EDTA滴定法测定钒渣中氧化钙

通过试验,确定了盐酸、硝酸、高氯酸分解钒渣样品,或碳酸钠-硼酸混合熔剂高温熔融样品后酸浸取的样品分解方式。在硝酸介质中,向试液中加入0.3～0.5 g氯酸钾,使锰形成二氧化锰沉淀,过滤沉淀后,在酸性条件下用无水乙醇将滤液中的钒还原为钒,用氨水调节pH 6~7,绝大部分的钒和铁、钛、铝、稀土等可生成沉淀,沉淀物经过滤被分离。调节滤液pH 7后,加入少量铜试剂分离残余的钒和金属离子,分取试液采用EDTA滴定法测定钒渣样品中的氧化钙含量。随机抽取一个钒渣样品,采用混合熔剂熔融处理样品后进行EDTA滴定法分析,11次测定结果的相对标准偏差为3.1%。对钒渣实际样品中的氧化钙量进行测定,结果与行业标准(YB/T 547.3-1995火焰原子吸收光谱法和高锰酸钾容量法测定氧化钙含量)的测定值一致;对钒渣标准样品进行分析,测定值与认定值一致。

Determination of calcium oxide in vanadium slag by EDTA titrimetric method

Through the experiment, the sample decomposition method was established,which used the HCl, HNO₃, HClO₄ to decompose vanadium slag sample, or used the mixed flux of Na₂CO₃-H₃BO₃ to fuse vanadium slag sample and then leached by acid. In nitrate acid medium, 0.3-0.5 g potassium chlorate was added to make Mn²⁺ form MnO₂ precipitate, which was removed by filtration. Then under acidic conditions, vanadium  was reduced to vanadium  using anhydrous alcohol. Ammonia was added to adjust pH 6-7,so that most vanadium  and metal ions such as iron, titanium, aluminum and rare earth metal ions may form precipitation, which may be separated by filtration. After adjusting the test solution to pH 7, a small amount of DDTC was added to separate the residual vanadium and metal ions,then calcium oxide content in the solution was measured by EDTA titrimetric method. A randomly selected vanadium slag sample was fused by mixed flux,and determined by EDTA titrimetric method,which the relative standard deviation(RSD%,n=11) was 3.1%.The determination results of proposed method agreed well with those of industry standard (YB/T 547.3-1995 Methods for chemical analysis of vanadium slag: the flame atomic spectrometric method and the permanganimetric method for the determination of calcium oxide content). CaO in reference materials of vanadium slag were determined,and the results were consistent with the certified values.