Iranian Journal of

Background and Objective:  Nitrophenols are among the most common and toxic compounds in industrial effluents that 2, 4 dinitrophenol (2, 4-DNP) is the most toxic compound in this group. The object of this study was to optimize the removal of 2, 4-DNP by thermally activated persulfate using a central composite design.
Materials and Methods: This study was performed on a batch thermal reactor with a volume of 4 L. In this study, a central composite design (CCD) with RSM method was used for designing and optimizing the operation parameters such as initial pH of solution, potassium persulfate concentration and temperature. The effect of 2, 4-DNP concentration and reaction time at optimum conditions were also investigated.
Results: The results indicated that the degradation rate of 2, 4-DNP was enhanced by increasing the concentration of persulfate and reducing temperature and pH. The optimum conditions for the highest degradation efficiency (99%) were  as initial concentration 10 mg/L, reaction time 30 min, temperature 60 °C, Potassium persulfate concentration 10 mmol/L, and pH 5. At the optimum conditions, when 2, 4-DNP concentration was increased to 50 mg /L, the 2, 4-DNP degradation rate decreased to 73%.
Conclusion: This study indicated that the heat-activated PS oxidation could be an efficient approach for decomposition of 2, 4-DNP. Temperature was the most influential variable in this regard (p<0.0001).
 

Background and Objective: Phenol compounds are commonly applied as raw materials in the production of pesticides, herbicides, and dyes. These compounds are toxic to animals, plants, and microorganisms. In this study, the sonophotocatalytic degradation of 2,4-dinitrophenol in aqueous solutions was investigated using organic-mineral polymer catalysts containing Zink and Cobalt oxides under visible light and ultrasonic (US) irradiation.
Materials and Methods: The characteristics of the synthesized catalyst were determined using XRD, FTIR, and SEM techniques. The effect of several key parameters, including pH (3-9), catalyst dosage (0.3-1 g/L), time (0-90 min), US power (100-200 W/m²), and initial concentration of 2,4-dinitrophenol (20-100 mg/L), on the degradation efficiency was also investigated.
Results: After 75 minutes of sonophotocatalytic processing, complete degradation of 2,4-dinitrophenol (20mg/L) was achieved with catalyst dosage of 0.5 g/L, pH of 9.0, and US intensity of 200 W/m². Kinetic studies indicated that the sonophotocatalytic degradation process followed a first-order kinetic model. The results of radical scavenging experiments confirmed that HO° and O₂˚^- radicals are the main oxidative species involved in the degradation of 2,4-dinitrophenol. Furthermore, the reuse of the catalyst for five consecutive tests showed a slight decrease in removal efficiency.
Conclusion: The results demonstrate that the sonophotocatalytic process, using the modified organic-mineral polymers with mixed Zink and Cobalt oxides catalyst, can be an effective method for removing 2,4-dinitrophenol from aqueous media.