Three-Dimensional Superhydrophobic Hollow Hemispherical MXene for Efficient Water-in-Oil Emulsions Separation

Abstract

A superhydrophobic macroporous material composed of hollow hemispherical MXene (HSMX) was synthesized by the thermal annealing of MXene-wrapped cationic polystyrene spheres (CPS@MXene). Notably, the spherical MXene shells exhibited highly efficient catalysis of the carbonization of CPS into carbon nanoparticles. Their insertion into the interlayer of MXene increased the d-spacing and created hollow hemispheres. The as-prepared HSMX with nanoscale walls had a lower packing density than MXene, but higher porosity, total pore volume, and total pore area. Moreover, the stacking of hollow hemispheres promoted the formation of a highly undulating macroporous surface and significantly improved the surface roughness of the HSMX-based 3D membrane, resulting in superhydrophobicity with a water contact angle of 156.4° and a rolling angle of 6°. As a result, the membrane exhibited good separation efficiency and Flux for emulsifier-stabilized water-in-paraffin liquid emulsions, which was dependent on its superhydrophobic performance and strong demulsification ability derived from the razor effect originating from the ultrathin walls of HSMX. This work provides a facile approach for the transformation of highly hydrophilic 2D MXene into superhydrophobic 3D HSMX, and opens a new pathway for the development of advanced MXene-based materials for environmental remediation applications.

Current Understanding of the Wettability of MXenes

“…On the contrary, the hydrophobic film (e.g., based on the deposition of the hollow hemispherical Ti 3 C 2 T x /carbon NPs on a commercial PVDF film) tends to boost the capture/separation of oil phase through the film due to the enhanced (suppressed) interaction between the oil (water) and the surface, as shown in Figure a. [ 46 ]…”

“…a) The plot of WCA against the average surface roughness for Ti 3 C 2 T x films (based on the data presented in Table S1, Supporting Information). [ 17,43n,45,46 ] b) AFM images of Ti 3 C 2 T x films (deposited on the glass slides) with different roughness prepared by varying the number of dipping cycles in the MXene dispersion. c) WCA versus surface roughness for thin films formed by the same dispersion in one particular study.…”

“…Facilitating the access of electrolyte to the active sites Electrochemical degradation Ti 3 C 2 T x quantum dots [137] -Facilitating the charge transport; Improving the kinetics of the electrode/electrolyte interfacial reactions -Facilitating the accessibility of water molecules and K + ions into the narrow interlayer spacings due to a low energy barrier interaction between the oil (water) and the surface, as shown in Figure 13a. [46] Though the continuous development of superhydrophobic and superhydrophilic materials based on MXenes has provided potential solutions to many practical challenges, the exploration of responsive materials with the reversible wetting properties under certain type of external stimuli has received considerable attention. Recently, it has been reported that the wettability of MXene-based materials, such as the hybrid formed by Ti 3 C 2 T x and coumarin, can be reversibly modulated by UV irradiation (365 and 254 nm).…”

Facile Fabrication of Highly Hydrophobic Onion-like Candle Soot-Coated Mesh for Durable Oil/Water Separation

“…Inspired by lotus leaves with excellent water-repellent and self-cleaning properties, the biomimicry of superhydrophobic surfaces has drawn much attention in academic and industrial fields for applications in self-cleaning [ 12 , 13 ], oil/water separation [ 14 , 15 ], directional water transport [ 16 ], anti-icing [ 17 ], anticorrosion [ 18 ], and drag reduction [ 19 , 20 ]. Principally, hierarchical micro/nanostructures and inherently low surface energy chemicals are the two characteristics needed to construct superhydrophobic surfaces [ 21 , 22 ].…”

Wettability Improvement in Oil–Water Separation by Nano-Pillar ZnO Texturing

“…During the last decades, there has been increasing interest in the materials with unique functions due to their promising application in various fields such as self-cleaning, antimicrobial, anti-icing, biocompatible materials, or oil transportation [ 4 , 5 , 6 , 7 , 8 , 9 ]. Particularly, depending on the different interfacial energy between organic compounds and water in immiscible oil–water mixtures, the materials with special wettability have gained widespread attention in oil–water separation [ 10 , 11 ]. As a simple preparation method, the meshed membrane owned many advantages, such as high permeability of pore space, good oil–water separation efficacy, and promising corrosion resistance [ 12 , 13 ].…”