Passage III

Oil spills in the ocean are cleaned up by using a sorbent to soak up the oil floating on the water’s surface. Two studies examined the effectiveness of 4 sorbents: 3 natural (milkweed, cotton, and kenaf ) and 1 synthetic (polypropylene).

Before the studies, the following procedures were performed for each sorbent: A 1 g sample of the sorbent was completely dried and then placed in a beaker containing 500 mL of seawater. Ten minutes later, the sample was removed from the beaker and its mass was measured. The mass of seawater the sample had soaked up, m_s, was calculated. The sample was discarded.

Study 1

The following procedures were performed for each sorbent:

• A 500 mL volume of seawater was poured into each of 5 identical 1 L beakers.

• A different mass of heavy crude oil—10 g, 20 g, 30 g, 40 g, or 50 g—was added to each beaker.

• A 1 g sample of completely dried sorbent was added to each beaker.

• The beakers were gently shaken for 10 min.

• Immediately after the beakers were shaken, each sample was removed from its beaker, and its final mass, m_f , was measured. The mass of oil that had been soaked up by the sample, m_o, was calculated as follows:

m_o = m_f − m_s − 1 g

The results, given in grams of oil soaked up per gram of sorbent, are shown in Figure 1.

Study 2

The procedures of Study 1 were repeated except that each sorbent was placed in light crude oil and seawater instead of heavy crude oil and seawater. The results are shown in Figure 2.