D2EHDTPA-TOA反协同萃取镉的速率方程

以恒界面池法研究了D2EHDTPA（二（2-乙基己基）二硫代磷酸）-TOA（三辛胺）反协同萃取镉的界面反应速率方程.萃取历程由若干个相转移（在本体相与界面相之间的物质转移）过程和若干个反应组成.萃取的速率方程为 r=1.42*10^-7Cd²⁺]^0.42BHA]^0.47/B]^0.85H⁺]^0.21 （mol•m^-2•s^-1） 探讨了萃取速率方程中非整数反应物级数的物理意义.Freundlich因子n越大,物质在界面层所受排斥力越大.萃取过程的表观活化能E=44.2 kJ•mol－1,萃取反应的焓变ΔH=72.9 kJ•mol－1.讨论了由不同的界面模型而导致不能通融的萃取动力学机理的问题.

Rate Equation of Antisynergic Extraction of Cadmium with D2EHDTPA-TOA

The kinetics of antisynergic extraction of cadmium with D2EHDTPA（di-(2-ethylhexyl)-dithiophosp-horic acid） -TOA（trioctylamine） under the condition of interfacial reaction controlling model was investigated by using an improved constant interfacial area stirred cell. The extraction course was composed of several interphase transfer processes (transfer between bulk phase and interfacial phase (or boundary phase)) and several chemical reactions. The extraction rate equation was : r=1.42*10^-7Cd²⁺]^0.42BHA]^0.47/B]^0.85H⁺]^0.21 （mol•m^-2•s^-1） The interfacial concentration was associated with the bulk concentration by using Freundlich adsorption equation. The concentration exponents in the extraction rate equation were decided by the two factors of the interfacial chemical reactions and the interphase transfer processes.The physical meaning of the fractional reaction order in the rate equation was analyzed. The bigger the Freundlich power n of a reactant, the more the repulsion exerted by the interfacial layer. The apparent extraction activation energy E=44.2 kJ•mol－1,the extraction enthalpy ΔH=72.9 kJ•mol－1. The inconsistency in extraction mechanism due to different interface models was also discussed.