Filtration of Microplastics: Pumice versus Activated Carbon

By: Mohan G.
Year: 2024
School: Fairmont Private Schools, Anaheim Hills
Grade: 6
Science Teacher: Michael Morin

Microplastics, tiny plastic debris less than 5 mm in size, have become a significant threat to our ecosystem. These minuscule particles, which can take hundreds to thousands of years to degrade, are now pervasive in our water, air, and marine life. Not only do they harm the environment, but they also pose health risks to humans. Global efforts are in progress to mitigate this issue, but finding effective and sustainable solutions remains a challenge.

One of the most common methods for filtering microplastics from water involves the use of activated carbon. Activated carbon is known for its high porosity and effectiveness in trapping contaminants. However, its production requires industrial processing, which is costly and contributes to its own carbon footprint. In light of these drawbacks, Mohan’s award-winning science fair project explores an innovative alternative: pumice.

Pumice is a naturally occurring, highly porous material formed from volcanic eruptions. Unlike activated carbon, pumice is abundant, widely available, and does not necessitate additional processing. Mohan hypothesized that pumice could be just as effective as activated carbon in filtering microplastics due to their similar porous nature.

To test this hypothesis, Mohan designed an experiment comparing the filtration efficiency of activated carbon and pumice. He constructed filtration tubes filled with each material and passed water containing microplastics of two different sizes (0.75 mm and 0.05 mm) through them. The goal was to evaluate the effectiveness of each filtration agent in trapping these tiny particles.

Mohan found that pumice was equally effective as activated carbon in filtering out microplastics. For the smallest particles, pumice even demonstrated superior performance. This discovery is significant as it suggests that pumice, a naturally occurring and readily available material, could be a more sustainable and cost-effective solution for microplastic filtration.

Despite the success of his experiment, Mohan acknowledges certain limitations. Measuring microplastics, given their tiny size, often requires sophisticated techniques like spectroscopy. In this project, simpler methods were used, which may impact the precision of the results. Additionally, Mohan suggests that using even smaller pieces of pumice and activated carbon could enhance filtration efficiency by increasing the surface area. Extending the length of the filtration channel could also improve performance by providing more contact time for the water with the filtration material.