Study on the preparation and adsorption thermodynamics of chitosan microsphere resins

Abstract

The aim of this research is to study the thermodynamic behavior of resins of chitosan microspheres (RCM) in adsorbing Cu²⁺, so that the theoretical basis of the application of RCM to eliminate metal ions in wastewater or fruit and vegetable juice can be obtained. First, RCM were prepared from chitosan as a raw material by using reverse phase suspension cross-linking polymerization, and some physicochemical properties of RCM were characterized. Second, the adsorption behavior of Cu²⁺ onto RCM was investigated by the batch method. The results show that the diameter of the microspheres was relatively uniform and the surface of microspheres was compacted with pores. The physical properties of the RCM were as follows: water content 51.982%, skeletal density 1.212 g•cm^-3, pileup density 0.862 g•mL^-1, porosity was in 0.554 and crosslinking degree was in 13.581%. The saturated adsorption capacity of RCM for Cu²⁺ was 0.993 mmol•g^-1. At the same time, the results also indicated that the adsorption of RCM for Cu²⁺ followed the Langmuir isotherm equation: C_e/Q=11.614+ 1.0075C_e at 313 K and the adsorption appeared to be of the monomolecular type. The adsorption was found through thermodynamic study to be a spontaneous endothermic process of increased entropy. The adsorption potential decreased gradually as Cu²⁺ concentration increased at the same temperature and it increased as temperature increased at the same initial concentration of Cu²⁺.

Keywords

resins of chitosan microspheres / adsorption Cu²⁺ / isothermal curve / thermodynamics

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