Oily Contaminants Research Articles

Pre-treatment of remanufacturing cleaning by use of supercritical CO2 in comparison with thermal cleaning

With the development of manufacturing industry, environmental issues have grown increasingly important; remanufacturing has thus been proposed as a means of improving manufacturing sustainability. Cleaning of the used product is one of the most demanding steps of remanufacturing and is usually taken to be the main polluting stage. Traditionally, the cleaning of engines has included thermal cleaning as the pre-treatment, followed by physical cleaning such as abrasive blast cleaning or ultrasonic cleaning. In this paper, a novel and environmentally friendly method of remanufacturing cleaning is proposed, using supercritical carbon dioxide (SCCO2) to remove oily contamination on discarded engine components. A comparison is conducted between this method and thermal cleaning, as pre-treatments, followed by abrasive water jet cleaning and ultrasonic cleaning to remove the pre-treatment residues. The results demonstrate that supercritical fluid cleaning is an ideal alternative to thermal cleaning when remanufacturing aluminium parts with low melting points.

Capillary Model of Gravity Elution of High Viscosity Liquid from a Porous Bed with a Low-Viscosity Liquid

Modeling of the processes of elution from porous systems is essential importance for development of the removing oily contaminations from the soils and intensification of the oil recovery processes. In the paper, capillary model of gravitational elution of high viscosity substances from the porous medium by using low viscosity liquids was derived. This model allowed for the prediction of changes in time of such parameters like: level of bed saturation with oil, relative bed permeability, liquid flow rate, flow resistance, volume of eluted liquid during the process. When modeling, phenomena and the physical properties associated with the analyzed process, such as, for example, the effects of surface tension, fluids viscosity, specific size of the granular bed, initial oil saturation of bed, variable process driving force, and the flow of liquid through the preferential flow paths, were taken into account. This allowed for the more complete imaging of elution process. The model has been verified on the basis of the results of experimental studies. In addition, the discussion on the behavior of the model due to changes in values of various parameters was carried out.

Developing Parameters for Uncommon Exposures

ABSTRACT Common exposure scenarios form the basis for exposure assessments included in human health risk assessments. The quantitative parameters that are used to calculate the receptor's dose associated with these common exposure scenarios are readily available. When humans have uncommon exposures, these often are excluded from the dose calculations because of the lack of parameters or parameters are estimated, which can increase the uncertainty in calculated dose. This study evaluates a third option of performing laboratory experiments to estimate parameters for uncommon exposures. Two exposures, the handling and hand-washing of contaminated work clothes and the drinking of water with sufficient free-phase hydrocarbons to form a visible sheen, were simulated in a laboratory. Parameters were developed for each exposure such that doses could be calculated. Parameters developed include a mass of oily contaminants on skin after washing contaminated clothes and the mass of a visible oily sheen on an aqueous surface. These results demonstrate that developing parameters for uncommon exposure scenarios is a practical alternative to eliminating or estimating exposures and these experiments can be done in compliance with human subject protocols.

Extreme water repellency of nanostructured low-surface-energy non-woven fabrics

We report the extreme water repellent nature of non-woven fabrics of PET (polyethyleneterephthalate) whose fiber surfaces are nanotextured with oxygen plasma and coated with a low-surface-energy nanofilm. The surface effectively suppresses vapor condensation and repels condensed water droplets in addition to exhibiting a high contact angle and a low contact angle hysteresis with a millimetre-sized water drop. We also show that the surface maintains its superhydrophobicity after water-vapor condensation and after oil-wetting due to high-aspect-ratio nanohairs on the fibers. The superior water-repellent ability of the plasma treated non-woven fabric can be exploited in a variety of industrial applications including water harvesting and fuel cell water management even under oily contaminations.

Self-organized TiO 2 nanorod arrays on glass substrate for self-cleaning antireflection coatings

Herein we report the direct fabrication of TiO 2 subwavelength structures with 1-dimensional TiO 2 nanorods on glass substrate through solvothermal process to form self-cleaning antireflection coatings. TiO 2 precursor solutions with different solvent constituents create TiO 2 nanorods with much different morphologies grown on glass substrates. Apiculate TiO 2 nanorods with vertical orientation are grown on the glass substrate which is solvothermally treated in the precursor solution containing ethylene glycol. This glass substrate exhibit the highest transmittance of 70–85% in the range of 520–800 nm and negligible absorption in visible light region (400–800 nm). Furthermore, the TiO 2 nanorod arrays show high hydrophobicity and photocatalytic degradation ability which offer the glass substrate self-cleaning properties for both hydrophilic and oily contaminants.

Effects of oily contamination and decontamination on the flame resistance of thermal protective textiles

AbstractThis paper reports an experimental study wherein flame resistance and limiting oxygen index of protective fabrics were determined before and after contamination with oil and after decontamination. Experimental variables were presence of contamination, laundry treatment, number of contamination/decontamination cycles, and fabric type. Although laundering with pre‐wash products alone was the most effective in removing oil, some product residues may have contributed to the increased flammability of some fabrics. Thus, use of that product was truly effective only if combined with detergent. For two fabrics higher flammability was noted after five contamination/decontamination cycles than after one. Of the three fabrics studied, aramid specimens retained the least oil, and although they had the highest flammability both before and after contamination, it increased the least with contamination. The FR cotton/nylon fabric retained the most oil after decontamination, but had better flame resistance than aramid. Much of the oil remained in the interior of cotton fibres making it difficult to remove but also less accessible for vaporization and combustion. For the aramid/FR viscose, energy from combustion of residual oil activated the FR additive, thereby reducing apparent fabric flammability, but this FR transference effect occurred only up to an optimum quantity of oil. Copyright © 2010 John Wiley & Sons, Ltd.

Effects of sandblasting media and steam cleaning on bond strength of titanium-porcelain

The effects of sandblasting media and steam cleaning treatment after sandblast were examined on tensile bond strength of porcelain to titanium. The use of the commercially available silica-coated alumina particles for sandblast was significantly effective for increasing bond strength than the conventional alumina. It might be due to the increased surface roughness and existence of remaining silica on titanium surface. Additional application of the steam cleaning on titanium surface after sandblasting could make the surface configuration clear in SEM by removing some sandblasted particles loosely embedded in titanium as well as the debris and oily contaminants. The resultant bond strength was significantly improved to reach almost the maximum strength of this porcelain-titanium system regardless of the kind of sandblasting media used, which was confirmed by the observation of the failure mode showing that most of the fracture surface was occupied by cohesive failure in porcelain.

A New Optical Film with Antismudge Function and High Durability

We describe a new surface treatment to obtain optical films for liquid crystal display (LCD) applications. The films consist of a phase-separated layer including a fluorine-containing (FC) compound and a widely used polymer resin for providing a hard coating after surface treatment of the optical film. The major features of the resulting configuration are high durability with a good hardness of above 4H and a surface that allows oily contaminants such as ink and fingerprints to be easily removed by gentle dry wiping, owing to the antismudge function of the FC compound with a low surface energy.

Characterization of the Combustion Process of Flame Resistant Thermal Protective Textiles in the Presence of Oily Contaminants: Effects of Contamination and Decontamination

This paper reports two experimental studies wherein the combustion process of flame resistant (FR) thermal protective textiles is characterized in terms of thermal decomposition and heat release parameters before and after contamination and in terms of heat release parameters after contamination and decontamination. Aramid and FR cotton/nylon decomposed at higher and aramid/FR viscose at lower temperature in the presence of oil. Oil interferes with thermally induced interactions between aramid and FR viscose, altering the thermal decomposition rates and formation of char, and thereby increasing the effectiveness of the flame retardant present in the viscose. It is apparent that oily contaminants present in FR fabrics affect the initiation of the thermal degradation and formation of char. All contaminated FR fabrics showed significantly higher peak heat release rate (PHRR), total heat release (THR) and effective heat of combustion (EHC) compared to uncontaminated ones. Oily specimens laundered with no detergent or prewash product had higher PHRR, THR and EHC compared to other treatments regardless of the fabric type or number of contamination/decontamination cycles. Heat release increased with increased number of contamination/decontamination cycles for most laundry treatments for all FR fabrics. FR cotton/nylon had the highest and aramid had the lowest PHRR and THR whether specimens were uncontaminated, contaminated or decontaminated. In this study heat release from FR fabrics increased with increased oily contamination.

Biotreatment of oily wastewater by rhamnolipids in aerated active sludge system

Oily wastewater generated by various industries creates a major ecological problem throughout the world. The traditional methods for the oily wastewater treatment are inefficient and costly. Surfactants can promote the biodegradation of petroleum hydrocarbons by dispersing oil into aqueous environment. In the present study, we applied rhamnolipid-containing cell-free culture broth to enhance the biodegradation of crude oil and lubricating oil in a conventional aerobically-activated sludge system. At 20 degrees C, rhamnolipids (11.2 mg/L) increased the removal efficiency of crude oil from 17.7% (in the absence of rhamnolipids) to 63%. At 25 degrees C, the removal efficiency of crude oil was over 80% with the presence of rhamnolipids compared with 22.3% in the absence of rhamnolipids. Similarly, rhamnolipid treatment (22.5 mg/L) for 24 h at 20 degrees C significantly increased the removal rate of lubricating oil to 92% compared with 24% in the absence of rhamnolipids. The enhanced removal of hydrocarbons was mainly attributed to the improved solubility and the reduced interfacial tension by rhamnolipids. We conclude that a direct application of the crude rhamnolipid solution from cell culture is effective and economic in removing oily contaminants from wastewater.

Quantity and Distribution of Oily Contaminants Present in Flame-resistant Thermal-protective Textiles

This paper reports an experimental study wherein the quantity and distribution of oily contaminants present in flame-resistant fabrics (FR) after contamination and decontamination was determined using radiotracer analysis and scanning electron microscopy. The experimental variables were fabric type, laundry treatment, and number of contamination/decontamination cycles. Laundry treatments involving a pre-wash product were the most effective in removing oil from all FR fabrics regardless of the number of contamination/ decontamination cycles. Accumulation of oily contaminants was noted after five contamination/ decontamination cycles regardless of the fabric type or laundry treatment. FR cotton/nylon retained the most residual oil for all laundry treatments. No oil remained in the interior of the aramid, viscose, and nylon fibers, but rather remained on the surface so that it was removed easily during decontamination. A significant quantity of oil was located in the interior of the cotton fibers, making it difficult to remove during decontamination.

Investigation of Optimum Liquid for Textile Washing using Artificially Soiled Fabrics

In order to obtain a criterion of liquid cleaning power, a textile washing test was carried out in water and various organic solvents. Cotton and polyester clothes soiled with particulate, oily and water-soluble contaminants were used. The soiled clothes were cleaned in various liquids with stirring and the detergency was evaluated from the change in the surface reflectance of the soiled cloth due to cleaning. The detergency was largely dependent on contaminant, cloth and liquid species, and showed good agreement with common and well-known knowledge about textile washing; the particulate contaminant was difficult to remove in any liquid. In contrast, the oily and water-soluble contaminants were readily removable in the organic solvents and water, respectively. By adding alkali and surfactant to water, the removal of any contaminant considerably increased. In comparison with the stirring, the ultrasonic washing was carried out with the aqueous solutions, but unexpectedly the detergency of most soiled clothes did not increase. For any artificially soiled clothes, a certain relation was successively found between the detergency and the relative dielectric constant.

Study on Metabolic System for Water-Soluble Coolant — Machining Performance and Long-Term Stability of Recycled Coolant

To reduce the management cost and environmental load of water-soluble coolant, authors have been studying on a metabolic system for water-soluble coolant. More than 90% of waste water-soluble coolant is composed of water phase. If the oily additives and contaminants can be isolated from the waste coolant, the amount of waste coolant decreases remarkably because the recycled water can be reutilized as a diluent of renewal coolant. Authors has been developed some types of water recovery methods for the metabolic system. To complete the metabolic system for water-soluble coolant, the coolant diluted with recovered water should have the same machining performance and long-term stability as those of coolant diluted with tap water. In this report, we examined the machining performance and ability change of water-soluble coolant diluted with recycled water under operations encountered in machine tool.

12.1: New Durable, Soil Resistant Optical Film for Front Surface Protection of Flat-Panel Displays

We describe a new protective laminating film for optical display applications. This film, based on UV-curable acrylate chemistry, is prepared by combining abrasion-resistant hardcoat technology with low-surface-energy fluorochemical coatings. The resulting construction shows excellent optical properties, and the fluorochemical surface allows oily contaminants such as inks and fingerprints to be easily removed simply by dry wiping. The film's chemistry and characterization are discussed, along with data on optical properties and environmental stability.

水晶結晶微量天秤とＬａｎｇｍｕｉｒ‐Ｂｌｏｄｇｅｔｔ法により評価した油汚れに対する洗浄力（原標題は英語）

The titled assessment was conducted using a quartz crystal microbalance (QCM) and the Langmuir-Blodgett (LB) method. The gold electrodes of QCM were coated with cellulose acetate, nylon 6 or polyethylene film by spin-coating. Spreading monolayers of long-chain fatty acid as oily contaminants on water were transferred onto spin-coated polymer film. LB films of arachidic acid were ultrasonically cleaned in aqueous solution. Detergency was determined based on the frequency change of the QCM due to cleaning. Detergency was greatest for cellulose acetate, followed by nylon 6 and polyethylene. For all films, detergency increased with the addition of ethanol, surfactant and alkali. Detergency is discussed in relation to contact angle of aqueous solution on polymer film. Liquid introduction between LB film and the polymer surface in the zone of contact appeared to be a significant factor in the removal of LB film from the polymer surface.

Adhesion between Hydrocarbon Particles and Silica Surfaces with Different Degrees of Hydration As Determined by the AFM Colloidal Probe Technique

Adhesion between oily contaminants and soil particles is a key factor controlling oil release during soil decontamination using wet separation processes. Previous research reports showed that hydration of the soil components, mainly silica particles, governs the oil release efficiency. In this work, the adhesion force between polyethylene particles and silica surfaces with different degrees of hydration obtained by thermal treatment and silanation was measured in an aqueous environment using the atomic force microscopy colloidal probe technique. The adhesion force increases significantly with dehydration of the silica surface and the subsequent increase in hydrophobicity. It was found that experimental adhesion forces measured in the polyethylene−water−silica system are in good agreement with the values calculated theoretically using the Lifshitz/van der Waals−Lewis acid/base interaction theory for highly hydrophobic silica substrates. This agreement is less satisfactory for hydrophilic and slightly hydrophobized silica. It is hypothesized that a thin film of water is strongly adsorbed to the silanol groups on the silica surface and protects the silica surface against its “dry contact” with the polyethylene particle during the atomic force microscopy surface force measurements.

Microstructural study on the inhibition of immersion tin coating formation by the substrate surface contamination

The formation of an immersion tin coating from a hydrochloric acid based bath on the inner surface of clean and contaminated copper tubes was studied by scanning electron microscopy and transmission electron microscopy in order to explore the role of substrate surface contamination in the immersion tin coating build-up. The mechanism of inhibition by a drawing lubricant layer was the major attribute under exploration. The substrate surface contamination was found to influence both the coating nucleation and growth processes and the overall appearance of the immersion tin coating. A discontinuous, thin, nanocrystalline and irregular tin coating forms on a contaminated copper substrate instead of a continuous, crystalline, regular tin coating of a reasonable thickness, which builds up on a clean copper surface. However, the nucleation mechanism of immersion tin deposit is equivalent on clean and contaminated substrate surfaces. The oily contamination layer is, thus, only suggested to block the accessibility of aqueous plating solution onto the substrate surface, thereby hindering the coating nucleation at the areas of poor cleaning. Besides, no grain growth was encountered in tin coatings deposited on the poorly cleaned copper.

Detachment behavior of Langmuir–Blodgett films of arachidic acid from a gold surface studied by the quartz crystal microbalance method

The detachment process of an oily contaminant from a gold surface was investigated using a model system constructed by the application of the quartz crystal microbalance (QCM) method and the Langmuir–Blodgett (LB) technique. Long-chain fatty acid, arachidic acid, was used as a model oily contaminant. The solid-condensed monolayers of arachidic acid on water were transferred onto the QCM by the vertical dipping method. The frequency change of the QCM at each immersion–withdrawal cycle indicated that the monolayers were successfully deposited on the gold surface of the QCM as Y-type multilayers. The QCM having the LB films of arachidic acid was cleaned in aqueous solutions containing sodium chloride, sodium hydroxide, surfactants and/or ethanol by applying ultrasonic waves. Surfactants used were sodium dodecyl sulfate (SDS) and n-octyl β- d-glucopyranoside (OGP). The detachment efficiency of the LB films from the gold surface was evaluated from the frequency change of the QCM due to the detachment. The efficiency increased with time and showed saturation at 20–30 min. The detachment was found to increase with increasing concentrations of sodium hydroxide, SDS, OGP, and ethanol. At the critical micelle concentrations of SDS and OGP or at ca. 50 vol.% of ethanol, the LB films were perfectly removed from the gold surface. The detachment efficiencies obtained in all systems were correlated with the free energy change due to liquid penetration between the LB films and the gold surface, which was calculated from the experimentally determined contact angles and surface free energies. The saponification of arrachidic acid by alkali as well as the liquid penetration was found to contribute to the detachment of the LB films. The exposure of the 172 nm ultraviolet excimer light prior to the ultrasonic washing was effective for the removal of the LB films.

Comparison between supercritical carbon dioxide extraction and aqueous surfactant washing of an oily machining waste

Mathematical models are developed to compare aqueous surfactant washing to supercritical carbon dioxide (SCCO 2) extraction. These two cleaning processes are potentially competitive technologies which can be used to remove oily contaminants from a solid waste. In both processes, the cleaning efficiency for a batch of waste is evaluated by quantifying the residual oil content in the treated sample. A mass transfer model is used to simulate a semi-continuous washing process, and the experimental data, obtained in a batch operation, are used to estimate the equilibrium parameters in the model. For SCCO 2 extraction, a linear desorption model is used to describe the supercritical desorption of oil from the solid phase into the CO 2 phase and the simulated results agreed very well with the experimental data. The oil removal in aqueous surfactant washing is viewed to be controlled primarily by the diffusional transport of oil from the interiors of the waste elements to the surface, thus, it can be significantly affected by the size of the particles. A pre-cleaning pulverization is then recommended to improve the cleaning efficiency without increasing any other operation costs. In SCCO 2 extraction, the desorption of oil from the solid waste is the controlling step and consequently, the solvent flow rate has no influence on oil removal. Our theoretical studies show that the difference between the cleaning efficiencies of these two technologies is not significant, with the oil concentration in the washing products approximately 5% lower than that in the extraction products.

Separation of oil contaminants by surfactant-aided foam fractionation

The separation of oily contaminants out of aqueous/non-aqueous phases using foam fractionation with a surfactant was investigated. In the separation of the light oil (hexadecane), the eluted amount of oil and the o/w (oil/water) ratio increased with the weight percentage of SDS (sodium dodecyl sulfate); and the ratio actually remained the same above the CMC (critical micelle concentration) point (0.23 wt% of SDS). Most of the oil was eluted even at 49:1 initial o/w ratio with the surfactant. For the heavy oil (carbon tetrachloride), the eluted o/w ratio and the oil recovery had maxima at 0.05 and 0.1 wt% of SDS solution, respectively, even though the overall recovery of 20–30 % was much lower than that of 80–100 % in the light oil. It was speculated that emulsion formation might affect oil entrapment in the foams. Higher gas flow rates, in general, increased the oil recovery, but did not increase the o/w ratio in the effluents.