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When there have been major oil spills, like the Exxon Valdez and the spill in the Gulf, chemicals are often dispersed on the surface of the ocean to absorb the oil. How does this chemical reaction work? How much of the oil is really absorbed?
Question Date: 2010-05-13
Answer 1:

Chemicals dispersed to absorb oil are called sorbents. The Environmental Protection Agency (EPA) lists the following materials as sorbents for cleaning up oil spills:

1. Organic products

1. Peat moss or straw;
2. Cellulose fibers or cork;
3. Corn cobs;
4. Chicken or duck feathers.

2. Mineral compounds

1. Volcanic ash or perlite;
2. Vermiculite or zeolite.

3. Synthetic products

1. Polypropylene;
2. Polyethylene;
3. Polyurethane;
4. Polyester.

Oil is hydrophobic meaning that it does not like to mix with water.Each of the sorbents is also relatively hydrophobic so it is favorable for the oil to be absorbed by these materials rather than remain in full surface contact with the water. Absorption is not a chemical reaction but rather a physical process in which one material (the oil)goes into the bulk volume of another material (the sorbent). These materials can work well to clean up small spills, but it is not necessarily practical to store and move large amounts of sorbent to clean up very large spills.

For absorbent bales or rolls made of polypropylene, about 2 gallons of oil can be absorbed per pound of material. The Exxon Valdez oil spill involved around 10 million gallons of oil which would require 5million pounds of polypropylene. The spill in the Gulf is releasing anywhere from 200,000 to 4 million gallons per day. As you can imagine, producing such large amounts of sorbent is both time consuming and expensive. Transporting and disposing of the sorbent adds additional expense.

Other chemical and bio-remediation methods also exist to aid in cleaning up oil spills. Additional chemical methods involve dispersing and gelling agents. Dispersing agents break the oil into droplets so that it can disperse more easily instead of forming slicks. When the oil disperses it is easier for it to naturally biodegrade. Gelling agents mix with the oil to form a gel that is easier to physically remove from the water than liquid oil. Bio-remediation involves the use of microorganisms to increase the rate at which the oil is biodegraded.

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