Making Seawater Easier to Swallow
Researchers in the United States and Korea have developed a membrane, thereby reducing the cost of filtration salt from salt water. The new polysulfone-based material is resistant to chlorine treatment – removing the need for certain steps costly desalination treatment.
The most common desalination process, reverse osmosis, forces seawater through semi-permeable membranes to filter out salt. Although much energy is required to run large desalination plants, they increase the supply of fresh water – and the world more than 1 billion people lack access to clean water and clean.
A shortcoming of desalination membranes is that over time they can be blocked by the growth of algae or bacteria in biofilms. Adding chlorine to kill micro-organisms in the water – but also destroys polyamide-based membranes. Thus, chlorine is generally removed from the water before they cross the membrane, and then resumed later.
The new membrane, based on a polysulfone backbone to make promises that a complex procedure and unnecessarily costly. “Polysulfone better chlorine resistance than polyamides, as well as its main chain aromatic rings and solid carbon, sulfur and oxygen has been committed,” said Ho Bum Park, a team led by University of ‘Ulsan, South Korea. “Therefore it is not contained amide bonds that are susceptible to attack by aqueous chlorine.”
Polysulfones have been used for desalination, but the water does not flow very well about it. This has been corrected by a change in how the polymers are said Benny Freeman, another team led by University of Texas at Austin. “Previously, the hydrophilic sulfone groups were added to the polymer after polymerisation – which has sites in the least stable. Instead, we have included these groups in the monomer, so that it enters directly into the polymerization integrated into the structure. “
The new polymer has been patented by the team and Freeman expects to find commercial uses in the three years of startup.
‘Highly chlorine resistant membranes could remove costly process steps and increase the lifetime of the membranes used in desalination, “said Ian Lomax, Major Projects Manager at Solutions Dow Water.
Natural Solution
But much more work is necessary if the membrane desalination is to solve the global water shortage. Thank you to the power needed to push water against the concentration gradient in the reverse osmosis membrane is greater in the desalination plants based is too expensive for many developing countries. (Most existing desalination plants are built near coastal power plants, the use of excess energy and waste heat). For richer countries, the benefits of desalination should be weighed to emissions from fossil fuels to energy-hungry, inefficient processes.
Improving efficiency membrane is the key to reducing the cost of desalination and the impact of fossil fuels, “said Thomas Mayer, who works at Sandia National Laboratories in Albuquerque, USA. “The membranes of human kidney using, for example, salt filters about 100 times more effective than synthetic membranes,” he said. “If we repeat, it would be very effective.”
When the membrane efficiency is quite good, might membranes in desalination systems powered human filtering, such as integrating the “LifeStraw” developed by Vestergaard Frandsen. This simple device contains a membrane filter micro-organisms in water and working on the power of the undertow of man – if the company said a spokesman Chemistry World, it was not made for develop a straw desalination in the immediate future.
Currently, reverse osmosis systems are the most effective means of implementing large-scale desalination, but improvements are also due to the effectiveness of other technologies such as thermal distillation or evaporation process, adds Dow Lomax, membrane processes have competition.
