Towards a high yield recovery of polyphenols from olive mill wastewater on activated carbon coated with milk proteins: Experimental design and antioxidant activity

Abstract

Activated carbon coated with milk proteins was used for the removal and recovery of phenolic compounds from actual olive mill wastewater (OMW). The extraction of polyphenols using the new adsorbent based on natural coating agent has significant potential compared with traditional extraction methods, as it significantly increases the extraction yield (80%) and overall efficiencies of the process for total phenols (75.4%) and hydroxytyrosol (90.6%) which is the most valuable compound. Complete discussions on the adsorption isotherms, kinetic and thermodynamic were performed and the optimum adsorption variables were investigated using the response surface methodology and the central composite experimental design. The extracted polyphenols exhibited a high antioxidant activity and a fast scavenging effect on DPPH free radical. The strategy devised in this work for polyphenol extraction using modified activated carbon with biological coating agent is of simple design, very effective and ensure the recovery of highly antioxidant extract.

Keywords: Adsorption equilibrium; Antioxidant activity; Biological coating; Experimental design; OMW polyphenols.