Mg-Al-NO_3层状双氢氧化物的制备及性能研究

制备了带正电荷的Mg-Al-NO_3层状双氢氧化物（LDH）,并对其组成、形貌、 电性能、离子交换性能等各种性质进行了表征。实验结果表明,所制备的正电纳米 颗粒具有可调控的层间自由空间。该方法为进一步研究聚合物/纳米复合材料提供 了一个合成前驱体的方法。     

多肽净电荷数及等电点的计算

多肽净电荷数及等电点的计算许旭（中国药科大学药物分析教研室，南京，２１０００９）罗国安，林炳承（清华大学化学系）（中国科学院大连化学物理研究所）关键词毛细管区带电泳，多肽，净电荷数，等电点考察多肽在毛细管区带电泳（ＣＺＥ）中的迁移时，必须知道其在分析...     

Ba_xCe_(0.8)Y_(0.2)O_(3-α)固体电解质的氧离子导电性

固体电解质是指固体状态下具有较高电导率的离子导体,根据其传导离子所带电荷分为阳离子导体(如:Na+,Li+,H+等)和阴离子导体(如:F-,Cl-,O2-等)。固体电解质与液体电解质不同之处为:(1)是固态;(2)电荷载流子通常只有一种;(3)由于晶格能较大,通常在较高温度下离子才能迁移。具有实用价值的固体电解质的电导率一般在10-3S·cm-1以上,同时要求其离子迁移数要足够大。至今,已发现和合成了上百种固体电解质材料。在加速研制绿色化学电源、寻找高离子电导率、高化学稳定性、低成本的固体氧化物燃料电池(SOFC)固体电解质的研究中,ABO3钙钛矿型…     

聚电解质层层自组装线性多层膜的电荷分区互补理论建立及膜内聚电解质离子化率

提出了聚电解质层层自组装线性多层膜的电荷分区互补理论,基于该理论建立了表面电荷密度、诱导电荷、聚电解质的吸附量和形态、膜内电荷存在形态之间的半经验数学模型。提出了计算膜内聚苯乙烯磺酸钠（PSSS）与聚烯丙基胺盐酸盐（PAH）的离子化率和电荷诱导效应的方法,讨论了处于最外层和次外层聚电解质的离子化率的不同及其与聚电解质强弱的关系。该方法比红外光谱法和光电子能谱法更简便,可用于研究所有聚电解质的离子化率。     

氢氧化铝镁钠米颗粒的零电荷点及电荷密度研究

探讨了电位滴定(PT)法测定的零电荷点的物理意义, 认为是零净电荷点(ZPNC)。并对零净电荷点pH(pHZPNC), 零可变电荷点pH(pHZPVC), 永久电荷密度(σP), 可变电荷密度(σV)和净电荷密度(σT)之间的关系进行了理论分析。用PT法测定了氢氧化铝镁纳米颗粒的pHZPNC和σP, 探讨了电解质浓度和pH对各电化学性质的影响规律。另外, 还考察了CO3^2^-对PT法测定结果的影响。     

氢氧化铝镁钠米颗粒的零电荷点及电荷密度研究

探讨了电位滴定(PT)法测定的零电荷点的物理意义, 认为是零净电荷点(ZPNC)。并对零净电荷点pH(pHZPNC), 零可变电荷点pH(pHZPVC), 永久电荷密度(σP), 可变电荷密度(σV)和净电荷密度(σT)之间的关系进行了理论分析。用PT法测定了氢氧化铝镁纳米颗粒的pHZPNC和σP, 探讨了电解质浓度和pH对各电化学性质的影响规律。另外, 还考察了CO3^2^-对PT法测定结果的影响。     

全柱成像毛细管等电聚焦电泳分析蛋白质药物电荷异质性

评价了cIEF-WCID检测多肽与蛋白质药物等电点的应用效果。测定标准多肽的等电点,验证了cIEF-WCID具有高的准确度和良好的重复性(相对标准偏差0.50%)。人血红蛋白的4种主要异构体实现了基线分离;甘赖胰岛素的重复测试均只检出单一特征峰(p I 5.95±0.01);比较重组人生长激素原液和成品,等电点特征峰比例差异明显,且成品有新特征峰出现;对比进口及国产贝伐单抗,发现厂家1、3与原研药基本一致,厂家1的主成分迁移规律与原研药高度一致,厂家2的重链C末端K缺失、N末端焦谷氨酸环化或脱酰胺修饰影响了电荷异质性;通过考察尿素浓度、电解质范围和聚焦时间,优化了检测重组人促卵泡素等电点条件:2 mol/L尿素,两性电解质pH 2.5~5.0与pH 3.0~10.0按1∶1混合,聚焦电压1 000 V(1 min)~1 800 V(4 min)~2 200 V(1 min)。cIEF-WCID可快速、准确测定具有电荷异质性的蛋白类药物等电点,分辨率和重复性好,尤其是可以跟踪聚焦过程中样本的迁移特征,特别适合蛋白类药物复杂电荷异质性的检测。     

阳离子聚电解质对油污泥的絮凝作用机理

用高密度电荷阳离子聚电解质处理油污泥［１,２］,依靠其与粘土颗粒间的静电作用压缩污泥中固相颗粒的表面双电层,中和ζ电位,使其颗粒间斥力减小,引力增大,油污泥化学脱稳,致使粘土颗粒聚集絮凝成团块,油颗粒聚集,实现油、水、泥渣的三相分离．１　实验部分１．１　样品制备　现场采集的油污泥中油品含量１９％,固含量８％,体系漏斗粘度３７ｓ,密度１．０９ｇ／ｃｍ３．阳离子聚电解质（ＣＦ）、聚丙烯酰胺－丙烯酸β－羟基丙酯基三甲基氯化铵按文献［２,３］方法制备,平均分子量２．６０×１０６,阳离子电荷度４５％．阴离…     

N-二乙酸基取代四氮杂大环及其镧系配合物的热力学研究

用pH电位滴定法测定了H2L（C－meso－meso－5,12-二苯基-7,14-二甲基-1,4,8,11-四氮杂环十四烷-N,N"-二乙酸）的逐级质子化常数,并进一步计算出配位反应的热焓和熵变．在（40±0．1）℃条件下测定了H2L与调系金属离子（La3+,Nd3+,Pr3+,Sm3+,Eu3+,Gd3+,Dy3+,Yb3+）形成1：1型配合物的稳定常数．用热力学稳定性的观点讨论了大环的尺寸效应和空间位阻等因素对配位稳定性的影响．     

用自组装法制备聚合物纳米复合膜

文章比较了自组装法（ｓｅｌｆ－ａｓｓｅｍｂｌｙ,ＳＡ）与Ｌａｎｇｍｕｉｒ－Ｂｌｏｄｇｅｔｔ技术（ＬＢ）及其它方法在制备聚合物纳米复合膜时的优劣。ＳＡ法由于操作简单、膜的结构稳定性较高,因此较ＬＢ技术等具有更大的实用价值。利用ＳＡ法,可以制备各种有机聚电解质与其带相反电荷的有机聚电解质、粘土化合物及无机纳米颗粒等组成的聚合纳米复合膜。     

Study on electric property at interface of positive sol of magnesium aluminum hydroxide

The isoelectric point (IEP) and zero point of charge (ZPC) of magnesium aluminumhydroxide were studied by electrophoresis method,potentiometric titration method,and elemental analysis.Results showed that the charge of magnesium aluminum hydroxide was composed of variable charge and permanent positive charge.Because of the permanent positive charge,the IEP and ZPC obtained were higher than calculated.The IEP decreased and ZPC increased as X increased.     

The Isoelectric Point and the Points of Zero Charge of Fe-Al-Mg Hydrotalcite-like Compounds

The relation of the isoelectric point (IEP) and the point of zero net charge (PZNC) of the hydrotalcite-like compounds was discussed. It was found that the IEP does not equal to the PZNC and the IEP is higher than the PZNC. The structural positive charges existing in the HTlc,which cause the difference between the IEP and the PZNC. The effects of the structural positive charges of the HTlc on its IEP and PZNC are the same as the specific adsorption of metal cations.     

Synthesis and characterization of goethite and goethite-hematite composite: experimental study and literature survey

Aging of synthetic goethite at 140 degrees C overnight leads to a composite material in which hematite is detectable by M?ssbauer spectroscopy, but X-ray diffraction does not reveal any hematite peaks. The pristine point of zero charge (PZC) of synthetic goethite was found at pH 9.4 as the common intersection point of potentiometric titration curves at different ionic strengths and the isoelectric point (IEP). For the goethite-hematite composite, the common intersection point (pH 9.4), and the IEP (pH 8.8) do not match. The electrokinetic potential of goethite at ionic strengths up to 1 mol dm(-3) was determined. Unlike metal oxides, for which the electrokinetic potential is reversed to positive over the entire pH range at sufficiently high ionic strength, the IEP of goethite is rather insensitive to the ionic strength. A literature survey of published PZC/IEP values of iron oxides and hydroxides indicated that the average PZC/IEP does not depend on the degree of hydration (oxide or hydroxide). Our material showed a higher PZC and IEP than most published results. The present results confirm the allegation that electroacoustic measurements produce a higher IEP than the average IEP obtained by means of classical electrokinetic methods.     

Studies on Zero Point of Charge and Permanent Charge Density of Mg-Fe Hydrotalcite-like Compounds

The theoretical analysis on the zero point of charge (ZPC) and charge density of colloidal particle possessing permanent charges indicates that ZPC determined directly by means of potentiometric titration (PT) should be zero point of net charge (ZPNC) and the permanent charge density (σ_P) can be obtained from the adsorption amount of H⁺ and OH^-(Γ_OH--Γ_H+) at ZPNC. ZPNC does not change with the electrolyte concentration while the zero point of variable charge (ZPVC) changes with the electrolyte concentration. When σ_P is zero, ZPNC equals to ZPVC, and only under this condition is ZPC measured directly by PT equal to ZPVC. The relationship between ZPNC, ZNVC, σ_P, the variable charge density (σ_V)5 or the total net surface charge density (σ_T) with pH or electrolyte concentration is derived.     

Temperature effects on the point of zero charge and isoelectric point of a red soil rich in kaolinite and iron minerals

The effects of temperature (373–1373 K) on the point of zero charge (PZC) and isoelectric point (IEP) of a red soil rich in kaolinite and iron minerals were studied. PZC values of the soil treated at 373 and 573 K indicated the presence of iron oxide. The soil calcined between 773 and 1173 K shows a PZC almost coincident with the respective values of kaolinite. At 1373 K, the PZC of the soil is nearer to the value of iron oxide. In the entire temperature range studied the PZC values were lower than the IEP values. An approach of PZC and IEP values was observed after a partial removal of iron oxide by the dithionite-citrate-bicarbonate (DCB) method. The analyses of the PZC and IEP values, of electron probe micro analysis (EPMA) data and of specific surface areas evidence a specific adsorption of iron oxide on kaolinite. Finally, the dissolution sequence of iron and aluminium contained in soil was determined using hydrochloric acid.     

Zn-Al类水滑石结构正电荷对内禀电离平衡常数的影响

采用电势滴定(potentiometric titration,PT)法测定了Zn-Al类水滑石(HTlc)的零净电荷点(pHPZNC);利用电势滴定数据直接计算得到Zn-Al HTlc的内禀电离平衡常数(pKa2int)和质子吸附自由能(G0ads,2);研究了结构电荷密度(σp)对pKa2int 和G0ads,2的影响.结果表明,随σp增加, pKa2int 和G0ads,2数值均降低,说明σp越大,带正电荷的HTlc与H＋结合力越低,HTlc去质子能力越强,H＋游离出HTlc表面的趋势越大.研究发现，HTlc的pKa2int与pHPZNC之间符合关系式: pKa2int =1.372pHPZNC－3.328.     

The Isoelectric Point of an Exotic Oxide: Tellurium (IV) Oxide

The pH-dependent surface charging of tellurium (IV) oxide has been studied. The isoelectric point (IEP) of tellurium (IV) oxide was determined by microelectrophoresis in various 1-1 electrolytes over a concentration range of 0.001–0.1 M. In all electrolytes studied and irrespective of their concentration the zeta potential of TeO₂ was negative over the pH range 3–12. In other words the IEP of TeO₂ is at pH below 3 (if any). TeO₂ specifically adsorbs ionic surfactants, and their presence strongly affects the zeta potential. In contrast the effect of multivalent inorganic ions on the zeta potential of TeO₂ is rather insignificant (no shift in the IEP). In this respect TeO₂ is very different from metal oxides.     

Measurements and theoretical interpretation of points of zero charge/potential of BSA protein

The points of zero charge/potential of proteins depend not only on pH but also on how they are measured. They depend also on background salt solution type and concentration. The protein isoelectric point (IEP) is determined by electrokinetical measurements, whereas the isoionic point (IIP) is determined by potentiometric titrations. Here we use potentiometric titration and zeta potential (ζ) measurements at different NaCl concentrations to study systematically the effect of ionic strength on the IEP and IIP of bovine serum albumin (BSA) aqueous solutions. It is found that high ionic strengths produce a shift of both points toward lower (IEP) and higher (IIP) pH values. This result was already reported more than 60 years ago. At that time, the only available theory was the purely electrostatic Debye-Hu?ckel theory. It was not able to predict the opposite trends of IIP and IEP with ionic strength increase. Here, we extend that theory to admit both electrostatic and nonelectrostatic (NES) dispersion interactions. The use of a modified Poisson-Boltzmann equation for a simple model system (a charge regulated spherical colloidal particle in NaCl salt solutions), that includes these ion specific interactions, allows us to explain the opposite trends observed for isoelectric point (zero zeta potential) and isoionic point (zero protein charge) of BSA. At higher concentrations, an excess of the anion (with stronger NES interactions than the cation) is adsorbed at the surface due to an attractive ionic NES potential. This makes the potential relatively more negative. Consequently, the IEP is pushed toward lower pH. But the charge regulation condition means that the surface charge becomes relatively more positive as the surface potential becomes more negative. Consequently, the IIP (measuring charge) shifts toward higher pH as concentration increases, in the opposite direction from the IEP (measuring potential).     

Studies on intrinsic ionization constants of Fe-Al-Mg hydrotalcite-like compounds

The theoretical analysis of the intrinsic ionization constant (K(a2)(int)) of Fe-Al-Mg hydrotalcite-like compounds (HTlc) possessing permanent charges was first performed using the double extrapolation method proposed by James et al. The theoretical permanent charge density (sigma(p,T)) of the HTlc sample was calculated from the crystal structure of HTlc, and the influence of sigma(p,T) on the K(a2)(int) was also examined. From the experimental results, these conclusions can be obtained: the zero point of the charge (pH(ZPC)) of Fe-Al-Mg HTlc increases with decreased Fe3+ content and increases with increased Mg2+ in the HTlc. The pK(a2)(int) of Fe-Al-Mg HTlc also increases with decreased Fe3+ and increased Mg2+ content in the sample; furthermore, the pK(a2)(int) of Fe-Al-Mg HTlc increases with decreased sigma(p,T).