Electrochemical and photoelectrochemical oxidation processes for polystyrene microplastic treatment: BDD anode vs Sb-doped SnO2 ceramic anode coated with a CdFe2O4 photocatalytic layer

This study evaluates the efficiency of electrochemical and photoelectrochemical oxidation for the degradation of polystyrene (PS) microspheres using two types of anode materials: a commercial boron-doped diamond (BDD) anode and a ceramic tin oxide anode doped with antimony coated with a photoactive cadmium ferrite (CdFe 2 O 4 ) layer. Experiments were conducted under different current intensities and illumination conditions to assess degradation efficiency. Both electrodes achieved significant PS removal, reaching up to 99% with the BDD anode and up to 96% with the cadmium ferrite anode under light exposure and 6 hours of treatment. The photoelectrochemical effect was evident in the cadmium ferrite system due to the photogeneration of additional oxidizing species under visible light. Kinetic parameters were calculated using nonlinear regression according to a modified Chamas model with a Monod-type saturation term. Mineralization was confirmed through total organic carbon analysis, and morphological changes were evidenced by scanning electron microscopy and Raman spectroscopy. The specific energy consumption (SEC) analysis revealed that, although the BDD anode exhibited higher efficiency at low applied current intensities, the cadmium ferrite anode represents a viable alternative due to its high removal efficiencies and energy consumption values comparable to those of the BDD anode at intermediate current intensities and due to its cost-effectiveness associated with its lower fabrication costs. These results highlight the potential of these ceramic anodes as a sustainable alternative for the treatment of wastewater containing microplastics. • Electrochemical and photoelectrochemical oxidation were applied for the degradation of PS microplastics. • Two anode materials were tested: commercial BDD anode and Sb-doped SnO₂ ceramic anode coated with Cd-Fe. • PS microplastics degradation efficiency reached up to 99% with BDD and 96% with Cd-Fe under visible light. • Morphological and structural degradation was confirmed by FESEM and Raman spectroscopy analysis. • Kinetic modeling using a modified Chamas model with Monod-type saturation described the degradation behavior. • The Cd-Fe ceramic anode showed competitive performance and lower operational costs compared to BDD.