Hydrolysis of Antimony(III)-Hydrochloric Acid Solution at 25°C

抄録

The system Sb(III)-HCl–H₂O has been studied by equilibrating mixtures of antimony trioxide and hydrochloric acid solution (<6 kmol/m³) at 25^°C for 30 days. X-ray diffraction analysis of the solids showed the existence of Sb₂O₃ (HCl < 0.1 kmol/m³) and Sb₄O₅Cl₂ (HCl>0.1 kmol/m³) as the final solid phases. The solubility for both compounds was also determined as a function of HCl concentration. The hydrolysis of antimony(III)-hydrochloric acid solution (Sb(III) = 140 mg/L, HCl = 0.1 and 1.0 kmol/m³) by neutralizing with NaOH solution was then studied in a pH range of 1.1 to 12.3 at 25^°C. The amorphous Sb₈O₁₀(OH)₂Cl₂ (spherical, particle size: 0.05–0.2 μm), crystalline Sb₈O₁₀(OH)₂Cl₂ (orthorhombic, rectangular plate in 1 μm thick layer) and crystalline Sb₂O₃ (orthorhombic) were found to be a solid phase depending on pH and hydrolysis time. The particle morphology of Sb₂O₃ was affected strongly by pH. The minimum solubility of crystalline Sb₈O₁₀(OH)₂Cl₂ (pH 2–3) and Sb₂O₃ (pH 3–11) was at a level of 10 mg/L in Sb(III).