Chem. J. Chinese Universities ›› 2021, Vol. 42 ›› Issue (6): 2008.doi: 10.7503/cjcu20200746

• Polymer Chemistry • Previous Articles     Next Articles

Effects of Co-reagent for Improving the Performance of Polyamide Composite Reverse Osmosis Membrane

YAN Tingting1, ZHANG Na1, LI Qiang1(), LI Zhenhua2, LI Chunhui1,2, LI Xue1,2, YU Ru1, WANG Rui1, WANG Jihua1, CAO Zanxia1()   

  1. 1.Institute of Biophysics,Shandong Key Laboratory of Biophysics
    2.College of Physics and Electronic information
  • Received:2020-10-11 Online:2021-06-10 Published:2021-06-08
  • Contact: LI Qiang E-mail:liqiang810108@126.com;qiayilai@mail.ustc.edu.cn

Abstract:

In a bid to improve the performance of polyamide composite reverse osmosis membranes(PA-RO-xx represents DMAc concentration), NN′-dimethylacetamide(DMAc) was applied as co-reagent added into the aqueous m-phenylenediamine solution for interfacial polymerization reaction with trimesoyl cloride. Characterization of the PA-RO-x membranes by X-ray photoelectron spectroscopy(XPS) and attenuated total reflectance Fourier transform infrared(ATR-FTIR) spectroscopy confirmed that with the increase of DMAc concentration, the content of cross-linked amide linkages in PA-RO-x membranes increased relative to the li-ner pendant carboxylic acid groups. By the field emission scanning electron microscope(FE-SEM) and atomic force microscope(AFM), it is obviously showed that the surface morphology gradually changed and the surface roughness of composite reverse osmosis membranes increased as the increase of DMAc content. The static water contact angle measurement with sessile drop method revealed that the hydrophilicity of the composite reverse osmosis membranes was enhanced after DMAc was added. According to the above mentioned charac-terization results, it was confirmed that DMAc play a key role that could effectively reduce the immiscibility between aqueous phase and oil phase, and help to improve the diffusion rate of m-phenylenediamine from aqueous phase to n-hexane for accelerating the reaction between m-phenylenediamine and trimesoyl cloride. At the same time, the increase of the linkages of cross-linked amide can be as hydrogen-bond sites, which can be beneficial for water molecules penetrate through the polyamide composite reverse osmosis membranes quickly without considerable losing the salt rejection. The higher the surface roughness of the membranes, the higher the permeate flux. The water permeate flux and NaCl rejection of PA-RO-5.2(DMAc concentration is 5.2%, mass fraction) reached 66.1 L/m2·h and 98.7%, respectively, for 2 g/L NaCl under 1.6 MPa. Compared with the polyamide reverse osmosis composite membrane without DMAc addition, the permeate flux of PA-RO-5.2 increased by 115% and the desalination rate decreased by 0.9%.

Key words: Polyamide composite reverse osmosis membrane, Co-reagent, N, N′-dimethylacetamide, Per-meate flux, Salt rejection

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