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Mining process of copper.

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Introduction

Figure 1 - The reaction which takes place when the ligand is dissolved in an organic solvent, then shaken with the leaching solution Figure 2 - Simple flow chart of a typical leaching operation Conventionally, copper was mined using the method of smelting. This way, the copper ore is mined, crushed, ground, concentrated, smelted and refined. In practice, only high-grade ores were considered as this created maximum profit. This process has it's draw-backs though. The ore has to be crushed extremely finely - to talcum powder thickness - before the process can start. Also, the ore must contain copper minerals in sulphide form (such as chalcolite or Covellite). The major draw- back was the huge amount of Sulphur Dioxide produced usually more than the copper itself. During the 1980's, a process revolutionised the way copper was mined. Commonly known as the leach- solvent extraction-electrowinning process (SX/EW), it allowed copper to be extracted from low- grade ores and mine wastes. The process was incedentally discovered when a blue-green solution was discovered near mine wastes. ...read more.

Middle

The gold leaches out in about 20-30 hours where it is screened from the slurry and pumped into an desorption tank where it is gold stripped. Typically a 20% ethanol solution is used at 80oC. The gold is now concentrated in the stripping solution and is pumped into electrowinning tanks. The gold then plates onto the steel wool within the tanks, when a golden fleece is created after hours. The golden fleece is the melted with the flux which removes the steel and impurities. The molten gold is the made into shiny bars and usually sold for further refining. Nothing is wasted: the carbon is heated with oxygen to reactivate it and restore it to the slurry tanks; the slurry eventually ends up in a tailing pond. Some lower grade ores may not go through this process, as it - like copper - is crushed and placed in heaps and slowly leached with cyanide solution. This process is cheaper but gives lower gold recovery. ...read more.

Conclusion

Leaching also requires extra safe-guards as there continually hazardous or corrosive chemicals. Bacterial leaching also is restrictive as leaching gold doesn't recover the base metals such as copper and visa versa. Bacterial Leaching is used a primary extraction method for gold due to the economic factors. As it only costs $30 per tonne of gold to produced, businesses can make a considerable profit extracting gold. For copper though, it is only secondary. This may be because it is "easier" to use previous methods. The new methods still require research and conversions of old plants. This requires considerable money, so businesses find it easier to continue as they are. Also, there are no tight environmental regulations on the amount of Sulphur Dioxide produced, so businesses are able to continue. For a new mining process to operate commercially it must pass through development stages. Firstly, there must be sufficient capital available to begin research. There must also be a quandary with the current process, which could be improved. It must be tested and proved to be more economically and environmentally viable than the original. ...read more.

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