Study On The Reduction Mechanism Of Zn(II)-NH 4 Cl Quasi-Neutral System Zinc Ion On Zinc Electrode

High iron concentration is a characteristics of zinc oxide ore and secondary zinc resources,some of which contain some other impurity,such as silicon,fluorine,chlorine and so on.There are some disadvantage for the traditional hydrometallurgy of zinc,for example difficulty purification of leaching solution,serious accumulation of fluorine and chlorine,long process etc.In recent years,many researchers have studied ammonia leaching leached of zinc oxide ore and part of the secondary zinc resources,but electrode process theory research of ammonia leaching system is in its infancy.Zn（Ⅱ）—（NH3）—NH₄Cl system have been selected as an electrolytic system in this paper,which is ammonia leaching method and has been the most studied and basically mature.Zn2+ reduction mechanism studied on the zinc electrode in the improved system.These adopt cyclic voltammetry compared the differences between zinc ions reduction on the gold electrode and zinc electrode on the based on the basis electrochemical theory and test theory.The zinc electrode has been adopted as deposition electrode of Zn2+ and Parsed the reaction mode of Zn2+ on the zinc electrode.The influence of several factors on Zn2+ reduction have been studied by linear sweep voltammetry and Chronocoulometry.Then the electrode surface of state that close to equilibrium system of Zn2+ have been studied by application of small potential step chronoamperometry.With large step potential chronoamperometry and electrochemical impedance spectroscopy examines the Zn2+ sedimentary mode of nucleation and impedance behavior on the deposition stages in zinc electrode have been studied.Finally,the Zn2+ reduction with impact of impurity ions have been studied with cyclic voltammetry.The results show that in zinc（Ⅱ）-NH₄Cl quasi neutral system,Zn2+ reduction reaction rate on the zinc electrode faster than the gold electrode,the reduction method to get two-step electronics and the first step for the speed control step,Improving the electrolyte temperature and zinc ion concentration can play a role in the reduction of Zn2+ of polarization effect,strengthening the stirring intensity can promote the reduction of Zn2+,but it will not change its depositional mechanism.To improve the concentration of NH₄+ concentration increase of Zn2+ reduction from depolarization.Rising electrolyte temperature will increase the electron transfer coefficient of the hydrogen evolution reaction and improving zinc electrode potential will accelerate hydrogen evolution reaction.Zn2+ on the surface state of the electrode that close to the equilibrium system is instability.Zn2+ is deposited on the zinc electrode to a three-dimensional instantaneous nucleation manner and in the various stages of the deposition solution impedance change is small.Diffusion resistance and electrochemical impedance change is bigger.Culminating in a large number of deposits in the electrochemical polarization-concentration polarization mixing control phase.Cd2+,Fe2+ in 80mg/L when deposited on Zn2+ was not significant and 80 mg/L of Ni2+ and Co2+ have bigger influence on the Zn2+ deposit.