STUDY OF CHITOSAN ENZYMATIC GELATION KINETICS FOR MEMBRANE PREPARATION

摘要

Chitosan is a natural biopolymer with excellent sorption properties that can be used to prepare flat-sheet "greener" filtration/sorption membranes without using organic solvent. The first step in chitosan membrane preparation, before drying and cross-linking steps, lies in the formation of a chitosan gel. Generally, chitosan is initially dissolved in acidic water then gelation is induced by basic media intake (usually ammonia) from liquid or vapor phase (Equation 1). However, the gelation process is initiated on one face of the polymer solution, which induces a non-solvent concentration gradient leading to a heterogeneous structure of the gel. An original enzymatic gelation process has been recently proposed (Chenite et al. 2006, Yan et al. 2014), based on the in-situ production of ammonia in the chitosan solution by the enzymatic hydrolysis of urea by urease (Equation 2).