A novel chitosan base molecularly imprinted membrane for selective separation of chlorogenic acid

Using molecularly imprinted technology and the phase inversion method, a chlorogenic acid molecularly imprinted chitosan membrane was prepared. Chlorogenic acid was used as the template molecule and chitosan as the film-forming material. Sulfuric acid was chosen as the cross-linking agent, in order to inhibit the swelling of chitosan membranes. The selectivity of these imprinted membranes in terms of permeability and adsorption capacity was studied. Furthermore, the chemical composition and surface structure of the membranes as well as their thermo-stability were characterized. Scatchard results show that there are two kinds of adsorption sites present on the molecularly imprinted membranes, one with high affinity sites and one with low affinity sites. For the high affinity sites, the maximum adsorption capacity was 139.57 μmol g−1 and that for the low affinity sites was 287.86 μmol g−1. In contrast, for the non-imprinted membranes, only one kind of sites was found, with a maximum adsorption capacity of 83.84 μmol g−1. The adsorption isotherms indicate that the adsorption isotherm curve of chlorogenic acid binding onto the imprinted membrane agrees with the Freundlich model while that of the non-imprinted membrane conforms to the Langmuir model. The permeation experiments proved that the imprinted membrane has a selective adsorption capacity for chlorogenic acid.