镁离子对低品位硫化镍矿氧化浸出电化学行为的影响

Effect of Magnesium Ion on Electrochemical Behavior of Low-Grade Nickel Sulfide Ore during Oxidation Leaching

低品位硫化镍矿中含镁硅酸矿物易被酸溶解出Mg^2+而影响其有价金属提取。采用不同氧化浸出体系研究了Mg^2+对硫化镍矿中Ni、Cu、Mg、Fe浸出的影响,利用循环伏安、动电位极化、交流阻抗等方法研究了Mg^2+影响硫化镍矿中硫化矿物氧化溶解电化学行为。结果表明,试验范围内,低品位硫化镍矿中硫化矿物氧化浸出受氧化产物扩散影响控制,含镁矿物被酸溶解释放出Mg^2+进入溶液,游离的Mg^2+受硫化矿物表面负电性离子吸引而吸附在矿石表面,降低矿物表面氧化溶解双电层电荷转移内阻,加速电荷转移过程;另一方面,由于Mg^2+吸附影响,使得硫化镍矿表面氧化产物膜致密生长而显著负影响硫化矿物浸出,致使硫化矿物自腐蚀速率随Mg^2+浓度增加而降低。Mg^2+对含S物种电对间转化不利,与Fe^3+协同影响硫化矿物氧化浸出效率,低Mg^2+浓度促进Fe^3+/Fe^2+循环,而高Mg^2+浓度引起硫化矿物腐蚀产物层致密生长而降低矿物被溶解的速率。硫化镍矿在不同体系氧化浸出时,初始含Mg^2+条件下,Ni、Cu、Fe浸出效率低于无Mg^2+体系。

Dissolution of magnesium from magnesium-bearing silicate minerals of low-grade nickel sulfide ores in acid leaching systems affects extraction of valuable metals.Effect of Mg^2+on oxidation leaching of nickel,copper,magnesium,and iron from low-grade nickel sulfide ore was studied in different oxidation acid leaching systems.Performance of Mg^2+on electrochemical behavior of sulfide minerals ore during oxidation leaching was investigated by method of cyclic voltammetry,potentiodynamic polarization,and alternating-current impedance.The results show that,in the test range,oxidative dissolution of sulfide minerals from low-grade nickel sulfide ore is controlled by diffusion of products.Magnesium minerals are dissolved by sulfuric acid generating Mg^2+in leaching liquor.Dissociative Mg^2+affects electron transfer and product diffusion in sulfide minerals oxidation leaching.Mg^2+absorbs electronegative points on surface of sulfide minerals,leading to an acceleration on charge transfer process due to decrease in charge transfer resistance of interface electric double layer.While,this absorption causes formation of corrosion products film tending to dense which has negative influence on sulfide minerals oxidation leaching.Self-corrosion rate of ore drops with increase of Mg^2+concentration.Presence of Mg^2+has poor effect on transform between sulfur-containing substances.Collaborative influence of Mg^2+and Fe^3+illustrates that low concentration of Mg^2+in leaching system facilitates cycle of Fe^3+/Fe^2+pair,and high concentration of Mg^2+reduces oxidizing leaching efficiencies of minerals because of densification of oxidation products layer.Leaching efficiencies of Ni,Cu,and Fe during oxidation leaching with existence of Mg^2+ insolutions are lower than those with absence of Mg^2+.