Removing Microplastics from Water with Ferrofluids
Abstract
Have you ever walked next to your favorite ocean, lake, or creek and seen plastic waste everywhere? Have you ever thought about how much plastic breaks down into microplastics and pollutes waterways? Scientists are coming up with new ways to remove these microplastics from our waterways, and now you can test them out for yourself at home.
Summary
Neodymium magnets are powerful. Some have the capacity to interfere with or reset pacemakers. Never put a neodymium magnet in your mouth, and always keep it away from computers, credit cards, and other magnetized objects.
Ferrofluids create stains on skin and other materials, so appropriate measures should be taken to keep the fluid contained in the working area. Any stains may be removed immediately from hard surfaces with oil as a solvent and paper towels.
Objective
In this science project, you'll investigate the relationship between the amount of ferrofluid and the efficiency of plastic removal from a modeled waterway.
Introduction
Plastic pollution is a large issue around the world. In fact, around the globe, the production or creation of plastic has nearly doubled from 2005-2025 alone. Mass production of plastic is not sustainable for the environment, and recycling plastic alone will not address the issue of plastic pollution. Plastic pollution has been shown to have negative effects on the environment, impacting ecosystems and the organisms in them, including us. In fact, trace amounts of plastics have even been found in human tissues like the brain and liver, which are vital organs essential to our life and health. Although we don't currently know if plastics alone are harmful to human health, emerging research has shown that harmful chemicals called endocrine disruptors can bind to small pieces of plastic that can be ingested or breathed in and take hold in the tissues of our bodies. These harmful chemicals have been associated with human immune disorders and developmental, reproductive, and neurological issues.
What can we do about plastic pollution, and why is plastic pollution such a big problem? Well, first we would have to talk about plastic's physical properties. Some plastics take an extremely long time to break down, and need to be in the presence of ultraviolet (UV) light to do so. Therefore, by putting plastic in landfills and burying it, it is unable to break down. However, the breakdown of plastics in our environment is also problematic. Plastics can break down into tiny microscopic pieces of plastic called microplastics or nanoplastics, depending on their size. Microplastics are defined as being tiny pieces of plastic that are at least 5 millimeters in diameter or smaller. These microplastics are what is potentially harmful to our bodies and the ecosystem, particularly when they bind to other harmful chemicals and prevent them from being degraded and eliminated from us and the environment.
What do we know about the chemistry of microplastics that could help us remove them from the environment to reduce their impact and therefore reduce the amount in our bodies? Most microplastics are degraded from larger pieces of plastic, which are nonpolar, long polymer chains. Polymers are the base unit of a plastic. This means that they will typically interact with other nonpolar molecules, known as “like dissolves like” by chemists. Therefore, we can add a nonpolar solvent, like oil, to interact with the plastic, but not the polar molecule water. Solvents are used to dissolve a chemical. But, how can we remove the oil, containing plastic, from the water then?
Removing plastics from water is challenging, but it can be overcome with the use of ferrofluids. Ferrofluids are known as liquid magnets. They contain a suspension of ferromagnetic particles in a solvent, like oil, as seen in Figure 1. This fluid becomes thick and is magnetic, so it can be pulled out of a solution with a magnetic field generated by another magnet. Some solvents will also act as surfactants for the ferromagnetic particles, which helps stabilize the solution by preventing the magnetic particles from clumping together or coming out of the suspension of the solution. Once the ferrofluid is created by adding the ferromagnetic particles to the solvent, it can then be added to the water containing microplastics, and a magnet can be used to interact with the ferrofluid and physically pull the plastics out of the solution. How much ferrofluid is needed to remove common microplastics from water? You will test this out for yourself in this science project.
Image Credit: Laura Ohl, PhD / Science BuddiesImage of ferromagnetic powder interacting with oil-based solvent to form a ferrofluid.
Terms and Concepts
- Sustainable
- Microplastic
- Nanoplastic
- Nonpolar
- Polymer
- Dissolve
- Solvent
- Polar
- Ferrofluid
- Surfactant
Questions
- Why is the plastic production rate not sustainable for the environment?
- How many different plastics are produced around the world?
- What are microplastics, and what causes this?
- What are the most common types of microplastics in the environment?
- What are plastics made of?
- What is their chemical behavior (polar or nonpolar)? What is the polarity of water and oil?
- What is a solvent, and how does it compare to a surfactant?
- What is a ferrofluid?
- How do you expect the ferrofluid and plastics to interact based on their chemistries?
Bibliography
- Baldwin et al. (2016, September 14). Plastic Debris in 29 Great Lakes Tributaries: Relations to Watershed Attributes and Hydrology. Retrieved May 7, 2025.
- O'Sullivan, C. (2014, December). Microplastics: An Issue of Scale. Retrieved May 12, 2025.
- Haederle, M. (2025, February 28). UNM Researchers Find Alarmingly Hihg Levels of Microplastics in Human Brains - and Concentrations are Growing Over Time. Retrieved May 15, 2025.
Materials and Equipment 
Recommended Project Supplies
The Ferrofluid Nanotechnology Kit is available from our partner Home Science Tools®.
The Ferrofluid Kit Contains:
- 10 Petri dishes, polystyrene, 90 x 15 mm
- 1 graduated cylinder, glass, 25 mL
- 2 pipets, disposable, 1 mL, 10 pack
- 30 mL mineral oil, Klearol (only need 1 bottle)
- 3 pairs gloves, nitrile, medium
- 50 mL ferrofluid (smaller volume also possible)
- 1 neodymium block magnet, 0.75" x 0.50" x 0.25"
Additional items needed:
- An apron or clothes that can be stained
- Lab notebook
- Water
- Cup (for water)
- Kitchen scale
- Ruler
- Scissors
- 1 piece of plastic, such as a plastic container or bottle (preferably one type of recyclable plastic not a mixed plastic, we recommend #1, which is PET or PETE )
- Small cups or weigh boats to weigh microplastics
- Food coloring, any color (optional)
- Sink with hot water
- Dishwashing liquid
- Small plastic bag (or reuse bags provided in kit for mineral oil)
Experimental Procedure
Scientific Method. Review the steps before you begin.
Neodymium magnets are very strong. Adult supervision is recommended when using them. Be careful not to drop the magnets, and do not let them slam together or fall. They may pinch your fingers, crack, or shatter. Keep magnets away from small children, pets, credit cards, and pacemakers.
- Prepare the microplastic pieces.
- Cut a piece of plastic into strips measuring less than 5 millimeters (mm) in width.
- Cross-cut the plastic strips into pieces less than 5 mm in height to create microplastic pieces.
- Cut 20 pieces of plastic of similar size for each of the three Petri dishes, or 60 pieces total.
- Count the number of pieces and evenly divide them between 3 small cups or weigh boats so you can easily add them to each Petri dish later. Record the number of pieces in each weigh boat in Table 1.
- Weigh each group of plastic pieces to ensure they are consistent in weight between conditions. If they are not the same weight between weigh boats, redistribute the plastic pieces to ensure there are the same number of pieces and the same weight for each weight boat. Record the final weights in Table 1.
- Put a pair of gloves on to prevent the ferrofluid from touching your skin.
- Prepare the water solution, which will simulate having multiple water systems (in each Petri dish) to clean up.
- Add 100 mL of water to a cup.
- Add 1-2 drops of food coloring to the 100 mL of water (optional). This will help visualize the water compared to the ferrofluid in the Petri dishes.
- Open each of the 3 Petri dishes with the insides facing up. The bottom halves will simulate water systems treated with increasing ferrofluids to remove the microplastics, and the top shallower halves will collect the microplastics removed from the water. Refer to Figure 2 for the experimental layout.
- Measure and pour 15 mL of water into the bottom half of each Petri dish.
- Measure and pour 2 mL of mineral oil into each Petri dish.
- Add an increasing amount of ferrofluid to each Petri dish. Add 0, 5, or 10 drops to one of the Petri dishes using the micropipette.
- Mix the solution using the end of a clean micropipette to solubilize the ferrofluid in the excess oil solvent.
- Prepare to remove the microplastics from each Petri dish, representing a microplastic-contaminated water system.
- Starting with the 0 drops of ferrofluid condition, drag the magnet across the surface of the liquid, immersing the magnet right below the water's surface.
- Repeat this step 3-5 times per dish, keeping the times the magnet is used in each Petri dish consistent between trials.
- Place any removed plastic onto the empty top of the Petri dish to count later.
- Clean the magnet between each Petri dish.
- Repeat these steps for the 5 drops and 10 drops of ferrofluid Petri dishes, keeping the number of times and method of using the magnet in each Petri dish consistent between each trial.
- Note: You can place the magnet into a plastic bag to speed up the cleanup process at the end (optional). This may interfere with the magnet's ability to pick up the microplastics.
- Count the number of plastic pieces removed, and record this data in Table 1.
- Calculate the efficiency of plastic removed in each trial, using Equation 1.
- Record the percent efficiency of plastic removed in Table 1.
- Repeat the entire experiment three times to ensure reproducible results for each ferrofluid amount. For each trial of the full experiment, create a new data table, like Table 1 below.
- Use your data to make conclusions about your experiment.
- How much plastic was removed from each Petri dish?
- What is the relationship between the amount of ferrofluid and the efficiency of plastic removal from each Petri dish?
- What did you observe about the ferrofluids and oil solution as the amount of ferrofluid increased?
- Are ferrofluids a good way to remove plastic from water, based on your observations and data? Use this information to inform your answer. Are there any concerns you have about it removing plastics from water in large waterways?
Image Credit: Laura Ohl, PhD / Science BuddiesExperimental setup for ferrofluid removal project showing inner part of petri dishes facing up to retain fluids.
| Ferrofluid Amount | Weight of microplastic pieces (g) | Number of plastic pieces (before) | Number of plastic pieces removed (after) | Percent efficiency of plastic removed (%) |
|---|---|---|---|---|
| 0 drops | ||||
| 5 drops | ||||
| 10 drops |
Ask an Expert
Variations
- Does the ferrofluid method of plastic removal work better for some single-type plastics than others? Create microplastics from multiple types and record their removal efficiency.
- Do ferrofluids work for mixed plastics? Test this method with a mixed plastic to test if it is possible!
- Are ferrofluids harmful to waterways? Do your own research to find out, and test how much of it can be removed from each water system after plastic cleaning up. Count the number of magnet swipes across the surface required to clean up the ferrofluid or the volume that can be extracted. Based on your results, does adding more or less oil or ferrofluid help with the removal process? Is there an optimal ratio of ferrofluid and solvent to ensure proper cleanup of waterways after plastic removal?
- Do ferrofluids with other solvents perform better than others at extracting microplastics from water? This study tested a ferrofluid with mineral oil as the solvent. In addition to different solvents, such as olive or vegetable oil, you can test different metal powders, such as aluminum and stainless steel. Ensure your magnetite powders do not contain contaminants, which will impact your results. These impurities can be cleaned by rinsing the powder multiple times with water and fully drying it before use. You could also test other surfactants.
- Which ferrofluids are best at extracting smaller pieces of plastic? Grind down your plastic with coarse and then fine sandpaper to see if this method works for even smaller pieces of plastic that are harder to see and measure. Use weight to keep track of its extraction.
- How do ferrofluids compare to other plastic removal techniques? Do your own research on different methods of plastic removal from water or land, such as microplastic removal from soil with mushrooms, and compare their percent removal and the time it takes to remove the plastic from the water or soil for each condition. Are some methods better for land or water environments? Use your results to explain your answer.
Careers
If you like this project, you might enjoy exploring these related careers:
Contact Us
Our kits are developed in partnership with Home Science Tools®. If you have purchased a kit for this project, Home Science Tools® is pleased to answer any questions.In your email, please follow these instructions:
- Include your Home Science Tools® order number.
- Please describe how you need help as thoroughly as possible:
Examples
Good Question I'm trying to do Experimental Procedure step #5, "Scrape the insulation from the wire. . ." How do I know when I've scraped enough?
Good Question I'm at Experimental Procedure step #7, "Move the magnet back and forth . . ." and the LED is not lighting up.
Bad Question I don't understand the instructions. Help!
Good Question I am purchasing my materials. Can I substitute a 1N34 diode for the 1N25 diode called for in the material list?
Bad Question Can I use a different part?
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Related Links
- Science Fair Project Guide
- Other Ideas Like This
- Environmental Science Project Ideas
- Green Chemistry Project Ideas
- My Favorites
- With our oil spill clean-up science project instructions, you can use this same kit to learn how ferrofluids can also be used to clean up oil spills in the ocean.
