Characterisation of composite films made of konjac glucomannan (KGM), carboxymethyl cellulose (CMC) and lipid

Emulsion films prepared from konjac glucomannan (KGM), carboxymethylcellulose (CMC), with and without alkali (KOH), were characterised for selected properties such as morphological characteristics, water vapour permeability (WVP), water sorptive capacity and tensile properties. It was found that smaller lipid globules, with a homogeneous distribution, increased the apparent hydrophobicity and “tortuosity” of an emulsion film for water molecule transmission, thereby resulting in reduced WVP. This was achieved when alkaline deacetylated KGM and CMC were served as the base polymers for the emulsion, with the latter functioning as an emulsifier. Interactions between deacetylated KGM and CMC resulted in a stable emulsion.     

Dowex50W-X树脂吸附硫酸溶液中的锶

In this study, strontium adsorption from sulfuric acid solution by different Dowex 50W-X ion exchange resins was investigated. Among these resins, Dowex 50W-X8 resin showed the maximum sorption of strontium from the aqueous solutions. The effect of pH, contact time, mass of resin, temperature, and concentration of interfeting ions on strontium adsorption were evaluated to determine the optimum conditions of strontium sorption process. The kinetic models of sorption were analyzed using pseudo-first and pseudo-second order models. The results indicated that the pseudo-second order kinetic model was more appropriate than the other one. Moreover, the data obtained in this study were fitted into several sorption isotherm models and it was found that the Langmuir sorption isotherm shows the best fitting to the experimental data.     

云南某氧化铜矿氨浸液萃取工艺

以云南某氧化铜矿的氨浸液作为萃取原液,研究萃取-洗涤-反萃过程。用McCabe-Thiele等温线法,推算二级萃取和一级反萃过程中各产物含铜浓度的变化。采用分流萃取的工艺,可以避免返回使用的萃余液被稀释。对含氨量测定表明,氨浸-萃取体系的氨挥发量和水膨胀均可控制。     

Effects of ionic strength and pH on the adsorption equilibria of lysozyme on ion exchangers

The effects of ionic strength and pH on adsorption of lysozyme to three strong cation exchangers have been studied. Adsorption equilibrium data obtained using the batch techniques corresponded well to the Langmuir isotherm. Ionic strength had a considerable influence on the isotherms. In all cases, the maximum binding capacity of the three exchangers decreased while the apparent dissociation constant increased with increasing ionic strength. The maximum binding capacity also decreased while the apparent dissociation constant was not significantly affected by an increase in pH. It was found that the three exchangers exhibited different levels of binding capacity under identical solution conditions. This was shown to be caused by variation in the arrangement and distribution of charged groups. However, the ion-exchange matrix had little effect on the apparent dissociation constant.     

Water sorption isotherms of crystalline raffinose by inverse gas chromatography

The interaction of water with crystalline raffinose was studied by inverse gas chromatography. Water sorption isotherms were constructed at 30, 35, 40 and 50°C with water activity ( a_w ) values between 0.0 and 0.7. Experimental data were successfully fitted to the BET, GAB and Freundlich equations and the monolayer and sorptive capacities of raffinose were calculated. These values were found to be lower than the corresponding literature values for other sugars and were attributed to the high degree of crystallinity of raffinose. The thermodynamics of the above interaction were further studied by application of the Zimm-Lundberg cluster theory. Results indicate a strong tendency for water molecules to cluster even at relatively low water activity.     

Effect of temperature on stability of adsorbed inhibitors on steel in phosphoric acid solution

Rates of steel dissolution in 35% H₃PO₄/6% butanol (test solution) in the presence of thiosemicarbazide and seven of its derivatives were determined by spectrophotometry, weight loss and potentiodynamic and impedance techniques in the temperature range 303 to 333 K. At all temperatures, the corrosion rate decreased with increasing inhibitor concentration. Increasing temperature decreased the protection efficiency particularly at concentrations less than 2.5 × 10^–4 M. At inhibitor concentrations above 2.5 × 10^–4 M, increasing the temperature did not affect efficiency. Potentiodynamic polarization measurements indicated that the inhibitors have a strong effect on the corrosion behavior of the steel and behave as mixed type inhibitors. Thermodynamic functions obtained from this study indicate that the presence of the inhibitors increase the activation energy. The negative values of G ^* indicated spontaneous adsorption on the metal surface. A kinetic-thermodynamic model was found to describe the experimental well data at different temperatures.     

不同利用方式下黄泥土中胡敏酸对芘的吸附特性初探

采用高效液相色谱法测定三种不同利用方式下黄泥土中胡敏酸对芘的吸附效应。结果表明:桑园、水田、水杉土壤中胡敏酸对芘的吸附在低浓度范围近似线性,而浓度较高时,吸附曲线的非线性增强,三者呈现相似的非线性吸附。但是,十年时间的不同利用方式对土壤中胡敏酸元素组成影响较小,桑园、水田、水杉土壤中胡敏酸对芘的吸附分配系数有一定差别,说明不同胡敏酸对芘的吸附能力不同,必然与其组成结构有关。不同利用方式下黄泥土中胡敏酸对芘的吸附等温线用Freundlich等温方程拟合效果很好,均达到显著相关。     

Deriving Analytical Expressions for the Ideal Curves and Using the Curves to Obtain the Temperature Dependence of Equation-of-State Parameters

Different equations of state (EOSs) have been used to obtain analytical expressions for the ideal curves, namely, the Joule–Thomson inversion curve (JTIC), Boyle curve (BC), and Joule inversion curve (JIC). The selected EOSs are the Redlich–Kwong (RK), Soave–Redlich–Kwong (SRK), Deiters, linear isotherm regularity (LIR), modified LIR (MLIR), dense system equation of state (DSEOS), and van der Waals (vdW). Analytical expressions have been obtained for the JTIC and BC only by using the LIR, MLIR, and vdW equations of state. The expression obtained using the LIR is the simplest. The experimental data for the JTIC and the calculated points from the empirical EOSs for the BC are well fitted into the derived expression from the LIR, in such a way that the fitting on this expression is better than those on the empirical expressions given by Gunn et al. and Miller. No experimental data have been reported for the BC and JIC; therefore, the calculated curves from different EOSs have been compared with those calculated from the empirical equations. On the basis of the JTIC, an approach is given for obtaining the temperature dependence of an EOS parameter(s). Such an approach has been used to determine the temperature dependences of A ₂ of the LIR, a and b parameters of the vdW, and the cohesion function of the RK. Such temperature dependences, obtained on the basis of the JTIC, have been found to be appropriate for other ideal curves as well.     

Evaluation of Thermodynamic Parameters for Separation of Hexavalent Chromium by Fly Ash

Abstract

Kinetics and thermodynamic parameters of Cr⁶⁺ separation by fly ash from aqueous solution has been evaluated. It was found that the separation process is partly diffusion controlled and endothermic in nature. The mass transfer coefficient increases with an increase in temperature. The activation energy and change of enthalpy were also evaluated and found to be 17.5 kJ/mol and 14.47 kcal/mol, respectively. The free energy of the process was small but positive, and it decreases with an increase of temperature. The change of entropy was found to be small and remains unchanged over the 30 to 50°C temperature range. This process follows the Langmuir isotherm model where Q _o and b were also determined at different temperatures.     

Adsorption/desorption of phenols onto granular activated carbon in a liquid–solid fluidized bed

The adsorption/desorption of phenols in aqueous solution onto coconut‐shell granular activated carbon (GAC) in a liquid–solid fluidized bed adsorber approaching saturation capacity was investigated. Experiments were carried out using a 20 mm id adsorber under a variety of operating conditions including GAC particle sizes (0.937, 1.524 mm), GAC mass (12, 24 g), influent phenol concentration (0.367–1.071 mmol dm⁻³), surface loading of GAC (2.0, 2.5 mmol g⁻¹) and liquid flow rate (0.15, 0.2, 0.35 dm³ min⁻¹). The effect of repetitive adsorption/desorption cycles on the adsorption capacity has also been examined for phenol/GAC systems. The model based on the external mass transfer with film‐surface diffusion, surface adsorption equilibrium and internal mass transfer was proposed to simulate the breakthrough curves of the phenol adsorption/desorption process. Using the experimentally measured Langmuir isotherm equilibrium parameters in the model has been found to describe reasonably well the experimental results. © 1999 Society of Chemical Industry