Nanostructured Hybrid Hydrogels for Solar-Driven Clean Water Harvesting from the Atmosphere

Md Nizam Uddin; Md Fozle Rab; A K M Nazrul Islam; Eylem Asmatulu; Muhammad M Rahman; Ramazan Asmatulu

doi:10.3390/ma15217538

Nanostructured Hybrid Hydrogels for Solar-Driven Clean Water Harvesting from the Atmosphere

Materials (Basel). 2022 Oct 27;15(21):7538. doi: 10.3390/ma15217538.

Authors

Md Nizam Uddin¹, Md Fozle Rab², A K M Nazrul Islam³, Eylem Asmatulu⁴, Muhammad M Rahman⁴, Ramazan Asmatulu⁴

Affiliations

¹ Department of Engineering and Physics, Texas A&M University, Texarkana, TX 75503, USA.
² Bangladesh Railway, Rajshahi 6100, Bangladesh.
³ Department of Mechanical System Engineering, Tokyo University of Agriculture and Technology, Tokyo 184-8588, Japan.
⁴ Department of Mechanical Engineering, Wichita State University, Wichita, KS 67260, USA.

Abstract

The scarcity of useable water is severe and increasing in several regions of the Middle East, Central and Southern Asia, and Northern Africa. However, the earth’s atmosphere contains 37.5 million billion gallons of water in the invisible vapor phase with fast replenishment. The United Nations Convention to Combat Desertification reports that by 2025 about 2.4 billion people will suffer from a lack of access to safe drinking water. Extensive research has been conducted during the last two decades to develop nature-inspired nanotechnology-based atmospheric water-harvesting technology (atmospheric water generator, AWG) to provide clean water to humanity. However, the performance of this technology is humidity sensitive, particularly when the relative humidity (RH) is high (>~80% RH). Moreover, the fundamental design principle of the materials system for harvesting atmospheric water is mostly unknown. In this work, we present a promising technology for solar energy-driven clean water production in arid and semi-arid regions and remote communities. A polymeric electrospun hybrid hydrogel consisting of deliquescent salt (CaCl2) and nanomaterials was fabricated, and the atmospheric water vapor harvesting capacity was measured. The harvested water was easily released from the hydrogel under regular sunlight via the photothermal effect. The experimental tests of this hybrid hydrogel (PAN/AM/graphene/CaCl2) demonstrated the feasibility of around 1.04 L of freshwater production per kilogram of the hydrogel (RH 60%). The synergistic effect enabled by photothermal materials and deliquescent salt in the hydrogel network architecture presents controllable interaction with water molecules, simultaneously realizing efficient water harvesting. This technology requires no additional input of energy. When considering the global environmental challenges and exploring the available technologies, a sustainable clean water supply for households, industry, and agriculture can be achieved from the air using this economical and practical technology.

Keywords: atmospheric water generator; electrospinning; fog harvesting; hydrogel; relative humidity.

Grants and funding

This research received no external funding.