[Degradation of aniline by a dual-electrode electrochemical oxidation process].

The efficiency and the mechanism of aniline degradation by an electrochemical oxidation process using a Ti/SnO2-Sb2O5 electrode as the anode and a graphite electrode as the cathode, were studied in two aqueous electrolytes with/without Fe2+. The results showed that the reasonable anodic potential was about 2.0 V +/- 0.1 V for Ti/SnO2-Sb2O5 electrode to oxidize organic compounds, while the optimum cathodic potential was -0.65 V for graphite electrode to reduce O2 generating H2O2. The oxidation degradation of aniline could not take place only by the single action of H2O2. Anodic oxidation was accounted for the degradation of aniline in the absence of Fe2+, while in the presence of Fe2+ both electro-Fenton oxidation and anodic oxidation (dual-electrode electrochemical oxidation) could degradate aniline effectively, and in this case the former was the main mechanism. Under the conditions of -0.65 V cathodic potential, pH 3.0 and 0.5 mmol x L(-1) Fe2+, the removal rate of COD was 77.5% after 10 h treatment and a current efficiency of 97.8% for COD removal could be obtained. This work indicates that the dual-electrode electrochemical oxidation is feasible for the degradation of organic compounds with a high current efficiency by using Ti/SnO2-Sb2O5 as anode as well as the reasonable anodic and cathodic potentials.

Anodic oxidation process for the degradation of 2, 4-dichlorophenol in aqueous solution and the enhancement of biodegradability.

Degradation of 2, 4-dichlorophenol (2, 4-DCP) in aqueous media by anodic oxidation using Ti-based oxide electrode has been studied. Additionally, the influence of anodic oxidation on the biodegradability of 2, 4-DCP solution was investigated. It was found that alkaline media was suitable for the anodic oxidation of 2, 4-DCP, while acidic media tended to cause more 2, 4-DCP volatizing. The poor degradation of 2, 4-DCP was ascribed to the direct anodic oxidation at lower anodic potential, while the indirect anodic oxidation was responsible for the better degradation at higher anodic potential with a high power consumption. The variation of COD and the characteristic of UV-vis spectra indicated that some organic intermediates were produced during the course of the degradation of 2, 4-DCP. The obvious inhibition of microbial activity was observed when 2, 4-DCP concentration was about 100 mg/L. The anodic oxidation process was able to enhance the biodegradability of 2, 4-DCP solution and this enhancement became greater with the extension of anodic oxidation treatment. This work suggests that the anodic oxidation with the Ti/IrO(2)/RuO(2)/TiO(2) electrode generally applied in chemical industry is a promising alternative for the pretreatment of the wastewaters containing chlorophenols.

[Electrochemical oxidation of dual electrodes with iron promoting used for the treatment of wastewater from acrylonitrile production].

Effects and laws of electrochemical oxidation of dual electrodes with iron promoting for the treatment of wastewater from acrylonitrile production were investigated using Ti/SnO2 + Fe as combined anodes and graphite as cathode. Compared with traditional electrochemical oxidation, the higher removal of organic pollutants and current efficiency were obtained via oxidation of dual electrodes. Through the process COD removal efficiency and current efficiency were enhanced by 11.0%-13.8% and 8.0%-15.0% respectively, referred to the results from traditional electrochemical oxidation under conditions of the same voltage and no hydrogen peroxide added. With 2 200 mg x L(-1) hydrogen peroxide and voltage of 4.0 V, COD and TOC removal efficiencies increased to 74.6% and 67.9% respectively, and with the increase of hydrogen peroxide, both were enhanced obviously. During the initial reaction period, the higher hydrogen peroxide concentration and the lower Fe2+ concentration were detected, and with reaction time increased, hydrogen peroxide concentration decreased rapidly and Fe2+ concentration increased gradually. The voltage value had great effect on the concentrations of hydrogen peroxide and Fe2+, and the current efficiency was affected obviously by the time of current passed through iron anode under certain initial dosage of hydrogen peroxide. The better color removal was also obtained from electrochemical oxidation of dual electrodes. The electrochemical oxidation of dual electrodes with iron promoting presents a new alternative for the treatment of organic wastewater.

[Electrolysis of iron promoting for the advanced treatment of landfill leachate].

The advanced treatment of landfill leachate by electrochemical oxidation was carried out in a box-style electrochemical reactor, using oxide-coated titanium anode. The effects of the concentration of FeSO4, reaction time, the initial pH value, and voltage (current) on the removal of contaminants were investigated. The removal efficiency of contaminant was compared when Fe2+ and Fe3+ used. The results show, compared with the traditional oxidation of electrolysis, the electrolysis of iron promoting can enhance the organism removal efficiency prominently. The increase of the concentration of FeSO4 can result in the increasing organism removal, but when it exceeds 1 250 mg x L(-1), the increasing range decreases. The removal progress of contaminants is very fast in the first 30 minutes, and then slows down. The reasonable initial pH value is 3 - 4. To eliminate COD and NH4(+) -N from leachate effectively, voltage and current must be larger than 3.3 V and 4.8 A respectively. Compared with Fe2+, the organism removal efficiency is slightly lower when Fe3+ used. Two tentative ideas, making recycle use of iron and the application of acid waste water in the process, were proposed.