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Physical & Chemical properties

Water solubility

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Endpoint:
water solubility
Type of information:
read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
weight of evidence
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: Data from handbook or collection of data.
Justification for type of information:
The substance is an aqueous solution of aluminium hydroxide, aluminium nitrate and aluminium sulphate. Aluminium sulphate is one of the constituents of this multiconstituent substance.
Reason / purpose for cross-reference:
read-across source
Principles of method if other than guideline:
data from handbook, no method given
GLP compliance:
not specified
Water solubility:
38.5 other: g/100g water
Temp.:
25 °C
Remarks on result:
other: handbook data, no information on pH value
Endpoint:
water solubility
Type of information:
read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
weight of evidence
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: data from handbook or collection of data
Justification for type of information:
The substance is an aqueous solution of aluminium hydroxide, aluminium nitrate and aluminium sulphate. Aluminium nitrate is one of the constituents of this multiconstituent substance.
Reason / purpose for cross-reference:
read-across source
Principles of method if other than guideline:
data from handbook, no method given
GLP compliance:
not specified
Water solubility:
68.9 other: g/100g water
Temp.:
25 °C
Remarks on result:
other: handbook data, no information on pH value
Endpoint:
water solubility
Type of information:
read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
weight of evidence
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: Peer reviewed official report.
Justification for type of information:
The substance is an aqueous solution of aluminium hydroxide, aluminium nitrate and aluminium sulphate. Aluminium nitrate and aluminium sulphate are constituents of this multiconstituent substance.
Reason / purpose for cross-reference:
read-across source
Principles of method if other than guideline:
official risk assessment, peer reviewed
Remarks on result:
other: See comments on "Any other information on results incl. tables" field below

The three aluminium salts—chloride, nitrate and sulphate—are highly soluble and will form various dissolved species on contact with water. The fate and behaviour of aluminium in the aquatic environment are very complex. Aluminium speciation, which refers to the partitioning of aluminium among different physical and chemical forms, and aluminium solubility are affected by a wide variety of environmental parameters, including pH, solution temperature, dissolved organic carbon (DOC) content, and the presence and concentrations of numerous ligands. Metals in solution may be present as dissolved complexes, as “free” or aquo ions, in association with particles, as colloids or as solids in the process of precipitating.

Aluminium is a strongly hydrolyzing metal and is relatively insoluble in the neutral pH range (6.0-8.0). In the presence of complexing ligands and under acidic (pH<6) and alkaline (pH>8) conditions, aluminium solubility is enhanced.

At low pH values, dissolved aluminium is present mainly in the aquo form (Al3+). Hydrolysis occurs as pH rises, resulting in a series of less soluble hydroxide complexes (e.g. Al(OH)2+, Al(OH)2+). Aluminium solubility is at a minimum near pH 6.5 at 20 °C and then increases as the anion, Al(OH)4-, begins to form at higher pH (Driscoll and Schecker, 1990; Witters et al., 1996). Thus, at 20 °C and pH <5.7, aluminium is present primarily in the form Al3+and Al(OH)2+. In the pH range 5.7 to 6.7, aluminium hydroxide species dominate, including Al(OH)2+and Al(OH)2+, and then Al(OH)3. Typically, at a pH of approximately 6.5, Al(OH)3 predominates over all the other species. In this range, aluminium solubility is low, and availability to aquatic biota should also be low. At pH >6.7, Al(OH)4becomes the dominant species. It is important to note that the various aluminium species described above are always present simultaneously at any pH value. The influence of pH in aquatic systems is mainly to change the proportion of all the species as the pH changes (2008 email from Canadian Wastewater Association to J. Pasternak, Environment Canada; unreferenced).

Mononuclear aluminium hydrolytic products combine to form polynuclear species in solution (Bertsch and Parker 1996). Aluminium begins to polymerize when the pH of an acidic solution increases notably over 4.5:

 

     2 Al(OH)(H2O)52+                      Al2(OH)2(H2O)84+   +   2 H2O

 

Polymerization gradually proceeds to larger Structures, eventually leading to the formation of the Al13 polycation (Parker and Bertsch 1992a, 1992b).

 

Driscoll CT, Schecher WD. 1990. The chemistry of aluminum in the environment.J. Environ Perspect Health 12: 28–49.

Witters HE, Van Puymbroeck S, Stouthart AJHX, Bonga SEW. 1996. Physicochemical changes of aluminium in mixing zones: mortality and physiological disturbances in brown trout (Salmo truttaL.).Environ Toxicol Chem 15: 986–996.

Bertsch PM, Parker DR. 1996. Aqueous polynuclear aluminum species. In: Sposito G, editor, The environmental chemistry of aluminum. 2nd edition.Boca Raton, Florida: CRC Press p. 117–168.

Parker DR, Bertsch PM. 1992a.Identification and quantification of the “Al13” tridecameric polycation using ferron.Environ Sci Technol 26: 908–914.

Parker DR, Bertsch PM. 1992b.Formation of the “Al13” tridecameric polycation under diverse synthesis conditions.Environ Sci Technol 26: 914–921.

 

 

Description of key information

Components aluminium nitrate and aluminium sulphate are highly soluble in water:

aluminium nitrate: 68.9 g/100 g water

aluminium sulphate: 38.5 g/100g water

Aluminium is relatively insoluble in the neutral pH range (6.0-8.0). Solubility is enhanced under acidic (pH<6) and alkaline (pH>8) conditions.

Key value for chemical safety assessment

Additional information

The substance is an aqueous solution of aluminium nitrate and aluminium sulphate and these components are highly soluble in water (68.9 g/100 g water and 38.5 g/100 g water at 25 °C, handbook data). Insofar the solution should be completely miscible with water. Nevertheless aluminium forms various dissolved species depending on pH, temperature, concentration etc. Therefore dilution of the substance may cause precipitation of aluminium hydroxide because the pH value rises.

Solubility of aluminium and its dependence on pH is common knowledge, as described in the assessment report for the three aluminium salts (chloride, nitrate and sulphate) under the Canadian Environmental Protection Act:

Aluminium is a strongly hydrolyzing metal and is relatively insoluble in the neutral pH range (6.0-8.0). In the presence of complexing ligands and under acidic (pH<6) and alkaline (pH>8) conditions, aluminium solubility is enhanced.

At low pH values, dissolved aluminium is present mainly in the aqua form (Al3+). Hydrolysis occurs as pH rises, resulting in a series of less soluble hydroxide complexes (e.g. Al(OH)2+, Al(OH)2+). Aluminium solubility is at a minimum near pH 6.5 at 20 °C and then increases as the anion, Al(OH)4-, begins to form at higher pH .