Macroscale precipitation kinetics: towards complex precipitate structure design.

Producing self-assembled inorganic precipitate micro- and macro-structures with tailored properties may pave the way for new possibilities in, e.g., materials science and the pharmaceutical industry. One set of important parameters to maintain appropriate control over the yield falls in the frame of reaction kinetics, which affects the possible coupling between hydrodynamics and chemical reactions under flow conditions. In this study, we present a spectrophotometric method to experimentally determine the characteristic timescales of precipitation reactions. It is also shown that the nickel-oxalate model system - despite the fast chemical complexation equilibria taking place - can be kinetically described by either Classical Nucleation Theory or the classical homogeneous kinetics approach. The applicability of our results is illustrated via injection experiments intrinsically exhibiting coupling between chemistry and hydrodynamics. Therefore, we suggest that easy-to-handle power law functions may be applied to characterize the precipitation kinetics in flow systems.