Application of chitosan, a natural aminopolysaccharide, for dye removal from aqueous solutions by adsorption processes using batch studies: A review of recent literature

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.

Of late, the most bountiful natural biopolymer chitin and chitosan have become cynosure of all party because of an unusual combination of biological activities plus mechanical and physical properties. However applications of chitin are limited due to its inherent insoluble and intractable nature. Chitosan, alkaline hydrolytic derivative of chitin has better solubility profile, less crystallinity and is amenable to chemical modifications due to presence of functional groups as hydroxyl, acetamido, and amine. The chemical modification of chitosan is of interest because the modification would not change the fundamental skeleton of chitosan, would keep the original physicochemical and biochemical properties and finally would bring new or improved properties. In view of rapidly growing interest in chitosan its chemical aspects and chemical modification studies is reviewed. The several chemical modifications such as oligomerization, alkylation, acylation, quternization, hydroxyalkylation, carboxyalkylation, thiolation, sulfation, phosphorylation, enzymatic modifications and graft copolymerization along with many assorted modifications have been carried out. The chemical modification affords a wide range of derivatives with modified properties for specific end use applications in diversified areas mainly of pharmaceutical, biomedical and biotechnological fields. Assorted modifications including chitosan hybrids with sugars, cyclodextrin, dendrimers, and crown ethers have also emerged as interesting multifunctional macromolecules. The versatility in possible modifications and applications of chitosan derivatives presents a great challenge to scientific community and to industry. The successful acceptance of this challenge will change the role of chitosan from being a molecule in waiting to a lead player.

Chitosan-modifications and applications: Opportunities galore

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

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 calcium ions by graft copolymer of acrylic acid on biopolymer chitin

Chitosan microspheres were employed as adsorbent in aqueous medium for the reactive orange 16 containing the vinylsulfone group. Adsorption isotherms were obtained varying pH, contact time, and initial concentration of the dye in the solution. The results from the adsorption experiments were analyzed using Langmuir's isotherm. An increase in the adsorption capacity as the pH decreased could be observed. Maximum adsorption reached 30.4mg/g and 5.6mg/g for pH 2.0 and 10.0, respectively. This effect could be mainly attributed to an increase in the contents of the NH + 3 group present in acid media, which resulted in a higher electrostatic attraction between the anionic dye and the protonated chitosan.

The interaction between reactive dye containing vinylsulfone group and chitosan microspheres

/pdf/adsorcao-de-azul-de-metileno-e-croconato-amarelo-pelo-xyli53mxpl.pdf

Lígia Furlan

Papers

Adsorption of Anionic Dyes on the Biopolymer Chitin

Adsorption of calcium ions by graft copolymer of acrylic acid on biopolymer chitin

The interaction between reactive dye containing vinylsulfone group and chitosan microspheres

Adsorção de Azul de Metileno e Croconato Amarelo pelo Biopolímero Quitina