THERMODYNAMIC STUDY ON ADSORPTION OF AROMATIC SULFONIC ACIDS ONTO MACROPOROUS WEAK BASE ANION EXCHANGER FROM AQUEOUS SOLUTIONS

INTRODUCTIONAromatic sulfonic acids are important intermediates in the production of a variety of synthetic dyes, opticalbrighteners, fluorescent whitening agents and pharmaceuticals. A variety of substituted benzene and naphthalenesulfonates are thus produced on a large scale in the chemical industry. Generally, aromatic sulfonic acids areprepared by sulphonation of simple aromatic hydrocarbons or their derivatives. Due to the good solubility andstrong hydrophilicity of aromatic sulfonic…     

超高交联吸附树脂吸附对硝基苯乙酮的热力学研究

比较两种超高交联聚苯乙烯吸附树脂NJ-8、AM-1与Amberlite XAD-4(以下简称XAD-4)对对硝基苯乙酮的静态吸附行为，根据吸附等温线研究了吸附热力学性质．在298～318K和研究的浓度范围内，NJ-8，AM-1、XAD-4对对硝基苯乙酮的吸附平衡数据符合Freundlich吸附等温方程．结果表明：吸附为放热过程，适当降低温度有利于吸附．计算了对硝基苯乙酮在NJ-8，AM-1、XAD-4树脂上的吸附焓变、自由能变，吸附熵变．对吸附行为作了合理的解释。     

Hydration and sorption characteristics of a polyfunctional weak-base anion exchanger after the sorption of vanillin and ethylvanillin

Features of the sorption of substituted aromatic aldehydes by a weak-base anion exchanger under equilibrium conditions are investigated using vanillin and ethylvanillin as examples. Analysis of the sorption isotherms of carbonyl compounds at different temperatures allows us to calculate the equilibrium characteristics of their sorption and assess the entropy and enthalpy contributions to the energy of the process. Hydration characteristics of the macroporous weak-base anion exchanger before and after the sorption of aromatic aldehydes are compared.     

酚醛型吸附树脂吸附咖啡因的热力学研究

利用酚醛型吸附树脂JDW－2（自制）和DuoliteS-761对咖啡因的吸附进行了研究，在303－323K和研究的浓度范围内，JDW－2和DuoliteS-761对咖啡因吸附平衡数据符合Freundlich吸附等温方程。Freundlich吸附等温线和等量吸附焓表明：JDW－2和DuoliteS-761对咖啡因吸附是放热过程，我们对咖啡因在JDW－2和DuoliteS-761上的吸附焓，自由能，吸附熵也作了测试，并对吸附行为作了合理解释。     

Thermodynamics of methane adsorption on the microporous carbon adsorbent ACC

The behavior of the thermodynamic functions (differential molar isosteric heat of adsorption, entropy, enthalpy, and heat capacity) of the adsorption system methane—microporous carbon adsorbent ACC was analyzed at different adsorption equilibrium parameters in the temperature interval from 177.65 to 393 K and in the pressure range from 1 Pa to 6 MPa. The influence of the nonideal character of the gas phase and noninertness of the adsorbent were taken into account, which resulted in the appearance of the temperature dependence of the isosteric heat of adsorption, especially in the region of high pressures of the adsorptive. For the system studied, nonideality of the gas phase exerts the main effect on the thermodynamic functions of the adsorption system. In this interval of the parameters of the adsorption system, the correction to the noninertness of the adsorbent is not higher than 2.5%. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1765–1771, September, 2008.     

一种亲水的酚羟基修饰聚苯乙烯树脂对酚类化合物的吸附热力学

在283-323K和研究的浓度范围内,苯酚、对甲苯酚、对氯苯酚和对硝基苯酚在亲水性的酚羟基修饰聚苯乙烯树脂（AM-1）与大孔吸附树脂（Amberlite XAD-4)上平衡吸附数据符合Freundlich吸附等温方程。酚类化合物在AM-1上的吸附容量比在Amberlite XAD-4上的吸附容量增加20%以上,这主要得益于AM-1表面的酚羟基入树脂的微孔结构。在较稀的溶液中AM-1对苯酚的吸附量比AmberliteXAD-4对苯酚的吸附量增加60%,表明AM-1对苯酚有特殊的选择性。Freundlich吸附等温线、相对吸附容量以及等量吸附焓表明,四种酚在两种树脂上的吸附是物理吸附过程。对酚类化合物被两种树脂吸附的吸附焓、自由能、吸附熵也作了测试,并对吸附行为作了合理的解释。     

Adsorption of cesium on a composite inorganic exchanger zirconium phosphate - ammonium molybdophosphate

The applicability of zirconium phosphate-ammonium molybdophosphate (ZrP-AMP) for the efficient removal of cesium from aqueous acidic solutions by adsorption has been investigated. The adsorption data analysis was carried out using the Freundlich, Dubinin-Raduskevich (D-R) and Langmuir isotherms for the uptake of Cs in the initial concentration range of 3.75^.10^-5-7.52^.10^-3 mol^.dm^-3 on the ZrP-AMP exchanger from nitric acid medium. The mean free energy (E) values for the adsorption of Cs were obtained from the D-R isotherm. Equilibrium adsorption values at different temperatures have been utilized to evaluate the change in enthalpy, entropy and free energy (ΔH°, ΔS°, ΔG°). The adsorption of cesium on the ZrP-AMP exchanger was found to be endothermic. This revised version was published online in August 2006 with corrections to the Cover Date.     

Determination of adsorptive properties of clay/water system: methylene blue sorption

In this study, adsorption of methylene blue onto clay was investigated. The effect of adsorption time and temperature on the adsorption process was studied. To reveal the adsorptive characteristics of the clay studied, porosity and BET surface area measurements were made. It was observed that the adsorption capacity decreases with increasing temperature, and adsorption equilibrium was attained within 1 h. It was found that the data fit well to Langmuir, Halsey, Henderson, and Harkins-Jura models but experimental data deviate significantly from BET and Freundlich models at especially high concentrations. Furthermore, isosteric adsorption enthalpy and entropy are calculated as -7.99 kJ mol(-1) and 25.41 JK(-1)mol(-1), respectively.     

Adsorption of Basic Magenta II onto H2SO4 activated immature Gossypium hirsutum seeds: Kinetics,isotherms, mass transfer,thermodynamics and process design

The adsorption of Basic Magenta II onto H₂SO₄ activated immature Gossypium hirsutum seeds was analysed using Ho, modified Freundlich, Sobkowsk–Czerwi, Blanchard, Elovich, Avrami, and modified Ritchie kinetic models by nonlinear regression-sum of normalized errors analysis. The goodness of fit was evaluated with coefficient of determination and root mean square error. The good agreement of experimental data to Avrami second-order model indicated that the mechanism of adsorption followed multiple kinetic orders. The Avrami second-order mechanism was applied to predict the rate constant of sorption and the equilibrium capacity and subsequently the obtained equilibrium adsorption capacities were utilized to find the equilibrium concentrations. Langmuir, Freundlich, Temkin, Sips and Hill isotherms were investigated to understand the nature of adsorption with the help of nonlinear regression analysis. Both Sips and Hill isotherms were best fit to the adsorption equilibrium data showing the homogeneous adsorption on the heterogeneous surface of carbon and the positive co-operative manifestations of the Basic Magenta II molecules. The mass transfer study depicted the details such as mass transfer coefficient, intra-particle diffusion rate, pore diffusion coefficient, and film diffusion coefficient. The adsorption process was found to be controlled by film diffusion. The thermodynamic parameters like, Gibbs free energy change, enthalpy change, entropy change and isosteric heat of adsorption confirmed the endothermic, feasible and spontaneous nature of adsorption. A single stage batch adsorber was designed using Sips isotherm constants to estimate the amount of carbon required for desired purification.     

两种吸附树脂对4B酸吸附行为的比较研究

研究了新型复合功能吸附树脂NDA-99和超高交联大孔吸附树脂JX-101对水溶液中4B酸(对甲苯胺-2-磺酸)的静态吸附行为和热力学特性，结果表明，NDA-99树脂对4B酸的吸附量明显大于JX-101树脂，两种树脂对4B酸的吸附均符合Freundlich吸附等温方程．其中，JX-101对4B酸的吸附属于物理吸附：NDA-99由于树脂表面存在弱碱性官能团，对4B酸的吸附表现为物理吸附和化学络合协同作用。     

枯草杆菌α-淀粉酶在一些色谱体系中的热力学和超热力学研究

通过测定不同温度范围的热力学平衡常数、焓变、熵变、自由能变和补偿温度,研究了枯草杆菌α-淀粉酶在几种色谱介质上的热力学和超热力学。结果表明,在RP-C18反相介质、Zn2+螯合的Sepharose fast-flow亲和介质和WCX-1阳离子交换介质上,当温度分别在13-30和30-50℃范围时,它们的lnKSL分别随绝对温度的倒数线性变化;而在PEG-400和修饰的PEG-400疏水色谱介质上,当温度分别在13-40和13-30℃范围时,它们的lnKSL分别随绝对温度的倒数线性减小,但当温度分别高于40℃和30℃时,它们则随绝对温度的倒数剧烈减小。通过研究不同温度范围的焓变、熵变、自由能变和α-淀粉酶构象变化之间的关系,发现在RP-C18反相和Zn2+螯合的Sepharose fast-flow亲和介质上在30- 50 ℃温度范围内,在WCX-1阳离子交换介质上在13-30 ℃温度范围内,α-淀粉酶的吸附过程由焓变和熵变共同所支配,而在Zn2+螯合的Sepharose fast-flow亲和介质上在13- 30 ℃温度范围内,在WCX-1阳离子交换介质上在30-50 ℃温度范围和在PEG-400 和修饰的PEG-400疏水色谱介质上在13-65 ℃温度范围时,α-淀粉酶的吸附过程仅仅由熵变所控制。最后,通过α-淀粉酶在这些色谱体系中的补偿温度进一步发现,它们的焓变仅仅只能通过它们构象变化所引起的熵变所补偿。     

Porous copolymer-based cation exchanger for the off-line preconcentration of aromatic amines from water

Summary A weakly polar porous copolymer and the sulfonic acid cation exchanger based on this copolymer were tested as sorbents for off-line preconcentration of aromatic amines from water. Minicolumns packed with the 1,4-di(methacryloyloxymethyl)naphthalene—divinylbenzene copolymer and the cation exchanger were used for the solid-phase extraction of polar amines. In order to study the sorption properties of these polymeric materials, the recoveries and breakthrough volumes ofp-aminophenol,o, m andp-phenylenediamine, aniline,o andp-anisidine,p-nitroaniline, ando-toluidine were determined.     

Surfactant assisted preparation and characterization of carboxymethyl cellulose Sn(IV) phosphate composite nano-rod like cation exchanger

Carboxymethyl cellulose Sn(IV) phosphate composite nano-rod like cation exchanger with diameter in the range of 20–40 nm, length in the range of 100–150 μm and particle size in the range of 21–38 nm have been successfully prepared by surfactant assisted sol–gel method. Scanning electron microscopy, transmission electron microscopy, X-ray powder diffraction, fourier transform infra red spectroscopy and thermogravimetric analysis-differential thermal analysis studies were carried out to study the structure and morphology of this composite nano-rod like cation exchanger. Freundlich adsorption isotherm is well fitted for the adsorption of pyridine on the surface of this composite nano-rod like cation exchanger. The thermodynamic parameters such as Freundlich constant, thermodynamic equilibrium constant (K ₀), standard free energy changes (ΔG ⁰), standard enthalpy changes (ΔH ⁰) and standard entropy changes (ΔS ⁰) have been evaluated. These parameters indicated that the adsorption of pyridine on the surface of composite nano-rod like cation exchanger was feasible, spontaneous and exothermic in nature which suggests for the potential application of pyridine removal from water.     

Adsorption of Zinc and Cyanide from Cyanide Effluents on Anionic Ion-exchange Resin

The adsorption of zinc and cyanide from cyanide effluents onto strong and weak basic anion exchange resins was studied in a batch adsorption system. Factors influencing the adsorption rates such as resin selection, resin amounts, contact time and temperature were studied and scanning electron microscopy-energy disperse spectroscopy(SEM-EDS) was used in the analysis. The present study shows that the adsorption capacity of resin 201×7 is better than that of resin 301. The adsorption process was relatively fast and came to equilibrium after 60 min. The kinetic data were analyzed with three models and the pseudo-second-order kinetic model was found to agree with the experimental data well. The equilibrium data could also be described well by Langmuir isotherm model. Thermodynamic parameters such as enthalpy change(ΔH⁰), free energy change(ΔG⁰) and entropy change(ΔS⁰) were calculated and the adsorption process was spontaneous and endothermic.     

Nicotinic acid adsorption thermodynamics study on carboxymethyl cellulose Ce(IV) molybdophosphate composite cation-exchanger

The thermodynamics of nicotinic acid adsorption from aqueous solution on carboxymethyl cellulose Ce(IV) molybdophosphate composite cation exchanger were studied. The composite cation exchanger was synthesized by sol–gel method and thereby characterized using scanning electron microscopy, thermogravimetric analysis, X-ray powder diffraction and fourier transform infra red spectroscopy. The analytical applicability and thermodynamic parameters, such as Freundlich constant, thermodynamic equilibrium constant (K _ο), standard free energy changes (ΔG°), standard enthalpy changes (ΔH°) and standard entropy changes (ΔS°) of this composite cation exchanger have been evaluated. The thermodynamic parameters showed that the adsorption of nicotinic acid onto composite cation exchanger is feasible, spontaneous and exothermic, suggesting their suitability for the potential application of nicotinic acid removal from waste water.     

Thermodynamics of krypton adsorption on microporous carbon adsorbent at high pressures

The behavior of the thermodynamic functions for the adsorption system krypton—microporous carbon sorbent ACC is described. The dependences of the differential molar isosteric heat of adsorption, entropy, enthalpy, heat capacity, and differential molar energy of the adsorption system on the adsorption equilibrium parameters were studied over the temperature range from 178 to 393 K and at pressures ranging from 1 to 6?106 Pa. Consideration of the non-ideality of gas phase and non-inertness of the adsorbent leads to a temperature dependence of the thermodynamic functions of the studied adsorption system, especially in the range of high pressures of the adsorptive. The non-ideality of the gas phase and the energetics of the adsorbent—adsorbate system exert the most significant effect on the thermodynamic functions. The non-inertness of the adsorbent in the investigated range of parameters of the adsorption system has a weak effect on the thermodynamic functions of adsorption. In the region of high filling of ACC micropores, the entropy increases, indicating the existence of processes, which change the structure of the adsorbate in the micropores, in particular, to form associates.     

Use of oxide minerals to abate fluoride from water

The removal of fluoride from aqueous solutions has been investigated using various oxide ores such as refractory grade bauxite, feed bauxite, manganese ore, and hydrated oxides of manganese ores (WAD). The refractory grade bauxite showed promising results. The studies were carried out as functions of contact time, pH, concentration of adsorbents, concentration of adsorbate, and temperature. The adsorption was rapid during the initial 5 min but equilibrium was attained within 120 min. The adsorption followed first-order kinetics. The present system followed the Langmuir adsorption isotherm model. Various thermodynamic parameters such as free energy, enthalpy, entropy, and equilibrium constants were calculated. The isosteric heat calculations showed that the adsorption process followed a heterogeneous model.     

An Analysis of the Interactions of BSA with an Anion-Exchange Surface Under Linear and Non-Linear Conditions

The interactions of BSA with an anion-exchange adsorbent have been studied to aid in the understanding of protein adsorption in ion-exchange chromatography. Linear chromatography, flow microcalorimetry and isotherm measurements were used to analyze adsorption energetics in the linear and overloaded regions of the equilibrium isotherm. The effects of salt type, salt and protein concentration, and temperature are reported. It was observed that under all conditions studied the adsorption process was entropically driven. This was contrary to expectations, since at the pH selected ion exchange is expected to dominate. A major driving force for the adsorption of BSA on the anion exchanger was concluded to be the increase in entropy from the release of water due to interactions between hydrophobic regions on the protein and adsorbent. The data further suggest that the conformational entropy change accompanying protein adsorption on the ion exchanger may also be significant.     

Quasi-equilibrated temperature programmed desorption and adsorption: A new method for determination of the isosteric adsorption heat

Temperature programmed desorption and adsorption (TPDA) studied under quasi-equilibrium conditions using typical flow TPD setup equipped with a chromatographic TCD detector has been found a good method of obtaining the equilibrium data characterizing adsorption of n-hexane on high silica HZSM-5 and HY zeolites. The equilibrium control of sorption has been confirmed by linearity of the isosters constructed from the TPDA profiles. For HZSM-5 it was corroborated by very good agreement obtained in fitting the experimental data with the model based on the dual site Langmuir (DSL) adsorption function. The values of the adsorption enthalpy and entropy, either determined from the adsorption isosters or as the fitted model parameters, were close to the literature data. Increase of the isosteric adsorption heat of hexane with coverage was observed for both zeolites (72-90 kJ mol⁻¹ for HZSM-5 and 46-61 kJ mol⁻¹ for HY).     

Adsorption thermodynamic and desorption studies of U(VI) on modified silica gel (SiAPMS-HL)

In this study, the adsorption process was examined by various isotherm models Langmuir, Freundlich and Dubinin–Radushkevich and equilibrium data were successfully described by Langmuir model. Adsorption thermodynamics of uranium (VI) on modified silica gel (SiAPMS-HL) has been studied within a temperature range from 293 to 333 K and the thermodynamic parameters, such as equilibrium constant (K _D), standard free energy changes (ΔG°), standard enthalpy change (ΔH°) and standard entropy change (ΔS°), have been obtained. The desorption studies were conducted in batch system to investigate the kind, concentration and volume of the eluent.