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Hazelnut shell, apricot stone, grapeseed and chestnut shell samples were carbonized in a thermogravimetric (TG) analyzer at different conditions to determine the carbonization kinetic parameters. Three different calculation methods and 22 different model equations concerning solid-state rate controlling mechanisms were used for the kinetic analysis of the carbonization TG curves. A computer program in BASIC which enables regression analysis, was used to calculate the kinetic parameters from experimental TG data. It was observed that the different values of Arrhenius parameters (E and Log A) were obtained depending on the method of calculation, the gaseous atmosphere and the sample properties. The most appropriate kinetic model which represents the carbonization of the cellulosic and lignin ingredients of the biomass samples were found as f(α)=(1−α)2 and f(α)=0.5·(1−α)·[−ln(1−α)]−1, respectively.

In this study, two different models of photopolymerization of multifunctional monomers are developed. The first is a kinetic model and is based on first order nonlinear ordinary differential equations describing the rates of photoinitiator, monomer, and live and dead radicals of different chain lengths. In the second model, a stochastic Monte Carlo approach is used to predict the time evolution of the photopolymerization process. In this model the chain affects are incorporated both in the propagation and termination rate constants. The simulations of these models for the predictions of gelation times are compared with the experimental values measured in the absence of oxygen in the reaction volume by using passive microrheology technique. The nonlinear decrease of gelation time with increasing photoinitator concentration and number of acrylate fragments on each monomer is best captured with the second model. Furthermore, the second model is successfully verified with kinetic data generated from FTIR and DSC experiments. POLYM. ENG. SCI., 54:1737–1746, 2014. © 2013 Society of Plastics Engineers

In this study, the effect of photoinitiator concentration on the gelation time of different resins were studied in the absence of oxygen in the reaction volume by using passive microrheology technique. Four different monomers which are ethoxylated pentaerythritol tetraacrylate (SR494), trimethylolpropane triacrylate (SR351), Methylene glycol diacrylate (SR272), and 2(2-ethoxyetoxy) ethyl acrylate (SR256) were used in these experiments. Resins were prepared from these four different monomers by mixing them with various amount of 2,2-dimethoxy 1,2-diphenylethanone photoinitiator molecule with high absorption coefficient at the frequency of UV light used in these experiment. The simulations of the results obtained from microrheology experiments were carried out with the new model based on the stochastic Monte Carlo approach in order to account for the inherently random and discrete nature of the photopolymerization reactions. The model captures the nonlinear decrease of gelation time with increasing photoinitator concentration and number of acrylate fragments on each monomer. POLYM. ENG. SCI., 51:1710-1719, 2011. (C) 2011 Society of Plastics Engineers

The crystallization behavior and kinetics of glasses produced from coal fly ashes, red mud and silica fume were investigated by using differential thermal analysis, X-ray diffraction and scanning electron microscopy techniques. The kinetic parameters of the glass-crystallization transformation were estimated under non-isothermal conditions applying three different equations, namely, Kissinger, Matusuta-Sakka and Ozawa. Non-isothermal differential thermal analysis curves were obtained using both coarse and fine glass samples. The crystallization activation energies of coarse glasses are in the range of 233–439 kJ/mol while the activation energies of fine glasses change in the range of 369–450 kJ/mol. Avrami exponent, n , values of coarse glasses indicated the three-dimensional bulk crystallization. This result is in well agreement with the cross-sectional scanning electron microscopy investigations. The values of the n obtained experimentally are in the range of 1.24–1.36 for fine glasses which show the one-dimensional surface crystallization. The crystallized phase of the glass-ceramic samples produced from waste glasses by applying the controlled heat treatment process was identified as diopside by X-ray diffraction analysis.

Activated carbons prepared from chestnut shell and grapeseed were used as adsorbent for the removal of Cu (II) ions from aqueous solutions. Adsorption experiments were performed by varying initial metal ion concentration, temperature and pH. Freundlich and Langmuir isotherms were used to analyze the equilibrium data obtained at different adsorption conditions. It was observed that Freundlich isotherm provided better fit to the equilibrium data than Langmuir isotherm. Effects of temperature, pH and adsorbent surface area on the adsorption capacity constant of Freundlich and Langmuir isotherms were statistically investigated by using a two-level factorial design technique and empirical regression equations were developed. It was determined that the adsorption capacities of adsorbents increased with increasing temperature, pH and surface area. The SEM images of adsorbents before and after adsorption were compared.

Sintered glass-ceramics were produced from coal fly ashes, red mud from aluminum production and silica fume. The capabilities of Tuncbilek fly ash and a mixture of Orhaneli fly ash, red mud and silica fume to be vitrified and devitrified by sintering process were investigated by means of scanning electron microscopy and X-ray diffraction analysis. To determine the effect of binder in the sintering technique, glass powders were pressed without or with the addition of polyvinyl alcohol. Owing to microstructural observations, density and hardness measurements, it can be said that physical properties and the hardness of the produced samples strongly depended on the crystallization degree of the samples. Toxicity characteristic leaching procedure test results showed that glass-ceramic samples produced by using sintering technique could be considered as non-hazardous materials. Chemical durability of the sintered glass-ceramic samples was also good. Microstructural investigations, hardness and physical properties of the samples indicated that the addition of polyvinyl alcohol improved the properties of sintered glass-ceramics obtained from Orhaneli fly ash, red mud and silica fume.

The crystallization kinetics of glasses obtained from coal fly ash was investigated by both isothermal and non-isothermal methods using differential thermal analysis (DTA) data. In DTA experiments, glass samples having coarse (800–1000 μm) and fine (

Carbonization experiments of grapeseed and chestnut shell samples having the average particle size of 0.657 mm and 0.377 mm, respectively, were performed to determine the effect of temperature, sweep gas flow rate and heating rate on the biochar yield. A statistical design technique was applied by the use of a two-level factorial design matrix to interpret experimental results. Carbonization conditions were selected according to a two-level factorial design matrix considering the following variables: temperature (723 K and 823 K), nitrogen gas flow rate (0 and 1000 cm 3 /min) and heating rate (5 and 20 K/min). Empirical relations between the biochar yield and the carbonization conditions were developed. To comment on the effect of parameters between the superior and inferior levels and to prove the accuracy of design equations from statistical design technique, biochar yields obtained at different conditions were also presented in the graphical way. It was found that temperature has the strongest effect on the biochar yields in comparison with nitrogen gas flow rate and heating rate. Biochar yields of grapeseed and chestnut shell were decreased with the increasing temperature, heating rate and sweep gas flow rate. A comparison between the fuel properties of waste materials and biochar products was also done.

Carbonization experiments of hybrid poplar samples were performed in a thermogravimetric (TG) analyzer to investigate the effect of carbonization conditions, such as heating rate, particle size and sweep gas flow rate on the biochar yield. During carbonization, samples were heated from room temperature to the temperature of 723 K in an inert atmosphere. A statistical design technique was applied by using a two-level factorial design matrix to elucidate the experimental results. It was obtained that the biochar yields of samples were changed depending on the carbonization conditions. Empirical relations between the biochar yield and the carbonization conditions were developed. Biochar yields of samples were decreased with the increasing heating rate and sweep gas flow rate and increased with the increasing particle size. Kinetic analysis of the carbonization TG curves was achieved by using three different methods of calculation; also, 19 different model equations of possible solid-state rate controlling mechanisms were considered. A computer program in BASIC which enables regression analysis was used to calculate kinetic parameters from experimental TG data. It was observed that the carbonization conditions and the method of calculation influenced the kinetic results obtained.

Can, Catalagzi, Seyitomer and Afsin-Elbistan thermal power plant fly ashes were used to investigate the sintering behavior of fly ashes. For this purpose, coal fly ash samples were sintered to form ceramic materials without the addition of any inorganic additives or organic binders. In sample preparation, 1.5 g of fly ash was mixed in a mortar with water. Fly ash samples were uniaxially pressed at 40 MPa to achieve a reasonable strength. The powder compacts were sintered in air. X-ray diffraction analysis revealed that quartz (SiO2), mullite (Al6Si2O13), anorthite (CaAl2Si2O8), gehlenite (Ca2Al2SiO7) and wollastonite (CaSiO3) phases occurred in the sintered samples. Scanning electron microscopy investigations were conducted on the sintered coal fly ash samples to investigate the microstructural evolution of the samples. Different crystalline structures were observed in the sintered samples. The sintered samples were obtained having high density, low water adsorption and porosity values. Higher Al2O3 + SiO2 contents caused to better properties in the sintered materials.

The recycling of three different fly ashes obtained from the coal fired thermal power plants has been studied. Coal fly ashes were vitrified by melting them at 1773 K for 5 h without any additives. After the glass production, glass samples were subjected to a heat treatment process to be able to see whether or not the glasses could be transformed into a microcrystalline structured materials. Produced glass samples were heated to 1423 K and held at this temperature for 2 h to determine the effect of heat treatment process on the properties of glasses. The properties of glass and the heat treated glass samples produced from coal fly ash were investigated by means of differential thermal analysis (DTA), X-ray diffraction (XRD) and scanning electron microscopy (SEM) techniques. DTA study indicated that there were only inflection points of the endothermic peaks in the DTA curves of the glass samples. XRD analysis showed the amorphous state of the glass samples and also the presence of only the diopside phase in the heat-treated glass samples. SEM investigations revealed that small amount of crystallites occurred in the microstructure of the heat treated glass samples in contrast to the amorphous structure of the glass samples. The mechanical, physical and chemical properties of the heat-treated glass samples are found better than those of the glass samples. Toxicity characteristic leaching procedure (TCLP) results showed that the heavy metals of fly ashes were successfully immobilized into both glass and heat treated glass samples. It can be said that glass and heat treated glass samples obtained by the recycling of coal fly ash can be taken as a non-hazardous material. Overall, results indicated that the vitrification technique is an effective way for the stabilization and recycling of coal fly ash.

The recycling of fly ash obtained from the combustion of coal in thermal power plant has been studied. Coal fly ash was vitrified by melting at 1773 K for 5 hours without any additives. The properties of glasses produced from coal fly ash were investigated by means of Differential Thermal Analysis (DTA), X-ray Diffraction (XRD) and Scanning Electron Microscopy (SEM) techniques. DTA study indicated that there was only one endothermic peak at 1003 K corresponding to the glass transition temperature. XRD analysis showed the amorphous state of the glass sample produced from coal fly ash. SEM investigations revealed that the coal fly ash based glass sample had smooth surface. The mechanical, physical and chemical properties of the glass sample were also determined. Recycling of coal fly ash by using vitrification technique resulted to a glass material that had good mechanical, physical and chemical properties. Toxicity characteristic leaching procedure (TCLP) results showed that the heavy metals of Pb, Cr, Zn and Mn were successfully immobilized into the glass. It can be said that glass sample obtained by the recycling of coal fly ash can be taken as a non-hazardous material. Overall, results indicated that the vitrification technique is an effective way for the stabilization and recycling of coal fly ash.

In this study, the removal of Cu 2+ and Pb 2+ ions by precipitation from aqueous solutions by using six fly ashes with different compositions was achieved. The effect of four parameters on the removal of Cu 2+ and Pb 2+ , which are contact time, fly ash composition, pH of the solution and fly ash concentration, were investigated. The fly ash concentrations required to achieve maximum Cu 2+ and Pb 2+ removal were found to vary between 0.2–10 and 0.075–3.5 g/l, respectively. It was also observed that both the Cu 2+ and Pb 2+ removal capacities of the fly ashes depend strongly on their CaO content.

Mixtures of Ca(OH) 2 and diatomite were hydrated at different conditions to produce reactive SO 2 sorbents. Two different hydration techniques were used; namely, atmospheric and pressure hydration. The effect of the hydration temperature, time and diatomite/Ca(OH) 2 weight ratio on the physical properties of the activated sorbents were investigated. In atmospheric hydration, it was found that increasing the temperature and hydration time caused an increase in the total surface area of the sorbents. However, surface area values of the sorbents prepared from mixtures which have different diatomite/Ca(OH) 2 weight ratio were generally not changed significantly. In pressure hydration, the surface area of the activated sorbents was positively affected from the hydration temperature and pressure. Finally, Ca(OH) 2 and two diatomite/Ca(OH) 2 sorbents were sulphated at constant temperature (338 K ) using a synthetic gaseous mixture consisting of 5% O 2 , 10% CO 2 , 5000 ppm SO 2 and the balance of nitrogen with a 55% relative humidity. The sulphation reaction of these sorbents were investigated and modelled. The unreacted shrinking core model was chosen to describe this non-catalytic solid/gas (hydrated sorbent/SO 2 ) reaction mechanism. The experimental results were found to be correlated successfully by this model.

The effect of quenching in air on the microstructure and the mechanical properties of the fly ash-based glass-ceramic samples were investigated. SEM observations clearly revealed that the presence of homogeneously dispersed tiny crystallites and crystalline grain size which increased with holding time at the nucleation stage. Furthermore, extensive cracks on the surface of the glass-ceramics were present due to quenching in air. On the other hand, XRD analyses clearly showed that the only crystalline phase that observed was diopside (Ca(Mg, Al)(Si, Al) 2O6). The result of the Vickers microhardness tests indicated that the hardness values of the fly ash-based glass-ceramics decreased with increasing holding time at the nucleation temperature. Resistance to wear decreased with the increase in crystalline grain size, similar to hardness values.

Glass-ceramic materials were produced from fly ash samples obtained from the Seyitomer thermal power plant in Turkey. Glass samples were crystallized by suitable nucleation and crystal growth heat treatments on the basis of DTA results. The microstructural analysis of glass-ceramic samples were carried out using SEM and XRD techniques. SEM investigations clearly demonstrated the presence of a tiny crystallized phase dispersed in the microstructure. XRD results revealed that the main crystalline phase was diopside [Ca(Mg,Al)(Si,Al) 2 O 6 ]. It was observed that the mechanical properties and the thermal expansion coefficient of the glass-ceramic samples depend only on the amount of the crystalline phase. Furthermore, chemical durability of the produced glass-ceramic samples were high.

In this study, the combustion reactivity of different rank coals, such as peat, lignite, bituminous coal and anthracite samples, was investigated. Non-isothermal thermogravimetry has been used to determine the combustion reactivities of the samples. The differences observed in the burning profile of the samples were studied. The calculated activation energy values of the samples were investigated, regarding carbon content, volatile matter content and burning profile peak temperature. The relationship between ignition temperature and carbon content (dmf) of the coal samples was also studied. The weight loss percentages of the different rank coal samples were discussed, depending on temperature.

The crystallization behaviour of fly ash based glass samples annealed at 600°C for 2 and 10 h was investigated by DTA, XRD and SEM. On the basis of DTA, nucleation experiments of two glass samples were carried out at 680 and 687°C for 5 h and crystallization experiments were performed at 924 and 892°C for 20 min. The Avrami constant for both glass samples was calculated as 4, which indicates bulk crystallization, predicted by the Ozawa equation. Using the modified Kissinger equation, activation energies of crystal growth were determined as 318 and 312 kJ/mol for samples annealed at 2 and 10 h, respectively. Single peak analysis technique proved that the activation energy is independent of DTA heating rate. SEM observations indicated that the produced glass–ceramic samples have fine grained microstructure. The crystallized phase was identified as diopside [Ca(Mg,Al)(Si,Al)2O6] by X-ray diffraction analysis. The results of Vickers microhardness tests showed that the hardness values of the produced glass–ceramic samples decreased with the increase in holding time at the annealing temperature.

The purpose of this study is to relate the combustion reactivity of lignite to its physical and chemical properties. Non-isothermal thermogravimetry, where the sample whose temperature increased at a linear rate (40 K/min) was heated in air, has been used to investigate the combustion reactivities of 25 lignite samples originating from different areas of Turkey. Since combustion reactivity is affected by the chemical and physical properties of coal, the combustion reactivity of the lignites used in this study was related to their proximate and ultimate analysis results and physical properties such as pore structure and surface area. The calculated activation energy values for the combustion reactions of the lignites ranged between 64 and 139 kJ/mol. Definite correlations between the activation energy values and the above-mentioned properties were found.

In this study, the effect of mineral matter on the combustion reactivity of chars produced from 25 lignite samples originating from various parts of Turkey was investigated. Char samples were produced from both original and demineralized lignites. Non-isothermal thermogravimetry has been used to determine the combustion reactivity of the samples. The combustion activation energies were calculated by the Coats-Redfern and Zsako methods from their TG data. Burning profiles of the original and demineralized lignite chars were also compared and discussed. The relationship between the carbon contents of the parent lignites and the conversions of their chars at 1273 K was studied as well. It was observed that the mineral species showed an important effect on the combustion reactivity of the char samples.

In this study, effect of demineralization on the combustion reactivity of 25 lignite samples, originating from different areas of Turkey, was investigated. Non-isothermal thermogravimetry, where the sample was heated in air where temperature increased at a linear rate of 40 K/min to 1273 K, has been used to investigate the combustion reactivities of the original and demineralized lignite samples. The activation energies calculated by two different methods and the burning profiles of the original and demineralized samples were compared and discussed. It was observed that the combustion reactivity of the samples was considerably influenced by the demineralization process applied.

In this study, the combustion characteristics of blends of a Turkish lignite and a Siberian bituminous coal with and without binder materials were investigated. Sunflower shell, sawdust, and molasses were used as binder materials. The combustion curves of the coal and binder material samples and of the blends were obtained using differential thermal analysis (DTA). The differences observed in the DTA curves of the samples are discussed in detail.

In this study, effects of total mineral matter content and of elements Ca, Mg, Na, K, Si and Al on the combustion reactivity of 25 lignite samples, originating from different areas of Turkey, was investigated. Non-isothermal thermogravimetry, where the sample was heated in air and the temperature of which increased at a linear rate of 40 K min−1 to 1273 K, has been used to investigate the combustion reactivities of the lignite samples. The calculated combustion activation energy values were related to the mineral impurities and definite correlations were observed.

The sulphation reaction of hydrated silica fume–Ca(OH)2 sorbents were investigated and modelled. These experiments were conducted in a thermogravimetric analyzer under isothermal conditions and in a humidified gaseous atmosphere consisting of 5 vol% O2, 10 vol% CO2, 0.5 vol% SO2 and the balance of nitrogen. The effect of the relative humidity on the reaction rate was determined by sulfating of hydrated sorbents in the gaseous atmospheres which have three different relative humidities: 25%, 55% and 90%. The unreacted shrinking core model was chosen to describe this non-catalytic solid/gas (hydrated sorbent/SO2) reaction mechanism. The experimental results were found to be correlated successfully by this model. It was determined that chemical reaction is partly rate limiting especially at the beginning of sulphation, diffusion through the calcium sulphite hemihydrate product layer generally controls the reaction rate.

Regeneration properties of sulfated dolomite and limestone samples were investigated. Natural stones were first fully calcined at 1223 K in a gaseous atmosphere consisting of CO{sub 2} 15 vol. % and dry air 85 vol. %; second, sulfation of the calcines was achieved by reacting them with a gaseous mixture consisting of CO{sub 2} 15 vol. %, SO{sub 2} 0.35 vol. %, and a balance of dry air at 1223 K; last, sulfated calcines were regenerated at 1373 K by a reductive decomposition process. During regeneration a 3:1 volumetric ratio of CO{sub 2}/CO was maintained in the reducing gaseous atmosphere to minimize CaS formation. It has been found that for the five sulfation-generation cycles the reactivity of the limestone and dolomite samples remained at acceptable levels. Since the repeated sulfation-regeneration steps caused an important change on the crystal lattice, as compared to the fresh stones, sorbent reactivity was also changed.

Siliceous materials such as silica fume, bentonite and diatomite were mixed with Ca(OH)2 and hydrated at different conditions to produce reactive SO2 sorbents. Two different hydration methods were used; namely atmospheric and pressure hydration. The effects of the hydration temperature, time and siliceous material/Ca(OH)2 weight ratio on the physical properties of the activated sorbents were investigated. A statistical design technique was applied by use of a two-level factorial design matrix to interpret experimental results. In atmospheric hydration, it was found that increasing the temperature and hydration time caused an increase in the total surface area of the sorbents. But, increasing the siliceous material/Ca(OH)2 weight ratio caused a decrease in the total surface area of the sorbents. The relative surface area increments of sorbents are also influenced by the chemical composition of the siliceous material. In pressure hydration, mathematical analysis showed that the surface area of the activated...

Ca(OH)2 was activated towards SO2 by hydrating it with various fly ashes collected from three different coal-fired power plants in Turkey. Reactive Ca(OH)2–fly ash sorbents were prepared using both atmospheric and pressure hydration techniques. The hydrated sorbents were analyzed using mercury porosimeter, thermogravimetric analyzer and X-ray diffractometer. The relative surface area increments of sorbents are influenced by the hydration conditions and the source of the fly ash. The reactive species formed during hydration as detected with X-ray diffraction measurements, were found to be responsible for these surface area increments. Thermogravimetric measurements showed that decreasing the Ca(OH)2 content of the hydrated sorbent which was presumably converted to Ca-containing reactive species caused an increase in the surface area of the sorbent. It was concluded that the reactivity of hydrated sorbents towards SO2 closely related to the sorbent surface area and the presence of the reactive species in the sorbent.

The sulphation reaction of the calcines produced from four limestone and one dolomite samples were investigated and modeled. The experiments were conducted in a thermogravimetric analyzer under isothermal conditions and in a gaseous atmosphere consisting of 15 vol% CO 2 , 0.35 vol% SO 2 and balance of dry air by volume. The variation of reaction rate with temperature was determined by sulphating of calcines at three different temperatures: 1023, 1173 and 1273 K. Based on the initial sulphation rates, the apparent activation energies were calculated as 51.58, 145.20 and −37.79 kJ/mol for L01, L04 and D01 samples, respectively. The unreacted shrinking core model was chosen to describe this non-catalytic solid/gas (CaO/SO 2 ) reaction mechanism. The experimental results were found to be correlated successfully by this model and diffusion through the calcium sulphate product layer is rate limiting.

The chemical reaction between sulphur dioxide and calcined limestone and dolomite particles was investigated using a thermogravimetric analyser. The samples used in this study originated from different parts of Turkey. Sulphation reactions were conducted under isothermal conditions in a gaseous mixture consisting of 15 vol% CO 2 , 0.35 vol% SO 2 and a balance of dry air by volume. Before sulphation all samples were completely calcined in a gaseous atmosphere of 15 vol% CO 2 and 85 vol% dry air. It was observed that the sulphation reactions of samples are very rapid in their initial stage but after some reaction time, which varies depending on sample properties and temperature, the reaction rates quickly slow down. Also, the conversion-time results of sulphation experiments showed variations depending on the sulphation temperature, sorbent type and the physical properties of calcines.

A number of methods have been developed which are used to remove the sulphur present in coal before combustion. The physical removal of pyritic sulphur by coal cleaning has been commercial practice for a number of years, but these methods do not remove organically bound sulphur, they can be applied effectively only to a limited number of coals. However, the removal of both pyritic and organically bound sulphur from coal can be effectively achieved by applying the chemical desulphurization methods. This paper gives a general review on the chemical desulphurization studies, including carbonization in different atmospheres, air oxidation, wet oxidation, Meyers Process, chlorination and extraction with the solutions of NaOH, CuCl2 and C2H5OH, which were carried out using different Turkish lignites.

Calcination kinetics of six dolomite samples originating from different parts of Turkey were investigated by using the non-isothermal thermogravimetry technique. Calcination TG curves of samples were obtained under two different atmospheres of (1) pure nitrogen and (2) a mixture consisting of 15 vol.% CO 2 and 85 vol.% dry air, by using a constant heating rate of 10 K min −1 . Kinetic analysis of the curves was achieved by applying four different methods of calculation; also, 14 different model equations of possible solid-state rate controlling mechanisms were considered. Arrhenius parameters E and A and the model function f (α) that best describes the reaction mechanism were evaluated for the decomposition reactions of both MgCO 3 and CaCO 3 components of samples. A computer program in basic which enables regression analysis to be carried out was used to obtain kinetic results from experimental non-isothermal TG data. It was observed that besides differences in the chemical composition of samples, gaseous atmosphere and the method of calculation influenced the results obtained.

The kinetic parameters for the thermal decomposition of 20 natural Turkish limestones, including the activation energy, pre-exponential factor and mechanism, were determined from their non-isothermal TG data. Thermogravimetric measurements were made in pure N2 and in a mixture of 15% CO2 and 85% dry air, at a constant heating rate of 10 K min−1. A computer program written in basic was used to evaluate the kinetic parameters of the decomposition reactions from experimental TG data. Five different calculation methods were employed in the kinetic analysis of the TG curves of the samples; this analysis also incorporated 14 different model equations reported in the literature concerning solid state rate-controlling mechanisms. It was observed that the values of the kinetic parameters showed differences depending on the method of calculation, the gaseous atmosphere and the sample properties.

Total sulphation capacities of 36 limestone and 6 dolomite samples, originating from different parts of Turkiye, were determined. Sulphation experiments were carried out in a tube furnace at a constant temperature of 1173 K and in a gaseous mixture consisting of 15 vol% CO2, 0.35 vol% SO2 and a balance of dry air by volume. Measured sulphation capacities of limestone samples from 0.381 to 0.689 (mg S03/mg sorbent) and those of dolomites range between 0.321–0.498 (mg SO3/mg sorbent). Sorption capacities of the stones were found vary significantly depending on physical properties of the calcines of the stones and an empirical relation between the sorption capacity and physical properties (total pore volume and pore radius) of calcines was obtained.

Activated carbons prepared from hazelnut shells and apricot stones were used as adsorbents for the removal of copper(II) ions from aqueous solution. Adsorption studies were carried out by varying the initial metal ion concentration, the temperature and the pH. The amount of Cu(II) ions adsorbed increased with increasing temperature, pH and initial Cu(II) ion concentration. The equilibrium data were analyzed using the Freundlich and Langmuir isotherms. The parameters of the isotherm models were determined for two activated carbons; it was found that the Freundlich model showed a better fit of the adsorption data than the Langmuir model. The physical and chemical properties of hazelnut shell and apricot stone activated carbons were determined for comparative purposes.

Glass, glass-ceramic and ceramic materials were produced from thermal power plant fly ash without any additives. X-ray diffraction (XRD) analysis revealed the amorphous phase of the glass sample. Augite phase was detected in the glass-ceramic sample, while the enstatite and mullite phases occurred in the ceramic samples. Scanning electron microscopy (SEM) investigations showed that tiny crystallites homogeneously dispersed in the microstructure of the glass-ceramic sample and elongated crystals formed in the ceramic samples. Density values of the obtained samples are comparable to those of the commercially produced glass, glass-ceramic and ceramic samples. Toxicity characteristic leaching procedure (TCLP) results indicated that the produced samples could be taken as non-hazardous materials. Produced samples showed high resistance to alkali solutions in contrast to acidic solutions. Microstructural, physical, chemical and mechanical properties of the produced glass-ceramic samples are better than those of the produced glass and ceramic samples.

New formulae have been developed for estimating the calorific values of Turkish lignites from their proximate analyses data. In order to obtain these formulae, 24 Turkish lignites from different areas were analysed to obtain calorific values and proximate analyses. The data of another 26 Turkish lignites obtained from the literature were used to check the developed correlations. All the correlations were obtained using least squares regression analysis. The mean differences between observed and calculated calorific values using the formulae developed range from 3.78 to 7.56%.

1. Abstract Two different gaseous atmospheres were employed to examine the changes of calcination TG curves of 20 natural limestone and 6 dolomite samples from various parts of Turkiye. Calcination TG curves of these samples were obtained in atmospheres of 1) pure nitrogen; and 2) 15% by volume CO 2 in dry air, and they were recorded under non-isothermal conditions. It was found that, initial and final calcination temperatures were effected by furnace atmosphere. Also, the shape of TG curves of both limestone and dolomite samples were strongly effected from CO 2 partial pressure. All samples were sulfated in a tube furnace at a constant temperature of 1173 K. The composition of the gaseous mixture used in the sulfation experiments was 15 vol % CO 2 , 0.35 vol % SO 2 and balance of dry air by volume. Total sulfation capacities of the calcines prepared from limestone samples range from 0.381 to 0.686 (mg SO 3 /mg sorbent) and those from dolomite samples range between 0.321-0.498 (mg SO 3 /mg sorbent).