Microstructure Regulation of the Reverse Osmosis Membrane to Improve the Boron Removal Performanc

Thin aromatic polyamide composite reverse osmosis membranes ( TFC) were modified by grafting polyethyleneimine ( PEI) chains and 4-azidobenzoic acid ( ABA) molecules. Attenuated total reflectance Fourier transform infrared spectroscopy ( ATR-FTIR) and X-ray photoelectron spectroscopy ( XPS) were used to analyze the chemical composition and structure of the active separation layer. Then the hydrophobicity and charge of the reverse osmosis membrane were measured by static water contact angle instrument and Zeta potentiometer, the surface morphology was observed by scanning electron microscopy( SEM) and atomic force microscopy ( AFM). Finally, the separation performance of the reverse osmosis membranes was tested in brackish water and seawater condition, respectively. The experimental results show that the separation layers of the reverse osmosis membrane become denser after modifying with PEI and/or ABA, and correspondingly the mass transfer resistance of boron permeation through reverse osmosis membranes is increased. The boron retention rate of the TFC-PEI-ABA membrane modified by both PEI and ABA reach 90. 45%, which meets the requirements of World Health Organization( WHO) for water quality.