According to Tsinghua University Material College Network August 18, 2016, in graphene oxide (GO) layered films, oxygen-containing functional groups support the SP2 nanocapillary network, this unique structure has ultra-fast water transport characteristics and excellent selectivity for different solutes in water, in the field of filtration and separation has potential applications. It has been widely accepted that GO thin films can be used to screen solute molecules and ions larger than the critical size of interlayer nanocapillaries for nanofiltration and ultrafiltration. However, the use of GO film to achieve water desalination is still challenging, and the results reported are highly controversial, hindering the further research and development of GO film in the field of practical desalination. The application of GO film in water desalination is a promising and challenging development direction. It is of great significance to solve the problem of shortage and pollution of clean fresh water resources in the world. And how to fully develop its potential.
Recently, Zhu Hongwei's team of the Institute of Materials has used isotope labeling to assist the simultaneous tracking of water and salt ion transmembrane diffusion, pressure-driven filtration and molecular dynamics simulation, revealing the reasons for the long-neglected controversy in the study of GO membrane water desalination. The results show that GO film can achieve excellent water/ion selectivity in concentration gradient-driven diffusion process, and has potential applications in water desalination. However, the desalination rate of GO film is very low in pressure-driven filtration process. Experimental and theoretical studies confirm that these contradictory results are due to the strong correlation between water/ion selectivity and external pressure and the length of GO interlayer nanochannels. External pressure weakens the water-ion interaction confined to the GO nanochannel, and thus reduces the water/ion selectivity. The length of the GO nanochannel regulates the relative selectivity between different salt ions and plays a leading role in the transport of water and ions. The above results lay a foundation for understanding the deep desalination mechanism of GO thin films. Considering the negative effect of external pressure on the intrinsic high water/ion selectivity of GO thin films and the unique transport mechanism of water molecules and salt ions in GO thin films, the application of thick GO thin films in the field of positive osmosis desalination will be a potential development direction in the future.
The results were published in the Journal of Chemical Science under the title of "Intrinsic high water/ion selectivity of graphene oxide lamellar membranes in concentration gradient-driven diffusion". The work was carried out by the School of Materials, Tsinghua University, the National Institute for Materials Science (NIMS) and Tsinghua University's Aeronautical Academy. Sun Pengzhan, a 2016 Ph.D. graduate from the School of Materials, was the first author, and Professor Zhu Hongwei, Japanese NIMS researcher Ma Renzhi, and Professor Xu Zhiping of the Aeronautical Academy were the correspondents. Author. School of materials, Tsinghua University is the first unit.