Study On Preparation Of Potassium Ferrate And Its Application In Original Water Treatment

Potassium ferrate is a new type of water treatment chemicals. It has been widely used, especially in the field of water treatment, because of its multi-functional, safe and high efficiency. So potassium ferrate has broad application prospects. However, the preparation process of potassium ferrate is very complex, and its solution has poor stability. All of these shortcomings have seriously affected the application of potassium ferrate. There is no comprehensive process date about large-scale production and application.In order to learn more ahout the accessibility of potassium ferrate, and its feature of water treatment. Preparation of potassium ferrate by hypochlorite oxidation, and the stability of solution were investigated. Potassium ferrate using in manganese and turbidity removal of water treatment was also studied.Firstly, the various factors in the preparation process were investigated to define their effect on the yield of potassium ferrate. The optimum condition of the preparation process can be determined from the experiments:temperature was 25℃, reaction time was 50min, the chlorine content of potassium hypochlorite sulution was 12% to 14%, the molar rate of potassium hypochlorite and ferric nitrate was 2.5. Secondly, the stability of potassium ferrate solution was investigated. The results showed that the stability of potassium ferrate solution was proportional to the alkali concentration and purity of potassium ferrate, and inversely proportional to the temperature and initial concentration of the solution.The removal of manganese in simulated water using potassium ferrate was studied. The experimental results showed that in the condition of using potassium ferrate only, the average removal rate of manganese can reach more than 80%, it was much better than polymeric aluminum chloride(PAC) or polymeric ferric sulfate(PFS), when using the same dose. Temperature and reaction time had less effect on the removal rate when potassium ferrate used only to remove manganese. When the pH around 8, better removal rates can be achieved in this experiment. The results of potassium ferrate pre-oxidation and PAC. PFS coagulation experiment showed that the join of potassium ferrate not only improved the removal rate of manganese, but also reduced the dosage of PAC and PFS largely.Several typical original water in Nanjing were used to study the efficiency of treatment using potassium ferrate. The results showed that a better removal rate of manganese and turbidity can be achieved using the method of potassium ferrate pre-oxidation and PAC coagulation. Low dosage of potassium ferrate did not bring better removal rate of permanganate index(CODMn), the removal rate was 30%-40% only.Potassium ferrate with high purity and yield was prepared by hypochlorite oxidation. The law on stability of potassium ferrate solution was defined. The obtained potassium ferrate was used to remove manganese and turbidity in water, and achieved good results. All these experiments provide a theoretical support for the pratical application of potassium ferrate.