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Fabrication Of Ti/SnO2-Sb2O5/PbO2-PVDF And Its Application On The Electrochemical Oxidation Of Perfluorooctanoic Acid

Posted on:2014-11-16Degree:MasterType:Thesis
Country:ChinaCandidate:Q XiangFull Text:PDF
GTID:2251330425491315Subject:Environmental Engineering
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Currently, the contamination caused by perfluorinated compounds (PFCs) has been gradually developing into a global environmental problem. In consideration of their stable physical and chemical properties and the fact that they are difficult to be conventional bio-degradation or advanced oxidation processes, it is the development of an effective degradation to PFCs that has been the topic in great demand to researchers. The anode material defined as lead dioxide is becoming immensely promising out of its excellent corrosion resistance, electrical conductivity, chemical stability and so on.In this thesis, a hydrophobic material, polyvinylidene fluoride (PVDF), was doped in the lead dioxide modified Ti-substrate anode with the method of electrodeposition. The modified anode features hard to peel off, high oxygen evolution potential and efficient electrochemical oxidation.In the meanwhile, regarding perfluorooctanoic acid as the representative of PFCs, the effects of different initial conditions on electrochemical degradation of PFOA were explored.1. Two different ways of electrodeposition were carried out to fabricate different PbO2modified anode. With the characterization methods such as SEM, EDS and XRD, the anodes’ surface morphology was compared at the micro-scale. As a result, finer particle size and more compact particle arrangement was observed on the surface of the PVDF doped lead dioxide modified anode fabricated under high and low current density, which strengthened the combination between sedimentary layer and substrate.2. The linear sweep voltammetry curve of different anodes showed that the oxygen evolution potential of Ti/SnO2-Sb2O5/PbO2-PVDF (1wt%) is1.78V(vs SCE), higher than1.42V(vs SCE) for Ti/PbO2under the same conditions, in the solution containing0.5mol/L H2SO4at32℃. The results of the accelerated life test of different anodes illustrated that45.75h for Ti/SnO2-Sb2O5/PbO2-PVDF (lwt%) was much longer than8.37h for Ti/SnO2-Sb2O5/PbO2and2.45h for Ti/PbO2, which was measured under the condition of a constant current density of1A/cm2and in the same electrolyte as linear sweep voltammetry. 3. Under the same conditions, the comparison electrodes for electrochemical degradation of PFOA displayed that the electrochemical oxidation degradation of PFOA meets the pseudo-first-order kinetics. Under the condition of room temperature, current density of40mA/cm2, magnetic stirring rate of1300r/min, PFOA3-hours degradation efficiency in the solution with the PFOA initial concentration of100mg/L for3kinds of anodes:Ti/PbO2, Ti/SnO2-Sb2O5/PbO2, Ti/SnO2-Sb2O5/PbO2-PVDF(1.0wt%) were53.0%,84.4%,91.8%, respectively. TOC removal rate were41.5%,44.9%,43.9%, respectively. Defluorination rate were17.4%27.8%,31%, respectively. As a result, Ti/SnO2-Sb2O5/PbO2-PVDF(1.0wt%) performs better than the other. Eventually, the electrodeposition method for the modified anode is determined as follows: electrolyte solution is the mixture of100mL inorganic phase containing200g/L Pb (NO3)2,0.1mol/L HNO3,0.5g/L NaF and ultrapure water and100mL organic phase containing0.02g/mL PVDF in N-methylpyrrolidone solution,85℃water bath, a magnetic stirring rate of1300r/min, a high current density(175mA/cm2) exerted in the first20min, and then a low current density(87.5mA/cm2) in the next40min;4. Three aspects of operating parameters which may impact the PFOA electrodegradation were explored:initial pH, the current density and the voltage between the electrodes. It was found that, at room temperature, the PFOA degradation efficiency in the initial solution of acidic (pH=3) of Ti/SnO2-Sb2O5/PbO2-PVDF(1.0wt%) anode is higher than that in neutral and alkaline solution. With the increase of the current density and the voltage between the electrodes, the PFOA removal efficiency of the anode, Ti/SnO2-Sb2O5/PbO2-PVDF(1.0wt%), had significantly improved. However, considering the life of the modified anode and energy-saving, current density and voltage should be controlled within30mA/cm2and10V respectively.
Keywords/Search Tags:Electrochemistry, Perfluorooctanoic acid, Dimensionally Stable anode, Lead dioxide, Polyvinylidene fluoride
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