Process Materials Inputs Pollution Outputs for Copper

Process

Copper concentration

Copper leaching Copper smelting

Copper conversion

Electrolytic copper refining

Secondary copper processing

Material Input

Copper ore, water, chemical reagents, thickeners Copper concentrate, sulfuric acid Copper concentrate, siliceous flux

Copper matte, scrap copper, siliceous flux

Blister copper

Air Emissions Process Wastes

Flotation wastewaters

Uncontrolled leachate

Sulfur dioxide, particulate matter containing arsenic, antimony, cadmium, lead, mercury, and zinc Sulfur dioxide, particulate matter containing arsenic, antimony, cadmium, lead, mercury, and zinc

Process wastewater

Particulates

Slag granulation waste

Other Wastes

Tailings containing waste minerals such as limestone, and quartz

Heap leach waste

Acid plant blowdown slurry/sludge, slag containing iron sulfides, silica

Acid plant blowdown slurry/sludge, slag containing iron sulfides, silica

Slimes containing impurities such as gold, silver, antimony, arsenic, bismuth, iron, lead, nickel, selenium, sulfur, and zinc

Slag

Source: From U.S. EPA, Profile of the Nonferrous Metals Industry, publication EPA/310-R-95-010, U.S. EPA, Washington, DC, September 1995.

Large amounts of water are used in the copper concentration process, although disposal of liquid wastes is rarely a problem because the vast majority of the water is recycled back into the process. Once the wastewater exits the flotation process it is sent to a sediment control pond where it is held long enough for most of the sediment to settle.

The seepage and leaking of sulfuric acid solutions used in leaching can also produce liquid wastes; however, this potential is offset by the copper producer's interest in collecting as much of the copper-bearing leachate as possible. Older operations generally do not have protective liners under the piles and experience some loss of leachate. New leaching operations use impermeable membranes to confine leach solutions and channel them to collection ponds.

Electrolytic refining does produce wastewaters that must be treated and discharged, reused, or disposed in some manner. Many facilities use a wastewater treatment operation to treat these wastes.

Primary copper processing primarily generates two solid-phase wastes: slag and blowdown slurry/sludge. Slag is generated during the smelting, converting, fire-refining, and electrolytic refining stages. Slag from smelting furnaces is higher in copper content than the original ores taken from the mines. These slags may therefore, be sent to a concentrator and the concentrate is returned to the smelter. This slag processing operation results in slag tailings. Slag resulting from converting and fire refining is also normally returned to the process to capture any remaining mineral values. Blowdown slurry/sludge that results from the sulfur recovery process is regulated by the RCRA as hazardous waste.

Secondary copper processing

Secondary copper processing produces the same types of wastes as primary pyrometallurgical copper processing. One type of secondary processing pollutant that differs from primary processing is the air emissions. Air pollutants are generated during the drying of chips and borings to remove excess oils and cuttings fluids and causes discharges of large amounts of dense smoke containing soot and unburned hydrocarbons. These emissions can be controlled by baghouses or direct-flame afterburners.

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