Multilayer polyelectrolyte films as nanofiltration membranes for separating monovalent and divalent cations

Alternating adsorption of polyanions and polycations on porous supports provides a convenient way to prepare ion-selective nanofiltration membranes. This work examines optimization of ultrathin, multilayer polyelectrolyte films for monovalent/divalent cation separations relevant to water softening. Membranes composed of five bilayers of poly(styrene sulfonate)/poly(allylamine hydrochloride) (PSS/PAH) on porous alumina supports allow a solution flux of 0.85 m³/(m² day) at 4.8 bar, and exhibit 95% rejection of MgCl₂ along with a Na⁺/Mg²⁺ selectivity of 22. Similar results were obtained in Na⁺/Ca²⁺ separations. PSS/poly(diallyl-dimethylammonium chloride) (PDADMAC) films permit higher fluxes than PSS/PAH systems due to the higher swelling of films containing PDADMAC, but the Mg²⁺ rejection by PSS/PDADMAC membranes is less than 45%. However, capping PSS/PDADMAC films with a bilayer of PSS/PAH yields Mg²⁺ rejections and Na⁺/Mg²⁺ selectivities that are typical of pure PSS/PAH membranes. Separation performance can be optimized through control over deposition conditions (pH and supporting electrolyte concentration) and the charge of the outer layer since Donnan exclusion is a major factor in monovalent/divalent cation selectivity. Streaming potential measurements demonstrate that the magnitude of positive surface charge increases with increasing concentrations of Mg²⁺ in solution or when the outer polycation layer is deposited from a solution of high ionic strength.     

十二烷基苯磺酸钠和无机阳离子之间相互作用的密度泛函理论研究

研究阴离子表面活性剂和阳离子之间的相互作用对于理解阴离子表面活性剂的沉淀和溶解现象具有十分重要的理论和实际意义,但关于两者相互作用的相关理论模型鲜有报道。本文采用密度泛函理论(DFT)方法研究了十二烷基苯磺酸根阴离子(DBS^-)与阳离子(Na⁺, Mg²⁺和Ca²⁺)在溶液内及气/液界面处的相互作用。在溶液内,在两种不同溶液环境中(水相和正十二烷)构建DBS^-/阳离子相互作用模型,并对其进行优化。结果表明, DBS^-能够与阳离子以双齿结构稳定结合。DBS^-与阳离子的结合能不仅取决于参与的无机盐离子种类,还与溶剂的性质有关。在气/液界面处, DBS^-与六个水分子相互作用形成的水合物DBS^-·6H₂O最为稳定。但是,无机盐离子的引入会严重破坏DBS^-·6H₂O水合物的水化层结构。本文定义无量纲参量def用来对水化层结构的变化程度进行评价。无机盐离子对DBS^-·6H₂O水化层结构破坏程度的顺序为:Ca²⁺ > Mg²⁺ >Na⁺。电荷分析结果表明水化层在十二烷基苯磺酸钠(SDBS)头基与阳离子的相互作用中起了重要作用。     

Separation selectivity of some ethylenediaminetetraacetic acid and cyclohexane-1,2-diaminetetraacetic acid complexes in column and ion electrokinetic chromatography

The complexes of Mn²⁺, Cd²⁺, Fe³⁺, Pb²⁺, Ni²⁺, Co²⁺, Zn²⁺ and Cu²⁺ with EDTA and cyclohexane-1,2-diaminetetraacetic acid (CDTA) were separated and detected in column and ion electrokinetic chromatography with suppressed conductivity and direct UV detection, respectively. In column ion chromatography (IC) these complexes were separated on an IonPac AS4A anion-exchange column (Dionex, USA). Parameters of carrier electrolyte, which were examined in the ion electrokinetic chromatography (IEKC) mode, include polymer and sulfate concentrations. In IEKC separation selectivity of complexes with poly(diallyldimethylammonium) cation as modifier is similar as for an IonPac AS4A column both for EDTA and CDTA chelates. It was shown that the ion-exchange capacity of the electrokinetic system is more than 100-times lower than the capacity of the IC column for the same peak resolution. In comparison with column main advantages of electrokinetic version are high separation efficiency (220 000–390 000 theoretical plates) and the absence of the analyte interaction with the sorbent matrix.     

盐水溶液中离子与丙氨酸极性基团间的作用对丙氨酸缔合的影响:密度泛函理论与分子动力学模拟

采用密度泛函理论和经典分子动力学模拟研究了盐水溶液中Na⁺、Cu²⁺、Zn²⁺、Cl^-与丙氨酸分子间的相互作用对丙氨酸分子缔合的影响. 密度泛函理论的计算结果显示丙氨酸分子与Na⁺、Cu²⁺、Zn²⁺、Cl^-之间的相互作用可增强其电荷分离. 经典分子动力学模拟结果显示在水溶液中两性离子形式的丙氨酸存在三种缔合结构.盐水溶液中, 阳离子、阴离子与丙氨酸间的相互作用均能一定程度上减弱丙氨酸分子的缔合. 但是阳离子与丙氨酸间的相互作用明显受离子水合作用的影响. 由于Cu²⁺水合作用较强, 虽在气相中Cu²⁺与丙氨酸分子之间相互作用明显比Na⁺强, 但是在水溶液中则情况刚好相反. 在ZnCl₂稀溶液中, Zn²⁺与丙氨酸间的相互作用被其第一水合壳层隔开. 但这种相互作用仍能明显影响丙氨酸分子的缔合, 这与Zn²⁺的水合壳层特征有关. 另外, 离子与丙氨酸之间的相互作用, 不仅会削弱丙氨酸的缔合, 也可导致丙氨酸分子间的缔合结构发生转变. 离子浓度也会影响其与丙氨酸分子间的缔合形式以及丙氨酸的缔合结构.     

MAGNESIUM ION EFFECTS ON CHLOROPLAST PHOTOSYSTEM II FLUORESCENCE AND PHOTOCHEMISTRY

Abstract. –Although there have been several reports that divalent cations, especially Mg²⁺, can significantly affect chloroplast photoprocesses, the molecular mechanism of cation interaction is not well understood. We have investigated the interaction of Mg²⁺with Photosystem II photoprocesses by studying cation effects on chloroplast fluorescence and the Hill reaction. Our results are summarized as follows.
1. Mg²⁺stimulation of background fluorescence (20–30%) saturates at about 0.5 mM Mg²⁺, while Mg²⁺stimulation of variable fluorescence (250%) saturates at about 2.5 mM Mg²⁺.
2. Addition of Mg²⁺to chloroplasts treated with 3-(3,4-dichlorophenyl)-1,1-dimethylurea or dithionite causes a doubling in the amount of total (background + variable) fluorescence.
3. Studies on chloroplasts in the presence of 2,6-dichlorophenolindophenol indicate that Mg²doubles the relative yield of variable fluorescence under light-limiting conditions.
4. Mg²causes large (70–120%) increases in the light-limited rate of the DCIP Hill reaction.
We interpret these results in terms of a model involving two components of chloroplast emission. Our analysis indicates that Mg²⁺increases the effective absorption cross section (size) of the pigment array associated with Photosystem II photochemistry.     

吡啶取代的Lindqvist型多酸的线性和非线性光学性质及阳离子检测功能的理论研究

采用密度泛函理论B3LYP方法计算了吡啶取代的Lindqvist型多酸(POMs)的线性(最大吸收波长, λ_max)和非线性光学(NLO)[超瑞利散射(HRS)的第一超极化率, β_HRS]性质, 探讨了其作为潜在阳离子检测剂的可能性. 金属离子吸附能计算结果表明, 吡啶取代的Lindqvist型多酸配体与金属离子之间均有较强的相互作用, 相互作用强度大小顺序为Ni²⁺>Cu²⁺>Co²⁺>Fe²⁺>Zn²⁺>Mg²⁺>Ca²⁺. 电子光谱和β_HRS计算结果表明, 引入适当的供、 受电子基团对该多酸配体进行修饰可有效调节线性和二阶NLO性质; 同时, 吡啶取代的Lindqvist型多酸对7种金属离子(Cu²⁺, Zn²⁺, Ca²⁺, Mg²⁺, Ni²⁺, Co²⁺, Fe²⁺)表现出了不同的检测行为.     

多组分氧化物Ag－Bi－V－Mo－O催化作用的光电子能谱研究

对于烃类选择氧化反应中复合氧化物的催化作用,普遍认为是Redox机理.迄今对于含有钥、秘复合氧化物催化剂的活性中心和作用机理还存在不同的看法.     

Interaction and aggregation of lipid vesicles (DLVO theory versus modified DLVO theory)

Interaction and aggregation of acidic phospholipid (phosphatidylserine) vesicles were studied with variation of cation species and their concentrations in vesicle suspensions, and of vesicle sizes. Aggregation was determined by measuring turbidity of vesicle suspension. The experimental results of aggregation of vesicles induced by monovalent cations (Na⁺, K⁺, Cs⁺ and TMA⁺) were explained well in terms of the interaction energy of two interacting vesicles using the ordinary Derjaguin–Landau–Verwey–Overbeek (DLVO) theory for both small and large lipid vesicles. However, the experimental results of aggregation of vesicles induced by divalent cations (Ca²⁺, Mg²⁺ and Ba²⁺) were not explained by the ordinary DLVO theory. In order to explain the experimental results of these vesicle aggregation phenomena, it was necessary to modify the theory by including hydration interaction energies which are due to hydrated water at membrane surfaces, and their magnitude and sign depend upon the nature (hydrophobicity) of the membrane surface.     

Electrophilic aromatic substitution regioselectivity for benzene derivatives in terms of cationic localization energies from semiempirical quantum chemical computations

Cationic localization energies (Λ⁺) for the interaction of monosubstituted benzenes with nitronium cation have been computed by the PM3 method. Yields (Y) of nitration isomeric products correlate linearly with the Λ⁺ values. The lnY=a+bΛ⁺ expressions agree both with Arrhenius equation and with linear free energy relationships.     

Studies on the Interaction of Poly(I:C) with Heterocyclic Compounds Containing Iodine

The iodine heterocvclic compound with trivalent-iodine as the cation has a specially remarkable antitumor activityii^[1]. Although 3, 6-bis (dimethylamino)-dibenzopyriodonium formate([I⁺]) inhibits DNA biosynthesis of cancer cells in vitro, the way of [I⁺] depressing DNA synthesis has not been studied. It is significant to investigate the mechanism of the interaction of [I⁺] with nucleic acids.     

Hydrophilic interaction liquid chromatography with indirect ultraviolet detection for the separation and quantification of pyrrolidinium ionic liquid cations

A method of hydrophilic interaction liquid chromatography with indirect ultraviolet detection was developed to determine three pyrrolidinium ionic liquid cations, i.e. N-methyl-N-ethyl pyrrolidinium cation ([MEPy]⁺), N-methyl-N-propyl pyrrolidinium cation ([MPPy]⁺) and N-methyl-N-butyl pyrrolidinium cation ([MBPy]⁺). Chromatographic separation was achieved on a hydrophilic column using imidazolium ionic liquids and organic solvents as the mobile phase. The effects of the background ultraviolet absorption reagents, the imidazolium ionic liquids, detection wavelength, organic solvents, column temperature and the pH value of the mobile phase on the separation and determination of pyrrolidinium cations were investigated and the retention behaviors in hydrophilic interaction chromatography were discussed. The optimized chromatographic conditions were selected. Under the optimal conditions, the detection limits (S/N = 3) for [MEPy]⁺, [MPPy]⁺ and [MBPy]⁺ were 0.59, 0.53 and 0.46 mg/L, respectively. The method has been successfully applied to the determination of the three ionic liquids synthesized in our chemistry laboratory. This research results may improve the analytical method of ionic liquid cations.     

Formation of [C60C5H5] adduct cations and theoretical study of the isomers

We study here the reactions between C₆₀ and planar C₅H₅⁺ cations that lead to the formation of [C₆₀C₅H₅]⁺ adduct cations in the chemical ionization source of the mass spectrometer. The structures, stabilities and charge locations of some possible isomers of [C₆₀C₅H₅]⁺: σ-adduct, π-complex, [1,4]- and [l,2]-addition cations, are studied by AM1 semiempirical molecular orbital calculations. We find that the most stable is the σ-addition cation. Another interesting and stable structure is the π-complex cation which is bonded by the electrostatic interaction at the inter-ring distance of 1.589 Å with the C_5v symmetry. The C₅H₅⁺ cyclopentadienium cation seems to be an “inverted umbrella” sitting on a five-membered ring of the C₆₀ cage.     

季铵阳离子与无机阴离子对铁的缓蚀协同效应

在酸性介质中,季铵阳离子与无机阴离子对铁具有明显的缓蚀协同效应,阴离子的表面活性越强,对协同效应的贡献越大,阳离子的结构对协同效应同样有着明显的影响。本文采用电化学方法仔细地研究了硫酸溶液中四丁基铵阳离子(TBA~+)和十六烷基吡啶阳离子(HDP~+)与SCN~-及I~-对铁的缓蚀协同效应。     

氧化石墨阳离子交换容量测定过程中结构的变化

氧化石墨(GO)结构层上的碳羟基(―C―OH)和边缘羧基(―COOH)在水介质中发生质子化反应解离出的H+具有阳离子可交换性。实验采用甲醛缩合法测量了GO的阳离子交换容量(CEC),用X射线衍射(XRD)、傅里叶变换红外(FTIR)光谱和X射线光电子能谱(XPS)分析测试手段对GO阳离子交换过程中间产物的结构变化进行了分析。结果表明,GO的CEC高达541.48 mmol/100 g。NH_4~+和Ca~(2+)交换后的GO,保持稳定的层状结构,c轴方向层间距分别增大了0.1499和0.2905 nm。NH_4+和Ca~(2+)主要以层间可交换阳离子形式存在于层间域中,并与水分子形成可交换水化阳离子层,部分以[NH_4(H_2O)_6]+和[Ca(H_2O)_6]_2+的形式存在于结构层的边缘附近,共同平衡结构层水解产生的负电荷。     

Tripodal lipophilic ionophores: synthesis, cation binding and transport through liquid membranes

New C₃-symmetric lipophilic tripodal ionophores, Et(CH₂OCH₂COR)₃; R=NMePh (1), R=NEtPh (2), R=piperidyl (3), have been prepared and their binding abilities for alkali and alkaline earth metal cations evaluated by extraction equilibrium and cation transport through bulk liquid membranes. Experiments show that these ionophores have considerable potential for transporting lithium, sodium and calcium ions relative to potassium and magnesium ions. The cation transport rates by ionophores 1 and 2 decrease in the order Li⁺>Na⁺>Ca²⁺>Ba²⁺>K⁺>Mg²⁺, and the selectivities of Li⁺/K⁺, Na⁺/K⁺ and Ca²⁺/Mg²⁺ are 6.47–7.24, 6.05–6.19 and 9.39–16.13, respectively. The extraction selectivity sequences of the ionophores 1 and 2 are in agreement with the descending order of the cation transport rate, and the complexation constants in chloroform phase were estimated.     

RbCl和CsCl水溶液结构的X射线散射及经验势结构精修模拟

采用X射线散射法研究了RbCl和CsCl水溶液的结构,利用基于经验势的结构精修(EPSR)方法获得了溶液中的水合Cl^-、Rb⁺、Cs⁺、离子缔合及本体水的对径向分布函数、配位数分布及空间密度分布(3D结构)等结构信息。在水溶液中,Cl^-具有相对稳定的6水合结构,其水合距离为0.321 nm,外加阳离子对其水合作用的影响不明显。7.3 ± 1.4个水分子与Rb⁺水合,其特征水合距离为0.297 nm,8.4 ± 1.6个水分子与Cs⁺水合其水合距离为0.312 nm。Cs⁺不具有第二水合层,而Rb⁺表现出了更强的水合能力,具有较明显的第二水合层。Cl^-、Rb⁺及Cs⁺常被认为是“结构破坏”型离子。从微观角度来看这种所谓的“结构破坏”主要体现在破坏了本体水分子的第二水合层保持四面体构型的趋势。RbCl和CsCl水溶液中部分存在着Rb-Cl和Cs-Cl直接接触离子对,在1.0 mol·dm^-3的溶液中Rb-Cl及Cs-Cl的特征距离分别为0.324和0.336 nm,溶剂分割离子对的距离则都在0.6 nm左右。相对于Cs⁺,Rb⁺与Cl^-离子之间表现出了更强的缔合能力。     

Structures and energetics of C3H6S isomers: a Gaussian-3 ab initio study

Twenty-two isomers/conformers of C₃H₆S^+√ radical cations have been identified and their heats of formation (ΔH_f) at 0 and 298 K have been calculated using the Gaussian-3 (G3) method. Seven of these isomers are known and their ΔH_f data are available in the literature for comparison. The least energy isomer is found to be the thioacetone radical cation (4⁺) with C_2v symmetry. In contrast, the least energy C₃H₆O^+√ isomer is the 1-propen-2-ol radical cation. The G3 ΔH_f298 of 4⁺ is calculated to be 859.4 kJ mol⁻¹, ca. 38 kJ mol⁻¹ higher than the literature value, ≤821 kJ mol⁻¹. For allyl mercaptan radical cation (7⁺), the G3 ΔH_f298 is calculated to be 927.8 kJ mol⁻¹, also not in good agreement with the experimental estimate, 956 kJ mol⁻¹. Upon examining the experimental data and carrying out further calculations, it is shown that the G3 ΔH_f298 values for 4⁺ and 7⁺ should be more reliable than the compiled values. For the five remaining cations with available experimental thermal data, the agreement between the experimental and G3 results ranges from fair to excellent.

Cation CH₃CHSCH₂^+√ (10⁺) has the least energy among the eleven distonic radical cations identified. Their ΔH_f298 values range from 918 to 1151 kJ mol⁻¹. Nevertheless, only one of them, CH₂=SCH₂CH₂^+√ (12⁺), has been observed. Its G3 ΔH_f298 value is 980.9 kJ mol⁻¹, in fair agreement with the experimental result, 990 kJ mol⁻¹.

A couple of reactions involving C₃H₆S^+√ isomers CH₂=SCH₂CH₂^+√ (12⁺) and trimethylene sulfide radical cation (13⁺) have also been studied with the G3 method and the results are consistent with experimental findings.     

改性氧化石墨烯去除重金属离子的分子动力学模拟

通过硅烷化反应在氧化石墨烯(Graphene oxide, GO) 表面嫁接螯合官能团N-(三甲氧基硅丙烷)乙二胺三酸(EDTA-Si), 得到改性氧化石墨烯(GO-EDTA), 采用分子动力学模拟在分子水平上研究了Pb²⁺在GO-EDTA 表面的动态吸附分布、 构象及动力学性质, 比较了Pb²⁺和单价Na⁺离子在氧化石墨烯上的吸附行为, 模拟了GO-EDTA与Ca²⁺相互作用, 与Pb²⁺的吸附行为进行了对比. 模拟结果表明, Pb²⁺和Na⁺的吸附位点是GO-EDTA 体系中的羧基, 而非氧化石墨烯表面的羟基; Pb²⁺和 Na⁺ 与羧基的吸附构象不同, 前者吸附构象以摩尔比2:1为主, 即两个羧基对一个Pb²⁺离子, 而后者更多倾向于摩尔比1:1的吸附模式, 即一个羧基对一个Na⁺离子; Pb²⁺离子相对于Ca²⁺和Na⁺离子, 形成的COO^--Pb²⁺离子对构象越过的能垒最低, 但是破坏该离子对构象时能垒较高, 表明Pb²⁺离子在氧化石墨烯膜上表现出良好的吸附性.     

Sol-gel Derived Silicate Phosphor Films

Mn²⁺-doped Zn₂SiO₄ and Mg₂Gd₈(SiO₄)₆O₂ phosphor films were deposited on silicon and quartz glass substrates by sol-gel process (dip-coating). The results of XRD and IR showed that the Zn₂SiO₄:Mn films remained amorphous below 700℃ and crystallized completely around 1000℃ From AFM studies, it was observed that the grains with 0.5-0.8 μm size packed closely in Zn₂SiO₄:Mn films, which were uniform and crack free. The luminescence properties of Zn₂SiO₄:Mn films were characterized by absorption, excitation and emission spectra as well as luminescence decay. These properties were, discussed in detail by a comparison with those of Mn²⁺ (and Pb²⁺)-doped Mg₂Gd₈(SiO₄)₆O₂ phosphor films.     

中位-取代的八乙基卟啉的质子化常数研究

本文报导用Aronoff法测定的十五种卟啉的质子化常数(K₃和K₄),并讨论了中位取代基(硝基、氯和甲氧基)对常数的影响。