Preparation Of High Efficiency Lead Dioxide Electrode And Study On Pretreatment Of Coal Gasification Wastewater

Coal gasification wastewater?CGW?contains a large number of toxic substances inc luding phenols,long-chain alkanes and etc,which are difficult to degrade.After traditional physical and chemical pretreatment,it still contains a large number of toxic pollutants which are difficult to degrade.Because of the excellent oxidation characteristics,electrocatalytic oxidation technology can efficiently remove organic pollutants which are difficult to biochemical treatment,and has a certain development trend.In order to study the efficiency of electrocatalytic oxidation on pretreatment of coal gasification wastewater,doped lead dioxide electrode was successfully prepared,and lead dioxide anodic catalytic oxidation was used to pretreat coal gasification wastewater to remove and transform refractory organic compounds.In this paper,the catalytic oxidation performance of the lead dioxide electrode was improved by doping PEG and Bi.The lead dioxide electrode was cha racterized by SEM,EDS and XRD and the electrochemical performance was tested by LSV curve,CV curve and EIS.The ability of the lead dioxide electrode to produce·OH was tested by fluorescence spectrometry.The degradation efficiency of CGW was investigated by TOC,total phenol,ultraviolet-visible spectra and three-dimensional fluorescence spectra and the biodegradability and the toxicity of CGW wastewater were expressed by dehydrogenase activity and acute toxicity of luminescent bacteria,respectively.Gas chromatography-mass spectrometry?GC-MS?and high performance liquid chromatography?UPLC?were used to analyze the concentration changes of organic species and pollutants.The results showed that the doping of PEG and Bi improved the surface morphology of PbO₂ and the reversibility and stability of the electrode,reduce d the impedance of the electrode,and significantly increased the formation rate of hydroxyl radicals.The degradation rate of phenol at the doped modified electrode was 76.78%in 3 hours,which conformed to the pseudo-first-order kinetics model and the rate constant was 0.00819.3,5-dimethylphenol,resorcinol and quinoline were selected as characteristic pollutants to explore the influencing factors and efficiency of electrocatalytic treatment of organic pollutants in coal gasification wastewater.Increasing current density and temperature would accelerate the removal of phenolic pollutants,but excessive current density and temperature would inhibit the degradation rate of pollutants.The optimum reaction conditions were 40mA/cm²,room temperature and 0.25mol/L of Na₂SO₄.The degradation rate of3,5-dimethylphenol was the fastest in the electrocatalytic system,followed by resorcinol and quinoline.The intermediate products in the degradation process were detected by GC-MS,and the possible degradation pathways of characteristic pollutant in the electrocatalytic oxidation system were proposed.The phenolic pollutants were well treated in the actual coal gasification wastewater.Considering the current efficiency and degradation efficiency of 40mA/cm² as the optimum current density,the wastewater at 45°C has the best degradation efficiency in the electrocatalytic oxidation system.With the prolongation of degradation time,the biodegradability first decreased and then increased,and the dehydrogenase activity increased from 29.87 nmol/h to 38.61nmol/h.The acute toxicity showed an overall upward trend,after 2 hours,the acute toxicity began to decline.A small amount of lead was leached out during the reaction,but the concentration was always lower than 1 mg/L,which would not affect the subsequent biological treatment.