When factories and homes dump wastewater full of chemicals, cleaning it up usually means drowning the problem in more harsh chemicals. But researchers in Hong Kong have found a smarter way to turn toxic gunk into something useful. Scientists at the Hong Kong University of Science and Technology (HKUST) have developed a new method that uses electricity to transform harmful pollutants in wastewater into solid pieces of plastic-like material that can actually be recovered and reused. The team published their findings in the journal Nature Communications, and the results could change how cities around the world treat dirty water.
The research was led by Professor Irene Lo Man-Chi, who holds a chair professorship in civil and environmental engineering at HKUST. She noticed a major problem with current water treatment methods: they require enormous amounts of chemicals, often miss a lot of the pollution, and sometimes create new toxic byproducts in the process. Her team wanted to find a better way.
The key innovation involves a specially designed electrode made from iodine-coated bismuth oxyiodide, which acts like a molecular fishing hook. When electricity runs through it, the electrode selectively grabs hold of certain pollutant molecules called phenols, which commonly come from pesticides, dyes, and industrial waste. Instead of breaking these molecules apart and losing them forever, the electrode convinces them to link together into longer chains, forming solid polymers that float to the surface where they can be scooped out and collected.
The system achieves an impressive 97.1% selectivity, meaning it targets the right pollutants almost every time, even when the water contains many different chemicals. It works across a wide pH range from 5 to 9, covering most natural water conditions. Perhaps most remarkably, the process requires just 2.93 kilowatt-hours of energy to treat one kilogram of organic carbon pollution, costing only about 30 US cents. This is thousands of times more efficient than conventional methods that simply try to destroy the pollutants.
Professor Lo described the significance: the breakthrough proves that water treatment can shift from a destructive, chemical-heavy process into one that selectively captures pollution and recovers valuable resources. Instead of just to make toxins disappear, future treatment plants might harvest materials that have real economic value.
The team expects this approach could make wastewater treatment roughly twice as cost-effective compared to existing technologies. With clean water becoming an increasingly precious resource globally, innovations that make purification cheaper and more efficient could help more communities access safe drinking water while also reducing plastic waste by finding new uses for recovered materials.