Zeolites are crystalline, hydrated aluminosilicate minerals that are characterized by their ability to exchange some of their constituent cations with cations in aqueous solutions, without a major change in their crystalline structure. Clinoptilolite is the most abundant ype of zeolite and it has received extensive attention due to its favorable selectivity for mmonium and certain heavy metal cations. The aim of this study is to investigate the binary and ternary (multicomponent) ion xchange behavior of sodium form of G&ouml / rdes type clinoptilolite for ammonium,cadmium and sodium ions. For this purpose, NH4 +-Na+,Cd2+-Na+ binary systems and NH4 +-Cd2+-Na+ multicomponent system were investigated both in batch and column systems at 0.1 and 0.01 constant total normality respectively and at 250C constant temperature. As a result of binary and ternary experiments, clinoptilolite&rsquo / s affinity for both ions but greater affinity to NH4+ ion than Cd2+ ion was observed and the selectivity sequence of G&ouml / rdes clinoptilolite was determined as NH4+&gt / Cd2+&gt / Na+ in binary and multicomponent batch and column operations. Additionally, total ion exchange capacities and maximum exchange levels of G&ouml / rdes clinoptilolite for both ions were determined in batch systems whereas breakthrough capacities and column efficiencies (for three different flow rates) were determined in column systems. Finally, it was concluded that the increase of the flow rate reduced the breakthrough capacities and column efficiencies of G&ouml / rdes clinoptilolite for ammonium and cadmium ions in multicomponent column systems involving more than one cation.

Photobiological hydrogen production from organic acids occurs in the presence of light and under anaerobic conditions. Stable and optimized operation of the photobioreactors is the most challenging task in the photofermentation process. The main aim of this study was to achieve in long term, a stable and high hydrogen production on acetate, using the photosynthetic bacteria Rhodobacter capsulatus in continuous panel photobioreactors. Rhodobacter capsulatus (DSM 1710), heat adapted Rhodobacter capsulatus (DSM 1710) and Rhodobacter capsulatus YO3 (Hup-), a mutant strain, were tested in outdoor conditions, under natural sunlight between September-December, 2008 in Ankara, Turkey. Defined culture medium containing acetate (40 mM) and glutamate (2 mM) and a dilution rate of 0.8 l/ day were used. Steady hydrogen production (0.4 mmol H2/lc.h) was obtained using the Rhodobacter capsulatus YO3 (Hup-) mutant strain that was continuously operated for 69 days, but the cell concentration could not be kept at a steady value. Further efforts were focused on achieving stable biomass concentration by optimizing the feed composition. Stable biomass (0.40 gdcw/lc) and high hydrogen productivity (0.8 mmol H2/lc.h) were achieved using feed media containing 40 mM acetate and 4 mM glutamate with a 10% (v/v) feed rate. Moreover, the EU project HYVOLUTION aims to combine dark fermentation and photofermentation process for the conversion of biomass to hydrogen. Effluents from the dark fementation contain high amount of ammonium, which inhibits phototrophic hydrogen production. After treatment it has been concluded that G&ouml / rdes clinoptilolite zeolite effectively removes ammonium ion from the dark fermenter effluent of molasses.

Clinoptilolite is a natural zeolite which can be used favorably in heavy metal removal. The main mechanisms for metal removal via clinoptilolite are adsorption and ion exchange. Several sources propose to keep the normality constant to obtain equilibrium isotherms for ion exchange systems, while many studies use constant sorbent mass with varying normalities of the sorbate. The objective of this study is to investigate the prevailing mechanisms of clinoptilolite during cadmium removal and the impact of the methodology for obtaining equilibrium isotherms. Batch Cd2+ removal experiments were conducted by using the two different methodologies (i.e. keeping the sorbent mass constant vs. keeping the normality constant) with clinoptilolite in as-received (AsC) and conditioned form (CnC), an ion exchange resin and granulated activated carbon. Exchangeable and framework cations, conductivity and pH were monitored during experiments. The equilibrium results were then fitted to isotherm models. The prevailing mechanisms for Cd2+ removal with clinoptilolite are discussed considering all monitored parameters and isotherm model fits. Use of the methodology was seen to have an effect on the overall Cd2+-clinoptilolite interaction. For example, differences between methodologies are observed regarding maximum sorbed Cd2+ and the distribution of exchangeable cations. Conductivity profiles provided a good indication of presence of ion exchange and demonstrated that it is more dominating for CnC than for AsC. The Cd2+ removal capacities observed in this study (0.65 meq/g for AsC and 1.46 meq/g for CnC) are the highest recorded for a clinoptilolite sample, as can be found in the literature.

Thesis (Master)--İzmir Institute of Technology,İzmir, 2005 / Includes bibliographical references (leaves. 84).

This thesis explains a method based on the homogenisation of zeta potential charges on carbon supports for the production of hierarchical structured zeolitic composites. The modification of carbons’ surface chemistry allowed zeolite particles to be fixed to the support by electrostatic interactions. In order to achieve this, the size reduction of zeolite particles was carried out by two different methods: a) ball milling and b) a synthetic route to produce zeolite colloidal dispersions. Also, the seeding method, based on hydrothermal growth was compared. The prepared materials in this work were designed to be used in the sorption of cations, and to allow vitrification and thereby reduce the final adsorbent volume. Results showed that a large pollutant amount can be trapped using a lower volume of material reducing costs and final waste disposal. The zeolites used in this work were selected based on their low density framework and low Si/Al ratio. Synthetic zeolites A, Y and clinoptilolite were successfully produced. Natural clinoptilolite was also utilised in this work. Also, zeolite A was produced at nanometre scale following the clear solutions method. All materials were successfully incorporated onto supports to produce multimodal porosity materials. The hierarchical modification of natural clinoptilolite, following a straightforward and nonexpensive methodology, is one the most significant contributions of this work. Carbons are used as supports due to their high surface area, they can be obtained from low-cost sources such as agroindustrial wastes and carbons allow volume reduction if materials are vitrified at high temperatures. In this work, carbons were produced from corn cob and husk, sugar cane bagasse, cherry stones, date stones and hazelnut shells. The prepared composite materials were tested in the removal of toxic ions from water solutions: cobalt, copper and caesium ions were effectively removed from aqueous media. Adsorption experiments showed that the distribution of supported zeolite particles improved their uptake efficiency and capacity. The kinetic studies revealed an enhanced rate constant for carbon-zeolites composites in comparison with pure zeolites. Diffusivity results suggested that mass transfer characteristics are modified by using hierarchical porous materials; results showed that particle size or support nature can modify diffusion resistances, reducing intraparticle diffusion and accelerating the overall kinetic processes. Adsorption equilibrium data was correlated using Langmuir and Freundlich models.

Le travail de la thèse présente une série de (bio)capteurs conductimétriques, à base de la clinoptilolite, pour la détermination de l’ammonium, de l’urée et de la L-arginine. La clinoptilolite, le matériau nanométrique, possédant des propriétés de la sorption intrinsèque et une capacité d’échange cationique vis-à-vis des espèces ammonium, a été d’abord utilisée pour la réalisation d’un microcapteur conductimétrique sélectif à NH4+. Ci-après, une application de ce nanomatériau dans les biocapteurs est favorable pour le fonctionnement dans les solutions tampons multicomposants. Parmi plusieurs variantes de biocapteurs à l’urée à base de la zéolite, la plus intéressante est le biocapteur, dans lequel la couche de la clinoptilolite, déposée sur le transducteur, a été recouverte par le dépôt de la couche de l’uréase et de la zéolite. Pour l’élaboration d’un biocapteur conductimétrique hautement sensible pour la détermination de la L-arginine, l’arginase et l’uréase ont été co-réticulées sur le transducteur. Une détermination quantitative de la L-arginine dans une solution buvable « Arginine Veyron » a montré un fort accord avec les données fournies par le producteur. Une procédure détaillée de l’optimisation du biocapteur conductimétrique pour la détection de la L-arginine dans le sérum bovin a été proposée. La clinoptilolite a été également appliquée comme un modificateur dans la co-immobilisation de l’arginase et l’uréase pour améliorer les caractéristiques analytiques de biocapteur conductimétriques pour la détermination de la L-arginine / Currentwork presents a serie of conductometric (bio)sensors based on clinoptilolite, for ammonium, urea and L-arginine determination. Clinoptilolite, a nanoscale material possessing exceptional sorption and cation-exchange properties toward ammonium species, was initially used for the development of NH4+-selective conductometric microsensor. The clinoptilolite-based microsensor was selective toward ammonium in the presence of interferences that are commonly found along with ammonium in natural waters. Hereafter, an application of this nanomaterial in biosensors is favorable for operation in multicomponent buffer solutions. Among the several variants of the urea biosensors based on zeolite, considerably better characteristics were obtained for the biosensor comprising a clinoptilolite adlayer and an upper layer of immobilized urease and zeolite. In the work, for first time was developed a highly sensitive conductometric biosensor for L-arginine determination based on arginase and urease co-immobilized in a single membrane. The results of a quantitative determination of L-arginine in a drinkable solution “Arginine Veyron”, obtained by the biosensor, were in high correlation with the data provided by the producer. The L-arginine conductometric biosensor was optimized for the serum analysis. Clinoptilolite was also applied as a modifier in co-immobilization of arginase and urease for the improvement of analytical characteristics of the conductometric biosensor for L-arginine determination

Potentially harmful elements (PHEs) have been researched in a wide variety of disciplines, including pedology, chemistry, pollution science and medicine. Within the scientific community, emphasis has usually been placed on the toxic elements, such as cadmium, chromium, lead and arsenic, but rarely has there been consideration of interactions between PHEs, the sediment matrix and processes occurring in the sediments. Dredging of canals is needed for navigability purposes and consequently testing of dredged sediments (to assess whether sediments are hazardous) and landfilling can be costly for British Waterways facing constantly changing regulations and reduction in government grants. PHE mobility and availability in canal sediments can be affected by oxygen availability, pH and Redox. Remediation is thus becoming a priority for British Waterways to limit their operational costs. Zeolites, a type of remediation tool, have been widely studied in the past 30 years due to their attractive properties, such as molecular-sieving, high cation exchange capacities and their affinity for PHEs. The pilot study to investigate the efficiency of the clinoptilolite showed that there was a concentration difference between PHEs adsorbed by the clinoptilolite and the PHE concentration lost from the sediments from three sites in the West Midlands. Thorough characterisation of the sediments was needed to understand the speciation of the PHEs and the secondary processes occurring in the sediments. The different components of the sediments were analysed using various analytical methods, such as X-Ray Fluorescence spectroscopy (XRF), particle size and X-ray Diffraction (XRD) for the solid-inorganic phase, Ion Chromatography (IC) and Inductively Coupled Plasma-Optical Emissions Spectroscopy (ICP-OES) for the liquid phase (pore water), Gas Chromatography-Mass Spectrometry (GC-MS) and organic loss on ignition for the organic phase, pH and Redox for the electrochemistry of the sediments and Scanning Electron Microscope with Energy Dispersive X-Ray analysis (SEM-EDX) for microscopy and imaging. The British Geological Survey (BGS) sequential extraction method was used to investigate the different phases in the sediments. pH remained near neutral for all three sites and Redox remained anoxic. Organic contents for all three sites were around 30% and contained most of the polycyclic aromatic hydrocarbons considered hazardous. Pore water showed only high concentrations of sulphates but low concentrations of PHEs, suggesting PHEs were not mobile. Sequential extraction confirmed the other results showing that PHEs were mainly associated with stable phases, such as iron and manganese oxides or sulphides. The results have been taken into consideration to design a new remediation strategy to maximise efficiency of the zeolite.

This work examined the effects of thermal and chemical treatments on zeolite reactivity and determined the zeolite properties governing the development of compressive strengths and pozzolanic reactivity. Zeolites are naturally occurring aluminosilicate minerals found abundantly around the world. Incorporation of zeolites in cement mixtures has been shown by past research to increase concrete’s compressive strength and durability. In addition, use of zeolites as SCMs can decrease the environmental impact and energy demands associated with cement production for reinforced concrete structures. Further, in contrast to man-made SCMs such as fly ash, zeolite minerals provide a reliable and readily available SCM source, not affected by the production limits and regulations of unrelated industries such as the coal power industry. In this work, six sources of naturally occurring clinoptilolite zeolite were examined. The zeolites were first characterized using x-ray fluorescence, quantitative xray diffraction, thermal analysis, particle size analysis, pore size distribution and surface area analysis, and scanning electron microscopy. Cation exchange capacity was also tested for one of the zeolites. Following comprehensive material characterization, the six pozzolanic reactivity of the natural zeolites was determined by measuring the quantity of calcium hydroxide in paste after 28 or 90 days, by measuring calcium hydroxide consumption of the zeolite in solution and by tracking the development of strengths of zeolite-cement mortars. Pretreatments that attempted to increase the reactivity of the zeolites, including calcination, acid treatment, milling and cation exchange, were then tested and evaluated using the same methods of material characterization and testing mentioned previously. Last, the results of the reactivity testing were reanalyzed to determine which properties of natural zeolites, including particle size, nitrogen-available surface area, and composition, govern the development of compressive strengths, pozzolanic reactivity and improved cement hydration parameters of pastes and mortars using natural zeolites as SCMs. Pretreatment testing showed that milling and acid treatment successfully increased the reactivity of zeolites used as SCMs. Additionally, particle size was shown to be the dominant property in determining the development of compressive strengths while particle size and surface area of the zeolites contributed to zeolite pozzolanic reactivity. / text

M.Sc. / In this study, natural and modified clinoptilolite (CLI) reinforced polypropylene (PP) composites possessing improved mechanical and adsorptive properties were prepared through melt-mixing. Determination of morphological, structural and thermal properties was achieved by means of different techniques (FTIR, TGA, DSC, electron microscopy and x-ray spectroscopy). Electron microscopy revealed that increasing filler loading beyond 20% leads to agglomeration of clinoptilolite particles reducing their dispersion within the matrix. Thermal studies showed that the reinforced composites had a lower thermal stability than the neat PP polymer, suggesting that the clinoptilolite interfered with polymer chain arrangement and bonding. It also showed that percentage crystallinity increased with increasing filler loading indicating that the filler particles acted as nucleating agents within the polymeric matrix during composite synthesis. Prior to the ion-exchange studies, water sorption behaviour of fabricated composites was evaluated because ion-exchange/adsorption studies were to be performed in aqueous media. It was therefore observed that the hydrophobic polymer, PP attained the property of water sorption mainly due to the porous structure of the composites created by mixing and extrusion and also by the addition of the hydrophilic filler material.

Student Number : 9400913V - MSc (Eng) dissertation - School of Chemical and Metallurgical Engineering - Faculty of Engineering and the Built Environment / Natural zeolites are finding applicability in a broad range of industrial processes. This study assesses the potential applications of a South African natural zeolite, Clinoptilolite, and develops a methodology to quickly screen and assess these applications. Zeolites are known to have ion exchange and adsorption properties. Wastewater treatment has been identified as a potentially important opportunity in South Africa, since South Africa - and particularly Gauteng - is a water scarce region. The wastewater treatment industry in this region can be divided into two main categories of effluent: namely chemicals from coal and the metal recovery and finishing related to the mining industry. The focus of this work was to find a method to screen for potential uses of Clinoptilolite in these industries. The major effluent treatment issue in respect of the effluents from coal-based processes was identified to be the removal of oxygenate organics that are highly soluble in water, such as ethanol and acetone. This problem cannot be solved using vapour-liquid equilibrium based processes due to high energy costs, and liquid-liquid equilibrium based processes inherently introduce new contaminants into the wastewater. We therefore screened the zeolite for application in the removal of soluble organics via adsorption. The zeolite was found to be unsuitable for the adsorption of acetone and ethanol due to the preferential adsorption of water. As a result we tested the potential of the zeolite as a drying agent for ethanol and acetone. It was found that this zeolite could find application in the dehydration of ethanol, but not acetone. In effluent from the mining and metals based industries, heavy metals frequently occur and are usually toxic, such as lead, zinc and nickel. Such contaminated water must be disposed of as toxic waste, and this is very costly. Thus being able to selectively remove these metals allows for the possible recovery and recycling of a potentially valuable metal. If no application can be found for the recovered metal, the loaded zeolite would need to be disposed of as toxic waste, but the volume of this waste is significantly smaller than that of the original effluent due to the concentration effect of ion exchange processes. All of the metals were ion exchanged onto the zeolite successfully. The zeolite exhibited exceptional selectivity for the removal of lead, and reduced the concentration of lead in the water to levels below detection by Atomic Adsorption. The selectivity for the uptake of the metals in decreasing order was lead, zinc and lastly nickel. Therefore, provided the zeolite can be regenerated, it could be used for effluent treatment in mining activities that have traces of lead in the ore body, such as zinc and silver deposits, and in the battery industry. As a result of the work presented in this dissertation, a further project was undertaken to investigate the regeneration of the zeolite. Preliminary findings indicate that although it can be regenerated, the zeolite capacity decreases with each successive regeneration cycle. More work is required on regeneration to improve the lifespan of the zeolite.