Chemical Engineering December 2020 - 7

Graphene-oxide filtration membrane for harsh
chemical environments
F
Via
iltration is being investigated as an alternative
to thermal separation methods
(such as distillation and evaporation)
in many applications because
of the potential energy savings, but conventional
filtration membranes, such as those
used in water desalination, are often not robust
enough to withstand high temperatures
and harsh chemical conditions.
Proprietary link
has been removed during paper manufacturing.
Initially, the black liquor contains about
12-15% solids, and it needs to be concentrated
to 70% solids in order to recover and
recycle the organic chemicals from the black
liquor back into the pulping process.
Via's membrane consists of grapheneoxide
(GO) flakes cast onto a hydrophilic
support material through a proprietary deposition
procedure. The resulting
scaffold of GO flakes
is bound together by customizable
molecular links that
allow the scientists to manipulate
the amount of space
between the GO sheets. " The
assembly process with the
GO and linkages can be run
Proprietary link
Now, Via Separations (Somerville, Mass.;
www.viaseparations.com) has demonstrated
a process for making graphene-oxide (GO)
membrane material that can withstand harsh
conditions. In its first commercial application,
the GO membrane is being employed for the
concentration of black liquor in pulp-and-paper
operations, where the membrane experiences
very high pH.
A byproduct from wood-pulping processes,
black liquor contains lignin, hemicellulose and
inorganic materials from wood, after cellulose
in a variety of ways, " explains Via engineer
Lauren Kovacs. " The GO chemistry allows
for customizations to separate materials
with varying molecular weights. "
The resulting membrane is robust
enough to separate solids at pH levels of
13-14. The membrane material is then spiral-wound
into modules similar to the configuration
of a reverse-osmosis membrane.
Via engineers are building a portable pilot
system for black liquor concentration that will
be set up at a paper mill in early 2021.
This additive reverses the effects of aging in
recycled asphalt pavement
A
new rejuvenator technology aims to
improve the chemistry and service
life of recycled asphalt pavement
(RAP). The Invigorate additive, developed
by Colorbiotics (Ames, Iowa; www.
colorbiotics.com) based on Iowa State University
research (www.iastate.edu), helps
overcome issues with asphaltene aggregation
and oxidation, which occur as RAP ages,
and enables mixtures with more recycled
content. " When asphalt ages, oxygen becomes
permanently fused to the surfaces of
asphaltene agglomerates. This accounts for
a large part of cracking susceptibility and also
impacts the ability of RAP to mix well with virgin
asphalt concrete (AC) at a molecular level.
Invigorate's solvency breaks apart these agglomerates,
and its chemical functionality
permanently binds to the oxidized sites. The
Invigorate-asphaltene complexes are more
compatible with the virgin AC and are stabilized
against reagglomeration, " explains Eric
Cochran, professor of chemical and biological
engineering at Iowa State. Produced from
soybean-oil feedstock, Invigorate is unique in
the marketplace in that it triggers chemical
reactions within the RAP, rather than acting
superficially, and is able to balance viscosity,
solvency and reactivity to aggressively
target oxidized asphaltenes, adds Cochran.
Invigorate's performance benefits mean that
mixtures incorporating as much as 50% RAP
can meet necessary specifications, greatly
improving upon current
industry-standard
mixtures of 20-25% RAP.
While the sustainability benefits of increasing
RAP content are clear, there are also
durability considerations at higher RAP levels,
says Dan Staebell, Colorbiotics' asphalt
business development manager. " Using RAP
is environmentally and economically smart,
but we have to be mindful of long-term durability
when increasing to higher levels near
50%. This can be achieved and confirmed
using the balanced-mix design approach.
Contractors and officials across the U.S. are
researching and understanding these tools
and implementing them to assist in specification
decisions, " says Staebell. Invigorate is
currently undergoing a number of field trials
across the U.S. wherein users have found
the asphalt mixtures with higher RAP content
very workable, even in colder conditions, according
to Staebell.
CHEMICAL ENGINEERING WWW.CHEMENGONLINE.COM
DECEMBER 2020
versity of Cologne and the
Fritz Haber Institute (Berlin,
both Germany) have used a
variety of tools to unveil this
mechanism, which was reported
last month in Nature.
TS-1 is a microporous,
crystalline material made up
of silicon and oxygen, with
small amounts of titanium.
Up to now, experts assumed
that the active center
in TS- 1 contains individual,
isolated titanium atoms.
Combining solid-state nuclear-magnetic
resonance
(NMR) studies with computer
modeling, the team
was able to show that two
neighboring titanium atoms
are required to explain the
catalytic activity, rather than
isolated Ti atoms.
The team believes the
findings will not only help to
improve existing catalysts,
but also to develop new
homogeneous and heterogeneous
catalysts.
MEMBRANES
Last month, Mann+Hummel
(Ludwigsburg, Germany;
www.mann-hummel.com)
expanded its Life Sciences
& Environment (LS&E) efforts
by investing in ZwitterCo
(Somerville, Mass.;
www.zwitterco.com), an
early-stage company developing
membranes for handling
waste streams heavily
contaminated with organic
materials. The investment,
through Mann+Hummel
Corporate Ventures, will
boost commercialization efforts
of this technology for
wastewater-treatment applications.
The strategic partnership
between the two
companies will be handled
through Microdyn-Nadir US,
Inc. (Goleta, Calif.; www.
microdyn-nadir.com), operating
as part of the LS&E
group within the Membrane
Solutions segment.
Earlier this year, ZwitterCo
started a two-year,
$1.25-million project
funded under the of the U.S.
Dept. of Energy's (DOE)
Water Security Grand Challenge.
That project aims to
demonstrate ZwitterCo's
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http://www.viaseparations.com http://www.mann-hummel.com http://www.zwitterco.com http://www.colorbiotics.com http://www.iastate.edu http://www.microdyn-nadir.com http://WWW.CHEMENGONLINE.COM
Chemical Engineering December 2020

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