Water & Wastewater International

discovered that pores sized 0.8 nanometers need to be created in the material, thereby allowing water to pass but not salt. The challenge is making multiple small holes, in a controlled and uniform way across graphene without compromising strength.

In the Middle East, the Masdar Institute in Abu Dhabi has been experimenting with graphene to flter water without creating holes. Speaking to WWi magzaine earlier this year, Dr Steve Griffths said the institute has been layering graphene, to allow water fltration without the need to perforate the material.

Meanwhile, in February Australian SMEs Clean TeQ and Ionic Industries partnered with Monash University to scale up graphene fltration technology.

The research team won funding
through the Australian Government’s
Cooperative Research Centres Projects
program
While it has been expensive and
challenging to produce single layer
graphene using existing methods, such
as chemical vapour deposition, the
University of Manchester’s Dr Nair said
that graphene oxide “can be produced
by simple oxidation in the lab”.

Dr Nair added: “This is our frst
demonstration that we can control the
spacing [of pores in the membrane]
and that we can do desalination, which
was not possible before. The next step
is to compare this with state-of-the-art
material available on the market.”
Dr Graeme Pearce, principal at
Membrane Consultancy Associates
(MCA) told WWi magazine: “The
development at the University
of Manchester aims to produce a
membrane with a highly controlled
character, free from defects. Given the
materials used, longevity should also
be good. The challenge will be whether
the membrane can be effectively used
with the current form factor (the spiral
wound element mounted in series in
long pressure vessels) and using current
process design concepts.

“Alternatively, the membrane might
be better exploited by a completely
different approach to process design,
which would be high risk and slow
to introduce, but might have a much
greater long term impact if the
improved membrane can be exploited
more effciently.”
He said: “The key issue would be
to demonstrate both performance and
longevity in the frst instance and then
establish what features of the current
approach to desalination plants limit
the benefts of a new membrane and
what can be done to remove these
impediments.”
Elsewhere in the UK, G2O is
commercialising a development from the
University of South Carolina in which a
graphene oxide coating is applied to an
existing polymeric membrane.

Commenting on this development,
Pearce added: “This preserves the
form factor and should be more
easily adopted by the industry. The
development is still early stage and the
longevity of the coating has yet to be
established, but the approach appears
to be promising and initial results on
performance enhancement have been
encouraging. This is more likely to
allow a radical optimization of existing
practice rather than the potentially
more revolutionary but higher risk
development from Manchester.”
Many sources have pointed to the
graphene development as being the
answer to cheaper and more energy
effcient desalination globally, yet the
material is still at an extremely early
stage. The real test will be scaling up the
graphene oxide, comparing it to new,
polymeric membranes when treating
seawater and addressing how resistant
it is to biofouling.