Olive Mill Wastewater Valorisation Through Polyphenol Adsorption

Due to the negative environmental impact of the Olive Mill Wastewaters (OMW), research is done in order to treat and valorize them. In this work, different OMW from different Italian regions (Liguria and Puglia) and harvests (from 2012 to 2014) were tested in order to recover polyphenols (PCs), molecules with a high added value because of their beneficial properties. The solid phase used for PCs recovery was the resin Amberlite XAD16; the desorption solvent was acidified ethanol. An HPLC method for total PCs content quantification was developed using a C18 column. A new, repeatable and reliable column packing method was developed. The packing quality was evaluated with step-change fluid dynamic analysis tests using NaCl 0.04M as tracer. Also, to avoid clogging problems in the packed columns an OMW pre-treatment was designed, capable to remove 98% of the solids. Several breakthrough tests were performed to evaluate the influence of linear velocity and column length (0.52m and 2.0m). A repeatability test was performed in order to evaluate the stability of the process. The process was modeled using a plug flow with axial dispersion model with solid-liquid mass transfer; implemented in COMSOL3.5a. The desorption curves were obtained with subsequent solvent regeneration. Antioxidant activity tests were performed with the desorption product using the ABTS method. On the basis of economic considerations, two new ion-exchange resins were tested (IRA958Cl and IRA 67Cl). IRA958Cl showed the best performance. Two breakthrough tests at different linear velocities were conducted with this resin. In order to recover specific high added value molecules (tyrosol and hydroxytyrosol) from the actual OMW, experiments were performed in collaboration with the Fachhoschule Nordwestschweiz (FHNW) using a Cyclodextrin-based polyurethane polymer, synthetized by the FHNW research group. Then, in order to increase the purity of tyrosol in the desorption fractions several organic solvents were tested.