For improved yields in solvent extraction, the selection of diluents used for copper, lithium and other minerals should be based on informed decisions.
Globally, there is an upsurge in the demand for critical metals and minerals to support the green energy transition and electrification. Thus, mine operators are exploring strategies to boost yields in their respective commodities.
Solvent Extraction
Solvent extraction is one of the tried and tested techniques for extracting metals from ores and other sources available to mine operators. In this process, diluents play a critical role.
Solvent extraction is preferred as it enables environmental responsibility, safety, and cost efficiency.
What Solvent Extraction Entails
Commonly, in solvent extraction, ore is leached with sulphuric acid. Then, a Pregnant Leach Solution (PLS) is produced. Then, PLS is mixed with the diluent in which an extractant is dissolved. The diluent causes the extractant to bind selectively to the targeted metal, for instance, lithium. Afterwards, the PLS dissolves the copper-extractant complex into the diluent and subsequently separates the organic layer from the water layer.
A variety of hydrocarbons are used to manufacture diluents. Some of the common ones include paraffin, cycloparaffin, and aromatic hydrocarbons.
However, in the marketplace where seemingly there is little differentiation in diluents, end-users must be thorough in product selection.
Solvent Selection
For this reason, miner operators should select diluents that meet their performance expectations concerning operator safety, environmental friendliness, and efficacy. Essentially, the following factors are essential in the selection of the most suitable solvent extraction fluid (the scope could be wider):
- Lower viscosity
The lower viscosity helps in achieving low-phase disengagement times and boosts selectivity.
- High flashpoint
Diluents with high flashpoints, when exposed to high temperatures, reduce the fire risk during solvent extraction. This enhances operator safety.
- Low rate of evaporation
The low rate of evaporation during solvent extraction reduces diluent consumption. Cumulatively, low solvent consumption can result in significant cost savings annually.
- Lower aromatic content
Lower aromatic content means a lower odour produced, which is ideal for operator safety.
- Low carcinogens and ecotoxins
Products that have reduced carcinogens and ecotoxins risk should be considered. This minimises mineworkers’ exposure to health hazards.
- Low carbon emission
To reduce Scope 3 Carbon emissions, the option of biodegradable diluents, which are becoming increasingly available on the market, can be considered. Typically, these are made from feedstock such as cooking oil, sunflower, or rapeseed oil.
Additionally, some manufacturers are producing diluents that they claim are “low-carbon” emissions.
Benefits of Informed Selection
Eventually, informed diluent selection ensures enormous benefits through significant cost savings, reduced health risks, improved operator safety, and environmental compliance, especially in an environment in which Environmental Social and Governance (ESG) are critical to employment safety.
Furthermore, claims some manufacturers make about the efficacy of their diluents should be thoroughly verified by seeking second, third opinions and fourth opinions. This is because the diluents are used for critical processes, so, there should be no margin for error. This is because more often than not, lapses can result in a reduction in yields, translating into huge financial losses on the balance sheet. This is not a situation mining companies would be keen to face as they aim to make the most of high commodity prices.
