Several factors determine how effective an adsorbent is at environmental cleanup. These include not only surface area, but also chemical structure, pore size and particle size. Activated carbon, because it's so porous, is an example of a very effective and widely used adsorbent. Amazingly, under the right conditions, one gram of activated carbon can have a total surface area of five football fields [source: EPA]. Carbon becomes activated when it's heated and treated with oxygen to increase the pore structure. The activated carbon is then effective at eliminating impurities from water (thus its use in household water filters) as well as cleaning the air of noxious gases in gas masks. Other uses for activated carbon include eliminating solvents, odors, gases and gasoline vapors.
Other common adsorbents include silica gel, effective in removing inorganic gases and purifying gas, and molecular sieves, effective in removing nitrogen oxide. Among other things, activated alumina works to remove polychlorinated biphenyls (PCBs). PCBs are synthetic compounds used especially in the electrical industry until the 1970s, when they were banned. But because they don't biodegrade, large amounts of PCBs still pollute the water, soil and air.
In addition, adsorbents (more so than absorbents) are used to supplement oil spill cleanups. They usually aren't effective as the primary method of cleanup unless the oil spill is very small, but they're useful for the final stages of the cleanup. The best adsorbents for cleaning oil from water are both oleophilic (oil-attracting) and hydrophobic (water-repellent). Think about how you need soap and not just water to clean the natural oils from your hair, or about how feathered animals get can get drenched in black oil that doesn't rinse off. For the same reasons, hair and feathers make effective adsorbents for cleaning up oil spills in the water.
For lots more information on environmental cleanup, see the links below.
- Air Pollution Training Institute. "APTI 415: Control of Gaseous Emissions: Chapter 4: Adsorption." EPA. (March 28, 2012) http://www.epa.gov/apti/Materials/APTI%20415%20student/415%20Student%20Manual/415_Chapter_4_12-15-2008.pdf
- Air Pollution Training Institute. "SI:431 Air Pollution Control Systems for Selected Industries: Lesson 6: Adsorbers." EPA. (March 28, 2012) http://yosemite.epa.gov/oaqps/eogtrain.nsf/fabbfcfe2fc93dac85256afe00483cc4/1453fe02b1ff08af85256b88004ca92f/$FILE/si431-lesson6.pdf
- Dynamic Adsorbents, Inc. "PCB Removal: Frequently Asked Questions." Dynamic Adsorbents, Inc. (March 28, 2012) http://www.pcbremoval.net/faq.htm
- EPA. "Cleaning Up Our Land, Water and Air." Environmental Protection Agency. Last updated Jan. 17, 2012. (March 30, 2012) http://www.epa.gov/cleanup/
- EPA. "Sorbents." Environmental Protection Agency. Last updated Jan. 27, 2011. (March 30, 2012) http://www.epa.gov/osweroe1/content/learning/sorbents.htm
- ITOPF. "Use of Sorbent Materials in Oil Spill Responds." The International Tanker Owners Pollution Federation Limited. (March 30, 2012) http://www.itopf.com/information-services/publications/documents/TIP8UseofSorbentMaterialsinOilSpillResponse.pdf
- Pani, Balram. "Textbook of Environmental Chemistry." I.K. International Pvt Ltd. Jan 1, 2007. (March 30, 2012) http://books.google.com/books?id=Y7GyU5SVLkQC