Department of Chemical Engineering and Applied Chemistry, University of Toronto, 200 College Street, Toronto, ON, Canada.
J Hazard Mater. 2011 Oct 30;194:399-406. doi: 10.1016/j.jhazmat.2011.08.012. Epub 2011 Aug 10.
High pressure oxidative acid leaching (HPOXAL) was successfully applied to slow-cooled converter slags from Vale's operations in Sudbury (Ontario, Canada). Extractions of Ni, Co and Cu exceeded 90% within 15-20 min and levelled at 95-97% after 45 min at 250°C, 90 psi O(2) overpressure and 70 g/L initial H(2)SO(4). Pyrrhotite tailings with ∼ 0.6% Ni content were also tested as a source of sulphuric acid in high pressure oxidation. Co-leaching of pyrrhotite tailings with converter slags at the same temperature, oxygen partial pressure and equivalent stoichiometric H(2)SO(4) was found to have kinetics similar to that of leaching with sulphuric acid. Lowering the addition of pyrrhotite tailings (and hence, the acidity) was found to have a detrimental effect on the kinetics of leaching and final extractions (especially at 250°C), and cause precipitation of metal sulphates. Continuous on-line acidity measurements were facilitated in experiments with an electrodeless conductivity sensor. It was shown that acid plays a major role in the conversion of fayalite to hematite and silica, and the dissolution of the base metals, while oxygen overpressure (or dispersion efficiency) determines the rate of acid generation and re-generation.
高压氧化酸浸（HPOXAL）成功应用于淡水河谷在安大略省萨德伯里（Sudbury）的转炉渣的缓冷处理。在 250°C、90 psi O₂过压和 70 g/L 初始 H₂SO₄的条件下，15-20 分钟内镍、钴和铜的浸出率超过 90%，45 分钟后达到 95-97%。还测试了含有约 0.6%镍的磁黄铁矿尾矿作为高压氧化中的硫酸源。在相同的温度、氧分压和等效化学计量的 H₂SO₄条件下，与转炉渣共浸磁黄铁矿尾矿，其动力学与用硫酸浸出的动力学相似。降低磁黄铁矿尾矿的添加量（因此降低酸度）对浸出动力学和最终浸出率（尤其是在 250°C 时）有不利影响，并导致金属硫酸盐沉淀。在使用无电极电导率传感器的实验中，实现了连续在线酸度测量。结果表明，酸在硅铁和二氧化硅的转化、以及基础金属的溶解过程中起主要作用，而过压氧（或分散效率）决定了酸的产生和再生成速率。
