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The bifunctional role of water
- Source :
- Repositório Científico de Acesso Aberto de Portugal, Repositório Científico de Acesso Aberto de Portugal (RCAAP), instacron:RCAAP
- Publication Year :
- 2021
- Publisher :
- Royal Society of Chemistry (RSC), 2021.
-
Abstract
- ERC-2016-CoG 725034 HE 7165/6-1 CH 1922/1-1 The use of water as a component of deep eutectic systems (DES) has raised some questions regarding its influence on the nature of the mixture. Does it form a DES or an aqueous solution and what is the role of water? In this work, the nature of citric acid:l-arginine:water mixtures was explored through phase equilibria studies and spectroscopic analysis. In a first step, PC-SAFT was validated as a predictive tool to model the water influence on the solid liquid equilibria (SLE) of the DES reline using the individual-component approach. Hence, activity coefficients in the ternary systems citric acid:l-arginine:water and respective binary combinations were studied and compared using ePC-SAFT. It was observed that the water-free mixtures citric acid:l-arginine showed positive deviation from Raoult's law, while upon addition of water strong negative deviation from Raoult's law was found, yielding melting depressions around 100 K. Besides these strong interactions, pH was found to become acidic (pH = 3.5) upon water addition, which yields the formation of charged species ([H2Cit]- and [l-arg]+). Thus, the increased interactions between the molecules upon water addition might be caused by several mechanisms such as hydrogen bonding or ionic forces, both being induced by water. For further investigation, the liquid mixtures citric acid:l-arginine:water were studied by FTIR and NMR spectroscopy. FTIR spectra disproved a possible solubility enhancement caused by salt formation between citric acid and l-arginine, while NMR spectra supported the formation of a hydrogen bonding network different from the binary systems citric acid:water and l-arginine:water. Either being a DES or other type of non-ideal solution, the liquefaction of the studied systems is certainly caused by a water-mediator effect based on the formation of charged species and cross interactions between the mixture constituents. This journal is publishersversion published
- Subjects :
- Activity coefficient
Inorganic chemistry
General Physics and Astronomy
Raoult's law
Ionic bonding
02 engineering and technology
Physics and Astronomy(all)
Arginine
010402 general chemistry
01 natural sciences
Citric Acid
Calcium Chloride
chemistry.chemical_compound
Phase (matter)
Freezing
Transition Temperature
Urea
Physical and Theoretical Chemistry
Solubility
Aqueous solution
Hydrogen bond
Chemistry
Water
021001 nanoscience & nanotechnology
6. Clean water
0104 chemical sciences
Models, Chemical
Thermodynamics
0210 nano-technology
Citric acid
Subjects
Details
- ISSN :
- 14639084 and 14639076
- Volume :
- 23
- Database :
- OpenAIRE
- Journal :
- Physical Chemistry Chemical Physics
- Accession number :
- edsair.doi.dedup.....fde00085d6b4a1eea3d547d5ba57e137