Zeolitic imidazolate framework-8 as a reverse osmosis membrane for water desalination: Insight from molecular simulation
The Journal Of Chemical Physics, 134, 2011, 134705
Zhongqiao Hu1, Yifei Chen1, and Jianwen Jiang1
1Department of Chemical and Biomolecular Engineering, National University of Singapore, 117576, Singapore
In this paper, molecular dynamics (MD) simulations study on water desalination using zeolitic imidazolate framework-8 (ZIF-8) membrane was conducted. ZIF is a class of metal-organic frameworks structurally similar to the porous zeolites. MD simulations show that under external pressure, water desalination can be facilitated as Na+ and Cl- ions cannot pass through the apertures of ZIF-8.
Two sections were prepared for reverse osmosis; the left chamber contained a 0.5 M NaCl solution consisting of 9864 H2O molecules, 90 Na+ and 90 Cl- ions. The right chamber consisted of 3741 H2O molecules. These two sections were separated by a ZIF-8 membrane 29.43 ? thick. LJ parameters were used, applying the universal force field (UFF) for the membrane. The water model used was TIP3P whose rigid structure was maintained by the SETTLE algorithm, while the ions were considered as charged LJ particles with parameters from the AMBER force field. Energy minimization was done using the steepest descent method. At varied pressures there was an observed linear increase in flux as pressure was increased. The observed water flux compared to carbon nanotube (CNT) and boron nitride nanotube (BNNT) membranes is relatively lower but the ZIF-8 membrane was able to deliver a salt rejection rate of 95% which is acceptable for human consumption.
Here, a porous metal-organic complex framework was investigated and significant insight with regards to its desalination potential was drawn from MD simulation. This is a significant step towards the branching out of membrane technology in desalination as the performance of a relatively new material (in the said application) is assessed.
John Matthew V. Cajudo