Chemical Engineering January 2017 - 8

COLD OIL SPILLS
Researchers at the U.S. Dept.
of Energy's Pacific Northwest
National Laboratory (PNNL;
Richland, Wash.; www.pnnl.
gov) have chemically modified
sawdust to make it exceptionally
oil-attracting and buoyant
- characteristics that are
ideal for cleaning up oil spills
in Arctic waters. The nontoxic
material absorbs up to five
times its weight in oil and stays
afloat for at least four months.
" Most of today's oil-remediation
materials are designed for
warm water use, " says PNNL
microbiologist George Bonheyo,
who leads the modified
sawdust's development from
PNNL's Marine Sciences Laboratory.
Beyond absorbing oil,
it also enhances another approach
to combatting oil spills
- controlled burns. If changing
weather or tides move
spilled oil toward a sensitive
area fast, oil can be burned
before it can cause further
harm. Called in-situ burning,
the practice can significantly
reduce the amount of oil in
water and minimize its adverse
environmental effects.
To modify the sawdust, researchers
chemically attach
components of vegetable oil
onto the material's surface,
making it hydrophobic. The
final product is a light, fluffy,
bleached powder. The team is
also trying out adding tiny, oileating
microbes - fungi and
bacteria - to the powder's
surface so any left-behind
material could naturally break
down oil over time.
NEW CATALYST
Haldor Topsøe A/S (Lyngby,
Denmark; www.topsoe.com)
has introduced a second-generation
HyBRIM catalyst, which
is said to boost profitability of
diesel and hydrocracking units
at petroleum refineries. Refiners
can achieve longer cycle
lengths, high-value products
from low-quality feedstocks
and increased volume swell
with the latest HyBRIM nickelmolybdenum
catalyst, with
25% improved activity for both
nitrogen and sulfur removal,
says the company.
Successor to TK-609 of the
(Continues on p. 10)
8
Paint a thermoelectric device onto any shaped
surface to recover waste heat
S
cientists from
Ulsan National
Institute of Science
and TechA
B
C
UNIST
nology
(UNIST; Ulsan,
South Korea; www.unist.
ac.kr), led by Prof Jae
Sung Son, have succeeded
in producing
high-performance, solid-state thermoelectric
(TE) materials with liquid-like properties that
can be easily brush-painted on surfaces of
almost any shape.
The thermoelectric effect is the direct conversion
of temperature differences to electric
voltage and vice versa. This phenomenon
can be used for heating or cooling, and for
waste-heat-recovery systems. The output
power of thermoelectric generators depends
both on the inherent properties of the TE material
and on the engineering of the device to
minimize heat losses.
The power generating efficiency of solidstate
TE devices can be estimated from a dimensionless
parameter, ZT = S2sT/k, where
S is the Seebeck coefficient, s is the electrical
conductivity, k is the thermal conductivity
and T is the temperature). In real-world applications,
the minimization of heat loss due
to incomplete contact between the surface
of the heat source and the TE module is no
Conventional TE device
Substrate
Electrode
Conventional TE device on
a curved heat source
Painted TE device on a
curved heat source
less important than the TE material's powergenerating
efficiency.
In response to that challenge, the scientists
developed a shape-engineerable TE painting
(diagram, C) that prevents that heat loss suffered
by conventional planar TE devices (diagram,
A and B). They achieved this by using
a molecule-level sintering process, which is
described in detail in a recent issue of Nature
Communications. They used the molecular
Sb2Te3-based chalcogenidometalate (ChaM)
for n-type BiTeSe and p-type BiSbTe TE particles.
Optimizing the process, they achieved
the ZT values of 1.21 for p-type and 0.67 for
n-type TE materials. They fabricated TE generators
by applying TE paint on flat, curved
or large-sized hemispherical substrates, followed
by sintering at temperatures above
350°C. The process is said to be the most effective
means of heat-energy collection from
any heat source, and the output power density
(4.0 mW/cm2) is the best value among
the reported printed TE generators.
An inexpensive adsorbant for removing
silver from wastewater
T
he release
of
silver
from industrial
wastewater has caused serious
environmental problems. Many
methods have been developed to
remove silver ions from industrial wastewater,
including
chemical
precipitation,
ion
exchange, electrolysis, replacement,
membrane and reverse osmosis. Several
adsorbents have been used to remove
and recover silver from aqueous solutions
or industrial wastewater. However, those
adsorbents are expensive, and lately many
low-cost materials have been tried, including
waste wool, peanut shells, crab shells,
soybean hulls and cotton. Now, a group
from Gangneung-Wonju National University
(Gangneung, South Korea; www.gwnu.
ac.kr) led by professor Choong Jeon, has
used recycled waste coffee grounds to remove
silver from industrial wastewater directly
as a zero-cost adsorbent.
From the Fourier-transform infrared (FTIR)
spectra analysis, the group found that the
waste coffee grounds - which have a porous
and homogeneous structure and are
composed mainly of carbon (61.60%) and
oxygen (38.40%) - have functional groups
like COO- and OH-, which play an important
role in Ag+ adsorption. The existence of Ag+
on the adsorbent was confirmed by scanning
electron microscope (SEM) images and
energy-dispersive x-ray (EDX) spectroscopy
analysis. The highest adsorption capacity
(46.2 mg/g) and removal efficiency (92.4%)
were achieved at pH of 6. The adsorbed
amount of silver ions decreased slightly with
increasing temperature in the range of 15
to 45°C. Most of the adsorption was completed
within 60 min.
The group believes the adsorption process
using waste coffee grounds can be applied
to the adsorption and recovery of silver ions
in industrial wastewater-treatment systems,
and that the process could replace conventional
treatment processes, such as solvent
extraction and ion-exchange resin.
CHEMICAL ENGINEERING WWW.CHEMENGONLINE.COM
JANUARY 2017
http://www.pnnl http://www.unist http://www.ac.kr http://www.topsoe.com http://www.gwnu http://www.ac.kr http://WWW.CHEMENGONLINE.COM
Chemical Engineering January 2017

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