Isotherm of Strontium Sorption on Clay

Sorption of strontium(II) with soil components from model solutions was studied. Limiting sorption of strontium ions, their landing site area, and Langmuir constants were determined.     

Sorption of Radiocobalt on Bentonite and Kaolinite

The factors affecting the sorption of radiocobalt by bentonite and kaolinite were studied with the aim to assess important factors which should be included in modelling radiocobalt migration in soils and waters. The distribution coefficients of radiocobalt sorption on bentonite and kaolinite from aqueous solutions were determined by using the batch method, and it was found that they were insensitive to the loading, the initial pH, the ionic strength, the humic substance and the sorption direction. Thus, the sorption characteristics of radiocobalt on bentonite and kaolinite facilitated the mathematical modelling of radiocobalt migration. In addition, the sorption kinetics and the sorption mechanism of radiocobalt on bentonite and kaolinite were also examined.     

Sorption Characteristics of Radioeuropium on Bentonite and Kaolinite

The factors affecting the sorption of radioeuropium(III) by bentonite and kaolinite were studied with the aim to assess the important factors which should be included in modeling of radioeuropium(III) migration in soils and sediments. Europium(III) is an analogue of trivalent actinides. The distribution coefficients of radioeuropium for sorption on bentonite and kaolinite from aqueous solutions were determined by using the batch method, and it was found that they were sensitive to the loading, the pH, the humic substance and the sorption direction. Thus, these sorption characteristics of radioeuropium on bentonite and kaolinite were found to be different from those of radiocobalt¹, and the mathematical modeling of trivalent lanthanides and actinides migration will be more complicated than that of radiocobalt. It is improbable that the migration modeling with a constant distribution coefficient will be successful in the case of trivalent lanthanides and actinides.     

Sorption of Cesium and Strontium on Hanford Soil

The sorption behavior of strontium and cesium on soil collected from the US Department of Energy Hanford site, Washington State, was investigated under batch experiments. The sorption ratio was determined as a function of time and radionuclide concentration. All experiments were performed at 25 °C under argon atmosphere. Cesium and strontium were extensively sorbed on the soil. The sorption data were well described by a Freundlich isotherm.     

双阳离子复合改性膨润土的吸附性能与构效关系

膨润土是一种以蒙脱石为主要成分的天然吸附材料. 本文用2-巯基乙胺盐酸盐(MEA)与十六烷基三甲基溴化铵(HDTMA)复合改性内蒙钙基膨润土(IMB), 制得具有特殊结构与性能的吸附材料MEA-HDTMA-IMB. X射线衍射(XRD)、红外光谱(FT-IR)、热分析(TG-DTA)及比表面积(N2-BET)等结构表征表明: 复合改性膨润土的比表面积和层间距显著增大. 吸附研究发现: MEA-HDTMA-IMB能同时有效吸附混合水溶液中的有机物对硝基苯酚和重金属铜. 复合改性膨润土对水中有机物的吸附机理以分配作用为主, 其吸附能力强于用季铵盐阳离子单一改性的有机膨润土HDTMA-IMB; 对水中重金属的吸附主要为络合反应, 其吸附性能与用巯基铵阳离子单一改性的膨润土MEA-IMB相当.     

Exchange Isotherm of Strontium(II) and Iron(III) Ions on Clay

Joint sorption of Sr^{2 +} and Fe^{3 +} ions on blue Cambrian clay was studied. A relationship between the isotherm of ideal ion exchange and the Langmuir sorption isotherm was revealed. The apparent constant and Gibbs energy of exchange of Sr^{2 +} and Fe^{3 +} ions on blue Cambrian clay were calculated.     

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.     

The Influence of Heat Pre-Treatment on the Sorption of Water Vapour on Bentonite

Sorption isotherms of water vapour on bentonite from the Rokle locality of northwest Bohemia in the Czech Republic were measured and analysed after being treated with heat. Protracted sorption measurements were performed at 30∘C in the range of water vapour relative pressures between 0.12 and 0.94. Prior to sorption measurements, the bentonite samples were exposed to flowing dry nitrogen for 18 hours at 115, 220 and 300∘C. Compared to the sample heated at 115∘C, the bentonite samples that were treated at 220 and 300∘C exhibited a decrease in water vapour sorption capacity. This decrease in sorption capacity was accompanied by structural changes that were confirmed by X-ray diffraction analysis.     

Poisson-Boltzmann与Donnan模型计算压实膨润土孔隙水与外部溶液间离子平衡的差异性比较

压实膨润土孔隙水与外部溶液之间的离子平衡是影响离子在压实膨润土中扩散的影响因素之一, 表征这一平衡的离子平衡系数可用压实膨润土的宏观属性参数通过Donnan 模型计算得到. 通过对膨润土主体矿物蒙脱石的TOT层结构单元进行简化, 构建了一个压实膨润土的单类孔隙结构模型, 辅以一个尺度变量H, 用Poisson-Boltzmann (PB)理论模型计算上述离子平衡系数. 对比计算结果, 发现PB模型计算的离子平衡系数总是大于Donnan模型的结果, 而参数H是联系这两种模型之间的桥梁. 通过对参数H取极限H→0, 实现了从PB模型到Donnan 模型的数学变换, 并从机理上讨论了两种模型之间的差异及其在实际扩散问题中的应用.分析表明PB模型更符合离子在压实膨润土中扩散的实际情况, 更适于处理实际扩散问题.     

Kinetic Models of Batch Sorption in a Limited Volume

Russian Journal of Physical Chemistry A - The batch sorption kinetics described by a nonlinear equation with a variable equilibrium parameter for the interface was considered. It was shown that a...     

Nitric Acid Procedure for Production of Powdered Cellulose II Forms with Various Morphologies and Comparison of Their Structural and Sorption Characteristics

A two-stage procedure for production of powdered cellulose II, based on polymorphous transformation of native cellulose I and hydrolytic dispersion of the fiber with a single reagent, nitric acid, was proposed.     

Determination of Parameter Uncertainty for Quantitative Analysis of Shaddock Peel Pectin using Linear and Nonlinear Near-infrared Spectroscopic Models

Fourier transform near-infrared spectrometry has been used in combination with multivariate chemometric methods for wide applications in agriculture and food analysis. In this paper, we used linear partial least square and nonlinear least square support vector machine regression methods to establish calibration models for Fourier transform near-infrared spectrometric determination of pectin in shaddock peel samples. In particular, the tunable kernel parameters of the linear and nonlinear models were set changing in a moderate range and were optimally selected in conjunction with a Savitzky–Golay smoother. The smoothing parameters and the linear/nonlinear modeling parameters were combined for simultaneous optimization. To investigate the robustness of calibration models, parameter uncertainty were estimated in a direct way for the optimal linear and nonlinear models. Our results show that the nonlinear least square support vector machine method gives more accurate predictive results and is substantially more robust compared to the spectral noise when compared with the linear partial least square regression. Furthermore, the optimized least square support vector machine model was evaluated by the randomly selected test samples and the model test effect was much satisfactory. We anticipate that these linear and nonlinear methods and the methodology of determination of model parameter uncertainty will be applied to other analytes in the fields of near-infrared or Fourier transform near-infrared spectroscopy.     

Sorption of Strontium Ions on Potassium-Titanate Nanoparticles of Various Morphology Obtained under Hydrothermal Conditions

The results of the study of the interaction of an aqueous solution of strontium nitrate with potas-sium-titanate nanoparticles of different morphology obtained by the hydrothermal method are reported. Comparative analysis showed the advantage of nanotubes as sorbents over nanolayers and nanowires. As can be seen from the experiment conducted with nanotubes containing aluminum, an amount of strontium sorbed from the solution rises with increasing temperature: at 50°C the absorption by the tubular matrix was ≈ 0.76 × 10^?3 mol g^?1, and at 80°C that was ≈ 2.02 × 10^?3 mol g^?1. Nanotube samples doped with magnesium had the best sorption characteristics: After 5 h of keeping in a solution at 80°С, the content of strontium in them was ≈3.65 × 10^?3 mol g^?1. The results show the promise of using potassium titanate nanoparticles to extract strontium from aqueous solutions.

     

Equation for the Dynamics of First-Order Irreversible Sorption,Based on the Adsorption of Anthocyanins by Bentonite Clay

Russian Journal of Physical Chemistry A - A new equation is proposed to replace the popular Lagergren equation describing the irreversible sorption of substances by a first-order reaction kinetics....     

Fabrication and Characterization of Sol-Gel Derived Potassium Sodium Strontium Barium Niobate

Potassium sodium strontium barium niobate (K_0.2Na_0.2Sr_0.48Ba_0.32Nb₂O₆, KNSBN) powder and thin films dip coated onto Si(100) substrates have been prepared by sol-gel route. The thermal evolution of these sol-gel derived KNSBN was studied by differential thermal analysis (DTA) and thermogravimetry (TG). Their structural changes at different annealing temperatures were examined by X-ray diffraction (XRD) and Raman spectroscopy. Our results suggest that the KNSBN tetragonal tungsten bronze (TTB) phase is formed via an intermediate orthorhombic phase. Pure TTB phase KNSBN was obtained at annealing temperatures of 1200°C and 600°C for powder and films respectively.     

Kinetics and Equilibrium Models for Sorption of Cu(II) onto a Novel Manganese Nano-adsorbent

The studies of kinetics and equilibrium sorption of Cu(II) were undertaken using nanoscale zerovalent manganese (nZVMn) synthesized by chemical reduction in a single pot system. nZVMn was characterized using scanning electron microscopy, energy dispersive x-ray, and surface area determined by Brunauer–Emmett–Teller. The effect of pH, contact time, adsorbent dose, agitation speed, initial Cu(II) concentrations, temperature, and ionic strength on the sorption of Cu(II) onto nZVMn were investigated in a batch system. The kinetic data followed pseudo-second-order. The mechanism was governed by pore diffusion. The equilibrium sorption data were tested by Freundlich, Langmuir, Temkin, Dubinin–Kaganer–Raduskevich, and Halsey isotherm models. The Langmuir monolayer adsorption capacity (Q_max = 181.818 mg/g) is much greater compared to other nano-adsorbents used in sorption of Cu(II). The thermodynamic parameters (ΔH⁰, ΔS⁰, ΔG⁰) revealed a feasible, spontaneous, and endothermic adsorption process. nZVMn has a great potential for effective removal of copper (II) in aqueous solution.     

The Sorption of Cesium and Strontium Ions onto Red-Clay from Sivrihisar-Eskisehir (Turkey)

The sorption of Cs and Sr ions fromaqueous solutions (concentration range: 20–400 mg/L)by red-clay from Sivrihisar-Eskisehir (Turkey) hasbeen investigated using EDXRF spectrometry. The XRDpattern of the sample indicates that it containsmontmorillonite, illite, albite, chlorite and quartz.The results indicate the presence of correlationsbetween sorbed Cs ions and desorbed Na and K ions andsorbed Sr ions and desorbed Mg and Ca ions. Sorptionprocesses are found to show a Freundlich-typebehaviour. The Dubinin–Radushkevich (D–R) isotherm hasbeen applied to the sorption data and the parametersof the D–R equation were calculated.     

Synthesis and Sorption Behaviour of Some Radioactive Nuclides on Sodium Titanate as Cation Exchanger

Crystalline (Na₄TiO₄·0.32H₂O) and amorphous (Na₂TiO₃·1.45H₂O) forms of sodium titanate were prepared by fusion reaction of TiO₂ and Na₂CO₃ at 1100°C in molar ratios of 2:1 and 1:2, respectively. The prepared products were characterized using IR, DTA-TG, X-ray and elemental analyses. Kinetic studies of the order of reaction (n) and activation energy (E _a) for crystallization transformation step (for crystalline sodium titanate only) have been determined from DTA thermogram and their values were found to be 0.87 (univalent order) and 3.97 kJ mol^–1, respectively. Ion exchange capacities and some distribution studies were carried out at different conditions in the presence of some complexing agents (EDTA, boric and citric acids) and the results showed that the capacities of the crystalline form are always less than the amorphous one.