Generalization of thermodynamic Langmuir isotherm for mixed-gas adsorption equilibria

This work presents a comprehensive thermodynamic model for both pure component isotherms and mixed-gas adsorption equilibria. A generalization of thermodynamic Langmuir isotherm, the proposed model assumes competitive adsorption of multiple adsorbates on adsorbent surface for mixed-gas adsorption equilibria, and it applies an area-based adsorption nonrandom two-liquid activity coefficient model in the activity coefficient calculations for the adsorbate phase. The resulting generalized Langmuir isotherm properly captures both surface loading dependence and adsorbate phase composition dependence for mixed-gas adsorption equilibria. The model is validated with accurate representations of gas adsorption equilibrium data for varieties of unary, binary, and ternary gas systems. The model results are further compared with those calculated from extended Langmuir isotherm and Ideal Adsorbed Solution Theory.     

负载氧化铁树脂吸附巴戟天多糖热力学动力学参数辨识

在建立巴戟天多糖在负载氧化铁树脂上吸附数学模型的基础上,采用多参数优化的非线性拟合方法,估算巴戟天多糖在负载氧化铁树脂上吸附热力学、动力学参数,并将优化计算所得到的流出曲线与实验流出曲线进行比较。结果表明：多参数优化拟合得到的巴戟天多糖理论流出曲线与实验流出曲线比较吻合。采用该方法测定不同pH值和离子强度下巴戟天多糖的吸附热力学、动力学参数结果表明：弱碱性条件下巴戟天多糖的平衡吸附容量高于酸性环境,在pH值为8．0时达到最大;随着离子强度的增大,巴戟天多糖在负载氧化铁树脂上的吸附量略有增加。     

MODELLING OF PROTEIN ADSORPTION IN A FIXED-BED: SINGLE AND TWO-SOLUTE BREAKTHROUGH BEHAVIOUR

Single- and two-solute adsorption breakthrough curves of lysozyme and bovine serum albumin on the cation exchanger SP-Sepharose Fast Flow were studied in this paper. A simplified mathematical model was used to model these data. Input parameters of the model such as equilibrium and kinetic parameters were estimated from single-solute batch experiments. For single-component adsorption in a fixed-bed, the breakthrough behaviour of lysozyme was well modelled. In contrast, significant deviations were observed between the measured and theoretical breakthrough curves of albumin. It was shown that the equilibrium parameters measured from batch experiments failed to account for the behaviour of albumin in the fixed-bed. The bisolute system consisting of the simultaneous adsorption of lysozyme and albumin was also modelled using the same set of parameters derived from single-solute batch experiments. Deviations were observed between the measured and theoretical breakthrough curves for both proteins, indicating that the effects of multicomponent equilibria and kinetics must be taken into consideration in parameter estimation.     

EFFECT OF pH AND IONIC STRENGTH ON COMPETITIVE ADSORPTION OF ERYTHROMYCIN A AND C ONTO MACROPOROUS RESIN SEPABEAD SP825 AT DIFFERENT TEMPERATURES

Equilibrium adsorption experiments were carried out to investigate the effect of pH and ionic strength on competitive adsorption of erythromycin A (EA) and C (EC) in aqueous solution onto macroporous resin, Sepabead SP825, at different temperatures. The equilibrium data for the binary system were analyzed using the extended Langmuir isotherm, and the characteristic parameters were determined. The maximum adsorption capacities for both EA and EC were obtained at pH 8.5, ionic strength 0.4 mol · L^?1 NaCl, and 303 K. Selectivity of Sepabead SP825 for EA and EC was also studied. The results suggested that EA was preferred over EC, and the increase of ionic strength and temperature in neutral solution was to the benefit of the separation of EA and EC.     

Single component and competitive adsorption of propane, carbon dioxide and butane on Vycor glass

Equilibrium of gas phase adsorption on Vycor glass has been investigated. Adsorption isotherms for propane, carbon dioxide and butane as pure gases, binary mixtures and ternary mixtures were determined experimentally as a function of temperature using a volumetric method. The single-component isotherms were described with the Langmuir and Freundlich equations. Additionally, a second order isotherm based on statistical thermodynamics and an isotherm equation based on vacancy solution theory taking into account real phase behavior were used for fitting single-component equilibrium data. In order to describe the measured partial isotherms for binary mixtures, at first simple extensions of the single-component isotherm models were used, i.e., the conventional competitive Langmuir model and a multi-Freundlich equation based on the ideal adsorbed solution theory (IAS). Since these two simple isotherm models failed to represent the unusual competitive behavior observed, three model extensions using additional mixture parameters were applied, i.e., two modified multi-Langmuir equations based on: (a) statistical thermodynamics and (b) vacancy solution theory and a modified multi-Freundlich IAS model correcting spreading pressure uncertainties. These three model equations were found to be capable to describe the observed behavior better. Finally, the measured partial adsorption equilibrium data of the ternary system were correlated based on the extended equations using the determined additional binary parameters. The results obtained reveal the difficulty to predict accurately multi-component adsorption equilibria.     

Rapid and selective separation for mixed proteins with thiol functionalized magnetic nanoparticles

ABSTRACT: Thiol group functionalized silica-coated magnetic nanoparticles (Si-MNPs@SH) were synthesized for rapid and selective magnetic field-based separation of mixed proteins. The highest adsorption efficiencies of binary proteins, bovine serum albumin (BSA; 66 kDa; pI = 4.65) and lysozyme (LYZ; 14.3 kDa; pI = 11) were shown at the pH values corresponding to their own pI in the single-component protein. In the mixed protein, however, the adsorption performance of BSA and LYZ by Si-MNPs@SH was governed not only by pH but also by the molecular weight of each protein in the mixed protein.     

亚甲基蓝在石棉尾矿酸浸渣上的吸附行为

采用XRD、FT-IR等手段分别对石棉尾矿和石棉尾矿酸浸渣进行表征。利用活化煅烧的石棉尾矿酸浸渣对亚甲基蓝(MB)进行静态吸附研究, 探讨了吸附剂投加量、吸附时间、pH值、离子强度和温度等因素对吸附作用的影响。结果表明:pH值、离子强度和温度对亚甲基蓝在石棉尾矿酸浸渣上的吸附影响较大。当pH<4.5时, 吸附量随着pH值的增大而增大, 随后pH值增大, 吸附量基本不变;亚甲基蓝在石棉尾矿酸浸渣上的吸附随离子强度的增大而降低;通过相关热力学研究计算吸附过程为吸热过程, 即高温利于吸附;亚甲基蓝在石棉尾矿酸浸渣上的吸附动力学符合Lagrange准二级方程;热力学符合Langmuir等温线方程。     

双甘膦修饰磁性四氧化三铁纳米微球吸附DNA的研究

用双甘膦(PMIDA)修饰磁性四氧化三铁纳米微球(MNP)并负载Zn2+制得了PMIDA-Zn2+修饰磁性微球吸附剂。考察了吸附溶液的pH值、离子强度、吸附时间、吸附温度等因素对DNA吸附的影响。结果表明,当吸附剂用量为10mg、pH值为5.0、离子强度(NaCl浓度)为2.0mol.L-1、吸附时间为20min、吸附温度为35℃时,吸附率可达80%,吸附容量为21mg.g-1。被吸附的DNA用3.5%的氨水能完全洗脱。将PMIDA-Zn2+修饰磁性微球用于玉米DNA的提取,所得DNA纯度较高,效果令人满意。     

应用Wilson方程和均相溶液理论计算固液吸附平衡

固液吸附平衡计算对于吸附分离设计具有重要意义。采用吸附质固体溶液理论并用Wilson方程描述各组分之间的相互作用,计算了6个烃类二元液体混合物在分子筛NaX和KBaY、硅凝胶和活性炭上的吸附平衡数据,进一步考察了该理论的适用性和计算精度。结果表明,该理论模型可以较好地关联二元液相混合物在固体表面的吸附等温线,关联结果的总平均相对偏差为5.0%,而且该模型可以预测其他温度下的吸附平衡,预测精度也在5%之内。     

A study on the adsorption behavior of protein onto functional microspheres

Adsorption has been investigated using bovine serum albumin (BSA) as the model protein and sulfonated microspheres as the matrix. The adsorption appears to be sensitive to time, pH, and ionic strength, and the presence of sulfonate groups can play important roles in this process, increasing the adsorption rate and the amount of protein adsorbed, as well as influencing the interaction of BSA molecules. Fittings from Langmuir's and Freundlich's isotherms indicate that the actual adsorption becomes more complicated than the ideal process, due to the presence of intermolecular interactions of BSA. The determinations under different pH conditions (pH 2.2, 4.3, 7.4) show that near the isoelectric point of BSA (pI 4.7), the amount of protein adsorbed reached a maximum value, and a higher or lower pH resulted in a significant decrease in amount adsorbed. The effect of ionic strength is, however, closely associated with the operating conditions. Copyright © 2005 Society of Chemical Industry     

Isotherm,Kinetic, and Thermodynamic of Cationic Dye Removal from Binary System by Feldspar

In this paper, the isotherm, kinetic, and thermodynamic of cationic dye removal onto inorganic adsorbent (Feldspar) were investigated in single and binary systems. Basic Red 18 (BR18) and Basic Blue 41 (BB41) were used as cationic dyes. The characterization of the Feldspar was carried out using X-ray fluorescence (XRF), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM) techniques. The effect of operational parameters such as adsorbent dosage, initial dye concentration, pH, ionic strength, and temperature on dye removal was studied. It was found that the adsorption of BR18 and BB41 onto Feldspar followed with Langmuir and extended Langmuir isotherms in single and binary systems, respectively. Adsorption kinetic of dyes was found to conform to pseudo-second order kinetic in single and binary system. The thermodynamic data showed that dye adsorption onto Feldspar was spontaneous, endothermic, and physisorption reaction. Based on the data of the present investigation, one could conclude that the Feldspar as an eco-friendly and low-cost adsorbent might be a suitable alternative to remove dyes from colored aqueous solutions containing cationic dyes.     

Adsorption equilibrium of amino acids and antibiotics on non‐ionic polymeric sorbents

Adsorption equilibria of two amino acids (phenylalanine and tryptophan) and two antibiotics (penicillin G and cephalosporin C) from aqueous solutions onto non‐ionic polymeric sorbents (XAD‐4 and XAD‐16) were investigated under various experimental conditions such as pH, temperature and organic solvents. The assumption that amino acids adsorbed on polymeric sorbents were desorbed by competitive adsorption with organic solvent as a desorbate was verified using binary adsorption data for amino acids (phenylalanine and tryptophan) and organic solvents (isopropyl alcohol and methanol) on XAD‐4 and XAD‐16. The experimental data were predicted by using multicomponent adsorption models of an Extended‐Langmuir (EL) equation and an ideal adsorbed solution theory (IAST) based on the Langmuir equation as a single‐component isotherm. Copyright © 2004 Society of Chemical Industry     

蛋白质离子交换的空间质量作用模型分析

引　言离子交换层析具有分离容量大、选择性高和介质种类多、价格适中等特点 ,是蛋白质类生物大分子分离纯化的主要手段[1] .离子交换或吸附平衡研究是离子交换层析过程设计和优化分析的基础 ,也是分离实践中评价和选择离子交换介质的重要步骤 .目前已提出多种模型用于描述离子交换平衡 ,其中应用最多的是基于Ｌａｎｇｍｕｉｒ理论的经验模型[2 ] .但是 ,Ｌａｎｇｍｕｉｒ模型不能直接反映溶液离子强度对平衡的影响 ,不利于在盐浓度梯度洗脱的离子交换层析过程中的应用 .近年来 ,基于离子交换反应和蛋白质空间屏蔽作用的空间质量作用模型受…     

Cu2+、Cd2+、Zn2+在高炉水淬渣上的竞争吸附特性

利用等温吸附法考察了高炉水淬渣对Cu²⁺、Cd²⁺、Zn²⁺的单组分吸附和竞争吸附性能。结果表明,单一组分吸附时,金属离子吸附等温线属于“H”形等温线,吸附平衡符合Langmuir吸附等温模型,高炉水淬渣吸附的顺序为Cu²⁺ >Cd²⁺ >Zn²⁺,这与重金属离子电负性、水合离子半径及荷径比等有关。当加入竞争离子后,Cu²⁺的吸附等温线基本维持原来形状,且仍旧与Langmuir吸附等温模型比较相符,而Cd²⁺ 和Zn²⁺的吸附无法与现有等温吸附模型很好地拟合,等温线的形状由于竞争作用也与传统的等温线均不相同,同时各金属离子的吸附量都比单组分的吸附量降低了。吸附动力学过程先是一个快速阶段,然后进入慢速阶段。无论是单组分还是竞争条件下,伪二级动力学方程拟合结果较好,说明高炉水淬渣与Cu²⁺、Cd²⁺、Zn²⁺之间的吸附过程主要是以化学吸附为主。     

二元液体混合物非理想吸附平衡数据的预测

根据气相吸附和液相吸附的热力学一致性条件 ,从溶液理论、表面热力学出发并结合相交换模型 ,提出从气相吸附平衡数据预测二元液体混合物吸附平衡的模型 ,模型中仅含 4个未知参数 .应用该模型对二元液体吸附体系进行了预测 ,结果与实验数据相当吻合     

Propane/Propylene Separation by Simulated Moving Bed II. Measurement and Prediction of Binary Adsorption Equilibria of Propane,Propylene, Isobutane,and 1-Butene on 13X Zeolite

Abstract

The design of a simulated moving bed (SMB) process relies on valid thermodynamic predictions of multicomponent adsorption built up from accurate binary adsorption equilibrium data. Experimental adsorption equilibria of binary mixtures constituted by propane, propylene, isobutane and 1-butene on 13X zeolite were determined using breakthrough experiments at 373 K and 150 kPa. In addition, these binary adsorption experiments allow to confirm the choice of isobutane as an interesting desorbent for the separation of propane-propylene by SMB, since it has an intermediate selectivity between the two species to separate. Various prediction models are available in the literature but only a few of them have both physical and thermodynamical consistency. The ideal adsorbed solution theory (IAST), the thermodynamically consistent extended Toth model (TCET), and the physically-consistent extended Toth isotherm (PCET) were used to predict binary adsorption equilibria from pure component adsorption isotherms parameters. The PCET model was found suitable for representing the adsorption equilibrium of the different hydrocarbon mixtures with a reasonably good accuracy.     

pH值和离子强度对空间质量作用模型参数的影响

以牛血清白蛋白（BSA）为模型蛋白质研究了pH值和离子强度对空间质量作用模型参数的影响。通过静态吸附实验确定了不同pH值和离子强度条件下BSA在阴离子交换剂DEAE-Spherodex M上的吸附平衡,利用色谱实验及非线性最小二乘法确定模型参数。研究发现,只有在pH值远大于BSA等电点时,蛋白质的特征电荷数和空间因子才为常数;离子交换平衡常数不仅是pH值的函数,也受到液相离子强度的影响。     

阴离子交换剂DEAE-Spherodex M的蛋白质吸附性能

通过间歇吸附实验,采用Langmuir等温方程和改进的平行扩散模型,研究了牛血清白蛋白和γ 球蛋白在阴离子交换剂DEAE SpherodexM中的静态和动态吸附行为,分析了吸附过程的热力学参数。研究发现,阴离子交换剂的吸附平衡是吸热反应,对于较宽分子尺寸范围的蛋白质,DEAE SpherodexM均具有较高的离子交换吸附速率。研究表明,DEAE SpherodexM具有较好的机械强度、化学和热稳定性、稳定的功能基、较高的交换容量和较快的离子交换速度,是一种较好的蛋白质分离介质。     

改性蒙脱石吸附亚甲蓝的研究

取钠型蒙脱石和钙型蒙脱石,经铜离子交换反应使其改性。研究改性前后蒙脱石吸附亚甲蓝的能力及其受温度、介质pH值和离子强度的影响,并就吸附等温线和相关热力学参数进行分析。结果表明：不论是钠型还是钙型蒙脱石,经铜离子处理后,二者吸附亚甲蓝的能力均有所下降,但改性钠型蒙脱石下降的幅度要大于改性钙型蒙脱石;介质pH值和离子强度对蒙脱石和改性蒙脱石吸附性能的影响有差异,而吸附温度对各吸附剂吸附性能的影响程度则相近;改性蒙脱石和蒙脱石吸附亚甲蓝的等温线均能较好的符合BET和Langmuir等温方程,在298．15K下,其吸附过程均为热力学自发过程。     

Adsorption of trypsin onto magnetic ion‐exchange beads of poly(glycidylmethacrylate‐co‐ethyleneglycoldimethacrylate)

Magnetic beads were prepared from glycidyl methacrylate (GMA), and ethyleneglycol dimethylmethacrylate (EGDMA) in the presence of Fe₃O₄ nano‐powder via suspension polymerization. The magnetic beads were characterized by surface area measurement, electron spin resonance (ESR), and scanning electron microscopy (SEM). ESR data revealed that the beads were highly super‐paramagnetic. The effects of contact time, pH, ionic strength, and temperature on the adsorption process have been studied. Adsorption equilibrium was established in about 120 min. The maximum adsorption of trypsin on the magnetic beads was obtained as 84.96 mg g^?1 at around pH 7.0. At increased ionic strength, the contribution of the electrostatic component to the overall binding decreased, and so the adsorption capacity. The experimental equilibrium data obtained trypsin adsorption onto magnetic beads fitted well to the Langmuir isotherm model. The result of kinetic analyzed for trypsin adsorption onto magnetic ion‐exchange beads showed that the second order rate equation was favorable. It was observed that after six adsorption–elution cycle, magnetic beads can be used without significant loss in trypsin adsorption capacity. Finally, the magnetic beads were used for separation of bovine serum albumin (BSA) and trypsin from binary solution in a batch system. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008