Heterogeneous Fenton catalysts: A review of recent advances.

Superhydrophilic/underwater superoleophobic membranes have aroused much research enthusiasm because of their good anti-fouling ability for the treatment of oil-contaminated water. However, such anti-fouling membranes inevitably suffer from fouling during long-term use. Thus, anti-fouling membranes with excellent self-cleaning performance, fast and superior flux recovery are still greatly required. Herein, the green tannic acid (TA)-Fe(III) complex is first assembled onto the polyvinylidene fluoride membrane (PVDF) surface and followed by the in situ mineralization of β-FeOOH to fabricate the PVDF/TA/β-FeOOH membrane for efficient oil/water emulsion separation. The resultant membrane exhibits superhydrophilicity and underwater superoleophobicity with underwater OCA of above 155° for various oils. Importantly, the as-prepared membrane shows fast (within 10 min) and excellent flux recovery (over 98%) attributed to the robust photo-Fenton catalytic activity of β-FeOOH. Moreover, the membrane also displays high separation efficiency (>99.1%) and high flux (1426.8–2106.2 L m−2 h−1 bar−1) for a series of oil/water emulsions. This study highlights a new direction in the development of photo-Fenton self-cleaning membranes with fast and robust flux recovery for efficient oil/water emulsion separation.

Photo-Fenton self-cleaning membranes with robust flux recovery for an efficient oil/water emulsion separation

Membrane filtration and absorption strategies based on superwetting surfaces for oil–water separation have regained tremendous attention due to their being low cost, highly efficient and environmentally friendly. Besides the usual superhydrophobic, superhydrophilic/underwater superoleophobic and dual superlyophobic surfaces, very novel and unprecedented surfaces with special extreme wetting behavior have been widely used in oil–water separation. In this review, novel surfaces with extreme wetting behavior for oil-water separation reported over the past three years including superhydrophilic–superoleophobic, superamphiphobic, superhydrophilic-underoil superhydrophilic, underoil superhydrophobic-underwater superoleophobic and liquid-infused surfaces, as well as oil–water separation mechanisms, separation approaches and design principles for obtaining novel superwetting membranes, are systematically summarized. The most common problems in the process of oil–water separation-membrane pollution and solutions are discussed. In addition, the selection of substrates, the swelling of hydrophilic membranes and the wettability conversion of intelligent response membranes are analyzed. The current trends, challenges and future research opportunities are also proposed, providing a road map for the future development of high-efficiency oil–water separation technology.

Designing novel superwetting surfaces for high-efficiency oil–water separation: design principles, opportunities, trends and challenges

Photo-Fenton self-cleaning PVDF/NH2-MIL-88B(Fe) membranes towards highly-efficient oil/water emulsion separation

Facile preparation of grass-like structured NiCo-LDH/PVDF composite membrane for efficient oil–water emulsion separation

Herein, a graphene oxide/MIL-88A(Fe) (GO/M88A) membrane was prepared for the first time by a facile vacuum filtration method. The intercalation of photo-Fenton catalytic M88A into GO nanosheets can not only regulate 2D nanochannels, but also endow the membrane with photo-Fenton catalytic activity. Accordingly, the GO/M88A membrane showed an enhanced separation efficiency and flux (more than 6 times that of GO membrane) based on synergistic separation/photo-Fenton processes. Importantly, the GO/M88A membrane maintained high separation efficiency (97.87 %) and almost constant flux even after 12 cycles of MB separation. The GO/M88A membrane can also be used to treat real textile wastewaters. Moreover, the membrane was directly used as catalyst for photo-Fenton catalytic degradation of contaminants with high degradation efficiency for MB (98.81 %) and BPA (97.27 %). Therefore, the results indicate that this novel GO/M88A membrane has excellent separation performance, stability and photo-Fenton activity and can be used as a potential membrane for water purification and environmental protection applications.

Graphene oxide/Fe(III)-based metal-organic framework membrane for enhanced water purification based on synergistic separation and photo-Fenton processes

With the rapid development of petrochemical industry, oily wastewater pose a serious threat to environment and human safety. Recently, superhydrophobic and superoleophilic materials have received considerable interest due to their high selective oil/water separation. Nevertheless, facile fabrication, stability, eco-friendly, sustainable and low cost materials are still a great challenge. Here, a sustainable superhydrophobic cellulose membrane (SOCM) is prepared via one-step facile sol-gel strategy for efficient oil/water separation. The superhydrophobicity is endowed with cellulose membrane (CM) by one-step micro/nano hierarchical structures construction and low-surface-energy chemical modification from tetraethyl orthosilicate (TEOS) and hexadecyltrimethoxysilane (HDTMS) hydrolysis and polycondensation. The SOCM shows high separation efficiencies (above 98%) for various oil/water mixtures. Importantly, the SOCM displays well environmental (acid, alkali and salt-resistance) and mechanical durability (tape peeling and scratch-resistance) and remarkable reusability (at least 10 times). The merits of facile fabrication, stability, eco-friendly, sustainable and low cost make SOCM a promising candidate material for large-scale application in oil/water separation.

Yangyang Chen

Papers

Photo-Fenton self-cleaning membranes with robust flux recovery for an efficient oil/water emulsion separation

Photo-Fenton self-cleaning PVDF/NH2-MIL-88B(Fe) membranes towards highly-efficient oil/water emulsion separation

Graphene oxide/Fe(III)-based metal-organic framework membrane for enhanced water purification based on synergistic separation and photo-Fenton processes

One-step facile fabrication of sustainable cellulose membrane with superhydrophobicity via a sol-gel strategy for efficient oil/water separation

Dual superlyophobic zeolitic imidazolate framework-8 modified membrane for controllable oil/water emulsion separation