Yuda Yürüm

Batch removal of copper(II) and zinc(II) from aqueous solutions with low-rank Turkish coals

Abstract The removal of heavy-metal ions from aqueous solutions containing low-to-moderate levels of contamination using Turkish Beypazari low-rank coal was investigated. Carboxylic acid and phenolic hydroxyl functional groups present on the coal surface were the adsorption site to remove metal ions from solution via ion exchange. The equilibrium pH of the coal/solution mixture has been shown to be the principal factor controlling the extent of removal of Cu(II) and Zn(II) ions from aqueous solutions. The optimum pH was measured to be 4.0 and it was found that the adsorption reached equilibrium in 20 min. The maximum adsorption capacities of the metal ions from their single solutions were 1.62 mg for Cu(II) and 1.20 mg for Zn(II) per g of coal. The order of affinity based on a weight uptake by coal was as follows: Cu(II)>Zn(II). The same behavior was observed during the competitive adsorption, that is in the case of adsorption from their binary solutions. The adsorption phenomena appeared to follow a typical Langmuir isotherm. It was observed that use of low-rank coal was considerably effective in removing Cu(II) and Zn(II) ions from aqueous solutions. Higher amounts of adsorbed metal ions could be desorbed (up to 80%) using 25 mM EDTA. Low-rank Turkish coals are suitable for consecutive use for more than three cycles without significant loss of adsorption capacity.

Carbon Nanotube Synthesis via the Catalytic CVD Method: A Review on the Effect of Reaction Parameters

Abstract This review covers the results obtained in carbon nanotube synthesis by chemical vapor deposition. Parameters such as catalysts, supports, carbon precursors, reaction time, temperature and gas flow rates that are used in the production of carbon nanotubes are discussed throughout the text. Purification of the synthesized carbon nanotubes and methods utilized for cost reduction were also explored.

Pyrolysis of Turkish Zonguldak bituminous coal. Part 1. Effect of mineral matter

Abstract The effects of mineral matter on the conversion of organic material in low temperature pyrolysis (300–500°C) of the vitrinite-rich Zonguldak bituminous coal and acid-washed coals were investigated. Calcium, iron and magnesium cations were removed from coal with HCl washing. The results indicated that these cations had catalytic effects during pyrolysis. It was also observed that the conversion in the pyrolysis processes was increased with the removal of the illite, kaolinite, chlorite and quartz minerals. The volumetric swelling ratios of the chars obtained in different experimental conditions were measured using the pyridine swelling technique and the extent of cross-linking in the macromolecular network of chars was examined. It was found that the cross-linking increased as the pyrolysis temperature was increased from 300 to 500°C.

Effect of the mineral matrix in the reactions of oil shales: 1. Pyrolysis reactions of Turkish Göynük and US Green River oil shales

The effect of the mineral matrix of Turkish Goynuk and Green River oil shales on the conversion of kerogen into organic material in pyrolysis reactions was investigated in this study. The conversion of kerogen to volatile organic material in pyrolysis reactions increased with increased reaction temperatures for the original and demineralized products of oil shales. Increasing the heating rate also caused greater kerogen conversion. It was found that pyrolysis reactions were catalyzed by alkaline earth metal cations in carbonates and inhibited by silicates. The inhibition effect of the silicates seemed to be greater than the catalytic effect of the carbonates in the pyrolysis reactions of the original Goynuk and Green River oil shales.

Hydrogen Production Methods

Commercially available hydrogen production methods such as steam reforming of natural gas, partial oxidation of heavy oil, coal gasification, coal carbonization, steam iron process that are based on fossil hydrocarbons and methods in the stage of development, like thermolysis, radiolysis and photolysis of water, thermochemical cycles, hydrogen from hydrogen disulfide and biomass are discussed.

Air oxidation of Beypazari lignite at 50°C, 100°C and 150°C

Abstract Structural changes occurred in Beypazari lignite while oxidizing at 50°C, 100°C and 150°C in a dynamic air atmosphere was detected by infrared spectroscopy. Relative changes in the amount of various oxygenated functional groups with respect to time were determined by curve resolution procedures. Investigation of the spectra of the samples at different oxidation conditions reveal that as the duration and temperature of the oxidation reactions increased the absorption in the aliphatic C–H stretching region decreased, while the absorption in the CO stretching region presented a significant increase.

Cation exchange properties of low rank Turkish coals: removal of Hg, Cd and Pb from waste water

The removal of contaminant heavy-metal ions from spiked aqueous samples containing low-to-moderate levels of contamination using Turkish Beypazari low rank coal was investigated. Carboxylic acid and phenolic hydroxyl functional groups present on the coals surface were the adsorption site to remove cations from solution via ion exchange. The equilibrium pH of the coal/solution mixture has been shown to be the principal factor controlling the extent of removal of Hg(II), Cd(II), and Pb(II) ions from aqueous solutions. The optimum pH was measured to be 4.0 for Hg and Cd, and 5.0 for Pb and it was found that the system reached equilibrium in 20 min. The maximum adsorption capacities of the metal ions from their single solutions were 0.039 mmol for Hg(II), 0.008 mmol for Cd(II) and 0.041 mmol for Pb(II) per gram of coal. The order of affinity on a mole basis was as follows: Pb(II)>Hg(II)>Cd(II). The same behavior was observed during the competitive adsorption, that is in the case of adsorption from their ternary solutions. Waste water samples were obtained from a mining industry plant located within Aegean Region, Turkey. It was observed that the use of low rank coal was considerably effective in removing Hg, Cd and Pb cations from water.

Chemical desulfurization of Turkish Cayirhan lignite with HI using microwave and thermal energy

The purpose of the present work was to investigate the effect of the concentration of HI and reaction time in the chemical desulfurization of Cayirhan lignite in a microwave energy set up and to compare the results with those obtained in a thermal heating system. As the concentration of the HI was increased, the extent of desulfurization was also increased in all the experiments done for all of the samples of lignite. The main difference between the thermal and microwave heating was the extremely short times for desulfurization in the case of microwave experiments. After desulfurization experiments Stotal/C ratio of all of the samples decreased to a lower value than that of the raw lignite which was 0.034. The loss of the sulfur containing bands in the FTIR spectra of the desulfurized lignite showed that the HI treatment was effective in the cleavage of dithioethers and thioetheric groups. Sulfur containing functionalities like thioethers and thiols although usually requiring strong reducing agents could be removed in significant amounts with concentrated hydroiodic acid from the coal matrix. The rapidity of the desulfurization reactions with microwave heating in concentrated HI was probably due to localized superheating which made HI more effective in the reactions such as with thioethers and thiols that normally resisted to cleavage by HI under thermal heating conditions.

Interaction of kerogen and mineral matrix of an oil shale in an oxidative atmosphere

Abstract The effects of the inorganic matrix of the oil shale on the oxidation of the kerogen at temperatures up to 1000°C in an air atmosphere were investigated Kerogen was isolated by successive HCl, HF and LiAlH 4 treatments. The initial shale and each product of every demineralization process were oxidized in a thermogravimetric system in an air atmosphere. The oxidation products were analyzed by Fourier transform infrared spectroscopy. Changes in the chemical structure of the organic material of the shale were correlated with the separated constituents of the inorganic matrix. Oxidation of the kerogen occurred in two stages. The first stage was complete at about 400°C. The oxidized product after the first stage contained a char of an aromatic ring system substituted with some aliphatic material and carbonyl groups. Calcium minerals increased the reactivity of the aromatic part of the organic material towards the oxidation reactions. Where calcium minerals were absent, mainly the aliphatic and the carbonyl groups decomposed. Silicates and pyrites did not affect the reactivity of the organic material in oxidation reactions.

Removal of Boron from Aqueous Solutions by Adsorption Using Fly Ash, Zeolite, and Demineralized Lignite

In the present study for the purpose of removal of boron from water by adsorption using adsorbents like fly ash, natural zeolite, and demineralized lignite was investigated. Boron in water was removed with fly ash, zeolite, and demineralized lignite with different capacities. Ninety-four percent boron was removed using fly ash. Batch experiments were conducted to test the removal capacity, to obtain adsorption isotherms, thermodynamic and kinetic parameters. Boron removal by all adsorbents was affected by pH of solution; maximum adsorption was achieved at pH 10. Adsorption of boron on fly ash was investigated by the Langmuir, Freundlich, and the Dubinin-Radushkevich models. Standard entropy and enthalpy changes of adsorption of boron on fly ash were, ΔS 0 = −0.69 kJ/mol K and ΔH 0 = −215.34 kJ/mol, respectively. The negative value of ΔS 0 indicated decreased randomness at the solid/solution interface during the adsorption boron on the fly ash sample. Negative values of ΔH 0 showed the exothermic nature of the process. The negative values of ΔG 0 implied that the adsorption of boron on fly ash samples was spontaneous. Adsorption of boron on fly ash occurred with a pseudo-second order kinetic model, and intraparticle diffusion of boron species had also some effect in adsorption kinetics.