Self-cleaning Properties Research Articles

Selective separation of tanshinone homologs by biocomposite membranes based on poly(ionic liquids) and natural fibers.

Membranes have been used as versatile tools for the separation of various natural products; however, the selective separation of structural analogs of natural products using membranes remains challenging. In this study, biocomposite membranes based on poly(ionic liquids) and different natural fibers (jute, cotton, or wool) were successfully prepared. Natural fibers can regulate the microstructure and improve the mechanical properties of membranes. Fourier transform infrared spectroscopy, nuclear magnetic resonance spectroscopy, scanning electron microscopy, X-ray photoelectron spectroscopy, atomic force microscopy, Brunauer-Emmett-Teller analysis, and thermo gravimetric analysis were used to characterize the membranes. The membranes were used to separate tanshinone homologs (tanshinone I, tanshinone IIA, cryptotanshinone, and dihydrotanshinone I), allowing cryptotanshinone to penetrate the membrane while rejecting tanshinone I. A maximal selectivity of 44.57% was obtained for the tanshinone homologs using a one-step separation protocol. These poly(ionic liquids)/natural fiber membranes possess high water flux, good self-cleaning, and good antibacterial properties. The membranes were effective in separating tanshinone homologs and have the potential to separate other natural homologs.

Construction of graphene oxide-doped carboxylated polyphenylene sulfide composite hydrophobic coatings with corrosion protection and self-cleaning properties on metal surfaces

Construction of graphene oxide-doped carboxylated polyphenylene sulfide composite hydrophobic coatings with corrosion protection and self-cleaning properties on metal surfaces

Modulating length/diameter ratio and phase of VO2 (A)/VO2 (B) nanobeams/nanofibers toward prominent microwave-absorbing, heat-conducting, self-cleaning, and mechanical properties

Modulating length/diameter ratio and phase of VO2 (A)/VO2 (B) nanobeams/nanofibers toward prominent microwave-absorbing, heat-conducting, self-cleaning, and mechanical properties

The magnesium sulfate whisker/Al2O3 superhydrophobic composite coating exhibits robust, corrosion-resistant, and delayed icing properties

Superhydrophobic coatings exhibit paramount significance in practical applications, yet they often confront durability challenges, notably their propensity to detach. In this study, by using epoxy resin as the intermediate layer, the upper coating consists of epoxy resin, micron-sized alkali magnesium sulfate whiskers and nanosized alumina. Using a simple spraying method, the contact angle of the composite coating was measured to be 154.8°, and the rolling angle was 3.5°. The results show that the prepared coatings are still superhydrophobic after 100 tape stripping and 1600cm sandpaper abrasion distance, proving that the coatings have good mechanical durability. Furthermore, in electrochemical tests superhydrophobic coating achieved 98.94% retardation efficiency compared to bare copper sheet. The delayed icing time of the superhydrophobic coated copper sheet is 7 times and 3.5 times longer at -15℃ and -20℃, respectively, compared with the bare copper sheet. Additionally, the coating has excellent self-cleaning and stain resistance properties and is suitable for use on a wide range of substrate surfaces.

Facile preparation of marine carrageenan hydrogel-coated steel mesh with superhydrophilic and underwater superoleophobic performance for highly efficient oil-water separation.

The discharge of oil-laden wastewater from industrial processes and the frequent occurrence of oil spills pose severe threats to the ecological environment and human health. Membrane materials with special wettability have garnered attention for their ability to achieve efficient oil-water separation by leveraging the differences in wettability at the oil-water interface. These materials are characterized by their simplicity, energy efficiency, environmental friendliness, and reusability. Among them, superhydrophilic-underwater superoleophobic membranes inspired by biomimetic fish scale structures have become a focal point of oil-water separation research due to their ability to repel oil contaminants effectively and maintain self-cleaning properties during the separation process. In this study, a stainless steel microporous two-dimensional metal mesh was employed as the substrate, coated with a carrageenan solution, and gelled in situ using sodium periodate as a crosslinking agent to fabricate a membrane with oil-water separation capabilities. The robust hydrophilicity of the carrageenan hydrogel imparts the coated stainless steel mesh with superhydrophilicity and underwater superoleophobicity (underwater oil contact angle ≥ 158°), along with excellent antifouling properties and recyclability. Experimental results demonstrate that the membrane achieved separation efficiencies of 98.87%, 98.08%, 98.14%, and 97.98% for silicone oil, canola oil, cyclohexane, and liquid paraffin, respectively, with a water flux of 1380.75L/m2·h. Remarkably, the membrane retained its initial separation efficiency even after 20 cycles. Additionally, the hydrogel exhibited exceptional stability under highly alkaline conditions, making it suitable for the treatment of complex oil-contaminated wastewater. PRACTITIONER POINTS: This study extracted a biocompatible and renewable hydrogel from marine red algae for application in oil-water separation. A superhydrophilic/underwater superoleophobic oil-water separation membrane was developed based on biomimetic fish scale structures. The membrane exhibited exceptionally high separation efficiency under pure gravity-driven conditions. The resulting material exhibits excellent oil repellency, self-cleaning capability, and recyclability.

Superhydrophilic self-cleaning cotton fabric with enhanced antibacterial and UV protection properties

AbstractA multifunctional cotton fabric with superior photocatalytic self-cleaning, antibacterial activity and UV protection was prepared through treatment with TiO2/Pt/SiO2 colloid, clarifying the influence of coating formulation on these functionalities. The photocatalytic activity of coated fabrics under UV and white-fluorescent light was tested and synergistic effects of Pt and silica in enhancing the self-cleaning property of fabrics were demonstrated. Various molar ratios of Pt:Ti (0.01%, 0.1%, 0.5%, and 1%) and Ti:Si (50/50 and 30/70) were utilised in synthesising the colloids. The self-cleaning performance of fabrics was assessed through monitoring coffee stain removal efficiency and methylene blue (MB) dye degradation kinetics. The results demonstrated an effective photocatalytic self-cleaning property on fabrics coated with TiO2/Pt/SiO2 colloids. Increasing the concentrations of Pt and silica both contributed to enhancing the self-cleaning property. The fabric coated with ternary TiO2/Pt/SiO2 30/1/70 colloid resulted in 43.5% higher MB dye removal compared with pure TiO2 after 3h irradiation under visible light. Moreover, the fabrics containing Pt 1% dopant possessed excellent bactericidal activity against both Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) bacteria, regardless of the presence of silica. While the addition of silica slightly reduced the UV protection of coated fabrics, increasing the concentration of Pt to 1% increased the protection level to 45 + . Various characterisation techniques including SEM, XPS, XRD, and TEM were employed to study the Pt-doping of TiO2 nanoparticles, as well as the effect of Pt concentration, superhydrophilicity of silica, and the chemical composition of coatings on the functionalities of fabrics.

Facile fabrication of nickel–cobalt phosphate-based fluorine-free superhydrophobic film with anti-corrosion and self-cleaning properties on Al alloy

Facile fabrication of nickel–cobalt phosphate-based fluorine-free superhydrophobic film with anti-corrosion and self-cleaning properties on Al alloy

Mechanical properties of lightweight photocatalytic marbelite

This study investigated the mechanical performance of lightweight photocatalytic marbelite (LPM). In the production of LPM, titanium dioxide (TiO2) and various fiber additives were used to impart self-cleaning properties to the LPM with photocatalytic effect. In the study, fibers were added to the LPM mix at different ratios (0%, 0.5%, 1%) and unit weight, ultrasound transmission rate, bending, splitting tensile and compressive strength tests were carried out on these specimens. The mixture was prepared with perlite and polyester resin and enriched with TiO2 and fiber additives. Perlite was used as an aggregate in the LPM and lightweighting properties were added to the specimens. The experimental results show that increasing the fiber content significantly improves the mechanical strength of the LPM. The improvement in bending strength reached 60%, while in compressive strength it reached 25% and in splitting tensile strength it reached 35%. With the addition of TiO2, the bending strength of LPM increased by 15%, while the compressive strength increased by 12% and the splitting tensile strength increased by 7%. These ratios were higher with increasing fiber content. These results suggest that LPM, which provide environmental benefits with their photocatalytic properties and improved mechanical performance, can be more effectively used in industrial applications.

Preparation of Waterborne Polyurethane Coatings with Enhanced Mechanical Properties and Superhydrophobic Surface

Waterborne polyurethane (WPU) coatings are recognized for their environmental friendliness and non-toxic nature. However, the presence of abundant hydrophilic groups within their polymer networks often restricts their hydrophobicity and mechanical performance. In this study, we utilized two distinct diols to design the molecular structure of WPU, aiming to enhance its mechanical properties by optimizing microphase separation and crystallinity, achieving a tensile strength of 24.13 MPa and a strain of 1350%. The resultant WPU exhibited high cohesion and abundant hydrogen bonding sites, which contributed to its strong adhesion of 8.31 MPa. Moreover, inspired by the self-cleaning function of lotus leaf-micro-nipples, we made the surface superhydrophobic by micro-nano structure. The irregularly embedded structure was formed between the WPU and SiO2@hbp. The surfaces of WPU coatings formed the peak-valley structure similar to the lotus leaf, achieving a water contact angle of 162° and a sliding angle near 1°. Additionally, the self-cleaning property of the coatings was preserved after 200 cycles of friction, each with a single friction distance of 40cm. The environmental friendliness and excellent self-cleaning capabilities of the coating highlight its potential for practical applications and provide a valuable reference for developing waterproof self-cleaning coatings.

Super-hydrophobic and photo-thermal anti-icing coatings comprising small-quantity tungsten carbide with liquid repellency, self-cleaning and anti-fouling properties

Super-hydrophobic and photo-thermal anti-icing coatings comprising small-quantity tungsten carbide with liquid repellency, self-cleaning and anti-fouling properties

Dandelion inspired multi-functional superhydrophobic bamboo scrimber with desirable humidity resistance

Bamboo scrimber is high value added biomass fiber composites from natural bamboo due to its excellent multiple properties. However, the hydrophilicity of bamboo scrimber make it being susceptible to mold, fungi decay, colour changing and cracking during outdoors application. Therefore, wind blowing dandelion inspired multi-functional superhydrophobic bamboo scrimber was fabricated by spraying solution of Cu2O nanoparticles (NPs) modified phenol formaldehyde (PF) resin, immersing ethanol solution of stearic acid, followed by growth of copper stearate nanowires. The superhydrophobic bamboo scrimber exhibited desirable chemical and mechanical durability, liquid permeability, ultraviolet resistance, self-cleaning and anti-fouling properties, as well as mold resistance. More importantly, the modified bamboo scrimber performed best humidity resistance over 136 days under relative humidity of 85 % in this field, which can be attributed to the dense nanostructure of copper stearate nanowires. Furthermore, a specific bamboo cellulose crystalline model from natural bamboo to bamboo scrimber was firstly proposed to support the improvement of hardness. This work provide an biomimetic strategy for bamboo scrimber superhydrophobic modification, and it’s also innovative to promote the high value development of biomass composites.

TA/PVP hydrogel coating enhanced photo-Fenton membranes with antifouling and self-cleaning properties for efficient oil–water emulsion separation

TA/PVP hydrogel coating enhanced photo-Fenton membranes with antifouling and self-cleaning properties for efficient oil–water emulsion separation

Constructing industrial lignin into robust and multifunctional superhydrophobic coating for effective anti-icing.

Using renewable materials as primary components for constructing superhydrophobic coatings is an effective strategy for enhancing the environmental sustainability of anti-icing technologies. Alkali lignin, a by-product of the pulp and paper industry, was graft-modified with 1H, 1H, 2H, 2H-perfluorooctyltrichlorosilane to create a robust and multifunctional superhydrophobic coating for effective anti-icing. The results demonstrated that the industrial lignin-based coating achieved a contact angle of 162.1°. Its robustness was evidenced by the fact that the contact angle showed no significant change after 400 vertical drop hammer impacts (with 100g weights) and 900cm of abrasion with 800-grit sandpaper. Furthermore, the coating versatility was confirmed through excellent self-cleaning properties, ultraviolet (UV) aging resistance, high-temperature durability, and substrate applicability. These characteristics provided a solid foundation for use of anti-icing coatings in extreme environmental conditions. More importantly, the superhydrophobic aluminum alloy samples exhibited outstanding anti-icing properties, as confirmed by low-temperature freezing delay and durability tests. The freezing time of the water droplets on the aluminum alloy sample was extended threefold, and the coating remained superhydrophobic for 10days at -24°C. This study offers new insights into the development of environmentally friendly anti-icing coatings and the value-added utilization of industrial lignin.

Underwater superoleophobic TiO2/porous metal matrix with self-cleaning properties for high performance oil/water separation

Underwater superoleophobic TiO2/porous metal matrix with self-cleaning properties for high performance oil/water separation

Construction of superhydrophobic PDMS@PS-SiO2 films with self-cleaning properties via a simple template approach for efficient water harvesting

Superhydrophobic materials have a wide range of applications in the fields of anticorrosion, anti-dust, anti-ice and anti-fouling due to their self-cleaning, anti-wetting and anti-bacterial properties. However, there are problems in the preparation process, such as cumbersome processes, inconsistent properties of the prepared hydrophobic surfaces, and environmental pollution by fluoropolymers. Therefore, it is especially critical to develop a simple method to prepare green and efficient superhydrophobic surfaces. Here, a simple template method is used to prepare superhydrophobic surfaces. The Polystyrene (PS) honeycomb patterned film was used as a template, and the microstructure inside the pores of the PS film was changed by filling silica particles inside the template. Reproduction of the surface microstructure of PS films using polydimethylsiloxane (PDMS). The shape and size of the template structure are adjusted to regulate the surface microstructure, which in turn achieves the control of the overall hydrophobicity. The transition from PDMS hydrophobicity to superhydrophobicity was achieved by changing the structure of the PS film surface. The PDMS@PS-SiO2 film achieved a water contact angle of 153°, an increase of 48° compared to the original film. Tested at different temperatures and pH, PDMS@PS-SiO2 film has good stability performance. Immersing the film in pollutants still maintains its own cleaning properties and is not easily contaminated for long-term use. The morphology of the film surface was observed using electron microscopy to demonstrate the successful preparation of the film as well as to explore the reason for the variation of the hydrophobic performance. In addition, using PDMS@PS-SiO2 film as the substrate of the hydrophobic film, the bionic water-collecting film was prepared with a water-collecting performance of 20.12 ± 0.15 mg min−1 cm−2. The reuse of mist was achieved. This method provides a new idea for the preparation of superhydrophobic surfaces and solving the problem of water shortage.

Fabrication of superhydrophobic transparent coatings prepared by spraying dual-sized silica particles

Abstract Photovoltaic modules exposed to severe wind and sand conditions over extended periods often accumulate dust, significantly impacting their power generation efficiency. Superhydrophobic self-cleaning coatings present a promising solution to mitigate this issue. In this study, a SiO2/PU coating was applied to glass substrates using a combined sol–gel spraying technique. The sol system comprised a mixture of SiO2 particles with diameters of 20 nm and 200 nm, enabling the construction of a micro-nano structure that enhances surface hydrophobicity. The SiO2/PU coatings prepared with mixed particle sizes demonstrated significant improvements in contact angle, rolling angle, self-cleaning, and antifouling properties compared to those made with a single particle size, achieving a water contact angle of 164.52°. Furthermore, the prepared SiO2/PU coatings possess excellent stability and transmittance. It is anticipated that this superhydrophobic SiO2/PU coating will be a candidate for anti- dust applications in photovoltaic modules.

Candle soot nanoparticles covered femtosecond laser-induced graphene toward multifunctional wooden houses

Laser-induced graphene (LIG) is an innovative material that can be used in the construction of smart wood houses due to its high electrical and thermal conductivity. However, potential practical challenges such as fire hazards, and the complexity of daily cleaning are limitations in such an application. In this study, we utilized femtosecond laser direct writing technology to create femtosecond laser-induced graphene (FLIG) on flame retardant cork. The FLIG surface was then coated with multi-scale candle soot particles to incorporate carbon black (CB-FLIG) superhydrophobic surface properties. Here we demonstrate CB-FLIG as a raw material for electronic components in multifunctional wooden houses. The infrared emissivity of the CB-FLIG surface was as high as 97.2 % and the electric heating performance was good. As such, it can be used as an electric heater in the winter, and we achieved room temperature control at a comfortable 24.9 °C with 4 V voltage in a model house. Also, the water contact angle was 151.2°, giving CB-FLIG self-cleaning properties. Ultimately, we demonstrate the application of CB-FLIG in the field of smart home components such as electrical wiring, electric heaters, fire protection, and self-cleaning, increasing functionality while reducing the need for routine maintenance. This study lays a robust foundation for state-of-the-art devices within smart timber houses and significantly propels the development of versatile, interconnected wooden dwellings.

An Environmentally Friendly Superhydrophobic Wood Sponge with Photo/Electrothermal Effects Prepared from Natural Wood for All-Weather High-Viscosity Oil-Water Separation.

Rapid industrial development has led to increased crude oil extraction and oily wastewater discharge. Achieving oil-water separation and marine oil adsorption in a cost-effective, efficient, and environmentally friendly manner remains a global challenge. In this work, natural wood was chemically treated to prepare a degradable and environmentally friendly wood sponge structure. In situ polymerization and spraying methods were used to produce an environmentally friendly oil-water separation sponge with superhydrophobic and superoleophilic properties (Fe3O4@P-P@WS). Fe3O4@P-P@WS had excellent superhydrophobicity (WCA = 154.2°) and self-cleaning properties. Additionally, Fe3O4@P-P@WS could convert solar and electrical energy into thermal energy, reaching a surface temperature of 74 °C under sunlight irradiation with an intensity of 1.0 kW m-2. When a voltage of 9 V was applied, the surface temperature reached 120.5 °C. Moreover, under the suction of a vacuum pump or the action of gravity, the continuous separation of highly fluid oil substances was achieved. The designed Fe3O4@P-P@WS offers advantages such as easily obtained raw materials, energy efficiency, simple preparation, and the ability to solve secondary pollution issues, providing a new technology for cleaning organic matter in industrial wastewater discharge and for round-the-clock cleaning of high-viscosity crude oil leaked during offshore oil exploitation.

The Effect of TiO2 as a Photocatalytic Paint in The Indoor Air Purification Process

Photocatalysis has applications in various fields, such as in air purification devices and even in coatings, where it can be incorporated into paint formulations to take advantage of its air purification and self-cleaning properties. This report looks not only at the process of photocatalysis, but also at studies that have been carried out on its incorporation into coatings using titanium dioxide (TiO2). TiO2 is commercially available and can be synthesized in the laboratory to improve its performance in air purification and decontamination of various pollutants. In addition, studies into enhancing TiO2 semiconductor materials with a photocatalytic system, such as the inclusion of manganese, were emphasized. These studies presented findings on boosted decontamination performance, which is critical for enhancing indoor air quality through the elimination of harmful gases and organic compounds. Volatile organic compounds, such as formaldehyde, toluene, benzene, and NOx, have extremely toxic health effects. Every year, indoor and outdoor air pollution causes a significant number of deaths. Considering that people spend more than 80% of their time indoors, the filtration of indoor air is even more important. Therefore, this article presents some studies on the further development of photocatalytic materials and technologies for the commercial application of photocatalytic paints. Commercial photocatalytic paints containing TiO2 doped with magnesium (Mn), silicate paints and water-based styrene acrylic paints were investigated, focusing on their ability to reduce VOC emissions.

Photocatalytic Elimination of Nitrogen Oxides (NOx), Ozone, BAP and Organic Pollutants from the Contaminated Air in Prague and Milan - 12 Months Field Study

Smart Cities start with clean air, clean water, clean look, pleasant environment and energy savings. Data collected in a 12 month field study clearly demonstrate that photocatalytic technology (i.e. FN NANO) is a convenient, energy and cost efficient solution to the air pollution problem. New methodology to determine the depollution efficiency of urban structures on 3D printed objects inside a "City reactor" will be presented.Daylight energy activated photocatalytic surface shows a strong electron deficiency of 3.2eV (1), and have enough power to break down molecules of polluting compounds such as nitrogen oxides (2), ozone (3), organic volatile compounds, benzo-a-pyrene and other harmful pollutants.UV + TiO2 → TiO2 (h + e−) 3,2eV (1)NO (hv,TiO2)→(NO2)ads.+ H2O → NO3 − (2)2O3 + hv → 3O2 (3)Lab studies carried out over the past 15 years determine that facades painted with photocatalytic coating can easily compensate for emissions from the automobile traffic [1]. These lab data were confirmed by our long-term field study in real conditions of the polluted city of Prague (CR) and Milan (IT).Initially, there was a question, if the street mixture of pollutants will degrade on the photocatalytic surface with the same rate as the individual compounds in the lab [2,3]. Our study shows that photocatalytic degradation of pollutants in the real environment is even more efficient than the ISO 22197 based lab measurements. The highest efficiency we could measure with real air was 80% elimination of NOx. More importantly, the long-term average (12 months/all seasons) indicates 42% DeNOx efficiency. This study clearly demonstrates that photocatalysis can be used as an inexpensive coating technology to improve the quality of air in polluted cities.Our former studies showed high efficiency of the composite FN NANO coatings for removal of VOCs [4]. This was confirmed by measurements in the real conditions of the polluted cities of Prague and Milan. In addition, these studies demonstrated that concentrations of ozone are instantly converted into harmless molecules of oxygen on the photocatalytic surface [3]. The intensity of UV radiation determines the formation of ozone during the day, but the same radiation, in combination with the photocatalytic surface, is able to eliminate these ozone emissions. Relative air humidity does not impact the function of the photocatalytic coating in contrast to the layer of TiO2 photocatalytic standard Evonik P25 (Table 1). The initial concentration of ozone of 100 ppbv can be regularly found outdoors on sunny days.Table 1 Photocatalytic removal of ozone Relative humidity (%) FN NANO2 Conversion (%) P25 Conversion (%) 0 42 42 50 40 33 100 33 13 The photocatalytic surface not only cleans the air, but at the same time, it protects facades from UV radiation and soiling due to the self-cleaning properties of the photocatalytic coating. It prolongs facade life, and save money on maintenance and works as an giant air purifier.Some of these coatings have a significant cooling effect, measured by the Cool Roof Council, suitable for cooling of the heat islands (cities).Standard city model for prediction and mapping of spreading emissions was used to map disappearance of the nitrogen oxides pollutants. It provided valuable information on modeling and quantification of the street canyon photocatalytic air depollution. Over 10 % of elimination of pollutants was measured and can be expected in the street canyons [5].All these effects are efficient, inexhaustible and long lasting, presenting a new standard in the urban architecture and environmental planning.Keywords: FN NANO® photocatalytic coatings, self-cleaning coatings, decontamination, air cleaning, NOx, ozone, VOCs, BAP.Acknowledgements. This project was realized with the financial support from the Ministry of Industry and Trade of the Czech Republic (TRIO FV 40209)References[1] R. Zouzelka, J. Rathousky, Photocatalytic abatement of NOx pollutants in the air using commercial functional coating with porous morphology, Appl. Catal. B Environ. 217 (2017) 466–476.[2] Mikyskova, E., Martiniakova, I., Zouzelka, R. & Rathousky, J. (2022): Photocatalytic NOx abatement: The effect of high air-flow velocity, Environmental Technology & Innovation.[3] Zouzelka, R., Martiniakova, I., Muzikova, M., Mikyskova, E., & Rathousky, J. (2022): Photocatalytic Abatement of Ozone, VOC and NOx Pollutants in the Air Stream, Journal of Industrial and Engineering Chemistry[4] Namrata Pathaka, at el., Efficacy of photocatalysis and photolysis systems for the removal of ethylene under different storage conditions; Postharvest Biology and Technology 147 (2019) 68–77[5] Nosek at el.,The role of flow structures in the effective removal of NOx pollutants by a TiO2-based coating in a street canyon; Journal of Environmental Chemical Engineering 11 (2023) 109758 Figure 1