Self-cleaning Potential Research Articles

Proposing a new approach to the selection of material portfolio using a combination of data mining and optimisation methods

The present paper aims to provide a new framework for the selection of a portfolio of materials. This paper shows that, compared with the traditional methods in the selection of materials, how the new materials are analysed based on new ideas. The case study is materials required for production of tile glaze in both traditional and modern methods. Modelling in this study was done based on mathematical description approach. The results of execution of feature selection algorithm revealed that important factors in the selection of glaze for production of tile in both traditional and modern methods include cracking, self-cleaning, uniformity, water absorption, and market potential. In addition, the results of K-means algorithm showed that all the materials of choice for production of tile glaze are not placed in a single cluster. Therefore, each cluster should be evaluated separately. Unlike the classical approaches to the selection of materials, in the new approach, candidates for the selection of tile glaze are firstly clustered by K-means algorithm. Each cluster is independently ranked using free disposal hull model. Free disposal hull is a mathematical programming model based on data envelopment analysis. The final optimised portfolio of materials was determined using the genetic algorithm.

Bioinspired Hairy Crab Claw Polymer Surface with Excellent Self-Cleaning Wettability in Muddy or Oil-Contaminated Water.

The hairy crab Eriocheir sinensis lives in muddy freshwaters such as ponds and paddy fields. The crab's claw features dense patches of setae and exhibits an excellent self-cleaning surface in muddy waters. This study examined the micronano structure and wettability properties of the crab claw. The results showed that the claw consists of 3D cross-linked fibers with a hierarchical micronano structure, and the main chemical composition of these fibers was determined chitosan molecules. The claw also has special superoleophobic and self-cleaning properties in muddy water. Inspired by the structure of the crab claw, 3D-layered micro/nanostructures with poly(vinyl alcohol)/chitosan/poly(N-isopropylacrylamide) were prepared by electrospinning and in situ polymerization. This novel bioinspired polymer surface exhibits superhydrophilicity in the air, superoleophobicity underwater (with an oil contact angle of 163°), and excellent self-cleaning potential in muddy water.

Protonated g-C3N4/Ti3+ self-doped TiO2 nanocomposite films: Room-temperature preparation, hydrophilicity, and application for photocatalytic NOx removal

Fabrication of photocatalysis films with good adhesion, hydrophilicity, and high activity on substrates at room temperature is essential for their application in air pollution control. Herein, functionalized transparent composite films containing ultrathin protonated g-C3N4 (pCN) nanosheets and Ti3+ self-doped TiO2 nanoparticles (pCN/TiO2) were fabricated on glass at room temperature. Thickness of the films measures 80 nm with surface roughness of 7.16 nm. The adhesion ability was attributed to the viscosity of TiO2 sol, which served as “chemical glue” in the films. The high photo-induced hydrophilicity demonstrated their self-cleaning potential. pCN/TiO2 films showed remarkably high visible-light-driven activity in terms of NO removal in a continuous-flow mode. Photoelectrochemical tests demonstrated the superior charge separation efficiency of pCN/TiO2 films compared with that of pristine TiO2. As identified by electron spin resonance spectra, O2− and OH radicals were the key reactive species involved in NO removal. The possible mechanism for photocatalytic NO oxidation was proposed. Potential cytotoxicity of pCN/TiO2 films was evaluated by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay to ensure the biosecurity. This work provides a facile route to fabricate nanocomposite films under ambient temperature. The nanocomposite films were characterized by photo-induced hydrophilicity, high NO removal efficiency, and good biocompatibility, showing its potential in large-scale application.

Laser Tailoring the Surface Chemistry and Morphology for Wear, Scale and Corrosion Resistant Superhydrophobic Coatings.

A strategy, combining laser chemical modification with laser texturing, followed by chemisorption of the fluorinated hydrophobic agent was used to fabricate the series of superhydrophobic coatings on an aluminum alloy with varied chemical compositions and parameters of texture. It was shown that high content of aluminum oxynitride and aluminum oxide formed in the surface layer upon laser treatment allows solving the problem of enhancement of superhydrophobic coating resistance to abrasive loads. Besides, the multimodal structure of highly porous surface layer leads to self-healing ability of fabricated coatings. Long-term behavior of designed coatings in "hard" hot water with an essential content of calcium carbonate demonstrated high antiscaling resistance with self-cleaning potential against solid deposits onto the superhydrophobic surfaces. Study of corrosion protection properties and the behavior of coatings at long-term contact with 0.5 M NaCl solution indicated extremely high chemical stability and remarkable anticorrosion properties.

Hydrophobicity of Surfaces Coated with Functionalized Titanium Dioxide Nanoparticles

Hydrophobic surfaces are eyed for their self-cleaning ability because water droplets can roll on them (instead of clinging), thus the surface have capability to remove dirt. Hydrophobic surfaces were created by coating functionalized Titanium Dioxide-based paint. The paint was fabricated by reacting fluorosilane molecules in ethanol with titanium dioxide nanoparticles. Ethanol also serves as the volatile suspension medium that evaporates when the paint is coated on surfaces. The paint was coated on different surfaces by simple dipping. Contact angle of coated aluminum sheet, soda-lime glass, filter paper and silicon carbide polishing paper showed hydrophobicity. Water droplets are made to roll on coated soda-lime glass at angle of 0.057°. The ability of water droplets to roll highlights the coated surface self-cleaning potential.

Ammonium-nitrate dynamics in the critical zone during single irrigation events with untreated sewage effluents

Previous studies in the Mezquital Valley evidenced that irrigation with untreated sewage effluent supplies two- to tenfold larger nitrogen doses to crops than common fertilizer recommendations. However, nitrate concentrations in the groundwater are only slightly above threshold concentrations for drinking water. To understand the N dynamics in this agroecosystem, we quantified nitrogen inputs, outputs, and transformations within the rooting zone and in the vadose zone down to the aquifer (i.e., in the critical zone). Single irrigation events were monitored in three different fields cropped with either annual rye grass (Lolium rigidum) or oats (Avena sativa L.) harvested for fodder. For each irrigation event, the total amount of water entering and leaving the field was quantified with a flowmeter. Soil pore water was collected with either microsuction cups or observation wells and groundwater was sampled at two wells. All water samples were analyzed for total nitrogen (Nt), ammonium nitrogen (NH4 +–N), nitrate nitrogen (NO3 −–N), chloride (Cl−1), and pH. Organic N was calculated as the difference between total N and inorganic N. The water tension and the soil water content were monitored before, during, and after the irrigation with tensiometers and TDR probes, respectively, installed at different depths and at three sites within each field. Batch experiments were conducted to assess the NH4 + adsorption capacity of the soils. The irrigations added 537 to 727 kg ha−1 N in form of organic N (40 %) and NH4 +–N (60 %) to the fields. Crops absorbed 65 % of the N and 31 to 66 kg NO3 −–N ha−1 leached out beyond the rooting zone (>40 to 130 cm). Batch experiments evidenced an ammonium adsorption capacity of 43 and 53 % of the input ammonium mass. Nitrification dominated over denitrification as the water infiltrated through the soil, evidenced by changes in nitrate concentrations and pH values in the soil pore water. The behavior of the total N/Cl ratio with depth indicated possible N losses due to NH3 volatilization at the field surface, a temporal withdrawal of N from the soil solution due to NH4 +–N adsorption in the rooting zone, as well as probable denitrification losses in the vadose zone. Although the studied agroecosystem muses the large N inputs relative efficiently, between 7 and 10 % of the added N with each irrigation leaches beyond the crop root zone as nitrate. This is triggered by overflow irrigation, since up to 8,699,000 L of water with N concentrations of up to 50 mg total N L−1 infiltrate rapidly through macropores beyond the rooting zone. Additionally, ammonia volatilization and denitrification seem to be occurring. The latter could provide a self-cleaning potential to the system, if it reaches N2 and needs further verification. Nevertheless, N inputs to the system should match crop uptake to avoid groundwater and atmospheric pollution.

Long term self-cleaning and photocatalytic performance of anatase added mortars exposed to the urban environment

Building envelope materials containing titanium dioxide have been proposed to exploit their photoactivated depolluting and self-cleaning potential, but a full appraisal of their durability and long-term performance is still missing. This study reports a two-year campaign of natural exposure in Milano, Italy, of photoactive and non-photoactive fiber-reinforced mortars, analyzing the evolution of lightness, solar reflectance, porosity and photoactivity. After aging, photoactive samples showed limited color variation. The photocatalytic activity of TiO2 containing samples, characterized with dye degradation tests, was minimal after aging. Then, after alternated cycles of UV–Vis irradiation and rinsing, almost 70% of the initial photocatalytic efficiency was recovered.

Effective bioremediation strategy for rapid in situ cleanup of anoxic marine sediments in mesocosm oil spill simulation.

The purpose of present study was the simulation of an oil spill accompanied by burial of significant amount of petroleum hydrocarbons (PHs) in coastal sediments. Approximately 1000 kg of sediments collected in Messina harbor were spiked with Bunker C furnace fuel oil (6500 ppm). The rapid consumption of oxygen by aerobic heterotrophs created highly reduced conditions in the sediments with subsequent recession of biodegradation rates. As follows, after 3 months of ageing, the anaerobic sediments did not exhibit any significant levels of biodegradation and more than 80% of added Bunker C fuel oil remained buried. Anaerobic microbial community exhibited a strong enrichment in sulfate-reducing PHs-degrading and PHs-associated Deltaproteobacteria. As an effective bioremediation strategy to clean up these contaminated sediments, we applied a Modular Slurry System (MSS) allowing the containment of sediments and their physical–chemical treatment, e.g., aeration. Aeration for 3 months has increased the removal of main PHs contaminants up to 98%. As revealed by CARD-FISH, qPCR, and 16S rRNA gene clone library analyses, addition of Bunker C fuel oil initially affected the activity of autochthonous aerobic obligate marine hydrocarbonoclastic bacteria (OMHCB), and after 1 month more than the third of microbial population was represented by Alcanivorax-, Cycloclasticus-, and Marinobacter-related organisms. In the end of the experiment, the microbial community composition has returned to a status typically observed in pristine marine ecosystems with no detectable OMHCB present. Eco-toxicological bioassay revealed that the toxicity of sediments after treatment was substantially decreased. Thus, our studies demonstrated that petroleum-contaminated anaerobic marine sediments could efficiently be cleaned through an in situ oxygenation which stimulates their self-cleaning potential due to reawakening of allochtonous aerobic OMHCB.

Hierarchically engineered membrane surfaces with superior antifouling and self-cleaning properties

In nature, surfaces simultaneously possessing antifouling and self-cleaning properties allow living systems to sustain diverse functions. Integrating these features into synthetic surfaces will open a novel avenue to advanced surface-based or surface-governed technologies for medical, industrial, ocean, and environmental applications. In this study, we report in situ engineered porous membrane surfaces with hierarchical structure: the external membrane surfaces are covered with zwitterionic (hydrophilic) and low surface energy brushes, endowing the membranes with superior antifouling and self-cleaning abilities. The surface composition, hydrophilicity and surface energy are assessed for the valuation of the antifouling and self-cleaning potential of the membranes. When utilized for model wastewater treatment, the membrane fouling is exquisitely suppressed: permeation flux-decline is decreased to an ultralow level (less than 1%) and permeation flux recovery after simple hydraulic washing is retained at nearly 100%. The present method can be extended to the construction and modification of a broad range surfaces.

Biofilms in drinking water and their role as reservoir for pathogens

Most microorganisms on Earth live in various aggregates which are generally termed "biofilms". They are ubiquitous and represent the most successful form of life. They are the active agent in biofiltration and the carriers of the self-cleaning potential in soils, sediments and water. They are also common on surfaces in technical systems where they sometimes cause biofouling. In recent years it has become evident that biofilms in drinking water distribution networks can become transient or long-term habitats for hygienically relevant microorganisms. Important categories of these organisms include faecal indicator bacteria (e.g., Escherichia coli), obligate bacterial pathogens of faecal origin (e.g., Campylobacter spp.) opportunistic bacteria of environmental origin (e.g., Legionella spp., Pseudomonas aeruginosa), enteric viruses (e.g., adenoviruses, rotaviruses, noroviruses) and parasitic protozoa (e.g., Cryptosporidium parvum). These organisms can attach to preexisting biofilms, where they become integrated and survive for days to weeks or even longer, depending on the biology and ecology of the organism and the environmental conditions. There are indications that at least a part of the biofilm populations of pathogenic bacteria persists in a viable but non-culturable (VBNC) state and remains unnoticed by the methods appointed to their detection. Thus, biofilms in drinking water systems can serve as an environmental reservoir for pathogenic microorganisms and represent a potential source of water contamination, resulting in a potential health risk for humans if left unnoticed.

Land Use and Water Quality Along a Mekong Tributary in Northern Lao P.D.R.

Improving access to clean water has the potential to make a major contribution toward poverty reduction in rural communities of Lao P.D.R. This study focuses on stream water quality along a Mekong basin tributary, the Houay Xon that flows within a mountainous, mosaic land-use catchment of northern Lao P.D.R. To compare direct water quality measurements to the perception of water quality within the riparian population, our survey included interviews of villagers. Water quality was found to vary greatly depending on the location along the stream. Overall, it reflected the balance between the stream self-cleaning potential and human pressure on the riparian zone: (i) high bacteria and suspended load levels occurred where livestock are left to free-range within the riparian zone; (ii) very low oxygen content and high bacteriological contamination prevailed downstream from villages; (iii) high concentrations of bacteria were consistently observed along urbanized banks; (iv) low oxygen content were associated with the discharge of organic-rich wastewater from a small industrial plant; (v) very high suspended load and bacteria levels occurred during flood events due to soil erosion from steep cultivated hill slopes. Besides these human induced pollutions we also noted spontaneous enrichments in metals in wetland areas fed by dysoxic groundwater. These biophysical measurements were in agreement with the opinions expressed by the majority of the interviewees who reported poor and decreasing water quality in the Houay Xon catchment. Based on our survey, we propose recommendations to improve or maintain stream water quality in the uplands of northern Lao P.D.R.

State of the art of TiO<sub>2</sub> containing cementitious materials: self-cleaning properties

Due to the physico-chemical characteristics of cementitious materials the aesthetic quality of these materials tend to decrease easily. On the other hand, the photocatalytic activity produced by TiO 2 loaded cementitious materials have recently allowed them to include self-cleaning and air-purifying properties. However, because a better understanding of these properties is still needed, only a limited number of these materials is present in the construction market. As a strategy to improve this situation, non standards tests based on photodegradation of organic dyes have become widely used to evaluate the photocatalytic action of the different materials. Today, a wide spectrum of non easily comparable results have been produced. In order to improve this situation, this paper focuses on the description of the developed laboratory tests as well as on the evaluation of the self-cleaning potential of the first buildings containing TiO 2 . Finally, future research challenges in this field are identified.

A microbiological study of the self-cleaning potential of oily Arabian Gulf coasts

Due to the active production and transport of crude oil in the Arabian Gulf region, the Arabian Gulf coasts are routinely polluted with oil. Therefore, such coasts have been subject of studies aiming at assessing the roles of indigenous microbial consortia in cleaning these environments. In the present study, epilithic microbial communities along Kuwait coasts were studied for their oil degradation potential. Gravel particles coated with deep green biofilms were collected from four coastal sites in autumn, winter, and spring. Phototrophs in these consortia were determined in terms of their chlorophyll a contents and identified by their morphological characteristics. Total bacteria were counted microscopically and cultivable bacteria by the dilution plating method on nutrient agar as well as on inorganic medium containing oil as a sole source of carbon and energy. The bacterial community structures were also characterized and compared by denaturing gradient gel electrophoresis (DGGE). Epilithic biomass samples from the four sites in the three seasons were rich in diatoms and picocyanobacteria as well as total bacteria. Direct counting gave bacterial numbers per square centimeter gravel surface of 2 to 6 x 10(7) cells depending on the sampling site and season. Cultivable bacterial numbers on nutrient agar and crude oil as a sole source of carbon were 3 x 10(3) to 8 x 10(4) and 1 x 10(3) to 7 x 10(3) cells/cm(2) gravel surface, respectively. The DGGE profiles of epilithon biomass samples revealed major 16S rDNA bands that matched bands of pure oil-utilizing bacterial isolates. The microbial communities showed a degree of consistency in all sites and seasons. The microbial consortia coating gravel particles are potentially suitable tools for self-cleaning of oily Gulf coasts. They are rich in oil-utilizing bacteria whose activities are probably enhanced by oxygen produced by the phototrophic partners in the consortia. The combination of conventional microbiological analysis with molecular approaches gives an enhanced idea about natural microbial communities especially those with environmental application potential.

Alkaliphilic and halophilic hydrocarbon-utilizing bacteria from Kuwaiti coasts of the Arabian Gulf

Green animate materials from the intertidal zone of the Arabian Gulf coast accommodated more alkaliphilic and halophilic bacteria than inanimate materials. The alkaliphilic oil-utilizing bacteria, as identified by their 16S ribonucleic acid sequences, belonged to the following genera arranged in decreasing frequences: Marinobacter, Micrococcus, Dietzia, Bacillus, Oceanobacillus, and Citricoccus. The halophilic oil-utilizing bacteria belonged to the genera: Marinobacter, Georgenia, Microbacterium, Stappia, Bacillus, Isoptericola, and Cellulomonas. Most isolates could grow on a wide range of pure n-alkanes and aromatic compounds, as sole sources of carbon and energy. Quantitative gas liquid chromatographic analysis showed that individual isolates attenuated crude oil and representative pure hydrocarbons in culture. The optimum pH for most of the alkaliphilic genera was pH 10, and the optimum salinity for the halophiles ranged between 2.5 and 5% NaCl (w/v). It was concluded that as far as their microbial makeup is concerned, oily alkaline and saline intertidal areas of the Kuwaiti coasts have a self-cleaning potential.

ASPECTS AND PROBLEMS OF NATURAL SELF-CLEANING POTENTIAL EVALUATION FOR URBANIZED ENVIRONMENT

The article deals with the concept of natural self-cleaning potential. It contains a description of available urbanized environment natural self-cleaning potential evaluation methodics and specific methods employed. Groups of criteria, producing different influence on self-cleaning geopotential were distinguished. Each criterion was evaluated by grades – related with parameters of impact factors – taking into consideration its rank in the general system of evaluation.

Pyrene Degradation in Forest Humus Microcosms with or without Pine and its Mycorrhizal Fungus

The mineralization potential of forest humus and the self-cleaning potential of a boreal coniferous forest environment for polycyclic aromatic hydrocarbon (PAH) compounds was studied using a model ecosystem of acid forest humus (pH = 3.6) and pyrene as the model compound. The matrix was natural humus or humus mixed with oil-polluted soil in the presence and absence of Scots pine (Pinus sylvestris L.) and its mycorrhizal fungus (Paxillus involutus). The rates of pyrene mineralization in the microcosms with humus implants (without pine) were initially insignificant but increased from Day 64 onward to 47 microg kg(-1) d(-1) and further to 144 microg kg(-1) d(-1) after Day 105. In the pine-planted humus microcosms the rate of mineralization also increased, reaching 28 microg kg(-1) d(-1) after Day 105. The 14CO2 emission was already considerable in nonplanted microcosms containing oily soil at Day 21 and the pyrene mineralization continued throughout the study. The pyrene was converted to CO2 at rates of 0.07 and 0.6 microg kg(-1) d(-1) in the oily-soil implanted microcosms with and without pine, respectively. When the probable assimilation of 14CO2 by the pine and ground vegetation was taken into account the most efficient microcosm mineralized 20% of the 91.2 mg kg(-1) pyrene in 180 d. The presence of pine and its mycorrhizal fungus had no statistically significant effect on mineralization yields. The rates of pyrene mineralization observed in this study for forest humus exceeded the total annual deposition rate of PAHs in southern Finland. This indicates that accumulation in forest soil is not to be expected.

Pyrene Degradation in Forest Humus Microcosms with or without Pine and its Mycorrhizal Fungus

The mineralization potential of forest humus and the self-cleaning potential of a boreal coniferous forest environment for polycyclic aromatic hydrocarbon (PAH) compounds was studied using a model ecosystem of acid forest humus (pH = 3.6) and pyrene as the model compound. The matrix was natural humus or humus mixed with oil-polluted soil in the presence and absence of Scots pine (Pinus sylvestris L.) and its mycorrhizal fungus (Paxillus involutus). The rates of pyrene mineralization in the microcosms with humus implants (without pine) were initially insignificant but increased from Day 64 onward to 47 μg kg−1 d−1 and further to 144 μg kg−1 d−1 after Day 105. In the pine-planted humus microcosms the rate of mineralization also increased, reaching 28 μg kg−1 d−1 after Day 105. The 14CO2 emission was already considerable in nonplanted microcosms containing oily soil at Day 21 and the pyrene mineralization continued throughout the study. The pyrene was converted to CO2 at rates of 0.07 and 0.6 μg kg−1 d−1 in the oily-soil implanted microcosms with and without pine, respectively. When the probable assimilation of 14CO2 by the pine and ground vegetation was taken into account the most efficient microcosm mineralized 20% of the 91.2 mg kg−1 pyrene in 180 d. The presence of pine and its mycorrhizal fungus had no statistically significant effect on mineralization yields. The rates of pyrene mineralization observed in this study for forest humus exceeded the total annual deposition rate of PAHs in southern Finland. This indicates that accumulation in forest soil is not to be expected.

Functional morphology of coral shape and passive hydrodynamic self-righting in recentManicina areolata

Thescleractinian Manicina area/ala is a common coral on Caribbean hard and soft substrata and was studied at Lee Stocking Island (Exurna Cays, Bahamas). It is not only found in reefal areas but also on bioclastic sand with seagrasses. The meandroid coralla typically grow to sizes of 2 to 10 cm and are morphologically variable. Growth form can vary from conical with round to oval cross-section to turbinate forms with few meanders and flat oval cross-section. The conical morphotype is usually attached to hard substratum, while the turbinate morphotype tends to live unattached, usually upright, in soft substratum. In infratidal areas, both attached and unattached turbinate forms were found in close vicinity, however, conical attached forms were rare. Habitats with sandy softgrounds, where free-living turbinate morphotypes were common, were influenced by strong tidal currents with concurrent danger of burial or 'disorientation' of the coralla. Therefore, strategies are necessary for the corals to remain in the upright position. Besides a high self-cleaning potential (FABRICIUS 1964), the colony shape itself leads to passive cleaning and self-righting, which is achieved by the flat-turbinate morphology of the corallurn, with a concave side and a flat to slightly convex opposite side, under high current speeds. The concave side, and particularly the median lobes formed by many meandroid coralla, are the critical morphological factors. Particularly the grooves formed inbetween the lobes channel currents in a way that scour underneath the coral and drag produced by the lobes act together to allow passive self-righting.