Electro-Fenton removal of polystyrene nanoplastics from urban treated wastewater using a biodegradable iron chelating...

Nanoplastics in urban treated wastewater represent an emerging environmental challenge due to their colloidal stability and resistance to conventional treatment processes. This work investigates the role of electrogenerated hydrogen peroxide in the degradation of polystyrene NPs in synthetic urban treated wastewater. Three electrochemical configurations were evaluated: electrochemical oxidation with cathodic H₂O₂ electrogeneration (EO-H₂O₂), electro-Fenton (EF) at acidic pH, and EF at near-neutral pH using Fe(III)-EDDS as an iron chelating agent. The carbon felt cathode achieved the highest performance in the EO-H₂O₂ system, removing 78.75% TOC at 0.75 kWh gTOC^-1. Under acidic EF conditions, NPs adsorbed onto the CF surface, as confirmed by SEM imaging and organic carbon monitoring, complicating the assessment of true degradation efficiency. The EF-EDDS system at circumneutral pH simultaneously overcame this limitation. It achieved superior performance, with minimum NPs elimination values of 51%, 86%, and 91% at 0.1, 0.3, and 0.5 A, respectively, corresponding to TOC removals of 75.8%, 88.8%, and 91.6%. TEM analysis indicated significant structural degradation and reduction in particle abundance after treatment. The EF-EDDS system achieved specific energy consumptions of 0.10-0.87 kWh gTOC^-1, representing a reduction of up to 14-fold compared to conventional electrochemical oxidation applied to the same wastewater matrix under comparable conditions, and showing lower specific energy consumption and higher mineralization than the literature systems included in the comparison, while recognizing the differences in reactor configuration, operating conditions and wastewater composition. Validation with real wastewater effluents is nevertheless required to confirm the generalizability of these findings.