Biomimetic fabrication of superhydrophobic loofah sponge: robust for highly efficient oil-water separation in harsh environments

Sustainable approach to oil recovery from oil spills through superhydrophobic jute fabric

Ecosystems suffer from increased oil exploitation and frequent oil spills, which calls for effective, environment-friendly, and economically viable solutions. To address this, abandoned gunny sacks as the concerned jute fabric were superhydrophobically (water contact angle ∼159°) modified, incorporating titanium dioxide (TiO2) nanoparticles and hexadecyltrimethoxysilane (HDTMS), rendering a facile drop casting procedure. The modified superhydrophobic-superoleophilic jute fabric has been identified as a high-performance filter with superior reusability that can separate oil-water mixtures in challenging environmental conditions (including potent acidic, alkaline, highly saline, aqueous, frigid, and blistering water environments) while maintaining high separation efficiency. In continuation, static conditions indulging a batch and continuous oil separation performance and dynamic conditions stimulating turbulence in the oil-water mixture were proficiently carried out, mimicking real-world circumstances. As a result, the modified jute fabric has the advantages of high separation efficiency, stable recyclable properties, and outstanding durability, highlighting its enormous potential for use in practical applications.

Marine oil spill remediation by Candelilla wax modified coal fly ash cenospheres

Biodegradable candelilla wax (CW) was creatively used for hydrophobic modification of coal fly ash cenospheres (FACs), a waste product from thermal power plants, and a new spherical hollow particulate adsorbent with fast oil adsorption rate and easy agglomeration was prepared. CW was confirmed to physically coat FACs and the optimum mass of wax added to 3 g of FACs was 0.05 g. From a series of batch scale experiments, CW-FACs were found to adsorb oil, reaching adsorption efficiency of 80.6% within 10 s, and aggregate into floating clumps which were easily removed from the water's surface. The oil adsorption efficiency was highly dependent on hydrophobicity of the used adsorbent, the adsorption of Venezuela oil onto CW-FACs was found to be a homogenous monolayer, and the capacity and intensity of the adsorption decreased as temperature increased from 10 to 40 °C. The Langmuir isotherm model was the best fit, with the maximum adsorption capacity achieved at 649.38 mg/g. CW-FACs were also found to be highly stable in concentrated acid, alkaline and salt solutions, as well as for spills of different oil products. Furthermore, the retention rate of the oil adsorption capacity of the CW-FACs after 6 cycles of adsorption-extraction was as high as 93.2%. Therefore, CW-FACs can be widely used, easily recycled, and reused for marine oil spill remediation, which is also a good alternative disposal solution for FACs.

Assessment of various forms of cellulose-based Luffa cylindrica (mat, flakes and powder) reinforced polydimethylsiloxane composites for oil sorption and organic solvents absorption

Oil spillage has damaged public health noticeably and contributed to significant environmental deterioration. As a result, a significant amount of effort has been spent on investigating and developing the sorbent materials capable of separating oil from water. Thus, the sorbent materials that could be effective particularly in oil spill disposal and resolve such environmental issue remain to be explored. We have proposed luffa cylindrica (LC)-polydimethylsiloxane (PDMS) composite forms to remove the oil and organic components that might be hazardous to aquatic organisms. The scaffolds were fabricated using hand lay-up method with various forms of luffa cylindrica i.e., LC mat, flakes and powder. Various characterizations such as scanning electron microscopy (SEM), atomic force microscopy (AFM), thermogravimetric analysis (TGA), effective porosity, surface wettability, mechanical stability, cytotoxicity and sorption behavior with respect to oil, phosphate buffer saline (PBS) and few organic solvents were performed. The results showed that the scaffold in combination with P-L flakes was highly effective in eradicating oil spills and removing harmful components of crude oil. Scaffolds composed of P-L mat, P-L flakes, P-L powder, and PDMS (P) exhibited oil absorption efficacy around 16.09 ± 4.62 %, 24.49 ± 3.55 %, 15.52 ± 2.67 % and 5.52 ± 1.44 %, respectively. We anticipate that the proposed scaffolds have the tremendous potential to provide a solution to this significant environmental remediation issue and to serve as a cost-effective method for removing oil spills and hazardous crude oil components.

Superhydrophobic MS@CuO@SA sponge for oil/water separation with excellent durability and reusability

We present a superhydrophobic material based on commercially melamine sponge (MS) with great durability, recyclability, and excellent sorption performance. The fabrication process of this sponge is facile without using toxic reagents or sophisticated equipment and therefore it is simple to scale up. The CuO layer utilized to give a rough surface of the substrate (MS) was successfully prepared in a commercial microwave to seed copper nucleuses in an alkaline medium. Stearic acid (SA) plays a role as the self-assembled monolayer on the surface of the sponge skeletons. Throughout this study, the properties of the modified sponge were fully characterized, and the changes in wettability were carefully examined. Water contact angle (WCA) measurements revealed the excellent superhydrophobicity of the material with high static WCA of 165.1° and low dynamic WCA of 8°. Furthermore, the as-prepared sponge demonstrated high efficiency in separation (over 99.0%) of different oils from water. Notably, several unique properties of as-modified material were found, consisting of ultrafast sorption capacities of up to 32-52 times of its own weight by using 80 mL of each oil, outstanding reusability with good sorption capacity even after 40 cycles. Even under various harsh environments, the novel materials proved its outstanding durability and ultrafast sorption capacity of oils. The durability, recyclability, and superhydrophobic properties of the novel superhydrophobic sponge provide it a solid basis for oil-water separation applications through an ultrafast sorption capacity of oils as well as quick recovery of the oil by easy squeezing process.

Fabrication of three bio-adsorbents from different parts of rape straw

Three kinds of bio-adsorbents are fabricated from the different parts of rape straw, which are adsorbent core, adsorbent hull, and adsorbent stalk, respectively. As the adsorbates, kerosene, paraffin, rapeseed oil, and dibutyl phthalate are employed to evaluate the adsorption performance of the three kinds of bio-adsorbents. The results suggest that adsorbent core has much higher adsorption quantity to all the four adsorbates (27.37, 32.23, 33.37, and 39.28 g/g, respectively) than adsorbent hull (7.39, 8.37, 8.85, and 10.30 g/g) and adsorbent stalk (6.75, 7.25, 7.92, and 9.32 g/g). The adsorption mechanism of the three bio-adsorbents is investigated. The results illustrate that different bio-adsorbents own different micromorphologies. The special microchamber structure is found in the bio-adsorbent of the adsorbent core, which is seen as the main reason for its excellent adsorption performance. The adsorption volume of unit mass (Va) was proposed to evaluate the intrinsic adsorption properties of the bio-adsorbents. The recovery performance of the bio-adsorbents is investigated by using of two different treatment methods. The effect of treatment on recovery rate is discussed.

Construction of Natural Loofah/Poly(vinylidene fluoride) Core-Shell Electrospun Nanofibers via a Controllable Janus Nozzle for Switchable Oil-Water Separation

Developing microstructure and multifunctional membranes toward switchable oil-water separation has been highly desired in oily wastewater treatment. Herein, a controllable Janus nozzle was employed to innovatively electrospin natural loofah/poly(vinylidene fluoride) (PVDF) nanofibers with a core-shell structure for gravity-driven water purification. By adjusting flow rates of the PVDF component, a core-shell structure of the composite fibers was obtained caused by the lower viscosity and surface tension of PVDF. In addition, a steady laminar motion of fluids was constructed based on the Reynolds number of flow fields being less than 2300. In order to investigate the formation mechanism of the microstructure, a series of Janus nozzles with different lengths were controlled to study the blending of the two immiscible components. The gravity difference between the two components might cause disturbance of the jet motion, and the PVDF component unidirectionally encapsulated the loofah to form the shell layer. Most importantly, the dry loofah/PVDF membranes could separate oil from an oil-water mixture, while the water-wetted membrane exhibited switchable separation that could separate water from the mixtures because of the hydroxyl groups of the hydrophilic loofah hydrogen-bonding with water molecules and forming a hydration layer. The composite fibers can be applied in water remediation in practice, and the method to produce core-shell structures seems attractive for technological applications involving macroscopic core-shell nano- or microfibers.

Robust superhydrophobic polyurea@cellulose nanocrystal coating

A multifunctional superhydrophobic PU@CNC composite coating with self-cleaning properties and mechanical durability was fabricated using a facile spraying method.

Facile Fabrication of Magnetic, Durable and Superhydrophobic Cotton for Efficient Oil/Water Separation

In this paper, we present a facile and efficient strategy for the fabrication of magnetic, durable, and superhydrophobic cotton for oil/water separation. The superhydrophobic cotton functionalized with Fe₃O₄ magnetic nanoparticles was prepared via the in situ coprecipitation of Fe2+/Fe3+ ions under ammonia solution on cotton fabrics using polyvinylpyrrolidone (PVP) as a coupling agent and hydrophobic treatment with tridecafluorooctyl triethoxysilane (FAS) in sequence. The as-prepared cotton demonstrated excellent superhydrophobicity with a water contact angle of 155.6° ± 1.2° and good magnetic responsiveness. Under the control of the external magnetic field, the cotton fabrics could be easily controlled to absorb the oil from water as oil absorbents, showing high oil/water separation efficiency, even in hot water. Moreover, the cotton demonstrated remarkable mechanical durable properties, being strongly friction-resistant against sandpaper and finger wipe, while maintaining its water repellency. This study developed a novel and efficient strategy for the construction of magnetic, durable, and superhydrophobic biomass-based adsorbent for oil/water separation, which can be easily scaled up for practical oil absorption.

3D Arrays of Super-Hydrophobic Microtubes from Polypore Mushrooms as Naturally-Derived Systems for Oil Absorption

Porous materials derived from natural resources, such as Luffa sponges, pomelo peel and jute fibres, have recently emerged as oil adsorbents for water purification, due to their suitability, low environmental impact, biodegradability and low cost. Here we show, for the first time, that the porosity of the fruiting body of polypore mushrooms can be used to absorb oils and organic solvents while repelling water. We engineered the surface properties of Ganoderma applanatum fungi, of which the fruiting body consists of a regular array of long capillaries embedded in a fibrous matrix, with paraffin wax, octadecyltrichlorosilane (OTS) and trichloro(1H,1H,2H,2H-perfluorooctyl)silane. Morphological and wettability analyses of the modified fungus revealed that the OTS treatment was effective in preserving the 3D porosity of the natural material, inducing super-hydrophobicity (water contact angle higher than 150°) and improving oil sorption capacity (1.8⁻3.1 g/g). The treated fungus was also inserted into fluidic networks as a filtration element, and its ability to separate water from chloroform was demonstrated.