Mixed matrix scaffolds were synthesized by uniformly distribution of ion exchange resins (H+ form Amberjet, ID 780 µm) into the stereo-structural chitosan matrix prepared by chitosan powder with middle molecular weight and then applied for the removal of copper ions from waste water. Specifically, ion exchange resin particles suspending in a 1 wt% of viscous chitosan solution were filled with cylindrical aluminum containers to prepare chitosan mixed matrix scaffolds through the freeze-gelation process. The internal surface area of mixed matrix scaffolds is 78 m2/g by the measurement of N2 adsorption/desorption processes. The uniform distribution of ion exchange resins embedded in the stereo structure of chitosan matrices can clearly be seen in the scanning electron micrograph which will facilitate the adsorption of chitosan as well as ion exchange resins. The adsorption processes were performed by adsorption copper ions of waste water onto the amine functional groups (-NH2) exposed to the external and porous stereo-structural surfaces of chitosan matrix as well as the sulfonate functional groups at the outer surface of ion exchange resins respectively. Results of continuous well-mixed adsorption experiments showed that both copper ions and hydronium ions compete for available adsorption sites on the ion exchanger particles as well as chitosan by adsorption mechanism. Adsorption isotherms at 25 ℃ and pH 6.0 over the concentration ranging from 50 to 1500 mg Cu2+/L performed distinct stepped shape. As copper ions penetrate the porous structure of mixed matrix scaffolds and adsorb on the exposed amines of chitosan and sulfonic sites of ion exchange resins near the outer surface, the formation of adsorbed copper clusters may constrict pores. These effects would be more pronounced when the behavior of adsorption isotherms was observed at its first step. The maximum adsorption capacity for mixed matrix scaffolds were 190 mg Cu2+/g-adsorbents at the initial copper ion concentration of 1500 mg Cu2+/L. The stepped shape of the isotherm revealed that a pore-blockage mechanism may occur along the adsorption processes. Results of well-mixed batch adsorption experiments of PVA-chitosan mixed matrix scaffolds revealed that adsorption isotherms at 25 ℃ and pH 6.0 over the concentration range 200 ~ 3000 mg Cu2+/L could be simulated by a Langmuir adsorption model. The desorption ratio of copper ions of PVA-chitosan mixed matrix scaffolds was 97.9% at low initial copper ion concentrations. As desorption ratio decreased, the initial copper ion concentrations increased.

Mixed matrix, chitosan, copper ions