Registration Dossier
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EC number: 233-135-0 | CAS number: 10043-01-3
Biodegradation in water and sediment: simulation tests
Administrative data
Link to relevant study record(s)
Description of key information
Aluminum sulphate will not degrade in surface water and goes into solution without undergoing chemicals decomposition. Aluminium ions will remain as aluminium ions.
When released into water, the aluminum sulphate hydrolyses to form aluminum hydroxides.
Reactions between aluminum sulphate, water and associated “impurities” result in the formation of a floc, which separates from the water phase to form alum sludge. A small fraction of the aluminum can stay in the water in either colloidal or dissolved form.The different reactions involved in the formation of aluminum hydroxide in aqueous solution was described; the overall reaction can be represented by the following equation:
Al2(SO4)3+ 6H2O<=> 2Al(OH)3 0+ 3H2SO4
The aluminum hydroxide present in sludge is expected to remain mostly solid following release into surface water.Experiments were showed that less than 0.2% of the aluminum hydroxide present in sludge was released in supernatant water at a pH of 6 and less than 0.0013% was released at pH 7.65. In both cases, aluminum hydroxide was present mostly in particulate form. At these pH values, aluminum solubility is low and kinetics favour the formation of solid aluminum hydroxide.
When heated between 770 and 860°C Aluminum sulphate decomposes to produce Aluminium oxide and Sulfur trioxide. It combines with water forming hydrated salts of various compositions
Al2(SO4) 770 - 860°C 2Al2O3 + 6SO2 + 3O2
Al2(SO4)3 + 6 NaHCO3 → 3 Na2SO4 + 2 Al(OH)3 + 6 CO2
Levels of background oxygen in surface water also indicate a lack of significant degradation.
Key value for chemical safety assessment
Additional information
Biodegradable matter is generally organic material such as plant and animal matter and other substances originating from living organisms, or artificial materials that are similar enough to plant and animal matter to be put to use by microorganisms.
Aluminium sulphate which, as an inorganic compound, would not be expected to biodegrade.
References:
Agency for Toxic Substances and Disease Registry (ATSDR), 1996 Toxicologicalprofile for aluminium. Atlanta, GA: ATSDR, US Department of Health and HumanServices.
According to “ANNEX VII - STANDARD INFORMATION REQUIREMENTS FOR SUBSTANCES MANUFACTURED OR IMPORTED IN QUANTITIES OF ONE TONNE OR MORE”, a ready biodegradability study does not need to be performed for an inorganic substance. As Aluminum sulphate is inorganic substance, a ready biodegradability study does not need to be conducted.
Aluminum sulphate will not degrade in surface water and goes into solution without undergoing chemicals decomposition.Aluminium ions will remain as aluminium ions.
When released into water, the aluminum sulphate hydrolyses to form aluminum hydroxides.
Reactions between aluminum sulphate, water and associated “impurities” result in the formation of a floc, which separates from the water phase to form alum sludge. A small fraction of the aluminum can stay in the water in either colloidal or dissolved form.The different reactions involved in the formation of aluminum hydroxide in aqueous solutionwasdescribed; the overall reaction can be represented by the following equation:
Al2(SO4)3+ 6H2O<=>2Al(OH)30+ 3H2SO4
The aluminum hydroxide present in sludge is expected to remain mostly solid following release into surface water.Experiments wereshowed that less than 0.2% of the aluminum hydroxide present in sludge was released in supernatant water at a pH of 6 and less than 0.0013% was released at pH 7.65. In both cases, aluminum hydroxide was present mostly in particulate form. At these pH values, aluminum solubility is low and kinetics favour the formation of solid aluminum hydroxide.
The anhydrous form occurs naturally as a rare mineral millosevichite, found e.g. in volcanic environments and on burning coal-mining waste dumps. Aluminum sulphate is rarely, if ever, encountered as the anhydrous salt. It forms a number of different hydrates, of which the hexadecahydrate Al2(SO4)3•16H2O and octadecahydrate Al2(SO4)3•18H2O are the most common. The heptadecahydrate, whose formula can be written as [Al(H2O)6]2(SO4)3•5H2O, occurs naturally as the mineral alunogen.
When heated between 770 and 860°C Aluminum sulphate decomposes to produce Aluminium oxide and Sulfur trioxide. It combines with water forming hydrated salts of various compositions
770 - 860°C
Al2(SO4) => 2Al2O3 + 6SO2+ 3O2
Al2(SO4)3+ 6 NaHCO3→ 3 Na2SO4+ 2 Al(OH)3+ 6 CO2
Levels of background oxygen in surface water also indicate a lack of significant degradation.
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