Physicochemical and electrokinetic properties of silica/lignin biocomposites.

A new method of synthesis of novel composites obtained from silica and Kraft lignin has been proposed. Silica used in the study was obtained by three methods (hydrolysis and condensation of tetraethoxysilane, precipitation in a nonpolar and polar medium with the use of sodium silicate). To extend the possible range of applications, the silica was preliminary modified with N-2-(aminoethyl)-3-aminopropyltrimethoxsysilane, and finally it was modified with Kraft lignin earlier oxidised with sodium periodate (lignin bonded to SiO2 by covalent interactions). The products physicochemical and electrokinetic properties were thoroughly analysed. The dispersive properties and surface morphology were evaluated on the basis of particle size distributions and SEM images. The stability of dispersion in inorganic-organic systems were characterised on the basis of the zeta potential, whose value also permitted concluding on the interactions between colloidal molecules dispersed in water solutions. The products were subjected to elemental analysis to get percentage contents of N, C, H, S elements and were also characterised by XPS and FT-IR spectroscopy. Results of the study are of practical importance in prospective applications of SiO2/lignin biocomposites.