Determination of silica in nickel raw ore by silicon molybdenum yellow spectrophotometry
Silicon content is an important control index in metallurgical process.In this paper,the self-pro-duced nickel ore was used as an example to discuss the experimental conditions affecting the coloring of sil-icon molybdenum yellow as well as common interference of Fe3+and F-in metallurgical samples.The sam-ple was treated by sodium hydroxide melting.The filtrate was taken as the solution to be tested after dry filtration.The acidity was stabilized with sulfuric acid,and the absorbance was measured after adding am-monium molybdate solution for coloring.The results showed that the maintaining of proper coloring acidity was the key to determination,and the addition of other reagents were unnecessary.Taking SiO2 as the unit of measurement,the linear range of calibration curve was 1.00％-40％.The limit of detection was about 1.00％.The apparent molar absorption coefficient was 1.1×104 L·mol-1·cm-1.When the mass concen-tration of F in test solution was higher than 65 mg/L,it would influence on the coloring of silicon-molyb-denum heteropoly acid.When the mass concentration of Fe3+in test solution was less than 7.5 mg/L,it had no influence on the determination.The content of silica in nickel raw ore was determined according to the experimental method,and the relative standard deviation(RSD,n=8)of the determination results was less than 0.6％.The recoveries were between 95％and 100％.As the mass fraction of silica was in range of 20％-40％,the estimation error was 0.4％.Moreover,a method to measure the matching between samples and standard matrix series was also recommended in this study.
silicon molybdenum yellowspectrophotometryacidityfluoride ionmatrix matchingnickel raw oresilica
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