<p>У овој докторској дисертацији приказани су резултати синтеза и карактеризација нано-композитних честица са језгро-омотач структуром. Нанокомпозитне честице су синтетисане у течној фази, електростатичком депозицијом in situ синтетисаних SiO2, Fe3O4, ZnFe2O4 или NiFe2O4 наночестица на површину монодисперзних и сферичних силика језгро честица (средњег пречника ~ 0,4 &mu;m). Силика језгро честице су синтетисане хидролизом и кондезацијом TEOS-a у базној средини. Силика наночестице су добијене неутрализацијом јако базног воденог раствора натријум силиката, док су феритне наночестице синтетисане копреципитацијом из воденог раствора одговарајућих нитратних соли. Да би се омогућила електростатичка депозиција нано-честица, силика језгра су функционализована са 3-аминопропилтриетоксисилан (APTES) или поли(диалилдиметиламонијум хлорид) (PDDA) чиме се повећава изоелектрична тачка силика честица. На овај начин су око силика језгро честица синтетисани једнослојни омотачи на бази SiO2, Fe3O4, ZnFe2O4 или NiFe2O4.<br />Резултати су потврдили да се униформан силика слој може депоновати на функцијонализованим силика честицама. Формиран силика омотач је имао дебљину ~ 30 nm, мезопорозну структуру са средњом величином пора од ~ 8 nm и значајном укупном запремином пора. Због тога су тако добијене силика језгро-омотач наноструктуре погодне за имобилизацију ензима али и неких других активних материја. Такође је потврђено да је оптимална pH вредност за синтезу хомогеног Fe3O4 омотача на нефункционализованим силика језгрима ~ 5,4. Добијени Fe3O4 омотач је суперпа-рамагнетан са температуром блокирања ~ 25 К. Уградња никла и цинка у феритну структуру омотача није било могуће на нижим pH вредностима. Међутим, показано је и да је на вишим pH вредностима велика брзина формирања феритних честица и њихова самоагрегација доминира над конкурентном реакцијом депозиције феритних честица на функционализована силика језгра. У циљу спречавања самоагрегације, депо-зиција ZnFe2O4 и NiFe2O4 наночестица на PDDA-функционализованим силика језгрима је обављена у присуству цитратне киселине на pH &gt; 7. Цитратна киселина пасивизира површину феритних наночестица и на тај начин инхибира самоагрегацију, омогућавајући депозицију ових честица на површину PDDA-функционализованих силика језгара.<br />У овој тези су синтетисане честице са двослојним омотачем, који се састоје од унутрашњег Fe3O4 и спољашњег силика слоја. На PDDA-функцио-нализованим SiO2-језгро/Fe3O4-омотач честицама, обављена је депозиција силика наночестица чиме је формиран спољни мезопорозни силика омотач. Добијене су композитне честице са два различита функционална слоја: унутрашњим који омогућава магнетну сепарацију честице из реакционог медијума и спољним који омогућава имобили-зацију активних материја. Добијени резултати су указали да се ове нанокомпозитне честице могу употребити у биоинжењерству и областима хертерогене катализе.</p> / <p>U ovoj doktorskoj disertaciji prikazani su rezultati sinteza i karakterizacija nano-kompozitnih čestica sa jezgro-omotač strukturom. Nanokompozitne čestice su sintetisane u tečnoj fazi, elektrostatičkom depozicijom in situ sintetisanih SiO2, Fe3O4, ZnFe2O4 ili NiFe2O4 nanočestica na površinu monodisperznih i sferičnih silika jezgro čestica (srednjeg prečnika ~ 0,4 &mu;m). Silika jezgro čestice su sintetisane hidrolizom i kondezacijom TEOS-a u baznoj sredini. Silika nanočestice su dobijene neutralizacijom jako baznog vodenog rastvora natrijum silikata, dok su feritne nanočestice sintetisane koprecipitacijom iz vodenog rastvora odgovarajućih nitratnih soli. Da bi se omogućila elektrostatička depozicija nano-čestica, silika jezgra su funkcionalizovana sa 3-aminopropiltrietoksisilan (APTES) ili poli(dialildimetilamonijum hlorid) (PDDA) čime se povećava izoelektrična tačka silika čestica. Na ovaj način su oko silika jezgro čestica sintetisani jednoslojni omotači na bazi SiO2, Fe3O4, ZnFe2O4 ili NiFe2O4.<br />Rezultati su potvrdili da se uniforman silika sloj može deponovati na funkcijonalizovanim silika česticama. Formiran silika omotač je imao debljinu ~ 30 nm, mezoporoznu strukturu sa srednjom veličinom pora od ~ 8 nm i značajnom ukupnom zapreminom pora. Zbog toga su tako dobijene silika jezgro-omotač nanostrukture pogodne za imobilizaciju enzima ali i nekih drugih aktivnih materija. Takođe je potvrđeno da je optimalna pH vrednost za sintezu homogenog Fe3O4 omotača na nefunkcionalizovanim silika jezgrima ~ 5,4. Dobijeni Fe3O4 omotač je superpa-ramagnetan sa temperaturom blokiranja ~ 25 K. Ugradnja nikla i cinka u feritnu strukturu omotača nije bilo moguće na nižim pH vrednostima. Međutim, pokazano je i da je na višim pH vrednostima velika brzina formiranja feritnih čestica i njihova samoagregacija dominira nad konkurentnom reakcijom depozicije feritnih čestica na funkcionalizovana silika jezgra. U cilju sprečavanja samoagregacije, depo-zicija ZnFe2O4 i NiFe2O4 nanočestica na PDDA-funkcionalizovanim silika jezgrima je obavljena u prisustvu citratne kiseline na pH &gt; 7. Citratna kiselina pasivizira površinu feritnih nanočestica i na taj način inhibira samoagregaciju, omogućavajući depoziciju ovih čestica na površinu PDDA-funkcionalizovanih silika jezgara.<br />U ovoj tezi su sintetisane čestice sa dvoslojnim omotačem, koji se sastoje od unutrašnjeg Fe3O4 i spoljašnjeg silika sloja. Na PDDA-funkcio-nalizovanim SiO2-jezgro/Fe3O4-omotač česticama, obavljena je depozicija silika nanočestica čime je formiran spoljni mezoporozni silika omotač. Dobijene su kompozitne čestice sa dva različita funkcionalna sloja: unutrašnjim koji omogućava magnetnu separaciju čestice iz reakcionog medijuma i spoljnim koji omogućava imobili-zaciju aktivnih materija. Dobijeni rezultati su ukazali da se ove nanokompozitne čestice mogu upotrebiti u bioinženjerstvu i oblastima herterogene katalize.</p> / <p>This thesis presents the results of the synthesis and characterization of the nanocomposite particles with core-shell structure. Nanocomposite particles were synthesized by liquid-phase technique through electrostatic deposition of in situ synthesized SiO2, Fe3O4, ZnFe2O4 or NiFe2O4 nanoparticles on the surface of spherical and monodispersed silica core particles (average size ~ 0.4 &mu;m). Silica core particles were prepared by hydrolysis and condensation of tetraethylorthosilicate in basic conditions. Silica nanoparticles were obtained by neutralization of highly basic sodium silicate solution while ferrite nanoparticles were obtained by coprecipitation from solutions of the corresponding nitrate salts. To improve electrostatic assembling of nanoparticles on the surface of silica core particles, the latter were functionalized with 3-amino-propyltriethoxysilane (APTES) or poly(diallyldimethylammonium chloride) (PDDA) which increases the isoelectric point of the silica core particles. In this way SiO2, Fe3O4 , ZnFe2O4 or NiFe2O4 shells were synthesized around the silica core particles, respectively.<br />The results confirmed that uniform silica layer can be deposited at the functionalized silica core particles. The formed silica layer had thickness of ~ 30 nm, mesoporous structure with average pore size of ~ 8 nm and high total pore volume. This makes silica shell suitable for immobilization of enzymes. Optimal conditions for synthesis of homogenous and thin Fe3O4 shell around non-functionalized silica core particles were found at pH ~ 5.4. Obtained Fe3O4 shell was superparamagnetic with blocking temperature at ~25 К. Incorporation of nickel and zinc into ferrite structure was impossible at lower pH values. However at higher pH the formation rate of Ni- and Zn-ferrite particles becomes very fast and the self-aggregation dominates the competing formation of the ferrite shell around functionalized silica cores. Because of that the self-aggregation was prevented by surface modify-cation of ZnFe2O4 and NiFe2O4 nanoparticles with citric acid before their deposition on the PDDA-functionalized silica core and homogenous and continuous shells were finally obtained at pH &gt; 7.<br />In addition, bilayered shell composed of internal Fe3O4 layer and external SiO2 layer, were also prepared. Silica nanoparticles were deposited on the surface of PDDA-functionalized SiO2-core/Fe3O4-shell particles which induced formation of external mesoporous silica shell. Obtained composite particles had two different functional layers: internal which would allow its magnetic separation from reaction mixture and external which could allow imobilization of various molecules and nanoparticles such as enzymes inside its pores. Based on these results, obtained nanoparticles could be used in bioengineering and heterogenous catalysis.</p>

Die Sammlung der zwei-dimensionalen (2D) Materialien ist begrenzt, da sehr wenige Verbindungen stabil bleiben, sobald sie nur aus Oberflächen bestehen. Aufgrund ihrer außergewöhnlichen Eigenschaften sind 2D Materialien jedoch nach wie vor überaus begehrt. Vor kurzem wurden atomar definierte, chemisch gesättigte SiO2 Bilagen auf verschiedenen Metalloberflächen präpariert. Eine solche ultradünne Silika-Lage wäre eine vielversprechende Ergänzung zur Familie der 2D Materialien, wenn sie unter Strukturerhalt vom Wachstumssubstrat isoliert werden kann. In dieser Arbeit untersuchen wir die Eigenschaften einer Silika-Bilage im Zusammenhang mit Anwendungen von 2D Materialien. Die Bilage besitzt kristalline und amorphe Regionen, die beide atomar glatt sind. Die kristalline Region besitzt ein hexagonales Gitter mit gleichmäßiger Porengröße, während die amorphe Region einer komplexeren Beschreibung bedarf. In einer Studie von Baublöcken zeigen wir, dass mittelreichweitige Struktureinheiten in Korrelation mit einem Parameter für die Bindungswinkelfrustration auftreten. Das Netzwerk verschiedener Nanoporen stellt eine größenselektive Membran dar, wie wir in einer Adsorptionsstudie zeigen. Pd- und Au-Atome durchdringen den Silikafilm abhängig von der Größe der zur Verfügung stehenden Nanoporen. Der ultradünne Film hält der Einwirkung verschiedener Lösungsmittel stand und die Beständigkeit der Struktur in Wasser wird analysiert. Diese Studien deuten die außergewöhnliche Stabilität dieser Struktur an. Wir entwickeln eine polymerbasierte mechanische Exfoliation, um den Film von seinem Wachstumssubstrat zu entfernen, und zeigen, dass der Film als intakte Einheit vom Substrat abgelöst wird. Wir präsentieren anschließend den Transfer des Silikafilms auf ein TEM-Gitter, wo er schraubenartig gewundene Formen annimmt. Weiterhin wurde der Film auf ein Pt(111)-Substrat transferiert. In diesem Fall wird unter Erhalt der Struktur ein Transfer in der Größenordnung von Millimetern erreicht. / The library of two-dimensional (2D) materials is limited, since only very few compounds remain stable when they consist of only surfaces. Yet, due to their extraordinary properties, the hunt for new 2D materials continues. Recently, an atomically defined, self-saturated SiO2 bilayer has been prepared on several metal surfaces. This ultrathin silica sheet would be a promising addition to the family of 2D materials, if it can be isolated from its growth substrate without compromising its structure. In this work, we explore the properties of a silica bilayer grown on Ru(0001) in the context of 2D technology applications. The bilayer sheet exhibits crystalline and amorphous regions, both being atomically flat. The crystalline region possesses a hexagonal lattice with uniform pore size, while the amorphous region requires a more complex description. In a building block study of the amorphous region, we find that medium range structural patterns correlate with a parameter describing the bond angle frustration. The resulting network of different nanopores represents a size-selective membrane, as illustrated in an adsorption study. Pd and Au atoms are shown to penetrate the silica film selectively, depending on the presence of appropriately sized nanopores. The ultrathin silica film is shown to withstand exposure to different solvents and the stability of the structure in water is analyzed. These studies indicate extraordinary stability of this nanostructure. We develop a polymer assisted mechanical exfoliation method for removing the film from the growth substrate, providing evidence that the film is removed as an intact sheet from the growth substrate. We subsequently present the transfer of the silica bilayer to a TEM grid, where it forms micro-ribbons. Further, the film is transferred to a Pt(111) substrate, where mm-scale transfer under retention of the structure is achieved.

The epoxy based polymer is one of the very common polymers, which was used as a host to create new better materials - nanocomposites. This thesis focused on the improvement of the thermomechanical properties of the epoxy thermosets without deteriorating their existing benefits and on further potential application of this knowledge in "smart" systems. The largest part of this work is dedicated to the reinforcement of epoxy thermosets by in situ generated silica and synthesis of organic-inorganic nanocomposites. Borontrifluoride monoethylamine (BF3MEA) was chosen as effective catalyst for the formation of nanosilica in epoxy-amine network matrix under nonaqueous (non-hydrolytic) sol-gel process. We proposed the mechanism of the nonaqueous sol-gel procedure, studied the structure evolution during the nanocomposite formation, and also determined the structure, morphology and thermomechanical properties of the obtained epoxy-silica nanocomposites. Significant attention in this work was given to the application of coupling agent and ionic liquids to improve compatibilization of the organic matrix and the inorganic part. As a result of the nonaqueous sol-gel process optimization by combination of the tetramethoxysilane (TMOS) and the coupling agent glycidyloxypropyltrimethoxysilane (GTMS), the high-Tg and...

The Ceratium species occurring in the Vaal River since 2000, was identified as Ceratium hirundinella (O.F. Müller) Dujardin as proposed by Van Ginkel et al (2001). Ceratium hirundinella is known to cause problems in drinking water purification and has been penetrating into the final drinking water of Rand Water since 2006. Ceratium hirundinella is associated with many other water purification problems such as disrupting of the coagulation and flocculation processes, blocking of sand filters and algal penetration into the drinking water. Ceratium hirundinella also produce fishy taste and odorous compounds and causes discolouration of the water. The aims of this study were to determine the main environmental factors which are associated with the bloom formation of C. hirundinella in the source water and to investigate the influence of C. hirundinella on the production of potable water. In order to optimise treatment processes and resolve problems associated with high C. hirundinella concentrations during the production of potable water, jar testing and chlorine exposure experiments were performed. Multivariate statistical analyses were performed to determine the main environmental variables behind C. hirundinella blooms. Ten years data (2000 - 2009) from the sampling point C–VRB5T in the Vaal River, (5 km upstream from the Barrage weir) were used for this investigation, because C. hirundinella occurred there frequently during the ten year period. In this study, it was found that C. hirundinella was favoured by high pH, Chemical Oxygen Demand (COD), orthophoshapte (PO4), and silica concentrations, as well as low turbidity and low dissolved inorganic nitrogen (DIN) concentrations. No correlation was found between C. hirundinella and temperature, suggesting that this alga does not occur during periods of extreme warm or extreme cold conditions, but most probably during autumn and spring. The results of the multivariate statistical analysis performed with historical data from Vaalkop dam, indicate that the dinoflagellate C. hirundinella seems to be favoured by low temperature and turbidity, and high DIN, Fe, Methyl–orange alkalinity, Cd, PO4, Conductivity, pH, hardness and SO4 concentrations. In order to optimise treatment processes such as coagulation, flocculation and sedimentation, jar testing experiments were performed to investigate different coagulant chemicals namely: cationic poly–electrolyte only, cationic poly–electrolyte in combination with slaked lime (CaO) and CaO in combination with activated silica. Water from four different sampling localities were chosen to perform the different jar testing experiments: 1) sampling point M–FOREBAY (in the Forebay, connecting the canal to the Zuikerbosch Purification plant) near Vereeniging due to its proximity to the Zuikerbosch treatment plant, 2) M–CANAL_VD (upstream from the inflow of the recovered water from Panfontein) to determine the influence of (if any) the recovered water from Panfontein on Forebay source water, 3) source water from Vaalkop Dam (M–RAW_VAALKOP) and 4) source water from Rietvlei Dam (water from both Vaalkop and Rietvlei Dams contained high concentrations of C. hirundinella at that time of sampling) to determine which coagulant chemical is the most effective in removing high concentrations of C. hirundinella cells during the production of drinking water. The jar testing experiments with Vaalkop Dam and Rietvlei Dam source water (rich with C. hirundinella) indicated that using cationic poly–electrolyte alone did not remove high concentrations of C. hirundinella efficiently. However, when CaO (in combination with cationic poly–electrolyte or activated silica) were dosed to Vaalkop Dam source water a significant decrease of C. hirundinella concentration was observed. This indicates that the C. hirundinella cells were “shocked or stressed” when exposed to the high pH of the CaO, rendering it immobile and thereby enhancing the coagulation and flocculation process. However, when 10 mg/L CaO in combination with poly–electrolyte was dosed to Rietvlei Dam source water the turbidity and chlorophyll–665 results indicated that this coagulant chemical procedure was ineffective in removing algal material from the source water. The jar testing experiments using the cationic poly–electrolyte alone or cationic poly–electrolyte in combination with CaO on M–FOREBAY and M–CANAL_VD source water, showed a decrease in turbidity, chlorophyll–665 concentration, and total algal biomass, with an increase of coagulant chemical. When CaO in combination with activated silica was dosed, the inherent turbidity of the lime increased the turbidity of the Vaalkop Dam, M–FOREBAY and M–CANAL_VD source water to such an extent that it affected coagulation negatively, resulting in high turbidity values in the supernatant. Regardless of the turbidity values, the chlorophyll–665 concentration and total algal biomass (C. hirundinella specifically in Vaalkop Dam source water) decreased significantly when CaO was dosed in combination with activated silica. Therefore it was concluded that a cationic poly–electrolyte alone is a good coagulant chemical for the removal of turbidity, but when high algal biomass occur in the source water it is essential to add CaO to “stress” or “shock” the algae for the effective removal thereof. However, when CaO in combination with activated silica was dosed to Rietvlei Dam source water a decrease in turbidity and chlorophyll–665 concentration was found with an increasing coagulant chemical concentration. These results confirm the fact that coagulant chemicals may perform differently during different periods of the year when water chemistry changes and that certain coagulant chemicals may never be suitable to use for certain source waters. For the effective removal of algae during water purification, it is recommended that cationic poly–electrolyte in combination with CaO are used as coagulant chemical at the Zuikerbosch Water Purification Plant. Turbidity is not a good indication of algal removal efficiency during jar testing experiments. If problems with high algal concentrations in the source water are experienced it is advisable to also determine the chlorophyll–665 concentrations of the supernatant water during the regular jar testing experiments, since it will give a better indication of algal removal. Chlorine exposure experiments were performed on water from Vaalkop Dam (M–RAW_VAALKOP) and Rietvlei Dam source water, to determine the possibility of implementing pre– or intermediate chlorination with the aim to render the cells immobile for more effective coagulation. The chlorine exposure experiments with Vaalkop Dam and Rietvlei Dam source water showed similar results. The chlorine concentration to be dosed as part of pre– or intermediate chlorination will differ for each type of source water as the chemical and biological composition of each water body are unique. When the effect of chlorine on the freshwater dinoflagellate C. hirundinella was investigated, it was found that the effective chlorine concentration where 50 % of Ceratium cells were rendered immobile (EC50) was approximately 1.16 mg/L for Vaalkop Dam source water. For the source water sampled from Rietvlei Dam, it was found that the EC50 was at approximately 0.87 mg/L. Results of analyses to determine the organic compounds in the water after chlorination revealed that an increase in chlorine concentration resulted in increase in total organic carbon concentration (TOC), as well as a slight increase in MIB and trihalomethanes (CHCl3). Pre– or intermediate chlorination seem to be an effective treatment option for the dinoflagellate C. hirundinella to be rendered immobile and thereby assisting in its coagulation process. The use of pre– or intermediate chlorination to effectively treat source waters containing high concentrations of C. hirundinella is a viable option to consider. However, the organic compounds in the water should be monitored and the EC50 value for each source water composition should be determined carefully as to restrict cell lysis and subsequent release of organic compounds into the water. / Thesis (M.Sc. (Environmental Science))--North-West University, Potchefstroom Campus, 2012.

The Ceratium species occurring in the Vaal River since 2000, was identified as Ceratium hirundinella (O.F. Müller) Dujardin as proposed by Van Ginkel et al (2001). Ceratium hirundinella is known to cause problems in drinking water purification and has been penetrating into the final drinking water of Rand Water since 2006. Ceratium hirundinella is associated with many other water purification problems such as disrupting of the coagulation and flocculation processes, blocking of sand filters and algal penetration into the drinking water. Ceratium hirundinella also produce fishy taste and odorous compounds and causes discolouration of the water. The aims of this study were to determine the main environmental factors which are associated with the bloom formation of C. hirundinella in the source water and to investigate the influence of C. hirundinella on the production of potable water. In order to optimise treatment processes and resolve problems associated with high C. hirundinella concentrations during the production of potable water, jar testing and chlorine exposure experiments were performed. Multivariate statistical analyses were performed to determine the main environmental variables behind C. hirundinella blooms. Ten years data (2000 - 2009) from the sampling point C–VRB5T in the Vaal River, (5 km upstream from the Barrage weir) were used for this investigation, because C. hirundinella occurred there frequently during the ten year period. In this study, it was found that C. hirundinella was favoured by high pH, Chemical Oxygen Demand (COD), orthophoshapte (PO4), and silica concentrations, as well as low turbidity and low dissolved inorganic nitrogen (DIN) concentrations. No correlation was found between C. hirundinella and temperature, suggesting that this alga does not occur during periods of extreme warm or extreme cold conditions, but most probably during autumn and spring. The results of the multivariate statistical analysis performed with historical data from Vaalkop dam, indicate that the dinoflagellate C. hirundinella seems to be favoured by low temperature and turbidity, and high DIN, Fe, Methyl–orange alkalinity, Cd, PO4, Conductivity, pH, hardness and SO4 concentrations. In order to optimise treatment processes such as coagulation, flocculation and sedimentation, jar testing experiments were performed to investigate different coagulant chemicals namely: cationic poly–electrolyte only, cationic poly–electrolyte in combination with slaked lime (CaO) and CaO in combination with activated silica. Water from four different sampling localities were chosen to perform the different jar testing experiments: 1) sampling point M–FOREBAY (in the Forebay, connecting the canal to the Zuikerbosch Purification plant) near Vereeniging due to its proximity to the Zuikerbosch treatment plant, 2) M–CANAL_VD (upstream from the inflow of the recovered water from Panfontein) to determine the influence of (if any) the recovered water from Panfontein on Forebay source water, 3) source water from Vaalkop Dam (M–RAW_VAALKOP) and 4) source water from Rietvlei Dam (water from both Vaalkop and Rietvlei Dams contained high concentrations of C. hirundinella at that time of sampling) to determine which coagulant chemical is the most effective in removing high concentrations of C. hirundinella cells during the production of drinking water. The jar testing experiments with Vaalkop Dam and Rietvlei Dam source water (rich with C. hirundinella) indicated that using cationic poly–electrolyte alone did not remove high concentrations of C. hirundinella efficiently. However, when CaO (in combination with cationic poly–electrolyte or activated silica) were dosed to Vaalkop Dam source water a significant decrease of C. hirundinella concentration was observed. This indicates that the C. hirundinella cells were “shocked or stressed” when exposed to the high pH of the CaO, rendering it immobile and thereby enhancing the coagulation and flocculation process. However, when 10 mg/L CaO in combination with poly–electrolyte was dosed to Rietvlei Dam source water the turbidity and chlorophyll–665 results indicated that this coagulant chemical procedure was ineffective in removing algal material from the source water. The jar testing experiments using the cationic poly–electrolyte alone or cationic poly–electrolyte in combination with CaO on M–FOREBAY and M–CANAL_VD source water, showed a decrease in turbidity, chlorophyll–665 concentration, and total algal biomass, with an increase of coagulant chemical. When CaO in combination with activated silica was dosed, the inherent turbidity of the lime increased the turbidity of the Vaalkop Dam, M–FOREBAY and M–CANAL_VD source water to such an extent that it affected coagulation negatively, resulting in high turbidity values in the supernatant. Regardless of the turbidity values, the chlorophyll–665 concentration and total algal biomass (C. hirundinella specifically in Vaalkop Dam source water) decreased significantly when CaO was dosed in combination with activated silica. Therefore it was concluded that a cationic poly–electrolyte alone is a good coagulant chemical for the removal of turbidity, but when high algal biomass occur in the source water it is essential to add CaO to “stress” or “shock” the algae for the effective removal thereof. However, when CaO in combination with activated silica was dosed to Rietvlei Dam source water a decrease in turbidity and chlorophyll–665 concentration was found with an increasing coagulant chemical concentration. These results confirm the fact that coagulant chemicals may perform differently during different periods of the year when water chemistry changes and that certain coagulant chemicals may never be suitable to use for certain source waters. For the effective removal of algae during water purification, it is recommended that cationic poly–electrolyte in combination with CaO are used as coagulant chemical at the Zuikerbosch Water Purification Plant. Turbidity is not a good indication of algal removal efficiency during jar testing experiments. If problems with high algal concentrations in the source water are experienced it is advisable to also determine the chlorophyll–665 concentrations of the supernatant water during the regular jar testing experiments, since it will give a better indication of algal removal. Chlorine exposure experiments were performed on water from Vaalkop Dam (M–RAW_VAALKOP) and Rietvlei Dam source water, to determine the possibility of implementing pre– or intermediate chlorination with the aim to render the cells immobile for more effective coagulation. The chlorine exposure experiments with Vaalkop Dam and Rietvlei Dam source water showed similar results. The chlorine concentration to be dosed as part of pre– or intermediate chlorination will differ for each type of source water as the chemical and biological composition of each water body are unique. When the effect of chlorine on the freshwater dinoflagellate C. hirundinella was investigated, it was found that the effective chlorine concentration where 50 % of Ceratium cells were rendered immobile (EC50) was approximately 1.16 mg/L for Vaalkop Dam source water. For the source water sampled from Rietvlei Dam, it was found that the EC50 was at approximately 0.87 mg/L. Results of analyses to determine the organic compounds in the water after chlorination revealed that an increase in chlorine concentration resulted in increase in total organic carbon concentration (TOC), as well as a slight increase in MIB and trihalomethanes (CHCl3). Pre– or intermediate chlorination seem to be an effective treatment option for the dinoflagellate C. hirundinella to be rendered immobile and thereby assisting in its coagulation process. The use of pre– or intermediate chlorination to effectively treat source waters containing high concentrations of C. hirundinella is a viable option to consider. However, the organic compounds in the water should be monitored and the EC50 value for each source water composition should be determined carefully as to restrict cell lysis and subsequent release of organic compounds into the water. / Thesis (M.Sc. (Environmental Science))--North-West University, Potchefstroom Campus, 2012.

Polymerní nanokompozity (PNCs) mají slibnou budoucnost jako lehké funkční materiály zpracovatelné aditivními výrobními technologiemi. Jejich rychlému rozšíření však brání silná závislost jejich užitných vlastností na prostorovém uspořádání nanočástic (NP). Schopnost řídit disperzi nanočástic je tak klíčovým předpokladem pro jejich uplatnění ve funkčních kompozitech. Tato práce zkoumá přípravu polymerních nanokompozitů v modelové sklotvorné polymerní matrici roztokovou metodou, technikou schopnou vytvářet prostorové uspořádání nanočástic řízené strukturními a kinetickými parametry přípravného procesu. Prezentované výsledky popisují rozdíly mezi změnami rheologického chování roztoku polystyrenu při oscilačním smyku s vysokou amplitudou (LAOS) vyvolanými nanočásticemi. Výsledky vedou k závěru, že vysoce-afinní OP-POSS nanočástice při nízkých koncentracích dobře interagují s PS a tvoří tuhé agregáty, zatímco nízko-afinní OM-POSS nanočástice za těchto podmínek neovlivňují deformační chování polymerních řetězců. Dále byla pozornost zaměřena na vliv použitého rozpouštědla na uspořádání nanočástic v SiO2/PMMA a SiO2/PS nanokompozitech, který je v literatuře prezentován jako parametr řídící prostorové uspořádání nanočástic v pevném stavu. Důraz byl kladen na kvalitativní rozdíly mezi „špatně dispergovanými“ shluky nanočástic, které byly na základě rheologie a strukturální analýzy (TEM, USAXS) identifikovány jako polymerními řetězci vázané nanočásticové klastry a dva typy agregátů, jeden termodynamického a druhý kinetického původu. Jednotlivé druhy agregátů se vyznačují odlišnými kinetikami vzniku a rozdílnými vlastnostmi jak mezi sebou, tak v porovnání s dispergovanými nanočásticemi. Pozorované typy disperze nanočástic byly kvantitativně posouzeny podle svých rheologických vlastností během roztokové přípravy, podle kterých byla vyhodnocena míra adsorpce polymeru na povrch nanočástic a atrakce ve vypuzeném objemu. Výsledky byly porovnány s teorií PRISM. Důležitost uspořádání nanočástic byla demonstrována na porovnání teplot skelných přechodů různých struktur při stejném chemickém složení.