Photocatalytic degradation of antibiotics by N-doped carbon nanoflakes-nickel ferrite composite derived from algal biomass.

This work reports the synthesis of nickel ferrite (NiFe) nanoparticles, N-doped mesoporous carbon nanoflakes (NCF) and novel nickel ferrite-carbon nanoflakes (NiFe@NCF) nanocomposite using solvothermal method. NCF was derived from a cyanobacterial consortium consisting of Anabaena, Lyngbya and Weistiellopsis, rich in carbon and nitrogen. The synthesized nanoparticles were used as heterogeneous photocatalyst for degradation of two harmful water pollutants, ciprofloxacin (CIP) and levofloxacin (LEV). 99.91% LEV and 98.86% CIP were degraded within 50 and 70 min of visible light irradiation using NiFe@NCF following pseudo first order kinetics. This improved efficiency of the nanocomposite may be attributed to its higher surface area, reduction of band gap (from 2.42 to 2.19 eV), more active sites as well as charge carrier mobility with decreasing agglomeration tendency of the magnetic nickel nanoparticles upon being embedded on NCF. N-doping improves light harvesting property, retards charge recombination and extends as well as delocalises ᴨ-conjugated system resulting in enhanced photocatalytic activity. The scavenging experiments and EPR analysis reveal that O₂^-• and •OH are the main active species taking part in the degradation process. The material performs well within a wide range of pH and can be effectively used up to 5 repetitive cycles. A feasible photocatalytic degradation mechanism of the antibiotics against NiFe@NCF nanocomposite is also put forwarded along with their possible degradation pathways from LCMS studies.