Study on the biodegradability improvement of 2,4 dinitrophenol in wastewater using advanced oxidation/reduction process with UV/SO 3 /ZnO

2,4-Dinitrophenol (2,4-DNP) is a toxic compound that is widely used in many industrial and agricultural processes. This compound has low biodegradability in the environment due to its aromatic structure, and it is unsuccessfully eliminated by other chemical methods. Therefore, in this study, an integrated oxidation and reduction method was used to remove 2,4-DNP from the aqueous medium, in order to simultaneously use the benefits of oxidizing and reducing radicals in 2,4-DNP degradation. 2,4-DNP degradation was modeled by response surface methodology (RSM) and central composite design (CCD). According to the results obtained from RSM, the optimal values for the studied parameters were obtained at pH = 8.9, time = 25 min, ZnO dose = 0.78 g/L, SO 3 = 1.89 mmolL −1 and 2,4-DNP concentration = 5 mg/L. Also, the removal efficiency with the integrated process was 3 to 4 times higher than the advanced oxidation or advanced reduction processes alone. Analysis of the data showed that at the time of the study, 2,4-DNP had been converted to linear hydrocarbons, and increased periods of time were required for complete mineralization. A decrease in the first-order model rate constant (k obs ) and an increase in 2,4-DNP degradation rate (r obs ) were observed at higher DNP concentrations.