Highly stable graphene oxide/nylon membrane for molecular separation

Haftu Gebrekiros Alemayehu; Rshan Beyene Hailu; Paulos Taddesse

doi:10.1088/1361-6528/acd060

Highly stable graphene oxide/nylon membrane for molecular separation

Nanotechnology. 2023 May 15;34(30). doi: 10.1088/1361-6528/acd060.

Authors

Haftu Gebrekiros Alemayehu^{1

2

3}, Rshan Beyene Hailu⁴, Paulos Taddesse⁵

Affiliations

¹ CAS Key Laboratory of Nanosystem and Hierarchical Fabrication, CAS Center for Excellence in Nanoscience, National Centre for Nanoscience and Technology, Beijing, People's Republic of China.
² University of Chinese Academy of Sciences, 19 A Yuquan Rd, Shijingshan District, Beijing 100049, People's Republic of China.
³ Department of Chemistry, College of Natural Sciences, Arba Minch University, PO Box-21, Ethiopia.
⁴ Department of Hydraulics and Water Resource Engineering, Water Technology Institute, Arba Minch University, PO Box-21, Ethiopia.
⁵ Department of Physics, College of Natural Sciences, Arba Minch University, PO Box-21, Ethiopia.

PMID: 37100047
DOI: 10.1088/1361-6528/acd060

Abstract

Graphene oxide (GO), due to its one-atom-thick structure and enriched oxygenated functionalities, is a promising candidate material to develop nanofiltration membranes to tackle the current worldwide water shortage. However, the stability of the GO membrane in an aqueous environment and its long-term operation remains unresolved. These issues greatly affect the mass transfer in the GO membrane. Here, we fabricate an ultrathin GO membrane on a nylon substrate within 5 min with the help of vacuum filtration for molecular separation. Thus, GO/nylon membranes dried in an oven at temperatures of 70 °C show greater aqueous solution stability than those dried at room temperature. To validate the stability, both GO membranes were immersed in DI water for 20 d. As a result, the GO/nylon membrane dried at room temperature was completely detached from the substrate within 12 h, whereas the GO/nylon membrane that dried at 70 °C remained stable for more than 20 d without any physical damage. We suppose the enhanced stability is due to the thermally induced balance in electrostatic repulsion resulting in stabilizing of the GO membrane. This method improves the GO membrane's operating time, selectivity, and permeability. Therefore, the optimized GO/nylon membrane shows higher rejection of organic dyes (∼100%) and good selectivity for sulfate salts such as Na₂SO₄and MgSO₄(>80%). The membrane continuously operates for more than 60 h with only a 30% water permeability decline and 100% rejection of dyes. We believe that the drying of GO/nylon membranes at a moderate temperature is important for enhanced separation performance and stability. This drying technique can be applied to other applications.

Keywords: graphene oxide; membrane separation; nanofiltration desalination; nylon membrane.