Sürdürülebilir Yeşil Kampüs Koleksiyonu / Sustainable Green Campus Collection
Permanent URI for this collectionhttps://hdl.handle.net/11147/7755
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Master Thesis An Investigation of Dye-Surfactant Intetactions in Aqueous Solutions for Elucidating the Mechanisms of Ultrafiltration(Izmir Institute of Technology, 2014) Olcay, Aybike Nil; Polat, Mehmet; Polat, HürriyetLow Molecular Weight Contaminants (LMWCs) in waters are serious environmental concern due to removal problems with classical techniques such as chemical coagulation, biological treatments and adsorption. LMWCs are usually copresent with surface active agents in contaminated waters. Though such advanced removal techniques as ultrafiltration and micelle enhanced ultrafiltration are said to perform better, no systematic study is present for elucidating how the contaminantsurfactants interactions affect removal efficiency. In this study, methylene blue (MB), a dye widely employed in textile, paper and chemical industries, was chosen as the model contaminant. Surfactants selected were anionic sodium dodecyl sulfate (SDS), cationic hexadecyltrimethyl ammonium bromide (CTAB) and non-ionic ethoxylated octylphenol (TX-100). Surface tension, size, charge and contact angle measurements were conducted to investigate dye-surfactant interactions. Cellulose nitrate filters were employed to determine the effect of these interactions in filtration efficiency. It was found that significant amount of MB was removed from solution since it attached on the negatively charged cellulose nitrate filter. Though presence of surfactants generally decreased MB removal efficiency, MB-SDS interaction created large-loose aggregates at low SDS concentrations which cannot pass the filter paper. The MB-CTAB/TX-100 interactions created positively charged MB-surfactant pairs which can attach to the filter surface causing a decrease in the removal. At concentrations above Critical Micelle Concentration (CMC), the efficiency of MB removal is low due to the formation of surfactant-micelles that are smaller than the pores of the filter. Detailed size distribution experiments suggest that MB molecules are within the micelles structure, not in the core as believed in literature and do not increase the size of the micelle.Doctoral Thesis Estimation of the Surface Charge Distribution of Solids in Liquids by Using Atomic Force Microscopy(Izmir Institute of Technology, 2011) Yelken Özek, Gülnihal; Polat, MehmetColloidal systems are widely encountered in minerals, ceramics, environment, biology, pharmaceuticals and cosmetics industries. These systems consist of micronsized particulates dispersed in a solvent. Homogeneity, dispersibility, stability of colloidal systems determines the economy and success of the final product in these applications. Control and manipulation of these properties depend on detailed analysis of the interactions among the particles. Electrophoretic potential measurements or colloidal titration methods are widely employed to characterize the charging of colloidal systems. However these methods only yield average charging information, not the charge distribution on the surface. Atomic Force Microscope (AFM) allows topographic surface analysis at nanometer level resolutions. Though it is widely used to obtain derived information AFM directly measures the forces between the tip and the surface atoms. The objective of the present work is to assess the applicability of AFM to surface charge mapping, i.e., the detection of positive or negative charged regions on metal oxide surfaces. Hence, well defined tips were prepared and allowed to interact with well defined oxide surfaces under different pH conditions. The influence of solution ion concentration and pH on the forces measured was also investigated. These measured force-distance curves were analyzed using a new solution of the one dimensional Poisson-Boltzmann equation to isolate the electrical double layer force, hence the surface charge on each measurement point. The new solution in question provides analytical expressions for all charging conditions which are amenable to such analysis.Repetitive force measurements on a predefined grid on the solid surface ultimately yield the charge distribution of the surface. Such an analysis procedure is new and advances the charge measurements on solids in solution to a new level.Doctoral Thesis Fixation and Stabilization of Heavy Metals in a Product Composed of Fly Ash and Industrial Acidic Wastes(Izmir Institute of Technology, 2010) Üzelyalçın Ülkü, Berna; Polat, MehmetLarge quantities of fly ash are produced in the world while only a very small portion of it finds utilization as a product. Since even larger quantities of fly ash should be expected to be generated in an increasingly energy-hungry world, finding new, smart pathways towards fly ash utilization carries its own weight in achieving sustainable development. Manufacturing light-weight fly ash aggregates which could also be used as sinks for other wastes with acceptable environmental foot-print and possible added value is exactly one such pathway. This thesis comprises of the studies where a fly ash sample from a large Thermal Power Plant (Soma fly ash) is used to stabilize an extremely acidic industrial waste in an aggregate structure with the aim that the aggregates produced had acceptable environmental impact and possible product value. The study is divided into several parts. Initial chapters contain the characterization studies of both the fly ash from Soma, Manisa Thermal Power Plant and the highly acidic industrial waste from a metal stripping factory in Cigli-Izmir. Later chapters contain the methodology and the experimental parts of the work. The acidity of the aggregates was also optimized keeping in mind the present environmental regulations. Solid/liquid ratio, effect of aging of the aggregates, effect of leaching from the aggregates and their mechanical strengths were the main experimental parameters investigated. Mineralogical composition of the aggregates was compared with the raw fly ash to shed light on the fixation mechanism. The fly ash was rich in especially Si, Al and Ca and some heavy metals in trace amounts whereas the acidic waste contained huge amounts of Zn, Fe and other heavy metals. This study demonstrated conclusively that the acidic waste was not only neutralized by the fly ash to disposable levels, but also that the leaching of both the major and minor elements from the aggregate body into the water was below the environmental limits in force both in Europe and Turkey today. The produced aggregates were also observed to possess the low-strength-material properties which open the possibility for their utilization in construction applications.