纳米TiO2预分离/富集FAAS法同时测定Cr(Ⅲ)和Cr(Ⅵ)的研究

纳米材料是近年来受到广泛重视的一种新兴功能材料,具有一系列新异的物理化学特性和一些优于传统材料的特殊性能.其中一点是随着粒径的减小,表面原子数迅速增大,表面原子周围缺少相邻的原子,具有不饱和性,易与其他原子相结合而稳定下来,因而具有很大的化学活性.纳米材料对许多金属离子具有很强的吸附能力,是痕量元素分析较为理想的分离富集材料.文章利用火焰原子吸收法(FAAS)研究了纳米TiO2(金红石型)对Cr(Ⅵ)/Cr(Ⅲ)的吸附性能,并应用于水样中铬的形态分析.吸附体系中pH对Cr(Ⅵ)和Cr(Ⅲ)的吸附有很大影响,当pH＞6时,纳米TiO2对Cr(Ⅲ)的吸附率大于90%,而对Cr(Ⅵ)基本不吸附,从而达到二者的分离.pH 6.5微酸性条件下,纳米TiO2吸附Cr(Ⅲ),然后以2mol.L-1HCl洗脱,得到Cr(Ⅲ)的含量,剩余水溶液中测定Cr(Ⅵ)含量.该法测定Cr(Ⅵ)和Cr(Ⅲ)的检出限分别为57和41 ng·mL-1,RSD分别为2.6%和3.4%(2.0μg·mL-1Cr,n=6),Cr(Ⅵ)和Cr(Ⅲ)的线性范围分别为0～9.0和0.1～10μg·mL-1.该法选择性好,大多数共存离子不干扰测定.该法简便快速,用于工业废水、地表水中铬的形态分析,结果较满意.

Combination of Separation/Preconcentration Based on Nanoscale TiO2 and FAAS for the Simultaneous Determination of Cr(Ⅲ)/Cr(Ⅵ)in Water

The nanometer-sized materials have attracted much interest of analysts in recent years because of their special physicschemistry characteristics. As the scale decreases to nanometer grade, the number of atoms on the surface increases remarkably, resulting in the unsaturation. This makes the nanometer-sized materials have a high adsorptivity for the metal atoms. In the present paper, the nanometer-sized TiO2 was applied in the separation and preconcentration of Cr(III) and Cr(VI) in water. The influence of pH on the adsorption of Cr(III) and Cr(VI) was studied. When pH is larger than 6, 90%, Cr(III) is adsorbed onto the nanometer-sized material surface, while is basically not adsorbed in aqueous solution. Therefore, the separation of Cr(III) and Cr(VI) is achieved. At the pH of 6.5, Cr(III) was adsorbed by nanometer-sized TiO2 and desorbed with 2.0 mol x L(-1) HCl, in which the Cr(III) could be preconcentrated. The Cr(III) solution, as well as the Cr(VI) aqueous solution was determined by FAAS. The detection limits of Cr(M) and Cr(VI) were 41 and 57 ng x mL(-1), respectively. And the linear ranges for Cr(III) and Cr(VI) were 0-9.0 microg x mL(-1) and 0.1-10 microg x mL(-1) with a RSDs of 2.6% and 3.4% (n=6, c = 2.0 microg x mL(-1), respectively. This method was applied in the simultaneous determination of Cr(III) and Cr(VI) in the industrial wastewater and river water, and the satisfactory recovery results were obtained.