Enhanced desalination performance and arsenate removal using semi-aromatic polyamide-based pervaporation membranes by modifying with amino-acids via interfacial polymerization

In this study, the semi-aromatic polyamide membranes were synthesized by the interfacial polymerization between piperazine (PIP) monomers in the water phase and Benzene-1,3,5-tricarbonyl chloride in the organic phase. To further modify the semi-aromatic pervaporation membrane, the two amino acids, glycine, and l-lysine, were mixed with PIP monomers for interfacial polymerization. The morphology and physicochemical properties of the synthesized membranes were analyzed using Fourier transform infrared (FTIR), field emission scanning electron microscope (FE-SEM), atomic force microscope (AFM), and contact angle measurements. The results show that the semi-aromatic polyamide membranes modified by the two amino acids possess a higher hydrophilic surface and lower thickness compared to the unmodified membrane. Additionally, the permeation flux of the semi-aromatic polyamide membranes was improved by 18.6% and 38.5% as modified with glycine and l-lysine, respectively, at the operating temperature of 70 degrees C when the rejection of both NaCl and arsenic are higher than 99.8%. Furthermore, the operating temperature significantly influenced the permeation flux, while the salt rejections were insignificantly affected. The permeation flux increases by 3.2- and 4.0-folds for glycine and lysine-modified membranes, respectively, when elevating the feed temperature from 40 degrees C to 70 degrees C. The highest permeation flux of 29.5 kg m-2 h-1 with a 5 wt% NaCl rejection of 99.8% was obtained at 70 degrees C by using 0.3 wt% l-lysine modified polyamide (PA) membrane. For elimination of 1.5 mg L-1 As solution at the feed temperature of 70 degrees C, such l-lysine modified PA membrane exhibited the permeation flux of 30.5 kg m-2 h-1 and As rejection of 99.6%, respectively. This work provides a cost-saving, facile, and eco-friendly preparation method for effectively improving the permeation flux while not sacrificing the high rejection of salts of the modified membranes. This concept is to modify the semi-aromatic PA thin-film composite membrane by adding glycine and lysine into the PA selective layer, resulting in increasing the hydrophilic properties and reducing the thickness of the modified membrane. Also, it could improve permeability without sacrificing the selectivity of the membrane.image

Automated summary

In this study, semi-aromatic polyamide membranes were modified by adding two amino acids, glycine and l-lysine, which improved the hydrophilic surface and reduced the thickness of the modified membranes. The modified membranes exhibited higher permeation flux without sacrificing salt rejection at elevated temperatures. This work provides a cost-saving, facile, and eco-friendly preparation method for effectively improving the permeation flux while maintaining high rejection of salts.