More and more people worldwide are losing access to clean water; it’s an unfortunate fact of life. While everyone has access to seawater, more often than not, they don’t have access to the purification methods that are necessary to filter out the metals, toxins, and salt from the water. Luckily, people are coming out with water treatments that can be readily accessible as well as environmentally sustainable.
One purification method that’s becoming more and more popular is the process of membrane distillation. Throughout the membrane distillation process, hot saltwater is passed over a membrane on one side, with cold fresh water passing over the other. The temperature difference between the two streams of water leads the hot water from the saltwater to turn into a vapor, passing through the membrane and joining with the cool saltwater.
The good thing about this is that it doesn’t require chemicals to use, thereby separating the water from the saltwater solution. Unfortunately, because of the temperature difference between fresh and saltwater, there needs to be a significant difference in the waters’ temperatures in order to succeed.
One great way to achieve this temperature difference is to heat the membrane itself by adding a layer to the saltwater side that can absorb solar energy. That way, you can direct sunlight to the saltwater layer and increase the heat without using much heating technology. This can be incredibly sustainable, as the power is sourced from the Sun and not anywhere else.
Nanophotonics Enabled Solar Membrane Distillation is one of the ways that’s currently being tested. This technology creates the saltwater layer known as carbon black to absorb the sunlight. When the sunlight is directed towards this layer, the frequencies of visible light are absorbed and transferred into energy, which is used to heat the membrane. It’s cheaper to operate than it would be to heat the entire vat of saltwater and would end up being a more sustainable option, seeing as the heat comes from the Sun and not a power grid.
Not only that, but researchers are also looking into how to take other contaminants out of the water. For example, nitrate, chromate, sulfate, and calcium ions can all negatively impact either a consumer’s health or the homes or industrial processes they come into contact with.
One way researchers are looking to get rid of these contaminants is electrosorption. Electrosorption is using a charge opposite to the ions in the water, attracting them to the electrode. After they’re attracted to the electrode, they can be pulled out of the water and disposed of. Other studies have shown that you can develop electrodes to remove harmful negatively-charged ions. One of them is sulfate, an incredibly dangerous ion that can be converted into hydrogen sulfide by bacteria.
This research is being proven to be incredibly effective, giving people access to clean water at a lower cost than other methods of water purification.