Multifunctional hollow superhydrophobic SiO2 microspheres with robust and self-cleaning and separation of oil/water emulsions properties

ZnO nanoparticles coated and stearic acid modified superhydrophobic chitosan film for self-cleaning and oil-water separation

The aim of this study was to prepare superhydrophobic chitosan films using a ZnO nanoparticle coating and stearic acid hydrophobic modification. A 1 % concentration of ZnO nanoparticles and a 1 % concentration of stearic acid generated a superhydrophobic film with the largest contact angle (WCA) of 156°, which was attributed to the synergy of micro/nano-level hierarchical structure and low surface energy modification. The superhydrophobic film showed better stability to acid, alkali, heat, and UV irradiation than a neat chitosan film and a reduction in light transmittance of 14.4 % at 354 nm. The superhydrophobic chitosan film also showed excellent self-cleaning and oil-water separation performance. Our findings will expand the application of chitosan films in food packaging, outdoor self-cleaning materials and oil-water separations.

Study on the Influence of Polymer/Particle Properties on the Resilience of Superhydrophobic Coatings

Enhancement in the resilience of superhydrophobic coatings is crucial for their future applicability. However, the progress in this aspect is currently limited due to the lack of a consistent resilience analysis methodology/protocol as well as the limited understanding of the influence of the materials components on the resultant coating performance. This study applies a quantitative analysis methodology involving image analysis and mass tracking and utilizes it to investigate how the properties of coating components can influence coating resilience. The factors examined were changing the molecular weight/tensile strength of poly(vinylchloride)/poly(dimethylsiloxane) (PVC/PDMS) polymers and changing the size of the roughening particles. In addition to the examination of resilience data to evaluate degradation patterns, three-dimensional (3D) mapping of the scratches was performed to obtain an insight into how material removal occurs during abrasion. The results can indicate preferential polymer selection (using higher-molecular-weight polymers for PVC) and optimal particle sizes (smaller particles) for maximizing coating resilience. The study, although focused on superhydrophobic materials, demonstrates wide applicability to a range of areas, particularly those focused on the development of high-strength coatings.

Biomimetic Superhydrophobic Films with an Extremely Low Roll-Off Angle Modified by F16CuPc via Two-Step Fabrication

Superhydrophobicity is the phenomenon of which the water contact angle (WCA) of droplets on a solid surface is greater than 150°. In the present paper, we prepare a superhydrophobic film with a structure similar to the surface of a lotus leaf, which is composed of polydimethylsiloxane (PDMS), zinc oxide (ZnO), a molecular sieve (MS) and 1,2,3,4,8,9,10,11,15,16,17,18,22,23,24,25-hexadecafluorophthalocyanine copper(II) (F₁₆CuPc). The F₁₆CuPc was used as the modifier to reduce the surface energy of the biomimetic micro-nanostructure. With the introduction of F₁₆CuPc, the superhydrophobic properties of the surface were enhanced so that the WCA and water roll-off angle could reach 167.1° and 0.5°, respectively. Scanning electron microscopy, X-ray energy spectrometry, and X-ray photoelectron spectroscopy analyses verified that the enhanced superhydrophobic properties of the film were mainly attributed to the modification of F₁₆CuPc. Finally, thermal, mechanical, and chemical stability studies, as well as the influences of UV and underwater immersion on the superhydrophobic film were investigated. This developed two-step fabrication method may be a potential direction for superhydrophobic surface fabrication due to its simple process, excellent superhydrophobic property, and favorable stability.

Single Step Synthesis and Functionalization of Nano Titania for Development of Multifunctional Cotton Fabrics

Synthesis and modification of nanoparticles to make them suitable to functionalise a substrate for various application fields involves many steps, which are complex, time-consuming, and sometimes require special equipment. This is a major drawback to meet rapid technological requirements. In this work, a procedure has been developed to modify TiO₂ nanoparticles by the sol-gel method at their synthesis stage using titanium tetraisopropoxide and modifying agents including ODS and GPTMS. The prepared nanoparticle finish can be used as it is without any further processing, thus eliminating the need for extra steps required to decorate them on some substrate. The nanoparticles were characterised by SEM, EDX, FTIR, XRD, and zeta potential. The adhesion of the obtained nanoparticles was tested by applying them to a cellulosic substrate. The obtained substrate was subjected to mechanical action and adhesion efficiency was estimated on the basis of UV transmittance and antibacterial properties that showed excellent results. The hydrophobic properties of the obtained nanoparticles were assessed by measuring water contact angles, which reached 157.9°, indicating their superhydrophobic nature. The developed procedure is facile and will be suitable for the engineering of multiple surfaces.

Polyimide based super-wettable membranes/materials for high performance oil/water mixture and emulsion separation: A review

This article reviews the application of highly heat and pressure resistant polyimide material for the development of membranes/materials that exhibit unique super-wettability, the characteristics pivotal for the efficient separation of oil-water mixture and emulsion. The polymerization of imide monomer in polyimide brings about the required porosity in the material, which in turn renders the crucial surface roughness, which is instrumental for establishing the desired super-wettability on the polyimide based membrane materials, in addition to the mechanical and thermal robustness. The membrane as the oil-water filtering medium can be either oil passing or water passing depends on the individual wettability of the membrane surface for oil and water, which in turn depend on the respective solid-liquid interfacial energy and the hierarchical surface roughness. Superhydrophobic/superoleophobic wetting characteristic of the surface repels water and allows oil to pass through the membrane medium, and the major disadvantage of this kind of oil/water separation is the rapid oil fouling of the membrane pores and the consequent less efficiency for oil water separation. On the other hand, the membrane surface engineered to have the Superhydrophilic/underwater superoleophobic wetting characteristics can be water passing, and the easy fouling of the membrane surface can be minimized. In the case of polyimide materials, there are lot of scopes to engineer the physical properties like surface energy and surface roughness of the membrane surface in order to obtain the required wettability. There have been many works focused on the application of different variants of polyimide materials for developing membrane for oil water separation. In this review, we present an itemized review of various works on polyimide materials based oil/water separation in terms of chemical, physical, structural and surface characteristics of the material.

Fabricating low-cost, robust superhydrophobic coatings with re-entrant topology for self-cleaning, corrosion inhibition, and oil-water separation

HYPOTHESIS

The superhydrophobic surfaces with re-entrant microstructures are known to provide robust superhydrophobicity by enhancing the energy barrier for Cassie-Baxter to Wenzel transition. However, the fabrication of such structured surfaces often involves sophisticated techniques and expensive ingredients.

EXPERIMENTS

Herein, a multifunctional, low-cost, and fluorine-free superhydrophobic coating with re-entrant surface topology was fabricated using fly ash (FA) and room-temperature-vulcanizing silicone. A systematic study was performed to evaluate the coating properties and durability. The robustness was evaluated as a function of particle size and inter-particle spacing. The performance in self-cleaning, corrosion inhibition and oil-water separation has been presented.

FINDINGS

The synthesized coatings are substrate-versatile and demonstrate superhydrophobic behavior. The close-packed coating of re-entrant FA particles attained via vibration compaction was seen to provide high robustness. The coatings retain their superhydrophobicity after multiple cycles of tape-peeling and exposure to environmental factors including temperature, pH, and UV radiation. These coatings exhibit excellent corrosion inhibition (corrosion efficiency > 99.999%), outperforming the majority of the previously reported superhydrophobic coatings. It also displays excellent self-cleaning property and high separation efficiencies in oil-water separation (>99%). We envision that such FA-based superhydrophobic coatings can solve the issues of synthesizing cheaper, sustainable, and robust superhydrophobic surfaces while simultaneously opening new avenues for FA utilization.

In Situ, One-Pot Method to Prepare Robust Superamphiphobic Cotton Fabrics for High Buoyancy and Good Antifouling

Multifunctional superamphiphobic cotton fabrics are in high demand. However, preparation of such fabrics is often difficult or complicated. Herein, a novel superamphiphobic fabric is constructed by a simple one-pot method with an in situ growth process. Under suitable alkaline conditions, dopamine (DA) can be oxidized to benzoquinone. Meanwhile, 3-aminopropyltriethoxysilane (APTES), 1H,1H,2H,2H-perfluorodecyltriethoxysilane (FAS-17) molecules undergo the hydrolysis reaction and bond together. Besides, benzoquinone can react with APTES by Schiff base and hollow nanoclusters can be finally obtained because of the steric hindrance effect of benzene ring and long alkyl chain. Such nanoclusters are formed on the surface of fabric, which endows the fabric with extreme liquid repellence. The effects of pH value and DA concentration on the surface morphology and lyophobic properties of the fabric are systematically studied. The water and pump oil contact angles of the superamphiphobic fabric obtained under the optimal reaction conditions can reach 160 and 151°, respectively. The lyophobicity of the fabric is maintained even after undergoing various harsh tests, showing significant durability and stability. In addition, the superamphiphobic fabric exhibits good antifouling and strong buoyancy ability. The superamphiphobic fabric can load 35 and 27.4 times its own weight in water and oil, respectively, which shows great potential in the field of functional textiles such as swimming suits, protective clothing, and life jackets in the future.

Organic Hollow Mesoporous Silica as a Promising Sandalwood Essential Oil Carrier

As film-forming agents, fillers and adsorbents, microplastics are often added to daily personal care products. Because of their chemical stability, they remain in the environment for thousands of years, endangering the safety of the environment and human health. Therefore, it is urgent to find an environmentally friendly substitute for microplastics. Using n-octyltrimethoxysilane (OTMS) and tetraethoxysilane (TEOS) as silicon sources, a novel, environmentally friendly, organic hollow mesoporous silica system is designed with a high loading capacity and excellent adsorption characteristics in this work. In our methodology, sandalwood essential oil (SEO) was successfully loaded into the nanoparticle cavities, and was involved in the formation of Pickering emulsion as well, with a content of up to 40% (w/w). The developed system was a stable carrier for the dispersion of SEO in water. This system can not only overcome the shortcomings of poor water solubility and volatility of sandalwood essential oil, but also act as a microplastic substitute with broad prospects in the cosmetics and personal care industry, laying a foundation for the preparation and applications of high loading capacity microcapsules in aqueous media.

Surface Engineering of Ceramic Nanomaterials for Separation of Oil/Water Mixtures

Oil/water mixtures are a potentially major source of environmental pollution if efficient separation technology is not employed during processing. A large volume of oil/water mixtures is produced via many manufacturing operations in food, petrochemical, mining, and metal industries and can be exposed to water sources on a regular basis. To date, several techniques are used in practice to deal with industrial oil/water mixtures and oil spills such as in situ burning of oil, bioremediation, and solidifiers, which change the physical shape of oil as a result of chemical interaction. Physical separation of oil/water mixtures is in industrial practice; however, the existing technologies to do so often require either dissipation of large amounts of energy (such as in cyclones and hydrocyclones) or large residence times or inventories of fluids (such as in decanters). Recently, materials with selective wettability have gained attention for application in separation of oil/water mixtures and surfactant stabilized emulsions. For example, a superhydrophobic material is selectively wettable toward oil while having a poor affinity for the aqueous phase; therefore, a superhydrophobic porous material can easily adsorb the oil while completely rejecting the water from an oil/water mixture, thus physically separating the two components. The ease of separation, low cost, and low-energy requirements are some of the other advantages offered by these materials over existing practices of oil/water separation. The present review aims to focus on the surface engineering aspects to achieve selectively wettability in materials and its their relationship with the separation of oil/water mixtures with particular focus on emulsions, on factors contributing to their stability, and on how wettability can be helpful in their separation. Finally, the challenges in application of superwettable materials will be highlighted, and potential solutions to improve the application of these materials will be put forward.

Multifunctional membranes with super-wetting characteristics for oil-water separation and removal of hazardous environmental pollutants from water: A review

Over the past few years, oil-water separation techniques have been widely researched due to influences of oil pollution. The oil pollution is significantly increasing day-by-day because of ever-increasing usage of oil in daily routine of humans and industrial activities. The separation of water from oil-water emulsions/mixtures through membrane technology has provided absolute necessary qualities such as low cost, eco-friendly, easy-operation and energy efficient. To build up the filter membranes with special super-wettability properties and bearing excellent multifunctional applications is highly attractive research area in current decade. However, evolution of membrane technology suffered many deficiencies including severe fouling, short-standing against high flow speed, surface wettability disorders, non-reusable and limited application. In this review article, we outline the recent advances in membrane technology with respect to special super-wettability properties, enhanced characteristics for purpose to serve oil-water separation, and more specifically its multifunctional applications. Therefore, this study is made for membranes having other than applications, in addition to oil-water separation. Further, the wetting phenomenon of these multifunctional membranes is addressed and highlighted the brief overview of surface wetting types including Superhydrophobic-Superoleophilic membranes, Superhydrophilic-Superoleophobic membranes, and Superhydrophilic-underwater Superoleophobic membranes. Moreover, relative fabrication procedures and multifunctional applications of developed multifunctional super-wetting membranes are also discussed along with wetting behavior. Finally, the current developments and achievements for oil-water separation multifunctional super-wetting membranes are concluded. Besides, it also explores the future challenges and obstacles associated to these membranes. Hence, this article provides brief overview of advancement of oil-water separation based multifunctional super-wetting membranes and ended with new thoughts of further modification/enhancement.

Multiscale-structured superhydrophobic/superoleophilic SiO2 composite poly(ether sulfone) membranes with high efficiency and flux for water-in-oil emulsions separation under harsh conditions

Multiscale-structured SiO₂ composite poly(ether sulfone) membranes (MSiCPESMs) are facilely prepared via the methods of nonsolvent induced phase separation and sol–gel.

Superhydrophobic nanoporous polymer-modified sponge for in situ oil/water separation

Developing an efficient and environmentally friendly strategy for oil-water separation is extremely important for practical application. In this study, a superhydrophobic and superoleophilic melamine sponge loaded with cross-linked and swellable polydivinylbenzene was successfully fabricated by a facile and effective one-step impregnation-curing method with adhesion of polydimethylsiloxane. The prepared sponge not only exhibited high oil absorption capacity, but it also enabled rapid oil collection in situ, which could be extended to practical application. Moreover, the modified superhydrophobic sponge showed excellent mechanical resistance and chemical stability. The surface morphology and chemical composition were characterized by scanning electron microscopy, X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy. This material has great development potential for large-scale oil spill clean-up and chemical spill accidents.

Waste cigarette filter as nanofibrous membranes for on-demand immiscible oil/water mixtures and emulsions separation

The rapid industrial growth and the frequent oil spill accidents have led to the large production of oily wastewater. Thus, it is urging to develop a low-cost and eco-friendly material to purify the oily wastewater. In our work, the waste cigarette filter as the raw material was used to prepare cigarette filter coated meshes (CFCMs) by a facile electrospinning approach. The as-prepared CFCMs prewetted with water or oil achieved the special wetting performance of underwater superoleophobicity or underoil superhydrophobicity without any further chemical modification. Hence, the cigarette filter coated meshes with larger or smaller pore size can be applied to on-demand immiscible oil/water mixtures (light or heavy oil/water mixtures) and oil/water emulsions separation (water-in-oil or oil-in-water emulsions), respectively. Moreover, the CFCMs still exhibited high separation efficiency larger than 99.9% for immiscible oil/water mixtures and emulsions after many cyclic testing. The work provides an application in oil/water separation for waste cigarette filters and contributes to reduce the pollution for environment from the waste cigarette filters.