It occurs as a soft reddish metal that can be found native as large boulders weighing several hundred tons or as sulphide ores. The latter are complex copper, iron and sulphur mixtures in combination with other metals such as arsenic, zinc and silver. The copper concentration in such ores is typically between 0.5-2%.
The most common ore is chalcopyrite, CuFeS2, a brass yellow ore that accounts for approximately 50% of the world's copper deposits. Numerous other copper ores of varying colours and compositions exist. Examples are malachite, Cu2CO3(OH)2, a bright green ore, and the red ore cuprite, Cu2O.
Hydrometallurgical Method -SX/EW
Solvent Extraction / Electrowinning is the most dominant leaching process used today in the recovery of copper from chemical solutions. As the name suggests the method involves two major stages:
Solvent Extraction- the process by which copper ions are leached or otherwise extracted from the raw ore using chemical agents.
Electrowinning- electrolysis of a metal ion containing solution such that Cu ions within it are plated onto the cathode and thereafter removed in elemental form.
Solvent Extraction at MYTCL involves the selective extraction of the valuable copper from the Pregnant Liquor Solution (PLS) into an immiscible organic phase, which consists of a complex organic extractant dissolved in high-flash point kerosene (a lixivant or leaching solution). These two types of solution are stirred and allowed to naturally separate along a settler due to their different specific gravities. From this stage the copper is stripped from the loaded organic phase by highly acidic electrolytes to produce an enriched electrolyte known as strong electrolyte. The remaining low-copper aqueous solution from the extraction stage, called raffinate, now high in acid (H2SO4) content is recycled to the leach cells to recover more copper while the strong electrolyte is sent to the tank house for electrowinning.
Copper can truly be cited as the ‘green’ metal both for its role in protecting the natural environment through its use in energy-saving applications, and for the achievements that have been realised in the production of the metal in an environmentally sound manner. Copper Ore is stacked by conveyor systems or by dumptrucks onto the heap cells and then prepared for irrigation. The complex systems of drains and heaps are environmentally designed to meet international standards with integrated safeguards preventing ground contamination.
The cathodes are stripped basically every seven days, with each copper-laden cathode weighing approximately between 48-52kg as per the London Metal Exchange (LME) market standard. These sheets are washed with hot water, sampled, weighed and bundled for shipment. Sampling is being carried out on an 80tonne/lot basis, and analysis is completed at offshore and local laboratories for LME quality control. MYTCL produces cathode copper that complies with LME Grade-A rating, and is more than 99.999% in purity.
Solution management to and from heap cells is strictly controlled on a daily basis. The foundations of the heaps are constantly monitored and checked for leaks, and measures are in place to pump out any stray solutions from beneath the HDPE before they have any opportunity to breach the protective clay base barriers. This design methodology not only protects the environment from potential impacts, but it also protects MYTCL’s liquid assets of the solution bearing precious copper.
Social & Environmental Stewardship through Production
Natural resource development without question affects communities and the environment. The overall benefits of MYTCL's mining activities take into account the economic well-being of the communities at large, and that quality of life improvements and guidelines are established and embellish positive impacts. In addition, host communities surrounding the S&K Project enjoy strong employment coupled with family-wage jobs, economic activity from the purchase of goods and services and fees and taxes paid to local, regional and federal governments. The S&K mining’s environmental footprint continues to be reduced as a result of improved technology and better scientific information; two generations of specially trained environmental, wildlife and reclamation professionals; a comprehensive framework of national and federal laws and regulations that commences with the initial mine plan and carries through to completed reclamation of the mine site; public participation in the regulatory process; and voluntary efforts and innovative actions by the MYTCL mining organisation led by Wanbao Mining Ltd in Beijing.
Elimination of Legacy Impacts
There is an additional focus of MYTCL that extends beyond the terms of contractural obligations as the Operator of the S&K Mines. MYTCL voluntarily undertakes projects aimed at addressing environmental impacts from historic or pre-law mining activities. These projects, accomplished independently, as well as in conjunction with governmental entities and local community groups, result in net environmental benefits including, elimination of high walls, reclamation of environmental contamination due to artisinal industry and village interference, management of land issues not resolved over time, improved water quality and fish and wildlife habitat restoration.