Keeping cobalt competitive: midstream processing in Australia

In the fourth instalment of the Australian Mining Review’s critical minerals series, we speak with Australia’s national science agency, CSIRO Futures manager Beni Delaval and CSIRO chief research scientist Chris Vernon for a deep dive into emerging mid-stream processing pathways for cobalt as highlighted in the agency’s From Minerals to Materials: An Assessment of Australia’s Critical Minerals Mid-Stream Processing Capabilities report.

According to the IEA, cobalt demand is expected to increase from 171.6kt in 2022, to 524.7kt in 2050, driven by emerging clean energy technologies, specifically the use of cobalt in lithium-ion batteries.

Australia has the opportunity to capitalise on this swell in demand, while enabling global divestment from the cobalt dominating the global supply chain, which is indivisible from significant human rights concerns.

Current mine production is highly concentrated in the Democratic Republic of Congo (DRC), which represented 73% of global mine production in 2022. Alongside Indonesia, representing 5% of global mine production, the country accounted for approximately 90% of the growth in cobalt supply between 2021 and 2022.

Dr Vernon says diversifying midstream processing in places with strict and reasonable adherence to government regulations, like in Australia, would be a massive boost for cobalt.

“A lot of the world’s cobalt is dug up we don’t quite know where, and we don’t quite know by who  but we know the DRC features,” he said.

“Some of that material makes its way into other jurisdictions where it gets processed and turned into cobalt chemicals its provenance gets lost.

“This is a real problem in that supply chain as we’re not quite sure how green it is, how socially acceptable it is, how environmentally acceptable it is.

“If you can shift the processing into more mainstream jurisdictions, you get a better oversight of where it’s coming from and how it’s being processed.”

With the second largest cobalt reserves in the world, Australia has a pivotal role to play in diversification, but with the current low-price environment of cobalt, the opportunity for Australia is unclear.

Ms Delaval says this low-price environment is being driven by growth of production in China and Indonesia, made possible by factors such as economies of scale, supply chain integration with domestic or foreign mines and policy support from government.

“A lot has happened in the market since we released this report, obviously nickel prices have taken a bit of a dive, and cobalt is usually associated with nickel, with strong production in China and Indonesia driving that price drop,” she said.

Ms Delaval says even though Australia is very well endowed with deposits which contain cobalt and nickel, it is quite expensive to extract and produce cobalt metal or cobalt sulphate.

“Compared to some of these other countries, we have fairly high labour costs, fairly high energy prices and very strong environmental and emissions standards, which can also increase costs,” she said.

“The sustainable products that are coming out of Australia are more expensive than some of the products produced elsewhere, which makes it really difficult for Australian producers to actually compete.

“[This may be] why a few of them have decided to stop supplying temporarily, because it’s just not profitable at the moment with such low prices.”

Robust investment into RD&D alongside innovative policy and investment solutions may be the missing link for making Australian cobalt competitive.

Extraction of cobalt compounds from ores

In Australia, cobalt is found within two economically relevant deposit types: sulphide deposits and laterite deposits.

Sulphide ore deposits are the most traditionally extracted due to their higher grade, while laterite ore deposits are lower in grade but more abundant.

Extraction of cobalt is tricky, given sulphide deposits are depleting and ore grades are declining globally.

“We found the best ores and we’re running out, simple as that,” Dr Vernon said.

“If you look at almost every ore type in the world, you’ll see that in the last 150 years, the grade has been declining, and that’s purely because the really good ones were easy to find.

“Now, we’re looking for the scraps, so grade is going down.”

For Australia to compete in cobalt, it will have to make the most of its remaining, untapped resources.

Thermal pretreatment: roasting and smelting

Cobalt is preferably first separated by beneficiation from other minerals and then chemically extracted to produce a cobalt rich solution used in further processing.

For sulphides, traditionally, a thermal pre-treatment of the ore involving roasting, smelting or a combination of both, is the first step in the separation process.

Roasting involves direct roasting or roasting with an additive such as sulphur dioxide, sulphates, chlorides, or chlorine gas, as a preliminary step to smelting, to assist in reduction or as a precursor to leaching.

Smelting is conducted with an electric or flash furnace to produce a nickel-cobalt sulphide matte that can be separated from major impurities, such as iron.

While roasting is highly mature and deployed at scale in Australia, efficiency can still be significantly improved. According to CSIRO, roasting and smelting will likely continue to be relevant in Australia given existing domestic sulphide deposits, however its use is limited when considering laterites.

RD&D FOCUS:

Roasting

• Optimisation of roasting parameters in reductions, including reductants used, additives, time and temperatures
• Optimisation of the composition of additives to improve downstream leaching efficiency

Smelting

• Development of strategies to recover cobalt lost to slags

Leaching is the next step for separation.

This process involves dissolution of the metal ore to form a solution ideal for retrieving one metal of interest, in this case, cobalt.

The major pathway for processing laterite ores involves sulphuric acid leaching.

Sulphuric acid leaching can be employed through pressure oxidation processes, high-pressure acid leaching (HPAL) or leaching at atmospheric pressure, depending on the ore type, grade and overall project economics.

Laterite ore deposits, which represent the majority of Australian cobalt reserves, are conventionally treated using sulphuric acid at high temperature and pressure and to a lesser extent using atmospheric pressure processes.

For example, HPAL is a high-pressure process used internationally at some of the largest plants for laterite ore processing and in Australia at Glencore’s Murrin Murrin and First Quantum Minerals’ Ravensthorpe operations in WA.

HPAL offers several advantages for processing laterite ores, including high extraction, shorter processing times and minimisation of iron. There is major room for improvement of HPAL surrounding the generation of large tailings volumes, high operational costs and energy intensity.

Leaching at atmospheric pressure is also used in extraction from laterite ores, but its use in industry is less prevalent than HPAL.

Acid leaching at atmospheric pressure includes in tanks at high temperature, heap leaching and mixed processes that incorporate an atmospheric and high pressure step.

Leaching at atmospheric pressure can be applied to low grade cobalt ores and tailings. These processes are of interest, as they are less cost and energy intensive than HPAL but entail lower nickel and cobalt extractions and longer processing times.

Sulphide ores, which become more difficult to either smelt or leach economically as grades decline, can be processed through pressure oxidation processes.

Pressure oxidation processes involve the addition of oxygen to a slurry under high temperature and pressure. The sulphur already present in the ore generates sulphuric acid under this temperature and pressure, which facilitates leaching.

The process can be applied to low grade sulphide ores that aren’t suitable for smelting and the excess sulphuric acid can be used to process other acid consuming ores, like laterites. However, without connected uses to consume it, the sulphuric acid can become a waste handling issue that introduces additional costs.

In addition to sulphuric acid leaching, ammonia leaching, bioleaching, alternative acid leaching and chloride leaching technologies are also being explored.

RD&D FOCUS:

HPAL

• Minimising waste generation and improving residue management; recycling acid used and implementing safe tailings storage

Atmospheric pressure leaching

• Using reducing agents and salt additives to increase recovery
• Optimising removal of metallic impurities

Pressure oxidation processes

• Progressions of cost-effective and scalable strategies to neutralise or make use of the excess sulphuric acid.

Production of refined cobalt products

Following separation, refined cobalt products can be produced. These include a mixed intermediate, battery grade cobalt compounds and cobalt metal.

Battery grade cobalt sulphate is a material of interest, as it is an input into the production of precursor cathode active material (pCAM) for lithium-ion batteries.

Purification and separation technologies including precipitation, solvent extraction and ion exchange, are used to separate cobalt from the initial leach solution. These methods remove metallic impurities and separate cobalt from other metals present, resulting in a highly pure solution.

In precipitation, metallic impurities are selectively precipitated out of the leach solution by adding a reagent and modifying the pH of the solution.

There are limitations for precipitation when it comes to selectivity of cobalt recovery in the process, as metals such as iron and nickel behave similarly to cobalt and will also be precipitated. Because of this, the process is commonly used to produce mixed precipitates (MHP and MSP) that require further refinement.

Additional refinement often involves solvent extraction, which can selectively extract cobalt out of a solution, despite the presence of other metals. The most common reagents used in the process are based on organophosphorus acids.

Ion exchange separation can be employed as an alternative to or alongside solvent extraction. Ion exchange separation utilises beads made from synthetic resins that selectively interact with metals present in the leach solution under specific pH conditions, allowing for separation as the captured metals are released using an appropriate reagent such as sulphuric acid.

Ion exchange can be used to produce highly pure cobalt solutions for use in electrowinning or crystallisation or to support cobalt recovery from waste streams, maximising extraction from low grade or complex ores.

RD&D FOCUS:

Precipitation

• Enhancing precipitation selectivity
• Opportunities to bypass downstream separation and purification steps by directly producing combined materials usable in pCAM production

Solvent extraction

• Developing cost-effective strategies to separate nickel and cobalt from complex leach solutions
• Developing alternative solvents
• Optimising selective recovery of cobalt

Ion exchange

• Enhancing dubitability and reuse for resins
• Integrating the resins in direct recovery of cobalt from leach solutions and waste streams

Cobalt sulphate

Once purified and separated, the recovered cobalt sulphate undergoes a process of crystallisation and final drying to produce a highly pure compound. The crystallisation process uses controlled temperatures or solvent compositions to induce formation of a crystal. Crystallisation is a key technology underpinning the final step to produce cobalt sulphate, a high-grade saleable solid and direct input into pCAM.

Approaches to crystallisation include thermal approaches, chemical approaches, and membrane crystallisation. Although the process is simple, crystallisation parameters can affect the suitability of the product for pCAM production.

RD&D FOCUS:

Crystallisation

• Increasing energy efficiency for evaporative and cooling crystallisation
• Optimisation of reagents like solvents and additives and process parameters like mixing to improve control over crystal characteristics and facilitate the recovery and recycling of reagents

Cobalt metal

Cobalt metal is a versatile product already produced in Australia that can be sold into multiple end markets. Hydrogen reduction and electrowinning are primary methods to produce this metal, and both have strong potential for renewable energy integration.

Hydrogen reduction involves introduction of a hydrogen gas to a cobalt-containing solution to produce metallic cobalt powder. This entails the addition of ammonia to the solution for pH control and removal of sulphate. Challenges to this method include the economic and environmental considerations that come with sourcing hydrogen gas. It is also inherently challenging as hydrogen has lower reductive capacity when compared to carbon.

In electrowinning, an electric current is passed between two electrodes to reduce cobalt ions present in a solution and deposit them in metallic form over a cathode. This pathway presents advantages as it is compatible with both sulphide and chloride solutions, but the process is limited by the side-production of hydrogen and co-deposition alongside nickel and copper, requiring their removal from the initial solution.

RD&D FOCUS:

Electrowinning

• Increased selectivity for cobalt over elements like nickel and copper

Hydrogen reduction

• Optimised reactor designs for operational efficiency
• Assess the viability of using hydrogen plasma as an alternative reducing

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