A Single Atom Makes
All the Difference
One atom can
make all the difference in the world. Change one atom and the neutral
smell of water becomes the stench of a poisonous gas. Lose an oxygen atom
when chlorophyll decays, and the colors of an autumn fall develop. The
same is true for environmental effects: slight changes in a molecule's
make-up can signal dramatic environmental benefits.
Take chlorine, for
example, which was once used to make paper white. There's a raging debate
over its use, but this has created more heat than light. For instance,
remove one chlorine atom in the chlorine gas molecule and replace it with
two of oxygen to create chlorine dioxide.
"So you would think
chlorine dioxide is similar to chlorine since they both have the same
word in their names. But the chemistry is fundamentally different. Hydrogen
is in both water and hydrogen cyanide, but the latter can be a deadly
gas," said Doug Pryke, Executive Director of the Alliance for Environmental
is today the best bleaching agent bar none in terms of environmental performance
and product quality. "In fact, chlorine dioxide is a solution to the problem
of persistent, bio-accumulative toxic substances in mill waste water,"
added Dr. Donald Mackay of the International Joint Commission Virtual
Elimination Task Force.
AET is a group of
North American chemical manufacturers established to research and promote
proven, practical technologies to raise the environmental performance
of the pulp and paper industry. AET commissioned an assessment of the
ecological effects of chlorine dioxide bleaching. The report, written
by a panel of some of the world's foremost scientists in the field, was
the first of its kind to follow the US Environmental Protection Agency's
Framework for Risk Assessment.
The authors reached
a unanimous opinion. "The environmental risks of chlorinated organics,
i.e. chlorine containing substances, in the waste water of a modern mill
using chlorine dioxide bleaching are insignificant," stated Dr.
Keith Solomon, Director of The Centre for Toxicology, who along with Dr.
Mackay helped prepare the report.
In short, the public
should not have to worry about the risks to human health and to the environment
from chlorine dioxide.
These dramatic findings
result from the way chlorine dioxide reacts with organic material such
as lignin, the tissue that hold a plant's cellular wall together, and
which is eliminated during bleaching. Chlorine gas reacts with lignin
to create certain compounds that can be potentially harmful. Chlorine
dioxide, on the other hand, breaks these compounds apart. As the rate
of chlorine dioxide use approaches 100 percent, the formation of these
potentially harmful substances falls to zero.
Small changes in
molecular structure can generate very large differences in effect. The
molecules responsible for the striking blue of the cornflower differs
only from the scarlet red of the periwinkle by one hydrogen atom -- an
example of the wonders of the natural world.
And in papermaking,
the switch from molecular chlorine gas to chlorine dioxide -- a seemingly
small change on the molecular level -- results in significant environmental
improvement. "It's an elegant solution to a complex problem," said Pryke.