Adsorption kinetics of amoxicillin, ampicillin, and doripenem on organobentonite

The frequent discharge of antibiotic compounds to the environment has accelerated the emergence and spread of superbugs, causing a global public health crisis. Clay material such as bentonite represents a promising solution for removing antibiotics from wastewater given its high porosity, abundance, and environmental compatibility. Here, the adsorption kinetics of amoxicillin, ampicillin, and doripenem on an organobentonite modified with chitosan are studied across temperature range of 30-50 oC. The kinetic data were correlated by various kinetic models such as pseudo-first-order (PFO), pseudo-second-order (PSO), Elovich, and intra-particle diffusion. PSO was shown to provide the most accurate representation for the adsorption kinetics of all three antibiotics at 30-50 oC, whereas the fitted parameters such as mass ratio of adsorbed adsorbate to adsorbent (mg g-1) and adsorption rate (g mg-1 min-1) were given as 35.538-53.569 mg g-1 and 5.263×10-3-6.056×10-3 g mg-1 min-1 for amoxicillin, respectively; 46.688-55.869 mg g-1 and 5.098×10-3-6.886×10-3 g mg-1 min-1 for ampicillin, respectively; and 54.032-59.606 mg g-1 and 6.262×10-3-6.709×10-3 g mg-1 min-1 for doripenem, respectively. In addition, multiple rate-controlling steps were also indicated in the correlation using intra-particle diffusion model.