A Hong Kong University (HKU) research team has created an innovative natural silk nanofiltration membrane that could transform water purification and treatment.
Nanofiltration membranes are widely used in industrial wastewater processing, treatment, and home water filtration applications. They can remove many contaminants, including heavy metals, organic molecules, and microorganisms, while allowing water and beneficial mineral ions (such as Ca2+ and Mg2+) to pass through.
However, the current approach has a major drawback. It requires extremely high pressure, up to 10 bar (10 times the normal atmospheric pressure), making the process energy-intensive and expensive. Bulky equipment is also required.
To tackle this problem, Professor Chuyang Tang and his team developed a silk-based nanofiltration membrane (Figure 1) that can achieve water purification at much lower pressure using a partial vacuum (< 1 bar) instead of high pressure (Figure 2).
In tests, the silk membrane achieved a water flow rate of 56.8 litres per square meter per hour at a vacuum pressure of less than 1 bar. While allowing beneficial minerals to pass through, this membrane rejects over 99% of organic pollutants in water, including the notorious perfluorinated compounds—also widely known as forever compounds—which have caused global concerns over their toxicity and persistence.
“Our new silk-based membrane is a game-changer,” said Professor Chuyang Tang. “It can filter water nearly 10 times faster than classic commercial nanofiltration membranes while efficiently removing harmful contaminants. And it can do this using a light vacuum suction, not intense pressure.”
The silk “ultra-permeable membrane” is sustainable and highly cost-effective, cutting energy consumption by around 80% compared to conventional nanofiltration systems. Prof Tang’s team has obtained a patent for the groundbreaking discovery, which was recently published in the journal Nature Communications article entitled “Ultra-permeable Silk-based Polymeric Membranes for Vacuum-driven Nanofiltration.”
“Silk is an amazing material—strong, flexible, and eco-friendly. We’ve harnessed its unique properties to push the boundaries of water purification,” explained Bowen Gan, the first author of the journal article and a PhD student supervised by Professor Tang.
Link to the article: https://www.nature.com/articles/s41467-024-53042-6
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