MATERIALS
RECOVERING THE RED METAL
W
orld usage of refined copper has more than tripled in the past 50 years, owing to the
expanding sectors of electrical and electronic products, building and construction, industrial machinery, and transportation. Interest in battery technology will inevitably add to demand. In addition, prices for copper
are rising. According to a report in the Financial Times newspaper at the end of 2017, copper prices reached $7312/t in 2017, the highest level since January 2014. This was attributed to strong global economic growth and robust demand in China, the world’s biggest consumer of copper. However, the International
Copper Study Group – an autonomous global inter- governmental organisation – in its latest report, The world copper fact book 2017, finds ‘increases in reserves have grown and there is more identified copper available to the world than at any other time in history’. The likelihood of running out of this crucial element, the report finds, is ‘improbable’. There is on average, 40 years of reserves, and significantly greater amounts of known resources according to US Geological Survey (USGS) data. In addition, recycling and mining exploration will continue to contribute to the long-term availability of copper. Nevertheless, with only around 29% of copper usage coming from recycled copper (USGS data, 2015), the world is reliant on copper produced from the
Increasing worldwide urbanisation and industrialisation are leading to a surge in demand for industrial metals, especially copper. Kathryn Roberts reports
processing of mineral ores. Chile is the largest copper
ore-producing country, generating around 5.7m t in 2017, followed by China (1.8m t), Peru (1.7m t) and the US (1.3m t). In Europe, Russia and Poland fall into the top 20 copper-producing countries though both produced less than 1m t in 2017. The rest of Europe, especially industrial manufacturing heavyweights: France and Germany, are heavily reliant on metal imports. Inevitably, there are potential
constraints on copper supply leading to volatility in the market. This includes, for example, escalating operational and energy costs, water supply in some of the dry regions where copper is mined. Added together, the demand and the constraints are motivating the French and German governments and businesses to look towards more secure, local resources of the red metal. And since most of the primary resources that contain what is considered a high amount (5–6% wt Cu) of the metal are exhausted in Europe, they have been turning their attention to the extraction of copper from moderate-grade
(2-3% wt Cu) ores and old waste deposits (ca0.5% wt Cu) related to past mining activities. Germany, like Poland, for
example, has significant copper ore deposits in the form of copper shale (Kupferschiefer), in the Mansfelder Land region This moderate-grade copper ore was mined for its metal content from the 12th century until 1990, and waste heaps remain in the area. In Poland, there are copper shale deposits in the Lausitz region, which are currently being explored by mining company KGHM Kupfer. And recently, significant reserves of copper shale have been discovered in Northern France and in the Massif Central region. Extraction of copper
from shale, however, is not straightforward. Traditional methods, like hydrometallurgy, which use aqueous solutions to extract the copper from copper oxide ores and pyrometallurgy, the application of heat, for use with copper sulphide ores, just don’t work for shale. Even the more environmentally-friendly bioleaching method, which is used to extract copper from chalcocite (Cu2
S) and covellite (CuS), cannot cope with the
shale. This is because copper shale is a complex ore: copper is present as the sulphide, but the ore also contains other metals such as zinc, lead and poisonous arsenic, present as different mineral compositions as well as significant amounts of organic matter. The resulting concentrate is highly alkaline and rich in organics. Acidophilic bacteria, such as Acidithiobacillus, used in classical bioleaching to yield copper sulphate in the process, cannot proliferate under the alkaline conditions. Against this background, in
2014, the EcoMetals Project was born. Funded to the tune of €4.2m by the German Federal Ministry of Education and Research (BMBF) and €1m from the French Agence Nationale de la Recherche (ANR), the project brought together scientists and engineers from 17 industrial, engineering and university partners from Germany, France and Poland to develop innovative bio hydrometallurgical processes for extracting copper and other metals from copper shale and metal waste heaps.
Thomas Deichmann, head
of public relations at German industrial biotechnology company BRAIN, one of the project’s industrial partners, comments: ‘Copper, among other metals, plays an important role in guaranteeing economic stability, which is an important driver for developing innovative extraction methods. There is an increasing need for eco-efficient access to metals from primary mineral resources and from waste heaps
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