Improved desalination by polyamide membranes containing hydrophilic glutamine and glycine

Abstract

Water desalination and recycling of wastewater is a key challenge to meet water shortage issues. Thin film composite polyamide membranes are widely used for desalination; however, their low permeability due to a poor hydrophilicity is a major drawback. Here, we designed novel thin film composite membranes having good hydrophilicity, permeability, and stability without compromising solute rejection. We improved the membrane hydrophilicity by incorporation of hydrophilic additives, such as glycine and l-glutamine, into the polyamide layer. Hence polyamide-based flat sheet membranes were fabricated via interfacial polymerization of m-phenylenediamine and trimesoyl chloride and then were coated over a polysulfone/sulfonated polyphenylsulfone (85:15) support. Polyamide membranes were then characterized and tested for desalination. Results show that the ridge and valley structure observed by scanning electron microscopy confirms the formation of the polyamide layer on membrane surface. The performance reached the highest pure water flux of 36.23 Lm−2 h−1 and flux recovery ratio of 89.18% for membranes with 2 wt% of l-glutamine. Incorporation of 2 wt% l-glutamine induced a high permeate flux and a maximum rejection of 87.87% for MgSO4, 83.50% for Na2SO4 and 60.77% for NaCl solutions. Overall, the polyamide nanofiltration membrane with hydrophilic groups displayed superior antifouling property and can be used as a potential candidate for desalination.