Solid-liquid equilibria in mixtures of iron(III) nitrate nonahydrate and ethanol or 1-propanol

Abstract

Solutions of iron(III) nitrate nonahydrate (INN) in ethanol and 1-propanol are interesting starting materials for producing iron oxide nanoparticles by spray flame synthesis. For the design of these processes, it is important to have information on solid-liquid equilibria (SLE) in these solutions. As corresponding data were not available in the literature, we have studied the SLE of solutions of INN in ethanol and 1-propanol experimentally at temperatures between 288.15 and 308.15 K at 101.3 kPa. Unexpected phenomena occur in these solutions: one would expect an increasing amount of precipitate upon increasing the concentration of the salt INN, but the reverse behavior is observed for a wide range of states. This is caused by chemical reactions in the solutions: not INN, but iron(III) hydroxide (IH) precipitates from the solution, leading also to a strong acidity of the mixture. These chemical effects are taken into account in a physico-chemical model that was developed for describing the SLE in the studied systems. In that model, the physical non-ideality is described with the extended Pitzer model.