than at a defined flux, showing a further advantage of basing theoretical analysis of nanofiltration in terms of applied pressure.Truncated pore size distributions gave better agreement than full distributions with experimental rejection data for a Desal-DK nanofiltration membrane. Such truncation is in agreement with the findings of atomic force microscopy (AFM). Analysis of uncharged solute rejection data alone could not give useful information about membrane pore size distribution. Neither could such a distribution be obtained quantitatively directly from AFM images. However, use of the shape of the distribution obtained by AFM in conjunction with experimental rejection data for an uncharged solute allows calculation of corrected distributions. Importantly, incorporation of such a corrected pore size distribution in calculations of NaCl rejection gave better agreement with experimental data, compared to calculations assuming uniform pores, at high pressure, the region of industrial interest. 相似文献
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W. J. Frederick JR. K. P. Wilson M. L. Laver S. A. Sinquefield 《Chemical Engineering Communications》1988,68(1):197-211
Solute rejection in the ultrafiltration of solutions containing polydisperse solutes was modeled using a spherical solute/cylindrical capillary model, accounting for steric hindrance and wall drag effects. A power law relationship was used for the solute radius-molecular weight relationship. The three parameters in the nondimensional model are the ratio of mean pore radius/solute radius coefficient, the exponent in the solute radius versus molecular weight relationship, and the standard deviation of the logarithms of the pore diameters. Values of the parameters, obtained by fitting the model to rejection coefficient data for solutions containing dissolved organics from wood, were self-consistent and made physical sense. The model provides a useful tool for evaluating ultrafiltration membranes for specific solute fractionation applications. 相似文献
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Although there is a voluminous literature on the determination of structural parameters (the pore radius, the ratio of membrane
porosity to membrane thickness) of a nanofiltration (NF) membrane and its separation performance (such as the rejection and
the permeation flux) by the simplified Teorell-Meyer-Sievers (TMS) model, little of this research comments on other theories
and the consequences of linking modeling evaluation to technological application. Theories used to predict the separation
performance of an NF membrane usually include: the non-equilibrium thermodynamic model, the pore model, the space charge model,
the TMS model, the electrostatic and steric-hindrance model, and the semiempirical model. In the article, we briefly trace
the origins or the general ideas of the above-mentioned theories. From there, recent researches on the characterization of
membrane structural parameters and electrical properties (such as the surface charge density q
w
) are reviewed. We then turn to research on the separation performance of an NF membrane for single-component solutions of
inorganic electrolytes, neutral organic solutions, and a mixture solution of electrolytes or that of an electrolyte and neutral
organic solute. Afterwards, we outline the applications of NF technology in the processes of product separation and conclude
with a discussion on the role of models in such applications. 相似文献
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《分离科学与技术》2012,47(11):2435-2449
Abstract The removal of 5 specific active pharmaceutical ingredients (API's) with molecular weight of 189, 313, 435, 531, and 721, respectively, from toluene, methylene chloride, and methanol was studied by using solvent resistant nanofiltration. Three membranes of the StarMem series (120, 122, and 228), with cut‐off values of 200, 220, and 280 respectively, were used in the experiments. Although the rejections expected from the size difference between solutes and membrane pores are high, the results largely depended on the solvent used. For toluene, rejections were rather small, due to the low molecular weight of the solutes of interest (all API's except for the largest compound). Modelling of the rejection curve showed that the minimum molecular weight of a solute to obtain a rejection of 90% in toluene with the membranes used, is ca. 600. The application in methylene chloride was unsuccessful due to partial dissolution of the membrane top layer; other polymeric membranes such as the Solsep series might be more successful. The rejections in methanol were sufficiently high (>90%) to allow implementation: the rejection can be significantly increased by using a module design with double membrane passage and recirculation of the retentate, as was calculated from mass balances. A comparison of a (single pass) nanofiltration system with a throughput distillation unit, currently in use, showed that the energy consumption is 200 times lower in the nanofiltration system. 相似文献
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磺化聚醚砜纳滤膜性能研究 总被引:15,自引:4,他引:11
本文主要研究了磺化聚醚砜 (SPES)复合纳滤膜的性能。详细讨论了纳滤膜对不同溶质的分离特性 ;探讨了无机盐浓度 ,操作压力 ,溶液 p H值及磺化聚醚砜的离子交换容量(IEC)与膜性能的关系 ;并对纳滤膜的电性能进行了初步研究。研究结果表明 ,磺化聚醚砜复合纳滤膜为一荷负电性纳滤膜 ,对无机盐有较好的选择分离性能。磺化聚醚砜的离子交换容量 ,无机盐浓度以及操作压力对膜性能影响较大 ,且对于两性溶质 ,膜的脱除性能与溶液 p H值有关 相似文献