Sustainable waste management and recycling of Zn–Al layered double hydroxide after adsorption of levofloxacin as a safe anti-inflammatory nanomaterial

Abstract

Inorganic nano-layered double hydroxide (LDH) materials are used in the catalytic field, and have demonstrated great applicability in the pharmacological fields. In the current study, we report Zn-Al LDH as an adsorbent for levofloxacin (levo). The physical and chemical properties of the prepared material before and after adsorption were monitored using X-ray diffraction, Fourier-transform infrared (FT-IR) spectroscopic analysis, energy dispersive X-ray spectroscopy (EDX), Brunauer-Emmett-Teller (BET) surface area measurements, high-resolution transmission electron microscopy (HRTEM), and field emission scanning electron microscopy (FESEM). Density functional theory (DFT) calculations for levo and its protonated species were studied at the B3LYP/6-311G (d,p) level of theory. The removal percentage of levo was 73.5%. The adsorption isotherm was investigated using nine different models at pH 9, where the obtained correlation coefficients (<i>R</i> ²) using the Redlich-Peterson and Toth models were 0.977. The thermodynamic parameters Δ<i>S</i>°, Δ<i>G</i>° and Δ<i>H</i>° were estimated and discussed in detail. Also, to support the adsorption research field, the applicability of the formed waste after the adsorption of levo onto Zn-Al LDH was investigated for medical purposes. The toxicity of levo in both normal and nanocomposite form was studied. Neither toxicological symptoms nor harmless effects were exhibited throughout the <i>in vivo</i> study. The oral anti-inflammatory activity, tested using 6% formalin to produce edema in the footpad, was manifested as a significant increase of 37% in the anti-inflammatory effect of the Zn-Al LDH/levo nanocomposite compared to levo in its normal form.