Rapid Determination of Lead in Barium-bearing Ores by EDTA Compleximetry
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摘要: 对于含钡铅矿石中铅的测定，采用EDTA容量法由于在分析流程中生成硫酸铅钡复盐使铅的分析结果偏低；采用钡铬酸铅容量法可以消除钡的干扰，但分析方法流程繁杂，耗时长。本文对现有的EDTA容量法进行改进，建立了一种快速测定含钡铅矿石样品中铅含量的分析方法。样品在盐酸体系中溶解，用硫酸沉淀分离可溶性钡离子，再用硫酸沉淀铅，所得的硫酸铅沉淀用pH=5.7的乙酸-乙酸钠缓冲溶液溶解，EDTA络合滴定法测定铅的含量。分析结果表明，盐酸用量为40 mL，50%硫酸用量为2滴时可以消除钡对铅测定的干扰，样品分解后硫酸铅沉淀20 min即可分离测定。本法的测定值与国家标准方法的测定值基本一致，方法精密度为0.1%~0.8%。方法中沉淀放置时间只有20 min，与国家标准方法和其他方法的沉淀放置时间(4 h或过夜)相比较，缩短了样品处理流程，满足了矿山企业选冶生产现场样品的快速检测要求。Abstract: For the determination of lead content in barium-bearing samples by the EDTA volumetric method, the lead analysis result is low due to the presence of lead sulfate and barium sulfate double salt formed during the analysis process. The interference of the barium can be eliminated by using the lead and barium chromate volumetric method, but the analysis process is complicated and time-consuming. Consequently, a rapid determination method based on the improved EDTA volumetry has been established and is documented in this paper. Barium-bearing ores are dissolved in a hydrochloric acid system with sulfuric acid precipitation to remove soluble barium ions. The acid solution is then evaporated and the lead sulfate separated by precipitation from other impurities with sulfuric acid solution. The lead sulfate precipitations are dissolved by acetic acid-sodium acetate buffer solution at pH of 5.7. The content of lead is analyzed by EDTA complexometric titration. Through the experiment, the amount of hydrochloric acid was 40 mL and the interference from barium was eliminated by 2 drops of 50% sulfuric acid. Lead sulfate was separated and measured after 20 min when the sample was decomposed. The influence of barium content on samples, to determine lead content was also studied. According to different barium contents of lead ore samples, the precisions (RSD, n=7) wer 0.1%-0.8%, and the results were consistent with those of the national standard method. The results show that the method can shorten the sample processing workflow, which can satisfy plant commissioning and processing requirements.
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Key words:
- barium-containing ores /
- lead /
- EDTA Compleximetry
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表 1 盐酸对硫酸铅钡溶解的效果
Table 1. Effect of HCl on Pb-Ba sulfate dissolution
取样量
m/gw(Pb)/% 回收率/% 理论值 测定值 0.3000 38.62 38.55 99.8 0.4000 38.62 38.62 100.0 
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表 2 沉淀钡时盐酸用量对铅测定的影响
Table 2. Effect of HCl concentration on Pb determination
V(盐酸)/mL m(Pb)/mg 回收率/% 加入量 测得量 10 150 148.2 98.8 20 150 149.3 99.5 30 150 149.8 99.9 40 150 149.8 99.9
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表 3 沉淀钡时50%硫酸用量对铅测定的影响
Table 3. Effect of 50% H2SO4 concentration on Pb determination
50%硫酸
用量/滴m(Pb)/mg 回收率/% 加入量 测得量 1 150 149.8 98.9 2 150 149.6 99.7 4 150 149.6 99.7 6 150 149.5 99.7
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表 4 残余王水对铅沉淀的影响
Table 4. Effect of residual acid on Pb determination
V(王水)/mL m(Pb)/mg 回收率/% 加入量 测得量 0 150 149.9 99.9 1 150 149.7 99.8 2 150 149.6 99.7 4 150 149.2 99.5
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表 5 放置时间对铅测定的影响
Table 5. Effect of standing time on Pb precipitation
放置时间
t/minm(Pb)/mg 回收率/% 加入量 测得量 0 150 149.2 99.5 10 150 149.6 99.8 20 150 149.9 99.9 60 150 149.9 99.9 240 150 149.9 99.9
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