Increasing large-scale feasibility of two-phase olive-oil washing wastewater treatment and phenolic fraction recovery with novel ion exchange resins

Abstract

The present investigation was focused on improving the feasibility of large-scale application of a ‘green’ procedure to recover total antioxidant compounds (TACs) by solid phase extraction from the liquid residues of oleic industry (two-phase olive oil washing wastewaters, OOWW). To this aim, the use of ion exchange resins Dowex 21 K XLT® strong base and Dowex 66® weak base was examined. Adsorption capacity equal to 146.12 mg TACsadsorbed/gresin upon 114 gresin/LOOWW for the weak-base resin and 117.29 mg TACsadsorbed/gresin for 114 gresin/LOOWW for the strong-base resin was successfully attained. Thus, it was possible to recover up to 83.3% TACs with the weak-base resin in contrast to 60.8% with the strong-base one. Also, 55.8% vs. 53.7% COD removal was ensured. The process could be driven with raw OOWW, taken directly at the conditions at the outlet of vertical centrifuges, since narrow improvement with T and pH modifications was found. Moreover, significant reduction in phenols concentration would prevent biomass inhibition of further biological treatments, or even permit partial discharge on land. On the other hand, the high added-value concentrated pool of antioxidant compounds would be key to render the reclamation of this effluent feasible at industrial scale.