Study On Pre-oxidation Of Divalent Manganese By Potassium Ferrate In Natural Water

There are a serious shortage of water resources in China.The per capita water resource is only 900m³and the distribution is extremely uneven.It is one of the most poorest country in the world.Iron-manganese groundwater contains about 20%of total groundwater,and the contamination incidents of manganese in surface water occurs time to time.In recent years,ferrate has gained continual attention by its excellent oxidation and environmental friendliness.Compared with traditional oxidants?Cl₂,?ClO₂,?KMnO₄?,ferrate has strong oxidant activity and selectivity,but it's application has been limited due to cumbersome preparation and poor stability.At present,there have been many studies on removal of heavy metals by ferrate?As?II?,Co?II?,Ni?II?,Cu?II??,but the study on removal of Mn?II?by ferrate in natural waters was still relatively scarce.What lacks more is the dynamic analysis and reaction mechanism of Fe?VI?with Mn?II?.In this paper,the experiment of ferrate stability analysis was found that the decomposition is affected by many factors,such as concentration,pH,temperature and zwitterion.In order to achieve the determination method of ferrate,the Flame atomic absorption?FAAS?was introduced,compared with the traditional method and used t-test analysis to dissect the result.The results reflect that the content of potassium ferrate was determined by FAAS is feasible and reliable.At the same time,the experiment of removing Mn?II?by potassium ferrate?K₂FeO₄?found that under the conditions of[K₂FeO₄]/[Mn]=2:3,pH=8.1,and the temperature was 25°C,the optimum removal of manganese was achieved,the removal rate of Mn?II?reached 89.23%,the manganese content was 0.02 mg/L.However,by the experiment of Mn?II?and potassium ferrate with Na₂SO₃ and NaNO₂,found that SO₃^2-can increase the ability of potassium ferrate to remove Mn?II?.And by adding free radical inhibitors such as tert-butanol?TBA?and ethanol?EtOH?,also proved that the descend of Mn?II?was due to the generation of SO₄·^-and·OH.In order to explore the role of NOM in K₂FeO₄/Mn?II?system,the experiment of potassium ferrate and Mn?II?in various water was carry out.It was found that fulvic acid does not improve the removal rate of Mn?II?,but it increased significantly?about 10%?in natural water.Analyze the cause:humic acid?HA?and fulvic acid?FA?have different structure and composition,which may make two substances show aopposite characteristics.On the other side,there are many reducing matter in natural water that can react with K₂FeO₄ to produce active components,increasing the removal rate of Mn?II?in solution.