Nanoplastics mineralization by the intensified photo-Fenton process

The widespread presence of microplastics (MPs) and nanoplastics (NPs) in aquatic systems has become one of the most challenging environmental issues nowadays. Although advanced oxidation processes (AOPs) have been widely studied for the treatment of persistent contaminants in water, their application for MPs and NPs removal have been scarcely addressed. In this study, the degradation of polystyrene NPs of different sizes (909 nm and 140 nm) by intensified photo-Fenton oxidation has been evaluated. The degradation experiments (6 hours) were carried out at 80ºC and pH0=3 in a pyrex glass reactor, using an initial NPs concentration of 20 mg/L. The initial concentrations of H2O2 and Fe3+ were set at 130 mg/L and 10 mg/L, respectively, introducing additional doses of H2O2 to enhance the oxidation yield. Firstly, photolysis was evaluated, demonstrating that NPs are poorly degraded only by irradiation (8% mineralization). The addition of H2O2 (UV/H2O2 treatment) significantly improved the mineralization of NPs (53% mineralization regardless NP size). Finally, by the intensified photo-Fenton reaction, using Fe salts as catalyst, almost complete mineralization was achieved with both NPs (82% and 94% with NP size of 909 nm and 140 nm, respectively). These results are very promising for the elimination of plastic waste in water.