Kinetics of the oxidation of formaldehyde in a flow electrochemical reactor with TiO2/RuO2 anode

This paper reports the electrochemical degradation of solutions containing formaldehyde by means of an electrochemical tubular flow reactor with a titanium anode coated with metal oxides (Ti/Ru0.3Ti0.7O2). Due to the simplicity and low molecular weight of the compound it was possible to achieve high mineralization rates; the oxidation reaction of formaldehyde as well as TOC and COD removal were controlled by mass transfer. For solutions with 0.4 g L−1 of formaldehyde, electrodegradation followed a pseudo first-order kinetics, and the mass transport coefficients were calculated. After the experiments, a 97% reduction of TOC was observed, and the final formaldehyde and COD concentrations were below the detection limit threshold. For solutions with 12 g L−1 of formaldehyde processed at 100 mA cm−2, a transition from a zero-order kinetics to a first-order kinetics started at the concentration for which the current density corresponded to the value of the limiting current.