The effect of an electric field on ion separation and water desalination using molecular dynamics simulations

We study the same system in zero fields

Samaneh Rikhtehgaran

2021

Scholarcy highlights

  • The availability of drinking water, which is one of the most basic requirements for human life, has been threatened by the world’s fast population growth, global warming, contamination, and other factors
  • There was no preference between positive and negative ions in zero fields, and there was no preferred direction to their movements; no ion separation could occur in this case
  • When the external electric field was applied in one direction, positive and negative ions moved in opposite directions, and Na+ ions remained in the first box while Cl− ions preferentially entered the second box and subsequently entered the third box
  • The results show that by increasing the magnitude of the electric field, the ion separation was improved considerably: more Cl− ions passed through the CNT and entered the second box and subsequently the third box while more Na+ ions remained in the first box
  • We perform molecular dynamics simulations to investigate the performance of a graphene-CNT membrane in ion rejection and water purification of a NaCl solution using the application of the electric field
  • We calculated the ion rejection R = \( \frac{N_i-{N}_p}{N_i} \), where Np is the number of ions in the second box and Ni is the initial number of ions. According to this figure, by increasing the magnitude of the electric field, the ion rejection values improved and for E = 10 mV/Å, the percentage of ion rejection increased significantly and it reached 95% which represents the capability of this nanofilter for ion removal
  • The major advantage of our proposed nanofilter is that while ions and water molecules can pass through a large entrance of CNT which is a crucial factor for achieving high water flux, we can successfully separate ions to obtain fresh water
  • Our MD results may offer helpful guidelines to design an energy-efficient desalination membrane

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