Reusable sponge can remove heavy-metal pollutants from water, resulting in safe, drinkable water

In one test, it was able to absorb up to 99 percent of Texas raw crude oil mixed into 100 milliliters of water within 3 hours in low temperatures.
Loukia Papadopoulos
The new sponge.jpg
The new sponge.

Northwestern University 

Northwestern University engineers have produced a new sponge that can remove toxic heavy metals, like lead, and critical metals, like cobalt, from contaminated water. The end result is safe, drinkable water.

“In proof-of-concept experiments, the researchers tested their new sponge on a highly contaminated sample of tap water, containing more than 1 part per million of lead. With one use, the sponge filtered lead to below detectable levels,” said the institution’s press release published on Wednesday.

“The new sponge shows promise for future use as an inexpensive, easy-to-use tool in-home water filters or large-scale environmental remediation efforts.”

Furthermore, by rinsing the sponge with a lightly acidic solution, the researchers recovered the metals and were able to reuse the sponge for multiple cycles. The research team has outlined design rules for developing and comparing similar tools to remove and recover other heavy metals from water.

In March of 2021, engineers developed another kind of sponge that could soak up 99 percent of oil from cold water. 

"We’re trying to keep the oil as it is, then develop the sponge to capture it," explained at the time Dr. Pavani Cherukupally from the Department of Chemical Engineering at Imperial College London. "This means we don’t have to do the pre-heating process and can directly tackle the problem."

By analyzing the molecular structure of the sticky oil, Cherukupally was able to engineer a nanocoating with a near-identical structure. Covering a sponge with this paraffin-like nanocoating turned a regular sponge into an oil-sucking machine that, in one test, was able to absorb up to 99 percent of Texas raw crude oil mixed into 100 milliliters of water within 3 hours in low temperatures such as 5°C.  The oil was further drained by soaking it in a solvent. 

In March 2017, engineers developed a sponge that could clean mercury from water in just five seconds. The sponge used a low-cost nanocomposite sponge created by a tiny layer of selenium. The selenium surface is covered with a polyurethane sponge that breaks down the mercury. 

The new study is published in the journal ACS ES&T Water.

Study abstract:

The presence of heavy metals in our water supply poses an immense global public health burden. Heavy metal consumption is tied to increased mortality and a wide range of insidious health outcomes. In recent years, great strides have been made toward nanotechnological approaches for environmental problems, specifically the design of adsorbents to detoxify water, as well as for a related challenge of recovering valuable metals at low concentrations. However, applying nanomaterials at scale and differentiating which nanomaterials are best suited for particular applications can be challenging. Here, we report a methodology for loading nanomaterial coatings onto adsorbent membranes, testing different coatings against one another, and leveraging these materials under a variety of conditions. Our tailored coating for lead remediation, made from manganese-doped goethite nanoparticles, can filter lead from contaminated water to below detectable levels when coated onto a cellulose membrane, and the coated membrane can be recovered and reused for multiple cycles through mild tuning of pH. The Nano-SCHeMe methodology demonstrates a platform approach for effectively deploying nanomaterials for environmental applications and for direct and fair comparisons among these nanomaterials. Moreover, this approach is flexible and expansive in that our coatings have the potential to be applied to a range of sorbents.

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