Magnesium stearate-coated superhydrophobic sponge for oil/water separation: Synthesis, properties, application

A solar-driven nanocellulose Janus aerogel with excellent floating stability and dual functions of oil-water separation and photocatalytic degradation of organic pollutants

Effective and practical cleanup of viscous crude oil spills is extremely important in real harsh marine environments. Herein, we designed a solar-driven, nanocellulose-based Janus aerogel (Janus-A) with excellent floating stability and dual function of oil-water separation and degradation of aqueous organic pollutants. Janus-A, with its amphiprotic nature, was prepared through polypyrrole (PPy) deposition, freeze-drying, octyltrichlorosilane (OTS) impregnation, TiO2 spraying on the bottom surface, and UV irradiation treatment. The photothermal conversion effect of PPy coating raised the surface temperature of aerogel to 75.8 °C within 6 min under one simulated solar irradiation, which greatly reduced the viscosity of the crude oil and increased the absorption capacity of the aerogel to 36.7 g/g. Benefiting from the balance between the buoyancy generated by the hydrophobic part and water absorption of the hydrophilic part, Janus-A showed excellent floating stability under simulated winds and waves. In addition, Janus-A exhibited high degradation efficiency for organic pollutants in water owing to the synergistic photocatalytic properties of TiO2 and PPy. These excellent performances make Janus-A ideal for integrated water-oil separation and water remediation.

The Design of PAN-Based Janus Membrane with Adjustable Asymmetric Wettability in Wastewater Purification

In this paper, an environmentally friendly polyacrylonitrile-based (PAN-based) composite membrane with a Janus structure for wastewater treatment was successfully fabricated. To achieve the optimum adsorption of PAN-based Janus composite membrane, the asymmetric wettability was regulated through electrospinning, resulting in TiO2 modifying PAN as the hydrophilic substrate layer, and PCL gaining a different thickness as the hydrophobic layer. The prepared Janus composite membrane (PAN/TiO2-PCL20) showed excellent oil/water separation performance for diverse surfactant-stabilized oil-in-water emulsions. For n-hexane-in-water emulsion, the permeate flux and separation efficiency reached 1344 L m-2 h-1 and 99.52%, respectively. Even after 20 cycles of separation, it still had outstanding reusability and the separation efficiency remained above 99.15%. Meanwhile, the PAN/TiO2-PCL20 also exhibited an excellent photocatalytic activity, and the removal rate for RhB reached 93.2%. In addition, the research revealed that PAN/TiO2-PCL20 possessed good mechanical property and unidirectional water transfer capability. All results indicated that PAN/TiO2-PCL20 with photocatalysis and oil/water separation performance could be used for practical complex wastewater purification.

Study on the Mechanism of Rapid Oil-Water Separation by a Fe3 O4 @PMMA@PDMS Intelligent Superhydrophobic Micro/Nanorobot

We prepared an environmentally friendly intelligent Fe3 O4 @PMMA@PDMS superhydrophobic oil-absorbing material with simple process and excellent performance, and investigated the effects of different particle sizes of Fe3 O4 , different concentrations of PDMS, and different heating times on the superhydrophobicity of the coating. The best performance of the coating was achieved at a particle size combination of 20/500 nm for Fe3 O4 , a PDMS to Fe3 O4 @PMMA mass ratio of 6 : 1, and a heating time of 2 min at 400 °C. H2-SPSS coating not only has excellent superhydrophobicity, abrasion resistance, self-cleaning property, and chemical corrosion, but also has good flux and efficiency for separating oil-water mixture, with fluxes of 40,540, 32,432, and 37,027 Lm-2 h-1 for trichloromethane, dichloromethane and bromoethane, respectively, and separation efficiencies of 99.78 %, 99.74 % and 99.73 %, respectively. In addition, we also prepared a superhydrophobic magnetic polyurethane (SPPU) sponge using Fe3 O4 @PMMA@PDMS, which not only has a good oil absorption capacity of 18-44 g/g for different oil substances, it can also move directionally by magnet attraction and absorb oil along a fixed path. Under the control of the magnet, SPPU completes the whole oil absorption process in only 4 s, showing excellent oil absorption and intelligence.

Eco-Friendly Fluorine Functionalized Superhydrophobic/Superoleophilic Zeolitic Imidazolate Frameworks-Based Composite for Continuous Oil-Water Separation

Superhydrophobic metal-organic framework (MOF)-based sponges have received increasing attention in terms of treating oil-water mixtures. However, highly fluorinated substances, commonly used as modifiers to improve the hydrophobicity of MOFs, have aroused much environmental concern. Developing a green hydrophobic modification is crucial in order to prepare superhydrophobic MOF-sponge composites. Herein, we report the preparation of a porous composite sponge via a polydopamine (PDA)-assisted growth of zeolitic imidazolate frameworks (ZIF-90) and eco-friendly hydrophobic short-chain fluorinated substances (trifluoroethylamine) on a melamine formaldehyde (MF) sponge. The composite sponge (F-ZIF-90@PDA-MF) exhibited superhydrophobicity (water contact angle, 153°) and superoleophilicity (oil contact angle, 0°), which is likely due to the combination of the low surface energy brought on by the grafted CF₃ groups, as well as the rough surface structures that were derived from the in situ growth of ZIF-90 nanoparticles. F-ZIF-90@PDA-MF showed an excellent adsorption capacity of 39.4-130.4 g g^-1 for the different organic compounds. The adsorbed organic compounds were easily recovered by physical squeezing. Continuous and selective separation for the different oil-water mixtures was realized by employing the composite sponge as an absorbent or a filter. The separation efficiency and flux reached above 99.5% and went up to 7.1 ×10⁵ L m^-2 h^-1, respectively. The results illustrate that the superhydrophobic and superoleophilic F-ZIF-90@PDA-MF sponge has potential in the field of water-oil separation, especially for the purposes of large-scale oil recovery in a water environment.

Synthesis of Superhydrophobic/Superoleophilic stearic acid and Polymer-modified magnetic polyurethane for Oil-Water Separation: Effect of polymeric nature

The superhydrophobic/superoleophilic materials based on polyurethane foams have been layered with three different polymers and extensive modification with iron/magnetic nanocomposite. The general desires are to study the effect of the polymer layer and to eliminate the oil contaminant from the oil-water system which is crucial due to the development of environmental technologies. These materials were generated by facile dip-coating two-step method on the polyurethane foams (PUF) surface. PUF was directly layered with polydopamine/polypyrrole/polyaniline (PDA/PPy/PANI) and incorporated with Fe-SA (stearic acid) nanocomposites by ultrasonication and refluxing. In addition, characterization by FTIR, SEM/EDX, XRD, and TGA presented that the polymer layer and Fe-SA nanocomposites successfully covered the PUF surface caused by the chelating interaction between the carboxylates and active sites on iron particles due to intermolecular hydrogen bond interaction. Interestingly, the water contact angle (WCA) measurement of the nanocomposites displayed that the contact angle significantly improved up to 164°. After 20 cycles of oil absorption capacity, the WCA steadily remained up to 153° indicating powerful superhydrophobic properties of the materials. Furthermore, the oil absorption capacity of the materials was evaluated using typical oil-water separation methods such as reusability, separation efficiency, and oil permeate flux. The results exhibited that the modified PUFs have enhanced the absorption capacity up to 44 times the foam weight, 99 % separation efficiency, and about 8000 L.m-2.h-1 oil flux. For oil removal, the dyed oil phase was rapidly absorbed within 2 s confirming the highly used products for a wide area of oil-water separation. PDA-coated PUF nanocomposites obtained the most outstanding results due to their remarkable interfacial adhesion properties which provide larger active functional groups for hydrogen bonding interaction on PUF surface and Fe-SA nanocomposites.

Superhydrophobic magnetic sorbent via surface modification of banded iron formation for oily water treatment

In the current study, a simple dry coating method was utilized to fabricate a super-hydrophobic super-magnetic powder (ZS@BIF) for oily water purification using zinc stearate (ZS) and banded iron formation (BIF). The produced composite was fully characterized as a magnetic sorbent for oily water treatment. The results of X-ray diffraction diffractometer (XRD), Fourier transform infrared (FTIR), X-ray photoelectron spectroscopy (XPS), scanning electron microscope (SEM), energy-dispersive X-ray spectroscopy (EDS) and particle size analysis revealed the fabrication of homogenous hydrophobic-magnetic composite particles with core–shell structure. Contact angle and magnetic susceptibility results showed that 4 (BIF): 1 (Zs) was the ideal coverage ratio to render the core material superhydrophobic and preserve its ferromagnetic nature. The capability of the fabricated composite to sorb. n-butyl acetate, kerosene, and cyclohexane from oil–water system was evaluated. ZS@BIF composite showed a higher affinity to adsorb cyclohexane than n-butyl acetate and kerosene with a maximum adsorption capacity of about 22 g g⁻¹ and 99.9% removal efficiency. Moreover, about 95% of the adsorbed oils could be successfully recovered (desorbed) by rotary evaporator and the regenerated ZS@BIF composite showed high recyclability over ten repeated cycles.

Facile Preparation of Robust Superhydrophobic/Superoleophilic TiO2-Decorated Polyvinyl Alcohol Sponge for Efficient Oil/Water Separation

Oily wastewater and oil spills pose a threat to the environment and human health, and porous sponge materials are highly desired for oil/water separation. Herein, we design a new superhydrophobic/superoleophilic TiO₂-decorated polyvinyl alcohol (PVA) sponge material for efficient oil/water separation. The TiO₂-PVA sponge is obtained by firmly anchoring TiO₂ nanoparticles onto the skeleton surface of pristine PVA sponge via the cross-linking reactions between TiO₂ nanoparticles and H₃BO₃ and KH550, followed by the chemical modification of 1H,1H,2H,2H-perfluorodecyltrichlorosilane. The as-prepared TiO₂-PVA sponge shows a high water contact angle of 157° (a sliding angle of 5.5°) and an oil contact angle of ∼0°, showing excellent superhydrophobicity and superoleophilicity. The TiO₂-PVA sponge exhibits excellent chemical stability, thermal stability, and mechanical durability in terms of immersing it in the corrosive solutions and solvents, boiling it in water, and the sandpaper abrasion test. Moreover, the as-prepared TiO₂-PVA sponge possesses excellent absorption capacity of oils or organic solvents ranging from 4.3 to 13.6 times its own weight. More importantly, the as-prepared TiO₂-PVA sponge can separate carbon tetrachloride from the oil-water mixture with a separation efficiency of 97.8% with the aid of gravity and maintains a separation efficiency of 96.5% even after 15 cyclic oil/water separation processes. Therefore, the rationally designed superhydrophobic/superoleophilic TiO₂-PVA sponge shows great potential in practical applications of dealing with oily wastewater and oil spills.

In situ self-foaming preparation of hydrophobic polyurethane foams for oil/water separation

Polyurethane foams with excellent oil–water separation performance were prepared using hydrophobic raw materials with the assistance of a physical cooling agent.

Permeabilities and Mechanical Properties of Hardened Cement Pastes Modified with Sodium Laurate and Nano Silica

In this work, a method of imparting hydrophobicity and high strength to hardened cement paste (HCP) is proposed. Sodium laurate (SL) was used as a hydrophobic modifier and nano silica (NS) as a pozzolan. The HCP was modified by SL and NS simultaneously. HCP modified with different contents of SL and NS was prepared. Surface wettability, micro-structures, chemical composition, and organic structure were systematically studied using contact angle (CA) measurement, scanning electron microscope (SEM) observation, X-ray photoelectron spectroscopy (XPS), and attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR), respectively. The surface CA of the sample is 138.5° and has high hydrophobicity. Compared with the reference sample, the water absorption of the modified sample reduced by 96.55%, while the compressive strength only reduced by 6.91%. Therefore, using hydrophobic modifier and reinforcing agent as cement admixture is an effective method to endow concrete with hydrophobicity and high strength at the same time.

Preparation and modification of cellulose sponge and application of oil/water separation

This work presents a facile preparation and modification of cellulose sponge with hydrophobic/oleophilic surface wetting properties.