Atmospheric Water Harvesting by an Anhydrate Salt and Its Release by a Photothermal Process Towards Sustainable Potable Water Production in Arid Regions

Abstract

Only 2.5% of the water on Earth is fresh water and only less than 1% is accessible to human consumption. Landlocked and desert communities and communities that are not wealthy enough to provide clean drinking water via conventional water treatment technologies are facing severe water shortages and tend to rely on long distance transportation to supply fresh water for their daily use.

As a lot of the water-scarce countries have abundant annual solar irradiation and relatively high humidity, this project proposes a technology that harvests water from ambient air using an anhydrate salt and releases it for collection using sunlight. This technology is designed to be potentially deployed in night-day cycles, as the humidity at night is at its peak, and solar irradiation during the day is also at its peak.

In this work, a mesoporous silica powder filled with CuCl2 and coated with carbon nanotubes is used. The water capture performance of this material was investigated with different relative humidity environments. Furthermore, the powder agglomeration sizes of this material were also investigated for each relative humidity environment. Water release was investigated under 1 kW/m2 simulated solar light in an in-lab ~60% relative humidity environment. The results show that this mesoporous material was able to capture water at 12% relative humidity conditions, low enough to capture water from the air in the Sahara Desert.

At relative humidity of 15% and 35%, the material was able to absorb 0.12 and 0.25 kg/kg of water, respectively, within 100 minutes, which indicates its fast water harvesting kinetics. A fully hydrated sample released 0.26 kg/kg of water in almost half an hour under 1 kW/m2 simulated sunlight. This project sheds more light on utilizing the atmosphere as an alternative water source.