Following decades of challenges in the mining sector caused by colloidal silica in copper and cobalt leaching, BME Metallurgy has succeeded in developing and applying an innovative solution that promises potential in other commodity segments.
According to Daniel Verwey, Business Development Manager at BME Metallurgy, colloidal silica can cause serious operational issues in hydrometallurgical plants and particularly in solvent extraction.
“For many years, process plants have grappled with the impacts of silica, a highly prevalent gangue mineral that is leached into solution during acid leaching of valuable metals,” said Verwey. “Depending on its quantity, it can undermine the efficiency of the extraction process – even to the extent of shutting down the process.”
Partnering with Innospec – who provide a specialised coagulant called DEHSCOFIX® SC12 – BME Metallurgy assisted its customer MMG to apply this novel solution at its Kinsevere mine in the Democratic Republic of Congo.
“The product is designed to remove colloidal silica by promoting coagulation of particles,” he explained. “It binds to the particle surface and destabilises the colloid, so that the coagulated particles can be flocculated and removed from the solution.”
The removal of the colloidal silica in Kinsevere’s solvent extraction plant delivered many important benefits, including a reduction in total suspended solids, in crud formation and in entrainment. Importantly, there was increased pregnant leach solution throughputs – allowing improved copper production and cathode quality.
The Kinsevere project demanded considerable laboratory test work conducted with DEHSCOFIX® SC12, he said. This showed not only that it could remove a significant proportion of colloidal silica from the pregnant leach solution, but there was an improvement in phase disengagement time and an elimination of stable emulsion formation. Plant trials were then conducted, where these results were confirmed.
“In its full plant implementation of this coagulant, MMG Kinsevere used the DEHSCOFIX® SC12 coagulant to dose the leach discharge slurry,” he said. “The positive outcome was that the silica in pregnant leach solution was reduced from an average of 1,400 parts per million (ppm) to below 500ppm.”
This resulted in the solvent extraction plant immediately recovering its stability and resuming operations at full capacity – bringing production back to historical levels and improving the quality of its copper cathodes.
So successful was the result that MMG and BME Metallurgy presented the outcome of the project in a joint paper at the Southern African Institute of Mining and Metallurgy (SAIMM) Copper and Cobalt Africa conference in 2023 in Livingstone, Zambia. Verwey went on to present an update on the DEHSCOFIX® SC12 solution at the SAIMM Hydrometallurgy for the Future conference in 2024 in Cape Town.
“Our collaboration with Innospec and our customers has allowed us to replicate these results on a number of other copper mines in Africa,” said Verwey. “With the growth in demand for uranium, we have also been working on its application in uranium plants; our successful test work confirms that this solution will work for this commodity, where it has a promising future.”
He noted that these successes were part of BME Metallurgy’s decade-long journey to becoming a specialised provider of chemicals and solutions that delivers process efficiency and improvement.
