Abstract
Graphene oxide (GO) and its composite membranes have exhibited great potential for application in water purification and desalination. This article reports that a novel graphene oxide membrane (GOM) of ~5 µm thickness was fabricated onto a nylon membrane by vacuum filtration and cross-linked by amino acids (L-alanine, L-phenylalanine, and serine). The GOM cross-linked by amino acids (GOM-A) exhibits excellent stability, high water flux, and high rejection to metal ions. The rejection coefficients to alkali and alkaline earth metal ions through GOM-A were over 94% and 96%, respectively. The rejection coefficients decreased with an increasing H+ concentration. Metal ions (K+, Ca2+, and Fe3+) can be inserted into GOM-A layers, which enlarges the interlayer spacing of GOM-A and neutralizes the electronegativity of the membrane, resulting in the decease in the rejection coefficients to metal ions. Meanwhile, GOM-A showed quite high antibacterial efficiency against E. coli. With the excellent performance as described above, GOM-A could be used to purify and desalt water.
Highlights
Nowadays, all living things on the earth are being threatened greatly by the shortage and pollution of water because of the fast population growth and environmental pollution caused by industry development [1,2], so water treatment and purification are of great significance to the development of society and economy
Characterization of Graphene oxide (GO)-Ala, GO-PHE, graphene oxide membrane cross-linked by L-alanine (GO-Ser). It can be observed from SEM images (Figure 1a,b) that the surface of graphene oxide membrane (GOM) are smooth with typical wrinkle morphologies and lamellar structures, which is consistent with GOMs in the literature reported [20,24]
We explored the hydrophilicity of GO, GO-Ala, GO-PHE, GO-Ser by measuring contact angles
Summary
All living things on the earth are being threatened greatly by the shortage and pollution of water because of the fast population growth and environmental pollution caused by industry development [1,2], so water treatment and purification are of great significance to the development of society and economy. Graphene oxide (GO) sheets and form 2–3 layers of water molecule intercalation when permeating through the GO layer This will cause membrane swelling and an interlayer spacing enlargement of GOM, leading to a decrease in the stability of GOM. The stability of the GOM in the solution could be enhanced after cross-linking, which enables the wide application of enhanced membranes in the researches of metal ions and organic matter permeation. L-alanine, L-phenylalanine, and serine were selected to modify GOMs (named GO-Ala, GO-PHE, and GO-Ser, respectively) in this study to explore the influence on the properties of membranes. Their stability, water flux, and rejection coefficients to alkali metal and alkaline earth metal ions were evaluated. The antibacterial activity of the GOM cross-linked by amino acids was investigated
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