Removing amoxicillin antibiotic from aqueous solutions by Saccharomyces cerevisiae bioadsorbent: kinetic, thermodynamic and isotherm studies

Antibiotics are used throughout the world and enter the water resources in different ways after consumption and have turned into one of the important concerns for humans due to their adverse effects of which amoxicillin (AMX) could be referred to. Thus, present research aims to study the efficiency of bioadsorbent produced from Saccharomyces cerevisiae in removing AMX antibiotic from aqueous solutions. The present experimental study was carried out in a discontinued reaction chamber with an optimal volume of 100 cc. The physical and structural specifications of the produced bioadsorbent were analyzed using FTIR, SEM and BET techniques. This study was carried out by culturing Saccharomyces cerevisiae strain on the culture medium of potato dextrose agar and the yeast was transferred to potato dextrose broth culture, 5-7 d after the primary growth of the yeast in order to produce yeast extensively. The effects of pH (2-8), initial concentration of AMX (5-25 mg L-1), the amount of bioadsorbent (0.1-1.5 g L-1) and contact time (10-240 min) were studied in this process. The isothermal models of Langmuir, Freundlich and Dubinin-Radushkevich were used to determine the balance isotherms, pseudo-first and pseudo-second-order kinetic model adsorption process kinetics. Results revealed that the highest efficiency of AMX removal was obtained by bread yeast bioadsorbent at initial antibiotic concentration of 5 mg L-1, bioadsorbent concentration, 0.75 g L-1 and optimal conditions including pH of 5 and contact time of 120 min (93%). Also, results indicate that the adsorption of AMX with the correlation coefficient of 0.939 follows the Freundlich model. Experimental data showed that AMX follows the pseudo-second-order kinetics with the correlation coefficient of 0.99. It can be concluded that the use of the bread bioadsorbent yeast for reducing the pollution load of hospital and manufacturing industries' sewage before entering into conventional treatment units and also before the final discharge of wastewaters containing antibiotic pollutants.