Desalination study authors explore fabricated membrane

ocean
Credit: Tiago Fioreze / Wikipedia

Have scientists found a new way to purify sea water with materials that don't rely on electricity and are cheap enough to be manufactured in most countries? Might their work contribute to the search for a new, inexpensive water source?

The paper drawing interest among news sites is titled, "Desalination of simulated seawater by purge-air pervaporation using an innovative fabricated membrane." The authors, from Alexandria, Egypt, are Mona Naim, Mahmoud Elewa, Ahmed El-Shafei and Abeer Moneer. Their paper has been published in Water Science & Technology.

Al-Fanar Media said, "Moneer and a team of fellow researchers in Alexandria say they have created a new membrane that can extract more fresh water from the sea and improve the energy efficiency of doing so."

The authors said they invented an innovative polymeric membrane. It's described as a breakthrough; it involves the pervaporation process. They said It can desalinate simulated seawater of exceptionally high concentration to produce a high flux of potable water with over 99.7% salt rejection in a once-through purge-air pervaporation process.

There's nothing new about pervaporation, said Gizmag; the process "involves filtering the liquid through a ceramic or polymeric membrane," although the membrane used has been expensive and complicated to manufacture.

Digital Trends also said, "The method of pervaporation has been in use since the early 1990s." It is being used in wastewater treatment to separate organic solvents from industrial waste water.

Lynda Delacey in Gizmag said the importance of their work lies elsewhere than just pervaporation. "The breakthrough in this research is the invention of a new salt-attracting membrane embedded with cellulose acetate powder for use in step one of the pervaporation process. Cellulose acetate powder is a fiber derived from wood pulp and is, according to the researchers, cheap and easy to make in any laboratory."

What is more, the materials, can be mass produced in printed and cut sheets for widespread use, said Bryan Lufkin in Gizmodo.

The technology is based on membranes which contain cellulose acetate powder, produced in Egypt. The powder, in combination with other components, binds the salt particles as they pass through. The technique is being considered as useful for desalinating seawater.

Why is their study considered as important? Any attempt to find a method that is (1) not environmentally unsafe and (2) not too expensive to manage and maintain is obviously welcomed, at a time when planners look at how much of the planet's water is actually fit for drinking and farming.

"New ideas of water treatment methods are always welcome: Desalination is an expensive process that also uses a ton of energy: more than 200 million kilowatt hours per day around the world," said Gizmodo.

A 2013 UNDP report, "Water Governance in the Arab region," talks about managing water scarcity and securing the future. "Current projections show that by the year 2025 the water supply in the Arab region will be only 15 per cent of what it was in 1960."

The report commented on desalination: "Nonconventional water resources include desalination, treated wastewater, rainwater harvesting, cloud seeding and irrigation drainage water. The Arab region leads the world in desalination, with more than half of global desalination capacity. Desalinated water is expected to expand from 1.8 per cent of the region's water supply to an estimated 8.5 per cent by 2025."

The report pointed to the difficulties that desalination presented, as a process which is "energy- and capital-intensive," although technological advances have brought down production costs. "While desalination plants reduce pressure on conventional resources, they have harmful environmental effects, including pollution and greenhouse gas emission."

Quoted in Digital Trends: "Using pervaporation eliminates the need for that is used in classic desalination processes, thus cutting costs significantly," said Ahmed El-Shafei, one of the study authors.


Explore further

Egyptian method filters seawater in minutes

More information: Mona Naim et al. Desalination of simulated seawater by purge-air pervaporation using an innovative fabricated membrane, Water Science & Technology (2015). DOI: 10.2166/wst.2015.277

ABSTRACT
An innovative polymeric membrane has been invented, which presents a breakthrough in the field of desalination membranes. It can desalinate simulated seawater of exceptionally high concentration to produce a high flux of potable water with over 99.7% salt rejection (%SR) in a once-through purge-air pervaporation (PV) process. A set-up was constructed for conducting the desalination experiments and the effect of initial salt solution concentration (Ci) and pervaporation temperature (Tpv) on the water flux (J), %SR, separation factor, and pervaporation separation index were determined. The membrane was prepared by the phase-inversion technique, of a specially formulated casting solution consisting of five ingredients, after which the membrane was subjected to a post-treatment by which certain properties were conferred. The results confirmed that the salinity of the pervaporate was independent of Ci (all %SR above 99.7). The best result was at Tpv = 70 °C, where J varied from 5.97 to 3.45 l/m2 h for Ci = 40–140 g NaCl/l, respectively. The membrane morphology was confirmed to be asymmetric. The contact angle was immeasurable, indicating the membrane to be super-hydrophilic. Activation energies computed using Arrhenius law were, under all conditions investigated, less than 20 kJ/mol K.

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Nov 02, 2015
This is huge, if it becomes practical. Reverse Osmosis requires high pressures and energy, and if this works, it will give us very large savings for many industries.

We need all these advances for the 21st Century.

Nov 02, 2015
gkam, *ALL* filtration requires energy. The only question is how much. Energy is not a huge part of the bill. The real bill is for infrastructure construction and maintenance. Energy accounts for anywhere from three to ten percent of the total cost. Even if you were to cut that bill in half, it wouldn't have much effect on the total water bill.

And what becomes of the stuff the filter removes? Where do you put it?

It is interesting, but the real costs are elsewhere...

Nov 02, 2015
"Energy is not a huge part of the bill. "
-------------------------------

The relatively small commercial RO plants I saw used staged 50hp motors.

BTW, that wastewater is nasty. I suggest an evaporation and condensation area. The salts and clean water can be recovered.

Nov 03, 2015
The relatively small commercial RO plants I saw used staged 50hp motors.


You need a sense of scale. Distribution of water uses much larger pumps. 50 HP is nothing. We use multiple pumps with medium voltage motors with rated for thousands of horsepower --for a plain water filtration plant.

As I said, the real cost is maintenance, NOT energy. Do note that I speak from personal experience of having worked at a water utility for 30 years.

Nov 03, 2015
Did you work with RO? The systems of which I talked were small. You could not afford to do it for a municipality.

Nov 03, 2015
Yes, RO can take real energy. But how much savings would you get here versus how much does the infrastructure for the new process cost?

No, I really mean it. The infrastructure and the operations are the most expensive component and don't forget the bond interest on the infrastructure.

By the time you're done, the energy is less than a quarter of the bill. In our fresh water utility it's about 3% of the bill. Shave a bit off of the energy and the water bill overall won't move much. Why? Investment in infrastructure, staffing, new capital costs and so forth.

I'm not suggesting we shouldn't do anything, but there has to be a very compelling case to make such changes. People who wave their hands around and suggest this is trivial are fools. We'd happily take your money and you'll still wonder when those savings will happen...

Nov 03, 2015
@ Jacob. How you are podna? I am good me as usual. I am really revved up because Mrs-Ira-Skippette has finally given in and is going to let me put up a real tower behind the house. I found a 75 foot Rohn 45G for only 200 bucks, but I have to take him down and move him. I really am excited about it, because for starters I am going to be able to get a 10 meter three element beam I built up there (now it's only at the top of a 25 foot fiberglass light pole), and my 2 meter beam too. If all this works out and I feel ambitious me, I might try for 40 20 & 15 meter tri-bander the 45G will handle that no problems.

Oh yeah, I almost forget. I was able to get a clean sweep of the military convoy stations last month. I got every one of them from the boat at work.

Oh yeah, I almost forget again. Don't mind glam-Skippy. He likes to claim he is the Electronic Engineer and the Senior Engineer at the power company. He is not smart enough to realize when he runs into a real EE like you.

73's

Nov 03, 2015
"No, I really mean it. The infrastructure and the operations are the most expensive component and don't forget the bond interest on the infrastructure."
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I was not talking of inventing new infrastructure, I was speaking of adding desalination to an existing system.

Nov 03, 2015
" I found a 75 foot Rohn 45G for only 200 bucks,"
--------------------------------------
This is a thread pertaining to the desalination of water using new media.

Please take that CB "Breaker-breaker" stuff to the Truckers Site.

Nov 04, 2015
""""""""
" I found a 75 foot Rohn 45G for only 200 bucks,"
--------------------------------------
This is a thread pertaining to the desalination of water using new media.

Please take that CB "Breaker-breaker" stuff to the Truckers Site.
"""""""

Hooyeei, Cher you are the gift that just keeps on giving when it comes proving he does not anything about the things he claims to be the expert at.

glam-Skippy, for a super duper electronic battle designer who worked for Robert McNamara you sure don't know much about radio. Not even the most basic stuffs. You just can't pass up a chance to prove you are a phony pretender.

Oh yeah, I almost forget. I'll take anything I have to say anywhere I want to, if it is all the same to you. CB's and truckers,,, what a moron you are Cher.

Nov 04, 2015
Then, why aren't you on the ARRL high school forum?

This is a forum for desalination. Got salt in your crystal oven?

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