Ferrate (Ⅵ) is generated by the electrochemical oxidation of porous magnetite electrodes, made by melting pure magnetite grain. Pretreatment of the anode by cathodic polarization is necessary for ferrate (Ⅵ) generation and the achievement of high current efficiency at magnetite electrode. An optimum synthesis electrolyte is observed to be 16 mol·L-1 NaOH. In this electrolyte the effects of anode current density, J, on Fe (Ⅵ) synthesis rate, current efficiency and internal cell temperature are studied. An optimum result is obtained at J=3.3 mA·cm-2, 30 ℃ in 16 mol·L-1 NaOH for 5 h.
采用快速电合成技术可有效获得ω((K2FeO4)为93%～98.1%的晶体,通过现代仪器分析(AAS,XRD,SEM,IR,TGA和DTA)表征了样品.发现样品具有以下性质:XRD八条强线d(pm)值为298x,2593,4323,3083,5213,4273,2942,2262;晶体较粗(50～100μm),呈长而薄的正交晶形;在4 000～400cm-1之间IR特征峰为三重强峰(815,791,774cm-1)和单重弱峰(1 571cm-1);热稳定性高于536K.
Cyclic voltammetry (CV) curves for the redox couple of Fe(Ⅵ)/Fe(Ⅲ) were measured using stationary glassy carbon (GC) electrode. The solutions of Na_2FeO_4 and NaFeO_2 in concentration range of 0.015～0.06 and 0.01～0.025 mol·L~(-1) respectively, in 13 mol·L~(-1) NaOH, and the mixtures of solid K_2FeO_4 or solid KFeO_2 and colloidal graphite, adhered to the surface of the GC electrode, in 13 mol·L~(-1) KOH, were studied. The anodic current peak at 0.7～1.0 V and the cathodic current peak at 0.15-0.2 V vs. Hg/HgO(13 mol·L~(-1) NaOH or KOH) were proved to be correspond to the formation and to the reduction of Fe(Ⅵ) respectively. The experimental conditions for separating the anodic current corresponding to the formation of Fe(Ⅵ) and that to the evolution of oxygen were determined.
