ECU Chemist touts benefits of "Subcritical Water"
(June 14, 2001)
There are days when award-winning chemistry professor Yu "Frank" Yang of East Carolina University confides to his students: "I'm not a chemist. I'm a plumber."
Those are the days when he's adjusting valves and stainless tubes and connecting hollow strands of wire, no thicker than a treble string on a guitar, to ovens and pressurizing devices.
The purpose is to produce and study what he calls "subcritical water." It's a relatively benign fluid; in fact it's water in its purest form, that could someday replace the toxic and expensive organic solvents used in industry and chemical laboratories. It also shows promise as a way to extract dangerous pesticides and PCBs from the soil at building sites and farm lands.
In explaining the nature of "subcritical water," Dr. Yang said water exists in three forms. It's a liquid, a gas and a solid and it reacts differently to temperature and pressure. Heat it and it boils. Cool it and it freezes. Pressurize it and unusual things happen.
For example, when the pressure of the liquid is changed from its usual one atmosphere to 50 atmospheres, it goes into a "subcritical" state and ceases to be the water that we all know and depend on to boil for coffee or freeze for ice.
In fact, the boiling point for water at 50 ATM pressure is about 392 degrees F and is almost twice as hot as the 212 degrees F that boils tap water on the stovetop.
The results, says Yang, is that the water in this "subcritical" state behaves like a solvent. A drop of this water on a strand of hair, for example, will cause the hair to dissolve. The hair strand will separate into different components than can be recorded, measured and analyzed.
"Many liters of organic solvents are used and disposed of daily," said Yang. He said the solvents are toxic and special care has to be taken in order to dispose of them properly. The solvents are also expensive.
"Water is much cheaper and safer," he said. "If there is a way to do something better, why not do it."
He said "subcritical water" could also dissolve and extract the toxic chemicals found in soils contaminated by pesticides and PCBs. This would require the development of a field unit that could operated at the contamination site.
Yang completed his undergraduate and graduate degrees in China and his doctorate in Germany. He joined ECU in 1997 after serving on the staff at the Energy and Environmental Research Center in North Dakota.
He has labeled his research as "Green Chemistry" because it uses environmentally friendly "subcritical water" instead of organic solvents. His work has gained international attention and he has been asked to address the 10th International Symposium on Supercritical Fluid Chromatography Extraction and Processing scheduled for next August.
He also recently received a renewal of a Cottrell College Science Award from Research Corporation for $49,418 to continue his study of the uses of subcritical water. In making the award to Yang for the second time, Research Corporation officers gave high praise to Yang's work.
Along with the research grants, the ECU professor has been singled out for his abilities as a teacher. He was among this year's recipients of the prestigious UNC Board of Governors' Distinguished Professor for Teaching Award.
"I love teaching," he said. "I get inspired by my students. I've found that if I'm excited about the work the students are affected and become excited, too."