Sponges absorb, but geckos adsorb -- that is, these salamander-like creatures can run up and down tree trunks and walls because the soles of their feet are covered with legions of tiny hairs, said Yang, a professor and chemical engineer at the University of Michigan. The hairs insert so close to a surface that their molecules actually attract each other in a brief defiance of gravity.
But why study adsorption as a separation technique? "Over 90 percent of separations in the industry are done by distillation," or selectively boiling off compounds, said Yang. "That's very energy-intensive. Adsorption isn't. It can also help with boiling points that are too close."
Thus the focus of Yang's research team is developing new sorbent materials whose surfaces attract and pluck out one particular compound from a mixture. "We're most excited about desulfurizing gasoline and diesel fuel," he said. Most fuels now contain more than a gram of sulfur per gallon, which contributes to acid rain. New federal standards are coming in 2006, however, to reduce those levels drastically.
"Reaching those levels with the current industry method would mean reactor size must increase by a factor of 15. Companies are saying they can't do that," said Yang. "So we've developed a very selective sorbent material based on crystal minerals that can do this -- and be regenerated."
For Yang, who as a boy moved with his family from mainland China to Taiwan in 1949, deciding on chemistry as a career was a natural choice: "In high school, the best students went into science and engineering, and I worked hard to be one of them," he said.
Yang received his undergraduate degree from the National Taiwan University in 1964 and his Ph.D. from Yale University in 1971. He is a member of the ACS industrial and engineering chemistry division.
The ACS Award in Separations Science and Technology is sponsored by IBC Advanced Technologies, Inc.