Fabrication of highly selective molecularly imprinted membranes for the selective adsorption of methyl salicylate from salicylic acid

Herein, highly selective molecularly imprinted membranes (MIM) for methyl salicylate (MS) are synthesized with 4-vinylpyridine (4-VP), acrylamide (AM) or methacrylic acid (MAA) as the functional monomer based on the Al₂O₃ microporous ceramic membrane. Fast kinetic equilibrium for the rebinding of MS was found on all the imprinted membranes. Compared with AM-MIM and MAA-MIM, 4-VP-MIM presents a stronger adsorption capacity and higher permeation selectivity for MS due to the formation of ionic bonds between MS and 4-VP. SEM analysis shows that the surface morphology of the membranes is strongly influenced by the concentration of vinyltrimethoxysilane. Compared with 4-VP-MIM (1, 2 or 4), 4-VP-MIM3 possesses higher kinetic equilibrium adsorption, binding capacity and better selectivity for MS. It was found that the pseudo-second-order kinetic model is suited to describe the kinetic of 4-VP-MIM3, as determined by multiple regression analysis. The adsorption isotherm analysis exhibits that 4-VP-MIM3 has the maximum adsorption capacity for MS. Moreover, the selectivity experiment shows that the selectivity coefficients of 4-VP-MIM3 for MS relative to salicylic acid (SA) and phenol are 2.4185 and 2.2277, respectively, which are close to the predicted selectivity coefficient values.