Lesson video

Hello, I am Mrs. Adcock and welcome to today's lesson.

Today's lesson is on alternative methods of extracting metals and we are going to be focusing on phytoextraction and bioleaching.

We are going to be thinking about how we can extract metals from low grade ores.

Today's lesson outcome is I can describe how metals are extracted by phytoextraction and bioleaching and compare different methods of metal extraction.

Some of the key words that we will be using in today's lesson include low grade ore, phytoextraction, displacement, electrolysis, and bioleaching.

Here you can see each of those keywords written in a sentence.

It'd be a great idea to pause the video now and read over those sentences.

You could even make some notes so that you could refer back to them later in the lesson if needed.

Today's lesson on alternative methods of extracting metals is split into three main parts.

First of all, we are going to look at phytoextraction, then we are going to look at the method of bioleaching, and finally, we are going to finish today's lesson by comparing methods of extracting metals.

Let's get started On the first part of our lesson, phytoextraction.

Earth's resources are processed to provide energy and materials.

These resources that we get from earth are finite and may eventually run out.

Here are some examples of finite resources, limestone, and we use limestone to make concrete and cement, crude oil, which is used to produce polymers and fuels, and metal ores, and we use metal ores to extract metals, which we use in many different ways.

It is becoming increasingly difficult to find high grade ores.

And remember, an ore is a rock that contains a metal or metal compound.

Low grade ores contain a lower percentage of the metal.

So if we take a copper ore, for example, a low grade copper ore will contain a lower percentage of copper or copper compounds in the rock.

Here we can see a graph that shows the percentage of copper found in ores over the years.

We can see that copper ores have been found worldwide, but if we look at the overall trend, we can see that the percentage of copper that has been found in these copper ores has been decreasing over the years.

Time for a question, over the last 100 years, the general trend is that the percentage of copper found in ores, A, has been increasing, B, has stayed the same, C, has been decreasing? The correct answer is C.

The general trend is that the percentage of copper found in ores has been decreasing.

This means it's more difficult to find high grade copper ores, so we need to develop ways that we can extract copper from low grade copper ores.

Scientists have developed ways to extract some metals, such as copper, from low grade ores, and this is really important with it becoming more difficult to find those high grade ores if we still want to be able to meet those demands for the metal, we need to extract the metal from low grade ores.

Phytoextraction, also known as phytomining, can be used to extract copper from soil that contains low grade copper ore.

And phytoextraction involves growing plants in soil that contains these low grade ores.

Here in the image we can see a plant that is used in phytoextraction.

Phytoextraction uses plants such as the Indian Pennywort shown in the image, and the term phyto is a combining form that means plant.

So the word phytoextraction means using plants to extract.

Phytoextraction involves the following steps.

It involves plants, and we can see an image there of a plant and the roots and the roots are in soil that contains the low grade ore.

First of all, we need to grow plants in soil that contains the low grade ores.

The metal compounds from the ore are absorbed through the roots.

Then we harvest the plants and burn them to produce ash, and this ash is then rich in the metal compounds.

We can see in the image there a plant that has been harvested and is being burnt to produce ash, which will be rich in metal compounds.

Next, we add acid such, as sulfuric acid, to the ash to produce a solution with a high concentration of dissolved metal compounds, and this solution is called a leachate.

If you look in the image, you can see we've got ash, and the ash contains those metal compounds, we add acid such, as sulfuric acid, to that ash, and we produce a leachate.

If our plants were grown in soil that contained low grade copper ore, then we can produce a leachate that contains copper compounds, and copper can be obtained from a leachate containing copper compounds by a displacement reaction with scrap iron.

Just a reminder that a displacement reaction is a reaction where a more reactive element will take the place of a less reactive element in a compound.

Here we can see our leachate that contains our copper compound and to the leachate we have added scrap iron.

Iron is more reactive than copper, so it displaces the copper from the copper compound and we can look at an example.

We've got iron and we have a copper compound there, which is copper sulphate.

We add the iron to the copper sulphate, and because the iron is more reactive, it displaces the copper from the copper compound and we end up with iron sulphate and copper.

At the bottom there you can see a balanced symbol equation for this displacement reaction where we were able to obtain copper from the leachate.

Copper can also be obtained from a leachate containing copper compounds using electrolysis.

Here we can see the apparatus that we use for electrolysis.

We can see the electrodes are placed in the leachate.

Electrolysis involves using electricity to separate the copper from the copper compound and the copper we will be able to collect from one of those electrodes.

We have seen that once we produce our leachate, we can either use a displacement reaction with scrap iron or electrolysis to obtain our copper.

Time for a question, how can copper be extracted from a leachate containing copper compounds? Can we use A, a combustion reaction, B, displacement reaction, C, photosynthesis, or D, electrolysis? The correct answers are B, displacement reaction, and D, electrolysis.

These are two ways that we can extract the copper from a leachate that contains copper compounds.

Well done if you identified both of those answers.

It's time for us to complete our first practise task of today's lesson.

And for this task, you need to order these statements to describe how phytoextraction can be used to extract copper from low grade copper ores.

Pause the video now, read through those sentences carefully and rearrange them into the correct order to describe how phytoextraction can be used to extract copper from low grade copper ores.

I'll see you in a moment when you're ready to go over the answers.

Let's see how you got on ordering these statements.

First of all, we need to grow plants in soil that contains that low grade copper ore.

The plants will absorb the copper compounds through their roots.

We will then harvest and burn the plants to produce ash that is rich in copper compounds.

Then we dissolve the ash in acid to produce a leachate.

We can then extract the copper from the leachate using either a displacement reaction with scrap iron or electrolysis.

Hopefully you were able to arrange those statements into the correct order.

Well done if you did.

You've clearly understood the work on phytoextraction.

We have had a look at how we can use phytoextraction to extract metals from low grade ores.

We're now going to have a look at the method of bioleaching.

An alternative method to extract some metals from low grade ores is bioleaching.

Bioleaching involves growing certain bacteria on a low grade ore.

We can see in the image there some bacteria that can be used in bioleaching.

The bacteria break down the metal ore to produce an acidic leachate that contains our metal compounds.

So we grow those bacteria over the low grade ore and they break it down to produce a leachate that contains the metal compound.

If we grow these bacteria over low grade copper ores, then we are going to produce a leachate that contains copper compounds.

If a leachate produced using bacteria contains copper compounds, the copper can be extracted.

The copper can be extracted by either a displacement reaction using scrap iron, and we saw this being used in phytoextraction, so we have our leachate that contains our copper compounds and we add scrap iron, and because the iron is more reactive, it will displace the copper from the copper compounds.

Or we can use electrolysis and we can see in the image there the apparatus used in electrolysis, and we have the electrodes that are present in the leachate, and this method uses electricity to separate the copper from the copper compounds.

Which two methods are used by scientists to extract copper from low grade copper ore? Can we use A, bioleaching, B, mining, C, quarrying, D, phytoextraction? We are looking for two methods used to extract copper from low grade copper ore.

The correct answers are bioleaching and phytoextraction.

So well done if you got that question correct.

We are going to have a question now to check that we can remember the difference between bioleaching and phytoextraction.

Is this statement true or false? Bioleaching is a method used to extract metals from low grade ores using plants.

That statement is false.

Why is that statement false? Can you justify your answer? Is it A, bioleaching is a method used to extract metals from low grade ores using plants and bacteria, or B, bioleaching is a method used to extract metals from low grade ores using bacteria? The correct answer is B.

Bioleaching is a method used to extract metals from low grade ores using bacteria.

It's phytoextraction which is the method that is used to extract metals using plants.

Bioleaching involves growing bacteria and phytoextraction involves growing plants.

Time for another practise task.

For this practise task, you need to describe how copper can be extracted from low grade copper ores using bioleaching, try to include as much detail as possible in your answer.

Pause the video now, have a go at answering this question and then when you come back we'll go over a model answer.

Let's have a look how you got on.

So we are looking to describe how copper can be extracted from low grade copper ores using bioleaching.

Your answer may include use bacteria in an area with low grade copper ore, the bacteria will break down the copper ore to produce an acidic leachate containing the copper compounds.

The copper can be extracted from the leachate by either a displacement reaction with scrap iron or electrolysis.

Well done if you managed to include lots of that key detail in your answer.

We have had a look at the extraction methods of phytoextraction and bioleaching.

We are now going to move on to the final part of our lesson and compare the methods of extracting metals.

The traditional method of extracting metal from high grade ores is mining, and this involves digging, moving, and disposing of large amounts of rock.

Here in the image we can see a copper mine and you can see the impact that this copper mine has on the environment.

Some of the disadvantages of mining include use of fuel for large machinery, and when the fuel is used in that large machinery, they can release atmospheric pollutants such as carbon dioxide, which is a greenhouse gas, environmental impacts, such as habitats being destroyed, noise pollution for local residents, and also those local residents can be impacted by dust particles that are released and these can have a negative impact on human health.

Let's have a go at this question based on what we've just learned.

Which of the following are disadvantages of traditional mining, A, dust particles can negatively impact health, B, noise pollution, C, loss of habitats, or D, extracting metal from high grade ores? Choose any answers that you think are correct.

The disadvantages of traditional mining include dust particles that are released into the atmosphere and can negatively impact health, noise pollution and loss of habitats.

D, extracting metal from high grade ores, is an advantage of traditional mining.

However, we have seen it is becoming more difficult to find these high grade ores.

Well done if you selected those three disadvantages of traditional mining.

Some of the advantages and disadvantages of phytoextraction include these listed here in the table.

Let's have a look at the advantages first of all.

The advantages of phytoextraction is that we can conserve those high grade ores, and because we will have less traditional mining taking place, there will be a reduction in noise pollution, dust particles, atmospheric pollutants, and loss of habitats, which are all associated with traditional mining.

Also, phytoextraction can be used to extract some metals from soil containing low grade ore.

Some of the disadvantages of phytoextraction are that it is a very slow process waiting for those plants to grow and the plants may be impacted by weather conditions, pests and disease, which can all impact that plant growth.

Phytoextraction is also more expensive than traditional mining.

Let's have a go at this question.

Which of the following is an advantage of phytoextraction, A, it conserves high grade ores, B, it's a quick process, C, it's cheaper than traditional mining? An advantage of phytoextraction is that it conserves high grade ores.

B is incorrect because phytoextraction is a slow process as we need the plants to grow.

C is also incorrect because phytoextraction is a more expensive process than traditional mining.

Some of the advantages and disadvantages of bioleaching include these listed here in the table.

Let's have a look at the advantages.

Bioleaching conserves high grade ores.

It also reduces the need for traditional mining.

So again, we have a reduction in noise pollution, dust particles, atmospheric pollutants, and the loss of habitats that are all associated with traditional mining.

Bioleaching also extracts some metals from low grade ores.

The disadvantages of bioleaching include it's a slow process and it also can produce toxic substances such as sulfuric acid, and we can see the hazard symbol there for a toxic substance.

These toxic substances can leach into the ground and cause environmental damage.

Which of the following statements are disadvantages of using bioleaching to extract copper, A, copper can be extracted from low grade ores, B, produces dust, C, slow process, D, produces toxic substances? The correct answers are that bioleaching is a slow process and produces toxic substances.

Well done if you got that question correct.

The answer is not A, copper can be extracted from low grade ores because that's an advantage of bioleaching, and B, produces dust, that is a disadvantage of traditional mining, not bioleaching.

Time for our final practise task of today's lesson, and for this task, we need to compare the advantages and disadvantages of phytoextraction and traditional mining.

Try to include as much detail as possible in your answer and as many advantages and disadvantages of both of those methods of extracting metals as you can.

Pause the video now, have a go at answering this question, and then I'll see you in a moment when you're ready to go over the answers.

Let's see how you got on.

Your answer may include an advantage of phytoextraction is that it can be used to extract metals from low grade ores, thereby conserving high grade ores.

Phytoextraction reduces the need for traditional mining and therefore reduces noise pollution, atmospheric dust and pollutants, and damage to habitats, which are all disadvantages of traditional mining.

However, phytoextraction is a slower and more expensive process than traditional mining and relies on good weather conditions for plants to grow.

Your answer may be different to this one here, but hopefully you still included lots of the same key points.

It would be a good idea to pause the video now and add any details that you missed to improve your answer.

We have reached the end of today's lesson on alternative methods of extracting metals, and we looked at phytoextraction and bioleaching.

Let's summarise some of the key points that we've covered in today's lesson.

In phytoextraction, metal is extracted from a crop of plants that absorb metal ions through their roots.

In bioleaching, metal is extracted from bacteria that extract metal from an ore, and both phytoextraction and bioleaching involve producing a leachate.

Electrolysis is a process used to separate metals from their compounds.

We can use displacement reactions or electrolysis to extract the metal from the metal compounds in the leachate.

There are advantages and disadvantages associated with each method of extracting metals.

Well done for all your hard work throughout today's lesson.

I've enjoyed the lesson, I hope you have too, and that you're able to join me for another lesson soon.