Equilibrium, kinetics, and thermodynamics study on the biosorption of reactive levofloxacin antibiotic on Pithophora macroalgae in aqueous solution

Since untreated wastewater from hospitals and residential areas is being discharged directly into surface waterways, pharmaceutical contaminants have been shown to be higher in many countries. Therefore, the development of novel and effective techniques to extract antibiotic substances from wastewater is of utmost importance. The present work aims at the use of green Pithophora macroalgae to remove levofloxacin antibiotic from an aqueous solution through biosorption. Biosorption is an economical and eco-friendly method for treating wastewater. The macroalgae were dried, grounded, and used as biosorbent to remove the levofloxacin (LVX) antibiotics from the aqueous solution. The influence of operating conditions such as initial antibiotic concentration, biosorbent dosage, agitation speed, pH, and temperature was studied. The biosorbent was characterized by FTIR, SEM, and point zero charge. The experimental data were evaluated using Langmuir and Freundlich isotherms. The experimental data best fit the Freundlich isotherm model (R-2 = 0.969), while the kinetic model for the experiment follows the pseudo-second-order (R-2 = 0.998) with a maximum biosorption capacity of 17.8 mg/g. Maximized removal of LVX occurs at favorable conditions of 298 K temperature, 150 mg/L initial concentration of antibiotic, 0.5 g sorbent dose, and 6.5 pH. The calculated thermodynamic parameters reveal that the biosorption of LVX antibiotics occurs by an endothermic process. This study deduces that Pithophora macroalgae biomass proved to be an effective biosorbent for biosorption of LVX antibiotics and may be a novel alternative method for antibiotics removal from aqueous solutions.