Behavior of human serum albumin on strong cation exchange resins: I. Experimental analysis

Experiments with human serum albumin on the strong cation exchange resin Fractogel EMD SE Hicap (M) were carried out. Even though human serum albumin was used at high purity, two peaks in gradient elution experiments occurred. The obtained data can be explained by considering that human serum albumin binds to Fractogel EMD SE Hicap (M) in two different binding conformations: the protein adsorbs instantaneously in the first conformation and then changes into the second one with a kinetic limitation. The two-peak behavior of human serum albumin was analyzed in detail, especially at various gradient lengths, concentrations and temperatures. Breakthrough curves were performed at four modifier concentrations and three velocities. The characteristic adsorption behavior, found for gradient experiments, was confirmed by the breakthrough curves. The two-peak elution pattern of human serum albumin was also found for other strong cation exchange resins, but not for weak cation exchange resins. It is concluded that the described behavior is peculiar for the interaction of human serum albumin with the strong cation exchange ligand of the resin.     

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 and mechanism of aqueous oxidation of H2S by Fe+3

The reaction kinetics of aqueous oxidation of H₂S by Fe⁺³ is investigated at 25°C by spectrophotometric method. The study conducted at various reactant concentrations and pH revealed that the reaction proceeds according to complex‐series reactions involving polysulfides as intermediates. The reaction of each step is first order with respect to Fe⁺³ and hydrogen sulfide or polysulfide. A mechanism is proposed, involving sulfido and polysulfido radicals. © 1999 John Wiley & Sons, Inc. Int J Chem Kinet 31: 331–335, 1999     

强酸性阳离子交换树脂催化合成醋酸正丁酯的动力学研究

以强酸性阳离子交换树脂Amberlyst 15作为催化剂,研究了醋酸与正丁醇合成醋酸正丁酯的反应动力学;考察了搅拌速度、催化剂粒径、温度、催化剂用量,以及酸醇物质的量之比对醋酸转化率的影响;建立了拟均相动力学模型,对实验数据进行了拟合,并估算了相应的动力学参数.结果表明,由拟均相动力学模型得到的计算值与实验值吻合较好.     

Calorimetric determination of H+/M+ (M=Na,K) ion exchange in γ-titanium phosphate

H⁺/M⁺ (M=Na, K) ion exchange on -titanium phosphate (-TiP) at 25°C and under static conditions has been studied. Titration and hydrolysis curves and the exchange isotherms were determined. The substitution was followed by X-ray diffraction. Direct calorimetric measurements were carried out at different degrees of conversion and the variation of the exchange enthalpy and the hydrolysis enthalpy of -TiP were obtained. The results are compared to the values of H° obtained in previous works from titration data.     

Studies on ion exchange equilibria and kinetics: V. UO 2 2+ −Na+−H+ ternary cation exchange kinetics

The kinetics of particle-diffusion controlled ion exchange in the ternary system of cations UO ₂ ²⁺ –Na⁺–H⁺–001×7 strong acidic resin has been studied. In the [R–H⁺]/(Na⁺+UO ₂ ²⁺ ) system, the change of the amount of Na⁺ in the resin phase with time showed a high peak. In the [R–Na⁺]/(H⁺+UO ₂ ²⁺ ) system, the change of the amount of H⁺ in the resin phase with time also showed a high peak. In the [R₂–UO ₂ ²⁺ ]/(H⁺+Na⁺) system, the change of amount of H⁺ in the resin phase with time showed merely a small peak. This kinetic character of the ternary ion exchange system in the finite solution volume has been analyzed according to the Nerst-Planck equation, and on the whole, the trend of the experimental results is consistent with the resulting numerical solution of the set of Nerst-Planck equations.     

Colorimetric detection of Fe3+/2+ and fluorescent detection of Al3+ in aqueous media: applications and DFT calculations

Abstract

A new multifunctional colorimetric and fluorescent chemosensor 1 for Fe^3+/2+ and Al³⁺ has been synthesized in the one-step procedure. The sensor 1 detected both Fe²⁺ and Fe³⁺ through the color change from yellow to brown and Al³⁺ via turn-on fluorescence. The binding stoichiometries of sensor 1 with Fe^3+/2+ and Al³⁺ were proposed to be 1:1 with the analyses of ESI-mass and Job plot. Importantly, the detection limits of 1 for Fe^3+/2+ (2.11 and 2.70 μM) and Al³⁺ (3.44 μM) were lower than the EPA guideline (5.37 μM) for Fe^3+/2+ and WHO guideline (7.41 μM) for Al³⁺. Compound 1 was used to quantify ferric species (Fe³⁺) in real samples. Moreover, the sensing processes for Fe^3+/2+ and Al³⁺ were proposed with the spectroscopic studies and theoretical calculations.     

SiO2@松香基阳离子交换树脂对水中微量Cd吸附

以硅胶为核,马来海松酸丙烯酸乙二醇酯和甲基丙烯酸为功能单体,采用涂覆悬浮聚合法合成了核壳型SiO₂@松香基阳离子交换树脂(SiO₂@RCER),研究了其对水中微量Cd²⁺的静态吸附性能。结果表明,在Cd²⁺溶液浓度为0.5 mg·L^-1,pH=6.0,温度为303 K,吸附剂用量为10 g·L^-1时,Cd²⁺去除率可达到100%;SiO₂@RCER对Cd²⁺的吸附符合准二级动力学方程以及Langmuir吸附等温线,表明吸附过程为单分子层化学吸附。吸附前后材料的XPS图谱表明:SiO₂@RCER对Cd²⁺吸附主要涉及Na⁺以及溶液中的Cd²⁺的阳离子交换。该吸附剂在对Cd²⁺、Pb²⁺浓度超标的矿区废水吸附处理后,高毒重金属浓度均达到国家生活饮用水水源水质一级标准(CJ3020-93),其他离子浓度也有所降低。     

Facile synthesis,characterization and application of magnetic Fe3O4-coir pith composites for the removal of methyl violet from aqueous solution: Kinetics,isotherm, thermodynamics and parametric optimization

Dyes are commonly used in coloring clothes; in fertilizers, as anti-freezers, as detergents and so on. The use of such dyes has carcinogenic and genotoxic effects. These dyes require proper removal from the environment. Subsequently, a green and low-cost approach promises to adhere to sustainability of the environment while maximum removal of these toxic dyes. The present study describes removal of methyl violet (MV) dye by adsorption process magnetically separable Fe₃O₄-coir pith composites. The study was evaluated in batch system taking the optimum conditions as: pH: 7, contact time: 12 h, stirring speed: 200 rpm, concentration of dye: 100 mg/L, adsorbent weight: 3 g/L, temp.: 308 K. The central composite design approach of response surface methodology in design-expert software showed maximum removal efficiency (>98%) for optimal parameters. The experimental equilibrium data fitted reasonably well to Langmuir isotherm model. ANOVA analysis along with Fisher's statistical test was also performed to validate the model. The predicted model was at par with the experimental values with adjusted R² of 0.9914. A thorough investigation of kinetic ($R_{\text{Pseudo second order}}^2$ = 0.99; $R_{\text{Pseudo second order}}^2=0.97;R_{\text{intra}?\text{particle diffusion}}^2=0.98)$, thermodynamic, adsorption isotherm $(R_{\text{Langmuir isotherm}}^2=0.997$ $R_{\text{Freundlich isotherm}}^2=0.99$ and eco-toxicological characteristics were performed for proper evaluations of the properties as well as sustainability of the adsorbent material. The whole research indicated encouraging potential of the developed material for adsorption, reusability and sustainability in applications for industrial scale wastewater treatment.     

Comparative of the removal of Pb2+, Cd2+ and Ni2+ by nano crystallite hydroxyapatite from aqueous solutions: Adsorption isotherm study

Release of heavy metal onto the water and soil as a result of agricultural and industrial activities may pose a serious threat to the environment. In this study, the adsorption behavior of nano hydroxyapatite with respect to Pb²⁺, Cd²⁺ and Ni²⁺ has been studied in order to consider its application to purity metal finishing wastewater. The batch method has been employed, using metal concentrations in solution ranging from 100 to 400 mg/L. The uptake capacity and distribution coefficients (K_d) were determined for the adsorption system as a function of sorbate concentration. The Langmuir, Freundlich, and Dubinin–Kaganer–Radushkevich (DKR) isotherms applied for sorption studies showed that the amount of metal sorbed on nano hydroxyapatite. It was found that the adsorption phenomena depend on charge density and hydrated ion diameter. According to the equilibrium studies, the selectivity sequence can be given as Pb²⁺ > Cd²⁺ > Ni²⁺. These results show that nano hydroxyapatite holds great potential to remove cationic heavy metal species from industrial wastewater.     

Remove of Heavy Metals(Cu2+, Pb2+, Zn2+ and Cd2+) in Water Through Modified Diatomite

At present, heavy metal pollution has become a major environmental problem, influencing the survival of human and other creatures. Developing heavy metal ion adsorbents, which are environment friendly, of low cost and good performance is one of the effective means to solve heavy metal pollution. Rich low-grade diatomite mineral, as raw material, was modified with calcium carbonate to improve the adsorption properties of diatomite for heavy metal ions. The effects of dosage(m), pH, adsorbing time(t), temperature(T) and concentration of adsorbent(c) on the removal rate of heavy metal ions(Cu²⁺, Pb²⁺, Zn²⁺ and Cd²⁺) were studied. The results show that under the suitable conditions, T=15 ℃, c=1.5 mmol/L, m=10 g/L, t=60 min, in a weak acid environment, the removal effect of the four kinds of metal ions by modified diatomite is the best.     

绿茶对水溶液中Pb2+和Cd2+吸附性能初步研究

研究了绿茶对溶液中Pb2 和Cd2 离子的吸附和解吸性质。考察了pH、温度、吸附时间对绿茶吸附性能的影响,得到吸附动力学曲线和吸附等温线。结果表明,茶叶在pH为4~6的弱酸性范围内对两种金属离子的吸附效果最佳,在30℃时,茶叶对Pb2 和Cd2 的饱和吸附量分别为46.66 mg/g和33.29mg/g,吸附符合Langmuir吸附等温方程,并对吸附机理进行了初步的探讨。对解吸条件研究发现,用0.1 mol/L HCl和EDTA作为解吸剂,对Pb2 和Cd2 的解吸效果较好,解吸率达80%以上,可有效回收重金属Pb2 和Cd2 。     

Studies on ion exchange equilibria and kinetics VI. Prediction of ion exchange equilibria of UO 2 2+ −Na+−H+ ternary system

Experimental data are reported for the ion exchange equilibria of the binary systems UO ₂ ²⁺ –H⁺, UO ₂ ²⁺ –Na⁺ and Na⁺–H⁺, and of the ternary system UO ₂ ²⁺ –Na⁺–H⁺ on a strong acid cation exchange resin 001X7 at 25 °C. It is found that the equilibria for any pairs of ions are essentially the same in binary and ternary mixtures and that the prediction method proposed by our laboratory for SO ₂ ^2– –Cl^––NO ₃ ^– -201X7 strong base anion exchange resin system is also applicable to the ternary system studied in this paper. The predictions of the ternary system UO ₂ ²⁺ –Na⁺–H⁺ based solely on the binary data without using resin phase activity coefficients are consistent with the experimental data.     

Novel naphthalene-based fluorescent chemosensors for Cu2+ and Fe3+ in aqueous media

Three novel compounds bearing 2,7-dihydroxylnaphthalene capable of detecting Cu²⁺ or Fe³⁺ have been synthesised based on photoinduced electron transfer. The ability of these compounds for complex transition metal ions has been studied, and complex stoichiometry for Cu²⁺ and Fe³⁺ complex has been determined in the Tris–HCl (0.01 M DMSO/H₂O (v/v) 1:1, buffer, pH 7.4) solution system by fluorescence titration experiments. These chemosensors form a 1:1 complex with Cu²⁺ or Fe³⁺ and show a fluorescent quenching with a binding constant of (4.46 ± 0.29) × 10³ and (8.04 ± 0.26) × 10⁴, respectively.     

Calorimetric determination of H+/M+ (M = Li,Cs) ion exchange inγ-titanium hydrogen phosphate

H⁺/M⁺ (M = Li, Cs) ion exchange in-titanium phosphate (-TIP) at 25°C and under static conditions has been studied. Titration and hydrolysis curves and the exchange isotherms were determined. The substitution was followed by X-ray diffraction. Direct calorimetric measurements were carried out at different degrees of conversion and the variation of the exchange enthalpy was obtained. The shape of the calorimetric curves is discussed. The results are compared to the values of H ⁰ obtained from titration data.     

Remediation of Cd2+ in aqueous systems by alkali-modified (Ca) biochar and quantitative analysis of its mechanism

Co-pyrolysis of straw and Ca(OH)₂ is a feasible modification method to improve the adsorption capacity of biochar for Cd. However, few studies have quantitatively analyzed the contribution of different adsorption mechanisms of alkali-modified biochar. In this study, the alkali-modified (Ca) biochar were prepared by co-pyrolyzing lime (Ca(OH)₂) and soybean straw (SBB) or rape straw (RSB) at 450 °C. The adsorption mechanism was investigated by a series of experiments and was provided by quantitative analysis. The maximum adsorption capacities of Cd²⁺ by Ca-SBB and Ca-RSB were calculated to be 78.49 mg g^?1 and 49.96 mg g^?1, which were 1.56 and 1.48 times higher than SBB (50.40 mg g^?1) and RSB (33.79 mg g^?1), respectively. Compared with the original biochar (SBB, RSB), alkali-modified biochar (Ca-SBB and Ca-RSB) were found to have faster adsorption kinetics and lower desorption efficiencies. The mechanism study indicated that Ca(OH)₂ modification effectively enhanced the contribution of ion exchange and decreased the contribution of functional groups complexation. After Ca(OH)₂ modification, precipitation and ion exchange mechanisms dominated Cd^2 + absorption on Ca-SBB, accounting for 49.85% and 34.94% of the total adsorption, respectively. Similarily ion exchange and precipitation were the main adsorption mechanism on Ca-RSB, accounting however for 61.91% and 18.47% of total adsorption, respectively. These results suggested that alkali-modified biochar has great potential to adsorp cadmium in wastewater.     

Separation of strontium from simulated waste in K2SO4/Nitrate medium containing Sr2+, Eu3+, Ce3+, Pd2+, Rh3+, Ru3+, UO 2 2+ , Fe3+, Cr3+, Ni2+, Al3+, Ca2+ and Cs+, by strongly basic anion exchanger

In this work Strontium was separated selectively form, Pd²⁺, Ni²⁺ and Ca³⁺ using anionic resins of Amberlite type IRA-900 and IRA-410 from nitrate medium. The Separation of strontium by strongly basic anion exchangers IRA-410 and IRA-900 from simulated waste containing, Sr²⁺, Eu³⁺, Ce³⁺, Pd²⁺, Rh³⁺, Ru³⁺, VO₂ ²⁺, Fe³⁺, Cr³⁺, Ni²⁺, Al³⁺, Ca²⁺, and Cs⁺, in K₂SO₄/nitrate medium which adsorbed as strontium sulphate complex was achieved through ligand- ligan exchange. The elution of strontium carried out via “loading” the column with a solution of 0.03N EDTA in presence of 0.1N NaNO₃ at pH7 where Sr²⁺ has low K_d value. An inductively Coubled Plasma — Optical Emission Spectrometry (ICP — OES) of ARL type model 3520, was used for elemental analysis.     

酸性溶液中Fe2+ /Fe3+相互转换对电极还原行为的影响

采用线性扫描伏安法和循环伏安法研究了含有Cl^-、SO₄^2-的酸性溶液中Fe²⁺/Fe³⁺相互转换对电极反应和Fe³⁺还原过程的影响. 结果表明: [Fe]_T=1 mol·L-1条件下,溶液中Fe³⁺/Fe²⁺的还原析出过程经过两个阶段：(1) E=0.35 V左右Fe³⁺还原成Fe²⁺过程; (2) E=-0.3 V之后H+的还原同时Fe²⁺离子与OH^-相结合生产Fe(OH)₂; Fe³⁺/Fe²⁺的相互转化主要影响Fe³⁺的第一还原阶段的还原峰电流和峰电位. |ipa/ipc|值随c(Fe³⁺ )/c(Fe²⁺ )增大而增大,且扫描速度慢时影响大,扫描速度快时影响小; 0.50 mol·L^-1 Fe²⁺+0.50 mol·L^-1 Fe³⁺时,随扫描速率的变化|ipa/ipc|值变化最小(|i_pa/i_pc|≈1.20). 同时,c(Fe³⁺ )/c(Fe²⁺ )也影响平衡电位,平衡电位随c(Fe³⁺ )/c(Fe²⁺ )增大而正移,电位从E₁=0.501 V升至E₅=0.565 V.