Determination of Lead in Mississippi Valley-type Ore by Inductively Coupled Plasma-Optical Emission Spectrometry after Acid Digestion

The main metal minerals in the Mississippi Valley-type (MVT) Pb-Zn deposit are galena and sphalerite. The associated barite and fluorite in the MVT ores can result in the formation of barium sulfate during acid digestion, leading to the determined Pb contents being lower than the real values. In this study, MVT ores are digested by hydrochloric acid-nitric acid-hydrofluoric acid (HCl-HNO₃-HF) and then the Pb contents are determined by Inductively Coupled Plasma-Optical Emission Spectrometry (ICP-OES). Digestion effects of HCl-HNO₃-HF, HCl-HNO₃-HF-HClO₄ and HCl-HNO₃-H₂SO₄, are investigated by X-ray Diffraction (XRD). Experimental results show that HCl-HNO₃-HF can prevent the formation of the mixed sulfate (Ba, Pb)SO₄, and the appropriate amount of HF can promote the dissolution of PbSO₄. XRD analyses also show that no PbSO₄ remained in precipitation. The precision (RSD) ranges from 0.3% to 0.7%. Recoveries by the standard addition method range from 96.0% to 99.2%. The best detection range of lead in MVT ore samples was 0.01%-20.0% (m/m).