RESUMEN
The increase in biodiesel production has been leading to an excess amount of crude glycerol and, consequently, serious environmental issues. For this reason, electrospun chitosan-based nanofibers (CB-EN), composed by chitosan and poly(ethylene oxide) (PEO), were synthesized to apply in the biosorption of impurities from industrial glycerol. To evaluate the biosorption efficiency, the chitosan-based nanofiber was compared to other chitosan-based biosorbents (chitosan biopolymeric film and chitosan powder). The equilibrium and thermodynamic studies were successfully performed to comprehend the interaction mechanisms through the biosorption of glycerol pigments onto electrospun chitosan-based nanofibers. The temperature effect was evaluated by experimental equilibrium curves. Freundlich and BET models were used to estimate isotherm parameters. Gibbs free energy change, enthalpy change, entropy change, and isosteric heat of biosorption were quantified. The equilibrium curves showed that the highest equilibrium relative adsorption (340.7 g-1) was reached at 60 °C. The BET model was the most suitable to represent the equilibrium behavior. The thermodynamic parameters indicated that the biosorption was spontaneous, exothermic, random, and energetic heterogeneous. Therefore, this work developed a green and efficient alternative to refine industrial glycerol. Graphical abstract Note: This data is mandatory. Please provide.
Asunto(s)
Quitosano/química , Glicerol/metabolismo , Nanofibras/química , Adsorción , Biocombustibles , Glicerol/química , TermodinámicaRESUMEN
Adsorption of copper ions onto chitosan films was studied, and the matrix effect was evaluated using a synthetic solution and a real effluent from closed copper mine. Chitosan films were prepared by casting technique and characterized. The adsorption study was carried out by equilibrium isotherms, thermodynamics, and kinetics. The thermodynamic parameters indicated that the copper adsorption onto chitosan film was favorable, spontaneous, and exothermic, suggesting an increased randomness at the solid/solution interface. The matrix effect was evaluated in kinetic assays, where a synthetic solution and a real system were carried out at different stirring rates. The highest values of adsorption capacity reached in all stirring rates were about 20% lower in the real effluent, and this reduction in the competitiveness was due to the presence of other ions in the matrix of the real effluent. The maximum adsorption capacity of copper ions onto chitosan films for the synthetic solution was of 450 mg g-1, and the removal percentage was in the range from 78 to 96%, and these values for the real effluent were of 360 mg g-1 and removal ranging from 62 to 76%. The mapping done of ions present in the water adsorbed of the mine in the films showed that the same was homogeneously distributed in the films' surfaces.