A Study On Treatment Characteristics Of Landfill Leachate By In-Situ Ferrate Generation Electrocatalytic Oxidation

Aiming at the problem of low biodegradability of landfill leachate,this study put forward an in situ Ferrate generation Electrocatalytic process（FEC）for landfill leachate,which adopts iron and DSA double anode arrangement to electrolyze in-situ ferrate,and combines ferrate with electrocatalytic oxidation.The efficient transformation and removal of refractory pollutants in landfill leachate were realized,and the transformation law and mechanism of organic matter in FEC process were found out.The research results can provide new ideas for biochemical improvement and treatment of landfill leachate.In this study,iron and DSA were used as double anodes,and stainless steel was used as cathode.By adding Na OH,Fe³⁺generated by anodic electrolysis reacted with OH^-to generate Fe（OH）₃.At the same time,Cl^-generated active chlorine in anodic oxidation and reacted with Fe（OH）₃to generate ferrate in situ.By changing the current density（0,4,8,12.5,17 m A/cm²）,Na OH dosage（0,5,7.5,10,12.5 g/L）and electrode arrangement（iron and DSA double anode,double iron anode,single iron anode,double DSA anode and single DSA anode）,the dissolved COD and NH₄⁺-N in landfill leachate were found out.Under the optimum conditions of arranging iron and DSA double anodes,current density of 12.5 mA/cm²,adding 10 g/LNa OH and reacting for 60 min,the removal rates of dissolved COD and NH₄⁺-N in landfill leachate are the highest,which are 50.94%and 38.11%respectively.Based on the optimization of reaction conditions of FEC process,the organic transformation law of FEC process was explored by three-dimensional fluorescence,molecular weight,B/C and high resolution mass spectrometry（FT-ICR-MS）analysis.The results show that FEC process can remove humic acids from landfill leachate,and transform larger molecules of humus and protein-like dissolved organic substances into small molecules of organic substances,thus improving the biodegradability of landfill leachate.After FEC treatment,the low-oxygen phenolic compounds in landfill leachate were significantly removed,the contents of aliatic compounds decreased,and the proportion of CHO,CHNO and CHOCl decreased.By measuring the concentration of ferrate and active chlorine,X-ray diffraction（XRD）,Fourier infrared（FT-IR）,X-ray photoelectron spectroscopy（XPS）analysis and Electron paramagnetic resonance（EPR）,it was proved that there were active species such as ferrate,active chlorine and·OH in FEC process.The results of kinetic analysis and quantitative calculation show that Fe（Ⅵ）can remove organic matter through the oxidation of intermediate species Fe（V）and Fe（IV）and the coagulation of hydrolysis product Fe（OH）₃,and Cl O^-indirect oxidation and·OH direct oxidation can simultaneously degrade organic matter,in which Fe（Ⅵ）oxidation plays a leading role and the contribution rate is as high as 62.77%under the optimal reaction conditions.