Highly Permeable Sulfonated Polydopamine Integrated MXene Membranes for Efficient Surfactant-Stabilized Oil-in-Water Separation

Abstract

MXene is an incredibly promising two-dimensional material with immense potential to serve as a high-performing separating or barrier layer to develop advanced membranes. Despite the significant progress made in MXene membranes, two major challenges still exist: (i) effectively stacking MXene nanosheets into defect-free membranes and (ii) the high fouling tendency of MXene-based membranes. To address these issues, we employed sulfonated polydopamine (SPD), which simultaneously serves as a binding agent to promote the compact assembling of Ti3C2T x MXenes (MX) nanosheets and improves the antifouling properties of the resulting sulfonated polydopamine-functionalized MX (SPDMX) membranes. The SPDMX membrane was tested for challenging surfactant-stabilized oil-in-water separation with an impressive efficiency of 98%. Moreover, an ultrahigh permeability of 1620 LMH/bar was also achieved. The sulfonation of PD helps in improving the antifouling characteristics of SPDMX by developing a strong hydration layer and enhancing the oleophobicity of the membrane. The underwater SPDMX membrane appeared superoleophobic with an oil contact angle of 153°, whereas the ceramic membrane exhibited an oil contact angle of 137°. The SPDMX membranes showed an improved flux recovery (31%) compared to the nonsulfonated counterpart. This work highlights the appropriate functionalization of MXene as a promising approach to developing MXene membranes with high permeation flux and better antifouling characteristics for oily wastewater treatment.

Superhydrophilic Photothermal-Responsive CuO@MXene Nanofibrous Membrane with Inherent Biofouling Resistance for Treating Complex Oily Wastewater

“…Another advantageous aspect includes the numerous interlayer channels that facilitate swift water transport, making them ideal for separating oily wastewater. 19,22,23 Besides its photocatalysis and oil/water separation performance, recent studies have highlighted its appealing photothermal conversion property, commonly referred to as light-to-heat conversion. 24 This photothermal conversion mechanism is attributed to its localized surface plasma resonance (LSPR) effect, similar to the metallic material.…”

“…The hydrophilic surface termination groups and numerous interlayer channels of MXene stand out as key strengths, rendering its anti-oil-fouling abilities. Another advantageous aspect includes the numerous interlayer channels that facilitate swift water transport, making them ideal for separating oily wastewater. ,, …”

Sulfonic Functionalized Polydopamine Coatings with pH-Independent Surface Charge for Optimizing Capillary Electrophoretic Separations

“…Moreover, the extensive potential of the developed SPD@capillary in practical applications was further demonstrated through the efficient separation of aromatic acids and nucleosides and rapid CD-based chiral analysis of racemic drugs. Recently, new strategies involved in the fabrication of sulfonated PDA (SPD) coatings and periodate-induced rapid deposition of PDA coatings were proposed, which possess abundant surface grafted sulfonate groups and good surface masking effect on various substrates [35][36][37]. Herein, to reveal the potential use of SPD-based materials and periodate-induced PDA coating strategy to achieve highly pH-independent and stable cathodic EOF in CE, we reported a facile approach to modify rapidly SPD coatings inside a capillary with high surface coverage and uniformity via post-sulfonation of periodate-triggered PDA coating (Figure 1).…”

Under-Oil Superhydrophilic/Superhydrophobic Janus Nanofibrous Membrane for Highly Efficient Separation of Surfactant-Stabilized Water-in-Oil Emulsions

“…For oil–water separation, under-oil superhydrophilicity can be an alternative to the hydrophilic–oleophobic property, because it also enables the antioil-fouling function by making water to replace oils that were attached on the membrane surface, and it also is able to promote the demulsification of water-in-oil emulsions, because of its stronger affinity to water than that to oils. − Compared to the hydrophilic–oleophobic property, under-oil superhydrophilicity has an obvious advantage of eliminating the use of a fluorinated moiety. So far, although there appear to be several under-oil superhydrophilic materials, including cellulose-based porous materials, , desert sand, fumed silica-coated metal felt, metal organic frame (MOF)-coated stainless-steel mesh, poly­(2-(dimethylamino)­ethyl methacrylate)-coated fabric, and electrospun membrane of deacetylated cellulose acetate, it is still challenging to achieve the under-oil superhydrophilicity, because the replacement of the solid–oil interface (lower interfacial tension) by a solid–water interface (higher interfacial tension) is thermodynamically unfavorable.…”