Study on the build of channels in accurate separation membrane and its selective mechanism

A new accurate separate membrane (ASM) for highly specific binding and permeation of luteolin molecules from aqueous solutions has been developed by a molecular imprinting technique. Luteolin molecular imprinted materials were prepared with luteolin modified by acryloyl chloride as the template molecule, followed by dispersing into polysulfone (PSF) to form the ASM with continuous and highly selective pore channels by a phase inversion method. Thus prepared ASM was characterized and evaluated by scanning electron microscope (SEM), attenuated total reflectance infrared (ATR-FTIR) spectroscopy technique, and binding experiments. The results showed that continuous distributed pore channels matching with the template molecules in size and structure were present in the ASM. The selective binding amount reached at 28.6 mg/g for the ASM, while a lower value of 3.67 mg/g for the blank membrane (i.e. non-templated). Relative to the corresponding blank membrane, ASM had an excellent recognition to luteolin in aqueous solution. The permeation flux of ASM increased with the increase in the amount of the molecular imprinted materials. Separation of an aqueous mixture containing similar molecules (luteolin and rutin) indicated that the separation factor of luteolin and rutin is as high as 10.78. It is concluded that the molecular imprinting allowed for preferential permeance and high selectivity to the template molecule (i.e. luteolin). The results also showed the formation of pore channels created by interparticle cavities in the molecular imprinted materials. The size and structure of the channels matched well with luteolin molecules while the recognition functional groups in the pore channels of the ASM could selectively bond with the luteolin molecules by multi-hydrogen bonds. It is believed that bond cleavage and molecular hopping to another bonding site were involved in this separation process.