通过铅核磁共振光谱(^(207)Pb-NMR)研究Pb(OH)_4^(2-)+OH^-Pb(OH)_5^(3-)的热力学平衡

A study of the thermodynamic equilibrium Pb(OH)_4^(2-)+OH^-Pb(OH)_5^(3-) by ^(207)Pb-NMR

采用铅核磁共振光谱(207Pb-NMR)研究了在不同温度、有无添加剂的碱性溶液中Pb(Ⅱ)粒子的水解产物,论证了配体电负性对207Pb-NMR与对1H-NMR相反的影响,计算了不同温度的表观平衡常数以及活化能变。实验结果表明Pb(Ⅱ)水解产物可能为构成平衡的Pb(OH)2-4与Pb(OH)3-5;升温导致207Pb共振移向低场;添加剂对207Pb化学位移的影响很小,对核磁峰宽的影响主要来自于水解粒子外部环境的变化。

The hydrolysis products of Pb(Ⅱ) ions have been studied in alkaline electrolytes with or without the presence of additives at different temperatures by using lead-207 nuclear magnetic resonance spectroscopy(207PbNMR). This paper demonstrates the effect of the electronegativity of the donor atom on207Pb-NMR,which is opposite to the effect observed in1H-NMR. The apparent equilibrium parameters at different temperatures and the change in activation energy have been calculated. The experimental results indicate that hydrolysis products under the experiment conditions may be a mixture of Pb( OH)2-4and Pb( OH)3-5in thermodynamic equilibrium. The207 Pb resonance shifts to low-field with increasing temperature. The additive has a small influence on the chemical shift of the207 Pb resonance,while the effect of the additive on the line-width of the207 Pb resonance may be primarily induced by the change in the outer sphere environment of the Pb(Ⅱ) species.