Several Zambian copper producers have noted an increase in oxide copper content in the deposits that they are mining, making it difficult for mining companies to extract and process the ores efficiently, says reagents expert Axis House technical manager Bernard Oostendorp.

As one of the largest copper-producing regions globally, Zambia is in a perfect position to benefit from the growing demand for copper to support the global energy transition.

However, mining operations will need to adapt their processing methods to ensure they meet the required concentrate quality.

While many operations traditionally mined and processed pure sulphide copper, they are now mining ores that contain up to 15% oxide copper, leading to a reduction in overall recovery when using traditional collectors.

Oostendorp explains that the changes in feed grades are also resulting in an increase in carbonaceous minerals being mined. This negatively affects the flotation process and limits the upgrading of ores with the standard reagent products.

Mining operations have to deal with the difficulty of having to mine deeper for resources, resulting in varying mineral content and declining grades.

This negatively impacts processing plants, which are designed to operate with a specific range of head grade to produce quality concentrate and, therefore, they are not achieving the required concentrate quality, he elaborates.

Consequently, some plants are moving from processing pure sulphide to mixed ore; however, this requires a change in the flotation circuits, which can be costly.

Oostendorp explains that while various physical parameters, such as airflows, levels and mass pulls can be varied, the resulting processed ore does not meet the required quality. Therefore, using selective reagents can achieve the required result while overcoming the need to invest more in plant upgrades.

“Optimising the reagent suites in the flotation process is vital to mitigating and improving processes,” he says.

Axis House offers specialised depressants and collectors, which are formulated to address these problems. Oxide and transitional copper ores can be processed with Axis House’s range of specialised collectors, such as AM810 and UniQ305.

With more than 20 years of experience in supplying reagents to Zambia, Axis House has worked on clients’ individual ores at its in-house metallurgical laboratory, in Cape Town, South Africa, and further developed a range of collectors, depressants and frothers to meet problems identified at each mine site.

Axis House also has an established office in Zambia.

Currently, the company is developing more selective sulphide and oxide collectors to treat the low-grade ore and to be more selective against gangue minerals like pyrite.

In terms of sulphide copper processing, Axis House has also focused on projects relating to selective collectors and pyrite depression, with a new pyrite depressant Revadep-P28 being tested on ores from multiple operations.

The company will continue to work alongside Zambian mines to ensure that specifically selective reagents are applied to avert plant upgrades.