New Sunlight-based Water Purification Technology

The technologies for the obtention of drinking water are a frequent topic in our weekly news output. After all, in an increasingly polluted and overpopulated planet, it is one of the most pressing needs for humanity. There are plenty of options out there, from desalination plants, sterilizing chemical compounds such as iodine or chloride, osmotic filters… but some of them are not cost-effective or can be power hungry. Hence, the research for improved techniques is an ongoing process.  

Evaporation is one of the approaches for the purifying of water. This process allows to remove solid particles (heavy metals, salt and other pollutants). However, to achieve it, water must be heated, requiring a large amount of energy in the process, either from electrical sources or else by using expensive optical systems that concentrate the sunlight. Nevertheless, let’s imagine for a moment that large amounts of water could be evaporated solely by sunlight. Guihua Yu, associate professor of materials science and mechanical engineering at The University of Texas at Austin, has found a solution. The key lies in a hybrid gel-polymer material that allows to carry out the process at ambient temperatures. Doctor Yu and his research team have announced their innovative technology in the journal Nature Nanotechnology .

The polymer material that they have developed combines hydrophilic and semiconducting properties. The former enable the gel to absorb water, while the latter boost the absorption of sunlight. In order to operate, the material is placed on the water surface and, while exposed to the solar rays, it starts to produce steam which can be channeled towards a condenser unit.  The efficiency of the technology allows to purify 25 liters per square meter of material. In fact, the tests carried out with water from the dead Sea —one of the saltiest water masses on Earth— have achieved results that comply with the WHO drinking water standards. Another advantage of the patent-pending system is that it can be retrofitted in existing desalination plants without high investment in new infrastructures.

Survival techniques to obtain drinking water

What would you do if you got lost in an area without access to drinking water? Would you be able to survive? Fortunately, you wouldn’t need high-tech hydrogels to survive under such extreme circumstances. Here you have a few techniques that will allow you to cover your daily water needs if you end up stranded in a lost island or you lose your way in a remote location.

• Iodine-based purification. If you are close to a dodgy source of water, you can make use of your first-aid kit by putting a few drops of iodine (between two and ten will do) in a water recipient. Et voilà, there you have a rudimentary potabilization.
• Sunlight purification. Ultraviolet radiation is a power bactericide. If you don’t trust the water, you can filter it through a cloth and fill a bottle. Close it tightly and expose it to the sun for six hours. This method isn’t 100% reliable, as some bacteria may survive, but the other options are surely worse.
• Solar distillation. No water in sight? Don’t panic, if you have a plastic bag maybe you still stand a chance. First, you must dig a twenty-inch deep and thirty-five-inch wide hole. You can also leverage existing cavities in the ground. Now, place a container in the center of the hole and cover the cavity with the plastic wrap. Make sure that the whole perimeter is sealed by using earth or stones. Finally, place a small stone at the center of the plastic film so it dips to a point over the container. Hopefully, twenty-four hours later, the water condensed in the plastic film will have flown spontaneously into the glass or dish at the bottom of the hole.

Of course, besides these DIY methods, there are water purification tablets and even UV pocket purifiers. However, the smartest thing is probably to carry a couple of bottles of water in your backpack if you plan to go hiking in the wilderness. 

Sources: Phys.org