Increasing the large scale feasibility of a solid phase extraction procedure for the recovery of natural antioxidants from olive mill wastewaters

The present investigation was focused on improving the feasibility of large scale applications of a solid phase extraction (SPE) procedure dedicated to the recovery of polyphenols from olive mill wastewaters (OMWs). To this aim, a previously developed SPE procedure was optimized in terms of contact time without negatively affecting the overall process productivity. The possibility of regenerating and recycling both the solid phase (Amberlite XAD16 non-polar resin) and the extraction solvent (acidified ethanol) was also demonstrated. In particular, the resin was successfully reused in 10 consecutive SPE cycles (including washing and reactivation steps), allowing almost constant polyphenols adsorption and desorption ratios (81.44 ± 0.91% and 52.69 ± 5.57%, respectively). Up to 695 mL of ethanol per liter of exhausted extraction solvent were recovered by means of a rotary evaporator. Furthermore, the solvent conventionally used for resin activation (i.e., methanol) was successfully substituted by a more biocompatible solvent (i.e., ethanol). An ORAC value corresponding to 6979 lM of Trolox equivalents was observed for the concentrated polyphenolic solution, obtained as a result of rotary evaporator operations. Importantly, no substantial loss of radical scavenging and antioxidant activities occurred by means of the aforementioned operations dedicated to the recovery of ethanol from the obtained polyphenolic solution.