#### Investigating electrostatic repulsive distance of electrically conductive polymer as reverse osmosis membrane for seawater desalination: A theoretical calculation

C.-M. Chang*, C.-H. Huang, Y.-T. Chiu, Y.-C. Chen, ITRI - Industrial Technology Research Institute, Taiwan

The reverse osmosis (RO) thin film encounters some troubles likes low flux, high operation pressure and high energy consumption in the application of seawater desalination. Finding out the electrostatic repulsive distance between two surfaces is a valuable assistance to design microporous diameter of RO films for increasing desalination efficiency.

A series of theoretical calculations are developed to analyze poly(4-vinylbenzyl sulfonate) and poly(4-vinylpyridine) RO films. First, we performed a semi-empirical calculation to get pK_{a} and pK_{b} of materials by using partial charge, and the materials dissociation degree in different pH value of water and the surface charge density of films were investigated by using Henderson-Hasselbalch equation.

Then, based on diffuse double layer theory, the counterion and co-ion concentration profile near the surface at various pH value of water can be related to the surface charge density. The salt rejection ratio we considered is 95%. Therefore, we could find out the electrostatic repulsive distance by doing curve line integral of co-ion concentration to half of 0.03M (0.6M in normal seawater). The results showed that...

**Session: **M4 - Short Oral + Poster Presentations

**Day:** 12 October 2016

**Time: ** 14:45 - 16:45 h

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