亚甲基蓝-高碘酸钾催化动力学光度法测定钼尾矿中钼

实验研究发现,在硫酸存在的情况下,高碘酸钾可以氧化亚甲基蓝褪色,钼对该褪色反应有催化作用,据此,建立了催化动力学光度法测定钼尾矿中钼的新方法。实验表明:当显色体系中亚甲基蓝浓度为0.012 g/L、硫酸浓度为0.001 mol/L、高碘酸钾浓度为0.000 4 mol/L时,于60 ℃加热13 min,钼在0.02～0.6 mg/L范围内与吸光度变化值呈良好的线性关系,方法检出限为0.05 mg/L。在最佳实验条件下,催化体系的表观活化能E_a=47.31 kJ/moL,反应速率常数k=3.5×10^-4/s。方法应用于3个不同地区钼尾矿中钼的测定,测定结果与原子吸收光谱法(AAS)吻合,相对标准偏差(RSD,n=11)为2.1%～2.9%,回收率为97%～102%。

Determination of molybdenum in molybdenum tailing by methylene blue-potassium periodate catalytic kinetic spectrophotometry

It was found through experiments that potassium periodate could oxidize methylene blue for fading in presence of sulfuric acid. Based on molybdenum had catalytic effect on this fading reaction, a new determination method of molybdenum was established in molybdenum tailing by catalytic kinetic spectrophotometry. The results showed that when the concentration of methylene blue, sulfuric acid and potassium periodate in coloring system was 0.012 g/L, 0.001 mol/L and 0.000 4 mol/L, respectively, the concentration of molybdenum in range of 0.02-0.6 mg/L exhibited good linearity to the absorbance change after the coloring system was heated at 60 ℃ for 13 min. The detection limit of method was 0.05 mg/L. Under the optimized experimental conditions, the apparent activation energy of catalytic system was E_a=47.31 kJ/mol, and the reaction rate constant was k=3.5×10^-4/s. The proposed method was applied to the determination of molybdenum in molybdenum tailings from three different areas. The results were consistent with those obtained by atomic absorption spectrometry(AAS). The relative standard deviation (RSD, n=11) was 2.1%-2.9%, and the recoveries were between 97% and 102%.