锌电积过程中锰元素对铝阴极的电化学行为影响

传统湿法炼锌工艺采用纯铝板作为阴极,但随着锌精矿品位的降低,电解液中杂质离子含量增大,造成阴极腐蚀消耗增加.本文以铝锰合金为研究对象,研究锰作为添加元素,与铝形成良好铝锰合金阴极材料的电化学行为,进一步提高铝阴极的耐蚀性和电催化活性.采用交流阻抗、阴极极化曲线、恒电流极化曲线、塔菲尔曲线等分析方法,探讨不同Mn元素含量对铝锰合金在40℃恒温条件,Zn2+ 65 g·L-1和H₂SO₄ 150 g·L-1溶液中电化学行为的影响.研究结果表明:相比纯铝电极,添加Mn元素的铝锰合金电极的耐蚀性普遍提高,腐蚀电流均减小;随着Mn含量的增加,腐蚀电流逐步降低,腐蚀电位与Mn含量增加无明显变化规律;当Mn质量分数为1.5%时腐蚀电流达最低(1.11 mA·cm-2),腐蚀电位最小(-1.0954 V);零电势下,表观电流密度i₀受Mn元素的添加影响显著,i₀随Mn含量增加呈现出先增大后减小的趋势,在Mn质量分数1.5%时达到最大值3.7462×10-16 mA·cm-2,远大于纯铝电极4.8027×10-33 mA·cm-2,整体变化幅度明显,电极的电催化活性得到提高;不同电流密度下的析氢过电位和纯铝电极的整体接近,电化学过程均为电化学传质步骤控制.综合考虑电极材料的耐蚀性和电催化活性,含Mn质量分数1.5%的铝锰合金可作为理想的电积锌阴极使用. 

Influence of manganese on the electrochemical behavior of an aluminum cathode used in zinc electrowinning

Pure aluminum is commonly used as the cathode electrode in the traditional hydrometallurgy applications of zinc electrowinning. However, with the decrease of zinc concentrate grade and increase of the impurity ions in the electrolyte, the corrosion consumption of the cathode material increases gradually. To further improve the corrosion resistance and electrocatalytic activity of the aluminum cathode, the electrochemical behavior of manganese as an additive for pure Al cathode material, such as Al-Mn alloy, was studied herein. Using the analysis methods of electrochemical impedance spectroscopy, cathodic polarization, galvanostatic polarization, and Tafel curves, the effect of Mn content on the electrochemical behavior of Al-Mn alloy in 40℃ constant temperature conditions and a solution containing Zn2+ at 65 g·L-1 and H₂SO₄ at 150 g·L-1 was investigated. The results show that the corrosion resistance of Al alloy containing Mn increases obviously compared to that of pure Al electrodes, and the increase of the Mn content could decrease the corrosion current. Moreover, the corrosion potential and the Mn content do not exhibit obvious change trends. When the Mn content reaches 1.5%, the corrosion current reaches the lowest value of 1.11 mA·cm-2 and the corrosion potential reaches the minimum of -1.0954 V. When the electrical potential of cathode becomes zero, the exchange current density is influenced by the Mn content and the exchange current density i₀ exhibits an initial increasing trend and then declines with the increase of the Mn content. When the Mn content is 1.5%, the exchange current density of the Al alloy cathode reaches the maximum of 3.7462×10-16 mA·cm-2; this value is much higher than that of the pure Al electrode (4.8027×10-33 mA·cm-2). The overall change amplitude is obvious, and the electrocatalytic activity of the Al-Mn electrodes is much improved compared with a pure Al electrode. The electrochemical process is controlled by the electrochemical mass transfer. Considering the corrosion resistance and electrocatalytic activity of the electrode material, the Al-Mn alloy containing 1.5% of Mn can be used as an ideal electrolytic zinc cathode.