关键词:

D2EHPA, Cr(Ⅲ), 反萃, 陈化现象, 动力学

Abstract:

In recent years, the extraction characteristics of Cr(Ⅲ) with the acidic organophosphate extractants have been studied, while the researches on the back-extraction of Cr(Ⅲ) were seldom reported.The acidic extractants loaded with Cr(Ⅲ) condense easily and form stable complex which can be hardly back-extracted to the aqueous phase, i.e., the extractant can’t be regenerated.This is so-called ‘aging’.In this paper, 10% D2EHPA/10% 1-octanol/kerosene was used as the solvent, 0.6 mol·L^-1 H₂SO₄ was used as the back-extraction agent, and the back-extraction was used as a method to study the aging process.The effect of Cr(Ⅲ) concentration and temperature on the aging process was investigated.The condensation reaction mechanism and a mathematic model were proposed.The aging dynamic parameters were simulated on the basis of this model, and the activation energy of aging process was obtained by regressing the experimental data.The results showed that the condensation reaction rate increased with temperature quickly.The reaction order was 1.57 and the rate constants varied between 2.49×10^-3 and 4.06×10^-2.The activation energy of aging process was low enough for a spontaneous reaction (43.0 kJ·mol^-1）.Furthermore, the operating temperature of below 23℃ in an industrial process is suggested on the condition of aging efficiency below 3% within 30 min.

Key words:

D2EHPA, Cr(Ⅲ), 反萃, 陈化现象, 动力学