Abstract
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Adsorption of tetracycline (TC) and ciprofloxacin (CIP) in single and binary systems by diethylenetriaminepentaacetic acid-functionalized magnetic graphene oxide (DDMGO) was explored. DDMGO were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS) and zeta potential measurements. The adsorption kinetics and equilibrium data of single antibiotic were well fitted by pseudo-second-order and Freundlich isotherm models, respectively. Negative ΔGo values hinted the spontaneous nature of TC and CIP sorption. Moreover, the ΔHo was positive for TC removal and negative for CIP removal, indicating that TC adsorption was endothermic and CIP adsorption was exothermic. Various experimental conditions (pH, ionic strength and foreign ions) presented an important influence on TC and CIP removal. In binary systems, TC sorption onto DDMGO exhibited stronger inhibition effect by the coexisting competitive antibiotics than that for CIP. The reusability experiment revealed that the DDMGO had an excellent regeneration performance in single and binary systems. TC and CIP removal mechanism on DDMGO was mainly dependent on π-π interaction, hydrogen bonds and amidation reaction. Besides, TC and CIP uptake could also be explained by cation-π and electrostatic interaction, respectively. These findings showed that DDMGO was an efficient and reusable adsorbent for antibiotics elimination.