Degradation of trichloroacetic acid by MOFs-templated CoFe/graphene aerogels in peroxymonosulfate activation

Integrating transition-metal and nitrogen into carbon-based materials have been attracted considerable attention in peroxymonosulfate (PMS) activation, but it is a great challenge to establish strong interactions between metal species and graphene. Here, we established metal–organic frameworks (MOFs)-hydrogels which acted as templates to form a family of FeCo/graphene aerogels (C-FeCo, C-CoMIL and C-FeZIF). The C-FeZIF, which co-doped Fe/Co and nitrogen into graphene aerogel, exhibited the most regular and stable metallic frameworks, the best crystallization and biggest pore sizes; it also showed the highest efficiency and stability in PMS catalysis for trichloroacetic acid (TCAA) degradation among these aerogels. By comparative analysis on different catalysis conditions (including catalyst dosage, PMS concentrations and reaction pH), 1 g/L C-FeZIF with 4 mM of PMS reacting under pH 5 showed to be the optimum conditions with an 81.2% removal of TCAA in 160 min. Meanwhile, the C-FeZIF/PMS system also performed well in TCAA degradation within a wide pH range from 3 to 9. Radical analysis suggested that 1O2 was the main active species produced in the C-FeZIF/PMS system, while both SO4•- and •OH radicals assisted the catalytic process to a certain extent. The synthesis process is environmentally friendly, easy to carry out, safe and stable with no secondary pollution, which could be scaled up easily for catalyst preparation for water treatment.