Study On Preparation Of Potassium Ferrate By Chemical Oxidation Method And Its Application In Organic Wastewater Treatment

The preparation and stability of potassium ferrate is studied, as its harsh preparing condition,terrible stability. Potassium ferrate is used to dispose organic wastewater.The influence of hypochlorite concentration,ferric salt dose, reaction temperature,reaction time,follow up depuration processes etc. on yield and purity of potassium ferrate is studied by hypochlorite oxidation method. Potassium ferrate with purity of 96.4%, yield 45.3% is prepared, when initial hypochlorite concentration is 137.3g/L, reaction time is 1 hour and ferric dose is as 30% as stoichiometric in water bath. Follow up depuration processes such as concentration of KOH in 2nd depuration,separating out time,washing solvent etc. also produce an effect on the purity and yield of potassium ferrate. The sample is characterized by XRD,FIRT and SEM. Results show that product is potassium ferrate crystal. Determination of potassium ferrate by redox titration based on the oxidation of chromate is improved. The maximum absorption wavelength is 510nm, when concentration of potassium ferrate solution is determined by ultraviolet spectrophotometry.Potassium ferrate solution containing KOH, KCl, KNO₃, Fe(NO₃)₃,KClO and additional ions are used to investigate the effect of the coexisting ions on the ferrate stability which lays the foundation of screening stabilizer for potassium ferrate. It is found that the stability of ferrate(â…¥) solution increases with increasing alkalinity, KCl, KNO₃ have a little effect on the stability of ferrate(â…¥), hypochlorite retards the ferrate decomposition significantly, but potassium ferrate decomposes more rapidly with the coexisting ion of ferric. The stability of potassium ferrate can be increased when KIO₄,NaSiO₃, CuCl₂ are added respectively. Stabilizer composed of KIO₄ and NaSiO₃ plays the greatest part in the stability of potassium ferrate solution. KIO₄ has no collective effect on retarding the ferrate decomposition with NaSiO₃,KClO or CuCl₂. Influence of stabilizer which is made up of NaSiO₃ and CuCl₂ is not apparent as KClO on stability of potassium ferrate.When the initial concentration of nitrobenzene is 55.04 mg/L, pH= 9.0, controlling reaction time as 30min, the removing efficiency of potassium ferrate to nitrobenzene (mole ratio is 10:1) can attain to probably 85% and 55%. Changing pH in reaction, the removing efficiency of nitrobenzene and CODcr both come up to a fairly level, the former reach to 98.2%, the latter to 91.9%. Degradation solution is analyzed by ultraviolet spectrum, FIRT, GC/MS Spectrum etc.. The results show that no refractory material is generated during nitrobenzene's degradation, aliphatic hydrocarbon is its terminal product. Mechanism of nitrobenzene degradation is preliminarily investigated. In order to achieve the goal of low-cost, high-removing efficiency, it's better to apply potassium ferrate with other water treatment agents in nitrobenzene wastewater treatment, as its high disposing expenditure.When the initial concentration of aniline is 62.04 mg/L, pH=9.0, controlling reaction time as 20min, the removing efficiency of potassium ferrate to aniline (mole ratio is 1:1) can attain to 91.03% and 56.14% respectively. Changing pH in reaction, has little influence on the removing efficiency of aniline, but removing efficiency of CODcr come up to 94.8%. Degradation solution is analyzed by ultraviolet spectrum,FIRT,GC/MS Spectrum etc.. The results show that Azobenzene is generated as intermediate product during aniline's degradation. Finally, aniline is decomposed into aliphatic hydrocarbon. Mechanism of aniline degradation is also discussed. The cost of 1 ton aniline wastewater treatment is 19.99 yuan.Dong Juan(Environmental Engineering)Supervised by Vice Professor Wang Yonghui...