Determination of calcium fluoride in dolomite-bearing fluorite by inductively coupled plasma atomic emission spectrometry combined with fluoride ion selective electrode method
Dolomite-bearing fluorite contains dolomite and calcium silicate.The existing test methods are greatly affected by the fluorite types and the experimental conditions.It is difficult to avoid the interfer-ence of dolomite,calcium silicate,and other components,which leads to higher determination results of calcium fluoride.In this paper,the content distributions of dolomite and calcium silicate in primary filtrate and secondary filtrate were analyzed by respective determination of magnesium and silicon in primary fil-trate,secondary filtrate and sample.Then the determination process was optimized combined with fluorine content in primary filtrate.Dolomite-bearing fluorite was dissolved with 10％acetic acid,and calcium flu-oride in primary residue was extracted with aluminum trichloride solution.The content of fluorine in pri-mary filtrate was determined by fluoride ion selective electrode method,and the content of calcium in sec-ondary filtrate was determined by inductively coupled plasma atomic emission spectrometry(ICP-AES).The results of the two methods were converted into calcium fluoride content and then added together.Con-sequently,a method for determination of low-grade calcium fluoride in dolomite-bearing fluorite was estab-lished by ICP-AES combined with fluoride ion selective electrode.The effect of aluminum trichloride ma-trix on the determination of calcium in range of 10.00-40.00 μg/mL was investigated.The results showed that aluminum trichloride matrix had great matrix effect on the determination of calcium.Therefore,the standard solution series were prepared by matrix matching method.The contents of calcium fluoride in dolomite-bearing fluorite samples were determined according to the proposed method,and the relative standard deviations(RSD,n=7)of determination results were between 0.21％and 0.64％.The recover-ies were between 99.2％and 100.3％.The proposed method could eliminate the interference of dolomite and calcium silicate in dolomite-bearing fluorite on determination results of calcium fluoride.
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