Highly efficient adsorption of fluoroquinolone antibiotics using chitosan derived granular hydrogel with 3D structure

Here, a granular hydrogel prepared from chitosan as the grafted backbone and acrylic acid as the polymerizable monomer was used as the adsorbent to remove two typical fluoroquinolone antibiotics, i.e. ciprofloxacin and enrofloxacin. The parameters affecting the adsorption capacity were investigated via a series of adsorption experiments, including pH (2.0-9.0), contact time (1-180 min), initial concentration (10-600 mg/L), and ion strength (1 mM and 10 mM NaCl/CaCl2). The results showed that the granular hydrogel possessed porous 3D structure and, the ionizable characterization of -COO- groups made the adsorbent be pH-sensitive and the maximum adsorption occurred at pH = 3.0. Moreover, the presence of abundant -COO- groups within 3D structured network provided the adsorbent with higher adsorption capacity of 267.7 mg/g for ciprofloxacin and 387.7 mg/g for enrofloxacin. When the initial concentrations were 10, 50 and 250 mg/L, the equilibrium time was determined to be 30, 60 and 120 min, respectively. After five consecutive adsorption-desorption cycles, a higher adsorption percentage (>85%) was still obtained, demonstrating that the developed adsorbent could be easily regenerated and reused for several times. (C) 2019 Elsevier B.V. All rights reserved.