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Student Guide: Can Nanotechnology Help Clean Up Oil Spills in Oceans and Seas? Try It Yourself with Ferrofluid

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Summary

Have you ever wondered how science could make the enormous task of cleaning up oil spills in oceans and seas more efficient? Scientists claim that the combination of nanotechnology and magnetism can come to the rescue. In this science activity, you will test the proposed technique yourself, using various amounts of ferromagnetic fluid, mineral oil, and a strong magnet. Will you succeed in separating oil from water?

Useful Vocabulary

  • Nanometer: (abbreviated nm): One billionth (10-9 ) of a meter, or about 50,000 to 100,000 times smaller than the width of a human hair. To give you some other practical examples, a sheet of paper is about 100,000 nm thick, a virus is between 30–50 nm long, and fingernails grow about 1 nm every second.
  • Nanotechnology: The making, modification, use, and knowledge of tools at the scale of a couple of nanometers with the goal of creating new structures, materials, and devices.
  • Suspended: When objects do not sink or float in a fluid but "hang" so as to move freely, they are "suspended" in the fluid.
  • Ferromagnetic fluid: or ferrofluid: A liquid that is pulled toward a magnet, if one is present nearby. Ferrofluid is made of a carrier fluid in which magnetic particles the size of a few nanometers are suspended. Different types of oil or water are frequently used as carrier fluids.
  • Neodymium magnet : A type of powerful permanent magnet.
  • Control: In a scientific experiment, a control is a test sample that does not receive any special treatment, to be used as a basis of comparison for the test samples that do receive special treatment.

Materials

To do this activity you will need:

  • Petri dishes (3)
  • Colored water (50 mL)
  • Mineral oil (10 mL) in a cup
  • Plastic transfer pipettes (2). Ideally, one should be graduated, but it is not required.
  • Disposable gloves (1 pair per student)
  • Ferrofluid with mineral oil as a carrier fluid (6 drops)
  • Timer or clock
  • Plastic sandwich bags (3)
  • Neodymium magnet
  • Cloth or paper towels

Directions

In this science project, you will test a novel method to clean up oil spills in water using a ferrofluid and a strong magnet.

  1. Caution: Ferrofluids are messy. They stain skin as well as clothes and surfaces. At all times, be careful not to stain skin, clothes or other surfaces/objects around you.
  2. Safety: You will be using a neodymium magnet. These magnets are strong. At all times, keep these magnets away from any magnetized material and computers. Never swallow a magnet, do not let neodymium magnets slam together, and never stick fingers or other body parts between two neodymium magnets.
  3. Working with a partner, put three petri dishes in front of you in a row on a protected work area.
  4. Pour colored water in each petri dish until they are about half full.
  5. Use a clean graduated pipette to add exactly 2.5 mL of mineral oil to each of the petri dishes. This represents your oil spill. Aim to release the oil near the middle of the Petri dish. Note: If you are not using a graduated pipette, add exactly 50 drops of mineral to each of the petri dishes (this equals approximately 2.5 mL).
Petri dish with colored water and 2.5 mL of mineral oil
Figure 1. Petri dish with colored water and 2.5 mL of mineral oil. Although the mineral oil may be almost invisible in this picture, you should be able to see it in your petri dishes.
  1. Put on disposable gloves.
  2. After making sure the lid is on tight, shake the bottle of ferrofluid before opening it. Dip the plastic transfer pipette into the bottle and test how it feels to let one drop of ferrofluid out of the pipette back into the bottle.
  3. Now use the pipette to add one drop of ferrofluid to the middle of the oil spill in the petri dish in the middle. What happens to the ferrofluid when it hits the oil?
  4. For the petri dish on the left, add five drops of ferrofluid to the oil spill, preferably evenly distributed over the oil surface. Watch what happens when the ferrofluid hits the oil. If you accidentally put a drop of ferrofluid on the water surface instead of the oil spill, observe what happens. Does the ferrofluid float on the water? Does it sink?
Petri dish with colored water and 2.5 mL of oil to which five drops of ferrofluid have been added
Figure 2. Petri dish with colored water and 2.5 mL of oil to which five drops of ferrofluid have been added.
  1. Close the ferrofluid bottle and place the dirty pipette aside on a cloth or paper towel. Note: Add no ferrofluid to the petri dish on the right. You will use it as a control.
  2. Start a timer, or note the time on a clock, and observe each petri dish for about one minute. In the petri dishes with the ferrofluid, does it distribute itself over the oil spill? Does it go into the water? Do you see ferrofluid sinking to the bottom of the petri dish?
  3. Next, discuss with your partner what you think will happen when you go through or over the liquid in the petri dish with a strong magnet.
  4. Take a clean plastic sandwich bag and put the magnet in one of the corners of the plastic bag.
Neodymium bock magnet put in the corner of a sandwich bag, ready to pick up the magnetized oil spill in an oil clean up procedure
Figure 3. Neodymium magnet placed in the corner of a sandwich bag, ready to pick up the magnetized oil spill in an oil cleanup procedure.
  1. Pick one of the petri dishes and pass the magnet in the bag through the oil in one movement. Slightly submerge the magnet in the liquid and try to cover the complete oil spill in one movement as best you can. How much oil did you remove using the magnet? How does the water/oil/ferrofluid mixture look now? Note: It is important to choose one way of moving the magnet through the oil spill and keep this consistent throughout this activity so that you can best compare how efficient each amount of ferrofluid is at removing oil. Using different ways of moving the magnet through the fluid might influence the results.
  2. Wipe the bag off on a paper towel or cloth and put the magnet in the other corner of the plastic bag. This corner should still be clean and dry; if not, use a new bag.
  3. Repeat step 14 to remove any remaining oil/ferrofluid mixture from the water. How much more oil could you remove? How does the water/oil mixture look now?
  4. Carefully dispose of the dirty plastic bag in a trash can.
  5. Repeat steps 13 through 17 for the other two petri dishes.
  6. Compare the different petri dishes. In each petri dish, observe if the cleanup was efficient in removing oil— do you see lots, a little, or almost no oil left in the petri dish? How do the different petri dishes compare to each other? Overall, which one looks like the "cleanest" (or has the least oil)?
  7. Can you see any traces of ferrofluid left in the petri dishes after the cleanup?
  8. Do any of the cleanup procedures you tested seem like a good candidate for cleaning up oil spills in the ocean? Use your observations to explain why or why not.
  9. Clean up the area. No special disposal is needed for the ferrofluid or materials contaminated with it.