Molecularly Imprinted Polymers for Gossypol via Sol–Gel, Bulk, and Surface Layer Imprinting—A Comparative Study

Three gossypol molecularly imprinted polymers (MIPs) were prepared by bulk polymerization (MIP1), surface layer imprinting using silica gel as the support (MIP2), and the sol-gel process (MIP3). The as-prepared MIPs were characterized by SEM and nitrogen adsorption-desorption techniques to study the morphology structure. The adsorption experiments exhibited that MIP1 had adsorption capacity as high as 564 mg·g-1. The MIP2 showed faster adsorption kinetics than MIP1 and MIP3. The adsorption equilibrium could be reached for gossypol in 40 min. A selectivity study showed that the adsorption capacity of MIPs for gossypol was about 1.9 times higher than that of the structurally-similar analogs ellagic acid and 6.6 times higher than that of the quercetin. It was found that the pseudo-second-order kinetic model and the Freundlich isotherm model were more applicable for the adsorption kinetics and adsorption isotherm of gossypol binding onto the MIP1 and MIP2, respectively. Results suggested that among those three, the MIP2 was a desirable sorbent for rapid adsorption and MIP1 was suitable for selective recognition of gossypol.