Abstract：Fixed carbon content was not only an industrial index for graphite ore, but also an important factor to evaluate the grade reserves of graphite ore. Fixed carbon was the residual carbon after removing inorganic carbon and organic carbon. The inorganic carbon was removed by adding nitric acid(2+8) in the beaker followed by boiling at low temperature, and the organic carbon was removed by burning and ashing. The determination of fixed carbon in graphite ore was realized by high frequency combustion infrared absorption with metallic tungsten and pure iron as the flux. The effect of crucible treatment method, nitric acid concentration, ashing temperature, ashing time and the mass ratio of tungsten to pure iron on the determination were discussed. The results showed that the blank of crucible was less than 0.003% after burning in muffle furnace at 1 050 ℃ for 2 h, and its influence on the determination results could be ignored. The inorganic carbon in sample could be effectively removed after treatment with nitric acid(2+8). The organic carbon in sample could be effectively removed by burning at 450 ℃ for 3 h. After optimization, the mass ratio of metallic tungsten to pure iron in flux was 1.7∶0.3. Under the optimized conditions, the limit of detection was 0.000 80%, and the limit of quantification was 0.002 67%. The content of fixed carbon in graphite ore certified reference material for composition analysis was determined according to the experimental method. The results were basically consistent with the standard values. The relative standard deviations (RSDs, n=6) were between 1.2% and 3.5%. Six graphite ore samples with different content gradient were determined according to the experimental method, and the RSDs were between 2.1% and 9.2%. Meanwhile, the samples were also determined by non-aqueous titration method in standard method of GB/T 3521-2008. The relative errors of two methods were less than the allowable limits of relative errors specified in The specification of testing quality management for geological laboratories.
王斌, 李霈, 刘巍平. 高频燃烧红外吸收法测定石墨矿中固定碳[J]. 冶金分析, 2021, 41(3): 51-55.
WANG Bin, LI Pei, LIU Weiping. Determination of fixed carbon in graphite ore by high frequency combustion infrared absorption method. , 2021, 41(3): 51-55.
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