Elsevier

Desalination

Volume 504, 15 May 2021, 114975
Desalination

Molecular dynamics simulation of carbon peapod-like nanomaterials in desalination process

https://doi.org/10.1016/j.desal.2021.114975Get rights and content

Highlights

  • Carbon peapods have been investigated in desalination process using MD simulations.

  • Charge effects on fullerene, nanotube, and graphene surfaces were also examined.

  • Presence of fullerene into nanotube increases salt rejection (about 5 times).

  • N-doped fullerenes also increases the salt rejection more than the pure fullerenes.

  • Charged plates, CNTs, and peapods leads to complete salt rejection.

  • Presence of fullerenes into CNT changes the orientations of the confined water molecules.

Abstract

In this research, the performance of carbon peapod-like nanomaterials consisting 1 and 3 fullerenes into (13,13) armchair carbon nanotube (CNT) has been investigated in desalination process using molecular dynamics (MD) simulations with the applied pressure of 350 MPa. We have also examined different charge effects on the fullerene, nanotube, and graphene surfaces in this work. We have calculated different properties including water and ion flux, self-diffusion coefficient, radial distribution function (RDF), hydrogen bonding (HB) analysis, potential of mean force (PMF), and barrier energy of penetration. Our results showed that the highest and lowest water fluxes are for the pure CNT (2565 ns−1) and reverse charged fullerene peapod (270 ns−1) systems, respectively. The pure CNT also showed the highest ion flux (26 ns−1) than the other systems. Presence of fullerene into nanotube decreased the ion flux (6.5 ns−1) which represents acceptable performance of the peapods in salt rejection during desalination process. Using of N-doped fullerenes has small effect and increased the ion rejection more than the pure fullerenes. Our results also indicated that using of charged plates, CNTs, and peapods leads to complete salt rejection (zero ion flux). The pure CNT has the smallest barrier energy whereas the reverse charged CNT and the reverse charged plates have the biggest barrier energy required to water molecules to penetrate into the nanotube. Presence of fullerenes into the CNT also changes the orientations of the confined water molecules.

Graphical abstract

The presence of fullerene into nanotube increases salt rejection. N-doped fullerenes also increases the salt rejection more than the pure fullerenes.

Unlabelled Image
  1. Download : Download high-res image (304KB)
  2. Download : Download full-size image

Introduction

Recent studies explored and developed nano-scale structures for purification and desalination processes of water and wastewater [[1], [2], [3], [4]]. These nanostructures represented very good ion selectivity and salt rejection. Moreover, these nanomaterials exhibited excellent water permeability at the nano-dimensions [[5], [6], [7]]. Recently, many nanomaterials have been studied as effective membranes for water desalination including graphene and carbon nanotubes (CNTs) [[8], [9], [10], [11], [12]]. However, using each of these nanomaterials has certain challenges. For instance, CNTs with their nano-scale structures are very good candidates for the desalination process [1,13]. The CNTs are also very good materials for ion selection processes [[14], [15], [16], [17], [18]]. These nanostructures also enable us to understand the transport process of water molecules at the nano-scale dimensions which is important to find the biological functions of cells [19,20]. However, preparation of highly dense, long, and perfectly aligned CNTs is difficult at the industrial scale [21,22]. Graphene is also one of the significant candidates for the desalination membranes which its properties can be improved by changing the size of the nanopores, or by addition of functional groups on the pore's edges [23,24]. Previous simulations also indicated that single-layer nanoporous graphene (NPG) membranes can effectively separate NaCl from water [2]. It is also found that the water permeability of the NPG membranes is about five times more than the other membranes [25,26]. However, it is difficult to fabricate NPG membranes in large scale values [27]. Layered grapheme oxide (GO) membranes are another significant membranes used in the desalination process which can be prepared by relatively simple techniques [[28], [29], [30]]. Recently, the lamellar GO membranes exhibited very good ions rejection by tuning the distance between the GO layers [8,31,32] which was about 4 to10 times more than the other nano-membranes. Previous investigations showed that the epoxy and hydroxyl groups prefer to aggregate on graphene surfaces [33] and therefore, it is experimentally difficult to prepare the GO surfaces with only one kind of oxide group.

Here, we want to use new nano-materials based on CNTs in the desalination process. In the recent years, many scientists investigated desalination process using CNTs by molecular dynamics (MD) simulations and tried to examine different factors which were significant on the process. For example, Corry [17] reported that the size and uniformity of nanotubes is significant to reach a favorite salt rejection. In another search, Corry [34] showed that the use of electric charges at the initial position of a nanotube hinders the entrance of ions. Corry also indicated that the CNT functionalization decreases the water flow into the nanotube pore. Chan et al. [35] showed that using of zwitterion group at the CNT ends results in rapid water flow and also ion rejection. Goldsmith and Martens [36] examined size and structure dependent salt rejection using armchair CNTs and declared some evidence of rectification of ions for the asymmetric charge distributions in the (12,12) system. Nasrabadi and Foroutan [37] indicated that the ions separation is dependent on the amount of applied electric charge. Khataee et al. [38] reported that the (7, 7) and (8,8) SiC tubes selectively separated Na+ and Clions, respectively. Azamat et al. [39] reported much ion rejection by (5,5) BN tube. Razmkhah et al. [40] showed that strong electric and magnetic field increases and decreases water flow rate through CNT, respectively.

One of the efficient method to increase the salt rejection rate in the CNTs is to reduce the inside accessible volume [41]. In order to do this, fullerene (C60) molecules can be located into the CNTs without changing the homogeneity of chemical interior. The Carbon peapods are synthesized during the CNT preparation by pulsed laser vaporization [42]. The fullerene (C60) can also enter the CNT through defects or vapor-phase diffusion [43]. These new nanostructures, which are called peapods, have completely different thermal and electrical properties than the normal CNTs [[44], [45], [46]] and have attracted much interests and applications in the several investigations in the recent years [[47], [48], [49]].

In this research, we want to examine performance of the carbon peapods consisting one and three fullerene molecules into armchair nanotubes in desalination process using MD simulations. We have also examined different charge effects on the fullerene, nanotube, and graphene surfaces in this work. Previous studies showed that the N-doping of carbon nanostructures is an important method to improve their properties [[50], [51], [52]]. Therefore, we want to investigate using of N-doped fullerene into the CNTs to examine its effects on the desalination process.

Section snippets

Simulation details

Our model has been built from two graphene plates with the size of 44.5 Å × 50.5 Å comprising a membrane spanned by a (13,13) CNT with the length of 36 Å (almost similar to the MD simulation of Goldsmith and Martens [36]). One and three C60 fullerene have been also located into the CNT in different simulations. We have also located ±0.1C electric charge on different materials (such as fullerene, nanotube, or graphene surfaces) in the different simulations. We do not intend to investigate the

Water flux

The water flux (the number of water molecules transmitted from nanotube per nanosecond) has been represented for the different simulated systems in Fig. 1.

The water flux trend is as follows: Pure CNT>1 fullerene peapod > Reverse charged plates > Charged plates > Charged CNT> 3 fullerenes peapod ≈ 3N-doped fullerenes peapod > Reverse charged CNT>1 fullerene charged >1 fullerene reverse charged. The snapshot of the three N-doped fullerenes system has been presented after 2 ns of simulation time

Concluding remarks

The new nanostructures, which are called peapods, have completely different thermal and electrical properties than the normal CNTs and have attracted much interests and applications in the several investigations in the recent years. In this research, we have examined the performance of peapods consisting 1 and 3 fullerene molecules into armchair nanotubes in desalination process using MD simulations. Our results represents the acceptable performance of the peapod-like nanomaterials in the

Authorship statement

All persons who meet authorship criteria are listed as authors, and all authors certify that they have participated sufficiently in the work to take public responsibility for the content, including participation in the concept, design, analysis, writing, or revision of the manuscript. Furthermore, each author certifies that this material or similar material has not been and will not be submitted to or published in any other publication before its appearance in the Desalination.

Authorship contributions

Category 1

Conception and design of study: M. Abbaspour.

Acquisition of data: M. Abbaspour, N. Ahmadi.

Analysis and/or interpretation of data: M. Abbaspour, N. Ahmadi.

Category 2

Drafting the manuscript: M. Abbaspour.

Revising the manuscript critically for important intellectual content: M. Abbaspour, M. Namayandeh Jorabchi, H. Akbarzadeh, and N. Ahmadi.

Category 3

Approval of the version of the manuscript to be published (the names of all authors must be listed):

M. Abbaspour, M. Namayandeh Jorabchi,

Declaration of competing interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Acknowledgments

The authors would like to express their sincere thanks to Prof. Jafar Azamat for helpful guidance for the simulation of desalination process.

References (72)

  • B.W. Smith et al.

    Formation mechanism of fullerene peapods and coaxial tubes: a path to large scale synthesis

    Chem. Phys. Lett.

    (2000)
  • B.W. Smith et al.

    Carbon nanotube encapsulated fullerenes: a unique class of hybrid materials

    Chem. Phys. Lett.

    (1999)
  • M. Hosseini et al.

    Water desalination through fluorine-functionalized nanoporous graphene oxide membranes

    Mat. Chem. Phys.

    (2019)
  • F. Zhu et al.

    Pressure-induced water transport in membrane channels studied by molecular dynamics

    Biophys. J.

    (2002)
  • F. Zhu et al.

    Theory and simulation of water permeation in aquaporin-1

    Biophys. J.

    (2004)
  • J. Azamat et al.

    Molecular dynamics simulation of trihalomethanes separation from water by functionalized nanoporous graphene under induced pressure

    Chem. Eng. Sci.

    (2015)
  • J. Azamat et al.

    Molecular dynamics simulation of transport of water/DMSO and water/acetone mixtures through boron nitride nanotube

    Fluid Phase Equilib.

    (2016)
  • J. Azamat et al.

    Computational study on the efficiency of MoS2 membrane for removing arsenic from contaminated water

    J. Mol. Liq.

    (2018)
  • M. Hosseini et al.

    Improving the performance of water desalination through ultra-permeable functionalized nanoporous graphene oxide membrane

    Appl. Surf. Sci.

    (2018)
  • A.K. Giri et al.

    Structure and kinetics of water in highly confined conditions: a molecular dynamics simulation study

    J. Mol. Liq.

    (2018)
  • A.V. Raghunathan et al.

    Molecular understanding of osmosis in semipermeable membranes

    Phys. Rev. Lett.

    (2006)
  • D. Cohen-Tanugi et al.

    Water desalination across nanoporous graphene

    Nano Lett.

    (2012)
  • L. Ruiz et al.

    Tailoring the water structure and transport in nanotubes with tunable interiors

    Nanoscale

    (2015)
  • J.G. Gai et al.

    An ultrafast water transport forward osmosis membrane: porous graphene

    J. Mat. Chem. A

    (2014)
  • S. Joseph et al.

    Why are carbon nanotubes fast transporters of water?

    Nano Lett.

    (2008)
  • J.A. Thomas et al.

    Reassessing fast water transport through carbon nanotubes

    Nano Lett.

    (2008)
  • K. Falk et al.

    Molecular origin of fast water transport in carbon nanotube membranes: superlubricity versus curvature dependent friction

    Nano Lett.

    (2010)
  • J. Farahbaksh et al.

    Investigation of raw and oxidized multiwalled carbon nanotubes in fabrication of reverse osmosis polyamide membranes for improvement in desalination and antifouling properties

    Desalination

    (2017)
  • H.D. Lee et al.

    Experimental evidence of rapid water transport through carbon nanotubes embedded in polymeric desalination membranes

    Small

    (2014)
  • J. Cannon et al.

    Influence of ion size and charge on osmosis

    J. Phys. Chem. B

    (2012)
  • G. Hummer et al.

    Water conduction through the hydrophobic channel of a carbon nanotube

    Nature

    (2001)
  • J. Azamat et al.

    Water desalination through armchair carbon nanotubes: a molecular dynamics study

    RSC Adv.

    (2014)
  • M. Majumder et al.

    Erratum: Nanoscale hydrodynamics: enhanced flow in carbon nanotubes

    Nature

    (2005)
  • B. Corry

    Designing carbon nanotube membranes for efficient water desalination

    J. Phys. Chem. B

    (2008)
  • C.Y. Lee et al.

    Coherence resonance in a single-walled carbon nanotube ion channel

    Science

    (2010)
  • B. Alberts et al.

    Molecular Biology of the Cell

    (2002)
  • Cited by (21)

    View all citing articles on Scopus
    View full text