A study on structural evolution of hybrid humic Acids-SiO2 nanostructures in pure water: Effects on physico-chemical and functional properties. (January 2022)

• Record Type: Journal Article
• Authors: Venezia, Virginia; Pota, Giulio; Silvestri, Brigida; Vitiello, Giuseppe; Di Donato, Paola; Landi, Gianluca; Mollo, Valentina; Verrillo, Mariavittoria; Cangemi, Silvana; Piccolo, Alessandro; Luciani, Giuseppina
• Is Part Of: Chemosphere. Volume 287:Part 1(2022)
• Publication Date: 2022-01
• Subjects: Humic acids (HA) -- Biowastes -- Antioxidant properties -- Hybrid nanoparticles -- Aging -- Supramolecular reorganization; Pollution -- Periodicals; Pollution -- Physiological effect -- Periodicals; Environmental sciences -- Periodicals; Atmospheric chemistry -- Periodicals; 551.511
• DOI: 10.1016/j.chemosphere.2021.131985
• Languages: English
• ISSNs: 0045-6535

Abstract

Abstract: Humic acids (HA) are considered a promising and inexpensive source for novel multifunctional materials for a huge range of applications. However, aggregation and degradation phenomena in aqueous environment prevent from their full exploitation. A valid strategy to address these issues relies on combining HA moieties at the molecular scale with an inorganic nanostructured component, leading to more stable hybrid nanomaterials with tunable functionalities. Indeed, chemical composition of HA can determine their interactions with the inorganic constituent in the hybrid nanoparticles and consequently affect their overall physico-chemical properties, including their stability and functional properties in aqueous environment. As a fundamental contribution to HA materials-based technology, this study aims at unveiling this aspect. To this purpose, SiO2 nanoparticles have been chosen as a model platform and three different HAs extracted from composted biomasses, manure (HA_Man), artichoke residues (HA_Art) and coffee grounds (HA_Cof), were employed to synthetize hybrid HA-SiO2 nanoparticles through in-situ sol-gel synthesis. Prepared samples were submitted to aging in water to assess their stability. Furthermore, antioxidant properties and physico-chemical properties of both as prepared and aged samples in aqueous environment were assessed through Scanning Electron Microscopy (SEM), N2 physisorption, Simultaneous Thermogravimetric (TGA) and Differential Scanning Calorimetric (DSC) Analysis, Fourier Transform Infrared (FT-IR), Nuclear Magnetic Resonance (NMR), Electron Paramagnetic Resonance (EPR) spectroscopies. The experimental results highlighted that hybrid HA-SiO2 nanostructures acted as dynamic systems which exhibit structural supramolecular reorganization during aging in aqueous environment with marked effects on physico-chemical and functional properties, including improved antioxidant activity. Obtained results enlighten a unique aspect of interactions between HA and inorganic nanoparticles that could be useful to predict their behavior in aqueous environment. Furthermore, the proposed approach traces a technological route for the exploitation of organic biowaste in the design of hybrid nanomaterials, providing a significant contribution to the development of waste to wealth strategies based on humic substances. Graphical abstract: Image 1 Highlights: Ceramic templated approach allows to obtain hybrid nanostructures with a good colloidal and chemical stability in water. Z-potential, FT-IR and EPR evidence suggest that SiO2 _HA NPs undergo HA structural reorganization during aging in water. HA structural reorganization in water involves their supramolecular structure, improving antioxidant activity in aged samples. HA reorganization depends on hydrophobicity index and carboxylic moieties, which enable tight binding to inorganic component. The antioxidant activity of SiO2 _HA_Man is stable, while that of SiO2 _HA_Art and SiO2 _HA_Cof increases during aging in water.