EDTA络合滴定法测定选铁尾矿中CaF2含量

采用EDTA络合滴定法测定选铁尾矿中的氟化钙含量。选用稀乙酸浸取试样中的碳酸钙,分离过滤氟化钙,用锆-二甲酚橙褪色分光光度法测定浸取液中的氟含量,折算为在稀乙酸中微溶的氟化钙的量;同时沉淀部分用氯化铝溶液在沸水浴中溶解浸取氟化钙,以三乙醇胺掩蔽干扰离子,在KOH介质中,以钙指示剂为指示剂,用EDTA标准滴定溶液测定沉淀中氟化钙的量,两者之和为试样中氟化钙的含量。用此法对试样进行11次平行测定,相对标准偏差（RSD）小于1.0%。在选铁尾矿试样中加入萤石标准物质进行加标回收实验,加标回收率在99%-102%。方法流程短,操作简单。精密度和加标回收率均能满足要求。

Determination of Calcium Fluoride in Iron Tailings by EDTA Complexometry

EDTA complexometry was used for the determination of calcium fluoride (CaF2) contents in iron tailings. The samples were pretreated by dilute acetic acid to leach calcium carbonate. The contents of CaF2 consist of two parts. On one hand, fluoride contents were determined by zirconium-xylenol orange fading spectrophotometry after CaF2 was filtrated. According to these values, the concentrations of CaF2 were obtained.. On the other hand, CaF2 of the precipitation was leaching by aluminium chloride solution in a boiling water bath. Choosing calcium indicator as an indicator, EDTA standard titration solution was used to determine the amount of precipitation of CaF2 in KOH medium. Therefore, the final CaF2 contents were calculated by the above-mentioned two values. The relative standard deviation (RSD, n=11) was less than 1.0% with the recovery of 99%~102%. The proposed method is simple, rapid, and the precision and recovery can meet the requirements of the determination of CaF2 in iron tailings samples.