Comprehensive coverage

Desalination, the nanorobot version

Futuristic water purification? An Israeli company is developing a new desalination method in which nano-robots will clean seawater of problematic salts; This, without removing from them substances that are important for our health

By Yonatan Sher - Angle of a news agency for science and the environment

When you hear the word "robot", what do you think of? Most of us probably imagine a shiny, powerful metal figure that can lift cars or bend thick steel bars with frightening ease. But in recent years it has become clear to us that robots are quite diverse devices: some are powerful and some are extremely smart, some are very large and some are tiny - the size of a thousand hairs. What can such a small robot already do? to stick to individual molecules and "swing" them from one side of the tank to the other side to precipitate drinking water.

Maybe this scene sounds to you like it's taken from a science fiction movie, but in fact it's already happening nowadays, in the nanorobot kingdom of The Israeli start-up NWPT - The company that develops an unusual desalination method, which uses nano-robots that remove salts from the water in a way that does not remove substances that are essential to us.

Is salt good for health?

Almost every Israeli knows that we are good at desalination: our small country is a leader in desalination technologies and capabilities, and uses five facilities spread along the Mediterranean Sea - which produce over 600 million cubic meters of desalinated water, which make up about 75 percent of our drinking water consumption.

With these data, you may be asking yourself - what is wrong with the way we pray water today? So it turns out that the method used in these factories, reverse osmosis (RO) - which uses a system of filtering membranes and high pressure pumps that push water through them to remove almost 100 percent of the salts from the water - is problematic for several main reasons.

First, the pump system in question requires a lot of energy to operate: the amount of electricity that is currently consumed in our desalination processes stands at About 3.5 kilowatt-hours (kWh) for every cubic meter of water. To illustrate, in 2015, about 4 percent of all electricity produced in Israel was used for desalination purposes. Since this is electricity that comes mainly from the burning of fossil fuels (natural gas) - the environmental price we pay for these desalinations is quite heavy.

The second disadvantage of the current method lies precisely in its great success. What do you mean? The reverse osmosis excels in the Ha-Kheeding in all that has to do with the removal of salts. But, we don't need this maximum excellence, because some of these salts are actually important for us. Yes, salt is not only the white spice that we generously sprinkle when falling in love: In chemistry, the nickname "salt" It can be given to any substance that consists of ions with a positive electrical charge, which are bound to ions with a negative electrical charge - so the salts found in seawater also include substances such as chlorine, sulfate and magnesium, some of which are essential for our health.

Indeed, in the last decade it has gradually developed Awareness in research The health disadvantages of consuming desalinated water are completely free of magnesium. Various studies have indicated that a lack of magnesium may cause symptoms of fatigue, lack of appetite, nausea and vomiting, and in severe cases trigger muscle contractions, lead to disturbances in mood and concentration and increase the risk of heart diseasefor diabetes and possibly colon cancer as well.

fight molecules with molecules

Yaron Wirtzer, co-founder of the start-up NWPT, says that the motivation for its establishment was an article in the media about the health damage caused by desalinated water in Israel. Therefore, the company's initial idea was to find a way to remove only the harmful salt from seawater. "I looked for all kinds of research on the subject and in the end I came to the conclusion that the solution should be at the molecular level of nanotechnology," Wirzer says. We all know what "technology" is, but what is "nano"? One nanometer is equal to one billionth of a meter - the size of a single molecule; For comparison, the width of a human hair is 100-80 thousand nanometers. That is, nanotechnology includes developments on these tiny scales.

Equipped with an idea for a nano-robot that is inside a dedicated facility that contains an electromagnet (a magnet that operates through an electric current) - Wirzer went looking for partners for the project, who knew how to create reality from fantasy. After many meetings with various experts who claimed that his idea was equivalent to science fiction - Wirzer reached Dr. Vladimir Kogan, who, although he changed the original design of the development, but also managed to create the long-awaited nanorobot with a size of about 80 nanometers. The final structure, on which the company issued a patent - includes a capturing unit that resembles a hoop and knows how to capture sodium molecules, which together with chlorine constitutes about 90 percent from the sailors in the sea water; I mean, this is a type of salt that we should really know how to get it out of the water with maximum efficiency.

The company's initial idea was to find a way to remove only the harmful salt from seawater. The NWPT imaging facility: NWPT
The company's initial idea was to find a way to remove only the harmful salt from seawater. The NWPT imaging facility: NWPT

According to Wirzer, although there are already similar nanorobots in the world that know how to capture individual sodium molecules - but here it is a development with a unique element: the mechanism that allows the nanorobots to release (and "take out") the various substances they capture, which uses ultraviolet lighting . "After years of trial and error, in July 2020 we succeeded for the first time in creating a nano-robot that captures sodium and also releases it," he says. "When you shine an ultraviolet light on it - it releases the sodium, and when you stop shining - it catches it." The process is very fast (on the order of seconds), and can also work forever, without a decrease in efficiency.

In addition to the health advantage of leaving magnesium in the desalinated water, Wirzer claims that in the future the company's desalination method will be able to save energy and prevent pollution: according to him, the method may save about 90 percent of the energy currently required to operate the pumps of the reverse osmosis method, and prevent the pollution of the sea caused by the use of chemicals that clean the membranes (in the current method) and the pollution created as a result of throwing away the membrane filters (whose lifespan is relatively short). In addition, according to Wirzer, the method in question may greatly reduce manpower expenses for maintenance - and finally lead to savings of about 80 percent of desalination costs.

Moreover, while the efficiency of the reverse osmosis method is up to 50 percent (the other 50 percent is brine - water in which all the salts removed in the process are concentrated) - Wirzer claims that with the new method it is possible to achieve an efficiency of about 80 percent in the production of desalinated water from pumped seawater.

Hello, how much for a kilo nanorobot?

The last component of a nano-robot, which, as mentioned, has a total size of about one thousandth of a hair, is a magnetic nano-particle - a kind of small magnet that allows you to control the position of the tiny robots and concentrate them in one point. To understand the importance of this part, one has to examine the prototype mechanism of the desalination plant that the company built in the laboratory.

The system diagram. Illustration by Ran Levy RNLV-Design
The system diagram. Illustration by Ran Levy RNLV-Design

At this stage, it is a container that contains 30 grams of nanorobots, into which 2 liters of saline water (with a reduced sodium concentration) are injected; By mixing them in the container, the nanorobots reach the sodium molecules quickly. After that, activation of a magnet at the bottom of the tank concentrates all the nanorobots (along with the sodium they captured) at the bottom, so that water with a low salt concentration remains in the upper part - the water that is pumped out, and in the future (when the experiment leaves the laboratory) is supposed to become fresh water. After this pumping, ultraviolet light shines on the nanorobots, and they release the sodium they captured - into the water that remains at the bottom of the tank. In the last step, the salty water is pumped from the bottom of the tank, the magnet releases the nanorobots back - and the process, which only takes a few minutes, can start again.

In a demonstration in the laboratory, the company was able to lower about 10 percent of the electrical conductivity (a way to measure the amount of salts in the water) of 2 liters of salt water - a figure that, according to the company, proves that the nanorobots succeeded in their mission. According to them, the thing that limits the desalination ability of the method is the amount of nanorobots they used. According to them, the prototype consists of only 30 grams of nanorobots because this is the amount they have been able to produce so far, due to the cost of the manufacturing process and the length of time it requires.

Small robots, big benefits?

So, science fiction or not science fiction? "After the company builds a larger pilot, using sea water - it will be possible to test the effectiveness of the development," says Dr. Adi Levy, head of the master's degree program in urban and rural sustainability at Ahva Academic College and a member of the executive committee of The Israeli Association for Ecology and Environmental Sciences. "There are many questions that can only be answered when such a facility is taken from the laboratory to the field." For example, according to him, tests that should be done regarding the production cost of the nano-robots and the operating cost of the system.

In addition, in the demonstration performed by the company, the nanorobots removed only sodium (and not other salts) - so, according to Levy, it is necessary to check and see if the process in question works on all the salts in a way that will leave some of the magnesium in the water - the concern for its presence there is what led to the birth of the development in the first place. In addition, unlike the reverse osmosis method - the new system does not treat other substances found in the water, such as bacteria, viruses and fungi.

At the same time, Levy agrees that if the system works with large amounts of water - the development may lead to significant energy and economic savings. "The biggest energy consumers in reverse osmosis desalination are the high pressure pumps - the part of the desalination process that the development is designed to replace," he explains.

However, according to Levy, replacing the large and industrialized desalination plants is a move that requires overcoming many and varied hurdles and therefore it is a situation that may only occur in the distant future, if at all. Therefore, he suggests seeing the new method as a possible solution for remote and energy-poor areas. "This relatively simple system may be able to provide an answer to the multitudes of people who still do not have access to clean and fresh drinking water, but are surrounded by salty water," he says.

Indeed, Wirzer's dream does not stop at Israel's borders. "Ultimately, the company's goal is to produce many units of the system along the coasts of the world, also in places like Morocco, the United Arab Emirates and Saudi Arabia - and our ambition is that this way it will be possible to turn deserts into green areas", he says. "These days we are in the process of raising funds so that we can produce a large amount of nanorobots, develop a prototype that knew how to precipitate a cube of water and also additional nanorobots that knew how to catch other salts such as boron, magnesium and calcium", he concludes.

More of the topic in Hayadan: