Antimony Solubility and Speciation in Aqueous Sulphuric Acid Solutions at 298 K

This work is an experimental and theoretical study of antimony speciation and the solubility of Sb₂O₅, Sb₂O₃ and Sb₂(SO₄)₃ at 298 K in aqueous sulphuric acid solutions (0 to 6 kmol/m³). A thermodynamic model was developed to quantify the solubility products and aqueous metal speciation. Main dissolved species were H₃SbO_3(aq) and H₃SbO_4(aq). The solubility of antimony increases with increasing solution acidity and with the presence of hydrogen peroxide in the solution. The following standard equilibrium constants at 298 K were obtained: Log K⁰_(Sb2O5) = 11.7±0.5, Log K⁰_(Sb2O3) = 32±1, and Log K⁰_(Sb2(SO4)3) = 55±2.