Geosynthetics in Copper Mining

What role do geosynthetics play in copper mining?

Copper is one of the most sought-after metals and chemical elements. The automobile industry and others turn to copper for manufacturing processes. There have been significant strides in producing electric cars in recent years, and copper mining has taken center stage, with geosynthetics having a vital part of that conversation.

Copper is an excellent conductor of electricity and heat and a cheaper, more affordable alternative to silver—the preferred metal in the power generation industry. Electric cars use more than double the amount of copper in a gas-powered car (1). Statistical data also shows that purely electric vehicles contain 814 pounds of copper. Sedimentary and igneous rocks yield abundant copper ores, mined using various mining processes, with heap leaching being the most common process used in the United States (2).  

Geosynthetics—synthetic products that help stabilize terrains—play a considerable role when mining copper from its ore. This article explores the role of geosynthetics in copper mining and how these products support heap leaching.

Mining copper in the United States

The United States is one of the world’s largest producers of copper (3), with most of it mined in the western part of the country. Montana, New Mexico, Arizona, and Utah are among the more popular copper mining states. 

Copper mining begins with extracting copper ores (such as copper oxide and copper sulfide), which process into pure copper. The extracted pure copper, also known as cathodes, is converted into simple products for ease of use by industries (4). 

Copper mining occurs in open pits, and the mining process involves three stages, namely:

• Leaching
• Solvent Extraction
• Smelting.

Leaching: There are two types of leaching when mining copper: Heap leaching and In-situ leaching. However, heap leaching is the more common of the two and is best for low-grade copper ores. It is also the most preferred leaching process in the United States. In heap leaching, chemical solutions help pull out specific metals from ores. The ores are mined and crushed into a heap full of gravel-sized ores. That heap is mounted on an impenetrable layer located in an area with a slight slope (4). Dilute sulfuric acid is often used as the leaching agent and is applied using sprinklers. The leaching process collects the Pregnant Leach Solution (PLS).

Solvent Extraction: After the leaching process, the next step involves extracting the copper from the PLS. This process occurs in an extraction plant. An organic solvent combines with the PLS, binding to the copper and separating it from the rest of the solution. Next, the copper is placed into acid to precipitate the organic material from the copper. In the final stage, electrowinning collects copper into thin sheets. 

Smelting: After the copper sheets are collected, it is time for smelting, which takes three steps: roasting, mixing, and casting. Step one is roasting the copper concentrate to remove moisture and sulfur. Step two is mixing the concentrate with limestone and sand (silica) and heating the mixture in a furnace to form slag and matte copper. Step three is converting matte copper to slag, which undergoes further leaching. After leaching, the copper is sent back to the furnace for casting. 

 Geosynthetics in heap leaching and copper mining

Heap leaching facilities can pose severe problems to the environment due to the dangerous chemicals used during the process. From ponds to hold the barren and pregnant solutions to water detention basins and channels, liners are an essential component to keep harmful substances contained. Geosynthetics perfectly fit the profile of such materials.

Geosynthetics are polymers shaped into planar materials that support, reinforce, and improve soil conditions. These geosynthetics are available in large flat sheets before being welded (5).

Geosynthetic properties vary depending on the polymer, thickness, extrusion process, and other factors, such as additives. These factors determine the product’s durability, toughness, and resistance to UV degradation.

Geosynthetic product manufacturing involves using semi-crystalline polyethylene materials, making them resistant to mechanical loads and chemical solutions (6). Products can include geotextiles, geosynthetic clay liners (GCL), and pipes.

Geosynthetics offer many benefits over other materials to the heap leaching process. In addition to being a superior product for containment, geosynthetics are highly malleable and can come in all shapes and sizes to fulfill various design requirements. Engineers can design a containment system using liners that are bent, twisted, and molded to precise specifications to ensure the containment of chemicals used during the heap leaching process.

Additionally, engineers can leverage other geosynthetics to construct various parts needed in the heap leaching process. For example, in separation, geotextiles are excellent for drainage and isolating the waste from valuable materials (in this case, copper from the waste product). They make closure a less expensive endeavor and ensure the process is more efficient (7).

Heap leaching relies on chemicals to separate desired metals, like copper, from ore. For this reason, the containment system must have high resistance to chemicals and be durable and flexible. One resin that meets these criteria is polyethylene (PE). PE geomembrane liners are resistant to most chemicals used during heap leaching. These liners are also effective at dealing with point loads, typical in mining applications. Another option is geosynthetic clay liners (GCL). GCL incorporates bentonite, a geogrid, and geotextile to create a low-permeability layer that can be more cost-effective than a compacted clay liner (8).

While heap leaching is the most common type of mining used to extract copper in the United States, the practice poses a risk to the environment. Using geosynthetics solves this problem by providing a chemically resistant, durable, and flexible material for use in the process.

Geosynthetics by AGRU

ARGU offers a variety of geosynthetic solutions to meet the requirements of current heap leaching operations. AGRU supports projects with exceptional technical expertise, superior customer support, and an evolving inventory of innovative products to solve any challenge.

Three recent AGRU innovations include FrictionSpike, CleanSeam, and Conductive Liner.

FrictionSpike is a first-in-class, patented multi-tiered geomembrane solution that enables engineers to increase slope angles, maximize containment air space, and increase Factor of Safety. Owners can use FrictionSpike for landfills, mines, and regions with unique interface shear strength requirements to meet project stability conditions and unlock new capabilities and designs.

CleanSeam is a protective strip on high-density polyethylene (HDPE) liners that installers can peel away to dramatically reduce the time required to prepare the liner’s welding zones.

Conductive Liner is a coextruded geomembrane that contains a carbon layer that conducts an electrical charge, which is a requirement for Construction Quality Assurance Testing using ASTM D7240. These product innovations exemplify how AGRU has remained at the forefront of the geosynthetics industry. By choosing AGRU, you can access an expansive catalog of high-quality products. AGRU also offers customer service and technical feedback, including detailed drop-in specifications that your engineer can use in planning a design.