Scientists from Nanyang Technological University, Singapore (NTU Singapore), in collaboration with ETH Zurich, Switzerland (ETHZ), have created a membrane made from a waste by-product of vegetable oil manufacturing, which can filter out heavy metals from contaminated water.
The research team, led by Professor Ali Miserez from NTU Singapore’s School of Materials Science & Engineering and the School of Biological Sciences and NTU Visiting Professor Raffaele Mezzenga from the Department of Health Science and Technology at ETHZ, discovered that proteins derived from the by-products of peanut or sunflower oil production can attract heavy metal ions very effectively.
In tests, they showed that this process of attraction, called adsorption, was able to purify contaminated water to a degree that meets international drinking standards.
The researchers’ membrane has the potential to be a cheap, low-power, sustainable, and scalable method to decontaminate heavy metals from water.
Professor Miserez said: “Heavy metals represent a large group of water pollutants that can accumulate in the human body, causing cancer and mutagenic diseases. Current technologies to remove them are energy-intensive, requiring power to operate, or are highly selective in what they filter.”
“Our protein-based membranes are created through a green and sustainable process, and require little to no power to run, making them viable for use throughout the world and especially in less developed countries. Our work puts heavy metal where it belongs – as a music genre and not a pollutant in drinking water,” added Professor Miserez.
The team’s research findings have been published in Elsevier's Chemical Engineering Journal.
The paper’s first author, NTU PhD student Soon Wei Long, said: “Protein-rich sunflower and peanut meals are low-cost raw materials, from which protein can be extracted, isolated, and self-assembled into functional amyloid fibrils for heavy metal removal. This is the first time amyloid fibrils have been obtained from sunflower and peanut proteins.”
The researchers combined the extracted amyloid fibrils with activated carbon to form a hybrid membrane. They tested their membranes on three common heavy metal pollutants: platinum, chromium and lead.
As contaminated water flows through the membrane, the heavy metal ions stick onto the surface of the amyloid fibrils. The high surface-to-volume ratio of amyloid fibrils makes them efficient in adsorbing a large amount of heavy metals.
The team found that their membranes filtered up to 99.89% of heavy metals. Among the three metals tested, the filter was most effective for lead and platinum, followed by chromium.
“The filter can be used to filter any sorts of heavy metals, and also organic pollutants like PFAS (perfluoroalkyl and polyfluoroalkyl substances), which are chemicals that have been used in a wide range of consumer and industrial products,” said Professor Miserez. “The amyloid fibrils contain amino acid bonds that trap and sandwich heavy metal particles between them while letting water pass through.”
The researchers are currently exploring the commercial applications of their membrane with BluAct, a Europe-based water filtration spin-off company of ETH Zurich.
“Plant-based amyloids from food waste for removal of heavy metals from contaminated water” was published in Chemical Engineering Journal, 30 April 2022. DOI: 10.1016/j.cej.2022.136513