难处理金矿浸出预处理过程的电位-pH图

E-pH Diagram of Pretreatment of Leaching for Refractory Gold Ore

通过热力学计算绘制了298.15 K下FeS2-H2O系、FeAsS-H2O系的电位-pH图,为难处理金矿浸出预处理过程中黄铁矿与毒砂的氧化分解提供了热力学依据.由FeS2-H2O系的电位-pH图可知,黄铁矿可以被O2等氧化剂氧化分解.在水的稳定区范围内,元素硫的稳定区较小,浸出预处理过程中硫基本上以HSO-4,SO24-形式存在.由FeAsS-H2O系的电位-pH图可知,毒砂比黄铁矿更容易被氧化分解.浸出预处理过程应提高氧化电位使毒砂中的砷和硫氧化至最高价脱去,避免亚砷酸盐和元素硫的生成.以难处理金精矿为原料进行加压氧化验证实验,在反应温度180℃、精矿粒度为-0.075 mm^+0.061 mm、氧分压为0.8MPa、初始酸质量浓度60 g/L、液固质量比4∶1、反应时间120 min、搅拌转速600 r/min条件下,金精矿的平均脱硫率93.85%,平均脱砷率为95.91%,实验结果与热力学计算结果一致.

E-pH diagrams of FeS2-H2O system and FeAsS-H2O system at 298.15 K were drawn to provide the thermodynamic basis for the pretreatment of pyrite and arsenopyrite before leaching.According to E-pH diagram of FeS2-H2O system,pyrite can be decomposed by O2 and other oxidants.The stable region of sulfur element is small and sulfur exists as HSO-4 and SO2-4 basically in the stable region of water.According to E-pH diagram of FeAsS-H2O system,the decomposition of arsenopyrite is easier than pyrite.Oxidation potential was improved to oxidize sulfur and arsenic to be removed and avoid the formation of arsenite and sulfur elements during the pretreatment process.Verification of pressure oxidation was carried out with refractory gold ore.When the temperature,concentrate particle size,oxygen partial pressure,initial acid concentration,liquid-solid mass ratio,reaction time and stirring speed are 180 ℃,-0.075~＋0.061 mm,0.8 MPa,60 g/L,4∶1,120 min andd 600 r/min respectively,average desulfurization rate is 93.85% and average arsenic removal rate is 95.91%.The experiment results are in good agreement with the calculation results of E-pH diagram.