The risks posed by exposure to Al are controlled by the reactivity of Al-bearing minerals, which in mine wastes are most commonly the sulphates alunite and basaluminite.
With this goal, dissolution experiments using both natural and synthetic alunite and basaluminite will be carried out.
On top of that, advances will be made in the understanding of alunite and basaluminite mineral structure and chemistry, their environmental stability and the behaviour of the potentially toxic element aluminium during dissolution.
Poorly crystalline secondary Fe/AI hydroxy sulfate minerals such as jarosite, schwertmannite, and basaluminite are found in ASS due to the favourable conditions in those environments for their precipitation (McElnea et al.
2002b) reported that synthetic basaluminite released -60% of acidity during 1 M KC1 extraction, in contrast to previously held views which reported that 1 M KC1 was unable to remove the acidity held in such minerals (Lin et al.
RAS] in jarosite, schwertmannite, and basaluminite releases 3, 2, and 2 moles of acidity, respectively (Eqns 4, 5, and 6) (Ahem et al.
0] values from the literature for alunogen (Nordstrom 1982) and basaluminite (Adams and Rawajfih 1977).
These equations were used to produce diagrams of amorphous aluminium hydroxide, alunite, alunogen, basaluminite, gibbsite, and jurbanite solubility plus the observed constant [MATHEMATICAL EXPRESSION NOT REPRODUCIBLE IN ASCII], in terms of pAl[(OH).
Figure 5 displays the solubility lines for minerals often associated with acid drainage, such as amorphous aluminium hydroxide, alunite, alunogen, basaluminite, and gibbsite, plus jurbanite and the 'equilibrium' line established by van Breemen (1973) for his experimentally observed constant value for [MATHEMATICAL EXPRESSION NOT REPRODUCIBLE IN ASCII].
Among them are hydrobasaluminite and basaluminite [[Al.
They proposed that sulfate retention by acid soils might be a consequence of the insolubility of Fe and Al-hydroxy sulfates (such as basaluminite, alunite, and probably their Fe-analogues).
However, sulfate and acidity may well be released from amorphous basaluminite and other metastable or intermediate Al hydroxy-sulfate phases.