Around 71% of the surface of the Earth is covered with water, but only 3.5% is composed of fresh water. Of that amount of fresh water, 68% exists in the form of ice and glaciers. Much of the remaining freshwater resources are unreachable or too polluted. According to UN Environment Programme, almost 40% of the bodies of water in 89 countries are heavily polluted. These figures explain why our planet suffers from a water crisis, as the demand for safe drinking water is unmet.
By 2030, experts predict that the demand for freshwater will exceed the global supply. One of the solutions proposed by environmentalists is the reduction of water pollution to increase our access to clean water and avoid water shortages.
A Unique Solution in Removing Water Pollutants
At Northwestern University, engineers developed a reusable sponge to recover and filter heavy metals and pollutants in contaminated water, making it safe and drinkable.
Research senior author Vinayak Dravid has been previously working on the creation of highly porous sponges that can be used for environmental remediation. In May 2020, his team developed a sponge to clean oil spills. However, the sponge they produced can only remove oil, not the toxic heavy metals left during the spill.
To address this challenge, they improved their sponge and coated it with an ultra-thin layer of nanoparticles. A mixture of manganese-doped goethite materials and other types of nanoparticles was developed and used to cover commercially available cellulose sponges. Then the loose particles are removed by rinsing the coated sponges with water. When submerged in polluted water, the coated sponges can effectively remove lead ions.
After filtering out lead from contaminated water, the sponge can be rinsed with slightly acidic water. Since the trapped lead ions are released, the sponge can be used again to recover more than 90% of the ions in succeeding use cycles.
Another part of the study includes a new set of guidelines established by Dravid and his colleagues to assist the development of tools to target specific metals such as cobalt. They looked for nanoparticles with large surface areas and adherence to metal ions, in addition to being low-cost and nontoxic. This environmental remediation platform called Nanomaterial Sponge Coatings for Heavy Metals (Nano-SCHeMe) allows scientists to differentiate the nanomaterial best suited for specific applications.
The researchers hope their discovery is the key to providing an inexpensive, easy-to-use device for in-home water filters or environmental remediation practices for large-scale industries.
Heavy Metals and Water Pollution
Heavy metals refer to naturally occurring elements with high atomic mass and a density at least five times greater than water. Although they are present in nature, they can become toxic once accumulated in organisms. Common examples of heavy metals are arsenic, lead, and mercury.
Rapid developments in society and industrialization are considered the major source of water contamination. About 40% of the lakes and rivers in the world are contaminated by heavy metals. They can enter water supplies through industrial and consumer waste. Private wells can also be contaminated through the movement of groundwater and surface water run-off.
Contamination of water by heavy metals is a serious threat as it can cause serious health effects. When exposed to heavy metals, a person can acquire chronic and acute toxicity that can lead to various health problems, such as kidney damage, cancers, and even death.
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