removal of metronidazole antibiotic pharmaceutical from aqueous solution using tio2/fe2o3/go photocatalyst: experimental study on the effects of mineral salts

A tio2/fe2o3/go photocatalyst is synthesized via the sol-gel method and characterized by x-ray diffraction (xrd), x-ray fluorescence (xrf), ft-ir, brunauer-emmett-teller (bet), and ultraviolet-visible diffuse reflection spectroscopy (uv-vis drs) analyses. metronidazole (met) concentration (10-20 mg/l), photocatalyst concentration (0.5-1.5 g/l), irradiation time (60-120 min), and initial ph (4-6) are investigated through response surface methodology (rsm), and the optimal process conditions are determined. the removal efficiency of met with the tio2/fe2o3/go photocatalyst is 97% under optimal conditions: a pollutant concentration of 10 mg/l, the irradiation time of 120 min, photocatalyst concentration of 1 g/l, and ph of 5. the influence of mineral salts concentrations (50-800 mg/l), including nacl, na2so4, nahco3, kcl, mgso4, and cacl2, are examined at the initial ph of 5, photocatalyst concentration of 1 g/l, and pollutant concentration of 20 mg/l. according to the results, the reaction rate constant decreases with an increase in mineral salts concentrations up to 800 mg/l, especially with na2so4 (42.43% deactivation) and also with mgso4 (38.08%) and nahco3 (37.73%), under the same operational conditions. the effects of mineral salts such as nacl and kcl on the reaction rate constant for the contaminant removal efficiency have a downward trend until these salts reach a 200 mg/l concentration, and then they experience an upward trend.