Contribution of different physical forces to the disjoining pressure of a thin water film being pressed by an oil droplet

With an objective to understand the nature of forces which contribute to the disjoining pressure of a thin water film on a steel substrate being pressed by an oil droplet, two independent sets of experiments were done. (i) A spherical silica probe approaches the three substrates; mica, PTFE and steel, in a 10 mM electrolyte solution at two different pHs (3 and 10). (ii) The silica probe with and without a smeared oil film approaches the same three substrates in water (pH = 6). The surface potential of the oil film/water was measured using a dynamic light scattering experiment. Assuming the capacity of a substrate for ion exchange the total interaction force for each experiment was estimated to include the Derjaguin-Landau-Verwey-Overbeek (DLVO) force, hydration repulsion, hydrophobic attraction and oil-capillary attraction. The best fit of these estimates to the force-displacement characteristics obtained from the two sets of experiment gives the appropriate surface potentials of the substrates. The procedure allows an assessment of the relevance of a specific physical interaction to an experimental configuration. Two of the principal observations of this work are: (i) The presence of a surface at constant charge, as in the presence of an oil film on the probe, significantly enhances the counterion density over what is achieved when both the surfaces allow ion exchange. This raises the corresponding repulsion barrier greatly. (ii) When the substrate surface is wettable by oil, oil-capillary attraction contributes substantially to the total interaction. If it is not wettable the oil film is deformed and squeezed out. (C) 2010 Elsevier Inc. All rights reserved.

Bioremediation of diesel oil contaminated soil and water

Diesel spills contaminate aquatic and terrestrial environments. To prevent the environmental and health risks, the remediation needs to be advanced. Bioremediation, i.e., degradation by microbes, is one of the suitable methods for cleaning diesel contamination. In monitored natural attenuation technique are natural processes in situ combined, including bioremediation, volatilization, sorption, dilution and dispersion. Soil bacteria are capable of adapting to degrade environmental pollutants, but in addition, some soil types may have indigenous bacteria that are naturally suitable for degradation. The objectives for this work were (1) to find a feasible and economical technique to remediate oil spilled into Baltic Sea water and (2) to bioremediate soil contaminated by diesel oil. Moreover, the aim was (3) to study the potential for natural attenuation and the indigenous bacteria in soil, and possible adaptation to degrade diesel hydrocarbons. In the aquatic environment, the study concentrated on diesel oil sorption to cotton grass fiber, a natural by-product of peat harvesting. The impact of diesel pollution was followed in bacteria, phytoplankton and mussels. In a terrestrial environment, the focus was to compare the methods of enhanced biodegradation (biostimulation and bioaugmentation), and to study natural attenuation of oil hydrocarbons in different soil types and the effect that a history of previous contamination may have on the bioremediation potential. (1) In the aquatic environment, rapid removal of diesel oil was significant for survival of tested species and thereby diversity maintained. Cotton grass not only absorbed the diesel but also benefited the bacterial growth by providing a large colonizable surface area and hence oil-microbe contact area. Therefore use of this method would enhance bioremediation of diesel spills. (2) Biostimulation enhances bioremediation, and (3) indigenous diesel-degrading bacteria are present in boreal environments, so microbial inocula are not always needed. In the terrestrial environment experiments, the combination of aeration and addition of slowly released nitrogen advanced the oil hydrocarbon degradation. Previous contamination of soil gives the bacterial community the potential for rapid adaptation and efficient degradation of the same type of contaminant. When the freshly contaminated site needs addition of diesel degraders, previously contaminated and remediated soil could be used as a bacterial inoculum. Another choice of inoculum could be conifer forest soil, which provides a plentiful population of degraders, and based on the present results, could be considered as a safe non-polluted inoculum. According to the findings in this thesis, bioremediation (microbial degradation) and monitored natural attenuation (microbial, physical and chemical degradation) are both suitable techniques for remediation of diesel-contaminated sites in Finland.

On the High Frequency Dielectric Behavior of Castor Oil

The low frequency dielectric behavior of castor oil (a vegetable oil) has been analyzed quite exhaustively in the context of its application as impregnant in capacitors. For the sake of completeness and in order to understand the relaxation phenomena in this liquid dielectric, this high frequency dielectric study was undertaken. In order to compare its properties with a liquid dielectric used in similar application and whose high frequency behavior has been quite well analyzed, Arochlor 1476 was studied. It is observed that both liquids have distributed relaxation times. The distribution parameters together with the two distinct relaxation times have been calculated by measuring the average relaxation time. It has been found that the distinct relaxation times thus calculated represent the dielectric behavior quite satisfactorily. The average dipole moments, dipole radii and thermal activation energies for dipole relaxation have also been evaluated.

Effect of surfactant dispersed in oil on interaction force between an oil film and a steel substrate in water

The oil phase, in an oil-in-water emulsion on a steel substrate, is strongly repelled by the substrate. The oil in this situation does not wet the steel and steel/steel friction is high. In this work we disperse anionic surfactants in an oil film and study the effect of this dispersion on the force of interaction between a silica colloid probe (AFM) carrying the oil film and a steel substrate in water. It is observed that when the surfactant is oil insoluble and the interaction time is short the strong entropic repulsion (without the surfactant) is replaced by a strong attraction. The steel on steel sliding friction in this case is low compared to that what is achieved when the surfactant is soluble in oil. The rationale underlying these interactions is explored here. (C) 2011 Elsevier B.V. All rights reserved.

A study of partial discharge characteristics in oil impregnated pressboard insulation

An attempt has been made to study the effect of time and test procedure on the behaviour of partial discharge (PD) pulses causing failure of oil-pressboard system under power frequency voltages using circular disc shaped samples and uniform field electrodes. Weibull statistics have been used to handle the large amount of PD data. The PD phenomena has been found to be stress and time dependent. On the basis of stress level, three different regions are identified and in one of the regions, the rate of deterioration of the sample is at a maximum. The work presents some interesting features of Weibull parameters as related to the condition of insulation studied in addition to its usual PD characteristics

Spatial distribution of oil in groundnut and sunflower seeds by nuclear magnetic resonance imaging

The nuclear magnetic resonance imaging technique has been used to obtain images of different transverse and vertical sections in groundnut and sunflower seeds. Separate images have been obtained for oil and water components in the seeds. The spatial distribution of oil and water inside the seed has been obtained from the detailed analysis of the images. In the immature groundnut seeds obtained commercially, complementary oil and water distributions have been observed. Attempts have been made to explain these results.

Purification and partial characterization of acyl carrier proteins from developing oil seeds of pisa (Actinodaphne hookeri) and ground nut (Arachis hypogaea)

Acyl carrier proteins (ACP) were purified to homogeneity in the active form from developing seeds of pisa (Actinodaphne hookeri) which synthesizes exclusively trilaurin and from ground nut (Arachis hypogaea) which synthesizes triacylglycerols containing long chain fatty acids. Two major isoforms of ACPs were purified from developing pisa seeds using DEAE-cellulose, Superose-6 FPLC and C-4 reversed phase HPLC chromatographic methods. In contrast, only a single form of ACP was present in ground nut seeds which was purified by anion-exchange and activated thiol-Sepharose 4B affinity chromatography. The two isoforms of ACPs from pisa showed nearly the same specific activity of 6,706 and 7,175 pmol per min per mg protein while ground nut ACP showed a specific activity of 3,893 pmol per min per mg protein when assayed using E. coli acyl-ACP synthetase and [1-C-14]palmitic acid. When compared with E. coli ACP, the purified ACPs from both the seeds showed considerable difference in their mobility in native PAGE, but showed similar mobility in SDS-PAGE under reducing conditions. In the absence of reducing agents formation of dimers was quite prominent. The ACPs from both the seed sources were acid- and heat-stable. The major isoform of pisa seed ACP and the ground nut ACP contain 91 amino acids with M(r) 11,616 and 1,228 respectively. However, there is significant variation in their amino acid composition. A comparision of the amino acid sequence in the N-terminal region of pisa and ground nut seed ACPs showed considerable homology between themselves and with other plant ACPs but not with E. coli ACP.

GC-MS study of Artabotrys odoratissimus fatty oil (leaves)

GC-MS study of two fatty oil fractions from Artabotrys odoratissimus (leaves) indicated the presence of fifteen compounds namely, nonanoic acid; methyl phenyl propanoate; decanoic acid; diethyl phthalate; dibutyl phthalate; 2 - amino-3-ethyl biphenyl; 5-methyl-9-phenylnonan-3-ol; hexadeca-2,7,11-triene; 2,6-dimethyl-1-phenylhepta-1-one; 2,5-dimethyltetradecahydrophenenthrene; 1-phenylundecane; 1-isopropyl-4,6-dimethyl naphthalene; 5-(2-butyl phenyl)pent-3-en-2-ol; 1-phenyideca-1-one and 1-phenylundecan-1-one. Some of the compounds are rare occurring and biologically active.

Lubricity of an oil in water emulsion in metal cutting: The effect of hydrophilic/lypophilic balance of emulsifiers

A steel disc is cut using a single point tool. The coefficient of friction of the nascent cut surface is measured by a spherical steel pin situated in close proximity of the point of cutting. The tool, disc and the friction pin are immersed in an oil in water emulsion bath during the experiment. The purpose of the experiments conducted here is to record the effect of hydrophilic/lypophilic balance (HLB) of the emulsifier on the lubricity experienced in the cutting operation. The more lypophilic emulsifiers were found to give greater lubricity than what is recorded when the emulsifier is more hydrophilic. XPS and FTIR spectroscopy are used to explore the tribofilm generated on the nascent cut surface to indicate a possible rationale for the effect. (C) 2011 Elsevier B.V. All rights reserved.