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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.

The characterisation of polyacrylamide flocculants.

Hecker, Richard January 1998 (has links)
Polyacrylamide is widely used as a flocculant but the influence of the molecular mass distribution upon flocculant activity is poorly understood. This thesis outlines the successful characterisation of ultrahigh molecular mass polyacrylamide solutions in terms of discrete solvated polymer coils and coil agglomerates. These features were correlated with the observed flocculation, demonstrating a number of solution state features required to improve flocculation activity.Aqueous solutions of polyacrylamide exhibit time-dependant behaviour affecting viscosity and polymer agglomeration. Improving the solvation of the polymer suppressed the agglomerates, as did manipulation of hydrogen bonding through the presence of salts. Limiting agglomeration through improved solvation apparently lowers a barrier to polymer interaction, such that the coils disperse but become more susceptible to reagglomeration under mild shear. These solvent modifications did not fully suppress the agglomerates.To fractionate polyacrylamide into a molecular mass distribution, flow field-flow fractionation (flow FFF) was chosen, coupled to a multi-angle laser light scattering (MALLS) photometer and a differential refractometer for molecular mass and concentration sensitive detection, respectively. For the first time, the analysis of high molecular mass polyacrylamides in water using the flow FFF-MALLS technique has been reported. However, a number of difficulties needed to be overcome, including shear artefacts, sample agglomeration and polymer-membrane interactions.Both polyacrylamide standards and commercial flocculants were amenable to the technique. Commercial flocculants were found to vary not only with regard to viscosity and mean molecular mass, but also with sub- and supramicron size agglomerates. The flow FFF technique is size-sensitive, which for some low molecular mass samples displayed an ++ / unusually wide elution profile, in apparent conflict with the molecular mass sensitive MALLS detector. It was concluded that polyacrylamide in solution exists simultaneously in three states: discrete polymer coils, entanglements of a several coils, and agglomerates with supramicron diameters.This thesis concluded with a comparison between the characterised polyacrylamides and observed flocculation activity on a standard kaolin substrate. Results show polymer with supramicron agglomerates produce the largest and most shear-resistant kaolin aggregates with a definite optimum agitation intensity. Higher molecular mass flocculants with less agglomeration bind fine particles under more gentle conditions but are deficient under increasing stress. Flocculants exhibiting coil entanglements showed poor activity and formed only small aggregates. A modified flocculation mechanism was proposed, in which supramicron polymer agglomerates play a critical role.

Effect of polyacrylamides on the physical properties of some light-textured soils.

Phillips, Shane January 2007 (has links)
The work presented in this thesis represents a combination of laboratory and field experiments designed to explain some field observations I made on some coarse sands in South Australia in 1999: that much of the irrigation water and nutrients applied to the sands under drip-irrigation simply passed through the root zone leaving the crops water-stressed shortly after irrigation events. There was clearly only minimal lateral spread of the water in these coarse sands. However, by applying small concentrations of polyacrylamide or ‘PAM’ in the irrigation water, the crops seemed to do better. Furthermore the timing of irrigation events appeared to be more flexible on the PAM-treated properties. I found this intriguing and saw an opportunity to increase the lateral spread of water in the root zone and thereby increasing the stored volume and residence time of water. By retaining more water in the rootzone, there was potential to save a considerable amount of costly irrigation water, and also improve crop production and quality. With encouragement from my then employer (Elders Pty Ltd) and from Ciba Specialty Chemicals Australia, I undertook to explore my findings in greater detail and to attempt to explain them based on some ‘hard’ (experimental) evidence. Increasing the lateral spread of water under drippers in coarse-textured soils requires water to be retained in the root zone for longer periods during irrigation, but the practical methods for doing this are limited to: • Altering the pore size distribution to create a finer average range of pore sizes, either by compaction or by stabilization of smaller pores using organic matter or additions of clay. • Reducing the wettability of the soil so that less water can be taken in and the soil never becomes saturated. (This of course risks surface runoff and suboptimal placement of irrigation water). • Altering the physical properties of irrigation water (eg. viscosity, surface tension) so that it interacts differently with soil pores and moves through them more slowly. The aim of the research was therefore to evaluate the potential for some commercially available PAMs to reduce hydraulic conductivity and to increase water retention on some drip-irrigated coarse sandy soils of South Australia and Victoria. I worked with two commonly available anionic polyacrylamides, designated PAM-1011 and PAM-135, and measured ponded infiltration in laboratory columns of seven different sandy soils from around South Australia and Victoria. I varied the concentration of the polymer within the range typically used in the field (0, 1 and 10 ppm for PAM-1011; 0, 2.5 and 25 ppm for PAM-135) and I also varied the quality of the irrigation water used to mix the PAM solutions in terms of salinity and sodicity (distilled water, 10 and 20 mmol(+) salt/L, using either sodium chloride, calcium chloride, or both). I measured the effects of PAM on pore-size distribution of one of the sands (by the water retention characteristic), on water repellence of the soils (by measuring water droplet penetration times), and the kinematic viscosity of the PAM solutions at various concentrations with various qualities of irrigation water. I also set up transparent cases of sand to observe infiltration and wetting behaviour of the PAM solution. Finally, with some understanding of how the physical and chemical properties of the PAMs, I conducted a field trial to measure the soil water matric potential at various depths and locations around drippers in vine rows receiving PAM in the irrigation water. Laboratory findings: The polymer PAM-1011 significantly reduced the steady-state infiltration rate in all sands, and it did this with relatively modest concentrations (< 10 ppm). The polyacrylamide PAM-135 was not effective for this purpose, which indicated that the chemical properties of the polymer (not investigated here) influenced its physical behaviour. Further work with PAM-135 was therefore discontinued in favour of PAM-1011. The effectiveness of PAM-1011 in reducing steady-state infiltration rates was related to changes in the properties of the irrigating solution caused by PAM-1011 rather than by a change in the properties of the soils to which it is applied. For example, PAM-1011 had only minimal (if any) influence on the pore size distribution (water retention) of a coarse sandy soil and had no significant impact on water repellence (wettability) of another sandy soil. It did, however, have a large impact on the kinematic viscosity of the irrigating solution, and the more PAM-1011 that was dissolved, the more viscous the solutions became. The effectiveness of PAM-1011 in reducing steady-state infiltration rates was reduced in salty irrigation water, and there was evidence to suggest that cation-effects may have been involved. When PAM-1011 was dissolved in distilled water, infiltration rates were reduced by the greatest amount. When PAM-1011 was dissolved in salty water containing the monovalent cation, sodium, infiltration rates were not reduced as much; furthermore, if the solvent water contained the divalent cation, calcium, PAM-1011 was even less effective than in sodium-rich water. Thus electrolytes affected the physical conformation of PAM-1011 solutions, altering viscosity. To overcome the salt-water effects, higher concentrations of PAM-1011 needed to be used. The cation-effects were primarily related to the way each cation interacted with the polymer to alter its kinematic viscosity. PAM-1011 in distilled water had the greatest viscosity, while PAM-1011 in sodium-rich water had a lower viscosity, and PAM-1011 in calcium-rich water had the lowest viscosity. A practical implication from this is that irrigators using salty waters will need to dissolve more PAM-1011 in their water-sources to increase the viscosity and thus gain the retarding effects of the polymer on infiltration rates. The data suggest that the amount of polymer required to overcome the salt effects is about 10 ppm PAM-1011. Rates as low as 1 ppm can be used when irrigators have access to high-quality water with < 10 mmol(+) salt/L present. Visual observations of the wetting fronts during infiltration showed that irrigation water containing PAM-1011 at between 1 and 10 ppm reduced the depth of percolation and increased its lateral spread in coarse sands. Field study: The field work was largely unsuccessful because shortly after the treatments were applied, a 1-in-100 year hailstorm struck that completely wiped out the vegetation on the vines in the study. I spent most of the season simply trying to keep the vines alive and to recover some of the leaf area for future years. Overall, however, this work identified the ability of PAM-1011 to reduce water movement through the root zone of coarse sands, and demonstrates the potential to conserve a great deal of water – a significant move toward higher water- and nutrient-use efficiencies on the coarser textured soils in the Murray-Darling Basin. / Thesis (M.App.Sc.) -- University of Adelaide, School of Earth and Environmental Sciences, 2007

Polyacrylamide gels synthesized in the presence of surfactants

Chakrapani, Mukundan. Van Winkle, David H. January 2003 (has links)
Thesis (Ph. D.)--Florida State University, 2003. / Advisor: Dr. David H. Van Winkle, Florida State University, College of Arts and Sciences, Department of Physics. Title and description from dissertation home page (viewed Oct. 1, 2003). Includes bibliographical references.

Untersuchungen zur Dynamik in Polyactrylamid-Lösungen und -Gelen mittels Fluoreszenzkorrelationsspektroskopie

Gansel, Julia January 2009 (has links)
Zugl.: Clausthal, Techn. Univ., Diss., 2009

Site blocking effects on adsorbed polyacrylamide conformation

Brotherson, Brett Andrew. January 2007 (has links)
Thesis (Ph.D)--Chemical Engineering, Georgia Institute of Technology, 2008. / Committee Chair: Yulin Deng; Committee Co-Chair: Peter Ludovice; Committee Member: James Frederick; Committee Member: Lawrence Bottomley; Committee Member: Preet Singh. Part of the SMARTech Electronic Thesis and Dissertation Collection.

Synthese und Untersuchung von neuen a, w-funktionalisierten Lipopolymeren zum Aufbau von polymerunterstützten Lipiddoppelschichten

Théato, Patrick. Unknown Date (has links) (PDF)
Universiẗat, Diss., 2001--Mainz.

Field Implementation Of Polyacrylamide For Runoff From Construction Sites

Chowdhury, Rafiqul Islam 01 January 2011 (has links)
Polyacrylamide (PAM) is often used a part of a treatment train for the treatment of stormwater to reduce its turbidity. This study investigated the application of PAM within various treatment systems for a construction site environment. The general concept is to introduce hydraulic principles when placing PAM blocks within an open channel in order to yield high mixing energies leading to high turbidity removal efficiency. The first part of the study observed energy variation using a hydraulic flume for three dissimilar configurations. The flume was ultimately used to determine which configuration would be most beneficial when transposed into field-scale conditions. Three different configurations were tested in the flume, namely, the Jump configuration, Dispersion configuration and the Staggered configuration. The field-scale testing served as both justification of the findings within the controlled hydraulic flume and comprehension of the elements introduced within the field when attempting to reduce the turbidity of stormwater. As a result, the Dispersion configuration proved to be the most effective when removing turbidity and displayed a greater energy used for mixing within the open channel. Consequently, an analysis aid is developed based on calculations from the results of this study to better serve the sediment control industry when implementing PAM blocks within a treatment system. Recommendations are made for modification and future applications of the research conducted. This innovative approach has great potential for expansion and future applications. Continued research on this topic can expand on key elements such as solubility of the PAM, toxicity of the configuration within the field, and additional configurations that may yield more advantageous energy throughout the open channel.

Muscles artificiels à base d’hydrogel électroactif / Artificial muscle fabrication based on electroactive hydrogel

Bassil, Maria 15 September 2009 (has links)
Les hydrogels de Polyacrylamide (PAAM) hydrolysés sont des matériaux électroactifs biocompatibles non biodégradables. Ils possèdent des propriétés très proches de celles du muscle naturel et leur mode opérationnel basé sur la diffusion d’ions est similaire à celui existant dans les tissus musculaires naturels. Compte tenu de ces caractéristiques, ces hydrogels sont de bons candidats pour la conception de nouveaux muscles artificiels. Le problème qui limite leur utilisation réside dans leur temps de réponse qui reste encore inférieur à celui du système de fibres musculaires naturelles. Leur fonction actuatrice est limitée par le phénomène de diffusion en raison de leur structure massique qui est à l’origine de cycles de fonctionnement relativement lents. Dans le but de développer un nouveau système artificiel mimant le comportement du muscle squelettique naturel cette étude se divise en deux grandes étapes. La première étape vise le développement d’une étude de la synthèse de l’hydrogel de PAAM et de son mode de fonctionnement. Dans cette étude les effets des paramètres gouvernant la polymérisation sur les propriétés des hydrogels sont évalués. Les propriétés électrochimiques et le mécanisme d’activation des actuateurs soumis à une excitation électrique sont étudiés et le mode de fonctionnement des actuateurs est caractérisé et expliqué. La seconde étape est la proposition et le développement d’une nouvelle architecture de muscle artificiel à base de PAAM. Cette architecture consiste en une structure fibreuse du gel encapsulée par une couche en gel conducteur jouant le rôle d’électrodes. La structure fibreuse permet au système d’exhiber une réponse rapide et la couche en gel améliore ses propriétés mécaniques. Comme un premier pas dans la réalisation du modèle nous avons mis en place un nouveau procédé basé sur la technique d’électrofilage qui permet la génération de fibres linéairement disposées. En utilisant ce processus nous avons réussi à fabriquer des microfibres de PAAM réticulées, électroactives montrant des réponses rapides. / Hydrolyzed Polyacrylamide (PAAM) hydrogels are electroactive, biocompatible and non-biodegradable materials. Their main attractive characteristic is their operative similarity with biological muscles and particularly their life-like movement. They suit better the artificial muscle fabrication despite their response time which stays low compared to natural human muscle due to their bulky structure and due to the kinetics of the size dependence of their volume change. In order to copy the natural skeletal muscle design into a new artificial muscle system this study is divided into two steps. The first step is the development of a comprehensive study of the hydrogel itself in order to obtain the elementary background needed for the design of actuating devices based on this material. The effect of polymerization parameter on the hydrogel properties is investigated. The electrochemical properties and actuation mechanisms of the hydrogel is studied, the bending of PAAM actuators induced by electric field is discussed and a mechanism for the bending phenomenon is proposed. The second step is the proposition of a new artificial muscle architecture based on PAAM hydrogel. The model consists on a fiber like elements of hydrolyzed PAAM, working in parallel, embedded in a thin conducting gel layer which plays the role of electrodes. The fiber-like elements enable the system to exhibit relatively rapid response and the gel layers enhance their mechanical properties. Aiming to realize the model we have put in place a new electrospinning setup which is a modified process for the production of micro to nanofibers via electrostatic fiber spinning of polymer solutions. The main advantage of this technology is to produce aligned electrospun fibers over large areas by simple and a low cost process making it possible to produce fiberbased devices efficiently and economically. Using this setup, we succeeded in the fabrication of electroactive crosslinked hydrogel microfibers that can achieve fast electroactive response

Canal seepage reduction using anionic polyacrylamide field and bench-scale tests /

Story, Brian T. January 2007 (has links)
Thesis (M.S.)--University of Wyoming, 2007. / Title from PDF title page (viewed on June 17, 2008). Includes bibliographical references.

Evaluation of anionic polyacrylamide as an erosion control measure using intermediate-scale experimental procedures

Shoemaker, Alexander Lee, Zech, Wesley C., January 2009 (has links)
Thesis--Auburn University, 2009. / Abstract. Vita. Includes bibliographical references (p. 118-121).

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