Durable plastic doubles as a CO2 cleaner
Melamine, a small aromatic molecule loaded with nitrogen
atoms, has traditionally found fame as a tough plastic that is ideal for making
durable dishware and laminate coatings. Research by Mei Xuan Tan, Yugen Zhang
and Jackie Ying at the A*STAR Institute of Bioengineering and Nanotechnology,
Singapore, has shown that this material could play a valuable role in reducing
greenhouse gas emissions. They demonstrated that a synthetic procedure turns
melamine polymers into low-cost ‘scrubbers’ that trap and release carbon
dioxide (CO2) gas on demand ("Mesoporous
Poly(Melamine–Formaldehyde) Solid Sorbent for Carbon Dioxide Capture").
Conventional scrubbers use amino alcohols as liquid sorbents
to catch waste CO2 gas. The intense energy needed to regenerate
these corrosive and unstable liquids after carbon capture has prompted a search
for better alternatives. One approach employs highly porous materials, such as
activated charcoal or inorganic zeolites, to soak up large quantities of
polluting gases. Unfortunately, most porous substances have poor selectivity
towards CO2 and thus must be replaced often.
Tan, Zhang and Ying investigated whether these problems
could be alleviated using porous organic polymers as the robust substances can
be chemically tuned to maximize carbon capture. Because melamine has an
abundance of amino sites that selectively bind CO2, the team
suspected it might act as an efficient sorbent. Until now, however, chemists
could introduce pores into melamine polymers only through the use of complex
inorganic templates.
The production of melamine plastics usually requires the use
of formaldehyde dissolved in water — a procedure that yields little to no
porosity. By switching to a more polar organic solvent known as dimethyl
sulfoxide (DMSO) and higher reaction temperatures, the researchers generated a
high-surface-area polymer with well-defined ‘nanopores’. They theorize that
DMSO bonds to melamine and formaldehyde early in the process and helps to
assemble the molecules into nanometer-wide rings, which subsequently link
together into a foam-like structure.
Tests revealed that the new melamine polymer had impressive
carbon capture capacity — it removed over 99% of CO2 from an analyte
gas in a typical industrial through-flow column setup and operated nearly
instantaneously. Furthermore, the researchers could quickly remove adsorbed CO2
by applying a vacuum that restored its scrubbing capabilities for numerous
cycles. The team attributes this unique behavior to reversible CO2
binding inside the polymer’s nanopores.
“Compared with other carbon dioxide capture materials,
poly(melamine–formaldehyde) is cost efficient, easily synthesized and can be
readily scaled up. We welcome industrial partners to work with us to
commercialize this technology,” say Zhang and Ying.
Read more:
http://www.nanowerk.com/news2/green/newsid=32443.php?
