硫酸铵存在下碘化钾-丙醇双水相体系萃取分离镉及其应用

Extraction of cadmium by potassium iodide-propanol aqueous two-phase systems in the presence of ammonium sulfate and its application

试验研究了在硫酸铵存在下碘化物-丙醇双水相体系萃取分离镉的行为及最佳分相条件。考察了络合剂的选择、KI和(NH_4)_2SO_4用量、pH值等反应条件对萃取率的影响。结果表明,体系中加入0.5mL 200g/L KI溶液和1.5g(NH_4)_2SO_4、在pH值为1~5的介质中,无需使用三苯甲烷类阳离子染料,Cd^(2+)与KI络合生成的CdI_4^(2-)络离子可与丙醇阳离子生成离子缔合物,进而被萃取到丙醇上层。实验方法通过火焰原子吸收光谱法(FAAS)检测萃取后丙醇相中Cd的含量得到证实。Cd^(2+)质量浓度在0.20~2.50μg/mL范围内呈线性关系,相关系数r=0.996 51。干扰试验表明,在±5%的误差范围内,铅烟灰样品中最大质量分数范围内的共存元素(8%Zn、2.5%Fe、2%Cu、0.7%In)不干扰Cd的测定。实验方法应用于铅烟灰中Cd的测定,结果的相对标准偏差(RSD,n=5)在1.8%~2.3%之间,加标回收率在90%~92%之间。

In the presence of ammonium sulfate, the extraction behavior of Cd2＋ was studied by potassium iodide-propanol aqueous two-phase in the presence of ammonium sulfate, and the optimal conditions of phase separation were selected. The reaction conditions, such as the selection of complexant, the amount of KI and （NH4）2SO4, pH value, on the extraction rate were investigated. Results showed that, without the need of chromogenic agent, CdI4^2 can be extracted into the upper layer of propanol by the formation of ion association with propanol cations, in the medium of pH 1-5, when 0.5 mL of 200 g/L KI solution and 1.5 g of （NH4）2SO4 were added. The method was verified through the determination of Cd in the extracted propanol phase by flame atomic absorption spectrometry. The mass concentration of Cd2＋ was linear in the range of 0.20-2.50 μg/mL. The correlation coefficient is 0.996 51. The interfering experiment shows that Cd^2＋ can be dissociated completely from the coexisting elements in the maximum mass fraction range of lead dust （8%Zn、2.5%Fe、2%Cu、0.7%In）, within the error range of ±5%. The proposed method was successfully applied to the determination of cadmium in lead dust. The relative standard deviation （RSD,n=5） was between 1.8%-2.3%, and the recovery of standard addition was between 90%-92%.