1723K下熔渣中Ni~(2+)和Fe~(2+)离子共存时的电化学行为

利用MgO部分稳定的ZrO_2固体电解质管集成构建以Pt,O_2(空气)|ZrO_2作为参比电极的新型可控氧流电解池,采用循环伏安CV、方波伏安SWV、恒电位电解PE等方法,并结合热力学计算与显微观察、能谱分析,研究1 723K高温下SiO_2-CaO-MgO-Al_2O_3熔渣中共存的Ni~(2+)、Fe~(2+) 离子在Ir电极上的电化学行为。结果表明:熔渣系中FeO与NiO之间存在较弱的相互作用,但镍离子以Ni~(2+)存在,铁离子基本以Fe~(2+) 存在。进行方波伏安分析时,Ni~(2+)、Fe~(2+) 离子的还原峰电流对频率呈现不同的规律。Ni~(2+)在Ir电极上的电化学还原是扩散控制的一步两电子转移反应过程;Fe~(2+) 到Fe的电化学还原也是一步两电子转移反应过程,但Fe~(2+) 的还原明显受到Ni~(2+)还原的影响。基于循环伏安法,计算得到NiO、FeO的质量分数分别为3%、5%的熔渣中Ni~(2+)离子在1 723K下的扩散系数为(9.2±0.2)×10-6cm2/s。

Electrochemical behaviors of coexisting Ni2+ and Fe2+ions in molten slag

A novel electrolytic cell with a controlled oxygen flow was constructed integrally through a one-end-closed magnesia partially stabilized zirconia solid electrolyte tube with Pt,O2 (air)|ZrO2 used as reference electrode.Combined with thermodynamic calculation,SEM observation and EDS analysis,electrochemical behaviors of coexisting Ni2+ and Fe2+ ions in SiO2-CaO-MgO- Al2 O3 molten slag were investigated on the iridium electrode at 1723 K by means of electrochemical techniques including cyclic voltammetry (CV), square wave voltammetry (SWV)and potentiostatic electrolysis (PE).The results show that there is weak interaction between FeO and NiO in the molten slag system,but nickel ions exist in the form of Ni2+ and iron ions exist basically in Fe2+.When SWV is performed,the reduction peak currents of Fe2+ and Ni2+ ions ex-hibit different rules for the scan frequency.The electrochemical reduction of Ni2+ on the iridium electrode in the molten slag is a single two-electron transfer step,and the rate of the electrochemical reduction of Ni2+ is controlled by diffusion.The electrochemical reduction of Fe2+ is also a single two-electron transfer step,but the process is obviously affected by the reduction of Ni2+.The diffusion coefficient value of Ni2+ ions derived from CVs is (9.2 ± 0.2 )× 10 -6 cm2/s in the molten slag containing 3 mass% NiO and 5 mass% FeO at 1723 K.