Study On Enzymatic Grafting And Adsorption Properties For Cd～(2+),Cu～(2+) Of Chitosan-(p-Hydroxybenzoic Acid)

Tyrosinase was extracted from potatoes, and its biochemical properties were studied.Enzymatic activity of tyrosinase against L-DOPA was optimal at pH 5.8 and 25℃. TheMichaelis Constant(K_m) was 4.76 mmol·L^-1. The p-hydroxybenzoie acid was selected fordetermining types of inhibition and the result showed that p-hydroxybenzoic acid was acompetitive inhibitor, with Inhibition Constant of 14.3 mmol·L^-1.The p-hydroxybenzoic acid was catalyzed and oxidized by potato tyrosinase toreactive o-quinones, which was grafted onto chitosan. The structure and property of thegrafting reactant were characterized by UV-Vis,FTIR,TG-SDTA and DSC. The effect ofsynthesis conditions on graft rate were investigated. The adsorption of Cd²³,Cu²⁺ bygrafted films were studied. The results indicated that the p-hydroxybenzoie acid had beengrafted onto ehitosan by tyrosinase. The graft rate was determined to be 47～58% withlinear titrimetric method. The grafted film's adsorption capacity for Cd²⁺,Cu²⁺ was163.7mg·g^-1 and 119.0 mg·g^-1, respectively. The adsorption of grafted films to Cd²⁺obeyed the Freundlich isotherm equation, however, the adsorption to Cu²⁺ were correlatedby the Langmuir isotherm equation and the Freundlich isotherm equation.