Rapid Detection of Aluminium and Iron Impurities in Lithium Carbonate Using Water-Soluble Fluorescent Probes
The real-time measurement of the content of impurities such as iron and aluminium ions is one of the keys to quality evaluation in the production process of high-purity lithium carbonate; however, impurity detection has been a time-consuming process for many years, which limits the optimisation of t...
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| Main Authors: | , , , |
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| Format: | Article |
| Language: | English |
| Published: |
MDPI AG
2024-12-01
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| Series: | Molecules |
| Subjects: | |
| Online Access: | https://www.mdpi.com/1420-3049/30/1/135 |
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| Summary: | The real-time measurement of the content of impurities such as iron and aluminium ions is one of the keys to quality evaluation in the production process of high-purity lithium carbonate; however, impurity detection has been a time-consuming process for many years, which limits the optimisation of the production of high-purity lithium carbonate. In this context, this work explores the possibility of using water-soluble fluorescent probes for the rapid detection of impurity ions. Salicylaldehyde was modified with the hydrophilic group <span style="font-variant: small-caps;">dl</span>-alanine to synthesise a water-soluble Al<sup>3+</sup> fluorescent probe (Probe A). Moreover, a water-soluble Fe<sup>3+</sup> fluorescent probe (Probe B) was synthesised from coumarin-3-carboxylic acid and 3-hydroxyaminomethane. Probe A and Probe B exhibited good stability in the pH range of 4–9 in aqueous solutions, high sensitivity, as well as high selectivity for Al<sup>3+</sup> and Fe<sup>3+</sup>; the detection limits for Al<sup>3+</sup> and Fe<sup>3+</sup> were 1.180 and 1.683 μmol/L, whereas the response times for Al<sup>3+</sup> and Fe<sup>3+</sup> were as low as 10 and 30 s, respectively. Electrostatic potential (ESP) analysis and density functional theory calculations identified the binding sites and fluorescence recognition mechanism; theoretical calculations showed that the enhanced fluorescence emission of Probe A when detecting Al<sup>3+</sup> was due to the excited intramolecular proton transfer (ESIPT) effect, whereas the fluorescence quenching of Probe B when detecting Fe<sup>3+</sup> was due to the electrons turning off fluorescence when binding through the photoelectron transfer (PET) mechanism. |
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| ISSN: | 1420-3049 |