Optimization of Dexamethasone Photochemical Oxidation Process Based on Sulfate Radicals using Response Surface Methodology

Dexamethasone is one of the most widely used glucocorticosteroids in medical centers. Due to the inefficiency of conventional treatment methods in its removal from wastewater, it is necessary to evaluate the use of sulfate radicals to properly remove this contaminant from aqueous solutions. The aim of this study was to investigate the removal of dexamethasone from aqueous solutions by sulfate radical under ultraviolet irradiation (UV/S2O8-2) using the Response Surface Methodology (RSM). Dexamethasone removal efficiency in this method by investigating the effect of pH variables between 3 to 9, persulfate (0.5-5 mM/L), initial concentration of dexamethasone (2-10 mg/L) and reaction time (10 to 60 minutes) Was investigated. Dexamethasone concentrations were measured using a high-performance liquid chromatography (HPLC) at 213 nm. The results showed that the UV/S2O8-2 process is effective in the complete removal of dexamethasone, so that by decreasing the pH and concentration of the initial dexamethasone as well as by increasing the concentration of persulfate and reaction time, the removal efficiency of dexamethasone increases. The results of this study showed that the UV/S2O8-2 process can be optimized in a certain number of experiments using the response surface methodology. Dexamethasone removal under optimal conditions of pH (7.7), persulfate concentration (2.7 mM/L), initial concentration of dexamethasone (5.2 mg/L) and reaction time of 34 minutes is 100 %. Due to the stability and high oxidation ability of sulfate radicals (SO4-.), It is recommended to use UV/S2O8-2 process to remove dexamethasone from aqueous solutions.