Impact of Various Parameters Over the Stability of Water-in-Vegetable Oil Emulsion

Theory regarding emulsification, its coalescence and impact of emulsifier over its stability has been updated. For the verification of the proposed theory, water-in-oil emulsion was prepared by mixing water and soybean oil in the presence and absence of emulsifier, monoglyceride. The effect of different parameters like emulsification time, contents of water, and concentration of emulsifier has been investigated on the emulsification and coalescence process of the emulsion. It was noted that the emulsion quality was highest if the mixture was homogenized for about 15 minutes and the water contents were 40% v/v. The addition of monoglyceride up to 0.5% w/v gave the most stable emulsion having higher quality than other composition. The results obtained were compared with the proposed theory and found to have good compositions.      

木质素系和萘系分散剂在煤水界面的吸附性能

研究了两种木质素类分散剂SL(木质素磺酸钠)和MSSL(改性磺化碱木质素钠盐)和一种萘系分散剂(FDN)在大同煤表面的吸附量和动力学, 结果表明, SL和MSSL在煤表面的吸附量远比FDN的大, 但是拟合所得的Langmuir平衡常数K和吸附速率常数ka都比FDN的小, 这表明SL和MSSL在煤表面的吸附能力比FDN略差, 吸附速率较慢. 采用IR和XPS研究了煤表面分散剂吸附层的结果表明, 吸附了SL和MSSL的煤表面具有明显的“红移”现象, 并且SL和MSSL在煤表面的吸附层厚度分别为7.22和4.61 nm, 而FDN的吸附层厚度较小, 为2.11 nm. 分析认为, SL和MSSL在煤表面的吸附以氢键力为主, 吸附量较大, 吸附层较厚, 在煤表面呈多点式吸附; FDN主要以π电子极化吸附在煤表面呈卧式吸附, 吸附强度较大, 吸附层较薄.     

表面活性剂和聚乙烯吡咯烷酮在ZrO2上的吸附对其悬浮体稳定性的影响

研究了水溶液中十二烷基苯磺酸钠（ＳＤＢＳ）、溴代十四烷基吡啶（ＴＰＢ）和聚乙烯吡咯烷酮（ＰＶＰ）在ＺｒＯ２上的吸附及对ＺｒＯ２水悬浮体稳定性的影响。结果表明：ｐＨ＝２．４时ＳＤＢＳ在ＺｒＯ２上的吸附等湿线为ＬＳ型，ｐＨ＝７．０时ＴＰＢ的吸附等温线为Ｓ型，吸附等温线与ＺｒＯ２粒子ζ电势变化同线有大体一致的关系。在最大吸附量时ＺｒＯ２粒子ζ电势较大，且吸附的表面活性剂离子形成大部分亲水基朝向水相的表面     

铀酰离子吸附在高岭土基面的分子动力学模拟

为研究铀酰离子在高岭土不同基面上的吸附, 对含有0.01 mol·L^-1碳酸铀酰液相和9×9×3个高岭土单胞的粘土固相的模拟盒子进行了分子动力学模拟. 从模拟的截图中直观地观察到了铀酰离子的吸附位点, 由径向分布函数得到了铀酰离子与水中氧原子的配位情况. 利用原子密度剖面图讨论铀酰离子在两个基面上的吸附倾向, 并从原子密度剖面图和均方位移等角度证实了铀酰离子在硅氧面上形成了外界配合物. 从理论上证明了表面配合模型对于吸附位点所做简化的合理性.     

Kinetic of Adsorption of Urea Nitrogen onto Chitosan Coated Dialdehyde Cellulose under Catalysis of Immobilized Urease

The adsorption of urea nitrogen onto chitosan coated dialdehyde cellulose (CDAC) under catalysis of immobilized urease in gelatin membrane (IE) was studied in batch system. The pseudo first-order and second-order kinetic models were used to describe the kinetic data, and the rate constants were evaluated. The experimental data fitted well to the second-order kinetic model.     

聚丙烯酸对自然水体生物膜吸附镉的影响

选择聚丙烯酸(PAA)为水中溶解态高分子天然有机质的代表, 研究了PAA对自然水体生物膜吸附重金属Cd的影响, 包括不同浓度的PAA对吸附的影响, PAA对特定pH下吸附等温线的影响以及不同pH下按不同顺序添加PAA时对吸附的影响. 研究结果表明, PAA的存在一般会降低生物膜对Cd的吸附, 其影响程度与PAA的浓度、 溶液pH、 吸附顺序及生物膜厚度等有关. PAA与Cd的浓度比越高, 其对吸附的影响越显著. 吸附溶液pH越高, PAA的影响越显著. 吸附顺序对吸附的影响在pH较低时不明显, 当pH较高时, 先加PAA后加Cd及两者同时吸附时对吸附的降低作用接近且较大, 先加Cd后加PAA时对吸附的降低作用相对较小. 生物膜较薄时PAA的影响更显著. PAA对生物膜吸附Cd的影响主要由PAA与生物膜之间对Cd的竞争以及三元表面配合物的生成与吸附2种因素共同决定. 高pH会促进PAA与Cd的配合而不利于带负电的配合物在生物膜上的吸附.     

Effects of surface structure on the molecular projection area. Adsorption of argon and nitrogen onto defective surfaces

This paper studies the effects of surface structure (defective surfaces) on the molecular projection area of argon and nitrogen at 77 K. The determination of the molecular projection area is based on choice of the surface area of the structure studied and the adsorption data obtained from the GCMC simulation. Two methods were used to determine the surface area: the flat surface area that are commonly used in the literature and the geometrical surface area. The molecular projection areas of argon and nitrogen at 77 K vary with pressure over the recommended range for BET plot (reduced pressures from 0.05 to 0.3) and also they varies with the percentage of defects on the surface. Additionally, it is seen that the geometrical surface area method gives molecular projection area of defective surfaces values that are in accordance with the experimental value reported in the literature.     

FT-IR、XPS和DFT研究水杨酸钠在针铁矿或赤铁矿上的吸附机理

采用傅里叶变换红外(FT-IR)光谱、X射线光电子能谱(XPS)以及基于周期平面波的密度泛函理论(DFT)分别研究了水杨酸钠在针铁矿或赤铁矿表面上的吸附结构,并将计算得到的光电子能谱移动(CLS)和电荷转移与实验得到的XPS结果进行对比。FT-IR结果表明,水杨酸钠可能以双齿双核(V)和双齿单核(IV)的形式分别吸附于针铁矿或赤铁矿表面。由DFT计算结果可知,水杨酸钠在针铁矿(101)晶面上形成双齿双核化合物(V)的吸附能为-5.46 eV。而水杨酸钠在针铁矿(101)晶面上形成双齿单核化合物(IV)的吸附能为3.80 eV,因此水杨酸钠在针铁矿上基本不以双齿单核化合物(IV)构型存在。水杨酸钠在赤铁矿(001)晶面上形成双齿单核化合物(IV)时吸附能为-4.07 eV,说明水杨酸钠在赤铁矿(001)晶面上形成了双齿单核化合物(IV)。另外,理论计算的针铁矿(101)晶面上吸附位点铁原子的Fe 2p的CLS值(-0.68 eV)与实验观察到的Fe 2p的CLS值(-0.5 eV)吻合。理论计算的赤铁矿(001)晶面上吸附位点铁原子的Fe 2p的CLS值(-0.80 eV)与实验观察到的Fe 2p的CLS值(-0.8 eV)吻合。因此,水杨酸钠吸附在针铁矿表面时能够通过羧酸基团上一个氧原子和酚羟基上的氧原子与针铁矿(101)表面上的两个铁原子形成双齿双核(V)结构,而在赤铁矿(001)表面上,水杨酸钠中羧酸基团上一个氧原子和酚羟基上的氧原子与赤铁矿(001)表面上的一个铁原子形成了双齿单核(IV)结构。     

Adsorption of Brilliant Yellow onto Sepiolite: Evaluation of Thermodynamics and Kinetics and the Application of Nonlinear Isotherm Models

We studied the adsorption of Brilliant Yellow (BY) from aqueous solutions onto sepiolite and determined the adsorption equilibrium isotherms. We applied pseudo-first-order and pseudo-second-order kinetic models; the adsorption of BY onto sepiolite was best described by the pseudo-second-order kinetic model. The experimental data obtained at different temperatures were analyzed using various isotherm models; the Koble–Corrigan isotherm model provided the best fits for the BY adsorption data at all temperatures. The thermodynamic parameters of the BY adsorption onto sepiolite indicated that the adsorption process is spontaneous and exothermic in nature.     

Adsorption of Polycation and Anionic Surfactant onto Iron Surfaces and the Inhibition of Carbon Dioxide Corrosion

The adsorption process of two polycations (pDADMAC and C‐PAM) with different charge densities has been investigated using the quartz crystal microbalance technique with dissipation monitoring (QCM‐D). The effect of the charge density of the polycation, the NaCl concentration, and the complexation with an anionic surfactant are addressed in this work. X‐ray photoelectron spectroscopy and atomic force microscopy were utilized to analyze the adsorbate with respect to the film coverage and film structure. The corrosion‐inhibiting performance of the films on high‐purity iron in a CO₂ saturated brine, at 25°C, 1 bar CO₂, and pH 4, was investigated by the linear polarization resistance technique. It was found that the polycations adsorbed onto the iron surface, but the corrosion rate of 1 mm yr^?1 was not lowered. However, the polycations formed a complex with an anionic surfactant, and such films showed excellent inhibition performance. Both films, of pDADMAC/SDS and of C‐PAM/SDS, lowered the corrosion rate of iron below 0.01 mm yr^?1. The SDS concentration was below the cmc. It is believed that the SDS adsorbed into the preadsorbed polycation film, forming a complex structure resulting in a hydrophobic and dense film.     

Adsorption behavior and mechanism of Cu(II) onto carbonate-substituted hydroxyapatite in the presence of humic acid

In this study, adsorption behavior and mechanism of Cu(II) onto carbonate-substituted hydroxyapatite (CHAP) in the absence and presence of humic acid (HA) were studied in batch experiments. The results showed that carbonate incorporation in HAP could significantly enhance the adsorption of Cu(II). In ternary systems, the presence of HA led to an increase in Cu(II) adsorption, dependent on HA concentration. Kinetic studies showed that pseudo-second-order kinetic model better described the adsorption process of Cu(II) onto CHAP and equilibrium data were best described by Sips models. The order of addition sequences of substrates was found to have a noticeable effect on Cu(II) adsorption onto CHAP. The general trend with respect to Cu(II) adsorption being: (CHAP–Cu)–HA?>?(CHAP–HA)–Cu?>?(Cu–HA)–CHAP. The present findings were important for estimating and optimizing the removal of Cu(II) ions by using CHA as a potential adsorbent.     

Near—infrared SERS Study of the Adsorption of a PMMA Dip—coated onto Silver Mirror Substrate

The interface between a-PMMA thin film and silver mirror substrate was investigated using surface-enhanced Raman scattering (SERS). It is found that the molecular chain axis of a-PMMA tends to parallel the substrate in the interface. When the sample is annealed at different temperatures, some interesting changes appear in the SERS spectra. The spectra differences and their transition are due to the surface geometry change of the ester group.     

固定波长同步荧光光谱参数的理论计算

基于荧光激发光谱和发射光谱对波长呈高斯分布的设定,本文推导出固定波长同步荧光光谱峰峰值位置、相对强度和半峰宽度等3个主要光谱参数的理论计算式。所提出的计算式应用于若干荧光物质光谱参数的计算,并和实测值、文献计算值作了对照。结果表明,和文献计算方法相比,本法与所研究物质的实际光谱参数较为接近,可为固定波长同步荧光光谱参数的理论计算提供一有效方法。     

Adsorption of poly(vinyl formamide-co-vinyl amine) onto silica particle surfaces and stability of the formed hybrid materials

In order to produce silica/polyelectrolyte hybrid materials the adsorption of the polyelectrolyte poly(vinyl formamide-co-vinyl amine), P(VFA-co-VAm) was investigated. The adsorption of the P(VFA-co-VAm) from an aqueous solution onto silica surface is strongly influenced by the pH value and ionic strength of the aqueous solution, as well as the concentration of polyelectrolyte. The adsorption of the positively charged P(VFA-co-VAm) molecules on the negatively charged silica particles offers a way to control the surface charge properties of the formed hybrid material. Changes in surface charges during the polyelectrolyte adsorption were studied by potentiometric titration and electrokinetic measurements. X-ray photoelectron spectroscopy (XPS) was employed to obtain information about the amount of the adsorbed polyelectrolyte and its chemical structure. The stability of the adsorbed P(VFA-co-VAm) was investigated by extraction experiments and streaming potential measurements. It was shown, that polyelectrolyte layer is instable in an acidic environment. At a low pH value a high number of amino groups are protonated that increases the solubility of the polyelectrolyte chains. The solvatation process is able to overcompensate the attractive electrostatic forces fixing the polyelectrolyte molecules on the substrate material surface. Hence, the polyelectrolyte layer partially undergoes dissolving process.     

Liquidus Curves of AgNO3(aq) Calculated from the Modified Adsorption Isotherm Model for Aqueous Electrolytes

Summary. The Brunauer-Emmett-Teller (BET) adsorption isotherm as modified by Robinson and Stokes is used to calculate the liquidus curve of AgNO₃(aq) including the eutectic point and metastable phases. The simplified approach described here predicts the liquidus curves by using sparse data and readily available constants.     

苯乙烯丙烯酸共聚物分散剂在氟铃脲颗粒界面的吸附性能

利用残余质量浓度法、ζ电位测定、红外光谱和XPS法系统地研究了苯乙烯丙烯酸共聚物(MOTAS)分散剂在氟铃脲颗粒界面的吸附量、吸附状态、ζ电位、吸附作用力和吸附层厚度等性能. 实验结果表明, MOTAS分散剂在氟铃脲界面的吸附符合Langmuir吸附等温式, 其饱和吸附量和吸附平衡常数k、ζ电位和吸附层厚度均随MOTAS分散剂相对分子量增加而增大, MOTAS分散剂在氟铃脲界面呈多点吸附, 氢键是分散剂分子与氟铃脲界面结合的重要作用力. 分析实验结果发现, MOTAS分散剂在氟铃脲颗粒界面吸附后具有静电排斥和空间位阻双重作用.     

Liquidus Curves of NaNO3(aq) Calculatedfrom the Modified Adsorption Isotherm Modelfor Aqueous Electrolytes

Summary.  The Stokes-Robinson modification of the Brunauer-Emmett-Teller (BET) adsorption isotherm is used to calculate the liquidus curve of NaNO₃(aq) including the eutectic point and metastable phases. The method described here represents a simplified approach to predict the liquidus curves with sparse information. Received August 9, 1999. Accepted November 4, 1999     

Voltammetric Determination of Aluminium in Haemodialysis Concentrates Using the Adsorption of the Al(III)-1,2-Dihydroxyantraquinone-3-sulphonic Acid Complex in Presence of Calcium

Abstract

This paper describes a method for the quantitative determination of aluminium in haemodialysis concentrates, based on the adsorption on a static mercury drop electrode of the Al-1,2 dihydroxyantraquinone-3-sulphonic acid complex. The signal was notably increased in presence of calcium. The electrolysis was carried out at -0.900 V. After 60 sec the aluminium contents were measured by differential pulse voltammetry. In these conditions aluminium can be determined in the range 0.65–38 ng/ml with a detection limit (3[sgrave]) of 0.20 ng/ml. The relative standard deviation was in all instances less than 2.1%.     

Adsorption of poly(ethylene glycol) s on mercury/aqueous solution interface 2. Influence of the chain length

The adsorption on a mercury/aqueous solution interface of poly(ethylene glycol)s (PEGs) with molecular weights from 200 to 20 000 was studied by a.c. voltammetry in order to understand better the adsorption of linear components of fulvic acids on hydrophobic particles in natural waters, and the influence of their adsorption on voltammetric signals. As a general trend it was noted that the equilibrium adsorption constant increases with the molecular weight while the adsorption rate decreases. The values of the maximum surface concentration F. suggest a flat configuration for adsorbed molecules for all PEGs studied.     

Formal Mathematical Analysis of the Existence of the Common Intersection Point in Relation to Determining the Parameters Describing Ion Adsorption at the Oxide/Electrolyte Interface: Comparison of the Triple and Four-Layer Models

For most oxide/electrolyte systems potentiometric titration curves measured for different ionic strengths have a Common Intersection Point (CIP) which corresponds to the Point of Zero Charge (PZC). However, there are systems where a CIP exists but the surface charge at this point does not equal zero (PZC CIP). In this paper theoretical analysis of the systems in which the PZC and CIP do not coincide is presented. It is based on the well-known 2-pK surface charging approach and Triple Layer Model (TLM) as well as the Four Layer Model (FLM) of the electric double layer. The appropriate mathematical criterion for CIP existence was applied with detailed derivations, both for TLM and FLM. Having determined in this manner the parameter values, one can draw proper conclusions about the features of oxide/electrolyte adsorption systems, in which PZC and CIP do not coincide. The values of adsorption parameters are found by fitting simultaneously the obtained theoretical expressions to both of the experimental titration isotherms, and to the individual isotherms of electrolyte cation adsorption measured using radiometric methods.