Adsorption Characteristics of Amoxicillin on Activated Carbon from Eucalyptus Leave and Wheat Straw

In this study, amoxicillin from aqueous solutions was adsorbed by activated carbons from eucalyptus leave and wheat straw through adsorption process. The effects of varying parameters such as initial pH of amoxicillin solution, initial concentration of amoxicillin solution, adsorbent dosage, contact time and temperature on the adsorption process were examined. Under optimum conditions containing pH 11, amoxicillin initial concentration 10 mgL-1, adsorbent dosage 0.07 g, contact time 30 and 60 min for eucalyptus leave and wheat straw, respectively, and temperature 25±1oC, maximum adsorption percentages for amoxicillin on eucalyptus leave and wheat straw were obtained 72.4% and 79.2% respectively. In addition, comparison of the experimental results with Langmuir, Freundlich and Temkin adsorption isotherms, showed that the Langmuir isotherm have better fitting with the equilibrium data than the Freundlich isotherm but the fitting with Temkin isotherm is weaker for both adsorbents. Also, thermodynamic parameters of the adsorption such as 〖∆H〗^0 and 〖∆S〗^0 were calculated that theirs negative values showed that the amoxicillin adsorption on eucalyptus leave and wheat straw is an exothermic process and along with decrease of randomness, respectively. Meanwhile, the more negative value of 〖∆G〗^0 at 25oC compared to higher temperatures is a sign of more spontaneous adsorption process at this temperature. In addition, the study of adsorption kinetics showed that the amoxicillin adsorption on both adsorbents is pseudo-second order.