North Line Copper adopts heap leaching, solvent extraction, and electrowinning as a core business processes due to their efficiency, scalability, and cost-effectiveness in extracting high-purity metals from low-grade ores, enabling flexible, modular operations that deliver consistent value across diverse mining environments.

Heap Leaching

Heap leaching is a hydrometallurgical process used to extract valuable metals—such as copper—from low-grade ore by applying a leaching solution over stacked heaps of ore. The process is efficient, scalable, and ideal for large-tonnage operations.

Leach pads are engineered, continuously lined containment areas designed to hold one or more ore heaps (or "cells") with integrated drainage systems to collect leach solution. Crushed ore is stacked in layers, with heap heights varying depending on the project, each containing tonnes of ore. A dilute acid solution, typically sulfuric acid (H₂SO₄), is sprayed or dripped over the heap, where it percolates through the ore by gravity, dissolving target metals into solution. Air is injected through a pipe network above the base of the heap to introduce oxygen, which supports chemical and biological reactions. Increasing airflow enhances reaction rates and heap temperature. The ore reacts with the acid solution, dissolving the target metals into the liquid phase, resulting in a solution rich in dissolved metals known as Pregnant Leach Solution (PLS). 

Solvent Extraction

The purpose of Solvent Extraction (SX) is to extract valuable metals from an impure solution, often derived from processes like heap leaching. The process selectively separates the target metal from the solution, transferring it into a more concentrated and purified solution. This process ensures minimal contamination from other metals, allowing for efficient electrowinning of the target metal.

The solvent extraction (SX) process uses mixer-settlers to transfer target metal ions between aqueous and organic phases. A leach solution, containing dissolved metals, is mixed with an organic solvent—typically a combination of a diluent and a selective extractant—which binds specific metal ions. During extraction, the target ions transfer into the organic phase, while the remaining solution (raffinate) is removed. The loaded organic is then washed with recycled water and spent electrolyte to remove impurities. In the stripping stage, the metal ions are transferred back into an aqueous solution using a high-acidity electrolyte, producing a concentrated solution for downstream processing such as electrowinning. Separation occurs naturally within settlers through gravity, with fluid levels managed by adjustable weirs and no moving parts. 

Electrowinning 

Electrowinning is an electrochemical process used to recover metals from a metal-rich solution by applying an electrical current. 

The solution, known as electrolyte, flows into a cell containing two electrodes—a positive anode and a negative cathode. When current is applied, metal ions in the solution are attracted to the cathode, where they gain electrons and deposit as solid metal. This method is commonly used after leaching or solvent extraction and is beneficial for producing high-purity metals.