2024-04-07 14:43:43
When salt is immersed in water, the interaction between the positive and negative poles of the water molecules disrupts the bond between the sodium and chlorine ions that make up the salt, causing them to separate and form salt water.
While the principle of salt dissolving in water seems clear, and previous studies have described it theoretically, the ability to observe the details of that process at the atomic level and know which ions dissolve in water first has remained a challenge due to the dynamic movement of dissolved ions within the water, an achievement that has succeeded. A Korean research team in its investigation, And announced In Nature Communications.
The starting point: preparing the study environment
The beginning of the researchers at the Department of Materials Science and Engineering at the Ulsan National Institute of Science and Technology in South Korea was to prepare the environment in which the experiments would be conducted, such that the vacuum conditions were high and the cold temperature was very high (minus 268.8 degrees Celsius).
Working in a vacuum means conducting experiments in a place free of air or other gases, and in a vacuum the pressure is much lower than atmospheric pressure, allowing for specific conditions that cannot be achieved in normal atmospheric environments.
There are different levels of vacuum, ranging from low to very high depending on the pressure level, and very high is often preferred to conduct very sensitive experiments at the atomic or molecular level, as happened in the Korean study, and this leads to achieving several advantages:
- Reduce interference; The absence of air or other gases prevents interference from molecules that might affect experimental results, and this is especially important for experiments that involve sensitive measurements or interactions at the atomic level.
- Vacuum environments reduce contamination by airborne particles or impurities; This ensures the purity of materials and samples used in experiments.
- Vacuum environments provide stable conditions for conducting experiments; Including constant pressure, temperature and humidity levels, this stability is essential to achieving reliable and repeatable results.
No less important than the vacuum environment is the measures taken to ensure that the experiment is carried out under very cold conditions. Cryogenic vacuum conditions achieve several advantages, which are:
- Reducing thermal vibrations; Which can interfere with accurate measurements and observations.
- Cryogenic temperatures help preserve the atomic structure of the materials being studied; This is crucial to maintaining the integrity of the salt membrane and ensuring that the interactions between water molecules and ions occur as normally as possible.
- Lower temperatures help chemical reactions occur at a slower rate; This allows researchers to monitor the process of salt dissolving in water over a long period, and capture subtle changes and interactions that may occur more quickly at higher temperatures.
- Cryogenic conditions can enhance the sensitivity of measuring equipment used in this study, this enables researchers to detect and analyze changes at the atomic level with greater precision.
The researchers used their “single ion control” technique to extract specific ions from the salt (N-Splash).
Single ion control
After preparing the study environment, the researchers used their “single ion control” technology, which allowed them to precisely manipulate individual water molecules to selectively extract specific ions from the salt, allowing them to exert atomic-level control and influence the behavior of the ions within the solution.
To understand what the researchers did, we can imagine salt as a colored bead that includes red beads, represented by “sodium ions,” and blue ones, represented by “chlorine ions.” Instead of simply pouring water on the bead and watching what happens, the researchers presented a new technology that can be likened to “small tweezers.” It is a “single ion control technology” that can capture and move each ion (or bead, depending on the illustration).
During experiments conducted under cryogenic vacuum conditions, they prepared a thin salt film (the colored bead according to our example), then added water molecules to it using a micropipette (an instrument used in laboratories to measure and transfer very small amounts of liquid), and carefully placed the water droplets around The membrane uses small magnets (representing the polarity of water molecules) to control their movement.
Using a scanning tunneling microscope (a tool for imaging and studying surfaces at the atomic and molecular levels), they observed that when water droplets come into contact with the membrane or colored bead, according to the example, something interesting happens: they somehow cause the chlorine ions (the blue bead) to separate from the membrane (the bead colored mother) and dissolved in water, and they were able to see this happening in real time under a microscope.
The researchers repeated this process several times, moving the water droplets in different patterns and observing how each ion (bead) interacted. They also took detailed measurements and collected data to analyze exactly what was happening at the atomic level.
After numerous experiments, they concluded that by carefully manipulating individual water molecules, they might selectively extract specific ions from the salt, revealing insights into the process of salt dissolution in water at the atomic level.
Improve battery performance and other applications
Professor in the Department of Materials Science and Engineering at the Ulsan National Institute of Science and Technology and the study’s lead researcher, Hyung Jun Shin, describes their findings as a “major experimental achievement,” and said in statement “Although the theoretical understanding of salt solubility in water has long been established, our success in extracting single ions through precise control of the water molecule is extremely important work,” the institute released.
He adds, “Ions play a pivotal role in changing the performance of batteries and semiconductor materials, so we envision that taking advantage of the technology of controlling individual ions will help develop basic technologies related to the functions of ions.”
Professor of Materials Science, Co-Director of the Materials Science Center and Director of the Research Office at Zewail City of Science and Technology, Muhammad Al-Kurdi, confirms that the results of the study are an “important achievement,” and indicates in a telephone conversation with Al-Jazeera Net that “it will have multiple applications, not in “Not only in the field of batteries, but also in water desalination and generating hydrogen energy from water.”
Understanding the precise interactions between ions helps in the production of batteries, water purification, and the generation of hydrogen from water (Unsplash)
According to Al-Kurdi, understanding the precise interactions between ions in solution helps in these three areas as follows:
- Battery production; Understanding the precise interactions between ions in solution can help improve ion transport and electrode interactions, which can improve battery performance and extend their life.
- Water desalination; Desalination techniques aim to remove salt and other impurities from seawater or brackish water to produce fresh water, and the ability of researchers to selectively extract specific ions from salt using single-ion control technology might lead to more efficient and selective methods of desalination, compared to traditional methods. Such as reverse osmosis.
- Generating hydrogen from water; Hydrogen is a clean, renewable fuel that can be produced by splitting water molecules through electrolysis. Researchers’ understanding of ionic interactions and manipulation of the water molecule can lead to improvements in electrolysis processes to produce hydrogen. Also, by improving the extraction of ions from water, it may become possible to enhance Efficient and scalable electrolysis systems, reducing the energy input needed to generate hydrogen.
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