Organic vapor leads to dissolution of molecular salts – ScienceDaily


It has long been known that when salt is stored in a humid environment, it absorbs water, dissolving some of the salt and causing it to clump together. Now researchers from Japan have discovered that steam isn’t the only agent that can do this.

In a study published on July 29, 2022 in RSC progressResearchers at the University of Tokyo’s Institute of Industrial Sciences have found that organic vapors can trigger the dissolution of molecular salts in a manner similar to water vapour.

This finding could have applications for cleaning indoor pollutants. Volatile organic compounds (VOCs) are organic chemicals that exist as vapors at room temperature. The highest concentrations of VOCs are found indoors, and some of these are harmful to human health and the environment. These compounds can be removed by a number of methods, but to date, removal through a phenomenon known as organic deliquescence has not been studied.

“Deliquescence has been used to collect atmospheric water vapor, but to our knowledge, organic vapor-induced deliquescence has not been reported,” says lead author of the study, Kazuyuki Ishii. “We studied this phenomenon with several solid molecular salts, which respond to organic vapors by changing from solid to liquid.”

Deliquescence is the process by which a solid becomes a liquid by absorbing enough moisture from the air to dissolve in an aqueous solution. This has been reported for a number of chemicals including calcium chloride (CaCl2), which spontaneously form aqueous solutions under humid conditions. Simply increasing the ambient humidity can cause deliquescence (observed as a solid-to-liquid transition) with some water-soluble chemicals without heating or adding liquid. CaCl2has been used, for example, as a chemical drying agent (i.e., a water-absorbing substance used to induce or maintain dryness).

“We used CaCl2 Powder in a typical control experiment, where it clearly turned into an aqueous solution through water vapor-induced deliquescence,” explains Kyoko Enomoto, senior author of results of this control experiment under equivalent conditions.”

The researchers observed that the molecular salts changed from solid to liquid when chemicals such as chloroform (CHCl3) were used as organic solvents.

“We found that organic deliquescence is not uncommon – instead, appropriate organic deliquescence responses to VOCs can be engineered based on the general rule ‘like dissolves like’,” explains Ishii.

There is an urgent need to remove VOCs from indoor environments with organic solvents, especially from industrial facilities that use large volumes. Based on the effectiveness of CaCl2 As a chemical desiccant for collecting atmospheric water vapor, the results of this study offer a promising method for the development of means for capturing VOCs.

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Materials provided by Institute of Industrial Sciences, University of Tokyo. Note: Content can be edited for style and length.


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