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

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.