The depletion of the Merensky ore has led the South African platinum industry into largely mining and processing Upper Group Two (UG-2) ore for the extraction of Platinum Group Metals (PGMs). However, the processing of the UG-2 material is not fully amenable to the conventional pyrometallurgical route due to the high chrome content. Therefore, in this study, a bio-based process for base metal extraction from UG-2 flotation concentrates was investigated. This study represents only part of the work done in a broader investigation to develop a completely biological two-stage process for the extraction of base metals and PGEs. In this paper, only the first stage of the process is presented. This study evaluated a mixture of indigenous thermoacidophile archaebacteria namely, Acidianus brierleyi, Sulfolobus sp., and Metallosphaera sedula. A statistical Design of Experiments (DOE) was used for finding optimal conditions. Factors investigated included particle size, pH, pulp density, inoculum dosage, and temperature. Optimal extraction efficiencies of 92% for Co, 97% for Cu, and 99% for Ni were predicted at correlation coefficients of 92.5%, 93.2%, and 88.0%, respectively, thus, verifying the fitness of the model. Optimal base metal extractions obtained were 99.3% for Co, 90.1% for Cu, 41.58% for Fe, and 99.5% for Ni. The results showed a substantial extraction of base metals from UG-2 PGM flotation concentrate suggesting a potentially feasible option for industrial bioprocessing of PGM concentrates. To the best of the authors’ knowledge, this is the first report on bioleaching of base metals from UG-2 flotation concentrates.

Graphical Abstract

中文翻译：

---

利用实验设计优化 UG-2 PGM 浮选精矿的生物浸出预处理

Merensky 矿石的枯竭导致南非铂金行业主要开采和加工上族第二 (UG-2) 矿石，以提取铂族金属 (PGM)。然而，由于铬含量高，UG-2 材料的加工并不完全适合传统的火法冶金路线。因此，在本研究中，研究了从 UG-2 浮选精矿中提取贱金属的生物基工艺。这项研究仅代表了更广泛研究中所做工作的一部分，该研究旨在开发一种用于提取贱金属和铂族元素的完全生物两阶段工艺。本文仅介绍该过程的第一阶段。这项研究评估了本地嗜热嗜酸古细菌的混合物，即Acidianus brierleyi、Sulfolobus sp。和景天金属球菌。使用统计实验设计 (DOE) 来寻找最佳条件。研究的因素包括粒度、pH、纸浆密度、接种剂量和温度。在相关系数分别为 92.5%、93.2% 和 88.0% 时，预测 Co、Cu 和 Ni 的最佳提取效率分别为 92%、97% 和 99%，从而验证了模型的适用性。获得的最佳贱金属萃取率为 Co 99.3%、Cu 90.1%、Fe 41.58% 和 Ni 99.5%。结果表明，从 UG-2 PGM 浮选精矿中大量提取了贱金属，这表明 PGM 精矿的工业生物加工可能是可行的选择。据作者所知，这是第一份关于从 UG-2 浮选精矿中生物浸出贱金属的报告。

图形概要