DDTC 体系中黄铁矿电极过程动力学的研究

在pH 值为11.4 的二乙基二硫代氨基甲酸钠(DDTC)体系中, 采用循环伏安电位扫描、恒电位阶跃和计时电位法研究了黄铁矿的电极过程。循环伏安曲线表明, 当c(DDTC)=1 ×10^-4 mol/L 时, 电极电位大于0.2V(SHE)以后, 黄铁矿电极表面发生四乙基二硫化秋兰姆(TETD 或D₂)的电化学沉积并残留在电极表面;采用恒电位阶跃法可以确定反应电流密度(i)与反应时间(t)之间的关系式为i =(9.08 ×10^-5 +4.77 ×10^-3 t^0.5)^-1, 由此可以确定DDTC 在黄铁矿电极表面的扩散系数D为3.72 ×10^-6 cm²/s, TETD 在黄铁矿电极表面的吸附厚度可达1.63 个单分子层;计时电位法则确定了pH 为11.4 时, 吸附于黄铁矿电极表面的TETD 的电化学动力学方程为η=0.116-0.064 lg[1-(t/τ)^0.5], 电化学动力学参数确定为:交换电流密度i₀ =3.08 μA/cm², 反应电子数n=2, 反应传递系数α=0.462。电化学动力学方程和电化学动力学参数值表明吸附于黄铁矿电极表面的TETD 易于还原。

Kinetics of Electrochemical Process of Pyrite Electrode in Diethyldithiocarbamate Solution

The electrochemical process of pyrite electrode in diethyldithioc arbama te (DDTC) solution with a pH value of 11.4 has been investigated using cyclic vo ltammetry, Potentiostatic method and Chronopotentiometry. At 1×10-4 mol/ L of DDTC the electrodepotential is higher than 0.2 V, resulting in electroch emical deposition of tetraethyl thioram disulphide (TETD) on pyrite surface. The depend ence of current density (i) on reaction time (t) is established using po tentiostatic method as follows: i=(9.08×10-5+4.77×10-3t 0.5)-1. From this the diffusion coefficient, D of DDTC on pyrite s urface in the DDTC solution is ascertained as about 3.72×10-6 cm2/s, a nd the thickness of TETD adsorbed on pyrite surface is about 1.63 molecule layers. The electroc he mical dynamic equation of adsorption of TETD on pyrite surface at pH 11.4 is es tablished as η=0.116-0.064 lg［1-(t/τ)0.5］ and the electroche mical kinetic parameters are determined as follows: exchange current density, i0=3.08 μA/cm2；reaction electron number, n=2 and transmission coeffi cient, α=0.462.