Photocatalytic degradation of gemifloxacin antibiotic using Zn-Co-LDH@biochar nanocomposite

Heterogeneous photocatalysis using Zn-Co-LDH@BC nanocomposite for degradation of GMF. [Display omitted] •Hydrothermal preparation of novel and efficient Zn-Co-LDH@BC photocatalyst.•Superior photocatalytic activity of Zn-Co-LDH@BC for degradation of gemifloxacin.•High mineralization efficiency of gemifloxacin using Zn-Co-LDH@BC photocatalyst.•A plausible degradation pathway for photocatalytic degradation of gemifloxacin.•Reusability of Zn-Co-LDH@BC catalyst after five photocatalysis run. The aim of the present study was to investigate the photocatalytic performance of biochar (BC)-incorporated Zn-Co-layered double hydroxide (LDH) nanostructures in gemifloxacin (GMF) degradation as a model pharmaceutical pollutant. The as-prepared Zn-Co-LDH@BC showed high photocatalytic efficiency due to the enhanced separation of photo-generated charge carriers using cobalt hydroxide as well as inhibiting the agglomeration of LDH nanostructures by incorporation of BC. According to the results, 92.7% of GMF was degraded through photocatalysis in the presence of Zn-Co-LDH catalyst. The photocatalytic performance of BC-incorporated Zn-Co-LDH was highly dependent on the solute concentration and photocatalyst dosage. The addition of ethanol caused more inhibiting effect than that of benzoquinone (BQ), indicating the major role of •OH in decomposition of GMF compared to the negligible role of O2•−. A greater enhancement in the photocatalytic degradation of GMF was obtained when the photoreactor containing Zn-Co-LDH@BC nanostructures was oxygenated. Less than 10% drop in the removal efficiency of GMF was observed within five successive operational runs. The results of chemical oxygen demand (COD) analysis indicated the COD removal efficiency of about 80% within 200 min, indicating the acceptable mineralization of GMF. The reaction pathways were also proposed for the photocatalytic conversion of GMF under UV light irradiation.