Cheap, simple technique turns seawater into drinking water
Researchersfrom the University of Alexandria have developed a cheaper, simplerand potentially cleaner way to turn seawater into drinking water thanconventional methods.
Thiscould have a huge impact on rural areas of the Middle East and NorthAfrica, where access to clean water is a pressing issue if socialstability and economic development is to improve.
Rightnow, desalinating seawater is the only viable way to provide water togrowing populations, and large desalination plants are now a fact oflife in Egypt and other Middle Eastern countries.
Mostof these plants rely on a multi-step process based on reverseosmosis, which requires expensive infrastructure and large amounts ofelectricity. These plants release large quantities of highlyconcentrated salt water and other pollutants back into the seas andoceans as part of the desalination process, creating problems formarine environments.
That’swhy the race is on to find a cheaper, cleaner and moreenergy-efficient way of desalinating sea water.
Ina paper published last month in the journal, Water Science & Technology, researchers Mona Naim, Mahmoud Elewa, Ahmed El-Shafei and Abeer Moneer announced that they have developed a new way topurify sea water using materials that can be manufactured easily andcheaply in most countries, and a method that does not rely onelectricity.
Thetechnology uses a method of separating liquids and solids calledpervaporation. Pervaporation is a simple, two-step process – thefirst step involves filtering the liquid through a ceramic orpolymeric membrane, while the second step requires vaporizing andcollecting the condensed water. Pervaporation is faster, cleaner andmore energy efficient than conventional methods, not least becausethe heat required for the vaporization stage does not necessarilyhave to be electrically generated.
Pervaporationis not new – it has been in use for many years. But the membraneused in step one has been expensive and complicated to manufacture.
Thebreakthrough in this research is the invention of a newsalt-attracting membrane embedded with cellulose acetate powder foruse in step one of the pervaporation process. Cellulose acetatepowder is a fiber derived from wood pulp and is, according to theresearchers, cheap and easy to make in any laboratory.
Accordingto the paper, the membrane can quickly desalinate highly concentratedseawater and purify even badly contaminated seawater. It can also beused to capture pollutants and salt crystals to minimize pollution ofthe environment. The membrane can be used in very remote situationsusing fire to vaporize the water.
Theresearchers have yet to prove the commercial viability of theproduct, but if they can, it could be a promising alternative fordeveloping countries where water and electricity is a scarceresource.