Ekrem Ekinci

Removal of mercury (II) from aqueous solution by activated carbon obtained from furfural

The adsorption of Hg(II) from aqueous solution at 293 K by activated carbon obtained from furfural is studied. The carbon is prepared by polymerization of furfural following carbonization and activation of the obtained polymer material with water vapor at 800 degrees C. Adsorption studies of Hg(II) are carried out varying some conditions: treatment time, metal ion concentration, adsorbent amount and pH. It is determined that Hg(II) adsorption follows both Langmuir and Freundlich isotherms. The adsorption capacity of the carbon is 174 mg/g. It is determined that Hg(II) uptake increases with increasing pH. Desorption studies are performed with hot water. The percent recovery of Hg(II) is 6%.

FT-i.r. characterization of pitches derived from Avgamasya asphaltite and Raman-Dinçer heavy crude

Abstract Pitches were prepared by three methods from Avgamasya asphaltite: (1) solvent extraction; (2) pyrolysis followed by vacuum distillation of the resulting tar; (3) air blowing of some of the vacuum-distilled tars. For Raman-Dincer heavy crude oil, only vacuum distillation was used. The chemical changes due to the different processes were studied by Fourier-transform infrared spectroscopy, softening point measurement and elemental analysis. Vacuum distillation and air blowing markedly increased the softening point, promoted dehydrogenation and aromatization through significant reduction of aliphatic structures and reduced the H C atomic ratio. The formation of oxygenated compounds is the major feature of the air blowing technique. The aromaticity and the softening point of solvent-extracted pitches depended on the effectiveness of the solvent.

Removal of mercury ion from aqueous solution by activated carbons obtained from biomass and coals

Abstract The adsorption of Hg(II) from aqueous solution at 293 K by activated carbons obtained from apricot stones, furfural and coals was studied. Adsorption studies were performed under the varying conditions of time of treatment, metal ion concentration and pH. The process of adsorption followed Langmuir isotherm. The removal of Hg(II) increased with the increase of pH of the solution from 2 to 5 and remained constant up to pH 10. Desorption studies were preformed.

The influence of the texture and surface properties of carbon adsorbents obtained from biomass products on the adsorption of manganese ions from aqueous solution

Studies on the adsorption of manganese ions from aqueous solution on carbon obtained from a mixture of biomass products indicate the importance of acidic surface oxides for manganese ion adsorption that is predominantly site specific. The results show that oxygen remaining from the raw material participates in the formation of surface oxides and indicates the possibility of controlling the content of acidic surface sites of the carbon surface by appropriate selection of the precursor composition and surface properties modification. The surface functionalities of oxidized carbon from a mixture of biomass products resembles the behavior of an ion-exchange resin. Oxidized carbon obtained from a 50:50 mixture of tar from steam pyrolysis of apricot stones and furfural contains a balance of surface area and high surface concentration of functional groups favorable for adsorption of positively charged manganese ions.

Effect of lignite addition and steam on the pyrolysis of Turkish oil shales

Abstract Steam was found to be a more effective sweep gas than nitrogen at low velocities in fixed-bed pyrolysis of Goynuk oil shale but, at higher velocities and in fluidized-bed pyrolysis, the differences were considerably less marked. Relatively small but significant synergistic effects were observed between lignites and the two oil shales investigated — Goynuk and Seyitomer — under static retorting conditions. These effects were more pronounced with large concentrations of oil shales but disappeared in fluidized-bed pyrolysis, where conversions are considerably higher because mass transfer limitations largely disappear.

Beneficial effects of hydrogen pressure in the pyrolysis of biomass: a study of Euphorbia Rigida

Abstract Fixed-bed pyrolysis and hydropyrolysis experiments at different temperatures and pressures have been conducted on a sample of Euphorbia Rigida extracted with n-hexane and methanol to remove low molecular mass terpenoids and saccharides to elucidate the extent of oil formation from the remaining predominantly cellulosic structure. The trends in yield and product composition are markedly different to those found previously for coals. Primary oil yields reached a maximum of ca 35% (daf basis corresponding to ca 60% on a carbon basis) at a hydrogen pressure of 50 bar and 500°C. Raising the temperature and hydrogen pressure decreased the oxygen contents and increased the aromaticities of the oils but also increased hydrocarbon gas yields. The relatively high nitrogen contents of the oils (2–3%) were not markedly affected by hydrogen pressure and present the major obstacle to producing light hydrocarbon oils via two-stage hydropyrolysis.

Preparation and characterization of novel UV-curable urethane methacrylate difunctional monomers and their structure-property relationships, 1

Four new UV-curable cross-linking agents namely 2,2-bis(4-β-ethoxy urethane ethyl methacrylate phenyl)propane (HEPAIEM), 2,2-bis(4-β-ethoxy urethane ethyl methacrylate phenyl)6Fpropane (HEPFAIEM), 2,2-bis(4-β-ethoxy urethane ethyl methacrylate-3,5-dibromo phenyl)propane (TBHEPAIEM), and 5-tert-butyl-1,3-bis(4-ethoxy urethane methacrylate phenyl)benzoylbenzene (tBuHEPBIEM), which can be good candidates for UV-curable coating applications, were synthesized by reacting isocyanato ethyl methacrylate (IEM) with four different diols. The structures of the monomers thus prepared were characterized by FTIR, mass and 1 H NMR spectroscopies. Introduction of new difunctional cross-linking agents affected the mechanical and physical properties of UV-cured films. Addition of 10% cross-linking agents into the formulations caused an increase both in tensile strength and elongation, when compared with widely used di(ethylene glycol)diacrylate (DEGDA) containing films. Elongation values of TBHEPAIEM containing films were exceptions. Gel contents of the UV-cured polymeric films were found to be between 88-98%. Thermogravimetric analysis showed that there were not any noticeable changes in thermal oxidative stability of the films compared with DEGDA containing ones. On the other hand, HEPFAIEM and TBHEPAIEM containing films showed increases in char yields due to the presence of F and Br in their structures. Introduction of the new difunctional monomers lowered the water absorption values of the films somewhat proportional to the methyl group content of the x-linkers.

Formation of porous structure of semicokes from pyrolysis of Turkish coals in different atmospheres

Activated carbons were obtained from Turkish coals by one-step steam pyrolysis process. The effect of the water vapor on the yield of the solid, liquid and gas products was studied. The presence of steam during pyrolysis-activation process contributes to distillation of low molecular weight products and reacts with the coal and the volatile products obtained during the pyrolysis. These processes lead to an increase in the yield of liquid and gas products and a decrease in the solid yield. The resulting carbons are determined to have good adsorption characteristics.

Characterization of liquid products from pyrolysis of subbituminous coals

Abstract Liquid products obtained during the process of steam pyrolysis and pyrolysis in inert atmosphere of four samples of subbituminous coals were the focus of interest in this work. The composition of aliphatic and aromatic fractions from silica gel chromatography of maltenes obtained both by steam pyrolysis and nitrogen pyrolysis was characterized by GC and GC–MS. Conclusions are drawn about the structure and utilization of the investigated coals.

Kinetic Investigations of Formation of Polyimides Containing Arylene Sulfone Ether Linkages by Potentiometric Titration and Their Characterization

In this work, thermal solution imidization kinetics of two high performance polyimides, prepared from the polycondensation of pyromellitic dianhydride (PMDA) and 3,3*,4,4*-benzophenonetetracarboxylic dianhydride (BTDA) with 4,4*-bis(3- aminophenoxy)diphenylsulfone (DAPDS) were investigated using nonaqueous titra- tion technique with tetramethylammonium hydroxide. Most of the kinetic investiga- tions, found in the literature, are based on the aromatic p-diamines. 1,2 In the present work, attention was focused on imidization kinetics with m-substituted aromatic di- amines having electron donating ({O{) and electron withdrawing ({SO2{) groups in the same molecule. Kinetic parameters, namely the rate constants, activation energ- ies, entropies and enthalpies of imidization reactions were determined and compared with the literature values. It is reported in literature 3 that electron affinities of dianhy- drides and ionization potentials of diamines, have strong influence on the reaction rate and activation energies of imidization. Activation energy (Ea) values were found to be 66 and 57 kJ/mol for DAPDS/PMDA and DAPDS/BTDA respectively, and order of reaction was found to be second order. Polyimides DAPDS/PMDA and DAPDS/BTDA, subjected to kinetic investigation, showed glass transition temperatures of 2677C and 2417C, both were found to be thermally stable up to 5007C. q 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35: 2981-2990, 1997