Determination of bismuth in bismuth-riched silver concentrate by EDTA titration
ZHANG Zhuo-jia1,2, ZHOU Zhi-yong1,2, XIE Lei1,2
1. ChenZhou Product and Commodity Quality Supervision and Inspection Institute, Chenzhou 423000, China; 2. National Quality Supervision and Inspection Center of Precious Metal and Heavy Nonferrous Products (Hunan), Chenzhou 423000, China
Abstract：The content of bismuth in silver concentrate directly affects the selection of smelting process and metal balance management, and it is an important index for the evaluation of silver concentrate. However, the determination methods of bismuth in bismuth-riched silver concentrate with bismuth content of higher than 5% (mass fraction) are rarely reported. Therefore, it is necessary to develop a rapid and accurate determination method of bismuth in bismuth-riched silver concentrate. The semi-quantitative composition analysis of bismuth-riched silver concentrate sample was conducted using wavelength dispersive X-ray fluorescence spectrometer (WDXRF) and high frequency infrared carbon-sulfur analyzer. It was found that the sample mainly contained silver, lead, bismuth, copper, antimony, iron, sulfur, silicon and carbon. On the basis of this, the sample dissolution system as well as the interference and elimination method of coexisting elements was discussed. The results showed that the sample solution was clear after dissolution in hydrochloric acid-nitric acid-perchloric acid-hydrobromic acid system, and the endpoint was obvious. The sulfur in sample was removed by hydrochloric acid volatilization. The carbon in sample was removed by heating nitric acid and perchloric acid to fuming. The volatilization of arsenic, tin and selenium in sample was complete by twice dissolution with hydrobromic acid. Most of antimony was also removed, and the residual antimony could be masked by adding 5mL of 100g/L tartaric acid solution. The copper was masked by adding 5mL of saturated thiourea solution, and the iron (III) could be masked by adding 0.2g of ascorbic acid. The interfere tests of other coexisting element showed that the interference of silver, lead, zinc, cadmium, magnesium and molybdenum in sample could be ignored. The pH of sample solution was adjusted to 1.5-1.7 with saturated ammonium acetate solution and nitric acid (4+96). The content of bismuth was titrated with EDTA standard titration solution. The determination method of bismuth in bismuth-riched silver concentrate by EDTA titration was established.The recovery tests of bismuth in three bismuth-riched silver concentrate samples were conducted according to the experimental method, and the recoveries were between 98% and 102%. The proposed method was applied for the determination of bismuth in five bismuth-riched silver concentrate samples, and the relative standard deviations (RSD, n=11) of the determination results were between 0.39% and 0.87%. The determination results were consistent with those obtained by inductively coupled plasma atomic emission spectrometry (ICP-AES).
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