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In this study, a first approach to model drop size distributions in agitated nanoparticle-stabilized liquid/liquid systems with population balance equations is presented. Established coalescence efficiency models fail to predict the effect of steric hindrance of nanoparticles at the liquid/liquid interface during the film drainage process. A novel modified coalescence efficiency is developed for the population balance framework based on the film drainage model. The elaborate submodel considers the desorption energy required to detach a particle from the interface, representing an energy barrier against coalescence. With an additional implemented function in the population balance framework, the interface coverage rate by particles is calculated for each time step. The transient change of the coverage degree of the phase interface by particles is thereby considered in the submodel. Validation of the modified submodel was performed with experimental data of agitated water-in-oil (w/o) dispersions, stabilized by well-defined spherical silica nanoparticles. The nanospheres with a size of 28 nm are positively charged and were hydrophobized by silanization with dimethyloctadecyl[3-(trimethoxysilyl)propyl]ammoniumchloride. This modeling approach is a first step toward predicting time-resolved dynamic drop size distributions of nanoparticle-stabilized liquid/liquid systems. [ABSTRACT FROM AUTHOR]

This work addresses the influence of partially hydrophobic aluminum particles on the interfacial properties of o/w and w/o dispersions. For this purpose, drop size distributions are determined in an agitated tank followed by batch settling experiments after stirrer stop. In presence of hydrophobized aluminum particles, the type of dispersion (o/w or w/o) has an unexpected influence on coalescence behavior. Particles accelerate the coalescence for o/w dispersions (low oil fraction) but hinder the coalescence for w/o dispersions (high oil fraction). For a deeper understanding of this effect, an in-depth characterization and comparison of the drop size distributions of the two dispersion types was performed. [Display omitted] • Aluminum particles induce opposing coalescence behavior in o/w and w/o dispersions. • Endoscope technique can track transient changes in particle-stabilized drop size. • Batch settling experiments are a useful tool to characterize coalescence behavior. [ABSTRACT FROM AUTHOR]

• First comparative study on filtration of particle/oil suspensions, o/w and w/o PE. • Gelling of particles can significantly improve filtration performance. • Possible enhancement of membrane performance after particle contact with membrane. • w/o PE show disproportionate increase of permeability. • Membrane pre-treatment: higher permeability and linear increase of flux with pressure. 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. [ABSTRACT FROM AUTHOR]