Comparison studies of adsorption properties for copper ions in fuel ethanol and aqueous solution using silica-gel functionalized with 3-amino-1,2-propanediol

Silica-gel functionalized with 3-amino-1,2-propanediol (SG-AP) was used as adsorbent for the removal of copper ions from both aqueous and ethanol solutions. The adsorption isotherms and adsorption kinetics were comparatively investigated by using batch method. The static saturated adsorption amount for Cu2+ in ethanol is less than that in aqueous, indicating a much lower adsorption rate. The experimental data were fitted to pseudo-first-order and pseudo-second-order kinetic models. The results indicated that all the adsorption data in both solutions fitted well with the second-order kinetic model, implying that SG-AP is suitable to apply in the low initial concentration of copper ions in aqueous or ethanol solution. The adsorption isotherms were fitted by the Langmuir, Freundlich and Dubinin-Radushkevich (D-R) models. It was showed that the adsorption processes in both aqueous and ethanol solutions were favorable and Freundlich model was much appropriate. From the D-R isotherm model, the calculated mean free energy E showed that the adsorptions occurred in aqueous via physical processes, while those in ethanol mainly via chemical processes. Desorption study showed that SG-AP had good durability as well as good efficiency for repeated use.