Latest R&D trends in desalination by membrane technologies

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8 Water Today - The Magazine l June 2017

C O N T E N T S
Latest R&D Trends in
Desalination by Membrane
Technologies.......26
This article gives an overview of the most important
innovations that are being developed and implemented in
desalination of seawater or brackish water by
membrane technologies.
By Alfonso José García Laguna
Forward Osmosis – A Brief
Introduction....32
This paper outlines some of the aspects of the Forward Osmosis
process and its derivatives, with regard to key issues, concepts and
some applications.
By Peter G. Nicoll
Solar Energy for Water
Desalination.......52
This article discusses the different solutions to the most commonly
used desalination process (RO, MSF, MED), and solar energy
production technology compatible with desalination.
By Pascale Compain
Simultaneous Evaporation &
Condensation in Connected
Vessels.........60
The article discusses a new water desalination technology which
is less expensive in both capital and operating cost, simpler to
implement and more operationally flexible than conventional
thermal desalination technologies like low temperature thermal
desalination & mechanical vapour recompression.
By Amit Katyal
Antiscalants & Dispersants:
Potential Additives in
Desalination............82
The article discuses the use of antiscalants and dispersants
as the potential additives in Desalination process.
By Dr. Piyush Kumar Verma
Latest Advances &
Opportunities in Desalination
Technologies..........74
Desalination refers to the process by which pure water is
recovered from saline water by application of energy.
By Parimal Pajankar
Advanced Method to
Optimize Reverse Osmosis
Performance...................80
RO Membrane Management System is a predictive solution
that gives you the opportunity to improve membrane
efficiency and the predictability of failures.
By Soumitra Banerjee
Water Today - The Magazine l June 2017 9

Masthead ....................................8
Water Wire.................................14
Launch Pad................................18
Event Zone.................................20
Product Zone.............................24
Editorial Calendar......................99
Subscription Form....................108
Classifieds...............................109
Ad. Index..................................111
Editor’s Note.............................112
R
E
G
U
L
A
R
S
Geothermal Desalination
Potential for Clean &
Affordable New Water
Solutions.......88
By Leon Awerbuch
Desalination.................96
By Dr. M. Lakshmi Prabha & B. Darshan
Hydroflow Electronic Water
Conditioners Desalination
Application.....100
By Dr. Denzil Rodrigues
A Project Case Study:
They like it fast?
Do it Fast-track!...............104
By Amir Nassiri
C O N T E N T S

Latest R&D Trends in Desalination by
Membrane Technologies
This article gives an overview of the most important innovations that are being developed and implemented in
desalination of seawater or brackish water by membrane technologies.
By Alfonso José García Laguna
D
roughts, water scarcity and demographic increase
point to a uncertain future regarding the availability of
water resources where of the 1400 millions of cubic
kilometers of water on Earth, a few part of them of 200,000
cubic kilometers are fresh water available for human consumption
or for the use in the industry or irrigation according to the United
Nations. This situation together with the climate change make
foreseen a future where a very large portion of the fresh water
is not adequate for human consumption, industry and agriculture
due to an excess of salts or to the presence of pathogens
and pollution in general, so private companies and public
authorities have been making big efforts during the last years
in R&D to develop and improve technologies to generate
fresh water starting from salted and/or polluted waters as
raw material.
One of the most important of these technologies is the
desalination of seawater or brackish water by membrane
technologies and it has suffered very important innovations
in order to make it more accessible to all economies worldwide.
In this article we will have an overview of the most important
innovations that are being developed and implemented on this
technology.
2. The Nanomaterials Approach
The latest trends in Research, Development and Innovation
to evolve the desalination by membrane technology has been
developed based in the composition of the material of the
membrane itself in order to provide additional benefits and
improvements in performance, energy-efficiency, profits and
sustainability.
In these trends there have been an undisputed winners as
the application of nanomaterials, transforming the technical
complexity and operational cost, mainly energetic, into affordable
solutions technically and economically.
The development of nanomaterials is giving a wide spectrum
of possibilities to water desalination and purification. These
nanomaterials provides features as mechanical stability,
energy-effective permeation of water, modifiable pore size,
hydrophilic and hydrofobic interactions that are very useful
to improve the efficiency and cost of the desalination by
membrane technologies.
The desalination by membranes based in these nanomaterials are
expected brings a new concept of environmental friendly and
cost-effective technologies.
3. Other Approaches
But not only have been nanomaterials on this thrilling competition
for the development of the best membrane based desalination
process, we have had also very smart designs as the Centrifugal
Reverse Osmosis.
4. Applications of Nanomaterials
4.1 Application of Graphene in Desalination
Materials with pore sizes in the order of 1.0 nm have currently
a great potential for their use in desalination and separation by
membranes technologies.
Graphene is a material that was synthesized by first time in 2004
that is formed by a carbon mono-layer composed showing an

hexagonal net that has shown a rapid permeation of water in
recent experiments using graphene membranes.
In addition, theoretical models have predicted a significant higher
orders of magnitude in selectivity and permeability than current
desalination technology by reverse osmosis (RO).
These promising results have brought different proposals for
desalination using graphene membranes.
Porous graphene with a pore size of 13.4 Amstrong would be
the most efficient to allow the passage of the molecule of
H2O with a permeation energy of 0.04 eV. Also, this pore
would present permeation energies for the passage of Na+
and Cl- ions of 0.16 and 0.17 eV, respectively according to the
results of these experiments and modelizations.
This shows that the ions require a considerable higher
amount of energy to be able to pass through the pore, which
would allow their effective blocking and therefore a very
important decrease of the required energy compared with current
commercial RO membranes.
4.2 Sulfonated Graphene Oxide (SGO) in Seawater
Desalination Membranes
The synthesis of SGO (Sulfonated Graphene Oxide) are
obtained by chemical oxidation of natural graphite, surface
functionalization of the Graphene Oxide (GO) with sulfonating
agents and/or subsequent exfoliation (Figure 1).
Experimental results show that membranes developed by the
insertion of different quantities of SGO into a SPES (Sulfonated
Figure 1: Scheme For The Synthesis Of SGO And Preparation Of Composite SGO-SPES Membrane
Figure 2: Schematical representation of ED unit
Polyethersulfone) matrix have a significant better behaviour in
egnergy consumption for desalination.
Electrodialysis (ED) is a seawater desalination process based in
a differential potential applied between two electrodes where the
membranes are located between these aforementioned electrodes
(Figure 2).
ED is one of the most energy-effective seawater desalination
process of current application and due to this reason has been
selected to test the behavior of the composite membranes of
SGO-SPES composite membranes in different experiments.
The results of these experiments show that the water retention
and conductivity is increased as the content of SGO is increased
into the SPES matrix (Figure 3).

The chemical interaction between SGO and SPES and the
functionalities on the SGO leads to a SGO-SPES composite
membranes with a higher ionic conductivity and high water
retention and therefore the desalination performance is
enhanced keeping an excellent mechanical stability.
Figure 3: Desalination performance of different prepared membranes
with different SGO content: 0, 0.5, 1, 2, and 5 wt% for SPES, SGO-05,
SGO-1, SGO-2, and SGO-5 composite membranes respectively.
Figure 4: Structures Of Some CNT Membranes. Shown Are (A) Cross-
Sectional Scanning Electron Microscope (SEM) Image Of A Pristine CNT
Membrane; (B) CNT Based Water Filter With Cylindrical Geometry;
(C) Movement Of Water Molecules Through A CNT Channel; (D) SEM
Image Of Scattered Nacl Nanocrystals On CNT Membrane Surface;
(E) Movement Of Pure Water Molecules Through CNT-Membrane In
Osmotically Imbalanced Compartments, And (F) Engineered CNT
Membranes In Industrial Set Up.
It’s shown in the figure 3 that the Power Consumption is 16%
lower and Current Efficiency higher 15.2% compared to the
SPES membrane.
The high performance and excellent stability of the SPES-SGO
composite membranes makes them a very competitive solution
for seawater desalination.
4.3 Carbon Nanotube Membranes
Carbon Nanotubes (CNTs) are graphene sheets rolled in
cylindrical form (Fig.4 A/B) showing pore diameters up to 1.6 Å
and lengths of centimeters.
There are two types of CNTs, the Single-Walled Carbon
Nanotubes (SWCNTs) (Fig.4 B) and the Multi-Walled Carbon
Nanotubes (MWCNTs). The first ones are formed by a single
sheet of graphene and the second ones are formed by several
layers of graphene.
CNTs have been proved for water desalination and the results
have been almost incredible.
The advantages of the CNTs compared with the current RO
membranes are the removal of compounds that currently
complicate the desalination by RO and the retention of a wide
spectrum of pollutant compounds.
But the most important advantage of the CNTs is the energy-
efficiency showing a Energy Consumption negligible compared
with the current RO membranes.
This behavior is due to the almost absence of friction of the
water molecule when flows through the CNTs pores due to the
smooth hydrophobic walls of the CNTs cylinders walls.
CNT membranes have an enormous potential to substitute
the current RO, NF & UF Membranes (Figure 4). The
comparison between the CNTs membranes and the current
membranes for RO, NF, UF/MF is shown in the Table 1 & Figure 5.
The hydrophobic behavior of the walls of the CNTs hollow
cylinders make the water molecules movement doesn´t need any
additional driven-force through the hollow tubes.
These walls of the hollow cylinders of the CNTs are citotoxic
hence pathogens are killed and the biofouling is avoided without
any additional cost.

Another advantage of the CNTs is that they can be functionalized
in order to reject a particular pollutant or ion from water.
In addition CNT membranes are reusable, less complex, durable
and eco-friendly without the need of complicated chemical
transformations for their manufacturing.
Figure 5: Diagrammatic representation of major membrane
filtration methods.
pressure & can overcome the resistance of the membranes of the walls
& generate the osmosis. This entire process consumes a lot
of energy.
The example is that of two boxers, one stands and the other
comes, hits him with all his strength and makes him fall, but the
one who is going to receive the blow if he moves backwards
can dampen or dodge this one. On the other hand, when the
boxer is coming in with a blow and you also receive it, even
with little force you can knock him out.
In addition, the membranes have a high index of fouling that
forces to stop the production times to be cleaned. So it was
necessary to generate a self-cleaning process that would avoid
downtime and its impact on productivity and costs.
The static membrane consumes energy, but if the membrane
rotates helps because the flow passes through it at a lower
pressure. The filtration is carried out and the centrifugal force is
what gives most of the pressure necessary for filtration and, to a
lesser extent, the help of a low pressure pump.The competitive advantages of the CNT membranes compared
with the RO, NF, UF and MF membranes is shown very
detailed in the Table 1 and Figure 5.
As it’s shown on the table, CNT membranes shows high
achievements as water permeability, desalination capacity, solute
selectivity, robustness, antifouling, energy savings and scalability.
They can produce potable water instantly and can be used
as point of generation (POG) treatment and as point of use
(POU) treatment and all these arguments point to the CNT
membranes as the next generation in water desalination and
separation processes in general, opening a new field of research,
development and innovation.
However, the implementation of CNT membranes at commercial
scale as they are currently the RO membranes, needs to develop
further improvements to reach to a effective and homogeneous
synthesis of the CNT membranes.
5. Centrifugal Reverse Osmosis
The conventional osmosis process works from membranes,
which are made of polymeric products through which water passes and
thesolidsareretained.Itisafiltrationprocess,&inthecaseof conventional
reverse osmosis it is worked with a stopped or static membrane, so the
highpressurepumphastoexertalltheforcesothatthewaterhassufficient
Figure 5: Centrifugal Reverse Osmosis - Pilot Plant
Not using much energy, the emission of toxic products is less.
“Only the word high pressure and low pressure represents many
kilowatts and hours of consumption less.”
With this system the cost of water treatment would increase from
1.10 dollars to 82 cents, a saving of 25% per cubic meter.
Less favored areas, especially coastal areas, could have access to
fresh water.

Definition
Specific Application
Materials
Pore Types and Sizes
(nm)
Thickness (µm)
Water Permeability
(mPa-1 s-1)
Solute Rejection Ability
Self-cleaning Capability
Tunable Selectivity
Membrane Fouling
Operating Pressure
(barr)
It is an open tip single
hollow structure or
polymer composite
arranged perpendicularly
with impermeable filler
matrices.
Desalination and selective
removal of specific
pollutant from complex
mixtures.
CNTs and polymers in
VA and MM–CNT
membranes.
Micropores (0.1–2)
2 - 6
~7 × 10−7
Good
Capable with or without
functionalization.
Mixed matrix only
No
Negligible
Mixed matrix only
Yes
20 - 40
A process which applies
transmembrane pressure
to cause selective
movement of solvent
against the osmotic
pressure difference.
Desalination, water reuse
and ultrapure water
production.
Organic polymers such as,
polyamide, polysulfone
and polyether sulfone.
Micropores (0.3–0.6)
~0.1 - 0.2
~3 × 10−12
Good
Only with
functionalization.
Mixed matrix only
Yes
30 - 60
Mixedmatrix with ceramic
reactivity
Yes
1 - 10
Mixed matrix with
ceramic reactivity
Yes
<1.0
A separation process in
which particles and
dissolved macromolecules
smaller than 2 nm are
rejected.
Hardness, heavy metals,
and dissolved organic
matter removal.
Organic polymers like
polyamide, polyester and
other porous polymers.
Micropores (b2)
~0.05
~40 × 10−12
Good
Only with
functionalization
especially at ceramic
reactive membranes.
Only with
functionalization
especially
at ceramic reactive
membranes.
Only with
functionalization
especially at ceramic
reactive membrane.
A process whereby a
solution containing a
solute of N1–100 nm
in diameter is removed
from the solvent.
Virus and colloid removal.
Polysulfone, acrylic,
cellulose and others.
Mesopores (2–50)
150 - 300
~0.5 × 10−10
Moderate
A separation process in
which particles and
dissolved macromolecules
larger than 100 nm are
rejected.
Suspended solids,
protozoa,
and bacteria removal.
Polypropylene,
polysulfone,
polyurethane and so on.
Macropores (N50–500)
50 - 100
--
Poor
Feature CNT Membrane RO NF UF MF
Table1: Comparative Features Of Major Membrane Technologies
In addition, the centrifugal technology allows the self-
cleaning of the desalination plant, because the force generated
in the process expels of the system the sea water residues.
This eliminates the use of cleaning chemicals, which reduce
the useful life of the membranes and may even cause the system
to close.
In this system, water enters from the bottom up, through the
membranes that rotate through centrifugal revolutions, the fresh
water is filtered, the brine is rejected and both are stored in containers.
Sea water has approximately 35 grams of salts per liter, while the
waste water has 50 to 60 grams of salt per liter, which could be
problematic for the environment where it is deposited, whether
sea or land.
To avoid this, a post-treatment based on the practices of Europe
and the Middle East, which consists of constructing dual or
hybrid plants, has been designed, in which plant A may have waste
of raw material that is useful for plant B.
In the case of reverse osmosis, waste is the water of rejection that
has high levels of salts, but when using a plant where elements are
recoveredsuchasmagnesium,whichhasahighdemandinthemarket,
a dual plant is created where the generation of waste is avoided or
mitigated. This is one of the main proposals to avoid environmental
impacts.
6. Forward Osmosis: Current Status and
Perspectives
Despite the attention that has brought the FO during these
last years due to the potential to either reduce energy
consumption in wastewater treatment, water purification and
seawater desalination and production of energy from salinity-
gradient energy harvesting, the most important problems that

impeded the industrial implementation of this technology, as
the absence of an ideal draw solution with a high osmotic
pressure and with the possibility of being easily regenerated
effective thermodynamically to make it competitive with the
current energy effectiveness of desalination by RO and the lack of
a membrane that can produce a higher water flux, similar to RO
membranes have not still been overcome and it seems the progress
of this technology is a little stopped, at least at the moment.
7. Conclusions
We can conclude that the research, development and innovation
in the desalination by membrane technologies is following the
path of the new nanomaterials in order to reduce CAPEX, energy
costs and the OPEX in general associated to the desalination by
membranes with the current technologies in the market.
On the other hand the centrifugal reverse osmosis is showing
very promising results at pilot scale with a significant reduction in
energy consumption compared with traditional RO.
It seems that the future of the desalination by membrane
technologies is brilliant as a solution to obtain fresh water starting
from salted or polluted water, mainly because the development
of commercial CNT membranes seems to be not very far and the
same happens with the centrifugal reverse osmosis.
8. Bibliography & References
1. Application of Capacitive Deionization in water desalination:
A review Faisal A. AlMarzooqi , Amal A. Al Ghaferi Irfan
Saadat , Nidal Hilal
2. Quitarle la sal al agua del mar? Investigador mexicano obtuvo
patente por máquina desalinizadora. Tania Campos
3. Desalination and Membrane Technologies: Federal Research
and Adoption Issues Nicole T. Carter
4. An environmentally friendly process for the synthesis of
an FGO modified anion exchange membrane for electro-
membrane applications Prem P. Sharma, Swati Gahlot, Batuk
M. Bhil, Hariom Gupta, and Vaibhav Kulshrestha
5. Jorge Lechuga Andrade: desalinización sustentable del agua.
Marytere Narváez
6. Trends in desalination and water reuse. Filtration +
Separation
7. La tecnología centrífuga bajo el costo de la desalinización.
PROGRESO, Yucatán
8. Carbon nanotube membranes for water purification: A
bright future in water desalination. Rasel Das, Md. Eaqub
Ali, Sharifah Bee Abd Hamid, Seeram Ramakrishna, Zaira
Zaman Chowdhury
9. Jorge Lechuga Andrade: desalinización sustentable del agua.
Marytere Navarrez
10. Dramatic Improvement in Ionic Conductivity and Water
Desalination Efficiency of SGO Composite Membranes.
Swati Gahlot, Prem P. Sharma & Vaibhav Kulshrestha
11. Forward Osmosis: Current Status and Perspectives.
A Journal of Membrane Science Virtual Special Issue
Editors: Rong Wang, Laurentia Setiawan, Anthony G. Fane
Singapore Membrane Technology Centre, School of Civil
and Environmental Engineering, Nanyang Technological
University, Singapore
12. Desalinización de agua por membranas de grafeno nano-
poroso: Cálculos de primeros principios. Raúl Ignacio
Guerrero Avilés.
13. Nano-enabled membranes technology: Sustainable and
revolutionary solutions for membrane desalination?
P.S. Goh , A.F. Ismail, N. Hilal
14. History And Current Status Of Membrane Desalination
Processes. Ali M. El-Nashar
Alfonso José García Laguna has over 17 years’ experience,
most of them as Engineering Manager in the field of
Water Desalination and Wastewater Reuse working for top
companies in the sector, developing projects all around the world.
The last one has been the development as Engineering Manager of
the Design Engineering for the Sohar Seawater Desalination Plant
250MLD,fortheOPWP(TheOmanPowerandWaterProcurement
Company) located in Sohar (Oman), with a production capacity of
250,000 m3
/day and a budget of 250 MEUR.
Alfonso has a M.Sc. in Chemical Engineering & a B.Sc. in Industrial
Engineering. He has developed also his own engineering and
consultingcompanydedicatedtoDesalination,ReuseandWastewater
Projects called “Laguna Water Engineering” developing projects in
Sri Lanka, Spain and currently with some on-going projects in India.
He can be reached at ajglaguna@lagunawater.net
About The Author

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