Super-amphiphilic graphene promotes peroxymonosulfate-based emulsion catalysis for efficient oil purification

Oil fractions containing highly toxic and hazardous organic contaminants can not only cause severe environmental disasters, but also an undesired waste of resources. Given the exceptional performance of persulfates in the removal of persistent and refractory organic pollutants from aqueous media, herein, a peroxymonosulfate-based Pickering emulsion catalytic (PPEC) system was constructed for the hazardous oil purification, using super-amphiphilic graphene as a solid emulsifier and a heterogeneous catalyst simultaneously. Combined detailed instrumental analysis with theoretical calculations, we find that the incorporation of pyridinic N and its oxide significantly facilitated the formation of super-amphiphilic graphene and successfully induced the formation of Pickering emulsion. In addition to stabilizing the PPEC system, super-amphiphilic graphene can also achieve efficient removal of Sudan III (simulated lipophilic organic pollutant) by activating peroxymonosulfate (PMS) to generate •O2- and 1O2. Results showed that 80 mg/L Sudan III (20 mL) could be fully degraded within 30 min using 10 mL 5 mmol PMS. More significantly, our proposed PPEC system also exhibited excellent property in the purification of practical waste engine oil. This study provides new insights into the purification and recovery of waste oil.