Degradation of sulfonamide antibiotics using ozone-based advanced oxidation process: Experimental, modeling, transformation mechanism and DFT study

In this research, degradation of three sulfonamide antibiotic compounds (SNAs) such as Sulfasalazine (SSZ), Sulfamethoxazole (SMX) and Sulfamethazine (SMT) as well as Metronidazole (MNZ) were investigated for the first time using experimental, modeling and simulation data under O-3, H2O2, and O-3/H2O2 systems. The kinetic and synergistic study confirmed the pseudo-first-order reaction and highest performance of the O-3/H2O2 process for the SNAs degradation process. Two modeling approach, central composite design (CCD) based on response surface methodology (RSM) and artificial neural network (ANN) were utilized to investigate the optimization and modeling of SSZ degradation as the response of O-3/H2O2 system and results were compared. The individual and interactive effects of main operational parameters were also possessed by the main effect graphs, contour and response surface plots. The experimental results showed maximum degradation efficiency at the optimum condition for SSZ, SMX, SMT and MNZ were 98.10%, 89.34%, 86.29% and 58.70%, respectively in O-3/H2O2 process. For proposed reaction mechanism of SNAs in O-3/H2O2 process the influence of inorganic salts including Na2SO4, NaH2PO4, Na2CO3, NaCl and tert butanol (TBA) as organic OH scavenger was studied. Besides that, LC-MS/MS analysis and DFT calculation were employed to identify the intermediate molecules produced (31 species) during the SSZ degradation (as a SNAs model) and a probable degradation pathway was proposed. The results provided a new strategy by combination of experiment and computer simulation to evaluate the O-3/H2O2 system for optimization of SNAs removal from wastewater.