Optimizing Electrocoagulation for Polystyrene Microplastics Removal via Magnetic Separation

This study investigated the effectiveness of electrocoagulation (EC) using iron electrodes to treat pure water and secondary effluent water contaminated with microplastics (MPs), and specifically polystyrene (PS). This research characterizes the composition and structure of the sludge formed during EC at different current densities and electrolysis times via techniques such as infrared spectroscopy, X-ray diffraction, and Mössbauer spectroscopy. Special attention is given to the formation of magnetite, a magnetic compound critical for the rapid recovery of coagulated MPs. The findings demonstrate that at intermediate current densities (5 mA cm–2), EC effectively removes 100% of the MPs from distilled water containing 50 mg L− 1 PS within 5 min when a magnet is used to collect the precipitate. In contrast, EC-treated wastewater has a lower recovery rate of MPs, achieving only 40% removal after 30 min and 80% removal after 720 min. This reduced efficiency is attributed to the absence of magnetite formation and the presence of nonmagnetic compounds such as goethite and lepidocrocite. This study highlights the critical role of magnetite in the efficient recovery of MPs during EC. While EC is highly effective for pure water, the process requires optimization for wastewater treatment because of the different nature of the by-products formed. Magnetite formation is the key to 100% removal of microplastics by EC. The efficiency of microplastics removal by EC is increased with the use of a magnet. EC was optimized to remove PS at a concentration of 50 mg L− 1 at 5 mA cm− 2 for 15 min. Lepidocrocite formation in wastewater limits microplastics recovery efficiency.