Adsorption properties of activated carbon from waste newspaper prepared by chemical and physical activation

Adsorption properties of activated carbons prepared from waste newspaper by chemical and physical activation were investigated using water vapor, ammonia, methane, and methylene blue (MB) as adsorbents. The water vapor adsorption isotherms show type V behavior and the maximum vapor adsorption of the chemically and physically activated products is about 1050 and 450 ml/g, respectively. The higher water vapor adsorption of the chemically activated products is attributed to the higher specific surface area (S(BET)) and greater hydrophilic activity (arising from the surface oxygen-containing functional groups) than in the physically activated products. The adsorption of ammonia and methane was measured by temperature-programmed desorption (TPD). NH(3) adsorption is found to be higher in the chemically activated product than in the physically activated product while methane adsorption is slightly higher in the physically activated products even though these have lower S(BET) values. In the MB adsorption, the chemically activated products show higher adsorption (390 mg/g) than the physically activated product. These results are suggested to be related to the surface characteristics.     

Preparation of a novel molecularly imprinted polymer using a water-soluble crosslinking agent

A molecularly imprinted polymer was prepared using a water-soluble crosslinking agent. An ionic complex was utilized as the assembly for the template molecule and the functional monomer, and water as porogenic solvent during preparation of the imprinted polymer. The results of chromatographic evaluations for the prepared polymer suggested that the polymer had much lower hydrophobicity compared with usual octadecyl group bonded silica or the usual molecular imprinted polymer prepared from ethyleneglycol dimethacrylate, and the selective recognition ability for template molecule in the completely aqueous condition.     

A new reforming process based on CH4 decomposition using a hydrogen-permeating membrane reactor

A new reforming process was studied using Ni/SiO₂ with a hydrogen-permeating membrane reactor. Nickel catalyst supported on SiO₂ is highly active for CH₄?H₂O?O₂ reaction in membrane reactor and the reaction close to CH₄+0.35O₂+1.3H₂O→CO₂+3.3H₂ proceeds at 873 K. Since the selectivity to carbon and CO₂ increased and decreased with decreasing contact time respectively, it is considered that the reaction was started by decomposition of CH₄ followed by oxidation of C and water shift reaction. Therefore, the reaction mechanism was different from so-called autothermal reforming (ATR) reaction.     

Reactivity and Structural Properties of a Mechanochemically Treated Ag2O-V2O5 System in Relation to AgVO3 Polymorphs

Formation and chemical properties of amorphous AgVO₃, which was prepared by mechanochemical treatment of an Ag₂O-V₂O₅ mixture, and crystalline AgVO₃ were studied in relation to AgVO₃ polymorphs. A ball-milled sample of the mixture was assigned as a highly deformed β-AgVO₃ rather than the low density phase α-AgVO₃. Crystalline α-AgVO₃ and β-AgVO₃ were converted into deformed β-AgVO₃ by ball milling, which produced a clear change. δ-AgVO₃ is resistant to mechanical treatment and its structure was not markedly affected. The dissolved chemical species from the ball-milled sample precipitates to form α-AgVO₃ without a seeding crystal, but other polymorphs deposit if they are present; i.e., β-AgVO₃ and δ-AgVO₃ grow on the seeding crystal.     

Mössbauer study of semiconducting and ferrimagnetic fly ash-recycled glass

Summary Room temperature M?ssbauer spectrum of fly ash-recycled glass (FARG), prepared with more than 86 mass% of fly ash and less than 14 mass% of Fe₂O₃, comprises two types of doublets due to Fe(II) and Fe(III) of magnetite nanoparticles. Isothermal annealing of fly ash-recycled glass at 1100 °C for 60 minutes results in a precipitation of ferrimagnetic magnetite phase having an internal magnetic field of 46.4-48.2 T. When the Fe₂O₃ content is equal to or more than 14%, room temperature M?ssbauer spectrum of FARG shows a magnetic hyperfine structure due to a magnetite phase, in addition to two doublets due to Fe(II) and Fe(III). An increase in the electric conductivity is observed from the order of 10^-8 to 10^-6 S ^. cm^-1 after heat treatment at around the crystallization temperature. This can be ascribed to an improved step-by-step electron hopping from Fe(II) to Fe(III) of distorted FeO₄ tetrahedra in the three-dimensional glass network.     

Preparation of a thermally phase-separating copolymer,poly(N-isopropylacrylamide-co-N-acryloxysuccinimide), with a controlled number of active esters per polymer chain

N-isopropylacrylamide and N-acryloxysuccinimide have been copolymerized in various mixtures of terrahydrofuran and toluene using azobisisobutyronitrile as initiator. Polymerization has been conducted for 24 h at 50°C under a slightly positive pressure of nitrogen. The copolymers were assayed for active ester content by measuring the UV absorbance (259 nm) of N-hydroxysuccinimide anion, generated by reacting the copolymers with N-isopropylamine in dimethylformamide and dissolving the resulting mixture in 0.1M HEPES buffer, pH 7.5. The molecular weight and its distribution have been estimated by gel permeation chromatography. The active ester content was found to be equivalent to the comonomer feed ratio, and the major factor controlling the molecular weight was the ratio of tetrahydrofuran to toluene. Thus, the number of active esters per polymer chain could be controlled by adjustment of the comonomer feed ratio and the ratio of tetrahydrofuran to toluene. Monomer reactivity ratios for copolymerization of N-isopropylacrylamide with N-acryloxysuccinimide were also estimated. These copolymers are useful for immobilizing binding ligands such as antibodies for subsequent thermally induced precipitation immunoassays and bioseparation processes.     

Two-dimensional separation system of coupling capillary liquid chromatography to capillary electrophoresis for analysis of Escherichia coli metabolites

A two-dimensional (2-D) separation system of coupling chromatography to electrophoresis was developed for profiling Escherichia coli metabolites. Capillary liquid chromatography (LC) with a monolithic silica-octadecyl silica column (500 x 0.2 mm ID) was used as the first dimension, from which the effluent fractions were further analyzed by capillary electrophoresis (CE) acting as the second dimension. Field-enhanced stacking was selectively employed as a concentration strategy to interface the two dimensions, which proved to be beneficial for the detection of metabolites. An artificial sample containing 118 standards, some of which lack chromophores or have weak UV absorbance, was used to optimize the 2-D separation system. Under the optimum conditions, 63 components in the artificial sample having absorbance at 254 nm could be well resolved and detected. The utility of the system was demonstrated by comprehensive analysis of E. coli metabolites. Comparing with the previous 2-D separation system we published in Anal. Chem. 2004, 76, 1419-1428, using a longer monolithic column in the first dimension improved the separation efficiency and offered the possibility of increasing the injection volume without compromising the separation efficiency. In the second dimension, field-enhanced stacking was used to improve the concentration sensitivity of the metabolites, and more metabolites in E. coli cell extract were detected and identified using the developed 2-D separation system. In addition, preliminary investigation for future CE-mass spectrometry coupling was also made in the study by using volatile buffers in the capillary LC and CE techniques.     

A highly diastereoselective pinacol coupling reaction of aldehydes and ketones using low-valence niobium generated from Nb(V)

A simple method for the diastereoselective synthesis of racemic 1,2-diol mediated by low-valence niobium generated in situ is described. A 1,4-dioxane-toluene solvent system was found to be essential to achieve higher selectivities and to prevent other reactions of pinacols, such as deoxygenation and acetal formation. Aromatic aldehydes and ketones were converted to the corresponding pinacols with up to 97 and 85% de, respectively.     

Unexpected formation of benzaldehydes by the reactions of dithioacetals derived from cinnamaldehydes with 2,3-dichloro-5,6-dicyano-p-benzoquinone in aqueous solvents

1,3-Dithianes 1 , 1,3-dithiolanes 2 , and diphenyl dithioacetals 3 derived from cinnamaldehydes reacted with 2,3-dichloro-5,6-dicyano-p-benzoquinone in aqueous solvents to give benzaldehydes 4 . Hydride transfer from 1–3 to 2,3-dichloro-5,6-dicyano-p-benzoquinone followed by hydrolysis and oxidative carbon-carbon bond cleavage would produce benzaldehydes 4 .     

Electrochemical control of CO/NO ligand exchange in a triruthenium cluster monolayer assembled on a gold electrode surface

A highly selective ligand exchange reaction is realized in the self-assembled monolayer (SAM) of a triruthenium cluster on a gold electrode surface under precise electrochemical potential control. CO as well as NO molecules, which are known to play key roles in many chemical, biological, and environmental systems, can be efficiently introduced into the SAM by electrochemically tuning the electronic state of the Ru site. These unique surface reactions are more convenient and efficient than conventional ligand exchange reactions in solution and could be used for the elucidation of the electron-transfer mechanism in a biological system as well as in the development of molecular sensors and devices.