1 H liquid-state nuclear magnetic resonance (NMR) spectroscopy was applied for the first time to lignin nanoparticles (LNPs) in an aqueous suspension to study the surface composition of LNPs and to acquire a better understanding of the mechanism of their formation. A series of LNPs were prepared from spruce and eucalyptus kraft lignin fractions with narrow molecular weight distributions and functionalities. An NMR pulse program combining presaturation with excitation sculpting increased the signal resolution, making it possible to observe a superficial layer of LNPs directly in the aqueous suspension, "as prepared". The particle size, charge, and surface morphology were characterized by transmission electron microscopy (TEM) and dynamic light scattering (DLS). According to liquid-state NMR, methoxy groups from syringyl and guaiacyl units of lignin are the main groups present on the surface of LNPs. The presence of aliphatic moieties, mainly from side chains of lignin molecules, has also been confirmed. Taking into consideration the chemical composition of the lignin fractions, the structure of lignin NPs as shown by NMR spectroscopy and their size and surface charge, a pattern of lignin self-assembly into LNPs has been suggested.

A hybrid nanocomposite material has been obtained by in situ formation of an inorganic network in the presence of a preformed organic polymer. Chitosan biopolymer and tetraethoxysilane (TEOS), which is the most common silica precursor, were used for the sol-gel reaction. The obtained composite chitosan-silica material has been characterized by physicochemical methods such as differential thermal analyses (DTA); carbon, hydrogen, and nitrogen (CHN) elemental analysis; nitrogen adsorption/desorption isotherms, scanning electron microscopy (SEM); and Fourier transform infrared (FTIR) spectroscopy to determine possible interactions between silica and chitosan macromolecules. Adsorption of microquantities of V(V), Mo(VI), and Cr(VI) oxoanions from the aqueous solutions by the obtained composite has been studied in comparison with the chitosan beads, previously crosslinked with glutaraldehyde. The adsorption capacity and kinetic sorption characteristics of the composite material were estimated.

The use of lignin from forests as a renewable resource is a greener alternative to the petrochemical industry and accelerates the progress towards the development of more environmentally friendly industrial...