Chemical Engineering March 2011 - 15

Graphene improves the performance of water deionization
CHEMENTATOR
research team from the University of
South Australia (Adelaide; www.unisa.
edu.au) and the East China Normal University
(Shanghai; www.ecnu.edu.cn) has developed
a capacitive deionization technology
(CDI) that uses graphene-like nanoflakes as
electrodes, instead of conventionally used
activated carbon (AC) materials. The team
claims that the graphene-based electrodes
offer better performance than conventional
CDI systems that use AC electrodes.
In CDI, water flows between pairs of
electrodes held at a potential difference
of 1-2 V. The negative electrode attracts
and holds positively charged ions such as
calcium, magnesium and sodium, while
the positively charged electrode attracts
and holds negative ions such as chloride,
nitrate and silica. When the electrodes
become saturated, the applied potential
is removed, and the ions are released and
flushed out. For each gallon of brackish
water fed to the process, more than 80%
emerges as fresh, deionized potable water.
A
Compared to alternative desalination
methods, CDI does not generate secondary
pollution, and is cost-effective and energy
efficient because it aims to remove only the
salt ions, which are a small percentage of
the feed solution.
" Although having a larger surface area
(989.54 m2/g) than graphene nanoflakes
(222.01 m2/g), AC has a much lower electrosorptive
capacity, 13.73 µmol/g, compared
with 23.18 µmol/g for graphene nanoflakes, "
says team member Linda Zou of the University
of South Australia. The team believes
graphene nanoflakes have a larger effective
surface area than that of AC because the
nanoflakes have an interlayer surface that
is more accessible to ions, while AC has a
large fraction of inaccessible micropores.
Another possible reason for the high conductivity
of graphene nanoflakes, the team believes,
is the presence of conductive graphitized
chunks in the nanoflakes, caused by
the incomplete graphene preparation from
the graphite precursor.
(Continued from p. 12)
collaboration of BASF SE
(Ludwigshafen, Germany;
www.basf.com), JGC Corp.
(Yokohama; www.jgc.co.jp)
and Inpex Corp. (Tokyo, both
Japan; www.inpex.co.jp). The
tests - carried out at Inpes's
Koshijihara natural-gas plant in
Nagaoka city - demonstrated
the performance of the new
gas-treatment process, which
is said to enable a 25-35%
reduction in the cost of CO2
recovery and compression. The
HiPact Process (high-pressure,
acid-gas capture technology)
is a joint development of BASF
and JGC.
Heat transfer by wire
Scientists at Fractal Antenna
Systems Inc. (Waltham, Mass.;
www.fractenna.com) have demonstrated
a new method of heat
transfer based on a complex
pattern of fractals built into an
infrared (IR) resonator. Fractal
(Continues on p. 16)
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Circle 2 on p. 62 or go to adlinks.che.com/35063-02
14 CHEMICAL ENGINEERING WWW.CHE.COM MARCH 2011
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http://www.basf.com http://www.jgc.co.jp http://www.unisa http://www.edu.au http://www.inpex.co.jp http://www.ecnu.edu.cn http://www.fractenna.com http://www.aggreko.com/northamerica http://adlinks.che.com/35063-02 http://WWW.CHE.COM
Chemical Engineering March 2011

Table of Contents for the Digital Edition of Chemical Engineering March 2011
