New insight into degradation of chloramphenicol using a nanoporous Pd/Co 3 O 4 cathode: characterization and pathways analysis.

The growing chloramphenicol (CAP) in wastewater brought a serious threat to the activity of activated sludge and the spread of antibiotics resistance bacteria. In this study, a highly ordered nanoporous Co 3 O 4 layer on Co foil through anodization was prepared as cathode for nitro-group reduction and electrodeposited with Pd particles for dechlorination to reduce CAP completely. After 3 h treatment, almost 100% of CAP was reduced. Co 2+ ions in Co 3 O 4 served as catalytic sites for electrons transfer to CAP through a redox circle Co 2+ -Co 3+ -Co 2+ , which triggered nitro-group reduction at first. With the presence of Pd particles, more atomic H* were generated for dechlorination, which increased 22% of reduction efficiency after 3 h treatment. Therefore, a better capacity was achieved by Pd/Co 3 O 4 cathode ( K  = 0.0245 min -1 , K is reaction constant) than by other cathodes such as Fe/Co 3 O 4 ( K  = 0.0182 min -1 ), Cu/Co 3 O 4 ( K  = 0.0164 min -1 ), and pure Co 3 O 4 ( K  = 0.0106 min -1 ). From the proposed reaction pathway, the ultimate product was carbonyl-reduced AM (dechlorinated aromatic amine product of CAP) without antibacterial activity, which demonstrated this cathodic technology was a feasible way for wastewater pre-treatment.