Mathematical Modeling of Fixed-Bed Columns Adsorption: Hexavalent Chromium onto Chitosan Flakes

Continuous fixed-bed column adsorption for wastewater treatment provides the most practical application to reduce water pollution by heavy metal ions. The objective of this work was to develop a new statistical approach capable of simulating the dynamic behavior of the fixed-bed adsorption. A statistical model (normal model), based on normal distributions, was deduced and experimentally validated in a Bayesian framework. The model was applied to describe the adsorption mechanism of Cr(VI) onto chitosan flakes, obtained from the waste of crustacean industry. The continuous flow of Cr(VI) was carried out in a glass column, at different operating conditions, determining the breakthrough curve and the breakthrough point time (tb). The proposed normal model provided a good description of the column adsorption with fitting error comparable to that of the widely used Bohart-Adams logistic model. In all cases, the tb was into or near to model credibility interval. Therefore, the model with the Bayesian approach represents a good option for the design of adsorption columns for wastewater treatment.Fil: Dima, Jimena Bernadette. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Centro Nacional Patagónico. Instituto de Biología de Organismos Marinos; Argentina. Universidad Nacional de la Patagonia "San Juan Bosco"; Argentina. Universidad Nacional de La Plata. Facultad de Ingeniería; ArgentinaFil: Ferrari, Mariano Andrés. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Centro Nacional Patagónico. Centro para el Estudio de Sistemas Marinos; Argentina. Universidad Nacional de la Patagonia "San Juan Bosco"; ArgentinaFil: Zaritzky, Noemi Elisabet. Universidad Nacional de La Plata. Facultad de Ingeniería; Argentin

Effect of crosslinking agents on chitosan microspheres in controlled release of diclofenac sodium

In this work chitosan microspheres were prepared by the simple coacervation method and crosslinked using epichlorhydrin or glutaraldehyde for the controlled release of diclofenac sodium. The effects of the crosslinking agents on chitosan microspheres over a 12-hour period were assessed with regard to swelling, hydrolysis, porosity, crosslinking, impregnation of diclofenac sodium (DS), and consequently to the release of DS in buffer solutions, simulating the gastrointestinal tract. The degree of swelling varied with the pH for glutaraldehyde chitosan microspheres (GCM) and epichlorhydrin chitosan microspheres (ECM). Partial acid and basic hydrolysis affected the swelling behavior of the GCM matrix. Release kinetics of diclofenac sodium from these matrices were investigated at pH 1.2, 6.8 and 9.0, simulating the gastrointestinal tract conditions. The results indicated that the release mechanism deviated slightly from Fickian transport