The behaviour of a two-compartment stirred-tank electrochemical reactor with two anodic reactions and with continuous flows of both anolyte and catholyte

Abstract

A partial mathematical model is presented for a two-compartment electrochemical reactor when there is a steady flow into and out of each compartment and when both anolyte and catholyte are well mixed. Two simultaneous anodic reactions, the fast oxidation of ferrocyanide ions and oxygen evolution, together with cathodic hydrogen evolution are considered and both migration and diffusion of hydroxyl ions across the diaphragm are taken into account. The resulting differential equations relate the concentrations of hydroxyl ions in each compartment and anolyte ferrocyanide to time in terms of,inter alia, the total reactor current and the partial current for ferrocyanide oxidation. By using the measured variation of current with time from an experimental reactor operated at a constant voltage and estimating the ferrocyanide partial current the observed concentration-time variations can be matched with those obtained by numerical integration of the model equations. Data from a series of experiments have been analysed and the assumption of a constant partial ferrocyanide current over the duration of a run gives a satisfactory representation of the behaviour of the experimental reactor. Reasons for discrepancies are discussed.