Application of kinetic,isotherm and thermodynamic models for the adsorption of Co(II) ions on polyaniline/polypyrrole copolymer nanofibers from aqueous solution

The aim of this research is to investigate sorption characteristics of polyaniline/polypyrrole copolymer nanofibers (PANI/PPy copolymer nanofibers) for the removal of Co(II) ions from aqueous solution. The adsorbent is characterized using FE-SEM, TEM, FTIR, TGA, DSC and BET surface area. The sorption of Co(II) ions by batch method is applied and the optimum conditions are investigated. In optimum condition, removal efficiency was 99.68% for 100 mg L⁻¹ Co(II) solution. It is found that temperature has a positive effect on the removal efficiency. It can be concluded that PANI/PPy copolymer nanofibers are potentially able to removal of Co(II) ions from aqueous solutions.     

Equilibrium,kinetics and breakthrough studies for adsorption of hydrogen fluoride on sodium fluoride

In this study, adsorption of hydrogen fluoride on sodium fluoride adsorbent is investigated through an experimental and theoretical study. This process is very important in a section of a total process of producing and making pure fluorine gas in uranium conversion industry. For applying the section of experimental study, experimental sample of differential adsorbed bed was designed and manufactured with necessary side equipment and the required experiments were applied in 22 and 54 °C. By the use of experimental results, Isotherm curve of hydrogen fluoride adsorption on sodium fluoride adsorbent was obtained which is the main tool for designing of adsorption bed. By considering the experimental results and adsorption models applied in this study, it can be concluded that equilibrium data were well represented by a langmuir isotherm equation with maximum adsorption capacities of 1.908 and 0.750 g HF/g NaF in 22 and 54 °C.     

Biosorption characteristics of Bacillus sp. ATS-2 immobilized in silica gel for removal of Pb(II)

The bacterial strain Bacillus sp. ATS-2 isolated from Pb(II) polluted soil was immobilized with a silica matrix and Pb(II) biosorption properties of immobilized biosorbent were examined. Optimum biosorption conditions were investigated in the fixed bed column with the variation in the parameters of pH, bed length, flow rate and influent concentration. The Pb(II) biosorption equilibrium was attained within 60 min and the maximum biosorption yield for silica gel immobilized Bacillus sp. ATS-2 was determined as 91.73% at pH 4.0. The higher biosorption yields were observed at flow rates of 60 and 180 ml h(-1). The optimum bed length for the column was found as 10 cm. Data obtained from batch studies were evaluated by Freundlich, Langmuir and Dubinin-Radushkevich (D-R) isotherm models. The maximum monolayer capacity of Bacillus sp. ATS-2 for Pb(II) was 2.36 x 10(-5) mol g(-1). The involvement of the functional groups on the surface of immobilized cells in biosorption process was also evaluated by FTIR spectral analysis.     

Adsorption of anionic dyes on poly(epicholorohydrin dimethylamine) modified bentonite in single and mixed dye solutions

The performance of poly(epicholorohydrin dimethylamine) modified bentonite (EPIDMA/bentonite) as an adsorbent to remove anionic dyes, namely Direct Fast Scarlet, Eosin Y and Reactive Violet K-3R, was investigated in single, binary and ternary dye systems. In adsorption experiments in single dye solutions, the adsorption of the three dyes onto EPIDMA/bentonite was described by the Langmuir isotherm model and the pseudo-second-order kinetic model. At low dosage of EPIDMA/bentonite, preferential adsorption was observed for the dye with higher affinity to the adsorbent in mixed dye systems. The reduction in uptake of the dye with increasing equilibrium dye concentration in the isotherm and desorption in the kinetic curves were observed for the dye with lower affinity. The total amount of dyes adsorbed versus the total equilibrium dye concentrations were fitted well by the Langmuir isotherm model. The kinetics of the total adsorbed amount of dyes followed the pseudo-second-order kinetic model. The effect of the dosage of adsorbent on color removal efficiency, residual color distribution and adsorption kinetics was investigated.     

Cadmium(II) removal from aqueous solution using microporous titanosilicate ETS-10

In this work, the removal of Cd²⁺ ions from aqueous solution using microporous titanosilicate ETS-10 was investigated in order to assess its potential as decontaminating agent in tertiary treatments. Accordingly, batch stirred tank experiments were carried out to study the ion exchange kinetics and equilibrium. Results show that pH affects considerably the ion exchange capability of ETS-10: at pH 4 it is 1.567 × 10² eq m⁻³, at pH 6 it is 3.629 × 10³, and no further increment was observed at pH 8. This is an extremely important observation since pH of industrial effluents and other wastewaters rounds 6. Both Langmuir and Langmuir–Freundlich isotherms were fitted to the experimental data measured. The second model performs slightly better as the calculated absolute average deviations show: AAD_L = 2.94% and AAD_LF = 2.40%. Concerning the kinetic behavior, the ion exchange was successfully represented by a Nernst–Planck based model (AAD = 11.9%).     

Methods for measuring water activity (aw) of foods and its applications to moisture sorption isotherm studies

Moisture sorption isotherm is commonly determined by saturated salt slurry method, which has defects of long time cost, cumbersome labor, and microbial deterioration of samples. Thus, a novel method, a_w measurement (AWM) method, has been developed to overcome these drawbacks. Fundamentals and applications of this fast method have been introduced with respects to its typical operational steps, a variety of equipment set-ups and applied samples. The resultant rapidness and reliability have been evaluated by comparing with conventional methods. This review also discussed factors impairing measurement precision and accuracy, including inappropriate choice of predryingwetting techniques and unachieved moisture uniformity in samples due to inadequate time. This analysis and corresponding suggestions can facilitate improved AWM method with more satisfying accuracy and time cost.     

Statistically modeled adsorption isotherms for the multilayer gas molecules adsorbed on non-porous solid adsorbents of two and three groups sites

The adsorption isotherms with each saturation vapor pressure factor (c_s1, c_s2 or c_s3) for two groups of sites in two cases of the multilayer and for three groups of sites in one case of the multilayer are derived statistically in heterogeneous non-porous solid adsorbents without interactions among the adsorbed molecules. When some sites of BET isotherm are substituted by less energetic sites, the two-group isotherm obtained by the substitution shows less adsorption over the whole range of relative pressure than the BET isotherm prior to the substitution, at any combined values of f₁ with M₁ of the two-group isotherm with the same saturation vapor pressure factor. A method to get the monolayer sites (v_m) from the ratios of the experimental isotherm to the theoretical isotherm at the whole relative vapor pressure minimizing the standard error is suggested. Our two- or three-group isotherms calculated through many experimental adsorption isotherm data selected appropriately provide larger values of v_m than those obtained from BET isotherms. Differential heat vs. v/v_m and Bose-Condensation heat are mentioned.     

A simple method to determine the adsorption isotherm of taxol from a yew tree

Taxol, a powerful anticancer agent, was extracted from yew extract and separated by NP-HPLC (NormalPhase High Performance Liquid Chromatography). At the mobile phase composition of hexane/IPA/MeOH, 90/4/6 vol%, taxol was preparatively separated in a chromatographic column with large packings (15 μm). The purified taxol was used to determine the adsorption isotherm of taxol. From the experimental results, the adsorption isotherm was obtained as the following Langmuir type,

Adsorption isotherms of phenols from water onto macroreticular resins

The amounts of equilibrium adsorption of phenol and 4-chlorophenol from water on non-ionic macroreticular resins were measured in the temperature range 288–318 K. It was shown that the isotherm data could not be fit by any conventional two- or three-parameter equation including the Langmuir, Freundlich, BET, and Redlich–Peterson equations over the entire range of concentration (1–32 mol m⁻³). They were well fit by combined BET equation or its modified form with the Freundlich or Langmuir equation, depending on the types of solutes and the resins. Such different fitting results could be related to the solute–resin interactions owing to the relatively wide pore size distribution of the resins. The effect of temperature on adsorption equilibrium was also discussed.     

Removal of Cr(III) in the fixed bed column and batch reactors using as adsorbent zeolite NaX

In this work, the uptake capacity of Cr(III) ions in NaX zeolite was investigated. The experiments were carried out in continuous and batch systems at . The batch isotherm evidenced an irreversible shape with a maximum chromium uptake of 3.61 meq/g. The column experiments were carried out at pH=3.5, with a flow rate of 9 ml/min and an average particle size of 0.180 mm. The dynamic system provided a distinct ion-exchange mechanism, which generated a favorable isotherm with a chromium uptake of 3.27 meq/g. A mathematical model was also applied to represent the dynamics of the sorption of the column. The model considered the axial dispersion in the column and the intraparticle diffusion as the rate-controlling step. The dynamic isotherm was successfully modeled by the Freundlich equation and the mathematical model described well the experimental dynamic data for the feed concentrations from 0.3 up to 3.0 meq/g.