Degradation of 4-Nitrophenol from industrial wastewater by nano catalytic Ozonation

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ABSTRACT: In this project, a nano catalyst (TiO2) and ozone combined with each other and they were used for the removal of 4-nitrophenol (4NP) in industerial wastewater. The effect of some operational parameters such as initial pH (3-9), the concentration of pollutant (20-80 mg/L), and amount of TiO2 were investigated. In O3/TiO2 process, the anion radical  formed before the production of hydroxyl radical. These results were different from the Ozonation process alone, in which high pH had a positive effect on the degradation of 4NP, because hydroxyl radicals was formed. In ozonation and O3/TiO2 processes, about 89 and 97% of  4NP were degraded respectively,  at optimum pH and 60 min of reaction. In catalytic ozonation the degradation rate of 4NP was higher at weak acidic pH conditions (pH=5). The removal of chemical oxygen demand (COD) was increased from 49% (only ozonation) to 74% (O3/TiO2) at 90 min of reaction. The kinetic of degradation was pseudo-first-order and degradation and mineralization of 4NP were estimated by HPLC and COD tests, respectively.