The Conversion Between The Different Valence State Of Iron And Iron Hydroxide Residue After Treatment

Ferrate(VI)is a powerful oxidant,It is potentially used in the environmental protection,water purification and "green" high energy battery et al. Although the ferrate(VI)is instability,unlike the stability of chiorine,which prohibits its entensive use. In order that the ferrate(VI)can be used wildiy,the fundamental research on the ferrate(VI)is very imporment.In the long time,people have thought the ferrate(VI) was decomposed into oxygen and ferric hydroxide precipitation,but it has been proved to be imperfect recently. In this article, A process in which Fe(III) was converted to Fe(VI) Fe(IV) was were traced using spectrophotometry method, and several new reactionsw were found, this not only deepens understanding about the reaction during the ferrate(IV,V and VI) ,but also provides basis for establishing the ferrate chemistry; Then ferric hydroxide precipitation remained after this process was after treated, the result has positive meanings to practical application of ferrate.Firstly, Five different compounds (ferric hydroxide,potassium fluoferrite,polyferric sulfate,ferric nitrate and ferric chloride)reacted respectively at 80℃with sodium hypochlorite in the high alkaline. When reactions were traced using spectrophotometry method, the ferric compounds were oxidized firstly to ferrate(VI), the ferrate(VI)solution was decomposed into ferric hydroxide precipitation and at the same time the purple ferrate (VI) solution was converted into the green ferrate (IV) solution in the reaction system of polyferric sulfate,potassium fluoferrite and ferric hydroxide ; but the ferrate(VI)solution was decomposed only into ferric hydroxide precipitation in the system of ferric nitrate and ferric chloride . In the system involved with polyferric sulfate and ferric nitrate, the highest concentration of ferrate (IV) (C_Fe(IV)= 1.25×10^-3mol·L^-1)was formed with polyferric sulfate system while the highest concentration of ferrate (VI) (C_Fe(IV)= 0.23mol·L^-1)was generated was the highest(C_Fe(IV)= 0.23mol·L^-1)was was generated for the ferric nitrate system.Secondly, Five different dosage of ferric compound reacted respectively at 80℃with sodium hypochlorite in the high alkaline. When reactions were traced using spectrophotometry method ,the ferric compounds were oxidized firstly to the purple ferrate(VI) solution .Then the ferrate(VI)was decomposed into ferric hydroxide precipitation and at the same time the ferric compounds was oxidized into ferrate(IV) by the ferrate(VI)in the reaction system .The green ferrate(IV) solution was more stable,and the concentration of ferrate(IV) was increased with the rising of dosage of ferric compound.Lastly, After the aforementioned reaction, the dregs of ferric hydroxide remained was converted into potassium fluoferrite firstly. Then the potassium fluoferrite was put into the high-alkali solution of sodium hypochlorite and ferrate (VI) was generated again. The colored water containing methyl orange was treated with the ferrate (VI) solution containing fluorion. The best pH value was about 7.0 in treated water, and 500mL colored water containing 20mg·L^-1 methyl orange could be treated well with 17mg potassium ferrate (VI). The results showed that not only the decolorizing efficiencies were above 95%, but also the residual quantity of fluorion in the treated water meeted the national effluent standards.