One of the main key points for the survival and development of civilizations, without a doubt, has been and will continue to be access to drinking water. For this reason, many of the most important cities are located next to rivers, where access to drinking water is assured. However, if you live in areas where there are no rivers nearby, engineering plays an important role, since you need to find methods such as desalinating sea water, obtaining potable water from the air, or other alternative methods.

At ATRIA we have experience in this type of project thanks to our Circular Economy area. A very interesting project in which we have worked is the study of the technical feasibility of a solar water treatment system.

The technology to obtain drinking water from seawater is well known and has been in use for decades. However, due to various reasons, notably its operating costs, it has never become a fully exploited process. The new material that we present to you today comes to make this change and significantly reduce the costs of this type of plant.

What is desalination?

Desalination is the process by which the salt and other compounds contained in seawater are extracted to make it suitable for human consumption. This is very important, since, although much of the planet’s surface is covered with water, only a small percentage of this is fresh water, and of this, an even smaller amount is drinking water.

Therefore, being able to transform salt water, which is the most abundant on the planet, into drinking water, is one of the most important tools to be able to supply the entire population and avoid water scarcity.

Types of desalination

There are several methods for desalinating water, and each has different characteristics. Next, we explain the most important ones:

  • Reverse osmosis 

    It is the most widespread desalination system and one of the most profitable. Approximately 60% of the world’s desalination plants use this type of technology. To desalinate the water, a semi-permeable membrane is used, through which the water is passed by exerting a pressure that exceeds the osmotic pressure. This means that only the flow of water is able to pass through the membrane, leaving the salts, ions and large molecules on the other side.

  • Distillation

    It is one of the simplest processes, since it is only necessary to evaporate the water and condense it again. However, to do this with large volumes of water, it requires either long times for the water to evaporate on its own, or large amounts of energy to heat all the water. At an industrial level, it can be carried out in distillation facilities where the temperature and pressure of the steam gradually decreases in various stages, reusing the heat of condensation to re-distill the water.

  • Freezing

    This is a similar method to distillation, but with the phase change in the opposite direction, since it is based on lowering the temperature of the water until it freezes to desalinate it. For this, seawater is sprayed into a cold room that is at low pressure, causing pure ice crystals to form that can be collected and converted into drinkable liquid water when heated.

  • Hydrate formation

    It is one of the most complex desalination processes from a technological point of view, and therefore one of the least widespread. It is based on adding hydrocarbons to seawater in order to form complex hydrate crystals. These crystals can be easily separated from the liquid medium, thus leaving the water desalinated.

  • Flash evaporation

    It is a method similar to distillation where desalination is achieved by turning the water into the vapor phase and then condensing it again to return to its liquid phase. The difference of this method is that the water is introduced in the form of fine droplets into a chamber at a pressure less than the saturation pressure of the water. This causes part of the droplets to go into the vapor phase instantly. The water that has not passed into the vapor phase is successively directed to chambers with even lower pressures, where more vapor is obtained from each of them. Once the water is in the vapor phase, it is condensed in the same way as in distillation.

  • Electrodialysis

    It is an electrochemical desalination process, which is based on the passage of an electric current through salt water. The ions corresponding to the salt (Na + and Cl-), are forced to migrate towards their opposite pole, the positive ions going to the negative pole (cathode), and the negative ions to the positive pole (anode). Two semi-permeable membranes are placed between the two electrodes, allowing only one of the two types of ions to pass through, separating them from the main body of water and therefore desalinating it.

Advantages of the new membrane

As we have mentioned, the reverse osmosis desalination method is the most common and widespread, so scientists are focused on improving its efficiency and reducing its operational costs. It is precisely at this point, where Korean researchers have made their breakthrough, managing to develop a semi-permeable membrane, essential for the process, whose useful life is up to 15 times longer than current membranes.

Today’s commercial membranes, despite their good performance, only have a useful life of 50 hours, after which they begin to let ions and large molecules pass. If the membranes are not removed within this time, the desalinated water flow will end up being contaminated, so it is very important to change them regularly every 2 days.

However, the new membranes, manufactured using coaxial electrospinning, instead of the usual electrospinning technique, allow a PVDF-HFP polymer and a silica airgel to be mixed, resulting in a membrane with a superhydrophobic and permeable surface. to water vapor.

The tests carried out with this new membrane have shown that it maintains an efficiency of 99.99% for 30 days in a row. This result is very positive, and means that these new membranes last 15 times longer than the current ones, and therefore they have to be changed much less regularly, saving costs both in the membranes themselves, and in the maintenance necessary to change them.

Although it is true that the costs of desalination facilities are high and are not reduced only to the fundamental elements of the process, it should be noted that this new type of membranes represents a significant advance towards optimizing the process and obtaining drinking water from of seawater more economically.

What did you think of our blog about the new, more durable membranes? Do you need to improve your material to extend its useful life? Do you want to look for a new material that will add value to your product? Contact us!

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