A breakthrough has been made in solar water harvesting technology that uses innovative gels and system designs to efficiently extract water from the atmosphere. This technology could revolutionize water use in arid, sunny regions, meeting critical needs for drinking water and other uses.
Atmospheric water harvesters use hygroscopic gels and salts to deliver water to arid areas. More than 2.2 billion people currently live in water-stressed countries, and the United Nations estimates that 3.5 million people die from water-related diseases every year. Because the areas most in need of improved drinking water are also among the sunniest places in the world, there is strong interest in using sunlight to help provide access to clean water.
Researchers at China's Shanghai Jiao Tong University have developed a promising new solar-powered atmospheric water harvesting technology that could help provide enough drinking water to people in these harsh, arid regions. They published their research results in the AIP publishing journal Applied Physics Reviews.
This atmospheric water harvesting technology can be used to increase daily water supply needs such as domestic drinking water, industrial water and personal hygiene water.
Overcoming traditional challenges
Researchers have historically faced challenges when infusing salt into hydrogels because higher salt content reduces the hydrogel's ability to swell due to the salting-out effect. This results in salt leakage and a decrease in water absorption capacity.
"What impressed us deeply was that even if up to 5 grams of salt were injected into 1 gram of polymer, the resulting gel could still maintain good swelling and salt-trapping properties," said researcher Wang Ruzhu.
Innovative absorbent gel and system design
Researchers used plant derivatives and hygroscopic salts to synthesize a super-hygroscopic gel that absorbs and retains large amounts of water. In a dry atmospheric environment, one kilogram of xerogel can absorb 1.18 kilograms of water, while in a humid atmospheric environment, it can absorb up to 6.4 kilograms of water. This hygroscopic gel is easy to prepare and low-cost, making it suitable for large-scale preparation.
In addition, the research team also used a prototype with a desorption chamber and a condensation chamber, configured in parallel. They used a turbofan in the condensation chamber to increase the recovery rate of desorbed water to over 90%.
In an outdoor prototype demonstration, the team found that it could release adsorbed water even in the morning or afternoon when sunlight was weak. The system also enables simultaneous adsorption and desorption during the day.
Future applications and optimizations
The research team will strive to use renewable energy to achieve simultaneous adsorption and desorption to maximize the daily water production per unit mass of adsorbent, thereby further optimizing the performance of the system and making it practical for use in the field of water production.
In addition to daily water production, adsorbent materials that can collect atmospheric water can play an important role in future applications such as dehumidification, agricultural irrigation, and thermal management of electronic equipment.
Reference: "Daytime air-water collection based on simultaneous adsorption-desorption of super-hygroscopic porous gels", author: Xiang Chengjie, Yang Xinge, Deng Fangfang, Chen Zhihui, Wang Ruzhu, December 5, 2023, "Applied Physics Reviews".
doi:10.1063/5.0160682
Compiled source: ScitechDaily