Synthesis, structure, and resolution of exceptionally twisted pentacenes

9,10,11,20,21,22-hexaphenyltetrabenzo[a,c,l,n]pentacene (2) and a dimethyl derivative (2m) were prepared by the reaction of 1,3-diphenylphenanthro[9,10-c]furan with bisaryne equivalents generated from 1,2,4,5-tetrabromo-3,6-diarylbenzenes in the presence of n-butyllithium, followed by deoxygenation of the double adducts with low-valent titanium. Both are bright red solids with a strong orange fluorescence in solution. The X-ray structures of these compounds show them to be the most highly twisted polycyclic aromatic hydrocarbons known. Compound 2 has an end-to-end twist of 144 degrees , and the two crystallographically independent molecules of 2m have twists of 138 degrees and 143 degrees. Both molecules were resolved by chromatography on chiral supports, and the pure enantiomers have extremely high specific rotations (for 2, [alpha]D = 7400 degrees; for 2m, 5600 degrees), but the molecules racemize slowly at room temperature (DeltaG++rac = 24 kcal/mol). Both the experimental geometry and the observed racemization barrier for 2 are in good agreement with computational studies of the molecule at a variety of levels. Attempts to prepare compound 2 by reaction of tetraphenylbenzyne with 9,10,12,13-tetraphenyl-11-oxacyclopenta[b]triphenylene (3, a twisted isobenzofuran) gave no adducts, and attempts to prepare tetradecaphenylpentacene by reaction of hexaphenylisobenzofuran (11) with bisaryne equivalents gave only monoadducts.     

Synthesis, structure, texture, and CO sensing behavior of nanocrystalline tin oxide doped with scandia

Weakly agglomerated nanocrystalline scandia doped tin oxide powders with high surface area (170-220 m(2)/g) and uniform size (3-4 nm) were synthesized for the first time by a two-step hydrothermal process in the presence of urea, followed by the calcination between 500 and 1200 degrees C. The structure and texture of the binary oxide system were characterized by thermogravimetry and differential thermal analysis, Brunauer-Emmett-Teller-specific surface area analysis, transmission electron microscopy, X-ray diffraction, Raman spectroscopy, and X-ray photoelectron spectroscopy. A metastable scandium tin oxide solid solution in tetragonal structure was formed for the scandia content lower than 6 mol % as the samples were calcined at 800 degrees C, and the excess Sc atoms were dispersed at the surface of the crystallites above this limit. The solid solution was metastable, so scandium migrated toward the surface region of the crystallites and produced a second phase of Sc(4)Sn(3)O(12) during calcining at high temperatures over 1000-1200 degrees C. In the case of the samples with higher dopant concentration (>15 mol %), the calcination at the temperature between 500 and 800 degrees C caused the precipitation of Sc(2)O(3), and the calcination over 1000-1200 degrees C led to the formation of more Sc(4)Sn(3)O(12). Textural analysis showed that doping an appropriate amount of Sc(2)O(3) into nanosized SnO(2) could effectively inhibit the grain growth and stabilize the surface area against high-temperature calcinations below 1000 degrees C. CO gas-sensing property measurements revealed that the dispersion of Sc at the surfaces of the SnO(2) nanocrystallites could improve the CO sensitivity significantly, and the pellet sample with scandia content of 10 mol % sintered at 800 degrees C showed the best CO gas-sensing property in the operation temperature range of 300-400 degrees C. On the basis of the structural and textural analysis, the correlation between the structure/texture and the sensitivity to CO for the as-calcined (SnO(2))(1-x)(Sc(2)O(3))(x) nanocrystallites has been established and explained.     

Temperature dependence of oxygen reduction activity at Pt-Fe, Pt-Co, and Pt-Ni alloy electrodes

Oxygen reduction reaction (ORR) activity and H(2)O(2) formation at Pt(54)Fe(46), Pt(68)Co(32), and Pt(63)Ni(37) electrodes in 0.1 M HClO(4) solution at 20 to 90 degrees C were investigated by using a channel flow double electrode method. In the temperature range of 20-50 degrees C, the apparent rate constants k(app) for ORR at these electrodes were found to be 2.4-4.0 times larger than that at a pure Pt electrode, whereas their apparent activation energies of 41 kJ mol(-1) at -0.525 V vs E degrees (0.760 V vs RHE at 30 degrees C) were comparable to that at the Pt electrode. H(2)O(2) yield was ca. 1.0% at Pt(54)Fe(46) and ca. 0.16% at Pt(68)Co(32) and Pt(63)Ni(37) between 0.3 and 1.0 V vs RHE. The k(app) values at the alloy electrodes decreased with elevating temperature above 60 degrees C, and settled to almost the same values at the Pt electrode. The H(2)O(2) production was not detected at the alloy electrodes once heated at the high temperature in the solution, probably due to the thickening of the Pt skin-layer by a considerable dissolution of nonprecious metal components (Fe, Co, Ni) from the alloys.     

Phosphazene-based ionic liquids: synthesis, temperature-dependent viscosity, and effect as additives in water lubrication of silicon nitride ceramics

Phosphazene rings with (dimethylamino)ethoxy (1, 2), pyridylmethoxy (3), or (dimethylamino)propoxy (4) chains were synthesized and quaternized at the substitutent nitrogen by treatment with methyl iodide at 35 degrees C over 3-6 h to give polyiodo salts, 5-8. Subsequent metathesis with LiN(SO(2)CF(3))(2) or NaBF(4) gave the respective ionic salts, 9-13. The amide salts, 9-12, were viscous liquids with pour points at 55-100 degrees C, and the tetrafluoroborate salt, 13, was a solid, mp 168 degrees C. The compositions of 2 and 5-13 were confirmed by elemental analysis and spectroscopic methods. Compounds 1, 2, and 4 were viscous liquids (d(25) = 1.67 g cm(-3); eta(25) = 0.76-1.56 mPa s(-1) ) with pour points at approximately 15 degrees C. The solid polyquaternary salts, 5-8, melted at 130-194 degrees C. The ionic liquids, 9-12, had an average density of approximately 1.73 g cm(-3) at 25 degrees C, and viscosities (25 degrees C) ranged between 68.3 and 139.2 mPa s(-1). A plot of the viscosities of 9-12 vs temperature revealed an almost linear correlation between 55 and 120 degrees C. Friction and wear properties of water with 0.25 wt % of 9-12 as boundary lubricant additives were evaluated on Si(3)N(4)/Si(3)N(4) ceramic interfaces. The most significant observation is that they caused a decrease in the running-in period.     

Synthesis,structure, and redox properties of the extremely crowded triarylpnictogens: tris(2,4,6-triisopropylphenyl)phosphine,arsine, stibine,and bismuthine

A series of the extremely crowded triarylpnitogens, tris(2,4,6-triisopropylphenyl)phosphine (1), arsine (2), stibine (3), and bismuthine (4), were synthesized by the reaction of 2,4,6-triisopropylphenylcopper(I) with the corresponding pnictogen trichlorides. Introducion of the three bulky aryl groups resulted in the unusual structures and redox properties, which were studied by X-ray crystallography and cyclic voltammetry. The triarylpnictogens 1, 2, and 3 had extremely large bond angles around pnictogen atoms (1: 111.5 degrees , 2: 109.2 degrees , 3: 106.7 degrees ), and not only 1 and 2, but also stibine 3 displayed a reversible redox wave in the cyclic voltammograms at very low potentials (1: 0.16 V, 2: 0.50 V, 3: 0.57 V vs Ag/Ag+), which suggests considerable stability of the corresponding cation radicals.     

Interactive effects of ultraviolet-B radiation and temperature on cotton physiology, growth, development and hyperspectral reflectance

Current conditions of 2-11 kJ m(-2) day(-1) of UV-B radiation and temperatures of >30 degrees C during flowering in cotton cultivated regions are projected to increase in the future. A controlled environment study was conducted in sunlit growth chambers to determine the effects of UV-B radiation and temperature on physiology, growth, development and leaf hyperspectral reflectance of cotton. Plants were grown in the growth chambers at three day/night temperatures (24/16 degrees C, 30/22 degrees C and 36/28 degrees C) and three levels of UV-B radiation (0, 7 and 14 kJ m(-2) day(-1)) at each temperature from emergence to 79 days under optimum nutrient and water conditions. Increases in main stem node number and the node of first fruiting branch and decrease in duration to first flower bud (square) and flower were recorded with increase in temperature. Main effects of temperature and UV-B radiation were significant for net photosynthetic rates, stomatal conductance, total chlorophyll and carotenoid concentrations of uppermost, fully expanded leaves during squaring and flowering. A significant interaction between temperature and UV-B radiation was detected for total biomass and its components. The UV-B radiation of 7 kJ m(-2) day(-1) reduced boll yield by 68% and 97% at 30/22 degrees C and 36/28 degrees C, respectively, compared with yield at 0 kJ m(-2) day(-1) and 30/22 degrees C. No bolls were produced in the three temperature treatments under 14 kJ m(-2) day(-1) UV-B radiation. The first-order interactions between temperature, UV-B radiation and leaf age were significant for leaf reflectance. This study suggests a growth- and process-related temperature dependence of sensitivity to UV-B radiation.     

Spin label studies on rat liver and heart plasma membranes: effects of temperature, calcium, and lanthanum on membrane fluidity.

The structures of rat liver and heart plasma membranes were studied with the 5-nitroxide stearic acid spin probe, I(12,3). The polarity-corrected order parameters (S) of liver and heart plasma membranes were independent of probe concentration only if experimentally determined low I(12,3)/lipid ratios were employed. At higher probe/lipid ratios, the order parameters of both membrane systems decreased with increasing probe concentration, and these effects were attributed to enhanced nitroxide radical interactions. Examination of the temperature dependence of approximate and polarity-corrected order parameters indicated that lipid phase separations occur in liver (between 19 degrees and 28 degrees C) and heart (between 21 degrees and 32 degrees C) plasma membranes. The possibility that a wide variety of membrane-associated functions may be influenced by these thermotropic phase separations is considered. Addition of 3.9 mM CaCl2 to I(12,3)-labeled liver plasma membrane decreased the fluidity as indicated by a 5% increase in S at 37 degrees C. Similarly, titrating I(12,3)-labeled heart plasma membranes with either CaCl2 or LaCl3 decreased the lipid fluidity at 37 degrees C, although the magnitude of the La3+ effect was larger and occurred at lower concentrations than that induced by Ca2+; addition of 0.2 mM La3+ or 3.2 mM Ca2+ increased S by approximately 7% and 5%, respectively. The above cation effects reflected only alterations in the membrane fluidity and were not due to changes in probe--probe interactions. Ca2+ and La3+ at these concentrations decrease the activities of such plasma membrane enzymes as Na+, K+-ATPase and adenylyl cyclase, and it is suggested that the inhibition of these enzymes may be due in part to cation-mediated decreases in the lipid fluidity.     

Synthesis, Characterization, and Thermolysis of C(15)N(12)

Synthesis of 1-methyl-2-fluoro-4,5-dicyanoimidazole was done by halogen exchange between 1-methyl-2-bromo-4,5-dicyanoimidazole and potassium fluoride. Halogen exchange between 1-methyl-2-bromo-4,5-dicyanoimidazole and lithium chloride in N-methylpyrrolidinone at 150 degrees C yielded 1-methyl-2-chloro-4,5-dicyanoimidazole, and additional heating to 210 degrees C resulted in the demethylation to yield 2-chloro-4,5-dicyanoimidazole. Thermolyses of the 2-halo-4,5-dicyanoimidazole derivatives (F, Cl) and 1-iodo-2-halo-4,5-dicyanoimidazole derivatives (Cl, Br, I) between 100 and 290 degrees C were found to yield Tris(imidazo)[1,2-a:1,2-c:1,2-e]-1,3,5-triazine-2,3,5,6,8,9-hexacarbonitrile, or HTT, with (C(5)N(4))(3) composition. HTT has been characterized and purified and the crystal structure obtained. Thermolysis of HTT at 490-500 degrees C gives a material with C/N = 1.020. The thermal properties of HTT and its decomposition products show thermal stability to 350 degrees C.     

Stable competitive enzyme-linked immunosorbent assay kit for rapid measurement of 11 active beta-lactams in milk, tissue, urine, and serum

Beta-lactams are used as veterinary drugs for the treatment of food-producing animals. For consumer protection, legislation is in place to set limits for their residues. An enzyme-linked immunosorbent assay (ELISA) was developed which allowed, in a single reaction, the class-specific measurement of 11 beta-lactams, with limits of detection below European maximum residue limits. Determinations were feasible in milk, tissue, urine, and serum with simple and rapid sample preparation. In this format, the specific capture antibodies were precoated on the microtiter plate and horseradish peroxidase-labeled conjugate was used to compete with free beta-lactams. The stability of the precoated microtiter plate and conjugate was at least 1 year when stored at 2 to 8 degrees C; upon reconstitution, the conjugate was stable for 6 days at 2 to 8 degrees C. The stability of lyophilized ampicillin standards was at least 6 months when stored at 2 to 8 degrees C and at least 1 year when stored at -20 degrees C. A low cross-reactivity, 3.6%, was observed with ampicillin with open beta-lactam ring relative to 100% for intact ampicillin. Generic recognition was shown by relative cross-reactivity values ranging from 22 (penicillin V) to 144% (nafcillin). Cross-reactivity for cephalosporins was <0.1%. Intra- and interassay precisions expressed as coefficient of variation were typically 2-8%. The inhibitory concentration with 50% binding for ampicillin was typically 2 ppb. Recovery for different spiked levels was >70% with all the matrixes.     

Systematic control of size,shape, structure,and magnetic properties of uniform magnetite and maghemite particles

As an application of the gel-sol method especially developed for the synthesis of general monodisperse particles in large quantities, uniform hematite (alpha-Fe2O3), magnetite (Fe3O4), and maghemite (gamma-Fe2O3) particles, precisely controlled in size, aspect ratio, and internal structure, have been prepared. For the synthesis of uniform ellipsoidal single-crystal particles of alpha-Fe2O3, a highly condensed suspension of fine beta-FeOOH particles doped with a prescribed amount of PO4(3-) ion in their interiors was aged at 140 degrees C for 24 h with seed particles of alpha-Fe2O3 in an acidic medium containing optimum concentrations of HCl and NaNO3. Systematic control of the aspect ratio and mean size was achieved by regulating the concentration of PO4(3-) ion incorporated into the beta-FeOOH particles and the number of seeds added. The resulting hematite particles were converted into magnetite by reduction in a H2 stream at 330 degrees C for 6 h; the magnetite was then oxidized to maghemite in an air stream at 240 degrees C for 2 h. Magnetite and maghemite thus prepared retained the original shape of the hematite. On the other hand, polycrystalline hematite particles of different sizes and aspect ratios were also prepared by aging a condensed Fe(OH)3 gel in the presence of different concentrations of SO4(2-) ion and seeds. The polycrystalline hematite particles were similarly converted into magnetite and then maghemite. The magnetic properties of these magnetite and maghemite particles were analyzed as a function of their mean particle volume, aspect ratio, and internal structure.     

Single, binary, and multicomponent sorption of iron and manganese on lignite

Acid mine drainage (AMD) has long been a significant environmental problem resulting from the microbial oxidation of iron pyrite in the presence of water and air, affording an acidic solution that contains toxic metal ions. The main objective of this study was to remove metal ions [Fe(II), Fe(III), Mn(II), Zn(II)] from AMD using lignite, a low-cost adsorbent. The lignite sorbent was utilized for the sorption of ferrous, ferric, manganese, zinc, and calcium ions in aqueous solutions. Studies were performed at different pH to find optimum pH. Equilibrium isotherms were determined to assess the maximum adsorption capacity of lignite for different metal ions. Sorption capacities were compared in single, binary, ternary, and multicomponent systems. The sorption data are correlated with Freundlich and Langmuir isotherms in each system. Both Freundlich and Langmuir isotherms fit the data reasonably well in terms of regression coefficients. Sorption studies were also performed at different temperatures to obtain the thermodynamic parameters of the process. The maximum lignite adsorption capacities at 25 degrees C were 34.22, 25.84, and 11.90 mg/g for Fe(II), Mn(II), and Fe(III), respectively. Adsorption of Fe(2+) (24.70 mg/g at 10 degrees C and 46.46 mg/g at 40 degrees C) increased with increased temperature, while Mn(2+) adsorption (28.11 mg/g at 10 degrees C and 7.70 mg/g at 40 degrees C) decreased with increased temperature.     

Controlled synthesis of high-quality PbS star-shaped dendrites, multipods, truncated nanocubes, and nanocubes and their shape evolution process

Well-defined single-crystalline PbS nano- and microstructures including dendrites, multipods, truncated nanocubes, and nanocubes were synthesized in high yield by a simple solution route. Novel star-shaped PbS dendrites with six symmetric arms along the 100 direction, each of which shows one trunk (long axis) and four branches (short axes), have been achieved using Pb(AC)2 and thioacetamide (TAA) as precursors, under the molar ratio Pb(AC)2/TAA = 2/1, at initial reaction temperature 80 degrees C, refluxing for 30 min at 100 degrees C, in the presence of cetyltrimethylammonium bromine (CTAB). The "nanorods" in each branch are parallel to each other in the same plane and are perpendicular to the trunk. The truncated nanocubes mainly bounded by the {100} plane were prepared under a different Pb(AC)2/TAA molar ratio, at initial reaction temperature 40 degrees C, refluxing for 12 h at 100 degrees C. Based on the systematic studies on their shape evolution, a possible growth mechanism of these PbS nano- and microstructures was proposed. The shapes of PbS nanocrystals with face-centered cubic (fcc) structure are mainly determined by the ratio (R) between the growth rates along the (100) and (111) directions. The Pb(AC)2/TAA molar ratio and the initial reaction temperature influence the growth ratio R in the formation of PbS nuclei at an early stage, which results in the final morphology of PbS nanocrystals. Under the current experimental conditions, we can control the PbS shape evolution by simply tuning the molar ratio, the initial reaction temperature, and the period of reaction. Based on the systematic studies on the shape evolution, this approach is expected to be employed for the control-shaped synthesis of other fcc structural semiconductor nanomaterials. The photoluminescence properties were investigated and the prepared nano- and microstructures displayed a very strong luminescence around 600-650 nm at room temperature.     

Chain orientation and headgroup structure in Langmuir monolayers of stearic acid and metal stearate (Ag, Co, Zn, and Pb) studied by infrared reflection-absorption spectroscopy

The monolayers of stearic acid at the air-water interface on pure water and ion-containing subphases have been studied using infrared reflection-absorption spectroscopy. In the presence of Co(2+), Zn(2+), and Pb(2+), ordered hydrocarbon chains and hexagonal subcell structure remain almost unchanged in comparison with those for the monolayer on pure water at the surface pressure of 20 m/Nm. In the cases of Co(2+) and Zn(2+), the H-bonded monodentate and unsymmetric bidentate chelating structure within the headgroups were formed, and in the case of Pb(2+), three types of structures, bidentate chelating, unsymmetric chelating, and bidentate bridging coordinations, were formed. The hydrocarbon chains in the monolayers are uniaxially oriented at a tilt angle of approximately 0 degrees with respect to the surface normal in contrast to a tilt angle of approximately 20 degrees on pure water surface at 20 m/Nm by the computer simulation of theoretical calculation to experimental data. In the presence of Ag(+), multilayers were developed with the highly ordered hydrocarbon chains in a triclinic subcell structure and a bidentate bridging structure within the headgroups. The multilayers were composed of three monolayers and the hydrocarbon chains in each monolayer were oriented at an angle of approximately 30 degrees away from the surface normal with their C-C-C planes almost perpendicular to the water surface.     

Surface Pressure, Hysteresis, Interfacial Tension, and CMC of Four Sorbitan Monoesters at Water-Air, Water-Hexane, and Hexane-Air Interfaces

The hydrophobicity of fine particles is important for their behavior at interfaces, for example, in stabilizing emulsions. In this study, contact angles were evaluated for silanized fumed silica nanospheres with mean primary diameter of about 12 nm, using heat flow microcalorimetry. Three systems were investigated: water-air-nanospheres, toluene-air-nanospheres, and toluene-water-nanospheres. For the water-air-nanospheres system, n-propanol at various concentrations in water was used to aid in dispersing the nanospheres, and the enthalpy of immersion between water, air, and nanospheres was obtained by extraploting to zero n-propanol concentration. Measurements of enthalpy of immersion for toluene-air-nanospheres system were straightforward, as all the nanospheres samples were dispersible in toluene. The enthalpy of immersion for toluene-water-nanospheres system was calculated from the data for the aforementioned first and the second systems. For water-air-nanosphere systems, contact angles were in the range of 14 to 118 degrees, corresponding to enthalpy of immersion from -0.0905 to 0.0041 J/m(2). For the case of toluene-air-nanospheres systems, the contact angles varied from 72 to 94 degrees with corresponding enthalpy of immersion from -0.0295 to -0.0189 J/m(2). For toluene-water-nanospheres systems, however, contact angles were in the range of 0 to 96 degrees, corresponding to enthalpy of immersion from -0.0717 to -0.0175 J/m(2). Copyright 2000 Academic Press.     

Low melting inorganic salts of alkyl-, fluoroalkyl-, alkyl ether-, and fluoroalkyl ether-substituted oxazolidine and morpholine

N-Alkyl- and N-fluoroalkyl-substituted oxazolidinium- and morpholinium-based quaternary salts and ionic liquids have been synthesized and characterized. Reactions of N-methyloxazolidine (1) or N-methylmorpholine (2) with 3-fluoropropyl bromide or iodopropane in THF at 25 degrees C gave the quaternary salts (3a,b, 4a,b). These salts were metathesized with various metal salts to yield the corresponding ionic liquids (5a-h, 6a-i). N-Alkoxyethyl- and N-(fluoroalkoxy)ethyl-substituted morpholines (8-11) were prepared and quaternized with methyl iodide (8a-11a). Their corresponding ionic liquids (12-18) were obtained by anion exchange and characterized. For both series of compounds, nitrate, hexafluorophosphate, perchlorate, triflate, and bis(trifluoromethanesulfonyl)amide were utilized. Most of the final products are liquids at 25 degrees C and are thermally stable with long liquid ranges as determined by thermal gravimetric analyses. For compounds 12, 16, and 18, thermal stabilities of > or =400 degrees C were observed. All the new compounds were characterized by spectroscopic and elemental analyses. Their densities and viscosities were also determined.     

Equilibrium and kinetics studies of reactions of manganese acetate, cobalt acetate, and bromide salts in acetic acid solutions

The oxidation of hydrogen bromide and alkali metal bromide salts to bromine in acetic acid by cobalt(III) acetate has been studied. The oxidation is inhibited by Mn(OAc)(2) and Co(OAc)(2), which lower the bromide concentration through complexation. Stability constants for Co(II)Br(n)() were redetermined in acetic acid containing 0.1% water as a function of temperature. This amount of water lowers the stability constant values as compared to glacial acetic acid. Mn(II)Br(n)() complexes were identified by UV-visible spectroscopy, and the stability constants for Mn(II)Br(n)() were determined by electrochemical methods. The kinetics of HBr oxidation shows that there is a new pathway in the presence of M(II)Br(n)(). Analysis of the concentration dependences shows that CoBr(2) and MnBr(2) are the principal and perhaps sole forms of the divalent metals that react with Co(III) and Mn(III). The interpretation of these data is in terms of this step (M, N = Mn or Co): M(OAc)(3) + N(II)Br(2) + HOAc --> M(OAc)(2) + N(III)Br(2)OAc. The second-order rate constants (L mol(-)(1) s(-)(1)) for different M, N pairs in glacial acetic acid are 4.8 (Co, Co at 40 degrees C), 0.96 (Mn, Co at 20 degrees C), 0.15 (Mn(III).Co(II), Co at 20 degrees C), and 0.07 (Mn, Mn at 20 degrees C). Following that, reductive elimination of the dibromide radical is proposed to occur: N(III)Br(2)OAc + HOAc --> N(OAc)(2) + HBr(2)(*). This finding implicates the dibromide radical as a key intermediate in this chemistry, and indeed in the cobalt-bromide catalyzed autoxidation of methylarenes, for which some form of zerovalent bromine has been identified. The selectivity for CoBr(2) and MnBr(2) is consistent with a pathway that forms this radical rather than bromine atoms which are at a considerably higher Gibbs energy. Mn(OAc)(3) oxidizes PhCH(2)Br, k = 1.3 L mol(-)(1) s(-)(1) at 50.0 degrees C in HOAc.     

Apparent and standard partial molar volumes of NaCl, NaOH, and HCl in water and heavy water at T = 523 K and 573 K at p = 14 MPa

Apparent molar volumes, Vphi,2, of aqueous NaCl, NaOH, NaOD, HCl, and DCl in water and heavy water were determined at T = 523 and 573 K and p = 14 MPa with a high-temperature platinum vibrating-tube densimeter in the aquamolality range 0.25 相似文献   

Single, binary and multi-component adsorption of copper and cadmium from aqueous solutions on Kraft lignin--a biosorbent

A new biosorbent for removing toxic metal ions from water/industrial wastewater has been investigated using by-product lignin from paper production. Lignin was extracted from black liquor waste, characterized and utilized for the removal of copper and cadmium from aqueous solutions in single, binary and multi-component systems. Adsorption studies were conducted at different temperatures, lignin particle sizes, pHs and solid to liquid ratios. All the studies were conducted by a batch method to determine equilibrium and kinetic parameters. The Langmuir and Freundlich isotherm models were applied. The Langmuir model fits best the equilibrium isotherm data. The maximum lignin adsorption capacities at 25 degrees C were 87.05 mg/g (1.37 mmol/g) and 137.14 mg/g (1.22 mmol/g) for Cu(II) and Cd(II), respectively. Adsorption of Cu2+ (68.63 mg/g at 10 degrees C and 94.68 mg/g at 40 degrees C) and Cd2+ (59.58 mg/g at 10 degrees C and 175.36 mg/g at 40 degrees C) increased with an increase in temperature. Copper and cadmium adsorption followed pseudo-second order rate kinetics. From kinetic studies, various rate and thermodynamic parameters such as effective diffusion coefficients, activation energy, and activation entropy were evaluated. Adsorption occurs through a particle diffusion mechanism at temperatures 10 and 25 degrees C while at 40 degrees C it occurs through a film diffusion mechanism. The sorption capacity of black liquor lignin is higher than many other adsorbents/carbons/biosorbents utilized for the removal of Cu(II) and Cd(II) from water/wastewater in single and multi-component systems.     

Syntheses,structures, and dynamic behavior of chiral racemic organoantimony and -bismuth compounds RR'SbCl,RR'BiCl,and RR'SbM [R = 2-(Me2NCH2)C6H4, R' = CH(Me3Si)2, M = H,Li, Na

RR'SbCl (1) and RR'BiCl (2) [R = 2-(Me(2)NCH(2))C(6)H(4), R' = CH(Me(3)Si)(2)] form by the reaction of R'ECl(2) (E = Sb, Bi) with RLi. The reaction of 1 with LiAlH(4) and metalation with n-BuLi gives RR'SbH (3) and RR'SbLi.2THF (4) (THF = tetrahydrofuran). Transmetalation of 4 with sodium tert-butoxide in the presence of TMEDA (TMEDA = tetramethylethylenediamine) leads to RR'SbNa.TMEDA (5). Structural analyses by (1)H NMR in C(6)D(6), C(6)D(5)CD(3), or (CD(3))(2)SO with a variation of the temperature (1, 2, 4, and 5) and by single-crystal X-ray diffraction (1, 2, 4, and 5) revealed the intramolecular coordination of the pendant Me(2)N group on the pnicogen centers in 1 and 2 and on Li or Na in 4 or 5. The variable-temperature (1)H NMR spectra of the hydride 3 in C(6)D(6), C(6)D(5)CD(3), or (CD(3))(2)SO show that the pyramidal configuration on antimony is stable up to 100 degrees C, whereas inversion at the nitrogen is not prevented by internal coordination even at -80 degrees C. The crystals of 1, 2, 4, and 5 consist of discrete molecules with the Sb and Bi atoms in an approximately Psi-trigonal-bipyramidal environment in the cases of 1 and 2 and in a pyramidal environment in the cases of 4 and 5. Crystal data for 1: triclinic, space group Ponemacr;, a = 7.243(4) A, b = 10.373(3) A, c = 15.396(5) A, alpha = 79.88 degrees, beta = 78.27 degrees, gamma = 71.480(10) degrees, V = 1066.2(7) A(3), Z = 2, R = 0.0614. 2: monoclinic, space group P2(1)/n, a = 10.665(2) A, b = 14.241(2) A, c = 14.058(2) A, beta = 90.100(10) degrees, V = 2135.1(6) A(3), Z = 4, R = 0.049. 4: monoclinic, space group P2(1)/n, a = 11.552(2) A, b = 16.518(3) A, c = 15.971(5) A, beta = 96.11(2) degrees, V = 3030.2(12) A(3), Z = 4, R = 0.0595. 5: monoclinic, space group P2(1)/n, a = 9.797(2) A, b = 24.991(5) A, c = 14.348(3) A, beta = 94.98(3) degrees, V = 3499.66(12) A(3), Z = 4, R = 0.0571. The dissociation of the intramolecular N-pnicogen bond and inversion at the nitrogen occurs when solutions of 1 or 2 in C(6)D(6) or C(6)D(5)CD(3) are heated above 25 or 30 degrees C. 1 and 3-5 are stable with respect to inversion of the configuration at the antimony in C(6)D(6), C(6)D(5)CD(3), or (CD(3))(2)SO up to 160 degrees C. Bismuth inversion, probably via the edge mechanism, is observed in solutions of 2 in (CD(3))(2)SO at 45 degrees C but not in C(6)D(5)CD(3) below 125 degrees C.     

Gas chromatographic study of volatile oxides and hydroxides of Tc, Re, Ru, Os and Ir-I Investigation by isothermal gas chromatography

Traces of radioactive elements were produced by the irradiation of uranium foils (93% (235)U) with thermal neutrons, and of gold foils with 600-MeV protons. They were volatilized as oxides and hydroxides by heating at 1500 degrees in an O(2) or O(2)/H(2)O stream and separated by adsorption chromatography on quartz granules. Compounds in the effluent gas were detected with a Ge(Li) detector and the elements identified by gamma-spectrometry.