Microemulsion-assisted precipitation of particles: Experimental and model-based process analysis

The technical-scale production of nanoparticles with tailored properties is of particular interest due to the increasing demand from industry. This study provides the basis for the scale-up of the synthesis route in water-in-oil (w/o)-microemulsion droplets by a detailed experimental and theoretical analysis of the precipitation of calcium carbonate (CaCO3) and barium sulfate (BaSO4). The used w/o-microemulsion system consists of water, cyclohexane and the inexpensive technical surfactant Marlipal O13/40. This system was extensively characterized with and without reactants in order to identify stable microemulsion regions. Precipitation was initialized by mixing two microemulsions, each containing one of the reactants, in semi-batch operating mode. Extensive parameter studies helped to identify control parameters, which allow the tailored synthesis of nanoparticles with certain properties. For CaCO3 a dependence of the morphology on the reaction time can be observed. For BaSO4 it was found out that the final particle size can be controlled by varying the initial reactant concentration ratio.A deterministic population balance equation (PBE) model and a stochastic Monte-Carlo (MC) model were derived for the BaSO4 system. The calculation time of the discretized PBE model compared with the MC model is much faster, but the MC simulations show a better agreement of experimental and simulation data, especially the particle size distribution (PSD).