自动电位滴定硼浓度方法在MOFs对硼同位素分离效果测定中的应用

金属 有机骨架（MOFs）材料作为吸附剂具有吸附硼同位素的潜力，为系统研究硼同位素效应，本文建立测定硼酸溶液中硼浓度的自动电位滴定法，以三种MOFs为例测定其对硼同位素的分离效果。采用弱酸强化法，甘露醇用量为理论用量的4倍，硼酸标准物质的测量值与参考值之差最小（-0.000 13 g），方法的测量不确定度为0.000 2~0.000 8，测量精度为0.10%~0.40%，方法有效、可靠。应用建立的自动电位滴定法测定吸附前、后硼酸溶液的硼浓度，用MC-ICP-MS测定吸附前、后硼酸溶液的硼同位素丰度比¹⁰B/¹¹B，以Cu-MOF-OCH₃、UiO-66-NH₂、MIL-101(Cr)-2,3-OH三种MOFs材料为例，测定其对硼同位素的静态分离效果。结果表明，Cu-MOF-OCH₃、UiO-66-NH₂和MIL-101(Cr)-2,3-OH对硼同位素的分离因子(S)分别为1.066、1.037和1.079，均大于商用树脂Amberlite IR743的S（1.027），其中，Cu-MOF-OCH₃对¹⁰B的10/11S>1，UiO-66-NH₂、MIL-101(Cr)-2,3-OH对¹¹B的^11/10S>1。本结果可为系统研究MOFs材料对硼同位素的分离效果提供参考。

Application of Automatic Potentiometric Titration of Boron Concentration in the Determination of Boron Isotope Separation Effect Based on MOFs

Metal-organic frameworks (MOFs) as adsorbents to separate boron isotope method is increasingly attractive. In order to systematically study the boron isotopic effect, an automatic potentiometric titration method for the determination of the boron concentration of boric acid in the solution was established, and taking several MOFs as examples to determine their separation effect on boron isotope. First, using weak acid fortification method, the dosage of mannitol was four times of the theoretical dosage. The difference between the measured value of the boric acid standard material and the reference value was the smallest (-0.000 13 g), the measurement uncertainty of the method was 0.000 2-0.000 8, and the measurement accuracy is 0.10%-0.40%,which made the method valid and reliable. Then, using established automatic potentiometric titration method to determine the boron concentration, using MC-ICP-MS to determine the boron isotope abundance ratio ^10/11B of the boric acid solution before and after adsorption, respectively. The static separation of boron isotopes by three MOFs, Cu-MOF-OCH₃, UiO-66-NH₂ and MIL-101(Cr)-2,3-OH, was determined as an example experiment. The results showed that the isotopic separation factors S of Cu-MOF-OCH₃, UiO-66-NH₂ and MIL-101(Cr)-2,3-OH for boron isotopes were 1.066, 1.037 and 1.079, respectively, which were all larger than that of the commercial resin Amberlite IR743 (1.027). Among them, Cu-MOF-OCH₃ has a positive isotopic effect on 10B cause of 10/11S＞1, and the UiO-66-NH₂, MIL-101(Cr)-2,3-OH have a positive isotopic effect on ¹¹B cause of ^11/10S＞1. This provides a reference for the systematic study of the separation effect of MOFs on boron isotopes.