Influence of manganese on the electrochemical behavior of an aluminum cathode used in zinc electrowinning
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摘要: 傳統濕法煉鋅工藝采用純鋁板作為陰極,但隨著鋅精礦品位的降低,電解液中雜質離子含量增大,造成陰極腐蝕消耗增加.本文以鋁錳合金為研究對象,研究錳作為添加元素,與鋁形成良好鋁錳合金陰極材料的電化學行為,進一步提高鋁陰極的耐蝕性和電催化活性.采用交流阻抗、陰極極化曲線、恒電流極化曲線、塔菲爾曲線等分析方法,探討不同Mn元素含量對鋁錳合金在40℃恒溫條件,Zn2+ 65 g·L-1和H2SO4 150 g·L-1溶液中電化學行為的影響.研究結果表明:相比純鋁電極,添加Mn元素的鋁錳合金電極的耐蝕性普遍提高,腐蝕電流均減小;隨著Mn含量的增加,腐蝕電流逐步降低,腐蝕電位與Mn含量增加無明顯變化規律;當Mn質量分數為1.5%時腐蝕電流達最低(1.11 mA·cm-2),腐蝕電位最小(-1.0954 V);零電勢下,表觀電流密度i0受Mn元素的添加影響顯著,i0隨Mn含量增加呈現出先增大后減小的趨勢,在Mn質量分數1.5%時達到最大值3.7462×10-16 mA·cm-2,遠大于純鋁電極4.8027×10-33 mA·cm-2,整體變化幅度明顯,電極的電催化活性得到提高;不同電流密度下的析氫過電位和純鋁電極的整體接近,電化學過程均為電化學傳質步驟控制.綜合考慮電極材料的耐蝕性和電催化活性,含Mn質量分數1.5%的鋁錳合金可作為理想的電積鋅陰極使用.Abstract: 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.
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參考文獻
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