Determination of trace gold,platinum and palladium in black shale by graphite furnace atomic absorption spectrometry with bismuth fire assay
MAO Xiangju1,2,3, YAO Mingxing1,2,3, GUO Xiaorui1,2,3, WANG Tiantian1,2,3, NI Wenshan*1,2,3, CHENG Cheng4
1. Zhengzhou Institute of Multipurpose Utilization of Mineral Resources,CAGS,Zhengzhou 450006,China; 2. China National Engineering Research Center for Utilization of Industrial Minerals,Zhengzhou 450006,China; 3. Key Laboratory for Polymetallic Ores' Evaluation and Utilization,MNR,Zhengzhou 450006,China; 4. Paris-Saclay University,Paris 91400,France
Abstract：The contents of Au, Pt and Pd in black shale are relatively low and their distribution is nonuniform. Therefore, a suitable separation and enrichment method should be auxiliary for determination.The composition and structure of black shale samples were analyzed by mineral liberation analyzer. Based on the principle that Ag could form alloys with Au, Pt and Pd, Ag was added as a protective agent to the fire assay ingredient for melting with Bi2O3 as collector, which enhanced the stability of bismuth button. Meanwhile, KNO3 was added into the fire assay ingredient to oxidize S in matrix to sulfates, which entered into melting slag. The resultant bismuth button was treated by cupellation, and the silver composite granule was obtained. Therefore, the separation and enrichment of Au, Pt and Pd in black shale were realized. After the silver composite granule was dissolved by adding HNO3 and then HCl, a method for the determination of Au, Pt and Pd in black shale was established by graphite furnace atomic absorption spectrometry(GF-AAS). The dosages of flour and Bi2O3 in the fire assay ingredient were optimized, then 8 g of flour and 100 g of Bi2O3 were used. The results showed that when 200 μL of 20 g/L Ag standard solution was added into the fire assay ingredient, the formed silver composite granule had regular shape, smooth surface and moderate size without loose bead phenomenon after Bi was blown completely. Under the selected experimental conditions, the calibration curves were drawn with the absorbances of Au, Pt and Pd and their corresponding mass concentrations. The correlation coefficients were between 0.999 7 and 0.999 9. The characteristic concentrations were between 0.338 ng/mL and 2.15 ng/mL. The proposed method was applied for determination of Au, Pt and Pd in certified reference material of black shale for composition analysis of precious metals. The results were basically consistent with the certified values. The precision and recovery tests of black shale samples from Nayong Area of Guizhou Province were conducted according to the proposed method. The relative standard deviations(RSD, n=6) of determination results were between 3.1% and 5.1%, and the recoveries were between 92% and 109%.
毛香菊, 姚明星, 郭晓瑞, 王甜甜, 倪文山, 程诚. 铋试金-石墨炉原子吸收光谱法测定黑色页岩中痕量金铂钯[J]. 冶金分析, 2023, 43(8): 24-30.
MAO Xiangju, YAO Mingxing, GUO Xiaorui, WANG Tiantian, NI Wenshan, CHENG Cheng. Determination of trace gold,platinum and palladium in black shale by graphite furnace atomic absorption spectrometry with bismuth fire assay. , 2023, 43(8): 24-30.
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