Desalination and Nanofiltration through Functionalized Laminar MoS₂ Membranes

Abstract

Laminar membranes of two-dimensional materials are excellent candidates for applications in water filtration due to the formation of nanocapillaries between individual crystals that can exhibit a molecular and ionic sieving effect, while allowing high water flux. This approach has been exemplified previously with graphene oxide, however these membranes suffer from swelling when exposed to liquid water, leading to low salt rejection and reducing their applicability for desalination applications. Here, we demonstrate that by producing thin (∼5 μm) laminar membranes of exfoliated molybdenum disulfide (MoS) in a straightforward and scalable process, followed by a simple chemical functionalization step, we can efficiently reject ∼99% of the ions commonly found in seawater, while maintaining water fluxes significantly higher (∼5 times) than those reported for graphene oxide membranes. These functionalized MoS membranes exhibit excellent long-term stability with no swelling and consequent decrease in ion rejection, when immersed in water for periods exceeding 6 months. Similar stability is observed when exposed to organic solvents, indicating that they are ideal for a variety of technologically important filtration applications.

Potential dependent ionic sieving through functionalized laminar MoS2 membranes

“…Then, the prepared Ag/AgCl electrodes were cleaned by rinsing with deionized water to remove any residue. 1 Finally, the stability of the as-prepared Ag/AgCl reference electrodes were tested as working and reference electrodes in 0.1 M KCl solution by applying current of 0 A for 1 hour. The stable Ag/AgCl reference electrodes showed a potential difference around −0.8 mV (ideally should be less than ±1.0 mV).…”

Highly Stable and Antibacterial Two‐Dimensional Tungsten Disulfide Lamellar Membrane for Water Filtration

“…[29,30] Additionally,t he layered MoS 2 membranes were also utilized to separate organic vapors [25] and ions. [26] Above all, the reported layer-stacked TMD membranes showedp rominent stability in water,a cid, and alkaline environments, as well as excellent separation properties.N evertheless, few reports were focusedo nt he long-term stability of the TMD laminar membranes during water filtration,a nd the separation performance of the TMD laminarm embranes werem ainly investigated in ad ead-endf iltrations etup rather than ac ross-flow system.Across-flow system with ac ontinuous or semi-continuous feed can alleviate intense concentration polarization andm embrane fouling to somee xtent.T he antifouling and antibacterial properties of TMD laminar membranes have been rarely investigated, even thought he membranes would inevitably make contact with organics, bacteria, and colloidsi np ractical applications, leading to severe membrane fouling. Therefore, the antifouling and antibacterial properties of the TMD laminarm embranes are two important aspects for the application in water filtration.…”

“…The water permeances were 3–7 times higher than that of pristine GO membranes . Additionally, the layered MoS 2 membranes were also utilized to separate organic vapors and ions . Above all, the reported layer‐stacked TMD membranes showed prominent stability in water, acid, and alkaline environments, as well as excellent separation properties.…”

“…Recent reports have demonstrated that transition metal dichalcogenide (TMD) nanosheets could also assemble into thin laminar membranes with remarkable water filtration performance, which can possibly evade the above concerns about the GO membranes . Unlike the GO nanosheets, the TMD nanosheets retained their structural integrity without any chemical modification during exfoliation.…”

“…[24] Recent reports have demonstrated that transition metal dichalcogenide (TMD) nanosheets could also assemble into thin laminar membranes with remarkable water filtration performance, whichc an possibly evade the above concerns about the GO membranes. [25,26] Unlike the GO nanosheets, the TMD nanosheets retained their structural integrity without any chemicalm odification during exfoliation. All sulfur atoms were Two-dimensional (2D) lamellar membranes consistingo fr estacked WS 2 nanosheets have shown excellent separation properties for water filtration.…”