Electrochemical Degradation Strategies for Polystyrene Microplastic: Current Trends and Future Prospects

Abstract

Polystyrene (PS) microplastic (MP) pollution is a major environmental issue due to its extensive use, persistence, toxicity and resistance to degradation. In aquatic ecosystems, PS-MP disrupt biodiversity, accumulate in marine organisms, and transport toxic pollutants, ultimately entering the food chain and posing serious ecological and health risks. Conventional removal methods, including filtration, flotation, coagulation, adsorption, and bioremediation, often struggle with inefficiencies, high costs, and secondary pollution. Likewise, degradation techniques such as biodegradation, photocatalysis, and thermal or chemical treatments face challenges related to effectiveness, prolonged treatment durations, and sustainability. Electro-oxidation (EO) has emerged as an efficient and advanced approach for PS-MP breakdown, leveraging reactive oxygen species (ROS) to achieve high removal rates with minimal environmental impact. This review explores recent progress in electrochemical degradation, emphasizing reactor design, electrode materials, operating conditions, mass transfer, mixing strategies, and temperature control. Additionally, degradation pathways and economic feasibility are critically examined. This study systematically evaluates EO performance, with removal efficiencies ranging from 28% to 90% over treatment durations of 3 to 72 hours. PS-MP sizes between 0.1 and 149 µm and concentrations from 10 to 2000 mg/L were assessed. Notably, the BDD anode with 0.03 M Na₂SO₄ as the electrolyte demonstrated superior efficiency, reinforcing its effectiveness in MP degradation. Key challenges and future research directions are discussed to improve EO's practical application. By addressing existing gaps and limitations, this review contributes to the development of sustainable solutions for mitigating PS-MP pollution and safeguarding aquatic ecosystems.