Facilitator/Educator Guide: Can Nanotechnology Help Clean Up Oil Spills in Oceans and Seas? Try It Yourself with Ferrofluid
Scientists claim that a novel method combining nanotechnology and magnetism can help clean up oil spills in oceans and seas. Test the proposed technique yourself using ferromagnetic fluid, mineral oil, and a strong magnet. Will you succeed in separating oil from water?
Nanotechnology (i.e., the making, modification, usage, and knowledge of tools at the scale of a couple of nanometers, with the goal of creating new structures, materials, and devices) is a relatively recent addition to the world of technology. This video made by Cambridge University The Strange New World of Nanoscience is a good way to familiarize yourself with the "nanoworld," or the realm of distances 1 billionth (10-9 ) of a meter long.
Magnetic nanoparticles can be used to create a ferromagnetic fluid, or ferrofluid.
When there is no strong magnet nearby, the ferrofluid flows as we expect liquids to flow. However, when a strong magnet (or magnetic field ) is introduced, the ferrofluid is drawn to the magnet. Ferrofluid is composed of a carrier fluid in which ferromagnetic nanoparticles are suspended. Different types of oil or water are frequently used as carrier fluids. One potential application of ferrofluid is to clean up oil spills in the ocean. Figure 1 shows a flow chart explaining the idea.
|Figure 1. Flow chart visualizing the proposed procedure to separate oil (spills) from water using magnets by first making the oil "magnetic." This activity concentrates on the first three steps: making the oil magnetic using a ferrofluid and using magnets to separate the magnetized oil from the water.|
In this science activity, students will add ferrofluid to a mixture of water and oil to make the oil magnetic, and then use a strong magnet to remove the oil/ferrofluid mixture from the water.
This science activity can serve as a starting point for a variety of science discussions. Here are a few examples of questions that can be used to start a discussion:
- Why do the ferromagnetic particles in ferrofluid need to be so small? Would iron filings be cheaper and more readily available?
- What criteria could you use to evaluate if the method tested is a good candidate to be used to clean up oil spills in the ocean?
- In this science activity, we perform cleanup procedures by adding ferrofluid to the oil spill in petri dishes. In addition, we do the cleanup on a petri dish without adding any ferrofluid. Why would we do that? This is called a "control," but why would we need a "control"?
- This activity uses an oil-based ferrofluid, but would a water-based ferrofluid work to magnetize the oil in the oil spill as well?
Needed for preparing ahead:
- White poster board, butcher paper, or other material to protect each work area (1 per demo or small group)
- Graduated cylinder, 50 mL (1) available from Amazon.com, or a small cup with a pouring spout. ( Note: Adjust the size of the cylinder if larger petri dishes are used.)
- Tap water (enough to fill each petri dish about half full)
- Liquid food coloring (about one drop per demo or small group)
- Cup (1 per demo or small group)
- Mineral oil (10 mL per demo or small group); available at a pharmacy
Needed for each demo or small group at the time of the science activity:
You can purchase these items together in a ferrofluid kit available from Amazon.com or you can purchase them separately.
- Petri dishes (3). Note: One petri dish comes with the kit, but three petri dishes total are required for the activity. The 60 x 15 mm dishes available from Amazon.com work well
- Plastic transfer pipettes (2). Note: One plastic transfer pipette comes with the ferrofluid kit, but two are required for this activity. One is preferably a graduated pipette, but this is not required. Graduated pipettes of 3 mL capacity are available separately from Amazon.com
- Ferrofluid with mineral oil as the carrier fluid (6 drops). Note: The ferrofluid must have mineral oil as its carrier fluid for the activity to work well. The ferrofluid can be bought separately from Amazon.com
- Neodymium magnet (1). The kit comes with two magnets. Magnets are available separately from Amazon.com
- Disposable gloves (1 pair per student). Note: One pair of gloves comes with the kit, so you may need to purchase additional gloves.
You will also need to have these items ready:
- Water with food coloring (enough to fill the petri dishes half full)
- Cup with 10 mL mineral oil
- Timer or clock
- Plastic sandwich bags (3)
- Paper towels or cloth, to clean up spills
|Figure 2. You need only a few classroom science materials and ferrofluid to do this fun science activity.|
What to Do
Prepare Ahead (< 10 minutes)
- For each area where you will perform a demo or a small group will work, protect the work area, as spilled ferrofluid will stain surfaces. Working on a white poster board or butcher paper works well.
- For each demo or small group, fill a graduated cylinder (or cup with a pouring spout) with tap water, enough to fill all of the petri dishes half full. Color the water with 1 drop of food coloring. You will use colored water for this activity to make the transparent mineral oil more visible.
- For each demo or small group, pour about 10 mL of mineral oil in a cup.
- Note: We suggest that the single bottle with ferrofluid be shared between activity groups. This is a messy fluid that will evaporate when left open to the air, so it is not advised to pour the fluid in separate open containers.
|Figure 3. This picture displays the prepared items as they will be presented to the student.|
Science Activity (10-20 minutes)
- Each classroom demo or small group should have a protected work area, three clean petri dishes, two plastic transfer pipettes, a pair of disposable gloves (one for each student who will handle the materials), access to the bottle of ferrofluid, a neodymium magnet, three plastic sandwich bags, paper towels or cloth to clean up spills, water with food coloring, and a cup with 10 mL of mineral oil.
- Check the environment for safety and inform students about the dangers of working with ferrofluid and neodymium magnets:
- Ferrofluids can stain skin, surfaces, and clothes.
- Neodymium magnets are strong magnets, and they should be kept away from computers or other magnetized material at all times. Never swallow a magnet, do not let neodymium magnets slam together, and never stick fingers or other body parts between two neodymium magnets.
- Have students work in pairs and prepare the test by arranging three petri dishes in a row on the protected work area. They will fill the three petri dishes half full with the colored water and then add exactly 2.5 mL of mineral oil to each of the petri dishes. This added oil represents the "oil spill." Note: If students are not using graduated pipettes, they can count out and drop exactly 50 drops of mineral oil (which is equal to approximately 2.5 mL).
|Figure 4. Petri dish with colored water and 2.5 mL of mineral oil. Although the mineral oil is almost invisible in this picture, you should be able to see it in your petri dishes.|
- Instruct the students to make the oil magnetic by adding 1 drop of ferrofluid to the middle dish, and 5 drops to the dish on the left. The petri dish on the right is used as a control, so tell the students not to add any ferrofluid to it. Ask students to wait one minute and observe the results. They will see the ferrofluid spread over the oil spill. This happens because the ferrofluid's carrier fluid and the oil spill are a close fit (in this case, both are mineral oil).
|Figure 5. The petri dishes as students will see them after adding ferrofluid to two of them and waiting one minute for the ferrofluid to spread. Occasionally, the oil with ferrofluid accumulates at the border of the petri dish or forms several little islands on the surface of the water.|
- Direct the students to perform the cleanup procedure — i.e., telling them to go through the colored water/oil/ferrofluid mixture in the petri dishes two times with a strong magnet placed in the corner of a plastic sandwich bag. Have them wipe the bag between passes, then place the magnet in a clean corner of the bag, and finally pass the bag through the fluid a second time.
|Figure 6. The petri dishes with ferrofluid will appear similar to this after students do the cleanup procedure twice. The darker areas are tiny amounts of oil/ferrofluid mixture left over after the cleanup.|
- Instruct students to make observations with respect to efficiency and potential contamination (from leftover ferrofluid).
- Ask students to conclude if any of the cleanup methods tested is a good candidate for cleaning up oil spills in the ocean.
- Tell Students to clean up the area and dispose of droppers or pipettes, cloth or paper towels, and gloves contaminated with ferrofluid. Note that no special disposal methods are needed, as the ferrofluid can be poured safely down a sink drain and other contaminated materials can be disposed of safely in the trash.
The control will have some oil removed (because it sticks to the plastic bag) but most will still be floating on the water. In comparison, the cleanup method using one drop of ferrofluid is a lot more efficient, removing most of the oil during cleanup. The remaining oil and water mixture is fairly clear, with some oil and a little ferrofluid contamination. The cleanup method using five drops of ferrofluid is most efficient in removing the oil spill, but the small amount of remaining oil may be considerably contaminated with the ferrofluid (i.e., it will look dark) and, occasionally, a tiny amount of ferrofluid will sink to the bottom of the petri dish. Consequently, using this method may mean introducing a new contaminant to the environment when used on ocean spills.
In conclusion, using ferrofluid and a strong magnet is a good technique for cleaning up oil spills on the ocean. But larger scale tests and further studies on the effects of potential ferrofluid contamination are needed to determine the ideal amount of ferrofluid used.
For Further Exploration
This science activity can be expanded or modified in a number of ways. Here are a few options:
- In this science activity, the water in the petri dish was still. No waves or movement disturbed the oil spill. Investigate if moving the petri dish around, creating small waves, or stirring the liquid in the petri dish has an influence on the efficiency of the cleanup procedure.
- This science activity tested the cleanup of mineral oil on water using a mineral oil-based ferrofluid. An option is to compare how efficient the method works in cleaning up different types of oil (e.g. vegetable oil or sesame oil).
- This science activity uses a visual evaluation of the efficiency. Check out the science fair project idea "Can Nanotechnology Help Clean Up Oil Spills in Oceans and Seas? Try It Yourself with Ferrofluid" for a detailed description of how to make quantitative evaluations of the efficiency by measuring the volume of the oil left on the water surface after the cleanup procedure.