Insight into the co-removal of Cu(II) and ciprofloxacin by calcite-biochar composite: Enhancement and competition

Abstract

The discharge of metals and antibiotics pose a serious risk to public health and environment. Gaining insight into the removal process is an imperative implication for comprehending environmental transformation of contaminants. In this study, a low-cost calcite-biochar (CAB) composite was prepared through a facial pyrolyzed process from shell waste for the removal of Cu(II) and ciprofloxacin (CIP) in single and mixed systems. CAB exhibited superior removal performance toward these two pollutants. In single system, CIP removal was adsorption coupled with flocculation and Cu(II) removal was adsorption combined with precipitation. The CIP removal followed the PSO kinetic and Freundlich isotherm model, while Cu(II) removal were better described by PSO kinetic and Langmuir isotherm model. In binary system, Cu(II) had an promotional and inhibitory effect on the removal of CIP, which depended on the concentration of Cu(II). But the adsorption capacity of Cu(II) removal was reduced with the existence of CIP. The microstructure analysis indicated that the cation bridging, hydrogen bonding, surface complexation and π-π interaction were attributed to the CIP removal and Cu(II) could act as a bridge or competitor. While the Cu(II) removal was inhibited by competing with the active sites or suppressing the formation of posnjakite in the coexistence of CIP. These results provided valuable information for the co-removal of CIP and heavy metal.