China Nonferrous Metallurgy

Based on the fact that the solubility product of manganese sulfide, ferrous sulfide and thallium (Ⅰ) sulfide exceeds that of arsenic sulfide, this paper aimed to improve the existing high-pressure closed digestion-ICP-MS method to make part of the metal ions brought by the impurities fully digest into the solution, so as to improve the accuracy and precision of determination of Mn, Fe and Tl in sulfide residue. It is found after optimization that the optimal digestion condition exists in a mixed acid system of hydrochloric acid + nitric acid + hydrofluoric acid + perchloric acid (with a volume ratio of 15∶5∶5∶3) at a particle size of 250 meshes. The measured value of Mn, Fe and Tl are respectively 0.025 70 g/kg, 0.024 10 g/kg and 0.000 50 g/kg in sulfide residue after arsenic removal. The improved method was used to determine the national standard substance of Mn and Fe ore and standard substance for composition analysis of sulfide single mineral. The internal standard elements of 89Y and 192Ir and isotopes of ⁵⁵Mn, ⁵⁶Fe and ²⁰⁵Tl were used to eliminate interference. The determination results showed the same results as those measured with national standard method, which indicated high accuracy and precision of improved method. Besides, it can be inferred from the determination results that the hydrogen sulfide was excessive in waste acid sulfidization plant, which provided a certain reference for adjusting the addition of hydrogen sulfide in the subsequent stage.