Facile preparation of melamine foam with superhydrophobic performance and its system integration with prototype equipment for the clean-up of oil spills on water surface

Melamine Network as a Solution for Significant Enhancement of the Mechanical, Adsorptive, and Surface Properties in a Novel Carbon Nanomaterial-Silica Aerogel Composite

Silica aerogels exhibit exceptional characteristics such as mesoporosity, light weight, high surface area, and pore volume. Nevertheless, their utilization in industrial settings remains constrained due to their brittleness, moisture sensitivity, and costly synthesis procedure. Several studies have proved that adding nanofillers, such as carbon nanotubes (CNT) or graphene nanoplatelets (GNP), can improve the mechanical strength of the aerogels. The incorporation of nanofillers is often accompanied by agglomeration and pore blockage, which, in turn, deteriorates the surface area, pore volume, and low density. Including flexible melamine foam (MF) as a scaffold for the silica aerogel and nanofiller composite can prevent the restacking of the nanofillers through π-π interaction, hence maintaining the incredible properties of aerogels and improving their mechanical properties. CNT, GNP, and the polymeric silica precursor, polyvinyltrimethoxysilane (PVTMS), were added to a MF, at varying concentrations, to fabricate the MF-aerogel nanocomposites. Surfactant and sonication were utilized to ensure a homogeneous dispersion of the nanofillers in the system. The presence of MF prevented the agglomeration of nanofillers, resulting in lower density and relatively higher surface properties (SBET up to 929 m2·g-1 and pore volume up to 4.34 cc·g-1). Moreover, the MF-supported samples could endure 80% strain without breakage and showed an outstanding compressive strength of up to ∼20 MPa. These aerogel nanocomposites also demonstrated an excellent volatile organic compound (∼2680 mg·g-1) and cationic dye adsorption (∼10 mg·g-1).

Bio-Inspired Textiles for Self-Driven Oil-Water Separation-A Simulative Analysis of Fluid Transport

In addition to water repellency, superhydrophobic leaves of plants such as Salvinia molesta adsorb oil and separate it from water surfaces. This phenomenon has been the inspiration for a new method of oil-water separation, the bionic oil adsorber (BOA). In this paper, we show how the biological effect can be abstracted and transferred to technical textiles, in this case knitted spacer textiles hydrophobized with a layered silicate, oriented at the biology push approach. Subsequently, the transport of the oil within the bio-inspired textile is analyzed by a three-dimensional fluid simulation. This fluid simulation shows that the textile can be optimized by reducing the pile yarn length, increasing the pile yarn spacing, and increasing the pile yarn diameter. For the first time, it has been possible with this simulation to optimize the bio-inspired textile with regard to oil transport with little effort and thus enable the successful implementation of a self-driven and sustainable oil removal method.

A comprehensive review on anticorrosive/antifouling superhydrophobic coatings: Fabrication, assessment, applications, challenges and future perspectives

Superhydrophobicity (SHP) is an incredible phenomenon of extreme water repellency of surfaces ubiquitous in nature (E.g. lotus leaves, butterfly wings, taro leaves, mosquito eyes, water-strider legs, etc). Historically, surface exhibiting water contact angle (WCA) > 150° and contact angle hysteresis <10° is considered as SHP. The SHP surfaces garnered considerable attention in recent years due to their applications in anti-corrosion, anti-fouling, self-cleaning, oil-water separation, viscous drag reduction, anti-icing, etc. As corrosion and marine biofouling are global problems, there has been focused efforts in combating these issues using innovative environmentally friendly coatings designs taking cues from natural SHP surfaces. Over the last two decades, though significant progress has been made on the fabrication of various SHP surfaces, the practical adaptation of these surfaces for various applications is hampered, mainly because of the high cost, non-scalability, lack of simplicity, non-adaptability for a wide range of substrates, poor mechanical robustness and chemical inertness. Despite the extensive research, the exact mechanism of corrosion/anti-fouling of such coatings also remains elusive. The current focus of research in recent years has been on the development of facile, eco-friendly, cost-effective, mechanically robust chemically inert, and scalable methods to prepare durable SHP coating on a variety of surfaces. Although there are some general reviews on SHP surfaces, there is no comprehensive review focusing on SHP on metallic and alloy surfaces with corrosion-resistant and antifouling properties. This review is aimed at filling this gap. This review provides a pedagogical description with the necessary background, key concepts, genesis, classical models of superhydrophobicity, rational design of SHP, coatings characterization, testing approaches, mechanisms, and novel fabrication approaches currently being explored for anticorrosion and antifouling, both from a fundamental and practical perspective. The review also provides a summary of important experimental studies with key findings, and detailed descriptions of the evaluation of surface morphologies, chemical properties, mechanical, chemical, corrosion, and antifouling properties. The recent developments in the fabrication of SHP -Cr-Mo steel, Ti, and Al are presented, along with the latest understanding of the mechanism of anticorrosion and antifouling properties of the coating also discussed. In addition, different promising applications of SHP surfaces in diverse disciplines are discussed. The last part of the review highlights the challenges and future directions. The review is an ideal material for researchers practicing in the field of coatings and also serves as an excellent reference for freshers who intend to begin research on this topic.

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.

Oil adsorbing and transporting surfaces: a simulative determination of parameters for bionic functional textiles

Certain superhydrophobic plants, such asSalvinia molesta, are able to adsorb oil films from water surfaces and thus separate the oil from the water. There are first attempts to transfer this phenomenon to technical surfaces, but the functional principle and the influence of certain parameters are not yet fully understood. The aim of this work is to understand the interaction behavior between biological surfaces and oil, and to define design parameters for transferring the biological model to a technical textile. This will reduce the development time of a biologically inspired textile. For this purpose, the biological surface is transferred into a 2D model and the horizontal oil transport is simulated in Ansys Fluent. From these simulations, the influence of contact angle, oil viscosity and fiber spacing/diameter ratio was quantified. The simulation results were verified with transport tests on spacer fabrics and 3D prints. The values obtained serve as a starting point for the development of a bio-inspired textile for the removal of oil spills on water surfaces. Such a bio-inspired textile provides the basis for a novel method of oil-water separation that does not require the use of chemicals or energy. As a result, it offers great added value compared to existing methods.

Durable superhydrophobic/superoleophilic melamine foam based on biomass-derived porous carbon and multi-walled carbon nanotube for oil/water separation

In the present study, fabrications of two eco-friendly superhydrophobic/superoleophilic recyclable foamy-based adsorbents for oil/water mixture separation were developed. Hierarchically biomass (celery)-derived porous carbon (PC) and multi-walled carbon nanotube (MWCNT) were firstly synthesized and loaded on pristine melamine foam (MF) by the simple dip-coating approach by combining silicone adhesive to create superhydrophobic/superoleophilic, recyclable, and reusable three-dimensional porous structure. The prepared samples have a large specific surface area of 240 m²/g (MWCNT), 1126 m²/g (PC), and good micro-mesoporous frameworks. The water contact angle (WCA) values of the as-prepared foams, PC/MF and MWCNT/MF, not only were 159.34° ± 1.9° and 156.42° ± 1.6°, respectively but also had oil contact angle (OCA) of equal to 0° for a wide range of oils and organic solvents. Therefore, PC/MF and MWCNT/MF exhibited superhydrophobicity and superoleophilicity properties, which can be considered effective adsorbents in oil/water mixture separations. In this context, superhydrophobic/superoleophilic prepared foams for kind of different oils and organic solvents were shown to have superior separation performance ranges of 54-143 g/g and 46-137 g/g for PC/MF and MWCNT/MF, respectively, suggesting a new effective porous material for separating oil spills. Also, outstanding recyclability and reusability of these structures in the ten adsorption-squeezing cycles indicated that the WCA and sorption capacity has not appreciably changed after soaking into acidic (pH = 2) and alkaline (pH = 12) as well as saline (3.5% NaCl) solutions. More importantly, the reusability and chemical durability of the superhydrophobic samples made them good opportunities for use in different harsh conditions for oil-spill cleanup.

Fabrication of Superhydrophobic/Superoleophilic Bamboo Cellulose Foam for Oil/Water Separation

Water is an indispensable strategic resource for biological and social development. The problem of oily wastewater pollution originating from oil spillages, industrial discharge and domestic oil pollution has become an extremely serious international challenge. At present, numerous superwetting materials have been applied to effectively separate oil and water. However, most of these materials are difficult to scale and their large-scale application is limited by cost and environmental protection. Herein, a simple, environmentally friendly strategy including sol-gel, freeze-drying and surface hydrophobic modification is presented to fabricate a bamboo cellulose foam with special wetting characteristics. The bamboo cellulose foam is superhydrophobic, with a water contact angle of 160°, and it has the superoleophilic property of instantaneous oil absorption. Owing to the synergistic effect of the three-dimensional network structure of the superhydrophobic bamboo cellulose foam and its hydrophobic composition, it has an excellent oil-absorption performance of 11.5 g/g~37.5 g/g for various types of oil, as well as good recyclability, with an oil (1,2-dichloroethane) absorption capacity of up to 31.5 g/g after 10 cycles. In addition, the prepared cellulose-based foam exhibits an outstanding performance in terms of acid and alkali corrosion resistance. Importantly, owing to bamboo cellulose being a biodegradable, low-cost, natural polymer material that can be easily modified, superhydrophobic/superoleophilic bamboo cellulose foam has great application potential in the field of oily wastewater treatment.