Professor In S. Kim and Professor Myung-Han Yoon have developed an ultra-high permeability water treatment membrane by using graphene nanofiber

□ GIST (President Seung Hyeon Moon): Professor In S. Kim of the School of Earth Sciences and Environmental Engineering and Professor Myung-Han Yoon of the School of Material Science and Engineering have developed an ultra-high permeability water treatment membrane by producing graphene * in the form of nanofibers to ensure physical strength without support layer **. 

* A high-strength material that is physically and chemically stable that is composed only of carbon

** A membrane made of a porous material to support the physical strength of the membrane

□ Forward osmosis * has been actively studied for a long time, and the support layer of the water treatment membrane used in the forward osmosis process is the main cause of deteriorating water treatment efficiency due to the concentration polarization ** phenomenon.

∘ This phenomenon is caused by the physical resistance of the support layer, which reduces the osmotic difference between the two solutions that cause the movement of the water, thus obstructing the movement of water. Concentration polarization, which occurs in the porous support layer, is a major cause of decreased water permeability.

* A process of filtering water by osmotic pressure difference by arranging a membrane between two solutions having different concentrations

** The physical resistance of the support layer reduces the osmotic pressure differential and reduces water movement

□ The research team removed the support layer from the existing water-treatment process and secured the physical strength by applying non-woven nanofibers and drastically reduced the concentration polarization phenomenon, thereby greatly improving water treatment efficiency. In addition, the water permeability of the water treatment membrane fabricated in this study is 54.6 LMH ***, which is 1.8 times better than the currently commercialized water treatment membrane (average 30 LMH).

*** Unit (L / m2 / h) indicating the permeation amount per unit area of the membrane per unit time

∘ The concentration polarization is determined by porosity *, tortuosity, * and thickness of the support layer. By removing the support layer, the team completely removed the physical factors and filled the gap between the graphene nanofibers with PVDF (polyvinylidene fluoride), which enabled it to function as a water treatment membrane.

* The ratio of the empty space to the total volume of the supporting layer

** The ratio of the distance that the actual water travels relative to the thickness of the support layer due to the curved structure inside the support layer

□ Professor In S. Kim said, "This study is a breakthrough in water treatment membrane fabrication by improving the water treatment efficiency by securing the physical strength by using graphene and nanofiber without a supporting layer, and this is expected to be widely applied in the water treatment market in the future."

□ This research was carried out with support from the Ministry of Land, Transport and Maritime Affairs (Seawater Desalination). The results of the research were published online in the Journal of Materials Chemistry A (JMCA) on April 4, 2018, and was selected as a frontispiece.