[sup 31]P and [sup 27]Al NMR investigations of the effects of pH on aqueous solutions containing aluminum and phosphorus
- Lawrence Berkeley Lab., CA (United States) Univ. of California, Berkeley (United States)
[sup 31]P and [sup 27]Al NMR spectroscopies are used to characterize the distribution of soluble aluminophosphate species in aqueous solutions of tetramethylammonium (TMA) hydroxide, phosphoric acid, and aluminum chloride. Solution compositions range from 0.1 to 1 mol % P, P/Al = 0.1-5, P/(TMA)[sub 2]O = 0.37-10. For solutions of 1 mol % P, a phase diagram is constructed for various concentrations of TMAOH and Al. The phase diagram is divided into three regions: a high-pH region (pH [ge] 6), a medium-pH range (2 [le] pH [le] 10) in which stable solid phases exist, and a low-pH region (pH [le] 2). In the low-pH region, soluble aluminophosphate complexes form between P species (H[sub 3]PO[sub 4] acid dimers, H[sub 3]PO[sub 4] molecules, and H[sub 2]PO[sub 4][sup [minus]] ions) and Al species (Al monomers as [Al(H[sub 2]O)[sub 6]][sup 3+] cations, and Al dimers as [Al[sub 2](OH)[sub 2](H[sub 2]O)[sub 8]][sup 4+] cations). Specific [sup 31]P NMR and [sup 27]Al NMR peaks are assigned to P and Al nuclei in aluminophosphate complexes which are stable in the low pH range. In the high-pH region, soluble aluminophosphate complexes form between HPO[sub 4][sup 2[minus]] ions and Al species. Also at high pH, [sup 31]P NMR spectra displays a series of sharp resonances (from [minus]2 to 5 ppm) assigned to P atoms in aluminophosphate complexes. [sup 27]Al NMR spectra of the same solutions display broad features centered at 5 ppm assigned to octahedrally coordinated Al bonded through oxygen to P, at [approx]45.5 ppm to pentacoordinated Al bonded through oxygen to P, and at [approx]65 ppm to tetrahedrally coordinated Al bonded through oxygen to P. Independent Al-O-P bond counts from [sup 31]P and [sup 27]Al NMR spectra of aluminophosphate solutions of high pH ([ge]6) indicate that each octahedrally coordinated, pentacoordinated, and tetrahedrally coordinated Al nucleus is bonded primarily to only one phosphate ligand. 21 refs., 13 figs., 2 tabs.
- DOE Contract Number:
- AC03-76SF00098
- OSTI ID:
- 6305835
- Journal Information:
- Journal of Physical Chemistry; (United States), Vol. 97:3; ISSN 0022-3654
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
ALUMINIUM CHLORIDES
NUCLEAR MAGNETIC RESONANCE
AMMONIUM HYDROXIDES
PHOSPHORIC ACID
ALUMINIUM 27
AQUEOUS SOLUTIONS
CHEMICAL COMPOSITION
CHEMICAL SHIFT
CONCENTRATION RATIO
DIMERS
IONS
LEWIS ACIDS
MATHEMATICAL MODELS
MONOMERS
NMR SPECTRA
PH VALUE
PHASE DIAGRAMS
PHOSPHORUS 31
ALUMINIUM COMPOUNDS
ALUMINIUM ISOTOPES
AMMONIUM COMPOUNDS
CHARGED PARTICLES
CHLORIDES
CHLORINE COMPOUNDS
DIAGRAMS
DISPERSIONS
HALIDES
HALOGEN COMPOUNDS
HYDROGEN COMPOUNDS
HYDROXIDES
INORGANIC ACIDS
ISOTOPES
LIGHT NUCLEI
MAGNETIC RESONANCE
MIXTURES
NUCLEI
ODD-EVEN NUCLEI
OXYGEN COMPOUNDS
PHOSPHORUS ISOTOPES
RESONANCE
SOLUTIONS
SPECTRA
STABLE ISOTOPES
400201* - Chemical & Physicochemical Properties