The kinetics of sorption from a solution onto an adsorbent has been explored theoretically. The general analytical solution was obtained for two cases. It has been shown that at high initial concentration of solute (sorbate) the general equation converts to a pseudo-first-order model and at lower initial concentration of solute it converts to a pseudo-second-order model. In other words, the sorption process obeys pseudo-first-order kinetics at high initial concentration of solute, while it obeys pseudo-second-order kinetics model at lower initial concentration of solute. The theoretical results (derived equations) show that the observed rate constants of pseudo-first-order and pseudo-second-order models are combinations of adsorption and desorption rate constants and also initial concentration of solute. The obtained theoretical equations are used to correlate experimental data for sorption kinetics of some solutes on various sorbents. The predictions of the theory are in excellent agreement with the experimental data.

Kinetic models of sorption: a theoretical analysis.

http://dns2.asia.edu.tw/~ysho/YSHO-English/Publications/PDF/Wat%20Res40,%20119.pdf

Second-order kinetic model for the sorption of cadmium onto tree fern: a comparison of linear and non-linear methods.

Adsorptive removal of hazardous anionic dye "Congo red" from wastewater using waste materials and recovery by desorption.

Adsorption of dyes from aqueous solutions on activated charcoal.

The defluoridation capacity (DC) of a chelating resin, namely Indion FR 10 (IND), and Ceralite IRA 400 (CER), an anion-exchange resin, were compared under various equilibrating conditions for the identification of selective sorbent. The results showed that chelating resin is more selective than an anion-exchange resin for fluoride removal. The fluoride sorption was reasonably explained using Freundlich and Langmuir isotherms. The surface morphology of resins before and after fluoride sorption was observed using scanning electron microscopy (SEM). Fourier transform infrared spectroscopy (FTIR) was used for the determination of functional groups responsible for fluoride sorption. Various thermodynamic parameters such as DeltaG0, DeltaH0, DeltaS0, and Ea have been calculated to understand the nature of sorption. The sorption kinetic mechanism was studied with reaction-based and diffusion-based models. The sorption process was found to be controlled by pseudo-second-order and particle diffusion models. The performance of the resins studied has been tested with field samples collected from a fluoride-endemic area.

Identification of selective ion-exchange resin for fluoride sorption.

The adsorption of the anionic dyes orange IV, orange G and xylenol orange on chitin was studied, employing the Langmuir isotherm. The adsorption parameters were determined utilizing various linear regressions of the isotherm. The results showed that the adsorption capacity is dependent on pH. In acid pH, the polymer amino groups are protonated and the polymer chain is positively charged, with a predominance of adsorption through ion exchange. Van der Waals adsorption, as well as adsorption through hydrogen bonding, is also likely to occur to some extent. For xylenol orange, a linear regression was found, with an angular coefficient of 0.726 L mg-1. The temperature increase reduces adsorption capacity by chitin, due to the enhancement of the desorption step in the mechanism. DH values of -10.9 kJ mol-1 for orange G and -28.9 kJ mol-1 for orange IV prove the physical nature of the adsorption by these dyes on the chitin surface.

/pdf/adsorption-of-anionic-dyes-on-the-biopolymer-chitin-50z92ddqs7.pdf

Adsorption of Anionic Dyes on the Biopolymer Chitin

Adsorption of Cu(II), Ni(II), Pb(II) and Zn(II) ions from aqueous solutions by N-(3,4-dihydroxybenzyl) chitosan have been carried out. The Langmuir (L), Freundlich (F), Langmuir - Freundlich (LF), Redlich-Peterson (RP) and Toth (T) adsorption isotherms models have been applied to fit the experimental data. Nonlinear regression computational program "Enzefitte", which is a library of the more commonly used adsorption isotherm equations for obtaining tabular outuput suitable for plotting theoretical of fitted isotherms, has been used to estimate the adsorption parameters. These parameters were used to calculate the amount adsorbed qcalc., a function of concentration (C).

/pdf/analise-das-isotermas-de-adsorcao-de-cu-ii-cd-ii-ni-ii-e-zn-2z2ol3ezcw.pdf

Análise das isotermas de adsorção de Cu(II), Cd(II), Ni(II) e Zn(II) pela N-(3,4-dihidroxibenzil) quitosana empregando o método da regressão não linear

Capsules were prepared from chitosan (QTS)-poly(vinyl alcohol) (PVA) blend by saline coacervation and then by formalization. A adsorbent based on chitosan, insoluble on acid solution, was obtained. The morphology, average diameters of QTS/PVA capsules and their pores were studied by using scanning electron microscopy. The entrapment-adsorption of dimethylglioxime and ethylenediaminetetracetate by the capsules were studied. The removal of the ion nickel (II) and copper (II), was more effective than by using unloaded capsules.

/pdf/processo-alternativo-para-remocao-de-cobre-ii-e-niquel-ii-de-4mr7ds2wia.pdf

Marilene Klug

Papers

Adsorption of Anionic Dyes on the Biopolymer Chitin

Análise das isotermas de adsorção de Cu(II), Cd(II), Ni(II) e Zn(II) pela N-(3,4-dihidroxibenzil) quitosana empregando o método da regressão não linear

Processo alternativo para remoção de cobre (II) e níquel (II) de soluções aquosas utilizando cápsulas de quitosana - Álcool Polivinílico