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 processes. A better understanding of the complexity of lignin as a raw material is necessary for creating new sustainable value chains, and a deeper understanding of the forces and interactions driving the self-assembly of lignin nanoparticles (LNPs) is required to create new, more advanced lignin nanomaterials. In the current study, “a library” of LNPs made from both softwood (spruce) and hardwood (eucalyptus) lignins was prepared utilizing green solvents-fractionated kraft lignins with narrow structural and molecular weight dispersity, and the LNPs were thoroughly characterized with respect to their size, shape, and surface properties. For both spruce and eucalyptus lignin fractions, the size of the LNPs decreased with increasing M_w with a decreasing number of phenolic hydroxyls and an increasing number of aliphatic hydroxyl units in the lignin fraction. The diameter of the LNP's could be varied between 80 and 500 nm, depending on the M_w of the initial lignin and its concentration. The number of methoxy and phenolic groups in the aromatic ring, the aliphatic hydroxyls and β-O-4 bonds in side chains in lignin fractions affect the morphology and surface structure of the LNPs to a significant degree. The LNP's with shapes ranging from doughnut-like structures to filled interconnected spheres were prepared, depending on the type of lignin phenylpropanoid units (botanical origin), concentration, and other properties of the lignin fractions. The identified strong dependence of the properties of the LNPs on the inherent properties of the lignin from which they were derived reveals that it is of crucial importance to select the appropriate starting lignin materials for the controlled design and synthesis of LNPs. This reduces costs for the subsequent purification and further processing of the LNPs, and prevents environmental pollution by minimizing the usage of resources. The obtained knowledge provides a clear guideline for the design of new biomass-based materials.

The synthesis of the chitosan/magnetite nanocomposites is presented. Composites were prepared by co-precipitation of iron(II) and iron(III) salts by aqueous ammonia in the 0.1 % chitosan solution. It was shown that magnetite synthesis in the chitosan medium does not affect the magnetite crystal structure. The thermal analysis data showed 4.6 % of mass concentration of chitosan in the hybrid chitosan/magnetite composite. In the concentration range of initial Gd-DTPA solution up to 0.4 mmol/L, addition of chitosan to magnetite increases the adsorption capacity and affinity to Gd-DTPA complex. The Langmuir and Freundlich adsorption models were applied to describe adsorption processes. Nanocomposites were characterized by scanning electron microscopy (SEM), differential thermal analysis (DTA), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and specific surface area determination (ASAP) methods.