无汞重铬酸钾-自动电位滴定法准确测定矿石中的全铁含量
Accurate Determination of Total Iron in Ores by Automatic Potentiometric Titration without Potassium Dichromate
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摘要: 铁矿石样品采用Na2O2碱熔进行前处理,自动电位滴定法准确测定矿石中全铁的含量。对于样品溶液Fe3+的还原方式,考察了SnCl2-HgCl2、SnCl2、TiCl3、SnCl2-TiCl3四种方式,确定选用SnCl2-TiCl3联合还原,不仅避免了有毒试剂的使用,而且滴定终点电位突跃明显。自动电位滴定法的相对误差(RE)为0.13%,精密度(RSD)为0.22%,优于手动滴定法,避免了手动滴定受终点颜色判断误差、分析者水平等因素影响的不足。将建立的SnCl2-TiCl3-K2Cr2O7自动电位滴定法应用于6个铁含量大于30%的矿石标准物质分析,RE＜0.2%,RSD＜0.3%(n=10)。该方法对于钒钛磁铁矿样品GBW 07226a、GBW 07224无需分离,可直接测定,样品分解方法简单快捷,适用性强,样品不会飞溅且分解完全,适用于需要较高准确度的铁矿石尤其是高含量铁矿石样品的分析工作。Abstract: For iron ores, this paper discusses an alkali fusion method of sodium peroxide to resolve the ores without splash and complete decomposition. Four methods of reducing Fe3+ to Fe2+ are also discussed, using stannous chloride and titanium trichloride as this not only avoids the use of toxic reagents, but also has a clearly potential jump at the end of the titration. Finally, the manual titration method is replaced by an automatic potentiometric titration to avoid manual errors, such as the judgement of the end of titration by colour and the level of experience of the analyst. The relative error can be reduced to 0.13% and the relative standard deviation is 0.22%. A new SnCl2-TiCl3-K2Cr2O7 automatic potentiometric titration method has been developed. It has been applied to detect six National Standard Reference iron ore samples where the content of iron is higher than 30% and the relative error is lower than 0.2%, the relative standard deviation being lower than 0.3% (n=10). The magnetite GBW 07226a and GBW 07224 with high vanadium and titanium can be determined directly in one step. This new method is suitable to determine iron ores especially high content iron ores which require higher accuracy and is simple and fast to perform.
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