Selective extraction and purification of gallic acid from actual site olive mill wastewaters by means of molecularly imprinted microparticles

An innovative biocompatible approach for the selective recovery of gallic acid (GA) from actual site olive mill wastewaters (OMWs) by means of Molecularly Imprinted Polymers (MIPs) was developed. Bulky MIPs with a high selectivity for GA were synthesized by a non-covalent approach using methacrylic acid as the functional monomer and ethylene glycol dimethacrylate as the crosslinker. Imprinting efficiency was evaluated in different water/ethanol solutions by determining a and e parameter, by using pyrogallic acid as the template analogue: the highest GA recognition, both in terms of percentage and of imprinting effect (a = 32.7; e = 4.2), was observed in pure ethanol. The efficiency of the developed extraction protocol was evaluated with an actual site OMW: a selective extraction of 80% of pure GA was achieved with high accuracy and precision, as shown by RSD% (4.3%) and recovery values (between 85% and 97%).