Researchers estimate that atmospheric mercury emissions have quadrupled since the industrial revolution. Heavy metals produced by burning fossil fuels and processing industrial and medical wastes are so persistent in the aquatic environment that the U.S. Food and Drug Administration says that about half a dozen species of fish are highly mercury-contaminated. suggest that consumption should be avoided because they. Researchers have been working for years to develop systems for removing mercury from water. But a team at Drexel University may have found a material that efficiently captures evasive mercury, even at low levels, and just the right material to clean up polluted bodies of water.
Among the many methods of removing mercury from water, adsorption, the process of chemically attracting and removing contaminants, is the most promising technology due to its relative simplicity, efficiency, and low cost. One day, Dr. Masoud Soroush, a professor at the Drexel College of Engineering, owns a lab developing new adsorption technology.
“Modern sorbents such as resins, mesoporous silica, chalcogenides and mesoporous carbon are more efficient than traditional sorbents such as activated carbon, clays and zeolites, which have lower affinities and lower capacities for mercury,” Soroush said. I’m here. “But the problem with all these materials is that they still have low mercury removal efficiencies and he cannot bring mercury levels down below 1 ppb.”
Soroush’s team of researchers at Drexel University and Temple University investigated the synthesis and use of surface-modified titanium carbide MXene for mercury removal. MXenes are a family of two-dimensional nanomaterials discovered in Drexel over a decade ago that have shown many remarkable properties.The team recently reported its results dangerous goods journal.
For mercury ion removal, Soroush said, the advantage of titanium carbide MXene is its negatively charged surface and the tunability and versatility of its surface chemistry, making MXene attractive for removal of heavy metal ions. Due to these properties and his MXene layered structure, titanium carbide MXene-based materials have shown excellent performance in gas separation, removal of salts from water, killing of bacteria, and kidney dialysis.
“2D materials such as graphene oxide and molybdenum disulfide have long been found to be effective in removing heavy metals from wastewater by adsorption due to their chemical functionality/structure that attracts metal ions,” says Soroush. says Mr. “Although MXenes are a similar type of material, we speculated that titanium carbide MXenes may have a much greater absorption capacity than these other materials. MXenes are therefore better adsorbents of mercury ions. will be.”
But Soroush’s team needed to make important adjustments to the chemical structure of titanium carbide MXene to further improve the material, one of the most difficult tasks.
“There’s a reason it’s called mercury. Once it’s released into the environment, whether by burning fossil fuels, mining or incinerating waste, mercury is largely avoided.” says Soroush. “It rapidly changes its chemical form – increasing its toxicity and making it very difficult to remove from bodies of water where it inevitably accumulates. So to attract mercury ions even faster, titanium carbide MXene flakes had to change the surface of
Metal ions such as mercury are positively charged and MXene flake surfaces are negatively charged, so there is a natural attraction between the mercury ions and the titanium carbide MXene surface. However, the team needed to boost this attraction in order to more strongly extract mercury ions from the water. To this end, they treated the MXene flakes with chloroacetic acid – a process called carboxylation – which provided MXene with highly mobile carboxylic acid groups, increasing the negative charge on the MXene flake surface and increasing the improves the ability to attract and retain mercury ions.
The result is a new sorbent, carboxylated titanium carbide MXene, which researchers say has demonstrated faster uptake of mercury ions and greater capacity than commercially available sorbents.
“The carboxylated titanium carbide MXene proved to be far superior to the sorbents currently used for mercury ion removal,” says Soroush. “Within 1 minute, he was able to remove 95% of mercury ions from a contaminated water sample at a concentration of 50ppm, which is effective and efficient enough to be used in large-scale wastewater treatment. It means that there is a possibility that
Within 5 minutes, titanium carbide MXene and carboxylated titanium carbide MXene removed 98% of mercury ions from a 10 ml water sample contaminated with mercury ion concentrations ranging from 1 to 1000 ppm.
“This is both [MXene] When [carboxylated MXene] The special structural properties and high density of surface functional groups make it an effective sorbent for removing mercury ions from wastewater,” the team wrote. “In general, the adsorption mechanism of metal ions follows two steps. Initially, the ions are quickly adsorbed to the available active sites and the process is rapid.When the adsorption sites are full, the adsorption progresses slowly and the ions have to diffuse into the pores and intermediate layers. ”
This development is important in the fight to contain mercury pollution, which is so prevalent that health officials recommend avoiding eating certain species of fish entirely. Efforts to contain the mercury released by the combustion of fuel are proving to be as difficult as reducing our dependence on the fuel itself. The ultimate solution to preventing the release of heavy metals such as mercury into the environment is a shift away from polluting energy sources, but Soroush suggests that the breakthrough could lead to new possibilities for cleaning up pollution that is already occurring.
“We envision using the carboxylated MXene technology to remove all heavy metal ions,” he said. “Another way to achieve this, besides using carboxylated MXenes as adsorbents, is to manufacture filters that are coated or embedded with carboxylated MXenes.”
reference: Isfahani AP, Shamsabadi AA, Alimohammadi F, Soroush M. Efficient mercury removal from aqueous solutions using carboxylated Ti3C2Tx MXenes. J. Hazard.meter2022;434:128780. Doi: 10.1016/j.jhazmat.2022.128780
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