Model accounting for the Cr(III) electroprecipitation kinetics in an electrochemical reactor based on CFD and mass transport contributions

[Display omitted] •Phenomenological theoretical model of Cr electroprecipitation in synthetic solution.•Model accounts for kinetics, momentum and mass transfers in the reactor.•Model describes experimental Cr removal at 10 and 30 mA cm−2.•Improvements of reactor configuration are suggested relying on simulations. The present research proposes a comprehensive kinetic model for chromium removal in synthetic tannery wastewater using an electroprecipitation process. The experimental process is conducted in a rotating cylinder electrode reactor (batch) using TiO2/RuO2 as cathodes, and AISI 1018 carbon steel as anode releasing iron species which induce the electroprecipitation. The theoretical analysis considers the simultaneous solution of the Reynolds averaged Navier-Stokes (RANS), and kinetic-based mass conservation equation to describe the distribution of ionic species inside the reactor. The electrode kinetics describing the flux production of Fe2+ species on the anode is also considered under full electrokinetic control conditions (secondary current distribution). The model proposed here can explain the experimental Cr3+ and Fe2+ concentration profiles, as a function of RCE rotation rate and applied current density; and it reveals that the chemical homogeneous precipitation of iron chromite is the most predominant reaction, compared to other precipitation contributions. Kinetic and transport parameters are determined by the fitting of the model to experimental data. Rationalization of the electroprecipitation reactor design can improve the contact between electrogenerated Fe2+ and Cr3+ in the effluent, to optimize its removal through the manipulation of operating conditions (e.g. mixing, current density, electrode configuration).