Influence of the doping level of boron-doped diamond electrodes in the electrooxidation of polystyrene nanoplastics

Abstract

[EN] Microplastics and nanoplastics have arisen as contaminants of emerging concern due to the wide use of plastics, and the application of boron-doped diamond (BDD) electrodes for their removal is promising. In this study, we report the influence of BDD doping levels (500, 2500, and 10000 ppm B doping) on the electrooxidation of polystyrene nanoplastics (100 nm, 20 mg¿L-1). Different current densities (50, 25, 12.5, and 5 mA¿cm¿ 2 ) have been applied to determine the best electrolysis conditions for each electrode type. In addition, hydroxyl radical (¿OH), persulphate (S2O8 2-), and hydrogen peroxide (H2O2) reactive species have been determined to understand the influence of the species generated on the degradation of NPs. BDD500 electrode presents the fastest degradation of PS NPs at low current densities (12.5 and 5 mA¿cm¿ 2 ), BDD2500 at 25 mA¿cm¿ 2 , and BDD10000 at 50 mA¿cm¿ 2 . Among oxidative species determined, S2O8 2- is the one generated with the highest concentration and seems to command the degradation of PS NPs, since at 25, 12.5, and 5 mA¿cm¿ 2 , the electrodes that produce more S2O8 2- degrade faster PS NPs. At 50 mA¿cm¿ 2 , the differences between the different electrodes were minimal. The highest mineralization (as measured by non-purgeable organic carbon measurements) was obtained for BDD500 at 50, 25, and 12.5 mA¿cm¿ 2 , and BDD2500 at 5 mA¿cm¿ 2 .