Introduction of an ordered porous polymer network into a ceramic alumina membrane via non-hydrolytic sol–gel methodology for targeted dynamic separation

Abstract

A highly selective composite imprinted alumina membrane (CIAM) for gentisic acid (GA) was successfully synthesized by the nonhydrolytic sol–gel (NHSG) method with room temperature ionic liquid (RTIL) as the pore template. The carboxylic acid was used as both the functional monomer and the catalyst to form the alumina membrane-based porous imprinted polymer layer. The adsorption capacities, fluxes and permeation selectivities of various CIAMs suggested that cinnamic acid (CA) was the promising functional monomer for preparing a CIAM to separate GA from salicylic acid (SA) and the incorporation of RTIL improved the selectivity of GA over CIAM. The amount of porous imprinted polymer layer on the CIAM significantly affected the separation of GA from SA over CIAM. A three-level Box–Behnken experimental design with three factors combining the response surface modeling was used to optimize the dynamic separation process. The experimental data were well fitted to a second-order polynomial equation using multiple regression analysis. The optimal conditions for the separation of GA from SA were as follows: GA concentration of 0.0325 mmol L⁻¹, temperature of 15.0 °C and flow rate of 1.0 mL min⁻¹. Under these conditions, the experimental separation factor was 13.26 ± 0.87%, which was close to the predicted separation factor.