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Water Desalination through a Zeolitic Imidazolate Framework Membrane by Electro‐ and Thermo‐Osmosis: Which Could Be More Efficient?
Author(s) -
Gupta Krishna M.,
Jiang Jianwen
Publication year - 2017
Publication title -
chemistryselect
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.437
H-Index - 34
ISSN - 2365-6549
DOI - 10.1002/slct.201700386
Subject(s) - desalination , forward osmosis , reverse osmosis , pressure retarded osmosis , osmotic power , membrane , osmosis , chemical engineering , seawater , chemistry , flux (metallurgy) , zeolitic imidazolate framework , environmental engineering , materials science , environmental science , engineering , organic chemistry , biochemistry , oceanography , adsorption , geology , metal organic framework
Pressure‐driven reverse osmosis (RO) is commonly used for water desalination. Due to high pressure gradient (Δ P ) involved in RO, however, there is continuous quest for other alternative techniques. In this study, electro‐ and thermo‐osmosis are examined by atomistic simulations for water desalination through a zeolitic imidazolate framework (ZIF) membrane. Under an electric field of 1.5 V/nm, water flux is predicted to be 2.8 × 10 4 kg/(m 2 ⋅h), corresponding to a flux at Δ P =40 bar in RO; but salt rejection is rather poor (50 %). With a temperature difference of 20 K between pure water and seawater, water flux of 5.7 × 10 4 kg/(m 2 ⋅h) is achieved in thermo‐osmosis, which is equivalent to a flux at Δ P =80 bar in RO; and salt rejection is up to 98 %. From the analysis of potential of mean force, it is revealed that the free energy barrier for water flow in thermo‐osmosis is low (2.8 kcal/mol), thus leading to a high water flux. The number of hydrogen bonds for water in the membrane is estimated to be 2.5 and the lifetime is about 0.9 ps. This study suggests that thermo‐osmosis might be superior to electro‐osmosis, and it could be a promising alternative technique to RO for water desalination.