Microfluidic preparation of chitosan microspheres with enhanced adsorption performance of copper(II)

This article presents facile microfluidic methods to prepare different chitosan microspheres by combining chemical crosslinking and solvent extraction. And the enhancement of Cu(II) adsorption kinetics and capacity was realized. The effects of solidifying time, initial concentration of Cu(II) and initial pH on adsorption performance were systematically studied. The adsorption isotherms can be fitted with Langmuir equation. The adsorption capacity was about 50 mg/g, which is similar to that in references. To enhance the adsorption kinetics, porous chitosan microspheres were prepared by using poly(ethylene glycol) to form the pores. Many tiny pores were closely arranged on the surface, which resulted in accelerating the adsorption of Cu(II). And the adsorption time to reach equilibrium was reduced from 100 h to 20 h. To enhance the adsorption capacity, chitosan was crosslinked with another biocompatible polymer, poly(acrylic acid), and the blending microspheres were prepared with a two-step solidifying method. By adjusting the content of acrylic acid, the adsorption capacity could be increased to 66.3 mg/g. Finally, porous chitosan-poly(acrylic acid) composite microspheres were prepared by combining the above methods. Adsorption reached equilibrium after about 25 h and the adsorption capacity is about 72 mg/g. Both the adsorption kinetics and capacity of the composite microspheres were enhanced.