Preparation and Adsorption Properties of Chitosan/Active Clay Composite as Sugar Juice Decolorization Agent

Chitosan/activated clay composite was prepared with chitosan solution and activated clay. With the decolorization ratio of sugar juice as an index, the effects of reaction temperature, reaction time, chitosan dosage and molecular weight on the preparation of chitosan/activated clay composite were investigated. The optimum conditions were obtained as follows: temperature 60 ℃, reaction time 7 h, chitosan dosage 2.0 g and molecular weight 2,000,000. The decolorization rate of the composite was up to 96.2%, which was significantly better than 56.7% of activated clay and 42.2% of chitosan. The decolorization rate of the structure of the composite was characterized by scanning electron microscopy, infrared spectroscopy, X-ray diffraction and thermogravimetric analysis. The results showed that chitosan was evenly distributed on the surface of activated clay, forming a more stable composite structure and maintaining the porous structure of activated clay. The thermal stability of the composite was higher than that of chitosan. The adsorption experiment of gallic acid in sugar juice showed that the adsorption kinetics of the composite conformed to the quasi second order kinetic model, the adsorption rate was controlled by the diffusion process outside the particles, and the adsorption process conformed to the Langmuir isothermal adsorption model, which was monolayer adsorption.