Preparation Of A Highly Effective Acetylene Black-ptfe Cathode And Treatment Of Dye Waste Water By Peroxi-coagulation

The conventional wastewater treatment methods cannot degrade nonbidegrdableorganic pollutants. electrochemical oxidation as a friendly environment technology isnoticed increasingly. Since the electrode material is not easy choiced,such as the catalyticactivity of cathode materials is not high, current efficiency is low and electrode life is notlong.So the development of more effective electrode materials, the improvement ofelectrode activity and electrode life will become the hot spot of the future research.In this paper, a novel acetylene black-PTFE cathode for electrogeneration of hydrogenperoxide （H₂O₂） was fabricated using acetylene black powder （ABP） as catalyst, PTFE asbinder. The effect of mass ratio of ABP to PTFE, solution pH （3-11）, applied currentdensity (5^-20 mA·cm^-2) and surface hydrophobic property on the activity and useful life ofcathode was investigated using a two-electrode undivided cell fed with air at 2 L·min^-1inNa₂SO₄solution of 0.05 M, and the characteristics of cathode were examined by FTIRspectra, BET measurement, SEM image and CV study. The experimental results show that:（1） so far the activity of cathode is the highest for the electrogeneration of H2O2with airfeed, at pH 3 and the current density of 20 mA·cm^-2the average H2O2generation ratereaching 58.9 mg·L^-1·h^-1·cm^-2during 150 min of electrolysis and the current efficiencybeing 92.7%; （2） a proper and stable surface hydrophobic property could significantlyincrease the useful life of cathode; （3） the cathode had a remarkable restoration andregeneration performance.The degradation of alizarin red S (100 mg L^-1), congo red (100 mg L^-1) and theirmixture (alizarin red S of 50 mg L^-1+ congo red of 50 mg L^-1) was studied using anperoxi-coagulation system with a new acetylene black-PTFE cathode to generate in situH2O2and a Fe anode to produce in situ Fe2+. The cathode performance for generatingH2O2and the removal efficiency of the dyes was investigated under different pH andcurrent densities. The experimental results show that the cathode had a very high activityand good stability for the generation of H2O2with air feed at pH from 3 to 9, and thatperoxi-coagulation method yields a very effective depollution of the dyes since they are oxidized with hydroxyl radicals produced from Fenton reaction between Fe2+and H2O2generated by the corresponding Fe anode and acetylene black-PTFE cathode and theirproducts can then be removed by mineralization or coagulation with the Fe（OH）3precipitate formed. The system had the obvious virtue of low energy consumption. TheUV-visible analysis indicate that the pH had less effect on oxidation processes of alizarinred S, but influenced the degradation pathways of congo red and the mixture. At initial pH3 and the cathode current density of 12 mA·cm^-2, after 120 min of electrolysis the TOCremoval ratio of alizarin red S, congo red and the mixture was 94.06%, 91.80% and95.52%, respectively, and the corresponding specific energy consumption was only0.8736, 0.8592 and 0.8976 kWh m 3, respectively.