电渗强化多孔介质孔内流动及传质

建立了电场中多孔介质孔内流动模型 ,通过计算比较了Poiseuille流和电渗流对孔内流动的贡献 ;提出“有效扩散系数”来定量描述电渗对多孔介质孔内传质过程的强化作用 ;建立了电色谱理论塔板高度模型 ,比较了Poiseuille流和电渗流对色谱理论塔板高度的影响 .计算结果表明采用Poiseuille流强化孔内传质的方法仅适用于孔径大于 5 0 0nm的大孔颗粒 ;而电渗流则可提高不同孔径的介质孔内的传质 ,降低色谱分离理论塔板高度 ;依据Yoshida模型计算了不同的有效扩散系数下的吸附穿透曲线以揭示电场强度对电色谱吸附行为的影响 ,理论预期与实验结果一致

ELECTROOSMOSIS ENHANCED INTRAPARTICLE LIQUID FLOW AND MASS TRANSPORT

A mathematical model describing the intraparticle flow contributed by Poiseuille flow and electroosmosis in the electrochromatography was established, which showed that the contribution of electroosmotic flux became dominant when the pore diameter to particle diameter decreased. A new concept in terms of effective diffusivity was proposed to quantify the electroosmosis enhanced intraparticle mass transport. The height equivalent of a theoretical plate (HETP) of electrochromatography was calculated as function of the effective diffusivity. The effects of Poiseuille flow and electroosmosis on the magnitude of HETP was investigated, respectively. It was shown that enhancement of intraparticle mass transport by Poiseuille flow, as shown by the reduction of the magnitude of HETP, could only obtained for those large pore particles characterized by pore diameter over 500 nm. While the introduction of intraparticle electroosmosis led to the increase in the effective diffusivity and the reduction of the HETP, both of which were dependent on electric field strength and were independent of pore diameter. Prediction of the breakthrough behavior of electrochromatography was attempted using the model developed by Yoshida. The predicted breakthrough curve as a function of the electric field strength was in good consistency with those experimental results obtained in different electrochromatography systems. This demonstrated the validity of the theoretical results obtained by the present study.