Heavy metal ions, such as cadmium and lead, should be removed from wastewaters to prevent bioaccumulation. Among many other separation processes, one of the alternatives is ion exchange involving a low cost packing material, clinoptilolite. Clinoptilolite is a natural zeolite and contains exchangeable cations such as Na+, K+, Mg2+, and Ca2+ in its structure. Aim of this study is to determine binary and multicomponent ion exchange behaviors of sodium enriched form of G&ouml / rdes clinoptilolite for lead and cadmium ions. For this purpose, Pb+2 &ndash / Na+, Cd+2 &ndash / Na+ binary and Pb+2 &ndash / Cd+2 &ndash / Na+ ternary systems were investigated in column operations for concentrations between 0.005 to 0.02 N and flow rates between 5 to 20 mL/min at 25 &amp / #730 / C. For determination of optimum particle size, 5/6, 8/10, 14/18, 20/30, 35/60, and 70/140 ASTM E-11 standard mesh ranges were tested and the optimum particle size, under the experimental conditions was found as 35/60. Furthermore, although the clinoptilolite has a theoretical ion exchange capacity of 2.14 meq/g based on its aluminum content, under experimental conditions maximum exchange level was determined as 1.08 meq/g. For binary and ternary experiments, it is observed that the clinoptilolite has affinity for both Pb2+ and Cd2+ ions. However, clinoptilolite has greater affinity to Pb2+ than Cd2+ ion. Therefore, selectivity sequence was determined as Pb2+&gt / Cd2+&gt / Na+. Additionally, for column studies, flow rates less than 10 mL/min and influent concentrations up to 0.01 N, sodium enriched form of G&ouml / rdes clinoptilolite holds great potential to remove Pb2+ and Cd2+ ions from wastewaters.

Proton exchange membrane (PEM) fuel cell technology is promissing alternative solution to today&rsquo / s energy concerns providing clean environment and efficient system. Decreasing platinum (Pt) content of fuel cell is one of the main goals to reduce high costs of fuel cell technology in the way of commercialization. In this target, porous carbons provide an alternative solution as a support material for fuel cell electrocatalysts. It is also essential to increase surface area of carbon support material to have well dispersion of the Pt nanoparticles. The aim of this thesis is to synthesize mesoporous carbon supports named as hollow core mesoporous shell (HCMS) carbon and prepare their corresponding electrocatalysts with platinum impregnation method. HCMS carbon supports were synthesized by using two different carbon sources. As a first approach, phenol/paraformaldehyde couples were used and carbon source exhibited 1053 m 2 /g BET surface area and 1.046 nm BJH adsorption pore diameter. Second approach was to use divinylbenzene (DVB) as a carbon source with an initiator named as azo bis isobuytronitrile (AIBN) differing synthesis criteria. It is observed that using AIBN/DVB, pore sizes increased up to 3.44 nm. Platinum impregnation was conducted by microwave irradiation method using hydrogen hexachloroplatinate (IV) hydrate as a platinum precursor. The first achievement was to increase platinum loading up to 44 wt % on commercial Vulcan XC 72 by using ethylene glycol as a reducing agent. Using different reducing agents such as hydrazine, sodium borohydrate with a combination of ethylene glycol, platinum loading reached up to 34 wt % on HCMS carbon support. Accordingly, 34 wt %, 32 wt % and 28 wt % Pt/HCMS carbon supported electrodes preparation was achieved. The sizes of the platinum nanoparticles were calculated by XRD analysis as 4 nm, 4.2 nm and 4.5 nm for 28 wt %, 32 wt % and 34 wt % Pt/HCMS carbon supported electrodes respectively. Characterizations of catalysts were performed by ex situ (N 2 adsorption, TGA, SEM, TEM and Cyclic Voltammetry) and in situ (PEMFC tests) analysis.

Propylene oxide (PO) is an important raw material for the chemical industry, which is produced commercially by the chlorohydrin process and hydroperoxide process. However the deficiencies in these processes have given rise to considerable interest in the development of a direct route to PO that does not produce by-products or coproducts. The development of novel, active and selective catalysts for gas phase oxidation of propylene using molecular oxygen were studied via testing a large number of catalysts by high-throughput screening method over combinatorially prepared different catalytic system in this study. v The promoted and un-promoted silver (Ag), copper (Cu), manganese (Mn) mono and bimetallic catalytic system over high and low surface area silica, alumina, titanium oxide and titanium-silicate supports were prepared by single step sol-gel method and by incipient wetness method. The study to determine the most effective catalyst and promoter in the epoxidation reaction with different reaction conditions, showed that potassium (K)- promoted Cu metal supported over high surface area silica favored the PO production at a high reaction temperature (350 &deg / C) and oxygen rich atmosphere (C3H6/O2=1.0). The catalyst showed high and low propylene oxide productivity was investigated by some of the characterization techniques. The highlydispersed copper particle over silica support was determined by XRD, TEM and XPS techniques. The only change between promoted and un-promoted catalyst was found out in the temperature dependence of propylene consumption and PO production rate. It was inferred that potassium (K) only neutralizes the acid sites of silica.

A comprehensive model, previously developed for a rectangular parallelepiped shaped 0.3 MWt circulating fluidized bed combustor (CFBC) fired with high calorific value coal burning in sand and validated against experimental data is adapted to cylindrical configuration and is extended to incorporate NOx formation and reduction reactions and pressure drops around cyclone, downcomer and loop seal. Its predictive accuracy is tested by applying it to the simulation of Middle East Technical University (METU) 150 kWt CFBC burning low calorific value indigenous lignite with high Volatile Matter/Fixed Carbon (VM/FC) ratio in its own ash and comparing its predictions with measurements. Favorable comparisons are obtained between the predicted and measured temperatures, pressure profiles and emissions of gaseous species. Results reveal that predictive accuracy in pressure profile strongly depends on the correlation utilized for entrainment in dilute zone and that accuracy in NO emission requires data on partitioning of coal nitrogen into char-N and volatile-N and is affected significantly by dilute zone oxygen content.

Wastewaters resulted from anthropogenic influence can encompass a wide range of potential contaminants and concentrations. There are numerous procedures that can be used to clear out wastewaters depending on the type and extent of contamination, however / disposal of pollutants from wastewaters in industrial scale is a difficult and costly problem. In this study, the use of ion exchange theory utilizing natural Turkish clinoptilolite zeolite from G&ouml / rdes-Manisa as ion exchange resins in down-flow column mode is investigated. The clinoptilolite with particle size range of 0.25-0.50 mm is used in the removal of lead Pb2+ and ammonium NH4+ ions from aqueous solutions. The aim of the study is to set up the conditions under which clinoptilolite may be used in an economical and efficient approach in the removal process. Experiments were divided into two sets: binary studies, and ternary studies, and the effects of conditioning clinoptilolite with NaCl solution, flow rate, and initial concentration of the solutions on the removal behavior were investigated. In binary studies, results showed that increasing the loading volumetric flow rate resulted in decreasing the breakthrough capacity and the column efficiency, while the total capacity remained constant. The maximum total capacity was determined as 1.16 meq/g of zeolite for NH4+, and 1.1 meq/g of zeolite for Pb2+ and these values were close to each other and to the sodium content of Na-form of pretreated clinoptilolite (1.16 meq/g of zeolite). In addition, by decreasing the initial contaminant concentration, an increase in breakthrough capacity and column efficiency was observed. In ternary studies, the results showed that the removal of Pb2+ and NH4+ ions are dependent on the flow rate, in which at moderately low flow rate, a higher ion exchange capacity is yielded. That was explained as at higher flow rates, the retention time was insufficient for the ion exchange process to take place completely between clinoptilolite and lead and ammonium ions. Thus, a competition between Pb2+ and NH4+ ions for the exchange sites on clinoptilolite was observed and this competition was in favor of lead ions. Consequently, it was observed that the clinoptilolite zeolite has affinity for both Pb2+ and NH4+ ions. However, the affinity of clinoptilolite for lead ions is higher than that for ammonium ions. Therefore, the cations selectivity for clinoptilolite according to their affinity is determined as the following sequence: NH4+ &gt / Pb2+ &gt / Na+.

Plastic materials are widely used throughout the world due to their low prices and easy processing methods. A serious problem of environmental pollution is brought with the widespread use of these materials due to their non-biodegradabilty. For this reason, plastic materials are degraded into lower molecular weight liquid and gaseous products which are potential raw materials and fuels for petrochemical industry. The use of catalysts enhances the formation of more valuable hydrocarbons at lower reaction temperatures and residence times. In this study, aluminum containing MCM-41 and tungstophosphoric acid (TPA) loaded SBA-15 materials were synthesized by impregnation of Al and TPA into hydrothermally synthesized MCM-41 and SBA-15, respectively to be used in catalytic degradation of polyethylene. Al was incorporated into MCM-41 framework with different Al/Si ratios using aluminum triisopropylate as the aluminum source and TPA was incorporated to the porous framework of SBA-15 with different W/Si ratios, using tungstophosphoric acid hydrate as the acid source. From XRD analysis, it was observed that introducing acidic compounds did not cause deformations in the regularity and by EDS analysis, it was found out that at lower loadings, acidic compounds were introduced more effectively for MCM-41 materials. Nitrogen adsorption-desorption isotherms showed that the synthesized materials exhibited type IV isotherms. SEM and TEM pictures showed the hexagonal regularly ordered structure of SBA-15 and MCM-41 materials. FTIR analysis of the pyridine adsorbed synthesized materials revealed the existence of Lewis and Br&oslash / nsted acid sites in the synthesized materials. From TGA analysis it was observed that aluminum impregnated MCM-41 samples reduced the temperature of the degradation reaction significantly and TPA loaded SBA-15 samples reduced activation energy of the reaction effectively. In the degradation reaction system, non-catalytic and catalytic degradation experiments of polyethylene were performed. In non-catalytic degradation and catalytic degradation reactions carried out using aluminum containing MCM-41 materials, selectivity of C3 and C4 hydrocarbon gases was high and in catalytic degradation reactions carried out using TPA impregnated SBA-15 materials, selectivity of ethylene was high. In the liquid analysis of non-catalytic degradation reactions, it was observed that the product distribution was mainly composed of hydrocarbons greater than C18. The use of aluminum loaded MCM-41 and TPA loaded SBA-15 materials resulted in a liquid product distribution in the range of C5-C14, which is the hydrocarbon range of gasoline fuel.

Textile wastewaters are highly colored and non-biodegradable having variable compositions of colored dyes, surfactants and toxic chemicals. Recently, ozonation is considered as an effective method that can be used in the treatment of industrial wastewaters / catalytic ozonation being one of the advanced oxidation processes (AOPs), is applied in order to reduce the ozone consumption and to increase the chemical oxygen demand (COD) and total organic carbon (TOC) removals. In this study, catalytic ozonation of industrial textile wastewater (ITWW) obtained from AKSA A.S. (Yalova, Istanbul) textile plant has been examined in a three phase fluidized bed reactor at different conditions. The effects of inlet chemical oxygen demand concentration (CODin), pH, different catalyst types [perflorooctyl alumina (PFOA) and alumina] and catalyst dosage on ozonation process were determined. Moreover, the changes in the organic removal efficiencies with gas to liquid flow rate ratio were investigated. The dispersion coefficients (DL) and volumetric ozone-water mass transfer coefficients (kLa) were estimated at various gas and liquid flow rates in order to observe the effect of liquid mixing in the reactor on ozonation process. It was observed that increasing both gas and liquid flow rates by keeping their ratio constant provided higher organic removal efficiencies due to the higher mixing in the liquid phase. The dyes present in ITWW sample were known to be Basic Blue 41 (BB 41), Basic Red 18.1 (BR 18.1) and Basic Yellow 28 (BY 28). The &ldquo / absorbance vs. concentration&rdquo / calibration correlations were developed to estimate the amounts of these colored dyes in the ITWW sample. This provided the opportunity to examine the degradation of each dye in this wastewater separately. While PFOA catalyst was found to increase the removal efficiency of BY 28 at an acidic pH of 4, alumina yielded highest color removals for BB 41 and BR 18.1 at a pH of 12. The highest TOC and COD reductions being 24.4% and 29.5%, respectively, were achieved in the catalytic ozonation of the ITWW using alumina as the catalyst at a pH of 12 and at a gas to liquid flow rate ratio of 1.36 (QG = 340 L/h, QL = 250 L/h). At the same conditions, also the highest overall color removal in terms of Pt-Co color unit, namely 86.49%, were obtained due to the lower BY 28 concentration in the WW sample than those of the BB 41 and BR 18.1. In addition, the oxidation of BB 41, BR 18.1 and BY 28 dyes were investigated in a semi-batch reactor by sole and catalytic ozonations with alumina and PFOA catalyst particles. The sole and catalytic ozonation reactions followed a pseudo-first order kinetics with respect to dye concentration. The highest TOC and COD removals being 58.3% and 62.9%, respectively, were obtained at pH of 10 for BB 41 and 55.2% and 58.8%, respectively, for BR 18.1 with alumina catalyst. On the other hand, for BY 28 PFOA catalyst yielded highest TOC and COD reductions being 61.3% and 66.9%, respectively, at pH of 4.

Despite their limited commercial applications, chemical heat pumps (CHP) have been considered as an important alternative to conventional heating and cooling technologies. In this study, the adsorption-desorption of ethanol over activated carbon was applied on the CHP reactor. The ethanol vapor - activated carbon adsorption rate was determined at 30, 60, 90 and 120&deg / experimentally by using Intelligent Gravimetric Analyzer C(IGA). The experimental adsorption data were used on the transient modeling of reactor by assuming single component gas phase. Then, spatial and temporal temperature, rate of heat transfer, and total amount of heat transferred for a given period were determined. Finally, the calculated adsorption and temperature profiles were integrated over volume to predict performance of heat pump for different reactor geometries. The results showed that, with proper modeling satisfactory performance values can be attained using these systems.

Fuel cells are the tools which convert chemical energy into electricity directly by the effective utilization of hydrogen and oxygen (or air). One of the most important barriers for the fuel cell commercialization is the durability of the fuel cell components in the long term operations. In this study, the durability of the PEM fuel cell electrocatalysts were investigated via cyclic voltammetry (CV) and rotating disk electrode (RDE) experiments in order to determine the hydrogen oxidation reaction (HOR) and oxygen reduction reaction (ORR) which corresponds to the half cell reactions in the fuel cell. PEM fuel cell electrodes mainly composed of carbon supported Pt catalysts. In long term operations due to Pt dissolution and carbon corrosion some properties of the electrocatalysts can be changed. Performance losses in catalysts mainly depend on / i) decrease in the total metal surface area (SA) and the electrochemically active surface area (ESA) due to the increase in the particle size ii) decrease in the tafel slope potential in ORR and iii) increase in carbon corrosion. In this study, these properties were examined via accelerated degradation tests performed in CV and RDE. The catalysts having different Pt loadings, synthesized with different ink compositions, pH values and microwave durations were investigated. The commercial catalysts having Pt loadings of 20, 50 and 70 (wt %) were tried and best results were obtained for Pt/V (50 wt %) catalyst. Different carbon to Nafion&reg / ratios of 4, 8, 12 in the ink composition were tried. C/N ratio of 8 gave the best result in Pt dissolution and carbon corrosion degradation tests. The catalysts prepared at different pH values of 1.4, 6.25 and 10 were tried and the catalyst prepared at pH of 10 was less degraded in Pt dissolution test and the catalyst prepared at pH of 6.25 showed better resistance to carbon corrosion. Catalysts prepared under different microwave durations of 50, 60 and 120 s were tried and the catalyst prepared at 60 s gave the best performances.

Membrane based separation techniques have been widely used and developed over decades. Generally polymeric membranes are used in membrane based gas separation / however their gas separation performances are not sufficient enough for industrial feasibility. On the other hand inorganic membranes have good separation performance but they have processing difficulties. As a consequence mixed matrix membranes (MMMs) which comprise of inorganic particles dispersed in organic matrices are developed. Moreover, to enhance the interaction between polymer and zeolite particles ternary mixed matrix membranes are introduced by using low molecular weight additives as third component and promising results were obtained at 35 &deg / C. Better understanding on gas transport mechanism of these membranes could be achieved by studying the effect of preparation and operating parameters. This study investigates the effect of operation temperature and annealing time and temperature on gas separation performance of MMMs. The membranes used in this study consist of glassy polyethersulfone (PES) polymer, SAPO-34 particles and 2- v hidroxy 5-methyl aniline (HMA) as compatibilizer. The membranes fabricated in previous study were used and some membranes were used as synthesized while post annealing (at 120&deg / C, 0.2atm, N2 atm, 7-30 days) applied to some membranes before they are tested. The temperature dependent gas transport properties of the membranes were characterized by single gas permeation measurements of H2, CO2, and CH4 gases between 35 &deg / C-120 &deg / C. The membranes also characterized by scanning electron microscopy (SEM), thermal gravimetric analysis (TGA) and differential scanning calorimetry (DSC). Annealing time and temperature affected the reproducibility and stability of the mixed matrix membranes and by applying post annealing step to mixed matrix membranes at higher temperatures and longer times, more stable membranes were obtained. For pure PES membranes thermally stable performances were obtained without any need of extra treatment. The permeabilities of all studied gases increased with increasing operation temperature. Also the selectivities of H2/CO2 were increased while CO2/CH4, H2/CH4 selectivities were decreased with temperature. The best separation performance belongs to PES/SAPO-34/HMA mixed matrix membrane at each temperature. When the temperature increased from 35 &deg / C to 120 &deg / C H2/CO2 selectivity for PES/SAPO- 34/HMA membrane was increased from 3.2 to 4.6 and H2 permeability increased from 8 Barrer to 26.50 Barrer. This results show that for H2/CO2 separation working at higher temperatures will be more advantageous. The activation energies were found in the order of / CH4 &gt / H2&gt / CO2 for all types of membranes. Activation energies were in the same order of magnitude for all membranes but the PES/SAPO-34 membrane activation energies were slightly lower than PES membrane. Furthermore, PES/SAPO-34/HMA membrane has activation energies higher than PES/SAPO-34 membrane and is very close to pure membrane which shows that HMA acts as a compatibilizer between two phases.