Transport Wilke-Chang equation

Wilke-Chang equation depicts that the diffusion coefficient of the forward transported M L complex shonld be much lower as compared to the backward transported bare ligand molecules due to smaller molar volume of the latter. This fact implies that the concentration of ligand at the aqueous feed-membrane interface will always be in excess because... 

In all forms of liquid membrane configurations, the transport efficiency can be changed based on the nature of the organic extractant, feed and receiver phase compositions and the viscosity of the membrane phase. Also, the nature of the diffusing species is important as the diffusion coefficient is dependent on the molar volume of the diffusing species, as per the Wilke-Chang equation (Wilke et al, 1955) ... 

The bulk diffusion coefficient Db obtained from membrane transport can differ from the Stokes-Einstein equation and Wilke-Chang relation. Both equations are valid under free-isotropic conditions, whereas the diffusion through the membrane can be reduced by an additional resistance of the pores 31). Significant reduction of the diffusion process takes place when pores are less then 10 times larger than the diffusing species. 

At higher temperatures, both the diffusion and decomplexation processes are accelerated, and transport rates increase. The transport parameters D, and were determined at elevated temperatures. The diffusion coefficient increases, while the extraction coefficient decreases with increasing temperature. correlates well with T/v as described by the Stokes-Einstein equation and Wilke-Chang relation. 

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