Magnetic copper-based metal organic framework as an effective and recyclable adsorbent for removal of two fluoroquinolone antibiotics from aqueous solutions.

Fe3O4/HKUST-1 magnetic copper based metal-organic frameworks (MOF) were synthesized by a simple and facile method and applied as an effective and recyclable adsorbent for the adsorptive removal of two widely used ciprofloxacin (CIP) and norfloxacin (NOR) fluoroquinolone antibiotics (FQAs) from aqueous solutions. Fe3O4/HKUST-1 was thoroughly characterized, and the major influence factors including solution pH, adsorbent amount and salt concentration were investigated. Compared to the reported adsorbents, Fe3O4/HKUST-1 has a very high adsorption rate, and it is found that CIP and NOR could be removed within 30 min. Moreover, the maximum adsorption capacities of the magnetic composites toward CIP and NOR reached as high as 538 mg g-1 and 513 mg g-1, respectively, much higher than those of most of the reported adsorbents for these two FQAs. The saturation magnetization value of Fe3O4/HKUST-1 was 44 emu g-1, which was sufficient for the separation of the Fe3O4/HKUST-1adsorbent from the aqueous solution by the application of an external magnetic field. Additionally, this magnetic material showed a good reusability with the adsorption capability decreasing only slightly after reuse for ten cycles. These results indicated that the magnetic composites Fe3O4/HKUST-1 may be a promising adsorbent in the decontamination of FQAs from wastewater due to its high adsorption capability, fast kinetics, easy separation from water, and excellent recyclability. The adsorption mechanism was proposed based on the effects of pH on adsorption and on the zeta potential of the adsorbent. For the adsorption of CIP and NOR by Fe3O4/HKUST-1, both electrostatic and π-π interactions may be important.