Kinetics and thermodynamics of rebaudioside A adsorption on a strongly acidic cation exchange resin

To explain the mechanism underlying the adsorption of stevia's polar component rebaudioside A in hydrophilic interaction liquid chromatography mode, the characteristics of rebaudioside A adsorption on various resins in an organic‐solvent‐rich system were studied. Among the tested resins, the strongly acidic cation resin FPC11 showed the best adsorption behavior for rebaudioside A. The factors affecting the adsorption kinetics of the resin for rebaudioside A are discussed. The results showed that the pseudo‐second‐order reaction model and intra‐particle diffusion model best described the adsorption kinetics of rebaudioside A on the resin. The adsorption rate was controlled by physical sorption, mainly via electron sharing or electron transfer between the adsorbent and the adsorbate. The adsorption process with multiple stages involved weak initial adsorption behavior. Thermodynamic studies showed that the adsorption of rebaudioside A on the resin was not an ideal monolayer adsorption, but mutual adsorption effects between the adsorbates. The adsorption was a spontaneous, entropy‐increasing endothermic process. The synergistic effect of hydrogen bonding and ion–dipole was a possible driving force.     

Kinetics of uranium adsorption from sulfate medium by a commercial anion exchanger modified with quinoline and silicate

Journal of Radioanalytical and Nuclear Chemistry - Noble gas monitoring system is used to measure the volumetric activity of beta particles due to radioactive noble gases—41Ar, 85Kr and...     

Kinetic studies of uranium(VI) adsorption on a composite ion exchanger

In this paper, we studied the continuous adsorption of uranium on a composite ion exchanger. The experimental study was carried out at optimum conditions of uranium uptake found in the previous study. For these conditions first the adsorption isotherm was determined. This isotherm shows non-linear sorption according to the Langmuir model. Then we investigated uranium adsorption at different time intervals at temperatures of 30°C and 60°C, respectively.     

Kinetics and thermodynamics of the adsorption of some dyestuffs and p-nitrophenol by chitosan and MCM-chitosan from aqueous solution

The effect of initial concentration, temperature, and shaking rate on the adsorption of three dyestuffs [orange II (O-II), crystal violet (CV), and reactive blue 5 (RB5)] and an ideal adsorbate, p-nitrophenol (PNP), by chitosan (Sigma C-3646) and the effect of temperature on the adsorption of O-II and CV by monocarboxymethylated chitosan (MCM-chitosan) were investigated. Kinetic data obtained for the adsorption of each dyestuff and PNP by chitosan and of O-II and CV by MCM-chitosan at different temperatures were applied to the Lagergren equation, and adsorption rate constants (k(ads)) at these temperatures were determined. These rate constants related to the adsorption of O-II and RB5 by chitosan and of O-II by MCM-chitosan were applied to the Arrhenius equation, and activation energies (E(a)) were determined. In addition, the isotherms for adsorption, at different temperatures, of each dyestuff and PNP by chitosan and of O-II and CV by MCM-chitosan were also determined. These isothermal data were applied to linear forms of isotherm equations that they fit, and isotherm constants were calculated. Because the isotherm curves obtained for the adsorption of O-II and CV by chitosan and of CV by MCM-chitosan fit the Langmuir adsorption isotherm, b constants were applied to thermodynamic equations, and thermodynamic parameters (delta G, delta H, and delta S) were calculated. Lastly, chitosan and MCM-chitosan were compared with respect to the ability to take up the dyestuffs and PNP.     

Removal of uranium,cadmium and iron ions from phosphoric acid solution using amberjet 1200 H resin: an experimental,isotherm and kinetic study

Journal of Radioanalytical and Nuclear Chemistry - Amberjet 1200 H resin is an industrial strong acid cation exchanger bearing sulfonic reactive groups that were tested for the removal of uranium,...     

Removal and recovery of uranium from aqueous solution by tea waste

Experiments on the removal and recovery of U(VI) from aqueous solution by tea waste were conducted. The adsorbent was characterized by scanning electron microscope and energy dispersive spectrometer before and after the adsorption treatment. The removal of U(VI) amounts to 86.80?% at optimum pH 6. The adsorption process reaches its equilibrium in 12?h at 308?K, and the kinetic characteristic can be described by the pseudo-second-order kinetic equation. The amount of adsorption increases from 22.92 to 142.21?mg?g^?1 with the decrease of tea waste dosage from 100 to 10?mg for solution with an initial uranium concentration of 50?mg?L^?1. Desorption for the four strippants is higher than 80?%. The equilibrium data are more agreeable with Freundlich isotherm than Langmuir isotherm.     

Hybrid aniline/silica xerogel cation adsorption and thermodynamics of interaction

Aniline groups chemically immobilized on silica through the sol-gel process were employed to extract divalent nickel and manganese from aqueous solutions at room temperature. The maximum adsorption capacity of the xerogel was studied from adsorption isotherms using a batch technique. The isotherms obtained were adjusted following the Langmuir equation. The xerogel adsorbent appears to have better affinity for nickel than manganese. From calorimetric titration, thermodynamic data on cation/nitrogen basic atom interaction in the solid/liquid interface were determined. The enthalpic values, -0.46 +/- 0.02 and -.029 +/- 0.02 kJ mol(-1) for nickel and manganese, respectively, are in agreement with the low availability of the basic nitrogen atom on the aniline group and also the possible steric hindrance of the phenyl group bonded to nitrogen. However, thermodynamics indicated the existence of favorable conditions for such cation-nitrogen interactions.     

Kinetics and thermodynamics of adsorption of congo red on cellulose

Thermodynamics and kinetics of adsorption of congo red (CR) on cellulose are studied at 308–328 K. In the used concentration range of CR, interaction of CR with cellulose is exothermic and CR molecules adsorb chemically on cellulose surface. The effects of contact time, temperature and initial concentration of CR on kinetics of its adsorption on cellulose were investigated. The process proceeds according to the pseudo-second-order equation. Initial adsorption rate of adsorption is first-order in CR and the intraparticle diffusion of CR molecules within cellulose is identified as the main rate-limiting step.      

U(VI) ion adsorption thermodynamics and kinetics from aqueous solution onto raw sodium feldspar and acid-activated sodium feldspar

The raw sodium feldspar (RSF) is activated with the concentrated sulfuric acid solution and the acid activated sodium feldspar (AASF) is obtained. The results obtained from the mercury intrusion method show that the acidification can increase the porosity and the specific surface area. The effects of the initial pH, contact time and ambient temperature on the adsorption of U(VI) ions are investigated in a batch process. The adsorption efficiency amounts to the highest at pH 6 and the adsorption equilibrium is reached in 600 min. The pseudo-second-order model is found to be more suitable for the adsorption process than the pseudo-first-order model and intra-particle model, indicating that the chemical adsorption is the predominant step for the adsorption process. Langmuir model is found to describe the adsorption process better than Freundlich model. This proves that the main form of U(VI) ions attached to RSF and AASF is the monolayer coverage. The thermodynamic parameters prove that the adsorption process is a spontaneous endothermic one. It was also found that acid activated treatment can help increase the adsorption rate and capacity. The results show that RSF and AASF can be used as a novel low cost adsorbent for removal of U(VI) ions from the low concentration aqueous solution.     

Recovery of uranium from uranium refining waste water by using immobilized persimmon tannin

Some attempts were made to examine the practical conditions for uranium recovery from uranium refining waste water. The adsorbent was highly effective in recovering uranium. The uranium adsorption was affected by pH, temperature, and uranium concentration of the uranium refining waste water. The adsorbent also recovered uranium effectively in column system. It aquires better mechanical properties and can be used repeatedly in the uranium adsorption-desorption cycles.     

油页岩飞灰对重金属离子的吸附动力学及热力学

采用批式振荡吸附法研究了燃油页岩电厂循环流化床锅炉飞灰对重金属离子Pb²+、Cu²+、Zn²+、Cd²+的吸附动力学及吸附热力学特性,并提出了吸附机理。结果表明,油页岩飞灰对Pb²+、Cu²+、Zn²+、Cd²+的吸附平衡数据符合Langmuir和Freundlich吸附等温方程,但Freundlich方程能够更好地描述吸附等温线。在油页岩飞灰对重金属离子吸附的初始阶段,拉格朗日准一级动力学方程、准二级动力学方程、Elovich方程、粒子内扩散模型均能很好地反映吸附模式,而整个吸附过程则遵循二级反应动力学方程,其吸附过程是液膜扩散和粒子内扩散共同作用的结果。油页岩飞灰对Pb²+、Cu²+、Zn²+、Cd²+的吸附是吸热反应。     

Removal of uranium from aqueous solution by using activated palm kernel shell carbon: adsorption equilibrium and kinetics

Activated palm kernel shell carbon (APKSC) was used to remove U(VI) from aqueous solutions in a batch system. The adsorption kinetics, isotherms, and effects of various parameters, such as temperature, contact time, solution pH, adsorbent dosage, and initial U(VI) concentration on the U(VI) adsorption process were studied. Equilibrium was reached after 120 min in the range of studied U(VI) concentrations and temperatures. U(VI) uptake was insignificantly affected by temperature, but was highly pH dependent, and the optimum pH for removal was 5.5. U(VI) removal efficiency increased with the increasing adsorbent dosage. U(VI) sorption capacity increased with increasing initial U(VI) concentration; any further increases in initial U(VI) concentration above a certain point caused insignificant changes in U(VI) sorption capacity. Isotherm data could be described by the Langmuir isotherm model with a maximum U(VI) adsorption capacity of 51.81 mg/g. Kinetic data were fitted to pseudo-first-order and pseudo-second-order equations, which suggested that the U(VI) adsorption onto APKSC was better reproduced by the pseudo-second-order model rather than pseudo-first-order model. Our results indicated that APKSC might be used as a cheap adsorbent in the treatment of uranium-containing wastewater.     

Diethylenetriamine functionalized silica gel for adsorption of uranium from aqueous solution and seawater

Journal of Radioanalytical and Nuclear Chemistry - The diethylenetriamine (DETA) organic moiety was anchored covalently on the surface of silica gel to obtain a surface-modified adsorbent...     

Kinetics and mechanism of ion exchange of Fe3+, Cd2+ and Na+/H+ on Lewatite S-100 cation exchanger in aqueous and aqueous-detergent media

Sorption mechanism of Fe (III), Cd (II) and Na (I) on cation exchange resins in H-form was investigated from aqueous and aqueous-detergent media by a modified limited batch technique. The cation exchange studies involved the sorption of metallic ions onto a Lewatite S-100 exchanger. Effects of mesh size of the exchanger, temperature and detergent on the exchange rate have been investigated. The mechanisms of cation exchanges have been determined in the temperature range of 25–65°C. In all cases of the reactions ions, diffusion is found to be the rate determining step in the exchange process. The exchange rate in the exchange process was found to increase with a decrease of particle size and an increase of temperature. However, in case of the influence of detergent, the exchange reactions are dependent on the reaction technique. The effective-diffusion coefficients have been evaluated at three different temperatures. The energy barriers (ΔE_a), entropies of activation (ΔS*), (ΔH*) and (ΔG*) for various sorption systems have also been calculated. The results are discussed in terms of size and valences of the counter ions. No change in the internal structure of Lewatite S-100 is inferred due to the sorption of counter ions.     

Effective adsorption of uranium(VI) from aqueous solution using ethylene-bridged mesoporous silica functionalized with ureido groups

Journal of Radioanalytical and Nuclear Chemistry - Ureido-functionalized ethylene-bridged mesoporous silica (UE-MS) was synthesized by co-condensation method for uranium(VI) uptake. The adsorbents...     

Removal of thorium and uranium from aqueous solution by adsorption on hydrated manganese dioxide

Journal of Radioanalytical and Nuclear Chemistry - The hydrated manganese dioxide (HMO) was synthesized by hydrothermal process using MnSO4 and KMnO4. The adsorption of HMO for Th(IV) and U(VI)...     

腐殖酸自水溶液中吸附亚甲基蓝的热力学与机理研究

腐殖酸是自然界植物残体经腐解后的产物 ,为一种复杂的天然大分子有机质 ,分子内主要含有羰基、羧基、醇羟基、酚羟基等多种活性官能团 ,因此它具有弱酸性、亲水性、吸附性和络合性 ,能够与许多有机、无机物发生相互作用。腐殖酸能作为水处理过程中的吸附剂 ,研究它对水中各类污染物的吸附规律和机理是十分有意义的。赵振国等[1～ 3] 运用吸附过程的ΔＧ 、ΔＨ 、ΔＳ 等热力学函数的变化来探讨吸附机理 ,得出了一些有意义的结论。我们将这一方法应用到水溶液体系中 ,探讨在不同吸附条件下各吸附热力学函数的变化 ,以期对吸附过程有更进一…     

Kinetics and thermodynamics of the sorption of uranium and thorium ions from nitric acid solutions onto a TBP-impregnated sorbent

Summary Kinetics and equilibrium studies on the sorption of uranium and thorium ions were carried out from nitric acid solutions by tri-n-butyl phosphate (TBP) loaded supported sorbent, commercially known as Egy-Sorb, using batch technique. Analysis of the rate data in accordance with three kinetic models revealed that the particle diffusion process was the rate determining mechanism and the sorption process of the metal ions onto impregnated sorbent follows first order reversible kinetics. The values of the first order rate constants, the rate constants of intraparticle transport, and the particle diffusion coefficients for the uranium and thorium ions were determined from the graphical representation of the proposed models. Experimental isotherms of both ions were successfully fit to Langmuir and Freundlich isotherm models over the entire concentration range studied. The effect of temperature on the equilibrium distribution values has been utilized to evaluate the changes in standard thermodynamic quantities.     

Adsorptive removal of uranium from aqueous solution using chitosan-coated attapulgite

Chitosan-coated attapulgite beads were prepared by coating chitosan on naturally and abundantly available attapulgite, and made into spherical beads to adsorb uranium from aqueous solutions. The beads were characterized by SEM, EDS and FT-IR. The characteristics of beads of adsorbing uranium(VI) from aqueous solutions were studied at different conditions of pH, initial uranium concentration, contact time, biomass dosage and temperature. The pseudo-second order rate equation was used to describe the kinetic data, and isotherm data were fitted to Langmuir and Freundlich adsorption models. Thermodynamic parameters (ΔG°, ΔH°, and ΔS°) of the biosorption were also calculated. Thermodynamic parameters of the CAAB, viz., ΔG°(308 K), ΔH°, and ΔS° were determined to be −21.59, 6.29l and 90.51 J/mol K, respectively. The experimental results demonstrate that the beads of chitosan coated onto attapulgite exhibit considerable potential for application in both adsorption and removal of uranium from aqueous solutions.     

Polymer coated cation exchanger in ion chromatography: preparation, properties and applications

Summary Stationary phases synthesized by polymer-coating of silica gel were investigated for the separation of cations by ion chromatography. Two kinds of polymer coating (polystyrene, polyglycidylmethacrylate) with sulphonic acid cation-exchange groups on various silica gels were prepared. These low capacity strong acid cation-exchangers were applied to determine alkali and alkaline earth metal ions in tap and mineral water, and grape juice samples. The IC-results were compared with those of AAS-measurement and of EDTA-titration of alkali metals and of alkaline earth metals, respectively.