The Structure and Thermal Properties of Solid Ternary Compounds Forming with Ca2+, Al3+ and Heptagluconate Ions

Ákos Buckó; Zsolt Kása; Márton Szabados; Bence Kutus; Ottó Berkesi; Zoltán Kónya; Ákos Kukovecz; Pál Sipos; István Pálinkó

doi:10.3390/molecules25204715

The Structure and Thermal Properties of Solid Ternary Compounds Forming with Ca²⁺, Al³⁺ and Heptagluconate Ions

Molecules. 2020 Oct 14;25(20):4715. doi: 10.3390/molecules25204715.

Authors

Ákos Buckó¹, Zsolt Kása¹, Márton Szabados², Bence Kutus³, Ottó Berkesi⁴, Zoltán Kónya⁵, Ákos Kukovecz⁵, Pál Sipos¹, István Pálinkó²

Affiliations

¹ Department of Inorganic and Analytical Chemistry, University of Szeged, Dóm sqr. 7, H-6720 Szeged, Hungary.
² Department of Organic Chemistry, University of Szeged, Dóm sqr. 8, H-6720 Szeged, Hungary.
³ Department of Molecular Spectroscopy, Max Planck Institute for Polymer Research, D-55128 Mainz, Germany.
⁴ Department of Physical Chemistry and Materials Science, University of Szeged, Rerrich B. sqr. 1, H-6720 Szeged, Hungary.
⁵ Department of Applied and Environmental Chemistry, University of Szeged, Rerrich B. sqr. 1, H-6720 Szeged, Hungary.

Abstract

In the present work, the structure and thermal stability of Ca-Al mixed-metal compounds, relevant in the Bayer process as intermediates, have been investigated. X-ray diffraction (XRD) measurements revealed the amorphous morphology of the compounds, which was corroborated by SEM-EDX measurements. The results of ICP-OES and UV-Vis experiments suggested the formation of three possible ternary calcium aluminum heptagluconate (Ca-Al-Hpgl) compounds, with the formulae of CaAlHpgl(OH)₄⁰, Ca₂AlHpgl₂(OH)₅⁰ and Ca₃Al₂Hpgl₃(OH)₉⁰. Additional IR and Raman experiments revealed the centrally symmetric arrangement of heptagluconate around the metal ion. The increased thermal stability was demonstrated by thermal analysis of the solids and confirmed our findings.

Keywords: Bayer process; aluminate; calcium; heptagluconate; structure of solid compounds; ternary compounds.

MeSH terms

Aluminum / chemistry*
Calcium / chemistry*
Crystallography, X-Ray
Gluconates / chemistry*
Microscopy, Electron, Scanning
Molecular Structure
Spectrometry, X-Ray Emission
Spectrophotometry, Infrared
Spectroscopy, Fourier Transform Infrared
Spectrum Analysis, Raman
Temperature
Thermogravimetry

Substances

Gluconates
Aluminum
Calcium

Grants and funding

K 124265/Nemzeti Kutatási Fejlesztési és Innovációs Hivatal