Environmentally friendly kaolin-coated meshes with superhydrophilicity and underwater superoleophobicity for oil/water separation

Exploration of the performance of iron-based superhydrophilic meshes for oil-water separation

This study investigates the oil-water separation capability of iron-based superhydrophilic meshes. It also intends to provide an optimistic view of their potential for industrial application. Oil-water separation performance of the 150 mesh, 300 mesh, and 400 mesh is primarily examined by analyzing the efficiency and speediness of separation as well as the limit of oil intrusion using petroleum based oils. The superhydrophilic meshes are further applied for oil-water separation of locomotive wash effluent. The superhydrophilic meshes showed good oil-water separation behavior. The 300 mesh is observed to have superior separation performance. It is also tested to have good reusability and resistance in harsh conditions. The separation effectiveness of 94.7%, reduced turbidity of 21.8 NTU, and chemical oxygen demand of around 70 ppm, along with reasonable flux and intrusion pressure values of 73.28 Lm-2min-1 and 0.848 kPa, respectively, are noticed for the separation study conducted for locomotive wash effluent using the designated superhydrophilic mesh. This study hence as well demonstrates a prospective future of superhydrophilic mesh for practical utility.

Robust Superamphiphobic Coating Applied to Grease-Proof Mining Transformer Components

The iron core and heat sink in a mining transformer are susceptible to damage from oil spills or the harsh mine environment; the deterioration of oil products in the underground environment and transformers produce massive amounts of harmful liquid substances, which may lead to unnecessary economic losses in drilling engineering. To overcome this issue, a convenient and economical way to protect transformer components was developed. Herein, we proposed an air spray technology at room temperature for the preparation of antigreasy superamphiphobic coatings, which are suitable for bulk metallic glass transformer cores and ST13 heat sinks. The addition of polypyrrole powder effectively improves the thermal conductivity and specific heat of the coating in the range of 50-70 °C. More importantly, the fabricated coating has excellent repellency to liquids, such as water, ethylene glycerol, hexadecane, and rapeseed oil. Meanwhile, the coating has excellent physical and chemical resistance and outstanding antifouling features, which provide a feasible solution for combating grease pollution and corrosion in the mine environment. Taking multifaceted stability into consideration, this work contributes to enhancing the application of superamphiphobic coatings in the fields of protecting transformer components in the harsh environment or during transformer operation faults.

A biomimetic structured bio-based flame retardant coating on flexible polyurethane foam with low smoke release and antibacterial ability

Flexible polyurethane foam (FPUF) is widely used in our life, but it is inherent flammable. The demand for environmental-friendly multi-functional FPUF has been increasing rapidly in the last decade. In this work, a novel bio-based flame retardant coating was constructed by chemically reacting sodium alginate (OSA) and polydopamine (PDA) on the FPUF, followed by depositing nanorod-like β-FeOOH molecules through complexation reaction to form a biomimetic structure. The limiting oxygen index of the coated FPUF samples reached 25.5%. The peak heat release rate was reduced by 45.0%, and the smoke density of the coated sample was decreased by 69.1% compared to that of the control FPUF sample. It was proposed that the OSA-PDA-β-FeOOH decomposed during combustion to promote the formation of compact crosslinked char and released inert gases to dilute the combustible gases, and the β-FeOOH transferred to Fe₂O₃ to settled the smoke particles reducing the smoke release. Furthermore, the coating with shark skin like structure endowed FPUF antibacterial ability because of its good superoleophobicity underwater. This work provided a novel strategy to construct a biomimetic multifunctional coating on the FPUF.

Synthesis of Si-Based High-Efficiency and High-Durability Superhydrophilic-Underwater Superoleophobic Membrane of Oil-Water Separation

Oil pollution is caused by the frequent discharge of contaminated industrial wastewater and accidental oil spills and is a severe environmental and health concern. Therefore, efficient materials and processes for effective oil–water separation are being developed. Herein, SiO₂-Na₂SiO₃-coated stainless steel fibers (SSF) with underwater superoleophobic and low-adhesion properties were successfully prepared via a one-step hydrothermal process. The modified surfaces were characterized with scanning electron microscopy (SEM), and contact angle measurements to observe the surface morphology, confirm the successful incorporation of SiO₂, and evaluate the wettability, as well as with X-ray diffraction (XRD). The results revealed that SiO₂ nanoparticles were successfully grown on the stainless-steel fiber surface through the facile hydrothermal synthesis, and the formation of sodium silicate was detected with XRD. The SiO₂-Na₂SiO₃-coated SSF surface exhibited superior underwater superoleophobic properties (153–162°), super-hydrophilicity and high separation efficiency for dichloromethane–water, n-hexane–water, tetrachloromethane–water, paroline–water, and hexadecane–water mixtures. In addition, the as-prepared SiO₂-Na₂SiO₃-coated SSF demonstrated superior wear resistance, long-term stability, and re-usability. We suggest that the improved durability may be due to the presence of sodium silicate that enhanced the membrane strength. The SiO₂-Na₂SiO₃-coated SSF also exhibited desirable corrosion resistance in salty and acidic environments; however, further optimization is needed for their use in basic media. The current study presents a novel approach to fabricate high-performance oil–water separation membranes.

Highly-efficient, Rapid and continuous separation of surfactant-stabilized Oil/Water emulsions by selective under-liquid adhering emulsified droplets

Anti-adhesion is considered to be the basis for oil/water separation. However, this principle may not the superior choice for surfactant-stabilized oil/water emulsions owing to the inevitable adhesion of surfactant on the membrane, resulting in further adhesion of emulsified droplets and therefore attenuation in separation performance. Herein, we demonstrated a novel separation strategy for surfactant-stabilized oil/water emulsions by exploiting rather than preventing adhesion. A modified filter paper (mFP) with strong under-liquid adhesion to emulsified droplets was prepared, endowing it excellent separation performance for both surfactant-stabilized and surfactant free emulsions with very high separation efficiency (up to 99.9 %). Furthermore, the Random layer stacked scraps of mFP (RLS-mFP) were used to construct the separation device, which provided a labyrinthine but unobstructed flow path for emulsion because of the randomly stacked form and relatively large interspace among mFP scraps. The RLS-mFP has excellent separation performance with the separation flux for surfactant-stabilized oil-in-water and water-in-oil emulsions achieving 1035 and 3570 L m^-2 h^-1 respectively only under gravity. After 1-hour continuous separation, both flux and separation efficiency of RLS-mFP showed almost no decline comparing to initial flux for surfactant-stabilized emulsions. Meanwhile, the mFP could be easily recycled by rinsing and reused at least 50 times without sacrificing separation performance.