Bioinspired Fabrication and Evaluation of Molecularly Imprinted Nanocomposite Membranes with Inorganic/Organic Multilevel Structure for the Selective Separation of Emodin

High purity emodin is in great demand with the development of medical treatment. Molecularly imprinted membranes (MIMs) have gained wide attention for selective separation of emodin due to its preferable selectivity. In this work, we describe a simple two-step method for developing emodin-imprinted TiO 2 @CA (ETMIMs) and emodin-imprinted SiO 2 @CA (ESMIMs) based on organic–inorganic nanoparticle (SiO 2 /TiO 2 ) modified cellulose acetate membranes at room temperature. SiO 2 /TiO 2 is used to improve the structural stability and roughness of membranes, and dopamine is used as the functional monomer and crosslinker. Importantly, the as-prepared membranes not only exhibited enhanced rebinding capacity ( ETMIMs = 3 0 . 7 3 mg g − 1 $\mathrm{\text{ETMIMs}}=30.73\mathrm{\text{mg}}{\mathrm{\text{g}}}^{-1}$ and ESMIMs = 4 6 . 0 4 mg g − 1 $\mathrm{\text{ESMIMs}}=46.04\mathrm{\text{mg}}{\mathrm{\text{g}}}^{-1}$ ) but also possessed superior rebinding selectivity (2.76 and 2.99 for physcion and 2.42 and 3.30 for aloe emodin onto ETMIMs and ESMIMs) as well as permselectivity (7.59 and 6.69 for physcion and 5.94 and 5.78 for aloe emodin onto ETMIMs and ESMIMs). The regeneration ability of ETMIMs and ESMIMs still maintained 90.4% and 89.2% of the original rebinding capacity after 10 cycling steps, respectively. The ETMIMs and ESMIMs obtained in this work show potential applications for selective separation and purification of emodin from analogs.