EDTA滴定法测定锑铋精矿中铋

Determination of bismuth in antimony-bismuth concentrate by EDTA titration

对采用盐酸、硝酸和高氯酸溶样方式能溶解铋精矿而不能溶解成分较为相似的锑铋精矿的原因进行了探讨。采用X射线衍射仪(XRD)分别对铋精矿和锑铋精矿进行物相分析,结果表明造成锑铋精矿溶解不完全的原因可能是锑铋共生矿物的不完全溶解。针对这一问题,实验对该溶样方法进行了改进,采取盐酸、硝酸和高氯酸预溶解样品,高氯酸冒烟后补加3次盐酸和氢溴酸继续溶解样品的方法进行溶样。实验表明,采用改进后的方法溶解锑铋精矿样品,所得样品溶液中均有少许灰色不溶渣,但无黑色不溶物。采用焦硫酸钾熔融-酸溶法处理灰色不溶渣后用原子吸收光谱法(AAS)对其中铋进行测定,经计算,灰色不溶渣中铋含量与样品中铋含量的比值不大于0.2%,即灰色不溶渣中的铋可忽略不计。据此,采用上述改进方法进行溶样,建立了EDTA滴定法测定锑铋精矿中铋的方法。对样品量进行了优化,最终选择样品量为0.3g。探讨了锑铋精矿样品中高含量锑对测定的干扰,结果表明,样品中大部分的锑已在溶样过程中挥发出去,而留在样品溶液中的锑也不干扰测定。将实验方法应用于锑铋精矿样品中铋的测定,测定结果的相对标准偏差(RSD,n=8)为0.22%~0.47%,加标回收率在99%~101%之间,所得结果与电感耦合等离子体原子发射光谱法(ICP-AES)的测定值相吻合。

Bismuth concentrate could be dissolved with hydrochloric acid,nitric acid and perchloric acid.However,the antimony-bismuth concentrate with similar composition could not be dissolved with the same acid dissolution method.The reason for this phenomenon was discussed.The phase analysis of bismuth concentrate and antimony-bismuth concentrate were respectively performed with X-ray diffractometer（XRD）.The results showed that the incomplete dissolution of antimony-bismuth paragenetic minerals was possibly the reason for the incomplete dissolution of antimony-bismuth concentrate.Based on this,the original sample dissolution method was improved.The sample was pre-dissolved with hydrochloric acid,nitric acid and perchloric acid.After perchloric acid fume,the hydrochloric acid and hydrobromic acid were supplemented for three times to further dissolve the sample.When the improved dissolution method was conducted for antimony-bismuth concentrate,there was few gray insoluble residues existed in sample solution,but no black insoluble substances.The gray insoluble residues were treated by potassium pyrosulfate fusion-acid dissolution method,and then the content of bismuth in it was determined by atomic absorption spectrometry（AAS）.The calculation results indicated that the ratio of bismuth content in gray insoluble residue to sample was not more than 0.2%.In other words,the content of bismuth in gray insoluble residues could be ignored.Consequently,the determination of bismuth in antimony-bismuth concentrate was realized by EDTA titration after the sample was treated with the improved dissolution method.The sample amount was optimized and 0.3 g was finally selected.The interference of high-content antimony in antimony-bismuth concentrate sample on the determination was discussed.The results indicated that most antimony in sample had been volatilized in sample dissolution process,and the residual antimony in sample solution had no interference with the determination.The experimental method was applied for the determination of bismuth in antimony-bismuth concentrate sample.The relative standard deviations（RSD,n=8）were between 0.22% and 0.47%.The recoveries of standard addition were between 99%and 101%.The results were consistent with those obtained by inductively coupled plasma atomic emission spectrometry（ICP-AES）.