According to the World Health Organization (WHO), about 785 million people around the world lack a clean source of drinking water. The climate crisis is making things worse. Saltwater, which makes up around 97 % of the water on our planet, is a huge untapped resource. Solutions are urgently needed to make it suitable and safe. According to the journal ‘Nature Sustainability’, scientists have developed technology that converts seawater into clean drinking water in under 30 minutes by using sunlight. “Sunlight is the most abundant and renewable source of energy on Earth,” Prof. Huanting Wang from the Department of Chemical Engineering at Monash University in Australia told the United Kingdom’s ‘Daily Mail’. “Our development of a new adsorbent-based desalination process through the use of sunlight for regeneration provides an energy-efficient and environmentally-sustainable solution for desalination.” Desalination is a process that turns undrinkable salty water into drinkable water.
Pass the salt
“Desalination has been used to address escalating water shortages globally,” Prof. Wang explained in ‘EurekAlert!’. “Due to the availability of brackish water and seawater, and because desalination processes are reliable, treated water can be integrated within existing aquatic systems with minimal health risks.” He continued: “But, thermal desalination processes by evaporation are energy-intensive, and other technologies, such as reverse osmosis, has [sic] a number of drawbacks, including high energy consumption and chemical usage in membrane cleaning and dechlorination.” Together with sunlight, the scientists used a material called metal-organic framework (MOF) to filter pollutants out of seawater in just half an hour. This highly efficient process generates large amounts of fresh water every day while expending much less energy than other methods. They developed a new type of MOF called PSP-MIL-53 that traps salt and impurities in brackish (slightly salty) water and seawater. When this material is placed in water, it pulls ions out of the liquid and holds them on its surface. The MOF reduces the total dissolved solids in the water from 2 233 parts per million (ppm) to under 500 ppm within 30 minutes. The WHO’s threshold for safe drinking water is 600 ppm. The material delivers up to 139.5 l of fresh water per kg of MOF daily. The MOF can be quickly and easily cleaned for reuse. This is because the material releases all of the salt ions it has soaked up from the water after just 4 minutes of exposure to sunlight.
Can sunlight overcome the water shortage problem?
“This study has successfully demonstrated that the photoresponsive MOFs are a promising, energy-efficient, and sustainable adsorbent for desalination,” Prof. Wang added. “Our work provides an exciting new route for the design of functional materials for using solar energy to reduce the energy demand and improve the sustainability of water desalination.” “These sunlight-responsive MOFs can potentially be further functionalised for low-energy and environmentally-friendly means of extracting minerals for sustainable mining and other related applications,” he concluded.
saltwater, salty water, sunlight, MOF, desalination