毒砂作为主要的砷矿物,常与以黄铁矿为主的硫铁矿紧密共生.在毒砂和硫铁矿伴生的矿床选矿中,硫铁矿中砷含量的高低严重影响硫铁矿的品位和应用.实验采用硝酸-氯酸钾饱和溶液溶解样品,加入一定量的硫酸加热冒浓白烟驱除硝酸,然后在盐酸介质中以硫酸铜为催化剂,用次亚磷酸钠将A s5+还原为A s o(单质砷),通过一定的水浴时间和单质砷沉淀静置时间,过滤使砷与其他杂质分离,用过量的重铬酸钾标准滴定溶液溶解As0,最后用硫酸亚铁铵标准滴定溶液滴定过量的重铬酸钾标准滴定溶液,从而准确测定硫铁矿中高含量砷(1％～10％).方法用于两个硫铁矿实际样品中砷的测定,结果的相对标准偏差(RSD,n=9)分别为0.78％和0.51％;并与碘滴定法分析结果吻合.方法避免了采用剧毒试剂三氧化砷测定硫铁矿中高含量砷.
Determination of high content arsenic in pyrite by ammonium ferrous sulfate titration
Arsenopyrite,as the main arsenic mineral,is often closely associated with pyrite which is mainly in pyrite.During the beneficiation of mineral deposits associated with arsenopyrite and pyrite,the level of arsenic content in pyrite seriously affects the grade and application of pyrite.In experiments,the sample was dissolved in nitric acid-potassium chlorate saturated solution.A certain amount of sulfuric acid was added to remove the nitric acid by heating until the concentrated white smoke appeared.Then,sodium hy-pophosphite was used to reduce As5+to As0(elemental arsenic)using copper sulfate as catalyst in hydro-chloric acid medium.After a certain water bath time and the elemental arsenic precipitation time,the arse-nic was separated from other impurities by filtration.As0 was dissolved with excess potassium dichromate standard titration solution,and the excessive potassium dichromate standard titration solution was titrated with ammonium ferrous sulfate standard titration solution.Therefore,the content of high arsenic content(1％-10％)in pyrite could be accurately determined.The proposed method was applied to the determina-tion of arsenic in two samples of pyrite,and the relative standard deviation(RSD,n=9)of measurement results was 0.78％and 0.51％,respectively.Which were consistent with the analysis results by iodime-try.This method avoided the use of highly toxic agent,i.e.,arsenic trioxide,for the determination of high arsenic content in pyrite.
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