Aluminium sulphate

Endpoint summary

Additional information

TERRESTRIAL FATE:

Due to the absence of chemical groups or other structural alerts this substance is not considered to exhibit an high hazard potential.

But we can say the following about Terrestrial fate of Aluminium sulphate.

 

-If released to soil, Aluminium sulphate is expected to have very high mobility based upon an estimated Koc of 75.41. Volatilization from moist soil surfaces is not expected to be an important fate process.

Volatilization from moist soil surfaces is not expected to be an important fate process based upon an estimated Henry's Law constant of 2.737E-030 atm-m3/mole Henry's Law constant indicates that volatilization from moist soil surfaces may occur . Aluminium sulphate is expected to volatilize slowly from dry soil surfaces based upon a vapor pressure of 6.01E-024 mm Hg .

 

-If released to air, a vapor pressure of 6.01E-024 mm Hg at 25 deg C ( 6.01E-024 mm Hg is equivalent to vapour pressure of 8.02E-022 Pa ) indicates that Aluminium sulphate will exist solely as a vapor in the atmosphere. Vapor-phase Aluminium sulphate will be degraded in the atmosphere by reaction with photochemically-produced hydroxyl radicals; the half-life for this reaction in air is estimated to be 76.4 days, calculated from its rate constant of 0.1400 E-12 cm3/molecule-sec at 25 deg.

Aluminum sulfate cannot be oxidized and atmospheric transformations would not be expected to occur during transport. If aluminum metal particulates were released to air during metal processing, they would be rapidly oxidized.

In air, aluminum sulfate will react with moisture and produce sulfuric acids, and aluminum oxide. Since these aluminum sulfate is usually not emitted to air, the amount of aluminum present in air would be negligible compared with the amount coming from natural erosion of soil.

 

- If released into water, Aluminium sulphate is not expected to adsorb to suspended solids and sediment based upon the estimated Koc value of 75.41. L/kg . Volatilization from water surfaces is not expected to be an important fate process based upon this compound's estimated Henry's Law constant is 2.737E-030 atm-m3/mole . An estimated BCF of 3.162 suggests the potential for bioconcentration in aquatic organisms is low.

 

Adsorption of aluminium occurs only under pH conditions where it hydrolyzes to give various hydrolysis products. Progressive hydrolysis leads to the formation of colloidal aluminium hydroxide.

- Aluminium sulphate has a propensity to leach through soil if water is applied, i.e. it does have mobility through soil, and providing sufficient water is present. As it moves downwards into layers where the water content is low, the leaching will stop.

On this basis, it does not have a high potential for adsorption to soil if water is not present andonly part of the aluminium sulphate in the solid phase is adsorbed.

 On the other basis if water is present aluminium sulphate as aluminium hydroxide precipitate (Al(OH)3) have a high potential for adsorption to soil.

Hydrolysis is a chemical reaction during which molecules of water (H2O) are split into hydrogen cations (H+, conventionally referred to as protons) and hydroxide anions (OH−) in the process of a chemical mechanism).

 

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)30+ 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.