氨络合物体系电积锌的阴极过程

Cathodic process of zinc electrowinning insolution containing ammonia complex

采用CHI650电化学工作站测定了在锌氨络合物体系中锌电沉积的稳态阴极极化曲线及电流—时间暂态曲线。结果表明:锌的阴极电结晶过程是以瞬时成核方式进行的,随外加电位负移,晶体的向外生长速率增大;添加剂的加入不会改变锌阴极电沉积的成核方式,但将大大减小晶体的向外生长速率。通过对不同NH3浓度下测得的阴极极化曲线的分析,可获得各条件下的平衡电位,以及阴极过程动力学参数(交换电流密度J0、传递系数α),进而推导出溶液中存在的主要离子为Zn(NH3)2+4,在阴极直接放电的络离子为Zn(NH3)2+2。

The cathodic process of zinc electrowinning in solution containing ammonia complex was studied by cathodic polarization and chronoamperometric method, which were tested with CHI650 electrochemistry lab. The experimental results show that, the electrocrystallization of zinc follows the mechanism of instantaneous nucleation, and the crystal growth rate increases with negative shift of applied potential. No obvious change in nucleation modes is found with the addition of additive, while its growth rate decreases deeply. According to equilibrium potential and dynamic factors, such as exchange current density and transfer coefficient, it is proved that the ion discharging at the cathode directly is Zn(NH_3)^(2+)_2; while the main species of complex is Zn(NH_3)^(2+)_4 in the solution.