Efficient removal of fluoroquinolones antibiotics by using kaolin-tannic acid-Fe(III) composite adsorbents from water

In this work, a series of novel composite adsorbents (k-TAFe) was designed and fabricated through a one-step method, that is, the chelation crosslinking of tannic acid, kaolin particles and different contents of Fe(III). k-TAFe had a high efficiency in adsorption of various fluoroquinolones antibiotics (FQs) from water. The detailed performance of k-TAFe in FQs adsorption, including the influences of Fe(III) content, solution pH, inorganic and organic additives, adsorption time and FQs' concentration, has been investigated systematically using ofloxacin (OFL), one of popular FQs, as an example. The maximal OFL uptake of k-TAFe was 0.405mmol/g at an initial pH of 6.0. On the basis of the analysis of the x-ray photoelectron and fourier transform-infrared spectra before and after adsorption, the comparison in the apparent performance of k-TAFe in adsorption of seven FQs with similar structures and their two sub-structural analogs, and theoretical calculation, multiple adsorption mechanisms, including chelating effect, hydrogen bonding, electrostatic attraction, and π-π electron–donor–acceptor interactions, were involved and discussed in detail. Among them, chelating effect due to Fe(III) played a key role in OFL adsorption, and the addition of kaolin particles synergistically enhanced Fe(III) fixed on the composite adsorbents, increased the Fe(III) contents, and caused an improved OFL uptake of k-TAFe. Because of the evident advantages of environmental-friendliness, high adsorption performance and low cost, k-TAFe as an efficient adsorbent has notable application potentials in removal of FQs from water. [Display omitted] •Kaolin-tannic acid-Fe(III) composite (k-TAFe) is obtained by simple one-step method.•k-TAFe shows superior performance in adsorption of various fluoroquinolones (FQs).•7 FQs with similar structure and 2 sub structural analogs are compared.•Particular adsorption mechanisms of k-TAFe are dominant at different pH levels.•Kaolin enhances Fe(III) adsorbed on composite and improves the FQs uptakes of k-TAFe.