Outstanding productions of peroxymonosulfuric acid combining tailored electrode coating and 3D printing
M. Pilar Castro, Miguel Montiel, Ismael F. Mena, Jan Gäbler, Hunter King, Cristina Sáez, Manuel A. Rodrigo
Abstract
In this work, the combination of a tailored design of electrode and electrochemical cell to produce peroxymonosulfuric acid (PMSA), also known as Caro's acid, is evaluated. For the electrode, a customized coating of BDD was deposited onto a niobium substrate. This electrode exhibited a good reproducibility and efficiency in the production of PMSA, thus promoting direct oxidation of sulfuric acid into Caro's acid and preventing the action of scavengers. The electrochemical cell was manufactured after the application of computer-aided design (CAD) combined with computational fluid-dynamics (CFD) simulation and 3D printing. The prototype, with an area of 25sqcm and a designed flowrate of 48 L/h, has been characterized with the evaluation of mass transfer coefficients and RDT curves, which demonstrate an outstanding performance with mass transport coefficients over 3·10−5 m s−1 without turbulence promoter. The cell equipped with the electrodes was tested in the production of Caro's acid enabling a remarkable production of 200 mM of peroxymonosulfuric acid in discontinuous operation mode with a coulombic efficiency (57.2 %) and energy Efficiency (10.67 mmolA−1 h−1). These values outperform the previous state-of-the-art works done in the field for undivided cells operated in discontinuous mode. The results obtained were successfully fitted to a phenomenological model for the generation of Caro's acid.