C14 : 14.4 - Extracting metals from ores Flashcards
from what is most copper extracted from and what is the problem with this
- copper rich ores
- Problem : Earth’s resources of metal ores are limited => finite resource
when is extraction of metal ores from the ground classed as economically viable
when the ore contains sufficiently high proportions of the useful metal, such as iron ores and aluminium ores
what are low-grade ores
ores with lower quantities of metals
what kind of techniques are being dev. to extract metal from low-grade ores and why
- since , it would be uneconomical to extract using traditional methods of mining :
- sustainable techniques are being used to meet global demand
- because copper ores (and nickel ores) are becoming scarce
list 2 new ways of extracting copper from low-grade ores and what do they rely on
- Phytomining
- Bioleaching
- rely on biological processes
why are traditional methods of mining avoided for low grade ores
- involves digging, moving and disposing of large amounts of rock
- destruction of habitats
- pollutes surrounding area
- uses lots of energy is smelting
- profit loss for all of this input for a small amount of metal
what are the 2 meain methods to extract copper from copper-rich ores
- sulfuric acid used to produce copper sulfate soln. => extracted by electrolysis /displacement
- smelting (roasting) => copper ore heated to a high temp w/ air => produces impure copper
how can impure copper be used as the +ve electrode in electrolysis
- electrolyte is copper sulfate
- when current switched on, copper ions are dissolved at the anode, migrate towards the cathode and are deposited as pure copper.
- The impurities in the copper anode, often silver and gold, fall to the bottom of the electrolysis tank as a sludge, leaving the copper ions free to migrate.
- This is because the impurities are less reactive than copper and do not dissolve in the electrolyte solution.
- They are often collected and used for other purposes due to their value.
another word for - impure copper be used as the +ve electrode in electrolysis
electrowinning
why are the new biological ways of extracting metals favoured over traditional methods
- avoid traditional mining methods like digging, moving and disposing lots of rocks
- thus avoiding environmental damage
what is a con of the new biological methods of extracting metals
- very slow
- also require either displacement or electrolysis to purify the extracted metal
how does phytomining work
- plants that can absorb metal ions through roots are grown on soil containing low-grade copper ore
- plants absorb the metal ions through active transport
- the plants are then burned - the Cu in the plants react w/ O2 in air and from CuO
- the Cu2+ ions can be leached out of the ash containing CuO by reacting w/ sulfuric acid to form a leachate of copper sulfate solution
- Copper can be obtained by displacement from scrap iron or electrolysis
advantages of phytomining to extract copper
- Uses low-grade copper ore
- Requires less energy than smelting
- Produces less air pollution
- reduces amount of waste rock
- reduces need to obtain new ore by mining
- conserves limited supplies of metal-rich ores
disadvantages of phytomining to extract copper
- can produce toxic chemicals
- much slower process
- electrolysis requires large amounts of electricity
in phytomining, why is the ash (containing the CuO) reacted w/ sulfuric acid ?
- better than melting CuO for electrolysis - which req. more energy
- however, reacting with sulphuric acid turn it into a solution
