- Carbon had been used for a few thousand years to extract metals from ore
- In the last 300 years, it has been discovered more metallic elements that are quite or very reactive
- Chemists realised these new, more reactive metals could not be extracted from their ores using carbon
- This was because the metals were more reactive than carbon
Electrolysis
- Extracting metals using carbon uses heat which is expensive
- Electrolysis uses electricity and heat which are expensive
- More reactive metals must be extracted via electrolysis therefore making them generally more expensive to extract
- The rarity of the metal will affect final cost
- Extracting metals using plants
When would you choose this?
- The ore is spread out over a large volume of land
- Lower concentrations of the metal
- Sometimes the percentage by mass of the metal you want from the ore is very low
- If these are true then costs of extraction would be too high using traditional methods, these are dubbed low-grade ores
If the ore is low grade...?
- As the manager of a company wanting to extract metal, you must consider:
- Machinery/equipment
- Workers
- Waste rock that will be left behind and needs to be disposed of
- You cannot afford to use lots of people and equipment as they are too expensive
- Might not get that money back after you sell your metal
- As it took too much time to extract it
How do you use plants?
- Plants grown on a large area of land - many square km
- Won't look ugly
- Plants will absorb metals from soil via their roots
- Takes a long time, usually several years
- After years, plants are harvested
- They are then placed in a large furnance and burnt
- Their ash is collected and the metal is extracted from it
What type of plants are used?
- Plants must be:
- Not lose their leaves easily
- Not allowed to grow too big
- High tolerance for harsh enviroments
- Able to live with lots of metals dissolved in their body
Benefits
- If the metal had contaminated an area, some companies will utilise this to remove the suspicious metals
- Land is decontaminated
- Great for enviorment
- Company makes money out of it - win win
- No noisy equipment - less noise pollution
- Less transport needed, lower pollution and lower carbon footprint
- Mines can be ugly but plants look more natural and blend in
What is achieved?
- The target ore may be spread out over a large geographical area
- Normal extraction costs too much
- Metal from the soil is concentrated into a pile of ash
- Extracting metal from this ash is easy
- Lots of money saved
- Company makes profit from extraction
- May be slow but useful for metal extraction