Study On The Degradation Of P-Nitrophenol And Microcystin-LR Wastewater By BDD Electrode

Electrochemical oxidation method, as an environment-friendly technology for itsunique superiority in treatment of organic wastewater has been pay great attention byresearchers at home and abroad. The electrodes, especially for the anode which are theheart in electrochemical reaction system are the important effect on effectivelydegradation of organic wastes, increasing the removal rate of pollutions and reducingenergy consumption. So the work of finding electrodes with high electrocatalic ability hasgreat significance.Boron-doped diamond thin film electrode （BDD） is a perspective material to be usedin electrochemical degradation of organic wastewater due to its excellent electrochemicalperformance. The electrochemical characters of the boron-doped diamond film electrodewere studied in this dissertation, results demonstrated that BDD electrode have charactersof wide potential window, low background current and corrosion stability. Andinvestigation of the oxidation of p-nitrophenol and MC-LR on diamond electrode was alsocarried out with the goa l of developing application in the electrochemical oxidation ofpoisonous and refractory organics for wastewater treatment.In the study of PNP degradation by BDD anode, the effect factors such as pH value,current density, Cl-concentration were investigated in the process of PNP and CODdegradation, the degradation performances on Pt electrode were compared, the possiblepathway of degradation mechanistic on BDD and Pt electrode were also investigated.Results demonstrated that the best conditions for PNP and COD remove was pH value for12, electrolytic concentration was20mA·cm-2and Cl-concentration was0.1mol/L. BDDelectrode is super to Pt electrode in the treatment of PNP wastewater. The results of PNPdegradation in high chlorine contain support electrolyte demonstrate: some chlorineorganic compounds were generate during the degradation of PNP, and the compound weredifficult to degradation, thus inhibit the COD removal.Most of the degradationintermediates of PNP are the same on BDD and Pt electrodes. On BDD electrode, PNPcould be quickly convert to organic acids, while the accumulation of degradationintermediates was happened on Pt electrode. In the study of MC-LR degradation, such parameters as reaction time, applied currentde nsity, supporting electrolyte conc entration, different cations and anions wereinvestigated to determine their effects on this oxidation process. Results demonstrated thatthe removal rate of MC-LR was increase along with the electrolytic time,current density,electrolyte concentration increases; the influence of cations on the de grada tion ratesincreased in the sequence of Li+＞K+＞Na+for the three chosen anion electrolytes,whereas it is Cl－> SO₄^2－>CO₃^2-> NO₃for cation electrolytes. We also elucidate thepossible intermediates and mechanisms of degradation. The de gradation of MC-LR overBDD involved in the series steps such as the oxidation of the double bonds of Adda, thedouble bond of Mdha and Amino of Guanidino group, the radical attach at carboxylategroup o n D-Glu, a nd the hydrolysis of peptide chains.