Síntese e caracterização do híbrido sílica/quitosana: estudo da interação com corante aniônico

Abstract

Organic and inorganic materials have been used as adsorbent materials of aquatic pollutants due to their both good adsorption capacities and physical and chemical stabilities. In this work, the ligand 3-aminopropytrimethoxysilane was immobilized on silica gel surface, with consecutive reactions with glutaraldehyde and chitosan. All materials were characterized by TG/DTG, DSC, FTIR, DRX and MEV, where the presence of the silica-immobilized chitosan was evidenced. The adsorption kinetics of the anionic dye remazol blue (AR) on the cross linked silica/chitosan (Sil-Quit-R) was studied in the temperature range of 25 - 55 ºC and initial dye concentration of 23 - 800 mg L-1. The results were best fitted to both the pseudo second-order Ho and McKay and the Avrami models. The AR dye adsorption at chemical equilibrium were best described using the three-parameter Redlich-Peterson I, Sips, Tóth, Baudu I and five-parameter Fritz-Schlunder IV models. From these results, the heterogeneity of the Sil-Quit-R adsorption sites was evidenced. The adsorption enthalpies (ΔadsH) were all endothermic and increased with the increasing of adsorption temperature. The negative values for ΔadsG have indicated that the adsorption processes are spontaneous. The adsorption entropies (ΔadsS) were all positive and increased with the increasing of adsorption temperature. From the thermodynamic viewpoint, the positive ΔadsS values were the adsorption driving force. The adsorption capacity of Sil-Quit-R was good, mainly related to the adsorption results at low dye concentrations in solution.