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Surfactants in the Environment

Instructor: Amanda Robb

Amanda holds a Masters in Science from Tufts Medical School in Cellular and Molecular Physiology. She has taught high school Biology and Physics for 8 years.

Learn about surfactants and their role in the environment and living things. We'll cover uses for biodegradable surfactants and how surfactants are used in the human body during respiration and digestion.

What Are Surfactants?

Do you wash your clothes? Scrub the dishes? Do you eat and breathe? If the answer is yes to any of these questions, you're using surfactants! Surfactants are a type of detergent that reduces the surface tension between two liquids or a liquid and a solid.

They have hydrophilic parts that mix with water and hydrophobic parts that don't mix with water. This allows them to blend hydrophilic and hydrophobic materials, such as oil and water.

Surfactants are used in laundry and dish detergent to bind hydrophobic dirt molecules and dissolve them in water. They are also used in many types of industrial manufacturing. Surfactants help dissolve dye into fabrics, creating perfumes, insecticides, and fungicides.

Biodegradable Surfactants

Surfactants traditionally have been human-made and can be harmful to the environment, particularly aquatic ecosystems. In an effort to reduce this negative impact, scientists have developed biodegradable surfactants.

Biodegradable surfactants are surfactants that readily dissolve in water and can be broken down by living organisms into non-toxic products. This ensures that when the surfactants enter water treatment plants, they are broken down and do not enter the ecosystem when waste water is returned to the land.

However, simply degrading in water does not ensure that the products are safe. Many chemicals can be extremely toxic to humans and the environment. Products from degradation of surfactants have been known to cause cancer and reproductive problems.

For surfactants to be considered 100% biodegradable by the Environmental Protection Agency (EPA), they must not only degrade in water but also not create known carcinogens or mutagens. Fortunately, many studies have shown that biodegradable surfactants are just as efficient as their non-biodegradable counterparts, making them an excellent choice for reducing human impact on the environment.

For example, surfactants are a common ingredient in spray pesticides such as Roundup. Since traditional pesticides were created from chemicals like petroleum, there was concern about applying them directly into the environment. However, studies have shown that biodegradable rapeseed oil-based surfactants were similarly effective, presenting a viable alternative to non-biodegradable pesticides.

Uses

Biodegradable surfactants present an opportunity to use the benefits of surfactants without causing harm to natural ecosystems, such as in retaining soil moisture. Natural surfactants also exist in our body to assist in the basic functions of breathing and digestion.

Soil Moisture

Creating safe, biodegradable surfactants is important so that they may safely be used in terrestrial and aquatic ecosystems without harming plant and animal life.

One application of surfactants is to increase water absorption by soil. After a drought dry soil is extremely dry. Dry soil is hydrophobic and the surface tension between the dirt molecules prevents water from entering the soil, even after a rain.

Biodegradable surfactants can be applied to the soil to increase water absorption. Surfactants create hydrophilic surfaces when applied to the soil while simultaneously binding to hydrophobic soil molecules. This reduces surface tension between soil molecules, which allows the water to penetrate the ground.

And increase in water absorption by soil is important for rejuvenating dry soil for agricultural purposes, but it can also be important for a type of dam that uses soil as the construction material, called an 'earth dam'. These types of dams must remain moist to stay functional. Surfactants can help prevent the dam walls from drying out, just as they do in agricultural soil by decreasing the surface tension between dry soil molecules and allowing water to penetrate.

Respiration

Take a moment to take a deep breath. The reason you can use this relaxation technique is due to surfactants. Your lungs are a maze of tiny air airways that dead end in small sacks called alveoli. The alveoli are composed of living cells, which need to stay moist to stay alive.

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