Editorial Feature

Copper (Cu) Recycling

Copper has been used and valued by man for thousands of years. It was first used to make coins and ornaments in 8000 B.C. By 5500 B.C. copper tools were invented which aided civilization to emerge from the Stone Age. Copper was alloyed with tin to produce bronze in 3000 B.C., which heralded the beginning of the Bronze Age.

Copper is an element with Cu as its chemical symbol and 29 as its atomic number. It is also a highly sought after metal known for its excellent thermal and electrical conductivity. It has become an essential component in our daily lives. Copper is one of the few elements that can be found naturally in its pure form. It is 100% recyclable.

Copper continues to be a material of choice for numerous domestic, industrial, and high-technology applications today. Its excellent alloying properties have made it an invaluable metal, as it aids in the formation of not only bronze but also brass when combined with zinc. Copper can also be mixed with nickel.

Copper is available in many parts of the world with South America’s Andean region emerging as the world's most productive copper region.

Alloys of Copper

Copper alloys are metal alloys with copper being their chief component. Research shows that there are as many as 400 different copper and copper-alloy compositions. Copper-nickel alloy is known for its use in the making of hulls of ships as it helps prevent corroding in seawater, and in reducing the adhesion of marine life, thereby reducing drag and increasing fuel efficiency.

Brass has better acoustic properties than pure copper or zinc and hence is widely used in making a number of musical instruments such as trombones, bells, trumpets, and cymbals. Bronze is commonly used in ship propellers and submerged bearings as it has high corrosion resistance

Phosphor bronze, aluminum bronzes, silicon bronzes, copper nickel, nickel silvers, leaded copper, and beryllium copper also belong to the family of copper alloys. Copper salts are another form of copper with copper sulfate being the best known and most widely used of all copper salts.

Properties of Copper

Melting point - 1083°C (1981°F)

Boiling point - 2567°C (4653°F)

Density - 8.9 g/cm³

The key properties of copper are listed below:

  • Resistant to corrosion
  • Good conductor of electricity
  • High ductility and malleability
  • Can retain a high degree of ductility and toughness at subzero temperatures
  • High thermal conductivity, which allows for higher heat fluxes
  • Relatively unreactive metal
  • Tough and non-magnetic
  • Anti-bacterial, lightweight, easy to alloy, and catalytic
  • Naturally hygienic metal that slows down the growth of germs

Manufacturing Process of Copper

Mined copper ore is converted into a form ready for processing in a number of steps.

Initially sulfide and oxide ores are mined through digging or blasting methods. The extracted material is crushed to walnut-sized pieces. The pieces are ground in large, rotating, cylindrical machines until it becomes a powder. The sulfide ores are sent to a concentrating stage while oxide ores are moved to leaching tanks. In the concentrating stage, the minerals are made into slurry (with about 15% copper) and waste slag is removed. If the tailings contain any copper oxide it is sent to the leaching tanks. The concentrated copper is converted into pure copper cathode using leaching and electrowinning or smelting and electrolytic refining processes.

In electrowinning, the copper mixture is treated and transferred to an electrolytic process tank where the mixture is electrically charged causing pure copper ions to migrate to starter cathodes made from pure copper foil. In smelting, melting and purifying of the copper mixture is carried out, which results in matte, blister and 99% pure copper.

The oxide ores and tailings in the tank are leached by a weak acid solution so as to produce a weak copper sulfate solution.

Applications of Virgin Material Copper

Copper and its alloys are widely used in a number of fields and its applications keep increasing year by year. The key applications of copper are listed below:

  • Essential nutrient in our daily diet as copper works together with iron to form red blood cells. Also known to cure or reduce anemia, osteoarthritis, and osteoporosis.
  • Building construction, power generation and transmission
  • Electronic product manufacturing
  • Production of industrial machinery and transportation vehicles
  • Copper wiring and plumbing, heating and cooling systems
  • Telecommunications links used in homes and businesses
  • Essential component in motors, wiring, radiators, connectors, brakes, and bearings used in cars and trucks
  • Semiconductor manufacturers use copper for circuitry in silicon chips, which enables microprocessors to operate faster and use less energy.
  • Copper rotors increase the efficiency of electric motors
  • Kitchenware such as copper water storage vessels, copper kettles and copper cooking pans
  • Experimental plasma confinement devices
  • Thick copper strips are used as lightning conductors on tall buildings
  • Locks, scrapyard cranes, electric bells
  • Household appliances such as fridges, vacuum cleaners, washing machines, dishwashers, and entertainment systems
  • Vehicle components such as starter motors, windscreen wipers, electric windows, radiators, oil coolers, bronze sleeve bearings, fittings, fasteners, and screws
  • Computer components such as disc drives and fans
  • Transformer components such as mains adaptors, electricity substations, power stations
  • Application in food preparation, hospitals, coins, door knobs and plumbing systems as copper has antimicrobial property
  • In architectural design as it offers a variety of colors and finishes
  • For surface and submersible marine aquaculture enclosures that are used near or at off-shore sites so as to improve the sanitary conditions, productivity and sustainability of raising many fish and sea creatures
  • Antiseptics, anti-fungal products, and ornaments

Environmental Impacts of Copper

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Copper and its compounds are considered to be non-toxic unlike some other metals such as lead or mercury. There are no reports of any occupational diseases attributed to copper metal or copper salts.

During the mining and refining processes of copper, dust and waste gases (mainly sulfur dioxide) are produced which could have a harmful effect on the environment. These effects can be minimized by the copper producers themselves if they capture the sulfur dioxide and use it to make sulfuric acid.

Copper-based fungicides (especially those using copper sulfate) might cause a slight russeting or severe foliage burn when used during cool, damp weather. These fungicides can also cause severe phytotoxicity under certain conditions especially in grape varieties.

Copper tends to become toxic when biological needs are exceeded. Cupric ion is said to be the main form of toxic copper. Human activities relating to disposal of coal ash residue and municipal and industrial wastes on land cause excess of copper in the environment.

Recycling Process

All natural resources including copper are finite resources. To ensure that we do not deplete copper resources, copper commodities have to be recycled regularly to prevent wastage. Recycling will not be a difficult task as copper is 100% recyclable without any detrimental effect on its properties. Recent world data state that about 24 million t of copper is being used annually out of which 35% comes from recycled material. Recycling of copper will ensure that there will always be an abundance of this valuable metal/element for centuries.

Three simple ways to recycle copper are detailed below:

  • Copper products are hard wearing and long lasting and do not require replacement or improvement, thus making newer versions of copper products should be reduced.
  • Similarly copper products such as mobile phones, washing machines and cookers that are in good working condition can be sold as second hand products or given to other to reuse instead of dumping them as garbage.
  • Copper containing waste such as waste electrical and electronic equipment (WEEE), electrical cables, old taps, copper plumbing pipes and scrap from copper/copper alloy production and manufacturing should be gathered, dismantled and sorted. Then the parts should be sent for melting, casting and manufacture of new copper products.

It is cost-effective to recycle old copper than to mine and extract new copper.

Applications of Recycled Copper

Recycled copper helps to regulate the cost of virgin copper material from rising. Recycled copper has a number of applications quite similar to the virgin material, as of copper does not lose its essential properties when recycled. Some examples of recycled copper applications are mentioned below:

  • Scrap copper with tin and lead presence are valuable as they are used to make gun metals and bronzes
  • Computer chips and turnings from screw machine processing compose a large portion of recycled copper sources
  • Copper tube manufacturers use on average more than 50% recycled materials in their tubes.

Sources and Further Reading

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