In Fig. 2, the distribution of the individual Hg(II) species in
aqueous solution at low Cl concentration is presented for the
pH-range considered in this work. It has to be stressed, that
non-ideal electrolyte solution properties, effects of ionic strength
and interaction with further dissolved compounds are not considered
by this simplified equilibrium calculation. For improved clarity,
species with insignificant share ( 9), different predominant
Hg(II) compounds are calculated as HgCl2, [Hg(SO3)2]
2
and Hg(OH)2 respectively. Further calculations reveal that the
increase of Cl concentration shifts the equilibrium towards
Hg(II) complexes with three or four Cl ligands in the lower
pH-range (not presented). Increasing S(IV) concentration results
in increased share of [Hg(SO3)2]
2 in the mid pH-range. However,
for all concentrations within the relevant range for FGD waste
waters, the predominant Hg(II) compound changes for increasing
pH-