How about efficient seawater desalination? Lots of water at a low price
Access to clean, safe drinking water is a need that is unfortunately poorly met in many parts of the world. Seawater desalination would be of great help in many regions of the world, if, of course, methods were available that were adequately efficient and within reasonable economy.
New hope for the development of cost-effective ways to obtain fresh water by removing sea salt appeared last year when researchers reported the results of studies using type material organometallic skeleton (MOF) for sea water filtration. The new method, developed by a team at Australia's Monash University, requires significantly less energy than other methods, the researchers said.
MOF organometallic skeletons are highly porous materials with a large surface area. Large work surfaces rolled into small volumes are great for filtration, i.e. capturing particles and particles in liquid (1). The new type of MOF is called PSP-MIL-53 used to trap salt and pollutants in sea water. Placed in water, it selectively retains ions and impurities on its surface. Within 30 minutes, MOF was able to reduce the total dissolved solids (TDS) of the water from 2,233 ppm (ppm) to below 500 ppm. This is clearly below the 600 ppm threshold recommended by the World Health Organization for safe drinking water.
1. Visualization of the operation of an organometallic membrane during seawater desalination.
Using this technique, the researchers were able to produce up to 139,5 liters of fresh water per kilogram of MOF material per day. Once the MOF network is “filled up” with particles, it can be quickly and easily cleaned up for reuse. To do this, it is placed in sunlight, which releases the trapped salts in just four minutes.
“Thermal evaporative desalination processes are energy intensive, while other technologies such as reverse osmosis (2), they have many drawbacks, including high consumption of energy and chemicals for membrane cleaning and dechlorination,” explains Huanting Wang, research team leader at Monash. “Sunlight is the most abundant and renewable source of energy on earth. Our new adsorbent-based desalination process and the use of sunlight for regeneration provide an energy-saving and environmentally friendly desalination solution.”
2. Osmosis seawater desalination system in Saudi Arabia.
From graphene to smart chemistry
In recent years, many new ideas have emerged for energy efficient seawater desalination. "Young Technician" closely monitors the development of these techniques.
We wrote, among other things, about the idea of the Americans at Austin University and the Germans at Marburg University, which to use a small chip from a material through which an electric current of negligible voltage (0,3 volts) flows. In salt water flowing inside the channel of the device, chlorine ions are partially neutralized and formed electric fieldas in chemical cells. The effect is that the salt flows in one direction and the fresh water in the other. Isolation happens fresh water.
British scientists from the University of Manchester, led by Rahul Nairi, created a graphene-based sieve in 2017 to effectively remove salt from seawater.
In a study published in the journal Nature Nanotechnology, scientists argued that it could be used to create desalination membranes. graphene oxide, instead of hard-to-find and expensive pure graphene. Single layer graphene needs to be drilled into small holes to make it permeable. If the hole size is larger than 1 nm, the salts will freely pass through the hole, so the holes to be drilled must be smaller. At the same time, studies have shown that graphene oxide membranes increase thickness and porosity when immersed in water. Doctor team. Nairi showed that coating the membrane with graphene oxide with an additional layer of epoxy resin increased the effectiveness of the barrier. Water molecules can pass through the membrane, but sodium chloride cannot.
A group of Saudi Arabian researchers have developed a device they believe will effectively transform a power plant from a "consumer" of water into a "producer of fresh water". Scientists published a paper describing this in Nature a few years ago. new solar technologywhich can desalinate water and produce at the same time electricity.
In the built prototype, scientists installed a watermaker in the back. solar battery. In sunlight, the cell generates electricity and releases heat. Instead of losing this heat to the atmosphere, the device directs this energy to a plant that uses the heat as an energy source for the desalination process.
The researchers introduced salt water and water containing heavy metal impurities such as lead, copper and magnesium into the distiller. The device turned water into steam, which then passed through a plastic membrane that filtered out salt and debris. The result of this process is pure drinking water that meets the safety standards of the World Health Organization. The scientists said the prototype, about a meter wide, could produce 1,7 liters of clean water per hour. The ideal place for such a device is in a dry or semi-dry climate, near a water source.
Guihua Yu, a materials scientist at Austin State University, Texas, and his teammates proposed in 2019 effectively filtering seawater hydrogels, polymer blendswhich create a porous, water-absorbing structure. Yu and his colleagues created a gel sponge out of two polymers: one is a water-binding polymer called polyvinyl alcohol (PVA) and the other is a light absorbent called polypyrrole (PPy). They blended a third polymer called chitosan, which also has a strong attraction to water. Scientists reported in Science Advances that they have achieved pure water production of 3,6 liters per hour per square meter of cell surface, which is the highest ever recorded and about twelve times better than what is produced today in commercial versions. .
Despite the enthusiasm of scientists, it is not heard that new ultra-efficient and economical methods of desalination using new materials will find wider commercial application. Until that happens, be careful.
