A sulfidic secondary raw material rich in Ni (millerite) and Zn (sphalerite) as well as mixed Ni-Fe-S sulfides was characterized and investigated for its leaching behavior under atmospheric direct acid leaching system utilizing air or oxygen, H2SO4, temperature ranges, and gas flow rates. The goal was to investigate extractability of the main elements (Ni, 15 wt% and Zn, 16 wt%) in the raw material whether both Ni and Zn could be extract simultaneously, or whether the material is more amenable to selective leaching, impacting the subsequent process options. Batch leaching experiments were performed in a 1 L and 0.5 L systems in two complementary leaching series. Ni was not appreciably extracted apart from the Ni sulfates present in the raw material apart from the experiments utilizing O2(g). The Ni dissolution did not readily occur until Zn extraction was finished and solution oxidation–reduction potential (ORP) increased to ca. 450 mV (vs. Ag/AgCl), and only reached ca. 50 % extraction at t = 24 h in T=90 °C and pH=1. The leach residue Zn content closely followed the ORP, achieving a minimum (0.1 wt% Zn) at E=471 mV (vs. Ag/AgCl). The most rapid leaching kinetics for ZnS was with excess acid, followed by experiments with O2(g). Decent kinetics were observed in response surface design of experiments (T=30, 50, 70 °C; m(H2SO4)/m(Raw material) = 0.6, 0.9, 1.2 g/g), allowing Zn extraction in < 6h. as it was possible to produce upgraded NiS (20 wt%) while extracting most of the Zn (99 %) under several experimental conditions, ranging from high T (90 °C) and limited constant acidity (pH 1) to low temperature (T=50 °C) and high excess acidity. It was shown that it is possible in an atmospheric process to selectively extract Zn while keeping majority of Ni in the leach residue. Selective extraction of Zn allows separation of Ni and Zn into separate materials feeds to be subsequently processed: Zn stream in a Zn process, and Ni-containing residue in a Ni smelter.

中文翻译：

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含 Zn 和 Ni 的次生硫化物的表征和浸出选项


对富含 Ni（硅铁矿）和 Zn（闪锌矿）以及混合 Ni-Fe-S 硫化物的硫化物二次原料在利用空气或氧气的常压直接酸浸系统、H2SO4、温度范围和气体流速下的浸出行为进行了表征和研究。目标是研究原材料中主要元素（Ni，15 wt% 和 Zn，16 wt%）的可萃取性，Ni 和 Zn 是否可以同时提取，或者材料是否更适合选择性浸出，从而影响后续工艺选择。在 1 L 和 0.5 L 系统中进行分批浸出实验，分为两个互补的浸出系列。除了利用 O2（g） 的实验外，除了原料中存在的硫酸镍外，镍没有被明显提取。直到 Zn 提取完成并且溶液氧化还原电位 （ORP） 增加到约 450 mV（相对于 Ag/AgCl），并且在 T=90 °C 和 pH=1 的情况下，在 t = 24 h 时仅达到约 50% 的提取率。浸出残渣 Zn 含量与 ORP 密切相关，在 E=471 mV 时达到最低 （0.1 wt% Zn）（与 Ag/AgCl 相比）。ZnS 最快速的浸出动力学是过量的酸，其次是 O 2 （g） 实验。在实验的响应面设计中观察到良好的动力学（T=30、50、70 °C;m（H2SO4）/m（原料）= 0.6、0.9、1.2 g/g），允许在 < 6 h 中萃取锌。因为在从高 T （90 °C） 和有限恒定酸度 （pH 1） 到低温 （T=50 °C） 和高过酸度的几种实验条件下，可以生产升级的 NiS （20 wt%），同时提取大部分 Zn （99 %）。 结果表明，在大气过程中可以选择性地提取 Zn，同时将大部分 Ni 保留在浸出残渣中。Zn 的选择性萃取允许将 Ni 和 Zn 分离成单独的材料进料，以便随后进行处理：Zn 工艺中的 Zn 流，以及 Ni 冶炼厂中的含 Ni 残余物。