Study on Separation/Enrichment and Determination of Mercury(II) using Microcrystalline Thymolphthalein Loaded with Ternary Association Complex

The paper presents a novel method for the separation/enrichment of Hg²⁺ using microcrystalline thymolphthalein loaded with ternary association complex prior to the determination by spectrophotometry. The effects of different parameters, such as the dosages of KI and dodecyl trimethyl ammonium bromide (DTAB) and thymolphthalein, various salts and acidity etc. on the enrichment yield of Hg²⁺ have been investigated to select the experimental conditions. The results showed that in the presence of 1.0 g NaCl, when the dosage of 0.1 M KI solution was 1.50 mL and 5.0 × 10^?3 M dodecyl trimethyl ammonium bromide (DTAB) solution was 1.50 mL respectively, the water‐insoluble ternary association complex of (DTAB)₂(HgI₄) which produced by Hg²⁺ and I^?, DTAB cation (DTAB⁺) was quantificationally absorbed on the surface of microcrystalline thymolphthalein Therefore, Hg²⁺ was separated completely from Zn²⁺, Mn²⁺, Ni²⁺, Co²⁺, Fe³⁺, Al³⁺, Pb²⁺, Bi³⁺ and Cr³⁺ etc. by contolling acidity. The possible enrichment mechanism of Hg²⁺ was deduced. The proposed method has been successfully applied to the determination of Hg²⁺ in the sample of industrial waster water, and the results agreed well with the dithizone method. The recoveries were 94.5%～106.5%, and the RSD was 2.0%～2.8%.