Study On Electrochemical Treatment Of Methylene Blue

At present,the dye wastewater is one of the refractory industrial wastewater due to its high chromaticity,large toxicity and hard degradability.The electrochemical method is popular because of high removal rate,low secondary pollution and simple equipment.Therefore,Using electrochemical method treatment of dye wastewater what explores the effect of different anode material in dye wastewater treatment and the degradation of dye molecules course has important theoretical significance and practical value.In this paper,the active cationic dye methylene blue?MB?,which has a strong electrochemical activity and positive charge,was treated by electrochemical method.The parameters such as applied voltage,plate spacing,electrolyte concentration and MB initial concentration were optimized using steel plate,titanium ruthenium and graphite as anode separately through single factor condition experiment.The experimental results showed that,under the optimum technological conditions,when steel electrode treated with MB simulated wastewater could reach 94.65%,and the removal rate of TOC could reach 73.28%.When titanium ruthenium steel electrode treated with MB simulated wastewater,the removal rate of MB was 91.42%,and the removal rate of TOC was48.74%.The removal rate of MB simulated wastewater with graphite steel electrode was94.80%,and the removal rate of TOC was 43.59%.Compared with the treatment of three kinds of anode materials,it was said that the mineralization rate was the highest when electrochemical treatment of the steel electrode was used to simulate wastewater.The electrochemical degradation of methylene blue simulated wastewater by the three anode materials all fit well to the kinetic first-order reaction model.The linear correlation coefficients were 0.9751,0.9822 and 0.9944.Through the scanning of three working electrode cyclic voltammetry curves,methylene blue had an obvious oxidation peak near 1.2V on the surface of the steel electrode,and there was an oxidation peak near 0.6v on the surface of the graphite electrode.While there was no obvious redox peak on the surface of the titanium ruthenium electrode,it indicated that the methylene blue was an indirect electrocatalytic oxidation process in the titanium ruthenium electrode system,which was a direct electrochemical oxidation process in the plate electrode and graphite electrode system.Combining with GC-MS,TOC and IC analysis,the degradation products of methylene blue simulated wastewater treated by three kinds of electrodes under the optimal conditions were respectively detected.The degradation mechanism of methylene blue was analyzed and the possible degradation path of methylene blue was deduced.Possible degradation pathways for the electrochemical treatment of MB at the steel plate electrodes:?1?MB methyl first off,oxidation of formaldehyde or formic acid and other small molecules of acid;?2?The carbon nitrogen bond and carbon sulfur bond of MB were destroyed to produce 2-methyl-5,5-diphenyl-4-methylimidazole,which then oxidized to produce thiazole and phenolic compounds,and eventually mineralized into small molecular compounds such as acetic acid,NO₂^-,NO₃^-,CI^-,SO₄^2-,CO₂ and H₂O.Possible degradation pathways for the electrochemical treatment of MB at the titanium ruthenium electrode:?1?MB methyl first off,oxidation of formaldehyde or formic acid and other small molecules of acid;?2?The carbon sulfur bond of MB and carbon nitrogen bond were broken to produce indole compound,which was continuously oxidized to produce the carbonyl group containing compound and phenolic compound as well as the diacid,which was finally converted into small molecular compounds such as acetic acid,NO₂^-,CI^-,SO₄^2-,CO₂,H₂O etc.Possible degradation pathways for the electrochemical treatment of MB at the graphite electrode:?1?methyl first MB off,oxidation of formaldehyde or formic acid and other small molecules of acid;?2?The carbon and sulfur bonds of MB were destroyed to produce carbonyl compounds,and the carbonyl compounds continued to be activated by the active group to produce carboxyl compounds,which were then generated by hydroxyl radical action to produce 2,4-bis?1,1-dimethylethyl?phenol and its isomer 2,5-bis?1,1-dimethylethyl?phenol,which continued to be oxidized to 2,5-bis?1,1-dimethylethyl?to benzoquinone,and eventually mineralization into small molecular compounds such as acetic acid,CI^-,NO₂^-,SO₄^2-,CO₂,H₂O etc.