With the use of a special substance that targets not one, but two hazardous heavy metal pollutants for simultaneous elimination, researchers at the Department of Energys Oak Ridge National Laboratory are addressing a global water crisis.
In actual situations where water supplies contain several chemically identical elements, ORNL’s Ping Li and Santa Jansone-Popova of the Chemical Sciences Division have found an adsorbent with remarkable selectivity for chromium and arsenic.
The novel material was shown by Results published in Small to collect chromium and arsenic in an even 2-to-1 ratio. The key innovation provides chromium and arsenic capture synergy, allowing the material to remove more arsenic the more chromium it can absorb.
According to Jansone-Popova, it is uncommon for an adsorbent to collect two contaminants at once and function rapidly and effectively in a variety of real-world water circumstances.
Two of the most harmful contaminants in drinking water around the world are chromium and arsenic. Both are poisonous and have a negative impact on health, including cancer. Because doses bioaccumulate, or build up with each exposure, and can eventually reach hazardous amounts, even low levels pose serious threats to living things. These substances are naturally occurring, but as byproducts of extensive mining, processing, and manufacturing, their presence in the environment has grown with industrialization and urbanization. Although releases affect the air, soil, and water, drinking water is the most typical exposure route.
These metals dissolve in water to produce chromate and arsenate oxoanions, or salts, that are chemically related to the helpful minerals like phosphate, sulfate, nitrate, and bicarbonate that are naturally present in water. The effects of chromate and arsenate, which are very mobile in water, can be extensive. Without human involvement, they remain in the ecosystem permanently and do not decay. To separate toxic metals from the innocuous mineral salts that are essential to the ecosystem, targeted methods are required.
Jansone-Popova is a member of an ORNL team that specializes in the investigation of adsorbents, substances created to target particular elements and bind them to a surface. Adsorbents can be used in a variety of processes to clean the environment or recover precious metals.
They are one of the most promising choices for water treatment because they are inexpensive, simple to use, and effective at filtering water supplies fast, but Jansone-Popova said they need to be modified for actual application in cleanup situations. It is difficult to create materials that can efficiently separate minute amounts of dangerous substances from the water’s bulk chemical species.
Selectivity is important in adsorbent design. The objective is to catch as much as possible before the adsorbent fills up and needs to be replaced or recycled because a materials surface has finite real estate. In complex environments like water, where similar constituents jostle for space, poorly selective materials lack the accuracy to isolate targets.
An adsorbent with excellent selectivity for chromate that decontaminates water quickly and effectively even when there are competing species was designed by Jansone-Popova in the past. A study published in Environmental Science and Technology demonstrated that the innovative substance obtained a level an order of magnitude below permissible limits set by the U.S. Environmental Protection Agency and reduced chromate concentrations 100-fold in one minute (1 part per million to 10 parts per billion).
The collaboration with Ping Li expands on the strategy used to create a framework for simultaneously trapping chromate and arsenate in a single material.
The method was not intended to be selective for arsenic, but our starting material is very good at trapping chromium in its most hazardous form, hexavalent chromium, Li added. But as this reaction proceeds, the substance is altered, providing a foundation for fresh chemistries.
Researchers changed the initial design to convert collected chromium-6 into chromium-3, a less hazardous condition. The ability to serve as an anchor point to bind arsenate is another advantage of chromium-3. A chemical process that results in stable, chromate-arsenate clusters that are firmly bound to the surface is made possible by the new structure. As a result, the poisons are practically permanently trapped because they cannot wash off or separate from the filter material without being purposefully removed through chemical processing.
We introduced a new architecture that could also bond with arsenic by taking use of the effective hexavalent chromium capture, Li added.
The building was inspired by chromate arsenate, which was originally a pressure-treated lumber additive.
The group is working with partners to broaden the method’s use to other environmental toxins and has patented the structure.
Fundamental findings like these can contribute in the reduction of harmful pollutants in the environment and the achievement of legal requirements for clean water, according to Jansone-Popova.
Bifunctional Ionic Covalent Organic Networks for Enhanced Simultaneous Removal of Chromium(VI) and Arsenic(V) Oxoanions through Synergetic Ion Exchange and Redox Process is the title of the journal paper.
The Office of Science provided funding for the project, which made use of the ORNL Compute and Data Environment for Science’s resources.
The DOE’s Office of Science, the nation’s largest funder of fundamental research in the physical sciences, is managed by UT-Battelle on behalf of ORNL. Some of the most important issues facing our time are being worked on by the Office of Science. Please visit AA5 for further details.
Oak Ridge National Laboratory published it at first.
Researchers: Ping Li, currently employed by Elementis Global, and Santa Jansone-Popova of the Chemical Sciences Division
Adam Malin/ORNL, United States Department of Energy
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