催化动力学光度法测定锌尾矿中痕量铅

在高氯酸-邻苯二甲酸氢钾介质中,于90 ℃水浴中加热,发现铅(Ⅱ)对碘酸钾氧化核固红的褪色反应有催化作用,据此建立了催化动力学光度法测定痕量铅的新方法。通过正交试验和方差分析确定最佳实验条件为:8.0 mL 1 g/L核固红(NFR)溶液,2.5 mL 0.02 mol/L HClO₄,0.5 mL 0.02 mol/L邻苯二甲酸氢钾溶液和1.5 mL 0.02 mol/L KIO₃溶液。方法线性范围为4.0×10^-5～4.4×10^-3 g/L,检出限为3.0×10^-6 g/L。实验表明,该催化反应为假一级反应,表观活化能E_a = 29.762 kJ/mol,反应表观速率常数K = 1.2×10^-4 s^-1。方法用于本地锌矿尾矿中铅含量的测定,测定值与原子吸收光谱法基本一致,相对标准偏差(n=9)为1.5% ~2.1%,加标回收率为98% ~ 104%。

Catalytic kinetic spectrophotometric determination of trace lead in zinc mine tailings

A novel catalytic kinetic spectrophotometric determination of trace lead was established based on Pb(Ⅱ) had catalytic effect on the fading reaction of nuclear fast red oxidized by potassium iodate in perchloric acid-potassium biphthalate medium at 90℃ water bath. The optical experimental conditions, which were obtained by orthogonal experiments and variance analysis, were as follows: 8.0 mL of 1 g/L nuclear fast red solution, 2.5 mL of 0.02 mol/L perchloric acid, 0.5 mL of 0.02 mol/L potassium acid phthalate solution and 1.5 mL of 0.02 mol/L potassium iodate solution. The linear range of this method was 4.0×10^-5-4.4×10^-3 g/L and detection limit was 3.0×10^-6 g/L. It was found that the catalytic reaction was pseudo-first-order reaction with apparent activation energy of 29.762 kJ/mol and apparent rate constant of 1.2 ×10^-4 s^-1.When the proposed method was applied to the determination of lead in local zinc mine tailings, the results were consistent with those obtained by atomic absorption spectrometry. The relative standard deviation (n=9) was 1.5 % -2.1 %, and the recoveries were between 98 %-104 %.