Exploring the pressurized heterogeneous electro-Fenton process and modelling the system

Abstract

• Hydrogen peroxide electrogeneration was boosted with the application of pressure. • Clofibric acid abatement was significantly enhanced with pressurized electro-Fenton. • Specific energy consumption was reduced when working above atmospheric pressure. • Pressure did not affect leaching nor damaged the heterogeneous catalyst. • Mathematical modelling based on experimental data represented the system behavior. In this research, a bench-scale installation was tested for the heterogeneous electro-Fenton treatment of clofibric acid. The setup consists of a pressurized flow-through electrochemical cell equipped with a catalyst fluidized-bed and aerated with a jet mixer. The novelty of the research is two-fold: the use of the pressurized-jet aerator on an electro-Fenton treatment is tested and it is one of the first studies combining pressure with heterogeneous catalysis in electro-Fenton. Moderate relative pressures, up to 2 bar, were analyzed. Initially, the electrogeneration of hydrogen peroxide was tested, showing that it is remarkably boosted by the application of pressure. Then, the elimination of clofibric acid by means of an electro-Fenton treatment was carried out at 0.12 and 0.25 A, using iron-containing alginate beads as the catalyst. Regardless of the current intensity, the increase from atmospheric pressure to 1 gauge bar boosted the elimination of the pollutant and reduced the specific energy consumption of the electrochemical cell. Specifically, at 0.25 A an abatement higher than 98% was achieved in 8 h at atmospheric pressure while only 1 h was required at 1 bar of gauge pressure. However, a further increase of the pressure to 2 bar did not report a major improvement. Moreover, the effect of pressure on the catalyst was analyzed, concluding that the integrity of the alginate beads was not compromised by pressure. In fact, the iron leaching was very similar at 0, 1 and 2 bar: around 30% after 8 h of treatment. Finally, a mathematical model was developed, using the experimental data to obtain the necessary fitting parameters, which allowed to understand better the behavior of the bench-scale reaction system.