Gold nanoparticles-based extraction of phenolic compounds from olive mill wastewater: A rapid and sustainable method

Olive Mill WasteWater (OMWW) is an important by-product of the Olive Oil production. Its high concentration in Phenolic Compounds (PC) gives OMWW antimicrobial and phytotoxic properties. The aim of this work is to develop a rapid, simple and sustainable method based on the use of gold nanoparticles (AuNPs) chosen to extract PC from OMWW. AuNPs can be used taking advantage of their unique surface properties and high surface/volume ratio. They also offer high stability, easy chemical synthesis and use of water or eco-friendly solvents for their synthesis procedures. Two different stabilizing layers were used on the AuNPs surface: Cysteamine hydrochloride (Cys), and 4,4’’- dithiolterphenyl (TR) obtaining AuNPs-Cys and AuNPs-TR, respectively. The extraction with AuNPs-Cys achieved 70% of the PC present in OMWW, allowing to make the by-product available for land fertilization and giving the possibility to use PC for other aims, as nutraceutical, active packaging, cosmetic or pharmaceutical.