Membranes with nanometer-sized pores can filter the herbicide glyphosate and its metabolite AMPA out of water. The success of the process not only depends on the size and charge of the molecules, but also on their hydration: The thicker their hydration shell, the harder it is for them to pass through the membrane. These findings made by researchers at the Karlsruhe Institute of Technology (KIT) will help further improve nanofiltration in order to provide people worldwide with clean water. The results of their study have been published in Nature Communications. (DOI: 10.1038/s41467-026-71492-y )
Water is fundamental to all life - contaminants are harmful to humans and the environment. Herbicides used in agriculture to control weeds present a particular challenge here. The most widely used herbicide in the world is glyphosate. Experts have differing views on its use. Some studies suggest potential risks such as carcinogenic effects in humans, nerve damage, and a negative impact on biodiversity. Since glyphosate may get into the water cycle after its use in gardening or farming, efficient water treatment technologies are required for the protection of our water resources.
Membranes Allow Water to Pass Through While Retaining Contaminants
Researchers from KIT's Institute for Advanced Membrane Technology (IAMT) are working on innovative membrane materials that are permeable to water while retaining contaminants. In a recent study, they collaborated with researchers from Ruhr University Bochum, University of South Bohemia in České Budějovice, and University of Lodz in Poland to find out how glyphosate and aminomethylphosphonic acid (AMPA) can be filtered out by nanofiltration membranes. AMPA is primarily formed in the soil as a glyphosate metabolite. It has similar chemical properties but lasts longer.
Nanofiltration is a pressure-based process in which the pores of the membranes are only a few nanometers in size. "Our study shows that the removal of contaminants such as glyphosate depends not only on the size of the molecules and their charge, but also on the water that surrounds them," said Professor Andrea Iris Schäfer from KIT's IAMT who is the study's corresponding author. "These findings will help us to further improve nanofiltration - and thereby provide people worldwide with clean, healthy water."
Nanofiltration membranes remove contaminants in various ways: Firstly, they work like a strainer that retains molecules that are larger than the membranes' pores. Secondly, many membranes carry an electric charge and repel equally charged ions. Thirdly, molecules in water are often surrounded by a hydration shell consisting of attached water molecules. The resulting hydration affects how large the molecules appear in water and how difficult it is for them to pass the membrane.
water to pass through while retaining contaminants. Nanofiltration is a pressure-based
process in which the pores of the membranes are only a few nanometers in size.
(Photo: Cynthia Ruf, KIT)
Higher pH Levels Are Associated with Greater Molecular Hydration
"We were able to show that the pH of the aqueous solution and the pressure applied during nanofiltration have a decisive influence on the removal of glyphosate and AMPA," said Phuong Bich Trinh, doctoral researcher at the IAMT. Depending on their pH value - that is how acidic or basic the solution is - the molecules can have different charges. With an increasing pH, charge exclusion becomes more significant. Molecule hydration increases as well so that glyphosate and AMPA can be removed more easily from the water. A higher pressure, however, can result in (partial) shredding of the hydration layer, which in turn decreases the degree of removal.
Measuring the hydrate shell of organic substances is a difficult task. For their study, the scientists from Ruhr University Bochum used Fourier-transform infrared spectroscopy (FTIR) in which infrared light interacts with the molecular vibrations. The researchers from the University of South Bohemia in České Budějovice processed the results of these measurements using computer-aided molecular dynamics simulations. The study significantly contributes to our understanding of the molecular details of the filtration process, making nanofiltration technologies even more effective as well cost and energy-efficient.
Original publication
Phuong B. Trinh, Minh N. Nguyen, Zdenek Futera, Babak Minofar, Marco Personeni, Poul Petersen, Andrea I. Schäfer: The role of hydration in the removal of glyphosate (GLY) and aminomethylphosphonic acid (AMPA) by nanofiltration membranes. Nature Communications, 2026. DOI: 10.1038/s41467-026-71492-y
