Energy consumption and reaction rate optimization combining turbulence promoter and current modulation for electrochemical mineralization

Abstract

• Distinct turbulence promoters were assessed for the electrooxidation of phenol. • Plastic mesh and reticulated vitreous carbon performed equally well to degrade phenol. • Combined modulated and constant current modes led to higher mineralization efficiency. • Use of turbulence promoters and modulated current led to a shorter treatment time. • Low energy consumption and treatment cost were also obtained for this new setup. Electrooxidation stands out as a promising technique for treating effluents containing toxic organic compounds. However, the high energy consumption remains an obstacle to its large-scale application. The aim of this work was to optimize the electrooxidation process by combining current modulation, where the applied current was maintained close to the limiting value, with turbulence promoters (TPs) to improve the mass transfer, consequently shortening the mineralization time. Electrooxidation was performed in an electrochemical flow reactor, with phenol selected as a model compound. A plastic mesh turbulence promoter (MTP) and reticulated vitreous carbon (RVC) were evaluated as TPs. The combined approach enabled reduction of the energy consumption from 168 ± 31 kWh kg −1 TOC (galvanostatic mode) to 72 ± 6 kWh kg −1 TOC [modulated current (MC) + MTP]. Additionally, the improvement of the mineralization kinetics reduced the electrolysis time by ~30%. Under galvanostatic conditions, use of the RVC outperformed the mineralization performance observed using the MTP, but similar efficiency was observed applying the MC mode at low flow velocities. The results reinforced the potential of electrooxidation as an option for the treatment of effluents, paving the way to obtain a process with fast degradation kinetics and high mineralization efficiency, leading to low energy consumption.