PSJ to Process 50% More Copper Without Using Extra Water

PSJ Cobre Mendocino is in the pre-construction phase of the project: reviewing studies, updating information about the deposit, and fine-tuning technical details before construction begins. During this review, the company presented a series of improvements to the Mendoza Government that have already been evaluated and approved.

The main innovation is a new system to treat "tailings"—the material left over after separating copper from rock—that allows more water recovery and leaves the residue much drier and more compact.

What are "tailings" and why does filtering them matter?

When ore is extracted, the rock is ground and mixed with water to separate the copper. What remains from that process—a mixture of water and ground rock—is called "tailings" or "tails". Traditionally, this residue is deposited in large dams as a kind of slurry.

The system PSJ is incorporating works differently: instead of leaving that residue wet, it passes through equipment that removes most of the water, converting it into something like a compact cake, almost dry (with just 15% moisture). That "cake" can be stacked dry, like bricks, instead of accumulating as liquid slurry.

Why is this an improvement?

• More water is recovered: the water removed from the residue is reused in the plant, rather than being lost.

• It's safer: a deposit of dry, compacted material is more stable than one with wet slurry, which reduces risks.

• Land recovery can begin sooner: by stacking the dry material in sections, vegetation can begin to be planted in completed areas without waiting for the entire mine to close.

This design was developed by Knight Piésold, an international consulting firm specialized in this type of mining deposits.

Fabián Gregorio, CEO of PSJ Cobre Mendocino.

More mineral per day, but without using more water

Thanks to this improvement, PSJ will be able to process up to 42,000 tons of ore per day, 50% more than the original 28,000 tons planned. And it will do so using the same amount of water already approved (141 liters per second) and over the same surface area already evaluated, without expanding the project area.

Where does that extra mineral come from?

Here a key technical concept appears: the "cutoff grade". In simple terms, it is the minimum concentration level of copper that a rock must have for it to be worth processing. If a rock has less copper than that minimum, it is not processed: it is discarded directly in a waste dump, as if it were "waste material".

With the information gathered from new drilling and with current international copper prices, the company recalculated that minimum.

How the process works, step by step

1. The rock is ground and copper is separated through a process called flotation.

2. What remains (the "tailings") first passes through a process that removes some water, leaving it with 60% solid material.

3. It then enters the new filtration system, which removes even more water, reaching 85% solids—a kind of almost-dry cake.

4. That cake is stacked dry, while the recovered water circulates back through the plant to continue being used.

What Mendoza gains from this

According to the company, with this increased processing capacity, annual production is projected to be approximately:

• 75,000 tons of copper

• 80,000 ounces of gold

• 900,000 ounces of silver

This means, according to PSJ, greater economic activity, more exports, and higher revenues for the province from royalties, taxes, and fiscal contributions.

The company also clarified that this additional investment in technology implies higher costs for PSJ—more equipment and infrastructure—but they present it as an improvement aimed at more efficient water use, greater safety for the tailings deposit, and a more robust design before construction begins.

With institutional information from PSJ Cobre Mendocino.