Scientists in Australia have been able to transform brackish water and seawater into safe, clean drinking water in less than 30 minutes using metal-organic frameworks (MOFs) and sunlight.
In a discovery that could provide potable water for millions of people across the world, researchers were not only able to filter harmful particles from water and generate 139.5L of clean water per kilogram of MOF per day, but also perform this task in a more energy-efficient manner than current desalination practices.
Metal-organic frameworks are a class of compounds consisting of metal ions that form a crystalline material with the largest surface area of any material known. In fact, MOFs are so porous that they can fit the entire surface of a football field in a teaspoon.
Access to safe drinking water is a situation that affects 785 million people worldwide
The World Health Organization suggests good quality drinking water should have a total dissolved solid (TDS) of less than 600 parts per million (ppm). The team of researchers were able to achieve a TDS of less than 500 ppm in just 30 minutes and regenerate the MOF for reuse in four minutes under sunlight.
Lead author Professor Huanting Wang from the Department of Chemical Engineering at Monash University in Melbourne, said this work – which was published in the journal Nature Sustainability – opened up a new direction for designing stimuli-responsive materials for energy-efficient and sustainable desalination and water purification.
“Desalination has been used to address escalating water shortages globally. 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,” Professor Wang said.
A dry dam bed at the Fika-Patso dam near Qwaqwa, in central eastern South Africa in 2017
“But, thermal desalination processes by evaporation are energy-intensive, and other technologies, such as reverse osmosis, has a number of drawbacks, including high energy consumption and chemical usage in membrane cleaning and dechlorination.
“Sunlight is the most abundant and renewable source of energy on Earth. 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.”
More than 780 million people worldwide lack even a basic drinking-water service and by 2025, half of the world’s population will be living in water-stressed areas. The population itself is set to hit 10 billion by 2050 and a staggering 10.9 billion by 2100, according to a UN report. And on top of that, global warming caused by humanity since the industrial revolution has been found to be without parallel in the past two thousand years.
Between 2017 and 2018, South Africa suffered a severe water shortage in the Western Cape region, most notably affecting the City of Cape Town when water levels hovered between 15 and 30 percent of total dam capacity. Significant water restrictions were implemented in a bid to curb water usage, which was successfully reduced by more than half to around 500 million liters (130,000,000 US gal) per day in March 2018 before conditions began to slowly improve.
But it was unquestionably a sign of what will happen again in the not too distant future.
