Chitosan beads coated with almond and walnut shells for the adsorption of gatifloxacin antibiotic compound from aqueous solutions

In the present study, chitosan (C), walnut (W), and almond shell (A) powder adsorbent (in different combinations as almond shells:walnut:chitosan 2:1:1 (AWC), chitosan:almond shell:walnut 2:1:1 (CAW), and walnut:almond shells:chitosan 2:1:1 (WAC)) powder were combined in different ratios to produce low-cost composite adsorbent beads for the removal of antibiotics gatifloxacin (GAT) from synthetic wastewater. The beads were characterized by a scanning electron microscope, Fourier transform infrared spectrum spectrophotometer, and energy-dispersive X-ray spectroscopy. The batch adsorption approach was employed to remove the antibiotic from the water. Moreover, isotherm and kinetics were conducted to illustrate the adsorption mechanism. Parameters like the effect of the adsorbent's dosage, pH, initial concentration, and contact time on antibiotic adsorption were evaluated. Adsorption percentage increased slightly with the increase in adsorbent dosage. The optimum pH for GAT adsorption on beads was 5-7. In addition, adsorption increased with initial antibiotic concentration and time rise. The adsorption isotherm data were successfully fitted to Langmuir isotherm for AWC and CAW beads, while WAC beads followed the Freundlich isotherm. The highest adsorption was attained at pH 5 on CAW beads and pH 7 on AWC and WAC beads. The optimal contact time for equilibrium studies was 120 min for all types of beads. The adsorption isotherm data in AWC beads fit well with the Langmuir model and Freundlich adsorption for CAW and WAC beads. The rate of adsorption on beads follows Lagergren pseudo-second-order kinetics. The results indicate that prepared combination beads can be used to remove antibiotics from wastewater.