The Study On Electrochemical Synthesis Of Ferrate And Oxidation Processes For Landfill Leachate

Landfill leachate is a kind of complex organic wastewater,Since the fluctuation of quality and quantity,full of harmful pollutants, it is difficult to dispose. There is still not an efficient method for the processing of it. Ferrate(VI) is a strong and environmentally friendly oxidant, coagulant, and water treatment agent, which lead to its unprecedented future practical application in many fields.In this paper, the preparation of Ferrate(VI), the stability of Ferrate(VI), treatment of landfill leachate with Ferrate(VI) and electrolysis was studied.The experimental results showed that:①On the same conditions, the current efficiency for producing ferrate(VI) was higher in NaOH than in KOH.At T=30℃,I=50mA/cm2 in 14 mol/L NaOH,for 60min electrolysis,between these parameter supporting a high current efficiency and a high concentration of ferrate(VI).②The stability of ferrate(VI) could be improved with NaOH and high pH。The higher the alkalinity was, the slower the decomposition speed of ferrate(VI) was. The ferrate(VI) stability increases with the temperature reduces.③The COD,NH3-N,chroma removal ratio increases with the augment of quantity of ferrate(VI).④Acidity condition was suitable for removing COD and alkaline condition was suitable for removing NH3-N in landfill leachate.⑤With testing the influence factors for the removal ratio of COD,NH3-N in landfill leachate, the order was: the NaOH quantity>intensity of current>electrolysis time and the NaOH quantity>electrolysis time>intensity of current. The result was following: the COD removal ratio could reach 72.61% when NaOH quantity was 7g, I=1.5A and electrolysis time was 15min; the NH3-N removal ratio could reach 65.01% when NaOH quantity was 7g, I=0.5A and electrolysis time was 45min.⑥This experiment select the best electrode spacing is 20mm, The removal ratio of COD and NH3-N could raise to 68.62% and 70.01% respectively when the NaOH quantity was 7g. Later, with the NaOH quantity increasing,the removal ratio was reduced⑦The COD, NH3-N removal ratio increases with intensity of current enhances, after the strength of current achieved 1.5A, continues to increase the intensity of current, the removal ratio increase slowly, the experiment chooses the best strength of current is 1.5A.⑧The removal ratio of COD and NH3-N could raise to 60% respectively when the electrolysis time was 60min. In the electrolysis process may consider the concentration of waste water to adjust the electrolysis time.⑨After uses the optimized parameter to electrolyze landfill leachate, the removal ratio of COD and NH3-N could raise to70%, chroma could raise to 88%.To the low concentration landfill leachate, it was no need to consider thecirculation electrolysis;But regarding the highly concentrated landfill leachate, electrolysis 4 may obtain a good effect.⑩In summary, the ferrate(VI) and the on-line electrolysis to process landfill leachate,shows good effect in the aspect of remove COD, NH3-N and chroma. And in this experiment COD, NH3-N primitive concentration are all high, after processing, achieved a better effect.