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Stabilization of cationic aluminum hydroxide clusters in high pH environments with a CaCl₂/l-arginine matrix

Author:
Smart, Scott E., Dubovoy, Viktor, Pan, Long
Source:
Chemical communications 2019 v.55 no.43 pp. 5998-6001
ISSN:
1364-548X
Subject:
aluminum, aluminum hydroxide, arginine, calcium, calcium chloride, gel chromatography, hydrolysis, nuclear magnetic resonance spectroscopy, pH, stable isotopes
Abstract:
We present a way of stabilizing cationic partially hydrolyzed aluminum clusters in a non-acidic environment, through Ca²⁺ and l-Arginine doping. The Keggin Al₁₃₋ₘₑᵣ (ε-AlO₄Al₁₂(OH)₂₄(H₂O)₁₂⁷⁺) aluminum cluster can be stabilized with CaCl₂ and l-arginine in a way to preserve the metal clusters. We use size-exclusion chromatography (SEC) and ²⁷Al nuclear magnetic resonance (NMR) spectroscopy to demonstrate that positively-charged Keggin structures are preserved and that the conversion to Al(OH)₃ materials is halted even at alkaline pH. The system serves to stabilize acidic Al clusters in alkaline or neutral conditions, while preserving their inherent cationic behavior.
Agid:
6453375