Title: Water Permeability and Water/Salt Selectivity Tradeoff in Polymers for Desalination

Journal: Journal of membrane science

Authors: Geoffrey M. Geise1, Ho Bum Park1,2*, Alyson C. Sagle1, Benny D. Freeman1, and James E. McGrath3

1Department of Chemical Engineering and Center for Energy and Environmental Resources,
University of Texas at Austin, Austin, TX 78758
2Laboratory for Energy & Environmental Resources and Chemical Engineering, Hanyang
University, Seoul 133-791, Korea
3Macromolecular and Interfaces Institute and Chemistry Department, Virginia Polytechnic
Institute and State University, Blacksburg, VA 24061

The original and creativity of paper: The paper intended to identify the relationships between water permeability and water/salt selectivity as well as water bound behavior. Moreover, they examine the relationships between water diffusivity and water/salt diffusivity selectivity water solubility as well as water/salt solubility selectivity. The obtained results can be applied on the development of desalination material design parameters (i.e., structure and property of membrane).


Summary:

?    Generally, the performance of desalination process is normally presents as water flux and salt rejection which revealed correlation between those parameters. However, both parameters are material properties independent due to they are influenced by sample size and measurement variables. Therefore, in practical, water permeability and water/salt permeability selectivity are used instead of water flux and salt rejection, respectively. 

?    Based on the experimental results, it is shown that a tradeoff relation and upper bound are observed when water and salt transport data are presented on a log-log plot of water permeability versus water/NaCl permeability selectivity. High water/NaCl permeability selectivity if influenced by water/NaCl solubility and diffusivity selectivity, whereas the dominant factor is diffusivity selectivity.

?    Polymer with high permeability to water possible to have low ability to separate water from mixtures with salt. 
?    
?    Tradeoff between water diffusion coefficient and water/salt diffusion selectivity provided tradeoff behavior between water permeability and water/salt permeability selectivity

?    Based on the data from desalination process, permeability and selectivity basis revealed realistic picture of impact of the polymer material 


Application & further study: The obtained results from this study can be applied on the development of desalination material design parameters (i.e., structure and property of membrane).


By Monruedee Moonkhum
Email: moon@gist.ac.kr