混合碱熔-离子选择电极法测定钨尾矿的氟含量

Determination of fluorine content in tungsten tailings by mixed alkali fusion-ion selective electrode method

钨尾矿中氟含量的测定目前还没有相应的标准方法,为了能够准确测定钨尾矿中氟含量,本实验对混合碱熔-离子选择电极法测定钨尾矿中氟含量的熔剂类型和用量、熔融温度、熔融时间、总离子强度调节缓冲溶液用量、溶液澄清时间、共存元素干扰等实验条件进行了探讨,确定了最佳实验条件:称取试样0.10 g,加入1 g过氧化钠-3 g氢氧化钠混合熔剂,于650℃熔融15 min,冷却后热水浸提熔融物,静置过夜分取10 mL清液,加入15 mL总离子强度调节缓冲溶液定容至50 mL后测定。干扰实验表明:50 mL测定溶液中含有15 mL总离子强度调节缓冲溶液时,质量浓度不大于25 mg/L的Al^(3+)、30 mg/L的Fe^(3+)、25 mg/L的Ca^(2+)、5 mg/L的Mg^(2+)、10 mg/L的Zn^(2+)对质量浓度为1.4 mg/L的F^(-)测定影响可以忽略不计。实验结果表明,标准曲线线性相关系数为0.9998,方法检出限为0.0016%,相对标准偏差(n=7)为0.58%~1.35%,加标回收率为96%~103%。方法检出限、精密度和准确度均满足钨尾矿中氟的测定需求,为钨尾矿氟污染监测提供了可靠的数据支撑。

At present,there is no corresponding standard method for the determination of fluorine in tungsten tailings.In order to accurately determine the fluorine content in tungsten tailings,the type and amount of flux,melting temperature and time,total ionic strength adjustment buffer solution amount,precipitation and standing conditions such as time and interference of coexisting elements are discussed.The optimum experimental conditions are determined as follows,the sample weight of 0.10 g,addition of 1 g sodium peroxide-3 g sodium hydroxide mixed flux,melting time 15 min at 650℃,hot water extraction after cooling,10 mL clear solution,addition of 15 mL total ion strength adjusting buffer solution to 50 mL.The interference experiment result shows that when 50 mL of the assay solution containing 15 mL of total ionic strength adjustment buffer solution,the mass concentrations of Al^(3+),Fe^(3+),Ca^(2+),Mg^(2+),Zn^(2+)are not more than 25 mg/L,30 mg/L,25 mg/L,5 mg/L and 10 mg/L,have negligible effects on the determination of F^(-)at a mass concentration of 1.4 mg/L.The experimental result indicates that the linear correlation coefficient of the standard curve is 0.9998,the detection limit of the method is 0.0016%,the relative standard deviations(RSD,n=7)are between 0.58% and 1.35%,and the recovery rates of standard addition are between 96% and 103%.The detection limit,precision and accuracy of the analysis method all meet the requirements for the determination of fluorine in tungsten tailings.It provides the reliable data support for monitoring fluorine pollution in tungsten tailings.