Newly Emerging Metal–Organic Frameworks (MOF), MXenes and Zeolite …
235
displayed similar structures as that of GO. Ti 3 C 2 T x MXene membranes with interlayer spacing of ~0.6 nm demonstrated ultrafast water flux of 37.4 L/(m
2 ·h·bar)),
which was attributed to the hydrophilic nature and the presence of H2O between the
layers. Ti 3 C 2 T x showed high selectivity toward single-, double-, and triple-charged
metal cations and dye cations of different sizes. For cationic dyes (MB) with large
size, the rejection was 100%. For double-charged Mg
2+ , interlayer space shrank and
the permeation was lowered. Inversely, single charged Na
+ expanded the interlayer
spacing and enhance the permeation. Such character enables Ti 3 C 2 T x to be effectively
used in separating higher charged cations.
Ag nanoparticles were used to modify MXene (Ti 3 C 2 Tx) to enhance the permeations and improve the antifouling capability (Fig. 7a–c) [134]. Ag@MXene with
variable Ag nanoparticles loadings were fabricated by in-situ production of Ag via
the self-reduction of Ag(NO 3 ) 2 on MXene surface. The intriguing thing was that
MXene acted as both the membrane and reducing agent. The optimized Ag loading
of 21% enhanced the water flux of MXene significantly from 118 to 420 LMH under
the same experiment conditions while the organic molecules rejections were well
maintained (Fig. 7d and e). In addition, Ag@MXene displayed better water flux
recovery than pristine MXene (Fig. 7f). Moreover, Ag@MXenen exhibited prominently increased antifouling ability toward Escherichia coli with more than 99% of
inhibition, while the MXene manifested only 60% of bacterial growth inhibition and
hydrophilic PVDF as a reference sample exhibited no bacterial inhibition. This kind
of membrane can be a good candidate for NF applications (Fig. 7g).
Recently, MXene was intercalated into GO to synthesize MXene/GO lamellar
membranes to be used in molecular separations (Fig. 8) [135]. Because GO lamellar
membranes are not permeable for organic solvents, MXene nanosheets were intercalated into the interlayers of GO membranes to reduce the spacing distance via
vacuum filtration method. The composite membranes showed excellent water and
organic solvent permeations. The flux of pure solvents of water, acetone, methanol,
ethanol, and IPA was 21.02, 48.32, 25.03, 10.76, and 6.18 L·m
−2 ·h
−1 (LMH), respectively, and the rejections for all the dyes were over 990% in aqueous and organic
solvents.
MXene-based 2D nanosheets have also shown usage in heavy metal ions removal
[136]. Considering that Ti 3 C 2 Tx MXene might be oxidized in aqueous media,
magnetic Fe 2 O 3 nanoparticles were deposited onto the surface of MXene (MGMX)
by solvothermal method using Fe(CH 3 COO) 2 as a precursor to enhance their stability
(Fig. 9) [137]. MGMX could adsorb 99.9% OF Hg
2+ with capacity of 1128.41 mg/g
even in the existence of background metal ions. The high adsorption was attributed to
the presence of large amount of O- and OH- groups together with negatively charged
surfaces. Magnetic properties of MGMX made them easily separated from aqueous
solutions after the adsorption.
And recently, a kind of Ti 3 C 2 T x MXene-based core–shell spheres (MX-SA)
containing MXene core and alginate (SA) shell were fabricated and used as adsorbents for Hg
2+ (Fig. 10) [138]. The spheres were fabricated using varied concentrations of Ti 3 C 2 T x MXene and SA via CaCl 2 as the crosslinking agent. The optimized
MX/SA ratio was 4:20. Under this condition, the spheres exhibited the inner core
235
displayed similar structures as that of GO. Ti 3 C 2 T x MXene membranes with interlayer spacing of ~0.6 nm demonstrated ultrafast water flux of 37.4 L/(m
2 ·h·bar)),
which was attributed to the hydrophilic nature and the presence of H2O between the
layers. Ti 3 C 2 T x showed high selectivity toward single-, double-, and triple-charged
metal cations and dye cations of different sizes. For cationic dyes (MB) with large
size, the rejection was 100%. For double-charged Mg
2+ , interlayer space shrank and
the permeation was lowered. Inversely, single charged Na
+ expanded the interlayer
spacing and enhance the permeation. Such character enables Ti 3 C 2 T x to be effectively
used in separating higher charged cations.
Ag nanoparticles were used to modify MXene (Ti 3 C 2 Tx) to enhance the permeations and improve the antifouling capability (Fig. 7a–c) [134]. Ag@MXene with
variable Ag nanoparticles loadings were fabricated by in-situ production of Ag via
the self-reduction of Ag(NO 3 ) 2 on MXene surface. The intriguing thing was that
MXene acted as both the membrane and reducing agent. The optimized Ag loading
of 21% enhanced the water flux of MXene significantly from 118 to 420 LMH under
the same experiment conditions while the organic molecules rejections were well
maintained (Fig. 7d and e). In addition, Ag@MXene displayed better water flux
recovery than pristine MXene (Fig. 7f). Moreover, Ag@MXenen exhibited prominently increased antifouling ability toward Escherichia coli with more than 99% of
inhibition, while the MXene manifested only 60% of bacterial growth inhibition and
hydrophilic PVDF as a reference sample exhibited no bacterial inhibition. This kind
of membrane can be a good candidate for NF applications (Fig. 7g).
Recently, MXene was intercalated into GO to synthesize MXene/GO lamellar
membranes to be used in molecular separations (Fig. 8) [135]. Because GO lamellar
membranes are not permeable for organic solvents, MXene nanosheets were intercalated into the interlayers of GO membranes to reduce the spacing distance via
vacuum filtration method. The composite membranes showed excellent water and
organic solvent permeations. The flux of pure solvents of water, acetone, methanol,
ethanol, and IPA was 21.02, 48.32, 25.03, 10.76, and 6.18 L·m
−2 ·h
−1 (LMH), respectively, and the rejections for all the dyes were over 990% in aqueous and organic
solvents.
MXene-based 2D nanosheets have also shown usage in heavy metal ions removal
[136]. Considering that Ti 3 C 2 Tx MXene might be oxidized in aqueous media,
magnetic Fe 2 O 3 nanoparticles were deposited onto the surface of MXene (MGMX)
by solvothermal method using Fe(CH 3 COO) 2 as a precursor to enhance their stability
(Fig. 9) [137]. MGMX could adsorb 99.9% OF Hg
2+ with capacity of 1128.41 mg/g
even in the existence of background metal ions. The high adsorption was attributed to
the presence of large amount of O- and OH- groups together with negatively charged
surfaces. Magnetic properties of MGMX made them easily separated from aqueous
solutions after the adsorption.
And recently, a kind of Ti 3 C 2 T x MXene-based core–shell spheres (MX-SA)
containing MXene core and alginate (SA) shell were fabricated and used as adsorbents for Hg
2+ (Fig. 10) [138]. The spheres were fabricated using varied concentrations of Ti 3 C 2 T x MXene and SA via CaCl 2 as the crosslinking agent. The optimized
MX/SA ratio was 4:20. Under this condition, the spheres exhibited the inner core