Zinc Based Metal-Organic Frameworks as Ofloxacin Adsorbents in Polluted Waters: ZIF-8 vs. Zn3(BTC)2

Abstract

Two different zinc-based metal-organic frameworks (MOFs) were investigated to remove one of the most used fluoroquinolone antibiotic, Ofloxacin (OFL), from polluted water. The most common zeolitic imidazolate framework-8 (ZIF-8) and the green Zn(II) and benzene-1,3,5-tri-carboxylate (Zn3(BTC)2) were prepared through a facile synthetic route and characterized by means of Fourier-Transform Infrared (FT-IR) Spectroscopy, X-ray Powder Diffraction (XRPD), and Scanning Electron Microscopy (SEM) analyses. The two MOFs were compared in terms of both adsorption and kinetic aspects under real conditions (tap water, natural pH). Results showed that OFL was adsorbed in remarkable amounts, 95 ± 10 and 25.3 ± 0.8 mg g−1 on ZIF-8 and Zn3(BTC)2, respectively, following different mechanisms. Specifically, a Langmuir model well described the ZIF-8 profile, while for Zn3(BTC)2, cooperative adsorption occurred. Moreover the kinetic results were quite different, pseudo-second-order and sigmoidal, respectively. The suitability of ZIF-8 and Zn3(BTC)2 as adsorbent phases for water depollution was tested on tap water samples spiked with OFL 10 µg L−1. The obtained removal efficiencies, of 88% for ZIF-8 and 72% for Zn3(BTC)2, make these materials promising candidates for removing fluoroquinolone antibiotics (FQs) from polluted waters, notwithstanding their limited reusability in tap water, as demonstrated by in-depth characterization of the two MOFs after usage.

Combined Layer-by-Layer/Hydrothermal Synthesis of Fe3O4@MIL-100(Fe) for Ofloxacin Adsorption from Environmental Waters

“…OFL adsorption on the MIL-100(Fe) and Fe 3 O 4 @MIL-100(Fe) was studied using a consolidated batch equilibration method [44]. Briefly, a fixed amount (10 mg) of each MOF was suspended in 20 mL of tap water spiked with OFL in the range 10-293 mg L −1 .…”

“…20 mg of MIL-100(Fe) and Fe 3 O 4 @MIL-100(Fe) were separately suspended in 40 mL of tap water at an initial OFL concentration of 20 mg L −1 . Unlike the previous paper [44], the suspensions were mandatorily stirred with a glass stirring rod throughout the experiment. Aliquots (100 µL) were withdrawn at various time intervals in the range of 0-60 min, diluted to 5-10 mL tap water, and filtered (0.22 µm nylon syringe filter) before the HPLC-FD analysis for the OFL determination at time t (C t ).…”

Efficiency in Ofloxacin Antibiotic Water Remediation by Magnetic Zeolites Formed Combining Pure Sources and Wastes

“…The BET isotherm, adapted to describe liquid-phase adsorption [55] through multilayer adsorption, has the following form (Equation ( 5)):…”

“…To the best of our knowledge, such materials were tested here for the first time for removing ofloxacin (OFL) under relevant environmental conditions (i.e., tap and river water, natural pH, microgram per liter concentration). Due to our previous investigations on the antibiotic fluoroquinolone's (FQ) behavior towards natural and synthetic substrates [52][53][54][55], OFL was chosen as a model molecule in these new experiments. Kinetic and equilibrium studies were performed in tap water to evaluate the adsorption properties of such materials towards OFL, while structural investigations were performed on the materials, before and after antibiotic loading, to elucidate the adsorption mechanism.…”

Feature Paper in Environmental Chemistry and Technology

“…Therefore, in recent years, several studies involving the use of some metal-organics to remove these new forms of pollutants from the environment have been conducted. In a study conducted by Capsoni et al [7], two different zinc-based metal-organic frameworks (MOFs) were investigated to remove one of the most used fluoroquinolone antibiotics, ofloxacin (OFL), from polluted water. The obtained removal efficiencies, of 88% for ZIF-8 and 72% for Zn 3 (BTC) 2 , make these materials promising candidates for removing fluoroquinolone antibiotics (FQs) from polluted waters, notwithstanding their limited reusability in tap water.…”