Determination of vanadium, molybdenum and nickel in black shale of Kunyang phosphate mine in Yunnan by inductively coupled plasma atomic emission spectrometry

Abstract

The black shale contained high content of carbon and many types of coexisting elements. Due to the incomplete digestion of carbon residue, the injection system of instrument was usually blocked. Meanwhile, vanadium, molybdenum and nickel could be also adsorbed, leading to the lower determination results. In order to eliminate the interference of carbon with the determination of vanadium, molybdenum and nickel, the black shale sample was pretreated by high-temperature burning. The influence of hydrochloric acid medium with different acidities on the spectral strength of vanadium, molybdenum and nickel was investigated. The interference tests of coexisting elements were also conducted. After removing carbon by burning in muffle furnace at 750 ℃, the sample was digested in nitric acid-hydrofluoric acid-perchloric acid system. After acidification by hydrochloric acid and dilution to constant volume, V 311.071 nm, Mo 202.031 nm and Ni 231.604 nm were selected as the analytical lines for determination of vanadium, molybdenum and nickel by inductively coupled plasma atomic emission spectrometry (ICP-AES). The hydrofluoric acid resistant nebulizer was used for sample solution injection. Consequently, a determination method of vanadium, molybdenum and nickel in black shale of Kunyang phosphate mine in Yunan was established. Under the optimum working conditions of instrument, the linear correlation coefficients of calibration curves of elements were all higher than 0.999 5. The detection limit of method was 1.2-8.1 μg/g. The proposed method was applied for the determination of vanadium, molybdenum and nickel in black shale samples of Kunyang phosphate mine in Yunan. The relative standard deviations (RSD, n=11) of determination results were between 0.91% and 5.1%, and the recoveries of elements were between 96% and 102%. The content of vanadium, molybdenum and nickel in national certified reference materials of stream sediment (GBW 07306, GBW 07311 and GBW 07312) was determined according to the proposed method, and the results were basically consistent with the certified values.