Chemical Engineering June 2022 - 6

edu.sg) have found a
way to create biocement
from two common waste
materials - industrial
carbide sludge (a waste
product of acetylene
production) and urea
(from urine).
To make the biocement,
carbide sludge is
first treated with an acid
to produce soluble calcium.
Urea is then added
to the soluble calcium to
form a cementation solution.
A bacterial culture
is then added and the
bacteria break down the
urea into carbonate ions,
which
react
with
the
soluble calcium ions in a
process called microbially
induced calcite precipitation
(MICP). When
this reaction occurs in
soil or sand, the resulting
calcium carbonate
generated bonds soil
or sand particles together
to increase their
strength, and fills
the
pores between them to
reduce water seepage
through the material.
The same process can
also be used on rock
joints, which allows for
the repair of rock carvings
and statues.
The soil reinforced with
biocement has an unconfined
compression
strength
of up to 1.7 MPa,
which is higher than that
of the same soil treated
using an equivalent
amount of cement.
The proof-of-concept
research was described
in a recent issue of the
Journal of Environmental
Chemical Engineering.
BIOFUEL
Researchers from the
University of Agder (UiA;
Kristiansand,
Norway)
and the University of
Jaffna (Sri Lanka; www.
jfn.ac.lk) are collaborating
to develop a more
environmentally
friendly
transportation fuel in
Sri Lanka. The biofuel
- made from bioethanol
and castor oil - is
suitable for the engines
used in the three-wheeler
(Continues on p. 8)
6
CHEMICAL ENGINEERING WWW.CHEMENGONLINE.COM
JUNE 2022
Scaleup project for
simultaneous carbon capture and conversion
A
multidisciplinary project to scale
up a system capable of simultaneously
capturing carbon dioxide
from fluegas and converting it to
ethanol has received $1.9 million from the
U.S. Department of Energy's Advanced Research
Projects Agency-Energy (ARPA-E;
Washington, D.C.; arpa-e.energy.gov). The
electrochemical capture-and-conversion
process has been proven in a laboratory
system designed by Mohammad Asadi,
assistant professor at the Illinois Institute
of Technology (IIT; Chicago; www.iit.edu)
and has the potential to lower the cost of
carbon capture to less than $40 per ton
of CO2 (compared to the $60-100 per-ton
cost observed today).
To accomplish the one-step capture and
conversion, Asadi's laboratory synthesized
a catalyst consisting of transition-metals
specially functionalized with organic ligands.
" We are unifying two problems -
capturing CO2 and converting it to useful
chemicals - into one system, " Asadi says.
The bifunctional material is able to address
a number of recalcitrant scientific and engineering
challenges, including the masstransport
challenge of bringing CO2 molecules
to a surface, and the thermodynamic
challenge of reducing CO2 while also forming
a carbon-carbon bond.
To address the mass transport issue, the
nanostructured surface sets up a CO2 gradient
to hasten the diffusion of CO2 to the reaction
surface, where the local environment
makes an ethanol-forming electrochemical
reaction favorable, Asadi explains.
A multidisciplinary team is now assembled
to study the economic feasibility and lifecycle
costs of a scaled-up version of the simultaneous
capture-and-conversion
system.
Scaling
up the prototype will involve assembling
stacks of the electrochemical systems
containing the catalyst material, Asadi notes.
Recycling bauxite residues and electrowinning iron
Electrochem Technologies
E
lectrochem
Technol ogies
& Materials
Inc.
(Montreal,
Canada;
www.electrochemtechnologies.com)
produced
pure
electrolytic iron
(99.995% Fe) using
its patented FerWIN
process (diagram) -
a sustainable zerocarbon
iron-making
technology - from ferrous sulfate heptahydrate
(copperas) originating from the sulfation
of bauxite residues. This pilot test work
involved reacting concentrated sulfuric acid
with bauxite residues, from which iron, aluminum
and sodium sulfates, along with gypsum,
are recovered. Then, the electrowinning of
iron metal was performed on the crystallized
copperas. Pure electrolytic iron flakes were
electrowon inside a rectangular electrolyzer
with 10 ft2 of cathodes, while regenerating the
concentrated sulfuric acid to be recycled upstream
during sulfation.
" Based on the excellent faradic current efficiency
(98%), low specific-energy consumption
(2.9 kWh/kg Fe) and operating expenditures
($315/m.t. of Fe), we are optimistic that combining
the sulfation of bauxite residues and the
electrowinning of iron could represent a possible
route for neutralizing, dewatering, recycling
and valorizing red mud and bauxite residues, "
says Francois Cardarelli, president of Electrochem
Technologies & Materials. " This is particularly
true in locations having an oversupply
of sulfuric acid from nearby smelters and affordable
nuclear power or hydroelectricity, " he says.
From an environmental standpoint, the
FerWIN process also releases pure oxygen
gas to the atmosphere generating carbon
tax credits. The patented technology is now
granted and enforced in 16 key jurisdictions
(within Canada, China, Japan, South Africa,
Europe, Brazil and India) where red-mud
landfills represent a serious environmental
hazard. As the technology is now technically
proven, de-risked, and the costs and
benefits analysis favorable, the company is
currently seeking to secure licensing agreements
for the FerWIN process across the
aluminum industry, Cardarelli says.
http://www.ntu.edu.sg http://www.electrotechnologies.com http://www.electrotechnologies.com http://arpa-e.energy.gov http://www.iit.edu http://www.jfn.ac.lk/ http://www.jfn.ac.lk/ http://WWW.CHEMENGONLINE.COM
Chemical Engineering June 2022

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