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EC number: 233-135-0
CAS number: 10043-01-3
Hydrolysis is an important factor influencing aluminium bioavailability in aquifers with pH, DOC and the presence of other ions involved in determining the specific degree of ligand formation and final in Aquo aluminium concentration present in the system. The calculation of a hydrolytic half life is not useful as regardless of pH, temperature or other parameters present, a specific equilibrium is ultimately reached between aquo to total aluminium concentrations.
speciation of Aluminium is pH dependent. At low pH values, dissolved
aluminum is present mainly in the aquo form (Al3+).
Aluminum hydrolyses increasingly with increased pH and is poorly soluble
in the neutral pH range between 6.0 and 8.0 due to the formation of less
soluble hydroxide complexes (e.g., Al(OH)2+,
Its solubility is at a minimum near pH6.5 at 20°C and then increases as
the anion, Al(OH)4–becomes
presence of complexing ligands and under acidic (pH < 6) and alkaline
(pH > 8) conditions, aluminium solubility is enhanced.
20°C and pH < 5.7, aluminum is present primarily in the formsAl3+
In the pH range 5.7 to 6.7, aluminum hydroxide species dominate,
and then Al(OH)3.
At a pH of approximately 6.5, Al(OH)3
to predominate over the other species. In this range, aluminium
solubility is low. At pH > 6.7, Al(OH)4–becomes
the dominant species.
its size fluoride readily substitutes for OH- and has a strong affinity
for Al under acidic conditions although this is limited by the relative
low abundance of fluoride in the environment. Aluminium-hydroxide
complexes predominate over aluminium-fluoride complexes under alkaline
also complexes with aluminium under alkaline conditions (>pH 6).
Nevertheless aluminium-sulphate complexes were found to represent only
5% of monomeric aluminium in lake studies. While all aluminium species
described are present simultaneously at any pH value the relative
proportion of these species will depend upon pH in aquatic systems.
complexes were a major component of monomeric Al over a wide range of pH
from 4.3 to 7.0 and were found to positively correlate with increasing
DOC concentrations as pH decreased.
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