Degradation of polystyrene nanoplastics by photo-Fenton oxidation in water

ORTIZ, DAVID; MUNOZ, MACARENA; GARCÍA, JORGE; DI LUCA, CARLA; MARTÍNEZ DE PEDRO, ZAHARA; CASAS, JOSÉ A.; CARBAJO, JAIME

Congreso; MICRO2022; 2022

UNESCO

The increasing widespread presence of microplastics (MPs) and nanoplastics (NPs) inaquatic ecosystems represents one of the most challenging environmental concerns nowadays.Given their low chemical and biological reactivity, the removal of these solids by conventionaltreatments is highly limited, especially for smaller particles. Although advanced oxidationprocesses (AOPs) have been extensively studied for the treatment of persistent pollutants inwater, their application for MPs and particularly NPs removal have been scarcely addressed.In this study, the degradation of polystyrene NPs (140 nm) by photo-Fenton oxidation hasbeen evaluated. The degradation experiments (6 hours) were carried out at pH0=3 in a pyrexglass reactor, using an initial NPs concentration of 20 mg/L. Firstly, a screening of UV-basedtechnologies for the removal of NPs was investigated (UV, UV/H2O2 and photo-Fenton). Ascarce degradation yield (< 30%) was obtained while evaluating photolysis, demonstratingthat NPs are poorly degraded only by UV irradiation. The addition of H2O2 (UV/H2O2treatment) significantly improved the removal of NPs (53% mineralization). Finally, bythe photo-Fenton reaction, using iron salts as catalyst, almost complete mineralization wasachieved (> 95%). Afterwards, a complete operating conditions study was carried out toanalyze the impact of temperature (25-80 ºC), initial H2O2 dose (60-230 mg/L) and catalystconcentration (5-20 mg/L) on the photo-Fenton oxidation (standard conditions: tempera-ture = 25 ºC; (Fe3+) = 10 mg/L; (H2O2)0 = 130 mg/L, with additional doses of H2O2throughout the reaction). Remarkably, temperature did not significantly affect NPs degra-dation, reaching similar degradation values for the different temperatures studied. On theother hand, a higher oxidant concentration increased the initial degradation rate of the NPswhile the effect of the catalyst concentration is currently under study. All in all, this studyproves that photo-Fenton oxidation is a promising alternative for the removal of NPs fromwater.