Electrocoagulation of polyester microplastics in organic-rich effluents: Performance, operating cost, and sludge generation

This study evaluated the influence of organic matter and operating conditions on the electrocoagulation removal of polyester microplastics (MPs) from a synthetic effluent. The effluent contained polyester MPs, sodium sulfonate, NaCl as supporting electrolyte, and a soluble organic amendment. A batch electrocoagulation system with aluminum electrodes was used. A full factorial design was first applied to identify the most influential parameters, followed by a Box–Behnken design to optimize the simultaneous removal of MPs and organic matter (OM). Screening experiments showed high MPs removal efficiencies, ranging from 88.1% to 99.8%, with initial OM concentration, initial MPs concentration, and operating time identified as the dominant factors. During optimization, MPs removal ranged from 76.6% to 98.3%, whereas OM removal, expressed as chemical oxygen demand (COD), ranged from 23.4% to 41.4%, indicating greater efficiency for particulate MPs separation than for dissolved OM removal. The optimal conditions were 700 mg L⁻¹ MPs, 28.64 min, and 1500 mg L⁻¹ COD, achieving predicted removals of 94.85% MPs and 41.06% OM. The partial operating cost was 4.73 US$ m⁻³, and sludge generation reached 3.52 kg m⁻³. Further studies using real wastewater matrices are recommended to validate process performance and support scale-up.