Evaluation of Langmuir and Freundlich Isotherms for Removal of Cephalexin and Tetracycline Antibiotics By Sistan Sand from Water and Wastewater Samples

In this research, Sistan sand was used as a natural and inexpensive sorbent for removal of cephalexin and tetracycline antibiotics from water and wastewater samples. For a concentration ۶۰.۰ mg L-۱ of cephalexin, optimum removal conditions were: pH of the sample ۳.۰, adsorbent amount ۱.۰ g, contact time ۲۰.۰ min, added amount of sodium chloride to adjust the ionic strength of the solution ۷.۰ g L-۱. Langmuir isotherm was the best fitted model for this adsorption process and adsorbent capacity was calculated to be ۰.۲۶ g g-۱. This adsorbent was able to remove up to ۶۸.۱% of cephalexin from wastewater. In case of tetracycline, for a ۹۰.۰ mg L-۱ of the analyte, the optimum adsorption conditions were achieved at pH ۸.۰, ۱.۰ g of sorbent, contact time of ۳۵.۰ min and ionic strength of the solution as sodium chloride of ۷.۰ g L-۱. The isotherm was best in agreement with Freundlich model. Adsorbent capacity was ۰.۷۶ g g-۱ and up to ۷۶.۲% of this antibiotic could be removed from wastewater. 

Keywords:

Cephalexin , Tetracycline , langmuir isotherm , Freundlich model , Wastewater analysis