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Spectrophotometric Determination of Vanadium in Carbonaceous Shales (Stone Coal Ores) Using 2‐(5‐bromo‐2‐pyridylazo)‐5‐diethylaminophenol
Author(s) -
Xianzhong Cheng,
Yun Kong
Publication year - 2007
Publication title -
geostandards and geoanalytical research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.037
H-Index - 73
eISSN - 1751-908X
pISSN - 1639-4488
DOI - 10.1111/j.1751-908x.2007.00127.x
Subject(s) - vanadium , chemistry , reagent , spectrophotometry , masking agent , molar absorptivity , sulfuric acid , demineralization , dissolution , inorganic chemistry , nuclear chemistry , chromatography , materials science , enamel paint , composite material , physics , optics
A selective and sensitive spectrophotometric method has been developed for determining the total amount of vanadium in carbonaceous shales (stone coal ores). The method is based on the reaction of vanadium(V) with the chromophore reagent 2‐(5‐bromo‐2‐pyridylazo)‐5‐diethylaminophenol (5‐Br‐PADAP) in the presence of hydrogen peroxide. In a 0.072 mol l −1 sulfuric acid medium, 5‐Br‐PADAP reacts with vanadium(V) to form a red‐violet complex with a maximum absorption peak at 596 nm with an apparent molar absorption coefficient of the complex of 8.45 × 10 4 l mol −1 cm −1 . Beer's law was obeyed in the range 0–25 μg vanadium in 25 ml of solution, with a correlation coefficient of 0.9995. Interferences due to various non‐target ions were also investigated and high quantities of other common inorganic ions were tolerable. The method involved the dissolution of the ore sample by Na 2 O 2 fusion, followed by filtering of the alkali solution after which Fe(III), Cu(II), Ni(II) and Co(II) etc. were effectively separated from the solution by precipitation in a NaOH solution. Selectivity was increased with the use of EDTA as a masking agent. The vanadium in ore samples was determined with a relative deviation (RSD) between 0.20 and 0.76%, and has been successfully applied to the determination of vanadium‐bearing stone coal ores. The results indicated that the accuracy of 5‐Br‐PADAP spectrophotometry is comparable with the ICP‐AES method. The characteristics of the method, i.e., simplicity, selectivity, sensitivity and rapid calibration, make it specially suitable for routine analysis.