Billions of tons of plastic waste are degrading in landfills and waterways around the world. Decades of that garbage is turning into microplastics that find their way into rivers, snow, seafood, bottled water and even people’s blood and organs.
A Chicago-area team of engineers is working on a solution: sponges coated with nanoparticles.
Northwestern University’s Atomic and Nanoscale Characterization Experimental Center (NUANCE) created a sponge that may seem like an ordinary household sponge — but it attracts microplastics when dipped in a special coating.
Microplastics, which result from commercial product development and the breakdown of larger plastics, are less than five millimeters long, according to the National Geographic Society. Their size makes it a challenge to keep them out of the environment, where it can take hundreds of thousands of years to decompose. During that time, wildlife can eat the microplastics. Though it is not clear exactly how harmful consumed microplastics are to human or animal health, a 2017 United Nations resolution discussed the need for regulations to reduce their presence in the environment.
Vinayak Dravid, founding director of NUANCE, recently discussed on WBEZ’s Reset how the engineers’ special sponge works.
Dravid said the sponge gets coated in the pollutant-attracting coating the same way clothing gets dyed different colors.
“The same approach, just take the sponge, dip it in our nanotechnology — we call it magic sauce,” he said. “We squeeze it and it’s ready for action.”
The coating is small, covering only about 5-10% of the sponge.
Different nanotechnology is created for different pollutants, including microplastics. Think of the coating as a glue: When polluted water passes through the sponge, the pollutants stick to the coating and the rest of the water flows through.
Dravid said the process is “extremely effective.”
“In some of the earliest studies, we were stunned to see that we are doing a significant alteration to the sponge,” he said. “We are getting something like a 90% sequestration.”
Nanotechnology is on a tiny scale — on the order of up to 200 nanometers. Dravid said it takes about one billion nanometers to make one meter. Particles this small behave on a different scale than larger ones, and that behavior can be harnessed for useful purposes.
In addition to the microplastic-attracting sponge, Dravid’s team looked at using slightly different coatings to attract oil or fertilizers.
Those coated sponges can be used to remove oil and address algae blooms in waterways.
Dravid said the sponge can absorb up to 30 times its own weight, and the oil it can pick up can then be reused.
“It attracts a tremendous amount of oil and it’s very efficient, meaning the mixture of oil and water, it drags only oil, then you squeeze it and then you do, as they say, imagine using it again and again, 30, 40 times. One unit can recover almost 1,000 times its own weight in oil,” Dravid said.
The technology can be beneficial for nearby Lake Erie, which experiences algae blooms caused by runoff pollution when rainfall washes fertilizer and manure spread on large farm fields into streams that flow into the lake, according to the Alliance for the Great Lakes.
In Chicago and Lake Michigan, Dravid said, harmful pollutants that disrupt the lake’s natural ecosystem may one day be removed using the coated sponges. A student at Northwestern is working on a fourth type of coating for heavy metals, including dissolved lead.
“That’s one of the areas that we are constantly working on, which is to be able to go beyond just lead, cadmium, [as well as] other waterways, which have other pollutants,” he said.
On a smaller scale, the engineers hope the technology will be implemented by everyday folks instead of just to clean out waterways. They hope the technology will stop the source of contamination so the pollutants don’t make it into the environment in the first place.
For example, the coatings could be used in washers, where Dravid said 70% of microplastic originates from.
“Imagine a unit that fits into your washer exhaust and all we do is just leave it there and, as the water passes through, it captures the micro- and nanoplastics separately,” he said. “And we use the filter again and again.”
Bianca Cseke is a digital producer at WBEZ. Follow her @biancacseke1.