Determination of gold in high antimony and bismuth material by lead fire assay gravimetric method after separation with potassium borohydride
High antimony and bismuth material is an intermediate product in the smelting process of non-ferrous metals.The accurate determination of gold content in high antimony and bismuth material has great significance to guide the smelting production and market transaction.When the content of gold in high antimony and bismuth material is analyzed by lead fire assay gravimetric method,antimony and bis-muth easily enter the lead buckle,which will seriously influence on the forming of lead buckle.It is not conducive to the cupellation,leading to great determination error of gold.In experiments,based on the characteristic that antimony hydride and bismuth hydride were easily volatile,the high-valence antimony and bismuth were reduced to low valence with sodium sulfite.Then potassium borohydride was added to react with antimony and bismuth to form the corresponding hydrides,which could be volatilized and sepa-rated.The residue was directly used for lead fire assay.The separation of antimony and bismuth from gold could be realized without filtration and roasting.The method for the determination of gold in high antimo-ny and bismuth materials by lead fire assay gravimetric method was established.The dosages of sodium sulfite and potassium borohydride were optimized.The results showed that the antimony and bismuth in sample could be removed by volatilization under the following experimental conditions:10.00 g of sample was transferred into 500 mL triangular flask;after adding 50 mL of aqua regia(1+1),the solution was heated on electric hot plate to almost dryness;then 20 mL of hydrochloric acid(1+1),10 mL of sodium sulfite solution,and 50 mL of saturated potassium borohydride solution were added;after stirring,the so-lution was heated on electric hot plate to dryness.The mass of lead oxide and silicon dioxide in the ingredi-ents was optimized,and the optimal mass was 80 g and 5 g,respectively.The content of gold in high anti-mony and bismuth material was determined according to the experimental method.The relative standard deviations(RSD,n=7)of the results were between 0.49％and 3.1％,and the found results were basical-ly consistent with those obtained by bismuth fire assay-inductively coupled plasma atomic emission spec-trometry.High purity gold was added into high antimony and bismuth material containing different gold contents for the spiked recovery test.The spiked recoveries were between 96％and 103％.
lead fire assayhigh antimony and bismuth materialsodium sulfitepotassium borohydridegravimetric methodgoldantimonybismuth
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