Chemical Engineering Journal 166 (2011) 994–1001 Contents lists available at ScienceDirect Chemical Engineering Journal journal homepage: www.elsevier.com/locate/cej Recovery of low molecular weight phenols through solid-phase extraction Francesco Ferri a , Lorenzo Bertin a,∗ , Alberto Scoma a , Leonardo Marchetti a,b , Fabio Fava a a Unit of Environmental Biotechnology e Biorefineries - Department of Civil, Environmental and Materials Engineering (DICAM), Faculty of Engineering, University of Bologna, via Terracini 28, 40131 Bologna, Italy b INCA - Interuniversitary Consortium “Chemistry for the Environment”, via delle Industrie 21/8, 30175 Marghera (VE), Italy article info Article history: Received 18 August 2010 Received in revised form 23 November 2010 Accepted 23 November 2010 Keywords: Polyphenols Solid phase extraction Resin Adsorption isotherm Desorption abstract The recovery of polyphenols from olive mill wastewaters (OMWs) decreases the toxicity of the efflu- ent and permits the obtainment of high-added value natural antioxidants. Solid phase extraction (SPE) represents a valuable approach to obtain polyphenols from OMWs, since it relies on simple, cheap and environmental friendly procedures and agents. In this work, five resins with different physical properties, namely Amberlite XAD4, XAD7, XAD16, IRA96 and Isolute ENV+, were tested in parallel for their adsorp- tion and desorption features towards an aqueous solution of ten target phenolic compounds typically occurring in OMWs. Water, methanol and ethanol, also under basic and acidified conditions, were tested as possible desorbing agents. Adsorption isotherms related to the mixture of all phenols and to each sin- gle phenol were determined. Experimental data well fitted with Langmuir isotherm model. The highest phenol adsorption (76%) was achieved with IRA96 polar resin. Conversely, non-polar adsorbents allowed higher desorption ratios. Almost 60% of the overall phenols originally occurring in the applied mix- ture were recovered by employing ENV+ and ethanol as the desorbing phase. Lower performances were achieved with the other recovery and desorption agents. The compound polarity generally influenced the adsorption ratios (the sorption capacities of non-polar resins increased by decreasing the compound polarity, and vice versa), while the desorption ones were not always affected by such a compound feature. These findings are of special interest in the perspective of developing an effective SPE procedure for the recovery of natural phenols from real OMWs. © 2010 Elsevier B.V. All rights reserved. 1. Introduction Olive mill wastewater (OMW) is one of the most environ- mentally concerning agrochemical waste of the Mediterranean area because of its high COD content, chemical features, high and seasonal productions and the typical fractionation of olive oil industries [1]. A relevant fraction of the OMW organic matter is constituted by phenolic compounds (up to 10 g L -1 [1]), which are able to exert antimicrobial [2,3] and phytotoxic [4–6] activities. Detrimental effects of OMW phenols versus pluricellular organisms belonging to different trophic levels were reported, too [7]. Despite such findings, no dedicated EU legislation currently regulates OMW disposal, and land spreading is allowed in Italy (i.e., one of the main olive oil producing country), even if subject to limitations [8]. On the other hand, due to their antioxidant activities [9–12], natural polyphenols are very interesting molecules for several industrial applications, mainly concerning the cosmetic [13,14] ∗ Corresponding author. Tel.: +39 051 2090317; fax: +39 051 2090322. E-mail addresses: francesco.ferri1@gmail.com (F. Ferri), lorenzo.bertin@unibo.it (L. Bertin), alberto.scoma2@unibo.it (A. Scoma), leonardo.marchetti@unibo.it (L. Marchetti), fabio.fava@unibo.it (F. Fava). and the food preservation and formulation [9,15–17]. Further- more, OMW phenol employment for medical proposals represents a fast developing research area [18]: the intake of specific phenolic molecules was correlated to the reduction of the oxidation of Low- Density Lipoprotein (LDL) [19,20], which is one among the main risk factors able to induce arteriosclerosis. Natural polyphenols can also decrease inflammation processes by reducing Leukotriene B4 production [21], and, importantly, were demonstrated to signifi- cantly reduce DNA oxidation, which is considered to be a crucial step in human carcinogenesis [22]. Thus, the recovery of pheno- lic compounds from OMWs appears of great interest since it could conjugate the reduction of the waste toxicity to the obtainment of high-added value molecules. Several studies addressed to improve the recovery and purifi- cation of chemicals from complex natural matrices are in progress [23–25]. Concerning the recovery of polyphenols from OMWs, membrane processes [7,26–28] and liquid-liquid extraction [10,29,30], eventually improved by the employment of surfactants [31], are the techniques so far most proposed. Solid phase extrac- tion (SPE) can represent a feasible alternative, because it relies on relatively low costs, high recovery yields and simple procedures [32]. However, most of phenol adsorption processes applied so far on OMWs were addressed to the wastewater decontamina- 1385-8947/$ – see front matter © 2010 Elsevier B.V. All rights reserved. doi:10.1016/j.cej.2010.11.090