Heavy metals pose a serious threat to public health and ecosystems around the world, especially those emitted by industrial processes. Their presence in the water, which is, among other things. consumed by humans and animals is a significant problem and can lead to a wide range of negative health effects, such as developmental delay, kidney damage, increased risk of cancer and liver or lung damage. There is even a risk of death in case of high concentrations and long exposure times.
Heavy metals and their occurrence in water
Common heavy metals in water include manganese, lead, arsenic, chromium and copper. According to the UN Environment Program, nearly 40% of water bodies in 89 countries are heavily polluted, including heavy metals. The highest risk, according to the 2019 risk assessment, is in drinking water and groundwater in Mexico, Saudi Arabia, India, Bangladesh, China, Chile, Thailand and Iran. In Sonora, Mexico, for example, about 43% of drinking water samples from storage tanks and wells had elevated levels of cadmium, arsenic, mercury, copper, lead .
Concentrations of cadmium, lead and copper in drinking water in ten cities in Saudi Arabia exceeded the recommended value. In India, average concentrations of arsenic, manganese, chromium, lead, nickel and zinc in drinking water were higher than WHO guidelines, and in Bangladesh, as much as 42.1% of water samples had arsenic concentrations above 50 μg/l.
These frightening numbers show why our planet is facing a serious water crisis, and the problem is growing every day. Demand for fresh water is expected to exceed global supply by 2030.
Nanotechnology advances in water detoxification
In recent years, scientists have made significant advances in nanotechnology, especially in the design of adsorbents for water detoxification and recovery of valuable metals. Nanomaterials exhibit unique adsorption properties that enable them to effectively remove heavy metals from contaminated water. Unfortunately, using nanomaterials on a large scale and selecting them for specific applications has so far been a real challenge.
Engineers at Northwestern University in Illinois have launched an experimental sponge that removes heavy metals, including toxic (e.g., lead) and critical metals (e.g., cobalt), from contaminated water, leaving it safe to drink. The results of the study were published on May 10 this year. In the journalACS ES&T Water. This new technology builds on previous research conducted by a team of scientists to develop highly porous materials for environmental remediation.
Vinayak Dravid, the study’s author, and his team have developed an innovative solution for environmental remediation by creating a material with high porosity. As early as May 2020. The team presented a sponge that does an excellent job of cleaning up oil spills. However, scientists were quick to point out that it could only remove the oil, not the toxic heavy metals inherent in the spill. Simply coating it with an ultra-thin layer of nanoparticles was enough to achieve the desired results.
Heavy metals removable thanks to manganese-doped goethite coating
During their research, the scientists tested many different types of nanoparticles and found that a coating made of manganese-doped goethite was the most effective. Its production is inexpensive and the necessary ingredients are readily available. This means that the technology can be used on a large scale and can meet industrial and environmental needs.
Its use can lead to a reduction in heavy metal removal costs. And, most importantly, manganese-doped goethite nanoparticles are non-toxic to humans and have properties that are essential for selective remediation of heavy metals. Their structure allows them to selectively bind and remove heavy metals, while leaving other environmental components intact. This enables more precise and effective cleaning.
With such a mixture of goethite materials with manganese and other types of nanoparticles, the researchers coated readily available cellulose sponges on the market. They then rinsed them with water to remove loose particles and dipped them into the contaminated tank. The coated sponges are capable of effectively capturing lead ions.
After the lead filtration process was completed, the sponge was rinsed with slightly acidic water to release the collected ions and prepare it for reuse. This allows the cycle to be repeated. Although the sponge’s performance decreases, it is still able to remove more than 90% of lead ions from samples in successive cycles. This innovative reusable technology creates a perspective for sustainable water treatment and environmental remediation.
Reusable sponge a chance to filter water effectively and inexpensively
The discovery by Northwestern University engineers could have a significant impact on access to clean drinking water and environmental remediation. The discovery of a reusable sponge that removes heavy metals and the development of new guidelines are key steps toward providing an inexpensive and easy-to-use device for home water filtration or environmental remediation for various industries. The reusable sponge can significantly reduce the costs associated with purchasing and replacing traditional filters, making it an attractive solution for those looking for affordable and effective water purification solutions.
Water treatment is an extremely important issue that is constantly evolving. In one of my earlier articles, I discussed one way to deal with the problem of contaminated water with bacteria. However, research in this area is constantly progressing, which we will certainly report on in future issues of Water Issues.