Evaluating the performance of L-methionine modified montmorillonite K10 and 3-aminopropyltriethoxysilane functionalized magnesium phyllosilicate organoclays for adsorptive removal of azithromycin from water

This study examined the adsorptive removal of azithromycin onto organoclays under batch conditions. Organoclay adsorbents (L-methionine modified montmorillonite K10; denoted as LMP clay and 3-aminopropyltriethoxysilane functionalized magnesium phyllosilicate; denoted as AMP clay) were synthesized by facile methods and characterized by Fourier Transform Infrared Spectroscopy (FT-IR), N-2 adsorption-desorption isotherms (BET method), Powder X-ray diffraction (PXRD), Field Emission Scanning Electron Microscopy (FE-SEM), Transmission Electron Microscopy (TEM), Energy-dispersive X-ray Spectroscopy (EDS), Thermogravimetric (TG), and Dynamic light scattering analysis (DLS) to examine the adsorption mechanism. Parameters affecting the adsorption process, such as pH, ionic strength, contact time, adsorbent dosage, initial AZM concentration, and temperature were investigated. The results of isotherm modeling revealed that the experimental data were more consistent with the Freundlich isotherm model (R-2 > 0.96). The kinetic data were more compatible with the pseudo-second-order kinetic model (R-2 > 0.97). The thermodynamic parameters indicated that the AZM adsorption was spontaneous and exothermic. The AZM removal efficiency was attained as 98 +/- 1% and 93 +/- 1% with LMP clay and AMP clay, respectively (adsorbent dosage = 0.5 g L-1, initial AZM concentration = 50 mg L-1, pH = 8.0 +/- 0.1, and temperature = 298 K). The monolayer adsorption capacity of LMP clay and AMP clay at 298 K was obtained 298.78 and 286.10 mg g(-1), respectively. The electrostatic attraction, hydrophobic effects, hydrogen bonding, and high surface area played dominant roles in the AZM adsorption. Further, the organoclay adsorbents could be consecutively cycled and regenerated for at least four adsorption-desorption cycles.

Automated summary

This study investigated the adsorptive removal of azithromycin onto organoclays under batch conditions. Various characterization methods were used to examine the adsorption mechanism. The results showed that the Freundlich isotherm model and pseudo-second-order kinetic model were suitable for describing the adsorption process. The thermodynamic parameters indicated that the adsorption was spontaneous and exothermic. The organoclay adsorbents showed high removal efficiency for azithromycin and could be consecutively cycled and regenerated for multiple adsorption-desorption cycles.