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 phytomining and bioleaching.

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

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

Some of the keywords we will be using in today's lesson include low-grade ore, phytomining, displacement, electrolysis, and bioleaching.

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

It would be a good idea to pause the video now and read through those sentences.

You might like to make some notes so that you can refer back to them later in the lesson if needed.

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

First of all, we are going to be looking at phytomining, then we are going to move on to look at bioleaching, and then we will finish today's lesson by comparing methods of extracting metals.

Let's get started Oo the first part of our lesson on phytomining.

Earth's resources are processed to provide energy and materials but these resources that we get from earth are finite and may eventually run out.

Here are some examples of finite resources that we use.

Limestone.

Limestone is used to make things like concrete and cement.

Crude oil is used to produce polymers and fuels.

And metal ores, we have an image there of a metal ore and metal ores can provide us with different metals, so we extract metals from metal ores.

It is becoming increasingly difficult to find some high-grade ores such as high-grade copper ores.

Low grade copper ores contain a lower percentage of copper.

Just a reminder that an ore is a rock that contains metal or metal compounds.

So a low-grade ore is one that contains a lower percentage of metal or metal compounds.

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

We can see that copper has been found in ores across the world.

Although there are some fluctuations on the graph, we can see the overall trend, that is the percentage of copper that we find in copper ores has been decreasing over the years.

Time for a check for understanding.

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, or c, has been decreasing.

The correct answer is c.

The percentage of copper that has been found in ores has been decreasing over the last 100 years.

That means it's more difficult to find high-grade copper ore.

Scientists fortunately have developed ways to extract some metals such as copper from low-grade ores.

It is becoming increasingly difficult to find high-grade ores because they have already been processed to extract the metal from them.

However, we can meet the demand at the moment for these metals by extracting the metals from low-grade ores.

Phytomining, also known as phytoextraction, is a process that can be used to extract copper from soil that contains low-grade copper ore.

Phytomining is a process that involves growing plants in soil that contains low-grade ores.

Phytomining uses plants such as Indian Pennywort and we can see that shown there in the image.

And the term phyto is a combining form that means plant.

Phytomining is mining that involves plants.

Phytomining involves the following steps.

We can see our plant here that is going to be used in the phytomining process.

We have the plant and the roots and this plant is being grown in soil that contains low-grade ore.

First of all, grow plants in soil that contains low-grade ores.

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

We then harvest the plants and burn them to produce ash, which is rich in these metal compounds.

We can see in the image there a picture of a harvested plant and that's being burnt to provide us with ash that's rich in those 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.

You can see there in the image we a picture of the ash and to that ash we have added acid and we are going to produce our leachate.

Phytomining can be used to extract different metals but if we just focus on copper, copper can be obtained from a leachate containing copper compounds.

So if we have grown our plants in soil that contained low-grade copper ores, our plants will absorb those copper compounds so when we harvest and burn the plants, the ash will contain a high concentration of copper compounds.

When we add the acid and form a leachate, our leachate will contain copper compounds.

We can then obtain the copper from that leachate by a displacement reaction with scrap iron.

A displacement reaction is a reaction where a more reactive element takes the place of a less reactive element in a compound.

Here we can see in the image we have scrap iron and we have our leachate containing our copper compound.

Iron is more reactive than copper, so the iron displaces the copper from the copper compounds.

For example, we have iron and copper sulphate and these will react together to produce iron sulphate and copper.

The iron is more reactive, so it has displaced the copper from that compound and we form iron sulphate and copper.

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

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

Rather than using a displacement reaction with scrap iron, we could use electrolysis.

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

We have our electrodes and they are placed in our leachate solution that in this example, would contain our copper compounds.

Electrolysis involves using electricity to separate the copper from the copper compound.

The copper would then collect at one of the electrodes and we would be able to obtain our copper from there.

How can copper be extracted from a leachate that contains copper compounds? A, combustion reaction.

B, displacement reaction.

C, photosynthesis.

D, electrolysis.

Choose any answers that you think are correct.

The correct answers are b, we could use a displacement reaction where we use scrap iron or d, we could use electrolysis.

Well done if you identified answers b and d as methods of extracting copper from a leachate containing copper compounds.

Time for our first practise task of today's lesson.

You need to order these statements to describe how phytomining can be used to extract copper from low-grade copper ores.

Pause the video now, read through those sentences carefully, and then decide on the correct order.

Come back when you're ready to go over the answers.

Let's have a look at the correct order that these statements should be in so that we can describe how phytomining can be used to extract copper from low-grade copper ores.

First of all, we are going to grow plants in soil that contains copper ores.

The plants absorb the copper compounds through their roots as they grow.

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

We then dissolve the ash in acid and this could be sulfuric acid and this will produce a leachate, and that leachate is going to have a high concentration of copper compounds.

We can then extract the copper from the leachate using either a displacement reaction with scrap iron because iron is more reactive than copper or we could use electrolysis.

Well done if you manage to arrange those statements in the correct order.

We have looked at phytomining as a method of extracting metals from low-grade ores.

We're now going to move on to have a look at how we can use bioleaching.

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

Bioleaching involves growing certain bacteria on a low-grade ore.

Here we can see an example of bacteria that are used in bioleaching.

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

If we grow those bacteria over a low-grade copper ore, then we will produce a leachate that contains copper compounds.

From that leachate, we can then try and extract the copper.

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

The copper can be extracted by, now, we could use a displacement reaction using scrap iron again.

The iron will displace the copper from the copper compound so we will then end up with an iron compound and our copper.

We could also use electrolysis.

Electrolysis involves using electricity to separate that copper from the copper compound.

Time for a question.

Which two methods are used by scientists to extract copper from low-grade copper ores? A, bioleaching.

B, mining.

C, quarrying.

Or d, phytomining.

Two methods that we could use to extract copper from low-grade copper ores.

The correct answers are bioleaching and phytomining.

So well done if you got that question correct.

Bioleaching is a method that involves growing bacteria over the low-grade ore and phytomining is a method that involves growing plants over a low-grade ore.

Time for another question to check we have remembered the difference between bioleaching and phytomining.

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

That statement is false.

Can you work out why that statement is false and 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, so bioleaching is a method used to extract metals from low-grade ores using bacteria.

It's phytomining that involves using plants.

Time for another practise task.

For this practise task, we need to describe how copper can be extracted from low-grade copper ores using bioleaching.

So think about the technique of bioleaching and how you can extract copper from those low-grade copper ores.

Make sure you give as much detail as you can in your answer.

Pause the video now and have a go at answering this question.

When you come back, we'll go over the answer.

How did you get on? Let's have a look.

To extract copper from low-grade copper ores using bioleaching, we would need to use bacteria in an area with low-grade copper ore.

The bacteria will break down the copper ore to produce an acidic leachate that contains those copper compounds.

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

Well done if you got that question correct.

Just make sure that you've got all the details that you needed and that you haven't missed anything important from your answer.

We have had a look at methods of extracting metals from low-grade ores.

First of all, we looked at phytomining, which involves growing plants in soil that contains low-grade ores, and then we looked at bioleaching, which involves growing bacteria over those low-grade ores.

Now we're going to finish by comparing 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 the impact that this has on the environment.

Let's consider some of the disadvantages then of this traditional method of mining.

Some of the disadvantages are the use of fuel for large machinery and when these machines use the fuel, they release atmospheric pollutants such as carbon dioxide, which is a greenhouse gas.

The environmental impact such as habitats being destroyed and looking at the image, you can see that it could be considered an eyesore as well.

Noise pollution for local residents with all the machinery that's used on the mining site and dust particles that are released can have a negative impact on human health.

Time for a question 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.

D, extracting metal from high-grade ores.

Choose any answers that you think are correct.

Some of the disadvantages of traditional mining are dust particles that can have a negative impact on health, noise pollution from all the large machinery that's used, and loss of habitats.

D, extracting metal from high-grade ores, that is an advantage of the traditional mining method that is used to extract metal from high-grade ores.

But remember those high-grade ores are also becoming more difficult to find.

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

We'll first of all focus on the advantages of phytomining.

It conserves high-grade ores.

Also because we do not need to use traditional mining, we have a reduction in noise pollution, dust particles, atmospheric pollutants, and loss of habitats that are all associated with traditional mining.

And another advantage of phytomining is that we can extract some metals from soil which only contains low-grade ore.

The disadvantages then of phytomining include that it's a very slow process.

It takes a long time for those plants to grow.

The plants may be impacted by weather conditions and pests and disease, which will all impact the growth of the plants and also phytomining can be more expensive than traditional mining.

Let's have a go at this question.

Which of the following is an advantage of phytomining? A, it conserves high-grade ores.

B, it's a quick process.

C, it's cheaper than traditional mining.

The correct answer is a, phytomining conserves high grade ores.

If we have a look at B, this is incorrect because phytomining is a slow process waiting for those plants to grow and phytomining is more expensive than traditional mining, so C is also incorrect.

Some of the advantages and disadvantages of bioleaching include, first of all, we'll have a look at the advantages.

It conserves high-grade ores just like phytomining.

We have a reduction in noise pollution, dust particles, atmospheric pollutants, and loss of habitats which are associated with traditional mining.

So we don't need to do as much traditional mining if we use the method of bioleaching.

And also bioleaching can be used to extract some metals from low-grade ores.

The disadvantages of bioleaching are that it's a slow process.

It can produce toxic substances such as sulfuric acid and we can see the hazard symbol there for a toxic substance, and 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.

Remember, you are looking for any disadvantages of using bioleaching to extract copper.

The correct answers are c, it's a slow process and d, produces toxic substances.

So well done if you identified those two disadvantages of bioleaching.

A was not correct because a says that copper can be extracted from low-grade ores.

This is an advantage of bioleaching.

And producing dust that is a disadvantage of traditional mining.

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

Once again, try to include as much detail in your answer as possible and see if you can remember as many advantages and disadvantages as possible of those two methods of extracting metals.

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

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

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

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

Your answer may not be exactly the same as that one there but hopefully you've included some advantages and disadvantages of phytomining and traditional mining in your answer.

You might like to pause the video now and add any key details that you missed from your answer.

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

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

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

In bioleaching, metal is extracted from bacteria that extract the metal from an ore.

And both of those methods produce a leachate and from this leachate we can extract the metal.

Electrolysis is a process used to separate metals from their compounds and we can use electrolysis or we can use displacement reactions to extract the metal from the leachate.

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

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

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