Production of cobalt from copper-cobalt ores on the African Copperbelt – An overview

Highlights

• Cobalt production is increasing, mainly from the Democratic Republic of Congo.

• Change in mine product from metal to relatively impure hydroxide.

• Extractive metallurgical techniques for cobalt product are reviewed.

Abstract

The development of renewable energy sources, electric vehicles and lithium-ion batteries has increased the demand for cobalt from the African Copperbelt that traverses the Democratic Republic of Congo (DRC) and Zambia. This increased demand has enabled the modernization of the process technology used across the region, resulting in the move from direct electrowinning of copper to solvent extraction-electrowinning. With this change has come a variety of technical challenges in the recovery of cobalt from these sources. The expansion markets for cobalt has resulted in a switch in the form of cobalt produced at the mine site, from metal cathode to cobalt hydroxide. In this paper, we provide an overview the processes currently used to produce cobalt from these copper-cobalt ores. The challenges for the technology in the context of the evolving markets for cobalt are highlighted.

Introduction

The African Copperbelt, or colloquially “the Copperbelt”, is the largest sediment-host copper province in the world. It is estimated that the Copperbelt contains 5 billion tonnes of ore containing 3.3% copper, yielding 185 million tonnes of copper. Industrial-scale mining on the Copperbelt has taken place for over a century. Cobalt is produced as a by-product of this copper mining. However, the increasing demand for energy storage and electric vehicles has increased the demand for cobalt (Azevedo et al., 2018), moving the status of cobalt from speciality metal to essential metal as the world’s energy sources change.

The global production of cobalt has increased over the period 2011–2018, as shown in Fig. 2. The data given in Fig. 3 indicates that the increase in global production has been sourced almost entirely from the DRC, which in 2018 produced about 60% of the world’s cobalt (see Fig. 3). This concentration of primary cobalt production in the DRC is mirrored by the concentration of refinery production in China, where about 60% of refinery production occurs (Azevedo et al., 2018, Shedd, 2019).

The price history of cobalt is shown in Fig. 4. Because cobalt is produced as a by-product of either nickel or copper production (Crundwell et al. 2011), the price of cobalt exhibits the volatility associated with by-product commodities. In 2018, the price spiked above 90,000 USD/t but has since dropped. Such spikes in price are not an uncommon experience, with price peaks in 1980, 1995, 2008 and 2018.

The dominance of the DRC in terms of total production and new production is clear from the data shown in Fig. 2, Fig. 3. This dominance is reflected in the biggest cobalt-producing mines and metallurgical operations, as shown in Table 1. All the current top producers are from the DRC. Some of these producers, like Mutanda Mining and Chambishi Metals, are temporarily closed, either for development or for business reasons.

The purpose of this paper is to provide an overview of the metallurgical methods used for separating cobalt and copper as currently practised on the African Copperbelt (see Fig. 1), the largest source of cobalt. Many of these mines have been in existence for decades. However, the processes used and the metallurgy employed have evolved with changes in the technology, market demand and societal pressures. Several other reviews have been published but they are not focused on the current industrial practice of the extractive metallurgy of cobalt. Instead, these reviews are focused on possible options for future development (Sole et al., 2019), on only the mineral processing (Shengo et al., 2019), or on design considerations (Miller, 2009, Fisher and Treadgold, 2009, Fisher, 2011). Other reviews, such as Rumbu, 2016, Prasad, 1989, Crundwell et al., 2011 are either too broad or require updating. In this work, the focus is on the techniques of extractive metallurgy that are currently used on the African Copperbelt to produce cobalt products.

There are two factors that have a bearing on the choice of products from the mine and hence the extractive metallurgy employed. The first influence is the requirements of manufacturers who use cobalt. In the next section, the supply chain to various cobalt products is discussed. The second influence is the mineralogy of the ore mined. This aspect is discussed after the supply chain. Following these preliminary topics, the production of cobalt from the region is discussed, after which an overview of metallurgical processes is given. Following this overview, each of the relevant process areas, or unit operations, is discussed in further detail.