Preparation and evaluation of molecularly imprinted composite membranes for inducing crystallization of oleanolic acid in supercritical CO2

In this study, novel molecularly imprinted composite membranes (MICMs) for inducing crystallization of oleanolic acid (OA) in supercritical CO2 (ScCO2) have been described. The MICMs were synthesized by the UV initiated photo-copolymerization, with OA as a template molecule, copolymerization of methacrylic acid (MAA) as a functional monomer, ethylene glycol dimethacrylate (EGDMA) as a crosslinker and polysulfone (PSF) ultrafiltration membranes as porous supports. The preparation conditions of OA-MICMs were optimized as follows: the molar ratio of OA, MAA and EGDMA 1 : 4 : 12, the amount of photoinitiator 1.5%, the concentration of OA 1 mmol L-1 and the elution time 6 h. Scanning electron microscopy (SEM) was used for the characterization of MICMs. The MICMs were used for inducing crystallization of OA in ScCO2. The purity and the crystallization rate of OA were 98.3% and 45.3%, respectively. Our work presents a new method to induce crystallization of OA in ScCO2 by using MICMs, with specific adsorption properties and capacities.