Cu(Ii)-Influenced Adsorption of Ciprofloxacin from Aqueous Solutions by Magnetic Graphene Oxide/Nitrilotriacetic Acid Nanocomposite: Competition and Enhancement Mechanisms

Nitrilotriacetic acid-functionalized magnetic graphene oxide (NDMGO) was developed for the removal of ciprofloxacin (CIP) with and without the presence of Cu(II). The physicochemical properties of NDMGO were characterized using SEM, TEM, XRD, FI-IR, XPS and zeta potential measurements. The CIP adsorption process could be better simulated by the pseudo-second-order kinetics and Freundlich isotherm model. Effects of Cu(II) concentrations on CIP uptake, as well as the influence of pH, ionic strength, background electrolyte and the addition sequences of CIP/Cu(II) were investigated. Adsorption results exhibited that the presence of Cu(II) obviously enhanced the CIP adsorption capability through Cu(II) bridging effect. The adsorption capacity for CIP was stronger in the (CIP-Cu(II))-NDMGO system than in the (NDMGO-Cu(II))-CIP and (NDMGO-CIP)-Cu(II) systems. Meanwhile, this nanomaterial showed high performance for Cu(II) adsorption. In addition to Cu(II) bridge enhancement, the mechanism could also be explained by hydrogen bonds, amidation reaction, electrostatic and π-π interaction. These results provided valuable information for the removal of CIP and improved our understanding on reaction mechanism of antibiotics by NDMGO in the presence of metal ions, demonstrated that NDMGO could be developed as an effective adsorbent to simultaneously removal metal ions and organic substances.