Research On The Application And Improvement Of Potassium Ferrate In Landfill Leachate Treatment

The potassium ferrate has been developed as a new water treatment agent sincethe 1950s in the 20th century owing to its satisfying effects of oxidativedecontamination and flocculating, eminent sterilization and effective disinfection anddeodorizing functions. Furthermore, it will not bring secondary pollution to thetreated water. However, K₂FeO₄ has not been able to achieve large-scale industrialapplications due to the poor stability of potassium ferrate and the complicatedpreparation and the higher cost.Landfill leachate is a highly concentrated organic wastewater, with the complexwater quality, a wide range of organic compounds, high concentrations of pollutants,large range of water quantity, higher contents of metals and ammonia nitrogen.Moreover, the treatment process is very complicated and the cost is high.In this paper the potassium ferrate crystal has been synthesized with potassiumhypochlorite and ferric nitrate, and the purity reaches 98%. With the change of timeto its purity analysis, it showed that the stable preserved periods for potassium ferratecrystal is about 20 days. The experiments indicate that the optimize dosage for thepotassium ferrate crystal is four times to that of ammonia nitrogen, the pH value is 9,and the removal rate of ammonia nitrogen is almost free of the influence oftemperature. To landfill leachate treatment, the potassium ferrate crystal can remove60% ammonia nitrogen. But experiments found that the crystals of potassium ferrateleachate decomposed immediately when adding it to the landfill leachate, whichindicates its oxidation is not fullly accomplished.In view of the problems above, we switch to use the potassium ferrate filtrateand the loaded-type potassium ferrate to treat the landfill leachate. The experimentalresults show that: the potassium ferrate filtrate is a very good ammonia removal agent,and it also have a certain effect to remove COD_Cr and BOD₅. When 5 ml potassiumferrate whose concentration is 21.45 mmol/L was added to 100 ml landfill leachate,the removal rate of ammonia nitrogen, COD_Cr, BOD₅ could reach 80%, 46.5%, 70%respectively. The stability of a lower concentration of potassium ferrate filtrate is greatly improved, and only a small number decomposed in 60 days. The activatecarbon loaded-type potassium ferrate has a very good cooperated effect to remove theCOD_Cr from the landfill leachate. When the dosage is 15 g (the biggest releasecontent of potassium ferrate is about 9 mg), the removal of COD_Cr in 100 ml landfillleachate could reach 89%.This paper summarizes the advantages and disadvantages of three types ofpotassium ferrate products through the compare of their effects in the landfill leaehatetreatment. The results provide a scientific basis for the in-depth study of potassiumferrate, it has important theoretical value and significance for the practicaldevelopment of potassium ferrate products.