Antimony(III) sulfide complexes in aqueous solutions at 30 °C: A solubility and XAS study

The Sb K-edge XAS measurements of antimony in alkaline (pH = 10.9 to 12) sulfide solutions gave average first shell coordination environments for strongly alkaline solutions that were consistent the speciation model derived from solubility experiments (i.e., Sb2S42 − and Sb(OH)3(aq)). XAS data enabled the elimination of a speciation model involving only Sb-S monomers at strongly alkaline pH. Antimony speciation in near neutral to strongly alkaline pH's is dominated by dimeric antimony sulfide complexes at sulfide concentrations > 0.001 mol kg− 1 S2 −total. Calculations of stibnite solubility and aqueous antimony speciation for conditions in anoxic marine basins indicate that sulfide species comprise a significant part of the total dissolved Sb(III) when mol kg− 1 S2 −total > ~ 0.00005 mol kg− 1 and that stibnite is close to saturation in some anoxic basins.