Dissertations / Theses on the topic 'Surfactants; Surface active agents'

Thesis (M.S. in biological and agricultural engineering)--Washington State University, May 2010.<br>Title from PDF title page (viewed on June 23, 2010). "Department of Biological Systems Engineering." Includes bibliographical references (p. 16-22).

Thesis (M.Ch.E.)--University of Delaware, 2008.<br>Principal faculty advisors: Norman J. Wagner, Dept. of Chemical Engineering; and Eric W. Kaler, College of Engineering. Includes bibliographical references.

Methods for the analysis of surfactants and proteins by Capillary Electrophoresis (CE) were investigated. Several modifications of the system to achieve detection and separation of these analytes were examined. These modifications included buffer additives, sample additives and surface treatment and modification of the fused silica capillary. For the analysis of anionic surfactants, the addition of an anionic IN absorbing compound to the buffer was investigated to achieve indirect detection of the non-absorbing surfactants. The effect on detection sensitivity and separation efficiency of the absorbing ion was examined. These parameters were affected by differences in the electrophoretic mobilities of the analytes in comparison to the absorbing ion. The use of organic modifiers was also investigated to minimize micelle formation of the surfactants which leads to zone spreading. For the analysis of serum and urine proteins, the use of high pH buffers was investigated to minimize solute/capillary surface interactions and achieve separation. At high pH's the proteins are negatively charged; therefore, they should be repelled by the negatively charged fused silica surface. To improve reproducibility of migration times of the proteins the addition of polyvinyl alcohol to the sample was also investigated. The polyvinyl alcohol improved reproducibility by reversibly covering the active sites on the capillary surface to minimize protein interactions. Migration time reproducibility was also improved by optimizing the capillary cleaning procedure. Lastly, the addition of methyl cellulose to the buffer to work as a dynamic molecular sieving medium was investigated to improve resolution. Analyte/ capillary surface interactions are a major limitation in CE especially for the analyses of proteins. The use of coated capillaries to eliminate these interactions has been widely investigated. However, reproducibility and degree of surface deactivation with these coating can be poor. In this work hydrothennal treatment of the fused silica capillary surface prior to deactivation was examined. Hydrothennal treatment was used to produce a homogenous surface prior to coating which leads to the production of more highly deactivated, reproducible columns. The effects of the treatment were studied by coating the surface with a silane and examining the influence of the coating on electroosmotic flow and analyte adsorption.<br>Ph. D.

Thesis (MSc)--Stellenbosch University, 2002.<br>ENGLISH ABSTRACT: The surfmers sodium l l-rnethacryloyloxy undecanyl-I sulfate (MET) and sodium 11- crotonoyloxy undecanyl-I sulfate (CRO) were synthesized and purified. Both contain a sulfonate and polymerizable double bond connected by a hydrocarbon chain. Sodium 4-[ 11- (3-carboxypropionoyloxy)-undecyloxy] benzenesulfonate (PSA-MA) could not be synthesized successfully. MET and CRO were characterized by means of nuclear magnetic resonance spectroscopy (NMR), elemental analysis (EA), thermal gravimetric analysis (TGA), determination of the critical micelle concentration (CMC), differential scanning calorimetry (DSC), and microscopy. MET and CRO displayed a liquid crystalline behavior. MET and CRO were used in combination with poly(diallyl dimethyl ammonium chloride) to form polyelectrolyte-surfactant complexes by common precipitation in water. These complexes were redissolved in methanol and cast in films. The cast films were investigated by wide angle X-ray scattering (WAXS) and small angle X-ray scattering (SAXS) with regard to ordered mesomorphous phases. Due to the destabilization of the lyotropic phase, little order were observed in the complexes. MET was co-polymerized with styrene and methyl methacrylate, in different proportions, by means of free radical polymerization. The co-polymers were characterized by NMR and infrared spectroscopy (Ik) and analyzed by DSC, TGA and gel permeation chromatography (GPC). All analytical techniques showed that the co-polymers were synthesized successfully. TEM indicated a fine, lamellar micro-structure.<br>AFRIKAANSE OPSOMMING: Die polimeriseerbare sepe, natrium-ll-metakrieloloksi-undekaniel-l sulfaat (MET) en natrium-ll-krotonieloksi-undekaniel-l-sulfaat (CRO) is berei en gesuiwer. Beide bevat 'n sulfonaat en 'n polimeriseerbare dubbelbinding wat deur 'n koolwaterstofketting verbind word. Natrium-4-[11-(3-karboksipropionieloksi)-undekieloksi]-benseensulfaat (PSA-MA) kon nie suksesvol berei word me. MET en CRO is deur middel van kernmagnetieseresonansspektroskopie (KMR), elementele-analise (EA), termiesegravimetriese analise (TOA), kritiese miselkonsentrasie (CMC), differensieelskandeerkalorornetrie (DSC) en mikroskopie gekarakteriseer. Beide MET en CRO het 'n vloei-kristalgedrag getoon. MET en CRO is met poli(diallieldimetielammoniumchloried) gereageer om polyelektrolietseepkompleks te vorm deur presipitasie uit water. Die komplekse is in metanol opgelos en films daarvan gemaak. Die films is deur wyehoek X-straal diffraksie (WAXS) en kleinhoek X-straaldiffraksie (SAXS) ondersoek om geordende mesomorfiese fases te ondersoek. As gevolg van destabilisasie van die liotropiese fase is min orde in die komplekse gevind. MET is met stireen en metielmetakrilaat deur middel van vryeradikaalpolymerisasie gekopolimeriseer. Die kopolimere is deur middel van KMR- en infrarooispektroskopie (IR), DSC, TOA en gelpermeasiechromotagrafie (OPC) ondersoek. Al hierdie analitiese metodes het die suksesvolle sintese van die kopolimere bewys. Transmissie-elektronmikroskopie het die teenwoordigheid van 'n fyn, laminere mikro-struktuur bewys.

A unique penetration instrument has been developed to evaluate the role of surfactants in kraft pulping process. This instrument can screen surfactants which can improve the wood impregnation more effectively and much faster than pilot-plant experiment. The role of surfactants in wood penetration has been explored. Surfactants can improve wood impregnation by dispersing the extractives in the wood structure and optimizing the interfacial properties between wood surface and kraft liquor. The addition of two blends of anionic and nonionic surfactants into kraft pulping process results in a significant reduction of the screen rejects and an increase of screened yield at the same delignification rate.<br>Six wood species were tested in this study including both non-resinous and resinous wood species. Both sapwood and heartwood of these species were tested. Surfactants were found to have no improvement on sapwood, but a significant improvement on heartwood. The critical micelle concentrations (CMC) of surfactants in kraft liquor were determined. The best dosages of surfactants based on CMC were also determined in this study.

Thesis (Ph.D.)--University of Delaware, 2008.<br>Principal faculty advisors: Eric W. Kaler, College of Engineering; and Abraham M. Lenhoff, Dept. of Chemical Engineering. Includes bibliographical references.

Thesis (Ph.D.)--University of Delaware, 2006.<br>Principal faculty advisors: Eric W. Kaler, College of Engineering; and Abraham M. Lenhoff, Dept. of Chemical Engineering. Includes bibliographical references.

The objective of this investigation was to observe and evaluate the effects of surfactants on the biodegradation of toluene in the subsurface. Soil microcosms containing gasoline were used to simulate conditions of an aquifer contaminated with hydrocarbons. The surfactants were the nonionics, Surfonic N-40 and N-95. Three volumes of gasoline, 0.005, 0.05, and 0.1 mL, were injected into separate microcosms in order to observe changes in toluene concentration in both adsorbed component conditions and free-phase, interstitial gasoline conditions. The data presented are the results from the microcosms containing 0.005 mL gasoline. -Dissolved toluene was only partially biodegraded in the microcosms containing free-phase hydrocarbons. The lack of complete biodegradation was believed to be due to substrate toxicity.<br>Master of Science

Thesis (Ph. D.)--University of Florida, 2000.<br>Title from first page of PDF file. Document formatted into pages; contains xvii, 174 p.; also contains graphics. Vita. Includes bibliographical references (p. 165-173).

Thesis (Ph. D.)--Ohio State University, 2005.<br>Title from first page of PDF file. Document formatted into pages; contains xvi, 161 p.; also includes graphics (some col.). Includes bibliographical references (p. 155-161). Available online via OhioLINK's ETD Center

The adsorbed layer morphology of a series of surfactants under different conditions has been examined primarily using atomic force microscopy (AFM). The morphologies of single and double chained quaternary ammonium surfactants adsorbed to mica have been characterised using AFM at concentrations below the cmc. Mixing these different types of surfactants systematically allowed a detailed examination of the change in adsorbed film curvature from the least curved bilayers through to most curved globules. From this study a novel mesh structure was discovered at curvatures intermediate to bilayers and rods. A mesh was again observed in studies examining the morphology change of adsorbed nonionic surfactant films on silica with variation in temperature. Other surfactant mixtures were also examined including grafting non-adsorbing nonionic surfactants and diblock copolymers into quaternary ammonium surfactant films of different morphologies.

Surfactant assisted solution exfoliation of expanded graphite by means of sonication was carried out in an attempt to produce non-covalent charge functionality on the surface of graphene for the directed self assembly of graphene films on patterned substrates via electrostatic interactions. This thesis includes the results of experimental research associated with: 1) quantifying the effectiveness of various di-functionalized dithienothiophene surfactant small molecules, 2) further understanding the surface affinity and interaction mechanism between these surfactant molecules and the surface of expanded graphite and graphene and 3) experimentally testing the feasibility of the directed self-assembly of graphene films by means of charge functionalization of graphene by the surfactant molecules adsorbed onto the surface of exfoliated graphene.

In title 12, 22, 11 are in subscript.<br>Thesis (PhD)--Stellenbosch University, 2002.<br>ENGLISH ABSTRACT: The aim of this study was to test a synthetic protein-free surfactant preparation, LPM-l, with the same chemical composition as commercially available Exosurf (Glaxo Wellcome), but containing in addition, a sugar, trehalose (TRE). Towards this end, a study was designed to firstly test the hypothesis that the true difference in acute physiological effects between a mixture of oppe, tyloxapol, hexadecanol and trehalose (LPM-l), and Exosurf, (Oppe, tyloxapol and hexadecanol) is zero, in a surfactantdeficient animal model. A second study addressed the physiological effects of oppe, hexadecanol, tyloxapol and trehalose (LPM-l) compared to treatment with trehalose (TRE) or saline, in order to determine (1) the contribution of TRE to the mixture of oppe, hexadecanol and tyloxapol, and (2) to assess the effect of the LPM-l surfactant replacement on the epithelial lining fluid composition by means of analysing bronchoalveolar lavage fluid. Thirdly, the effects of TRE and / or calcium were studied on the surface properties of oppe suspensions, by in vitro analysis using the ring detachment method of Du Nouy The in vivo research comprised of two studies, performed in randomised controlled fashion. In the first study, 24 New Zealand White adult rabbits were randomised into 4 groups, while in the second study, 15 animals were randomised into 3 groups. In the first in vivo study, three synthetic surfactants, LPM-l, Exosurf and LPM-2, and a saline group were tested. LPM-l is a new formulation that consists ofa mixture of Df'PC, TRE, hexadecanol and tyloxapol. LPM-2 is a formulation with a composition equivalent to that of commercially available Exosurf, prepared on site. In both studies animals were subjected to repeated lavage with large volumes of warm saline (25 ml/kg) in order to establish surfactant deficiency and acute lung injury. Five minutes after the last lavage, vehicle, i.e. surfactants LPM-l, Exosurf, or LPM-2, or saline, in the first in vivo study, and LPM-l, TRE or saline in the second in vivo study, was instilled, and the course of the animals followed over the next 3 hours. Ventilator settings were standardized before and after lavage. The effects of surfactant treatment on gas exchange (arterial Pa02, oxygenation index (Ol), arterial-alveolar oxygen (a/A) ratio), percentage calculated shunt, and total dynamic respiratory compliance (CRSdyn), and histopathological changes were compared with changes in saline treated controls. Arterial blood gases in 100% oxygen and CRSdynwere measured before and after lavage, at 15 minute intervals for the first 30 min, then at 60, 90, 120, and 180 min after vehicle instillation. Oxygenation improved to a similar extent after LPM-l and Exosurf instillation, surpassing that of LPM-2 or saline. Overall, intratracheal instillation of both Exosurf and LPM-l, rapidly improved the gas exchange and reduced the intrapulmonary shunt, but did not restore the lung to its pre-lavage condition. From the 2nd in vivo study it was evident that trehalose-only, was inefficient as a lung surfactant, failing to improve oxygenation indices or the calculated percentage shunt, or influencing respiratory compliance. The addition of the sugar, trehalose (TRE), to the on-site 'Exosurf mixture (LPM-2) brought the activity of the resultant LPM-l to the same level as that of commercial Exosurf, but failed to raise the activity above that of Exosurf. These physiological improvements were sustained for up to 3 hours. Saline-treated animals had no improvement in gas exchange despite management with variable PIP (to maintain a tidal volume of -1 0 ml / kg) and constant PEEP of 5 cm H20. In-vitro results, obtained by the Ou Nouy tensiometer, showed higher mean ordinate surface tension values for the OPPC-only and DPPC + TRE mixtures, and the slopes of their respective graphs smaller in magnitude than those of the other formulations, suggesting that these formulations had less surface tension-lowering capability than the other surfactants. At 20°C (20 mg / ml DPPC-surfactants) the mean ordinate values of OPPC and OPPC + TRE, 70.13 and 69.47 dyne / cm, respectively, were not significantly different from each other. The mean ordinate values of LPM-l and the formulation containing OPPC + TRE + tyloxapol + CaCh were lower, but similar, as were the values of LPM-2 (on-site Exosurf) and LPM-2 + CaCho Thus, three internally homogeneous subgroups could be identified which differed significantly, namely: DPPC and DPPC + TRE, LPM-2 and LPM-2 + CaCh, and DPPC + TRE + tyloxapol + CaCh and LPM-l. Similar conclusions apply to the ordinate values of the surfactants at 37°C, and to the mean slope values at 20°C, with the exception that the subgroups, LPM-2 and LPM-2 + CaCh, and LPM-l and OPPC + TRE + tyloxapol + CaCh are not so clearly separated. A similar analysis of mean slope values was performed. Here too a significant difference between substances was found, OPPC alone or in combination with TRE, again being significantly different from the other surfactants. The most prominent light microscopy findings of the lungs of animals included general lymphatic dilatation, congestion and lung polymorphonuclear infiltration, with no difference between study groups. Hyaline membranes were present in all surfactant groups, but significantly more so in the saline treated group. In the first in vivo study, the presence of neutrophils in the lung interstitiwn as well as alveoli, was a common finding in all of the study groups towards the end of the study protocol. A significant increase in the BAL-fluid neutrophil count occurred in all animals, concurrent with a significant decrease in the BAL macrophage count. No significant change occurred in the peripheral neutrophil count during the 3-hour study, suggesting recruitment of neutrophils from storage pools. Treatment with synthetic surfactant (LPM -1) did not have a significant effect on modifying the inflammatory response, since there was no significant difference in the BAL-derived cell counts between the LPM-1 and -saline groups. Epithelial damage was a consistent finding in all groups. The damage was more evident by electron microscopy examination and included hydropic changes, most readily observed in the mitochondria. The airspaces of study subjects showed the presence of oedema fluid. This luminal oedema appeared to be more prominent in the control group and LPM-2 (on site 'Exosurf') group. Organellar debris, probably originating from lysis of epithelial cells, was present, despite treatment with synthetic surfactant. The electron microscopical appearance of the epithelial-lined substance ("hyaline membranes") in the present study showed a marked variability within groups as well as within the same case. The majority of cases showed a mix of membrane types with both granular and fibrillar materials present within the same membrane. In some cases there were layering of the membranes into distinct bands. The instillation of LPM-l resulted in the formation of a slightly different type of epithelial lining fluid after lavage, when compared to the prelavage composition. The most pronounced changes occurred within the fatty acids, whilst the phosphatidylcholine values remained unchanged. Palmitic acid concentrations (C16:0) increased significantly, suggesting enrichment of the epithelial lining fluid after instillation of LPM-l. This increase in C16:0 was concurrent with significant decreases in the percentage C16:1, C18:0, and C18:2. In contrast to previous studies, we describe higher levels for phosphatidyldimethylethanolarnine (PEA). An explanation may be that the lipid identified as PEA, was in fact partly phosphatidylglycerol (PG)-a lipid whose accurate identification was precluded for technical reasons. After surfactant instillation, the PC/SM ratio, a reflection of the lecithin / sphingomyelin (LIS), decreased significantly in the TRE-group between the first and final lavage, but remained statistically unchanged in the animals treated with LPM-l or saline. The change in ratio was mainly accounted for by a decrease in BAL-fluid PC content together with a rise in SM content. A poor correlation existed between the BAL-derived PC/SM ratio and indices reflecting oxygenation status (a/A ratio, Ol), as well as the CRSdynat the time of the final lavage. In conclusion, the primary hypothesis was accepted, LPM-l performed similarly to Exosurf in vivo, improving oxygenation, but not CRSdyn.None was clearly superior to the other. Some questions remain. The reason why LPM-l (LPM-2 + TRE) did not behave in a superior manner, in vivo, to Exosurf, is partly unclear. This finding was somewhat surprising since the chemical composition of Exosurf and LPM-2 did not differ, and the addition of TRE to LPM-2 (on-site Exosurf), did improve the in vivo activity of the resultant LPM-l, above that of LPM-2. A possible explanation for observed differences in performance include methodological issues, i.e. the preparation of the on-site formulations, especially that of LPM-2 (on-site Exosurf), may differ from the way in which true commercial Exosurf is prepared.<br>AFRIKAANSE OPSOMMING: Die doel van die studie was om 'n sintetiese proteïn vrye surfaktant te ontwikkel en die produk te vergelyk met 'n kunsmatige surfaktant reeds in kliniese gebruik. Die bekende uit die literatuur en die onbekende van die produk wat evalueer sou word, lei op tot die samestelling van die nul hipotese van die PhD naamlik dat geen verskil in longfunksie sou gewys word tussen die toetsproduk en reeds gebruikte kommersiële surfaktant nie. Die hipotese was dat 'n suiker (trehalose), in kombinasie met Dipalmitoiel fosfatidielcholine (DPPC), gaswisseling en longfunksies sal verbeter vir 'n long met 'n lae surfaktant konsentrasie. Vir die studie is jong volwasse wit New Zealand konyne gebruik en is hulle met 'n gestandaardiseerde en menslike manier gebruik in eksperimentele werk. Die diere is onder intraveneuse narkose geplaas en verskillende kardiovaskulêre en pulmonologiese aspekte is gemeet. Die long surfaktant is uitgewas deur middel van fisiologiese soutoplossing wat tot liggaam temperatuur verhit is en daarna is die diere prospektief gerandomiseer tot eksperimentele groepe. Met vooraf bepaalde tydsintervalle is die fisiologiese metings herhaal en was die metings toegespits daarop om longmeganiese funksie en gasoordrag vermoë te evalueer. Lig mikroskopiese en elektron mikroskopiese studies is ook op die longe gedoen en verder is brongoalveolêre vloeistof ook ontleed. Die groepe met ondersoek was: I. oppe, heksadekanol, tyloxapol en trehalose (LPM-I). 2. oppe, heksadekanol, tyloxapol (LPM-2 :. LPM-I sonder trehalose). Hierdie is 'n proteïnvrye surfaktant plaaslik berei ( dieselfde samestelling as Exosurf). 3. Exosurf®. (Kommersiële preperaat reeds in gebruik). Hierdie is 'n proteïnvrye sintetiese surfaktant. 4. Trehalose, 'n non-reduserende disakklaried van glukose. Addisioneel is daar ook in vitro studies gedoen waann die oppervlakte spanmngs aktiwiteite van die verskillende surfaktant oplossings vergelyk is. Die statistiese analise is gedoen in samewerking met Prof. J. Maritz wat 'n unieke metode ontwikkel en gepubliseer het om herhalende veranderlikes op 'n statisties verantwoordbare manier te ontleed. In die eerste van die studies, is LPM-I, Exosurf®, fisiologiese soutoplossing en 'n plaaslik bereide "Exosurf" (LPM-2), met 'n chemiese samestelling identies aan dié van kommersiële Exosurf®, evalueer. In 'n tweede studie is die fisologiese effekte van LPM-I vergelyk met trehalose of fisiologiese soutoplossing om die volgende te ondersoek: 1) Die bydrae van trehalose tot 'n mengsel van oppe, heksadekanol en tyloxapol (LPM-2). 2) Die gevolg van LPM-l surfaktant toediening op die konyn se brongo-alveolêre vloeistof samestelling. 'n Derde, in vitro studie, het die oppervlaktespannings-effekte van trehalose en of kalsiumbyvoegings tot DPPC-oplossings gemeet deur middel van die ring metode van Du Nouy, In die eerste in vivo studie verbeter oksigenasie en persentasie longaftakking tot dieselfde mate na LPM-l en Exosurf® toediening en word die hipotese van die proefskrif bevestig. In die breë gesien, is die tydsprofiele van LPM-l en Exosurf® ten opsigte van oksigenasie en persentasie longaftakking statisties betekenisvol beter en van 'n sneller aard, as die tydsprofiele van dieselfde indekse na die toediening van fisiologiese soutoplossing of LPM-2. Die tydsprofiel van dinamiese longvervormbaarheid, na die toediening van LPM-I of Exosurf®, is dieselfde, maar betekenisvol beter as die vervormbaarheid na toediening van LPM-2 of fisiologiese soutoplossing. Alhoewel die oksigenasie indekse in die geval van LPM-l en Exosurf® betekenisvol verbeter oor die studietydperk, vind volkome herstel tot die basislynwaardes (voor spoeling) nie plaas nie. Bykomend, geen van die surfaktante het na toediening enige noemenswaardige verbetering in longvervormbaarheid tot gevolg gehad nie. Die rede vir die swakker vertoning van LPM-2 en Exosurf is onbekend en sal in opvolg studie ondersoek word. In die tweede in vivo studie is dit duidelik dat trehalose op sy eie, 'n oneffektiewe surfaktant is aangesien die preperaat na toediening geen verbetering teweegbring ten opsigte van oksigenasie indekse, persentasie longaftakking, of long-dinamiese vervormbaarheid nie. Die toevoeging van trehalose tot LPM-2, om LPM-l te lewer, neem wel die aktiwiteit van LPM-l tot dieselfde in vivo vlak as dié van kommersiële Exosurf®, maar slaag nie daarim om 'n hoër fisiologiese in vivo aktiwiteit as dié produk te bereik nie. Die diere wat met fisiologiese soutoplossing behandel is toon geen verbetering in enige fisiologiese parameter nie. Die in vitro resultate wat verkry is deur die Du Nouy tensiometer toon hoër gemiddelde ordinaat oppervlaktespannings waardes vir 'n formule wat slegs uit DPPC bestaan, asook vir 'n mengsel van DPPC + trehalose. Die helling van die grafieke van hierdie oplossings is ook kleiner as die van die ander formulas wat daarop dui dat DPPC op sigself, en DPPC + trehalose, weinig vermoë het om oppervlaktespanning te verminder. Daarteenoor verlaag die volgende oplossings die oppervlaktespanning ten opsigte van gedistilleerde water betekenisvol en wel in In konsentrasie afhanklike manier by beide 21°C en 3rc: LMP-I-, LPM-2-, DPPC + trehalose + tyloxapol + CaCf2-, en LPM-2 + CaCf2. Die prominentste ligmikroskopiese bevindinge van die longe van die diere sluit in: Algemene limfvat dilatasie, stuwing, en long neutrofiel infiltrasie. Betreffende hierdie histologiese bevindinge is daar geen verskille aangetoon tussen die groepe nie. Hialienmembrane was teenwoordig in al die groepe, maar betekenisvol meer in die groep wat fisiologiese soutoplossing ontvang as vervangingsterapie. In die tweede in vivo studie is daar 'n betekenisvolle styging in die neutrofiel- en daling in makrofaagtelling, van die brongoalveolêre vloeistof spoeling in al drie die groep aangetoon. Terselfdertyd vind geen noemenswaardige daling in die perifêre (sistematiese) neutrofieltelling plaas nie. Hierdie bevindinge dui daarop dat die brongoalveolêre selveranderinge toegeskryf kan word aan verwerwing van neutrofiele vanuit 'n longstoringspoel eerder as rekrutering vanuit die sistemiese sirkulatoriese poel. Surfaktant (LPM-l), behandeling het geen betekenisvolle vermindering in long inflammasie teweeggebring nie. Epiteelskade was 'n algemene ligmikroskopiese bevinding in al die groepe. Die samestelling van die brongoalveolêre vloeistof verander na installering van LPM-I. Die prominentste verandering word waargeneem in die vetsuur samestelling terwyl die DPPC waardes onveranderd bly. Die vetsuur, palmitiensuur (palmitic acid), (CI6:0), verhoog betekenisvol na toediening van LPM-l. Daarteenoor verminder die konsentrasie van C16:1, C18:0 en C18:2. In kontras met vorige studies, beskryf die huidige studie hoër konsentrasies van fosfatidieletanolamien, moontlik as gevolg van tegniese verskille in die metingsmetodes. 'n Betekenisvolle verlaging in die fosfatidielcholine:sfingomiëlien (PC/SM) verhouding word waargeneem tussen die eerste en die finale longspoeling van die trehalose-groep, terwyl dit onveranderd bly in die diere wat LPM-1 of fisiologiese soutoplossing ontvang.

Gas hydrates are a topic of great interest and intense investigation. Traditionally, these compounds have been seen as a nuisance to the oil and gas industry, which can plug pipelines and cause hours of costly downtime. More recently, gas hydrates have been viewed as a possible energy source due to the vast amount of methane trapped in the form of gas hydrate. Many researchers have also proposed the possibility of transporting natural gas in the form of gas hydrate may be safer and more economical than using liquid or compressed natural gas. Gas hydrate may also offer the possibility of reducing greenhouse gas emissions via the sequestration of carbon dioxide.<br>Surfactants have been found to act as both promoters and inhibitors of hydrate formation. In the present study, the formation rate, solubility and mass transfer conductance of methane in the presence of Gemini surfactant, a new class of surfactants, was studied with varying concentration of Gemini surfactant. The experiments to determine the formation rates of methane hydrate were conducted at 4&deg;C and 6500 kPa. While the experiments to determine solubility and mass conductance were carried out at 4&deg;C and 3800 kPa. The resulting values were used to determine experimental accuracy and reproducibility by comparing the values obtained with literature values and by analyzing the distribution of the data obtained. Solubility measurements were extremely close to literature values with only a 1.4% difference. The distribution of solubility values and formation rates did not deviate significantly between replicates indicating a high degree of reproducibility; however, a lot of variability was observed in mass transfer conductance. This may be attributed to the fact that mass transfer was not determined experimentally by regressing a coefficient to fit a curve, which may be less accurate than other experimentally determined parameters.<br>In the second part of the study, the formation rate, solubility and mass transfer conductance of methane were determined using aqueous Gemini surfactant solutions. The experiments to determine the formation rates of methane hydrate were conducted at 4&deg;C and 6500 kPa. While the experiments to determine solubility and mass transfer conductance were carried out at 4&deg;C and 3800 kPa. The resulting values were used to determine the effect of Gemini surfactant on the properties of interest by comparing the values obtained with aqueous Gemini surfactant with the values previously obtained for pure water. The results obtained showed that solubility increased with increasing concentrations of Gemini surfactant with solubility increasing by up to 18% for higher concentration of Gemini surfactant. The mass transfer conductance was also found to increase by up to 49%; however other than the existence of an increase, no conclusive relationship could be determined between the concentration of Gemini surfactant and mass transfer conductance.<br>Finally, the formation rate of gas hydrates was found to decrease slightly, relative to water, at low concentrations, increased linearly at subsequently higher concentrations and ultimately plateau at a maximum. This trend was in agreement with similar experiments found in literature and the increase in formation rate may be attributed to the increase in both solubility and mass transfer conductance when using aqueous Gemini surfactant.

Thesis (MTech (Chemical Engineering))--Cape Peninsula University of Technology, 2016.<br>Due to the rising cost involve with bringing new fields on stream, of producing residual crude from matured fields, and the significant enhancement in oil recovery provided when compared to conventional water-flooding, increasing attention is being given to chemical flooding technologies. This is particular of interest in mature fields that had previously undergone water flooding. These methods entail injecting chemicals such as surfactant, alkali, and polymer often in mixture into reservoirs to improve oil recovery. In this study a sulfonated surfactant was produced from cheap waste vegetable oils and its performance was assessed in terms of thermal stability at reservoir conditions, adsorption on different reservoir materials, gas chromatography characterization and a limited interfacial tension measurement to evaluate its ability to improve the recovery of crude oil. Waste vegetable oils have great potential as a sustainable and low cost feedstock as well as its low toxicity.

Studies involving solids-stabilised foams have been limited and few have focused on the benefits of complex systems such as those involving mixtures of more than one surfactant. Little is known about the effectiveness of using mixed surfactant systems as foam stabilisers at the bulk level. The purpose of this project was to gain further understanding and insight into foam stability, on a bulk scale, in the absence, and in the presence, of solid colloidal particles, and for systems involving single or mixed surfactants. Foams were produced using sodium dodecyl sulphate (SDS), dodecanoic acid (DA), or a mixture of both surfactants at varying molar ratios. The surface tension at a given concentration, the limiting surface tension (at high concentrations), the critical micelle concentration, foamability and foam stability were all significantly affected by the molar ratio of SDS to DA. The initial pH of mixed surfactant solutions played a role in the shift of surface tension and CMC. The higher pH values, the lower surface activity, therefore resulted in higher surface tension. At a given pH, however, the mixed surfactant solutions with higher molar ratio of SDS to DA appeared to have lower CMC. The foam stabilising ability of colloidal dispersions of four hydrous metal oxides, namely hydrous iron oxide (formed by hydrolysis of Fe(III) solutions and referred to as HFO), hydrous zinc oxide (formed by hydrolysis of Zn(II) solutions and referred to as HZO), hydrous chromium oxide (formed by hydrolysis of Cr(III) solutions and referred to as HCO), and hydrous nickel oxide (formed by hydrolysis of Ni(II) solutions and referred to as HNO) were studied at varying concentrations. Generally foam stability increased as the solid concentration increased. Foams stabilised by HNO were found to be the most stable. Foams stabilised by HFO were found to be unstable regardless of the solid concentration. It is believed that the instability of such foams is primarily due to the large aggregated size of HFO flocs. The aggregate size of hydrous metal oxides was influenced by the concentration of NaOH used to hydrolyse the metal ion solution, and by sonication treatment immediately following solid formation. However, the final pH of the colloidal dispersions did not significantly change the aggregate size. Solids stabilised foams are believed to be highly dependent on the state of hydrophobicity of the solids used, and this is in turn controlled by adjustment of the pH dependent surface charge and potential. Electrophoretic mobility is a commonly used tool to probe the potential near the surface and was used in this thesis to determine the affect of surfactant adsorption (particularly from solutions containing mixtures of SDS and DA) on surface properties of the solids. The electrophoretic mobility of all hydrous metal oxide aggregates decreased as the concentration of SDS/DA increased. Specific adsorption was evident in all cases and resulted in charge reversal for most cases. Electrophoretic mobility data for surfactant adsorption, as a function of total surfactant concentration, was consistent with a three-stage model of surfactant adsorption involving (1) electrostatic adsorption, (2) cooperative adsorption and (3) surface saturation. The influence of surfactant adsorption on electrophoretic mobility was found to be consistent with models requiring the stabilising solids to be in a controlled state of flocculation, where the zeta potential (as probed by electrophoretic mobility) must be sufficiently high to prevent total flocculation of the solid and thus collapse of the foam, but sufficiently low that the solids have some degree of hydrophobicity such that they prefer to be only partially wetted (and thus reside at the air/water interface). The total percentage adsorption of SDS/DA surfactant mixtures on both hydrous iron oxide and hydrous nickel oxide was found to be independent of time. However, the proportion of adsorption due to SDS and DA was dependent on time. Moreover, the initial and final ratio of SDS to DA adsorption did not reflect their ratio in solution. SDS adsorbed, initially, to a greater extent that would be predicted from its solution concentration, but this trend was reversed after a period of time.