| Dinitrotoluenes (DNTs) are environmentally persistent pollutants with toxic, carcinogenic and mutagenic activities. Electrocatalytic oxidation technology has promising application prospects especially in treating wastewaters containing refractory owing to its easy operation, high oxidation efficiency, fast reaction rate and environmental benign in wastewater treatment.The Ti/TiO2-NTs/PbO2 electrode was fabricated by anodic oxidation and electrodeposition. The degradation ability of the prepared electrode was also investigated using DNT as a model organic pollutant. The results showed that the novel Ti/TiO2-NTs/PbO2 electrode exhibited good performance and electrocatalytic degradation of organic and long electrode serviced life, compared with traditional Ti/PbO2 electrode. After 240 min degradation, the removal rate of DNT was only 75.0% by Ti/PbO2 electrode, but reached 94.0% by Ti/TiO2-NTs/PbO2 electrode. The electrode serviced life of Ti/TiO2-NTs/PbO2 electrode is about four times as long as Ti/PbO2 electrode. No significant decrease of removal rate of DNT was observed after 150h of use, which indicated that Ti/TiO2-NTs/PbO2 electrode had a high stability.Effectiveness of important process parameters of current density, pH, supporting electrolyte, reaction temperature, electrode distance and initial DNT concentration were investigated. The reasults showed that the removal efficiency of DNT increased with increasing current density. The removal rate of DNT in acid condition was higher than that in the neutral and alkaline condition. Using NaCl as a supporting electrolyte was more favorable to the removal rate of DNT wastwater, compared with using Na2SO4 as a supporting electrolyte. The electrode distance and reaction temperature had little effect on the removal rate of DNT. The removal rate and efficiency of DNT decreased with increasing initial DNT concentration. The result also showed that after the addition of NaHCO3 as a hydroxyl radical scavenger the removal rate of DNT decreased from 95.9% to 74.8% after 240 min reaction, indicating that hydroxyl radical played an important role in the degradation of DNT. A pseudofirst-order kinetics was observed for the degradation of DNT in this electrocatalytic oxidation.The Ti/TiO2-NTs/PbO2 electrode was applied to the treatment of DNT production wastewater. The optimal process conditions were determined basing on the experiment. The optimum current density, pH and reaction time for treatment DNT production wastewater were 30 mA/cm2,3.0 and 240 min, respectively. The removal of COD, DNT and color were 63.2%,86.9% and 96.3%at the optimum conditions. The BOD5/COD of the DNT production wastewater increased from 0.04 to 0.32, implying that the biodegradability of the wastewater was improved significantly after electrocatalytic pretreatment. |
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