An excellent arsenic(V) sorption behavior of p-tert-butylcalix[8]areneoctamide impregnated resin

The present article describes the arsenic(V) extraction behavior of p-tert-butylcalix[8]areneoctamide (3) and of a resin (4) impregnated with 3. Liquid–liquid and solid–liquid (column sorption) extraction studies were carried out to optimize various experimental parameters such as pH, extraction effeciency and column stability. Thermodynamic studies based upon Temkin and Flory-Hugins models reveal that the sorption was spontaneous and exothermic. The values of correlation coefficients (R2) show that Langmuir and Freundlich isotherm models are best fit to describe the sorption equilibrium. Application of 4 to real samples indicates a slight decrease (5-7%) in extraction efficiency of 4 because of high concentration of total dissolved salts (TDS). It is deduced that 4 is highly effective for the removal of arsenic(V) at a wide range of pH and attains a maximum value, i.e. 99% at pH 4. The impregnated resin is easy to synthesize from cheap materials. It is more efficient and easily regenerable as compared to already reported resins.     

Thermodynamic studies of Ni(II) adsorption onto bentonite from aqueous solution

The adsorption behavior of Ni(II) onto bentonite was studied as a function of temperature under optimized conditions of shaking time, amount of adsorbent, pH, and concentration of the adsorbate. Thermodynamic parameters such as ΔH^°, ΔS^°, and ΔG^° were calculated from the slope and intercept of the linear plot of lgK_D against 1/T. Analysis of adsorption results obtained at T=(298, 303, 313, and 323) K showed that the adsorption pattern on bentonite followed the Langmuir, Freundlich, and D-R isotherms. A flame atomic absorption spectrophotometer was used for measuring the concentration of Ni(II).     

EFFECT OF HYPERCROSSLINKED RESINS SURFACE CHEMISTRY ON THE ADSORPTION OF PHENOL FROM AQUEOUS SOLUTION

Two hypercrosslinked resins with similar physical characters but different surface chemistry were synthesized and used to remove phenol from aqueous solutions. The FTIR spectra, elemental analysis and the Boehm titration were used to characterize the chemical properties of the resins. The adsorption experiments were carried out using the bottle-point technique, and the effects of the surface chemistry on the adsorption were discussed. The adsorption data fit well with the Freundlich model, indicating the heterogeneity of the resins surface. It could be seen from the experimental results that the adsorption capacity increased with the increase in the total surface concentration of oxygen-containing groups. The pH dependence and the effects of ionic strength were also discussed. The kinetic adsorption data fit well with the pseudo-second order model, and the results showed that the surface oxygen-containing groups have little effect on the adsorption rate.     

Thermodynamic quantities of adsorption described by Freundlich isotherm

Thermodynamic analysis of the Freundlich adsorption isotherm was performed. Equations describing the thermodynamic characteristics of adsorption as a function of the adsorbed quantity are presented, and relationships between the excess differential and average molar thermodynamic adsorption quantities were obtained. It was shown that the thermodynamic approach does not contradict the molecular statistical theory and provides more general equations. A model of adsorption described by the Freundlich isotherm is discussed. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 175–177, January, 2000.     

Non-Linear Binding and the Diffusion–Migration Test

In this paper we investigate the non-linear binding effects upon the diffusion–migration test. For the diffusion test we derive the conditions required for the non-linear binding isotherm to produce an actual penetration front. When more than two ion species are present we show that the diffusion coefficient associated with a particular ion cannot be extracted from the diffusion test on account of multi-species electrical effects. In the migration test where an external electrical field is applied to the sample, we give the conditions required for the propagation of a stable travelling wave. In addition new explicit expressions of the time-lag are obtained for both tests, allowing the determination of the properties of the unknown binding isotherm whatever its physical nature. Throughout the paper the results and the method are illustrated by the diffusion of the Cl^– ion within cement-based materials, using experimental data extracted from literature. The theoretical predictions compare well to these experimental data.     

改性红壤对水中磷的去除

用三氯化铁改性的红壤作为吸附剂对水中的磷进行吸附,考察了吸附剂吸附过程中时间和温度对吸附的影响。实验结果表明,改性红壤对磷的吸附是一个准二级反应过程;整个吸附过程符合Freundlich等温线,25℃时对磷的最大吸附容量为428.4mg.g-1。     

Synthesis and Micromechanistic Studies of Sensitized Bentonite for Methyl Orange and Rhodamine-B Adsorption from Wastewater: Experimental and DFT-Based Analysis

This work reports the formation of a novel adsorbent, prepared by activating bentonite with cinnamic acid, which is highly efficient to remove dyes from wastewater. The adsorption efficiency of the cinnamic acid activated bentonite was compared with unmodified bentonite by removing methyl orange and rhodamine-B from polluted water. The characterization was performed through X-ray diffraction (XRD) Fourier transform infrared (FTIR) and scanning electron microscopy (SEM). The results indicated that acidic pH and low temperature were more suitable for the selected dyes adsorption. The analysis of the data was done by the Langmuir and Freundlich isotherms; the Freundlich isotherm showed more suitability for the equilibrium data. The data were further analyzed by pseudo-first and pseudo-second-order models to study adsorption kinetics. The results showed that methyl orange and rhodamine-B adsorption obeyed pseudo-order kinetics. The results obtained from this research suggested that acid activation of bentonite with cinnamic acid increased the surface area of the clay and hence enhanced its adsorption efficiency. The maximum adsorption efficiency for the removal of methyl orange and rhodamine-B was up to 99.3 mg g⁻¹ and 44.7 mg g⁻¹, respectively, at 25 °C. This research provides an economical modification technique of bentonite, which makes it cost-effective and a good adsorbent for wastewater treatment.