Recovery and purification of natural antioxidants from olive mill wastewater concentrates by a sustainable process

Abstract

Olive mill wastewater (OMWW) resulting from olive oil production is characterized with high organic load and phytotoxicity due to the presence of phenolic compounds (PCs). Antioxidant properties of PCs make this waste a potential resource for some industries. Hence, instead of spending effort to treat the toxic components, the recovery of value-added compounds from OMWW can be sustainable waste management solution providing economic benefits. This study was aimed to find out a recovery process for antioxidant PCs mainly hydroxytyrosol (HTyr). The concentrated OMWW samples by Mechanical Vapor Recompression (MVR) evaporator at two different rates, OMWC1 and OMWC2 were subjected to solid phase extraction (SPE) by using different synthetic polymeric resins stands alone (Process I) and as integrated to aqueous two-phase extraction (ATPE) (Process II). Process I and II with non-ionic PAD 950 yielded higher total PCs recovery from both OMWCs while the performance of Amberlyst A26 resin in Process II was better for HTyr recovery. The recoveries of HTyr were 21.77 and 34.31 mg/g from more concentrated OMWC2 by Process II whereas 4.88 and 3.86 mg/g HTyr were recovered from OMWC1 by the application of Process I with PAD 950 and Amberlyst A26 resins, respectively. The first extraction stage of Process II with ATPE system minimized the coextraction of non-target compounds and in overall Process II provided the eliminations of 85-90% carbohydrates and almost complete proteins from the extract of OMWC2. The antioxidant activities of the extracts achieved from more productive Process II exhibited variation depending the applied activity assays.