...From the pages of Agricultural Research magazine
Ultrasound: An Environmentally Friendly Tool for the Textile Industry
Chemical engineer Allan Lambert
prepares an enzyme processing
solution before treating fabric.
Most people associate ultrasound technology with obstetricians,
not textile manufacturers. But that may change in the near future, at
least in the world of cotton processors, because of work being done
by chemical engineer Val Yachmenev and his colleagues at the Agricultural
Yachmenev, who works in the Cotton Textile Chemistry Research
Unit (CTCRU) at ARS' Southern Regional Research Center in New Orleans,
Lousiana, has found that ultrasound can boost enzymatic activity during
several different types of treatments to cotton fibers.
Enzymes are protein molecules that can speed up complex chemical reactions. They act as catalystssubstances that start or accelerate chemical reactions without themselves being affected. Human saliva, for example, contains amylase, an enzyme that helps break down starchy foods into sugars.
Chemical engineer Val
Yachmenev inspects a
sample of cotton fabric
after an enzyme-ultrasonic
"Use of enzymes in the cotton industry has become
more popular in recent years," says Yachmenev, "because scientists
have developed highly specific enzymes that perform textile-processing
tasks." Enzymatic treatments have been used for a long time to
remove the starch size that's added to cotton yarns to smooth and protect
them from breaks during weaving. But new processing applications have
been developed for scouring (removing natural waxes, pectins, and fats
from the surface of cotton fibers), biofinishing (removing fiber fuzz
and pills from fabric surface), and biostoning (removing color and softening
denim fabrics for a stone-washed effect). Enzymes are also used in laundry
detergent, to remove fiber fuzz and various stains, and in bleach cleanup
after scouring to eliminate problems during the dyeing process.
Yachmenev says that enzymes use significantly less water,
less energy, and fewer chemicals than traditional methods. In addition,
wastewater from enzymatic treatments is readily biodegradable and does
not pose an environmental threat.
Gene Blanchard, CTCRU's research leader, describes differences between traditional and enzymatic scouring methods: "To scour cotton fibers the old-fashioned way, you boil them in a highly alkaline solution at temperatures of 100° C. Afterwards, you're left with alkaline wastewater that must be neutralized with an acid or diluted with large amounts of fresh water.
Chemist Gene Blanchard (left)
observes as chemical engineer
Val Yachmenev prepares cotton
samples for enzyme-ultrasonic
"If you use an enzymatic treatment," Blanchard
continues, "you only have to heat the solution to about 50°
C for optimum enzyme performance. You don't expend as much energy, you
do less damage to the textile, and the resulting wastewater is biodegradable."
Although enzymatic processing offers many advantages,
there are a few drawbacks when compared to traditional methodsnamely,
expensive processing costs and relatively slow reaction rates. "These
drawbacks could impede widespread use of enzymes by the textile industry,"
But ultrasound technology may help make up for enzymatic
It's In the Bubbles
Ultrasound can be defined as sound waves with frequencies above 20,000
oscillations per second, which is above the upper limit of human hearing.
In liquid, these high-frequency waves cause the formation of microscopic
bubbles, or cavitation. They also cause insignificant heating of the
When fabric is placed in an enzymatic solution, enzyme molecules, which
are relatively large, make their way to the fabric and are adsorbed
onto the surface. The enzymatic reactionbiostoning, scouring,
etc.occurs when the enzymes reach the place where solid and liquid
meet, the "solid/liquid interface."
Although this seems like a straightforward process, it can take awhile
because of the enzymes' large size. Yachmenev says, "These bulky
molecules don't move toward the interface very quickly. And their size
makes it hard for them to penetrate the nearly immobile layer of liquid
that sits right next to the fabric surface."
Yachmenev decided that the best way to accelerate the transport of
enzymes through this liquid barrier was to shake things up. He chose
ultrasound as his tool.
"Ultrasound causes cavitational bubbles to form in liquid. When
the bubbles collapse, they generate tiny but powerful shock waves. I
knew we needed to agitate the border layer of liquid to get the enzymes
through the barrier more quickly, and these shock waves seemed like
the perfect stirring mechanism," he says.
Some scientists had speculated that ultrasonic energy would be too
powerful to use as a stirring toolthat it would tear apart the
large, yet fragile, enzyme molecules. To prevent this from happening,
Yachmenev and Blanchard diffused the ultrasound energy uniformly through
a solution with low enzyme concentrations.
The experiment was a success. Enzymatic treatments supplemented with ultrasonic energy resulted in shorter processing times, less consumption of expensive enzymes, less fiber damage, and better uniformity of treatment to the fabric.
All of Yachmenev's experiments were conducted in a laboratory that
houses a small-scale ultrasound machine. Some textile manufacturers
have expressed interest in the technology, but they would need large,
industrial-grade equipment to achieve similar results at the mass-production
level. Unfortunately, most ultrasound manufacturers produce only smaller
machines for the medical and research communities.
Yachmenev has contacted manufacturers from around the world trying
to generate interest. He says it would be a good investment because
the technology's usefulness isn't limited to just the textile industry.
"It can be used to intensify enzymatic treatments in any solid/liquid
system," he says.
"For example, the paper industry would be an excellent candidate
for using ultrasound. Paper producers have had problems in the past
with meeting environmental standards, and they have been moving toward
enzymatic treatments. Ultrasound would make these treatments more cost-effective,"
"I believe enzymatic treatments are the wave of the future,"
he continues. "Governments worldwide are calling for a reduction
in the quantity and toxicity of wastewater, and using enzymes would
help factories and manufacturers achieve this goal. Ultrasound will
help them achieve it at lower costs."
An article about Yachmenev's work appeared in the Journal of Chemical Technology and Biotechnology in May 2002.By Amy Spillman, Agricultural Research Service Information Staff.
This research is part of Quality and Utilization of Agricultural
Products, an ARS National Program (#306) described on the World Wide
Web at http://www.nps.ars.usda.gov.
Val G. Yachmenev
and Eugene J. Blanchard
are in the USDA-ARS Cotton Textile Chemistry Research Unit, Southern
Regional Research Center, 1100 Robert E. Lee Blvd., New Orleans,
LA 70179-0687; phone (504) 286-4577 [Yachmenev] or (504) 286-4495 [Blanchard],
fax (504) 286-4271.
"Ultrasound: An Environmentally Friendly Tool for the Textile Industry" was published in the February 2003 issue of Agricultural Research magazine.