针对目前冰晶石总氟含量常规测定耗时长、操作烦琐、过程物质存在毒害性和测试成本高等不足,提出了碱解-氟离子选择电极法实现快速准确测定冰晶石中的总氟含量。样品预处理过程中,在200℃下采用过量氢氧化钠在镍坩埚中碱解 1 h,可将冰晶石中的氟完全转换为氟离子。溶液电位测量过程中,在样品溶液和氟离子标准溶液中加入TISAB Ⅳ总离子强度调节缓冲溶液来消除Al³⁺的干扰,同时在氟离子标准溶液中加入适量Na⁺和Al³⁺来保证样品溶液和标准溶液的总离子势和Na⁺浓度一致。实验结果表明,该方法与传统化学分析法一致性良好,平均相对偏差为0.40%,最大绝对偏差为0.32%,且5次平行测量相对标准偏差小于0.50%,适用于冰晶石总氟含量的快速批量测定,亦可推广用于其他氟化物中总氟含量测定。

The existing conventional determination methods for total fluorine content in cryolite have shortcomings such as long testing time required,complicated operation,toxic substances involved,and high testing cost.In order to overcome these shortcomings,an alkali hydrolysis-fluoride ion selective electrode method is proposed to determine total fluorine content in cryolite.In the sample pretreatment process,cryolite has been decomposed by excess sodium hydroxide in a nickel crucible at 200℃ for 1 h to facilitate all fluorine to be converted into ionic form.Then,TISAB Ⅳ solution is added into both cryolite sample solution and fluoride ion standard solution to eliminate the interference caused by Al³⁺ and to stabilize the solution's pH value.Besides,appropriate amount of Na⁺ and Al³⁺ are added in the fluoride ion standard solution to keep the total ionic strength and Na concentration consistent between the sample and standard solutions.Experimental results indicate that the accuracy of the proposed method is in excellent with that of the conventional chemical analysis method,showing an average relative deviation and maximum absolute deviation of 0.40% and 0.32%,respectively,and the relative deviation of five repeated measurements is less than 0.5%.Therefore,the proposed method works well for the fast determination of large quantity samples and can be extended to determine other fluorides.

李睿琪(2000-),女,硕士生;龙秉文(1978-),男,博士,教授,研究方向为资源化工,通讯联系人,bingwen＿long@163.com。