Green management of wet olive pomace by means of ultrafiltration of an aqueous extract of phenolic compounds

Wet olive pomace is a major by-product generated by olive mills. To contribute to the circular economy of the olive industry, the recovery of interesting compounds from wet olive pomace was assessed. To that end, a previously optimized solid-liquid extraction, only employing water as the extractant, was first applied to the wet olive pomace. Afterwards, an ultrafiltration process to treat the obtained extract was developed. Several membranes (UP005, UH030, UH050, and UP150, from Microdyn Nadir) were studied, in a wide range of cross-flow velocities (1.5-3.5 m/s) and transmembrane pressures (0.75-5.5 bar). By a thorough characterization of the ultrafiltration streams by LC-ESI-QToF-MS, it was possible to describe the evolution of the rejection of 29 phenolic compounds. Some adsorption processes were also observed in the ultrafiltration process. The UP005 and UH030 membranes displayed satisfactory values of permeate flux and rejection. Both membranes efficiently retained a high fraction of the total solids, chemical oxygen demand, and color. On the contrary, the phenolic compounds were obtained in the ultrafiltration permeate, which constitutes a source of antioxidant molecules with applications in cosmetics, pharmacy, and nutraceutics.