Hand-held device can harvest drinkable water using sunlight alone

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Increasing climatic variations have challenged scientists to devise ways to solve the looming issue of water scarcity around the world. It's reported that a third of the world’s population lives in water-stressed regions.

Researchers at UC Berkeley have now developed an innovative solution to the crisis with their hand-held device that can "extract and convert water molecules from the air into drinkable water using only ambient sunlight as its energy source," said a statement from the institute.

The team's work illustrates how specifically created metal–organic frameworks (MOFs) could aid society in coping with and adapting to climate change. MOFs help to capture and store water molecules through their active adsorption sites and pores.

Harvesters driven by MOFs are more efficient

According to scientists, alternative materials like hydrogels, zeolites, or salts fail to function simultaneously under low-humidity circumstances, efficiently use energy, and have a large capacity. Harvesters driven by MOFs are able to handle concerns of water shortage in a variety of contexts, including agricultural and drinking water. Additionally, in areas with an abundance of water but poor quality, this technique may be employed to guarantee pure water.

Data science and machine learning are being used by specialists at the Bakar Institute of Digital Materials for the Planet (BIDMaP) of the College of Computing, Data Science, and Society to speed up and scale the creation of these molecules, materials, and devices.

The methods used are quite effective at collecting water; 85 to 90% of the water it collects as air vapor is released as drinking water. Up to 285 grams of water, or one cup of water, may be gathered per kilogram of the metal-organic framework in a single day. Without replenishment or modification, the MOF can continue to work for numerous cycles over many years. The MOF can be sustainably disassembled and rebuilt in water with no discharge at the end of its useful life.

According to the researchers, it's compact in dimensions compared to the previous MOF-powered harvesters and can fit in a handbag. "Despite the size change, the device is even more energy-efficient. It produced 200 grams of clean water per square meter of water vapor, more than three-fold the water productivity rate of an earlier iteration by Yaghi’s team of a MOF-powered harvester."

The researchers are aiming to develop the system further for efficiency, size, and scale to further the widespread adoption of household-based MOF-powered water harvesters, and community-scale water harvesters, with the help of data science and machine learning. "Those could be in kitchens or even next to air conditioners to supply homes with clean water for cooking and cleaning. Some companies are already working on this," said Yaghi.

The study is published in Nature Water.

Abstract

Sorbent-assisted atmospheric water harvesting has emerged as a promising method to mitigate water stresses in arid climates. Here a new water harvester based on metal–organic frameworks (MOFs) has been designed, constructed, and tested in two locations in California (Death Valley National Park and Berkeley). This water harvester is capable of harvesting water at a capacity of 210 and 285 g H2O per kilogram of MOF-303 per day, respectively. The unique configuration of the MOF cartridge and the condenser in the harvester allows the highest efficiency of water uptake and harvesting from the air without power or energy input aside from ambient sunlight. Indeed, this water harvester operates passively with double the amount of water harvested compared with our previous passive MOF water harvester. These results highlight the great potential for addressing the water stress problem in the world.