Agrowaste with antioxidant properties as intercalating agents for LDH

The exploitation of biowastes for the production of bio-based chemicals, materials or fuels has been recently fostered to the purpose of converting an environmental and economical concern into an industrial opportunity. Biowastes in fact, in most cases are rich in organic molecules as for example the olive mill wastewater (OMW), an aqueous waste released from the production of virgin olive oil. OMW typically contains a wide range of polyphenols, which are natural antioxidants and may be present up to 10 g L-1. After recovering, such antioxidant molecules can be exploited for cosmetic and food applications [1]. However, the recovery implies the use of biotechnological processes and the operating costs must be taken into consideration. Anionic clays or layered double hydroxides (LDHs) are versatile and multifunctional materials, thanks to their easiness of scaling-up preparation and functionalization through one pot synthesis, tunable composition and biocompatibility. LDHs indeed, are advantageous in many field of application as catalysts, catalyst precursors, anion exchangers, additives and/or stabilizers in polymer formulations, sorbents and scavengers for pollutants, thus revealing an essential role also in environmental remediation [2-3]. In the present work, the idea is to intercalate an agrowaste into an LDH with the aim of decreasing the environmental impact of such biowaste and to exploit the antioxidant properties of the polyphenols present, such as p-coumaric acid, syringic acid, ferulic acid, vanillic acid, 3,4-dihydroxybenzoic acid, etc. and then to further exploit such organo-modified LDH in a polymer composite. Hence, the final material would be of great interest thanks to its multifunctionality. It is well-known in fact that the organic functionalization of LDH induces a strong interaction at the interface filler/polymer through its tethered molecules, with consequent notable boosting in mechanical performances. Moreover, being the modifier antioxidant, such property is potentially preserved into the composite. In view of these considerations, olive mill wastewater has been used as intercalating agent in Zn2Al-LDH and, for comparison, some model systems have been also prepared through the intercalation of some antioxidant molecules, chosen among those potentially present in OMW. The organo-modified LDHs have been employed for the preparation of poly(butylene succinate) (PBS) composites trough in situ polymerization. Both clays and composites have been studied in terms of molecular, morphological and chemical characteristics by GPC, XRD and FT-IR. Thermal properties have been investigated by TGA and DSC. Viscoelastic and antioxidant properties have been also assessed.