Magnetically controlled liquid paraffin oil-in-water Pickering emulsion stabilized by magnetite/cellulose nanocrystals: Formation and Cr(VI) adsorption

Abstract

This paper has explored the formation, stability, surface properties, rheological characteristics and magnetic behavior of liquid paraffin oil-in-water Pickering emulsions stabilized by hybrid magnetite/cellulose nanocrystals (MCNC) with various concentrations of components. It was shown that the most resistant MCNC-stabilized emulsions are those containing 37–83 wt% of magnetite in the hybrid. Magnetite-stabilized emulsions are unstable and easily disintegrate. Basing on the findings of the potentiometric titration, the suggestion was made that coordination bonds appear in the internal Stern layer of the double electrical layer of cellulose nanocrystals (CNC) with positively charged magnetite particles. Dynamic viscosity of MCNC-stabilized emulsions is higher than that of CNC- and Fe3O4-stabilized emulsions. Increase in thixotropy index of emulsions is mostly associated with the zeta potential closing to zero values. MCNC-stabilized emulsions demonstrate higher capability to adsorb highly toxic compounds of Cr(VI), than the related MCNC hybrids because of larger quantity and better availability of adsorption active centers on the surface of particles during the formation of 2D structures on the surface of an oil drop.