Na2EDTA返滴定法测定铜冶炼烟尘中镉

铜冶炼烟尘中含有较高含量的铅、铜、砷、铝、铁、锑、铋等元素,对滴定法测镉产生干扰。采用氟化铵-盐酸-硝酸-高氯酸分解试样,用氢溴酸除去砷、锑、锡等干扰元素。硫酸铅沉淀分离铅,氨水沉淀分离铁、铋、部分铝等共存元素,在稀硫酸介质中加入硫代硫酸钠使铜离子以硫化亚铜状态从溶液中分离,滤液中加入过量的Na₂EDTA标准滴定溶液,加入氟化钾掩蔽剩余铝,在pH 5.5~5.6的盐酸-六次甲基四胺缓冲溶液中,以二甲酚橙为指示剂,用锌标准滴定溶液返滴定。测得结果为锌、镉合量,扣除锌量,即为镉量。优化了氨水用量、氟化钾用量等实验条件,建立了Na₂EDTA返滴定法测定铜冶炼烟尘中镉含量的方法。方法用于测定铜冶炼烟尘中镉,结果与电感耦合等离子体原子发射光谱法(ICP-AES)一致,结果的相对标准偏差(RSD,n=11)为0.56%~0.92%。按照实验方法对铜冶炼烟尘样品进行加标回收试验,回收率为99.6%～100.2%。

Determination of trace bismuth in pure zirconium by hydride generation-atomic fluorescence spectrometry

Pure zirconium is widely used in aerospace, navigation, nuclear reactor and other fields. As bismuth greatly influences on the corrosion resistance of zirconium, it is very important to accurately determine the bismuth content in pure zirconium. An analysis method for the determination of trace bismuth in pure zirconium by hydride generation-atomic fluorescence spectrometry (HG-AFS) was established. The results showed that pure zirconium sample could be completely dissolved with HCl-HNO₃-HF. The determination of bismuth in pure zirconium by HG-AFS was realized under the following experimental conditions: thiourea-ascorbic acid was used as the pre-reducing agent; the potassium borohydride solution (12g/L) was selected as the reducing agent; 20% (volume fraction) hydrochloric acid was used as determination medium; the negative high voltage of photomultiplier tube was 300V; the lamp current was 80mA. It was found that the interference of zirconium matrix with the determination of bismuth could be ignored, so the matching of zirconium matrix was not required for the preparation of standard solution series. The linear range of calibration curve for bismuth was 0.00005%-0.0010%, and the linear correlation coefficient was r=0.9998. The limit of detection was 0.000002%. The contents of bismuth in three pure zirconium samples were analyzed by the proposed method. The relative standard deviations (RSD, n=10) of determination results were between 0.29% and 0.75%. The found results were consistent with those obtained by inductively coupled plasma mass spectrometry (ICP-MS).