纳滤膜对电解质溶液分离特性的理论研究(Ⅰ):单一电解质溶液

电解质溶液在纳滤膜中的截留率对于膜法海水淡化和重金属离子的脱除非常重要.本文假定膜具有狭缝状孔,采用扩展Nernst-Planck方程、Donnan平衡模型和Gouy-Chapman理论来描述电解质溶液中离子在膜孔内的传递现象.使用纯水透过系数、膜孔径及膜表面电势来表征纳滤膜的分离特征,这三个参数可通过Levenberg-Marquardt方法由实验数据关联得到.本文使用该模型计算了两种商用纳滤膜(NF45和SU200)对1-1型(NaCl,KCl,LiCl),2-1型(K2SO4)和2-2型(MgSO4)单一电解质溶液的截留率,并与实验数据进行了比较,两者吻合较好.计算结果表明电解质溶液中离子在纳滤膜孔内传递的主要机理是离子的扩散和电迁移,纳滤膜对电解质溶液中离子的分离效果主要由空间位阻和静电效应决定.该模型在低浓度时对电解质溶液通过纳滤膜的截留率计算结果较准确,但对高浓度电解质溶液则偏差较大.     

纳滤膜对电解质溶液分离特性的理论研究(II): 混合电解质溶液

假定纳滤膜具有狭缝状孔, 使用纯水透过系数、膜孔径及膜表面电势来表征纳滤膜的分离特征, 用流体力学半径和无限稀释扩散系数表征了离子特性. 采用扩展Nernst-Planck方程、Donnan平衡模型和Poisson-Boltzmann理论描述了混合电解质溶液中离子在膜孔内的传递现象, 计算了三种商用纳滤膜(ESNA1-LF, ESNA1和LES90)对同阴离子、同阳离子和含四种离子的混合电解质体系中离子的截留率, 并与实验数据进行了比较. 计算结果表明, 电解质溶液中离子在纳滤膜孔内传递的主要机理是离子的扩散和电迁移, 纳滤膜对混合电解质溶液中离子的分离效果主要由空间位阻和静电效应决定. 该模型在低浓度时对含一价离子的混合电解质溶液通过纳滤膜的截留率计算结果比较准确, 但对高浓度或含高价离子的混合电解质溶液则偏差较大.     

静电位阻模型在纳滤膜跨膜电位解析中的应用

采用静电位阻模型对纳滤膜的跨膜电位进行了理论解析, 考察了溶液体积通量密度、原料液浓度、阴阳离子扩散系数比、膜孔半径和膜体积电荷密度对KCl(1-1型电解质)和MgCl2(2-1型电解质)中的纳滤膜跨膜电位的影响. 研究结果表明, 随着通量密度的增大, KCl和MgCl₂的跨膜电位线性程度增强; 两种电解质的跨膜电位均随着原料液浓度和膜孔半径的增大而下降; 在不同的考察范围内, 阴阳离子扩散系数比对1-1型和2-1型电解质的跨膜电位的影响差别较大; KCl的跨膜电位随着膜体积电荷密度的变化关于零点呈现出对称性, 而MgCl₂的跨膜电位零点则出现在膜体积电荷密度为负的条件下.     

磺化纤维素纳米纤维多孔膜支撑的高通量纳滤膜的制备及脱盐性能

以细菌纤维素为原材料, 先后通过NaIO₄和NaHSO₃氧化还原反应制备了表面部分磺酸化的细菌纤维素(SBC)纳米纤维. 利用SBC纳米纤维多孔膜替代传统的超滤膜作为支撑底膜, 结合界面聚合反应调控制得复合纳滤膜, 并对其纳滤性能进行研究. 结果表明, 制备得到了对Na₂SO₄和MgSO₄具有高截留率(>96%)和超高分离通量(>320 L·m ^-2·h ^-1·MPa ^-1)的新型纳滤膜.     

聚酰胺纳滤膜对黄连中生物碱的截留性能

以盐酸小檗碱为模型分子,考察循环时间、操作压力、料液浓度和离子强度等因素对聚酰胺纳滤膜截留盐酸小檗碱性能的影响。实验表明:聚酰胺纳滤膜对盐酸小檗碱的截留率80min后基本稳定;随着操作压力的增加,膜通量和截留率都增大;随着料液浓度的增加,聚酰胺纳滤膜通量下降,对盐酸小檗碱的截留率先增大后下降;随着溶液中离子强度的增加,膜通量和截留率都减小。在黄连提取液中生物碱含量为0.025g/L、操作压力为0.4MPa条件下,聚酰胺纳滤膜5min可使黄连提取液中生物碱浓缩6.27倍。     

UV辐照接枝制备酚酞基聚芳醚酮纳滤膜——链转移剂的作用

酚酞基聚芳醚酮(PEK-C)超滤膜的表面通过紫外辐照接枝丙烯酸(AA)可以制备对II价盐有很好截留率的亲水性纳滤膜. FTIR-ATR、表面接触角、SEM和AFM的研究结果表明, 在接枝单体溶液中加入异丙醇(i-PrOH)作为链转移剂并不影响AA在PEK-C超滤膜表面的接枝反应. 得到的改性膜同样具有优良的纳滤性能. 与不加i-PrOH的AA改性膜相比, 新合成的膜有较高的滤出液通量, 该膜对盐离子的截留率虽有所降低, 但可以通过增加接枝反应时间和辐照光源的强度来提高. i-PrOH的浓度对膜的分离性能的影响很大, 在低浓度时, 改性膜对离子的截留率会有所下降, 继续提高i-PrOH的浓度, 膜的截留率不再变化而滤出液通量会有成倍的增加, 表明链转移剂的存在可能会提高膜的接枝密度, 增加膜的表面电荷, 使膜对离子的截留率保持不变.     

聚电解质层层自组装纳滤膜*

层层自组装技术能够方便地对膜的微观结构和组成进行调控,已在制备复合型纳滤膜方面取得了迅速的发展。本文综述了近年来用于聚电解质层层自组装纳滤膜的制备方法,种类以及影响因素。介绍了静态层层交替沉积、压力驱动自组装和电场强化自组装等三种制备方法;归纳了均聚型、共聚型和有机/无机杂化型等三类用于层层自组装纳滤膜的聚电解质的特点;讨论了聚电解质的荷电性、电荷密度和电离程度等因素对其自组装膜分离性能的影响。总结了聚电解质自组装纳滤膜在水处理和有机溶剂中物质的分离等方面的应用。同时,对提高聚电解质自组装纳滤膜的组装效率,分离性能和发展方向提出了设想和建议。     

以聚偏氟乙烯为基底的高渗透选择性聚酰胺/酯纳滤膜的制备与表征

以亲水性聚(N-羟乙基丙烯酰胺)(PHEAA)、疏水性聚甲基丙烯酸甲酯(PMMA)为链段的两亲性三嵌段共聚物PHEAA-b-PMMA-b-PHEAA(PHMH)为改性剂,以聚偏氟乙烯(PVDF)为基底膜材料,利用非溶剂诱导相分离法制备了PVDF/PHMH基底.与未改性PVDF基底相比,PVDF/PHMH基底表面孔径变小,孔隙率和亲水性增加;与PVDF基底纳滤膜N0相比,通过界面聚合制备的PVDF/PHMH基底纳滤膜N1表面粗糙度大、亲水性强、截留分子量小,N1纳滤膜对Na₂SO₄的截留率为96.0%,水渗透通量高达304 L·m^-2·h^-1·MPa^-1,优于商业化纳滤膜的渗透选择性.     

用流动电位法表征纳滤膜的结构及性能

利用测量流动电位的方法考察了纳滤膜的表面电学性能对纳滤膜的截留性能的影响.首先,采用不同功能层材料制备了复合纳滤(NF)膜,考察功能层的交联时间、单体结构等对表面电性能的影响,研究纳滤膜对不同无机盐的选择截留性能与表面电性能的关系.通过流动电位法测定纳滤膜的表面电学参数,如流动电位(ΔE)、zeta电位(ζ)和表面电荷密度(σd).实验表明,这些电学参数的变化与功能层交联时间和纳滤膜截留率的变化一致,在交联时间为45 s时,3种电学参数的绝对值均最大,而纳滤膜对无机盐的截留率也最大.复合纳滤膜zeta电位的绝对值(|ζ|)按照Na2SO4>MgSO4>MgCl2变化,同截留率的变化相同.带侧基单体交联后得到的纳滤膜的表面电性能参数的绝对值小于不带侧基单体的.因此,流动电位法可用于研究复合纳滤膜的截留机理和功能层结构.     

紫外辐照接枝制备亲水性荷正电纳滤膜

通过在酚酞基聚芳醚酮超滤膜表面紫外辐照接枝亲水性单体二烯丙基二甲基氯化铵(DADMAC)制备了一种表面荷正电的纳滤膜. ATR-FTIR和表面水接触角的研究结果表明膜表面的接枝率和亲水性随着辐照时间和单体在接枝溶液中的浓度的增加而增加. 荷正电纳滤膜对盐溶液有很好的截留, 对盐溶液中的高价阳离子和低价阳离子的截留率分别为95%和65%. 但当溶液中存在高价负离子时, 膜的截留性能会明显下降. 表明静电效应在荷电纳滤膜的分离过程中起了重要的作用.     

Chemical Solutions to the Current Polycrisis

In the past 15 years, we've experienced an unprecedented series of crises, including financial (2008), health (2020), and most recently the supply chain disruptions and the energy emergency in Europe, caused by the war in Ukraine (2022). On top of that, climate change still poses a serious threat to our lives and our planet. These interconnected challenges create tremendous societal problems and compromise the viability of the chemical industry in an environment of price volatility and high inflation. Thus, the International Union of Pure and Applied Chemistry (IUPAC) has launched a series of actions to tackle this and raise awareness of the role of chemistry in solving our major threats. Since 2019, IUPAC has identified the “Top Ten Emerging Technologies in Chemistry” to connect chemical researchers with industry, bridging the gap between science and innovation, maintaining the current competitiveness of the chemical industry, as well as tackling our most pressing global challenges.     

硅酸钠和硅铝酸钠溶液的研究

本文采用TMS-GC方法研究硅酸钠及硅铝酸钠溶液中硅酸根离子存在状态及其变化,并配合²⁷Al-NMR方法研究铝酸根离子存在状态,从中找出它们的变化规律。     

Solutions in the calcium oxide-ethylene glycol-water system

A comprehensive study of solutions formed in dissolution of calcium oxide in ethylene glycol and in its mixtures with water was carried out. The major form of compounds in the solutions was established. The maximum attainable concentration of Ca(II) in solutions was determined in relation to the temperature and composition of the mixed solvent.     

Solutions,in Particular Dilute Solutions of Nonelectrolytes: A Review

Journal of Solution Chemistry - The liquid state is one of the three principal states of matter and arguably the most important one; and liquid mixtures represent a large research field of profound...     

Studies on the Stabilization of Modified Lyocell Solutions

Additives with functional properties makes the Lyocell process a versatile tool for the creation of new innovative materials beyond the textile sector. Occupying functional groups or active surfaces the additives emphasize the suitability of Lyocell fibers, but simultaneously enhance the complexity of chemical reactions in cellulose/N-methylmorpholine-N-oxide (NMMO) solutions, respectively. Concerning to the concentration acidic ion exchange resins, activated charcoals, carbon black etc. shift the start of decomposition to lower temperatures, decrease the viscosity, enhance the formation of amines as the main degradation products or cause autocatalytic reactions. New routes in stabilization of modified Lyocell solutions applying a polymeric stabilizer system are described. Using calorimetric, UV/VIS, ESR and HPLC analysis the degradation processes and thermal stability of modified Lyocell solutions compared to the unstabilized were studied. Moreover, as kinetic investigations show a distinguished behavior for modified solutions autocatalytic reactions can be suppressed by the stabilizing system. ESR kinetic study of radicals reveals that formation and recombination rates of radical reactions depend on cellulose concentration in Lyocell solutions and additional ingredients.     

聚酰胺-胺型树枝状高分子水溶液的表面活性

树枝状化合物是一类三维的、高度有序的新型高分子.与传统高分子相比,这类化合物在合成时,可以在分子水平上严格控制,设计分子大小、形状、结构和功能基团,产物一般高度对称,单分散性好.因而具有广泛的潜在用途^[1,2].近年来,已引起广大化学工作者的重视.     

二种求算晶体平面间距d_(hkl)的数学方法

用数学方法推导出结构化学晶体学中晶面间距的一般通式,并在此基础上推导出其他晶系的晶面间距(d(hkl))的计算表达式。     

Copper-Selective Electrode in the Analysis of Dye-Containing Solutions

The effect of dye concentrations in solutions on the potential of a copper-selective electrode with a chalcogenide membrane was studied. It was found that the electrode potential depends on the dye concentration in solutions containing no copper ions. Conventional selectivity coefficients of the electrode with respect to dye anions were determined. The selectivity coefficients ambiguously changed with the dye nature and their concentration in solutions. The use of the calibration graph method without taking into account the composition of the test solution gave rise to great errors in the results of determinations.     

Filters for the Preconcentration of Elements from Solutions

The main techniques for the preconcentration of elements on thin-layer filters are considered: sorption on filters with noncovalently immobilized reagents, bonded groups, and mechanically fixed sorbents and the extraction of elements on filters as poorly soluble and polymeric forms previously formed in solution. The matrix of the filters is cellulose, synthetic polymers of the linear and branched structures, synthetic fibers, reversed-phase silica gels, foamed polyurethanes, etc. The variation of the nature of the bonded group or the reagent introduced into the solution, the matrix material, and the technique for the immobilization of groups provides the preconcentration of elements with regard to the peculiarities of test materials and the method for the subsequent determination of elements. Methods for the determination of elements in different samples including preconcentration on filters are considered.