In recent years, Pickering emulsions (PE) have become of increasing interest for their application in (bio-) catalytic multiphase processes. To design an economically feasible process, an efficient and effective catalyst recovery is necessary. Ultrafiltration of PE has been shown to be a promising procedure. In this work, the influence of drop size distributions and rheology on the ultrafiltration of water-in-oil and oil-in-water PE stabilized by different nanoparticles as well as organic solvent-nanoparticle suspensions was studied.
Particles with higher hydrophobicity led to larger Sauter mean diameters. Depending on the ability of silica particles to form three-dimensional network structures, shear thinning or Newtonian rheological behavior was obtained. When suspensions of particles with gelling properties were filtered, an increase in flux compared to the filtration of the pure organic solvent was observed. Water-in-oil PE showed – regardless of investigated particle type and concentration – a disproportionate increase of flux with pressure. However, adjusting the membrane pre-treatment procedure led to a linear dependency between flux and pressure, which was also observed for oil-in-water PE (without special pre-treatment).
This work shows that the ultrafiltration of PE made from various nanoparticles is possible and contributes to a better understanding of PE characteristic properties and their influence on the ultrafiltration behavior.