MODELING AND OPTIMIZATION OF REMOVAL OF CEFALEXIN FROM AQUATIC SOLUTIONS BY ENZYMATIC OXIDATION USING EXPERIMENTAL DESIGN

Antibiotics are used globally and, after use, they enter water sources in different ways. The presence of these compounds in the environment has created concerns about the toxicity of aquatic organisms and the emergence of antibiotic-resistant bacteria. The purpose of this study was to remove cefalexin from aqueous solutions by enzymatic oxidation using response surface methodology (RSM). For this purpose, batch experiments were performed to evaluate the effect of independent variables, including temperature, pH, contact time, enzyme activity, HBT mediator concentration, and antibiotic concentration. The residual cefalexin concentration was determined by HPLC. The Box-Behnken design of experiments and RSM were used to evaluate the overlap between variables. The results showed that the oxidation efficiency increased with increasing contact time and enzyme activity and decreasing antibiotic concentration. The highest and lowest removal percentages were 90.5% and 5.54%, respectively. Considering the value of R-2 (0.946) and adjusted R-2 (0.95) in the RSM model, one can state that the selected model is suitable for data analysis. Finally, the second-order polynomial analysis and the quadratic model were used as the best model for finding the relationship between the main variables and cefalexin removal efficiency. The Box-Behnken Design model can be effective for optimizing enzymatic oxidation of cefalexin, and laccase can be used to remove cefalexin.