Synthesis And Application Of Potassium Ferrate(Ⅵ) For Oxidizing Degradation Of 2-sec-Butyl-4,6-Dinitrophenol (DNBP)

2-sec-butyl-4,6-dinitrophenol (DNBP) is widely used as pesticide, herbicide and polymerization inhibitor for aromatic vinyl compounds. A mass of highly toxic and less degradable nitrophenol waste effluents are generated in the process of DNBP production. The waste water has caused not only many serious environmental problems, but also hindered further development of these production industries. At present, the treatment of DNBP wastewater has not been studied extensively owing to difficulties with its degradation. In the paper, an efficient and multifunctional water treatment chemical reagent, namely potassium ferrate(VI), was synthesized and used for the treatment of DNBP wastewater. Potassium ferrate(VI) can perform superiorly in degrading and oxidizing various organic contaminants, disinfecting microorganisms, removing colloidal/suspended particulate materials. More importantly, ferrate(VI) is also an environmental friendly treatment chemical, which will not produce any harmful by-products in the treatment process. This research provides the potential application of ferrate(VI) as a new and efficent chemical reagent for the treatment of DNBP wastewater. The research in this paper involves the following three parts.In the first part of this paper, the solid phase potassium ferrate of high purity (96～98.5%) was prepared by the improved wet method by which ferric nitrate was oxidized under strong alkaline conditions and hypochlorite was used as an oxidant. Potassium hydroxide, ferric nitrate, chlorine gas, etc. was selected as the raw materials for synthesizing potassium ferrate(VI). The synthesized ferrate(VI) compound was characterized by means of X-ray powder diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and TG-DTA analysis.The aqueous stability of potassium ferrate at various pH values, temperatures and different concentrations was investigated in the second part of the paper. The experimental results showed that ferrate solution at low concentration was more stable than at high concentration. The stability of potassium ferrate solution increased with the pH value increase and temperature decrease. Meanwhile, the influence of various ions on the stability of ferrate solution was also studied and it indicated that the stability of the oxidant Fe(VI) could be enhanced greatly by the addition of potassium chlorate in aqueous solution.In the third part of the paper, the application of potassium ferrate in the treatment of DNBP wastewater was discussed. The effects of various factors, such as temperature, reaction time, pH value and a mass ratio of Fe(VI) : DNBP on the degradation of DNBP were studied throughly. It ws found that the optimal temperature and pH value for DNBP degradation was 30℃and 6.5, respectively, and under this condition and a Fe(VI) : DNBP mass ration of 20: 1, approximately 90% of the DNBP was degraded after 4h. The experimental results also showed that the COD_cr of DNBP wastewater decreased from the original 20mg/L to 18mg/L when the mass ratio of K₂FeO₄ : DNBP reached to 2 : 1. The COD_cr of the solution was lower than 3mg/L when the mass rate of K₂FeO₄ : DNBP reaches to 20 : 1, which can meet the effluent standard for chemical industry.