Preparation of composite-imprinted alumina membrane for effective separation of p-hydroxybenzonic acid from its isomer using Box-Behnken design-based statistical modeling

Highly selective composite imprinted membrane for p-hydroxybenzonic acid (p-HB) was prepared by using semicovalent imprinting technique. A thermally reversible covalent bond was used to link p-HB molecule to a functional alkoxysilane monomer to generate covalently bound imprint precursor. This precursor was incorporated into a cross-linked functional silica sol with the tetraethoxysilane as cross-linker via a typical acid-catalyzed, sol-gel synthesis. Then, the SCIM was prepared through dipping and grafting on the upper side and inner pores of the Al₂O₃ microporous membrane and then removing of the template molecule after thermal treatment. Compared with composite imprinted membrane via noncovalent imprinting approach as well as the black Al₂O₃ microporous membrane, the SCIM exhibited higher membrane flux and selective rebinding of p-HB as well as showing excellent permeability for p-HB. Response surface methodology was used to investigate the best combination of separation conditions in the dynamic separation process. The optimal conditions for the separation of p-HB from salicylic acid were as follows: the p-HB concentration of 5 mg L^-1, the temperature of 10°C, and the flow rate of 1 mL min^-1. Under these conditions, the experimental selective separation factor was 32.75±0.91%, which was close to the predicted selectivity coefficient value. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40621.