[sup 31]P and [sup 27]Al NMR investigations of highly acidic, aqueous solutions containing aluminum and phosphorus

Journal Article · Thu Jan 21 04:00:00 EST 1993 · Journal of Physical Chemistry; (United States)

DOI:https://doi.org/10.1021/j100105a039· OSTI ID:6131792

Mortlock, R F; Bell, A T; Radke, C J ^[1]

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1. Lawrence Berkeley Lab., CA (United States) Univ. of California, Berkeley (United States)

[sup 31]P and [sup 27]Al NMR spectroscopies have been used to characterize acidic, aqueous solutions of orthophosphoric acid, aluminum chloride, and tetramethylammonium (TMA) hydroxide. The final compositions of the solutions range from 0.1 to 1 mol % P, 0.0 to 20 mol % HCl, P/Al = 0.1 to 20, and P/(TMA)[sub 2]O = 2 to 20. Soluble aluminophosphate cations form reactions of hexaaqua Al monomeric cations, [Al(H[sub 2]O)[sub 6]][sup 3+], with phosphate ligands (i.e., H[sub 3]PO[sub 4], H[sub 2]PO[sub 4][sup [minus]], and acid dimers H[sub 6]P[sub 2]O[sub 8] and H[sub 5]P[sub 2]O[sub 7][sup [minus]]). [sup 31]P NMR spectra of aluminophosphate solutions reveal five distinct chemical shift regions. A correlation between the partial charge on P nuclei (calculated using semiempirical molecular orbital theory, MNDO [modified neglect of differential overlap]) and the [sup 31]P NMR chemical shift confirms the assignments of the [sup 31]P NMR resonances. Regardless of the total charge of the complex or the connectivity of the Al to -O-P units, the MNDO calculations show that P atoms in the same type of phosphate ligand bonded to Al monomers have similar partial charges, and, therefore, exhibit nearly identical [sup 31]P chemical shifts. [sup 27]Al NMR spectra of aluminophosphate solutions display four resonances. The assignment of the [sup 27]Al NMR resonances is based on the manner in which the [sup 27]Al and [sup 31]P NMR peaks change in intensity with pH, P, and Al concentration. Estimates of the number of Al-O-P bonds are calculated independently from [sup 31]P and [sup 27]Al NMR spectra and agree quite closely for a range of pH's and both Al and P concentrations. 44 refs., 17 figs., 3 tabs.

• DOE Contract Number: AC03-76SF00098
• OSTI ID: 6131792
• Journal Information: Journal of Physical Chemistry; (United States), Journal Name: Journal of Physical Chemistry; (United States) Vol. 97:3; ISSN JPCHAX; ISSN 0022-3654
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400201* -- Chemical & Physicochemical Properties
ALUMINIUM 27
ALUMINIUM CHLORIDES
ALUMINIUM COMPOUNDS
ALUMINIUM ISOTOPES
AMMONIUM COMPOUNDS
AMMONIUM HYDROXIDES
AQUEOUS SOLUTIONS
CHARGED PARTICLES
CHEMICAL SHIFT
CHLORIDES
CHLORINE COMPOUNDS
DIMERS
DISPERSIONS
HALIDES
HALOGEN COMPOUNDS
HYDROGEN COMPOUNDS
HYDROXIDES
INORGANIC ACIDS
IONS
ISOTOPES
LEWIS ACIDS
LIGHT NUCLEI
MAGNETIC RESONANCE
MATHEMATICAL MODELS
MIXTURES
MONOMERS
NMR SPECTRA
NUCLEAR MAGNETIC RESONANCE
NUCLEI
ODD-EVEN NUCLEI
OXYGEN COMPOUNDS
PH VALUE
PHOSPHORIC ACID
PHOSPHORUS 31
PHOSPHORUS ISOTOPES
RESONANCE
SOLUTIONS
SPECTRA
STABLE ISOTOPES