Removal of dyes from aqueous media using environmentally friendly aerogels based on chitosan

According to the World Health Organization, between 17% and 20% of water pollution is caused by dye treatments in the textile industry, which makes the development of efficient technologies for its removal essential. Environmentally friendly adsorbent materials, such as aerogels, can be effectively used in adsorption processes involving water remediation because of their high specific surface area and the possibility of an easy separation from the contaminated solutions. In this work, aerogels were obtained by a simple procedure that includes the cross-linking of chitosan with glutaraldehyde, followed by a freeze-drying step to eliminate water by water sublimation. The obtained aerogels presented low density (0.049–0.083 g/cm3), a three-dimensional skeletal structure that provides them with high porosity, acceptable swelling capacity and good dimensional stability. FTIR and X-Ray analysis were used to identify aerogels' chemical structure and dynamic-mechanical analysis to complement the characterization of these materials. Selected formulations were also tested as adsorbents of Congo Red in aqueous media. The adsorption results demonstrated that the aerogels adsorption capacity strongly depended not only on the crosslinking agent content but also on the amount of chitosan in the initial solution used in their synthesis. Moreover, preliminary thermodynamic studies of the adsorption process indicate that both adsorption rate and aerogel sorption capacity increase with increasing temperature.