Treatment Of Wastewater Containing Nitrobenzene And Phenol By Combination Of Heterogeneous Catalysis With Electrochemical Process

In recent years, electrochemical technology has many advantages in removing pollutants from wastewater. Heterogeneous catalytic technology has been used in the treatment of environmental wastewater. In this study, with the combination of electrochemistry and heterogeneous catalysis in the bipolar packed bed cell, the electric nonconducting particle was replaced by catalyst and heterogeneous catalytic reactions occurred in an electrochemical reactor. And a novel electrochemical heterogeneous catalytic reactor was constituted by combination of electrochemistry and heterogeneous catalytic process. Nitrobenzene and phenol were selected as treatment objects by the new process. The degradation of the organic was investigated and primary conclusion was as followed.The traditional bipolar packed bed cell was used to treat nitrobenzene and phenol from wastewater. The optimal conditions of nitrobenzene electrolysis were determined as: applied potential of 40 V, Na₂SO₄ concentration of 1000 mg L^-1 and pH 10. Under optimal conditions nitrobenzene removal was 61.4%. And the optimal conditions of phenol electrolysis were determined as: applied potential of 25 V, Na₂SO₄ concentration of 1000 mg L^-1 and pH 2.5. Under optimal conditions phenol removal was 42.6%. Both the apparent kinetics on nitrobenzene and phenol removal can be expressed as the pseudo-first order reaction.Treatment of nitrobenzene wastewater by electrochemical heterogeneous catalytic process, the optimal conditions of nitrobenzene removal were as: applied potential of 40 V, Na₂SO₄ concentration of 500 mg L^-1, pH 10 and 45 min of HRT. By evaluation of nitrobenzene degradation, the best catalyst was selected as Fe₂O₃/γ-Al₂O₃. With the filling of Fe₂O₃/γ-Al₂O₃, the apparent kinetics on nitrobenzene removal can be expressed as the pseudo-first order reaction and nitrobenzene and TOC removals were 75.1% and 39.8%, respectively. With the introduction of catalyst, the nitrobenzene and TOC removals were significant increased by 13.7% and 12.6%, respectivly. After electrolysis, the biodegradablity of the effluent was greatly increased and BOD₅/COD_Cr increased from 0.06 to 0.307. In addition, intermediate and ultimate products were analyzed with HPLC and GC-MS, which included aniline, phenol and p-aminophenol, etc. The possible mechanism of nitrobenzene degradation includes the reduction of nitrobenzene at cathode, direct anodic oxidation and indirect oxidation by cathodic byproducts, and partial mineralization of nitrobenzene.Treatment of phenol wastewater by electrochemical heterogeneous catalytic process, the optimal conditions of phenol removal were determined as: applied potential of 25 V, Na₂SO₄ concentration of 1000 mg L^-1, pH 2.5 and 45 min of HRT. By evaluation of phenol degradation,...