Scientists have created a “smart” sorbent that cleans water and returns valuable resources to production.
How the nano-sponge works
It has a porous cellulose base with a metal oxide nanoparticle coating. The principle is a chemical trap:
- Heavy metals (lead, copper, zinc) bind to the surface of particles through ion exchange.
- Phosphates are captured due to electrostatic attraction.
The material functions on a pH contrast — when the acidity of the environment changes, the sponge captures or releases pollutants, allowing it to be used repeatedly:
- Sorption is activated in neutral water.
- In an acidic environment (pH <4), metals are released.
- In an alkaline environment (pH >10), phosphorus is released.
“We’ve turned a problem into a resource. Instead of burying toxins, we are reusing them,” says Vinayak Dravid, project leader.
Tests in Chicago
Metal factory effluent and agricultural fertilizer pollute the Great Lakes.
Problem:
- The Environmental Protection Agency (EPA) allows up to 1.3 ppm of copper in water.
- Algae blooms were observed because phosphorus levels must be under 0.1 ppm to prevent them.
Solution:
- StormTrap LLC, a company specializing in stormwater treatment, introduced filters based on the sponge into collectors.
- Result: 99% removal of copper and zinc and 94% of phosphates per cycle.
The nano-sponge tackled the algae bloom problem.
Resources vs. ecology
Phosphorus ores are being depleted by 3% each year. At the same time:
- 22 million tons of phosphates are washed into the oceans.
- The extraction of 1 ton of phosphorites emits 5 tons of carbon dioxide.
Re-use example: Metals collected from Chicago’s wastewater are sent to the BatteryCorp plant for battery production.
Development of multipurpose technology
The development of the nano-sponge is the result of many years of research, a kind of “Swiss Army Knife” in the world of water purification, combining various functions:
- 2019: OHM-sponge for oil collection.
- 2021: PEARL membrane for extracting phosphates.
- 2023: Technology for removing lead down to 2 ppb.
- 2025: Multi-tasking Nano-SCHeMe platform.
“Previously, toxic dirt was obtained after cleaning. Now it is raw material for industry,” says Kelly Matuszewski, a graduate student.
Future: from microplastics to rare earth metals
Plans for 2026-2030:
- Marine testing in the Gulf of Mexico.
- Integration with desalination systems.
- Creation of household filters for less than $10.
The project encountered a paradox: the more effective the cleaning, the greater the contribution of agriculture to pollution. The scientists’ answer is mobile units for farms that intercept runoff before it enters rivers.