Highly efficient removal of Sb(V) from water by franklinite-containing nano-FeZn composites.

The existence of toxic and carcinogenic pentavalent antimony in water is a great safety problem. In order to remove antimony(V) from water, the purpose of this study was to prepare a novel graphene nano iron zinc (rGO/NZV-FeZn) photocatalyst via hydrothermal method followed by ultrasonication. Herein, weakly magnetic nano-Fe-Zn materials (NZV-FeZn, GACSP/NZV-FeZn, and rGO/NZV-FeZn) capable of rapid and efficient Sb(V) adsorption from water were prepared and characterised. In particular, rGO/NZV-FeZn was shown to comprise franklinite, Fe0, and graphite. Adsorption data were fitted by a quasi-second-order kinetic equation and Langmuir model, revealing that among these materials, NZV-FeZn exhibited the best Sb removal performance (543.9 mgSb gNZV-FeZn-1, R2 = 0.951). In a practical decontamination test, Sb removal efficiency of 99.38% was obtained for a reaction column filled with 3.5 g of rGO/NZV-FeZn. Column regenerability was tested at an initial concentration of 0.8111 mgSb L-1, and the treated water obtained after five consecutive runs complied with the GB5749-2006 requirement for Sb. rGO/NZV-FeZn was suggested to remove Sb(V) through adsorption-photocatalytic reduction and flocculation sedimentation mechanisms and, in view of its high cost performance, stability, and upscalable synthesis, was concluded to hold great promise for source water and wastewater treatment.

A Superior Na3 V2 (PO4 )3 -Based Nanocomposite Enhanced by Both N-Doped Coating Carbon and Graphene as the Cathode for Sodium-Ion Batteries.

A superior Na3 V2 (PO4 )3 -based nanocomposite (NVP/C/rGO) has been successfully developed by a facile carbothermal reduction method using one most-common chelator, disodium ethylenediamintetraacetate [Na2 (C10 H16 N2 O8 )], as both sodium and nitrogen-doped carbon sources for the first time. 2D-reduced graphene oxide (rGO) nanosheets are also employed as highly conductive additives to facilitate the electrical conductivity and limit the growth of NVP nanoparticles. When used as the cathode material for sodium-ion batteries, the NVP/C/rGO nanocomposite exhibits the highest discharge capacity, the best high-rate capabilities and prolonged cycling life compared to the pristine NVP and single-carbon-modified NVP/C. Specifically, the 0.1 C discharge capacity delivered by the NVP/C/rGO is 116.8 mAh g(-1) , which is obviously higher than 106 and 112.3 mAh g(-1) for the NVP/C and pristine NVP respectively; it can still deliver a specific capacity of about 80 mAh g(-1) even at a high rate up to 30 C; and its capacity decay is as low as 0.0355 % per cycle when cycled at 0.2 C. Furthermore, the electrochemical impedance spectroscopy was also implemented to compare the electrode kinetics of all three NVP-based cathodes including the apparent Na diffusion coefficients and charge-transfer resistances.

Romanechite-structured Na(0.31)MnO(1.9) nanofibers as high-performance cathode material for a sodium-ion battery.

A new cathode material composed of romanechite-structured Na(0.31)MnO(1.9) nanofibers is developed for sodium-ion batteries for the first time. It can deliver a Na-uptake capacity of >100 mA h g(-1) with a superior high-rate capability and good cycling performance in the voltage range of 2-4.5 V vs. Na(+)/Na, and exhibit the unique ability of fast charging with the normal discharge rate.

Theoretical Studies of the Reactions CFx H3-x COOR+Cl and CF3 COOCH3 +OH.

The mechanism and kinetics of the reactions of CF(3)COOCH(2)CH(3), CF(2)HCOOCH(3), and CF(3)COOCH(3) with Cl and OH radicals are studied using the B3LYP, MP2, BHandHLYP, and M06-2X methods with the 6-311G(d,p) basis set. The study is further refined by using the CCSD(T) and QCISD(T)/6-311++G(d,p) methods. Seven hydrogen-abstraction channels are found. All the rate constants, computed by a dual-level direct method with a small-curvature tunneling correction, are in good agreement with the experimental data. The tunneling effect is found to be important for the calculated rate constants in the low-temperature range. For the reaction of CF(3)COOCH(2)CH(3) +Cl, H-abstraction from the CH(2) group is found to be the dominant reaction channel. The standard enthalpies of formation for the species are also calculated. The Arrhenius expressions are fitted within 200-1000 K as kT(1) =8.4×10(-20) T (2.63) exp(381.28/T), kT(2) =2.95×10(-21) T (3.13) exp(-103.21/T), kT(3) =1.25×10(-23) T (3.37) exp(791.98/T), and kT(4) =4.53×10(-22) T (3.07) exp(465.00/T).

Theoretical study on the reactions of (CF3)2CFOCH3 + OH/Cl and reaction of (CF3)2CFOCHO with Cl atom.

Reactions of (CF3)2CFOCH3 and (CF3)2CFOCHO with hydroxyl radical and chlorine atom are studied at the B3LYP and BHandHLYP/6-311+G(d,p) levels along with the geometries and frequencies of all stationary points. This study is further refined by CCSD(T) and QCISD(T)/6-311+G(d,p) methods in the minimum energy paths. For the reaction (CF3)2CFOCH3 + OH, two hydrogen abstraction channels are found. The total rate constants for the reactions (CF3)2CFOCH3 + OH/Cl and (CF3)2CFOCHO + Cl are followed by means of the canonical variational transition state with the small-curvature tunneling correction. The comparison between the hydrogen abstraction rate constants by hydroxyl and chlorine atom is discussed. Calculated rate constants are in reasonable agreement with the available experiment data. The standard enthalpies of formation for the reactants, (CF3)2CFOCH3 and (CF3)2CFOCHO, and two products, (CF3)2CFOCH2 and (CF3)2CFOCO, are evaluated by a series of isodesmic reactions. The Arrhenius expressions for the title reactions are given as follows: k1= 1.08 × 10(-22) T(3.38) exp(-213.31/T), k2= 3.55 × 10(-22) T(3.61) exp(-240.26/T), and k3= 3.00 × 10 (-19) T(2.58) exp(-1294.34/T) cm(3) molecule(-1) s(-1).

From pure C36 fullerene to cagelike nanocluster: a density functional study.

The geometrical structures, energetics properties, and aromaticity of C(36-n) Si(n) (n ≤ 18) fullerene-based clusters were studied using density functional theory calculations. The geometries of C(36-n) Si(n) clusters undergo strong structural deformation with the increase of Si substitution. For the most energy favorable structures of C(36-n) Si(n) , the silicon and carbon atoms form two distinct homogeneous segregations. Subsequently, the binding energy, HOMO-LUMO energy gap, vertical ionization potential, vertical electron affinity, and chemical hardness for the energetic favorable C(36-n) Si(n) geometries were computed and analyzed. In addition, the aromatic property of C(36-n) Si(n) cagelike clusters was investigated, and the result demonstrate that these C(36-n) Si(n) cagelike structures possess strong aromaticity.

Electronic structures and optical properties of the IPR-violating C60X8 (X = H, F, and Cl) fullerene compounds: a computational study.

Stimulated by the preparation and characterization of the isolated pentagon rule (IPR) violating chlorofullerene: C(60)Cl(8) (Nat. Mater. 2008, 7, 790-794), we have performed a systematic investigation on the structural stabilities, electronic and optical properties of the IPR-violating C(60)X(8) (X = H, F, and Cl) fullerene compounds via density functional theory. The large energy gaps between the highest occupied and the lowest unoccupied molecular orbitals provide a clear indication of high chemical stabilities of C(60)X(8) derivatives, and moreover, the C(60)X(8) molecules present great aromatic character with the negative nucleus independent chemical shift values. In the addition reactions of C(60) (C(2v)) + 4X(2) → C(60)X(8), a series of exothermic processes are involved, with high reaction energies ranging from -71.97 to -233.16 kcal mol(-1). An investigation on the electronic property shows that C(60)F(8) and C(60)Cl(8) could be excellent electron acceptors as a consequence of large vertical electron affinities. The density of state analysis suggests that the frontier molecular orbitals of C(60)X(8) are mainly from the carbon orbitals of two separate annulene subunits, and the influence from X atoms is secondary. In addition, the ultraviolet-visible spectra and second-order hyperpolarizabilities of C(60)X(8) are calculated by means of time-dependent density functional theory and a finite field approach, respectively. Both the average static linear polarizability <α> and second-order hyperpolarizability <γ> of C(60)X(8) increase greatly compared to those of C(60).

Thermochemical stabilities, electronic structures, and optical properties of C56X10 (X = H, F, and Cl) fullerene compounds.

Stimulated by the recent isolation and characterization of C56Cl10 chlorofullerene (Tan et al., J Am Chem Soc 2008, 130, 15240), we perform a systematic study on the geometrical structures, thermochemistry, and electronic and optical properties of C56X10 (X = H, F, and Cl) on the basis of density functional theory (DFT). Compared with pristine C56, the equatorial carbon atoms in C56X10 are saturated by X atoms and change to sp³ hybridization to release the large local strains. The addition reactions C56 + 5X2 --> C56X10 are highly exothermic, and the optimal temperature for synthesizing C56X10 should be ranged between 500 and 1000 K. By combining 10 X atoms at the abutting pentagon vertexes and active sites, C56Cl10 molecules exhibit large energy gaps between the highest occupied and lowest unoccupied molecular orbitals (from 2.84 to 3.00 eV), showing high chemical stabilities. The C56F10 and C56Cl10 could be excellent electron acceptors for potential photonic/photovoltaic applications in consequence of their large vertical electron affinities. The density of states is also calculated, which suggest that the frontier molecular orbitals of C56X10 are mainly from the carbon orbitals of two separate annulene subunits, and the contributions derived from X atoms are secondary. In addition, the ultraviolet-visible spectra and second-order hyperpolarizabilities of C56X10 are calculated by means of time-dependent DFT and finite field approach, respectively. Both the average static linear polarizability <α> and second-order hyperpolarizability <γ> of these compounds are larger than those of C60 due to lower symmetric structures and high delocalization of π electron density on the two separate annulene subunits.

Electronic structures and nonlinear optical properties of highly deformed halofullerenes C(3v) C60F18 and D(3d) C60Cl30.

Electronic structures and nonlinear optical properties of two highly deformed halofullerenes C(3v) C(60)F(18) and D(3d) C(60)Cl(30) have been systematically studied by means of density functional theory. The large energy gaps (3.62 and 2.61 eV) between the highest occupied and lowest unoccupied molecular orbitals (HOMOs and LUMOs) and the strong aromatic character (with nucleus-independent chemical shifts varying from -15.08 to -23.71 ppm) of C(60)F(18) and C(60)Cl(30) indicate their high stabilities. Further investigations of electronic property show that C(60)F(18) and C(60)Cl(30) could be excellent electron acceptors for potential photonic/photovoltaic applications in consequence of their large vertical electron affinities. The density of states and frontier molecular orbitals are also calculated, which present that HOMOs and LUMOs are mainly distributed in the tortoise shell subunit of C(60)F(18) and the aromatic [18] trannulene ring of C(60)Cl(30), and the influence from halogen atoms is secondary. In addition, the static linear polarizability and second-order hyperpolarizability of C(60)F(18) and C(60)Cl(30) are calculated using finite-field approach. The values of and for C(60)F(18) and C(60)Cl(30) molecules are significantly larger than those of C(60) because of their lower symmetric structures and high delocalization of pi electrons.

Computational studies on the mechanism and kinetics of Cl reaction with C2H5I.

The dual-level direct kinetics method has been used to investigate the multichannel reactions of C(2)H(5)I + Cl. Three hydrogen abstraction channels and one displacement process are found for the title reaction. The calculation indicates that the hydrogen abstraction from -CH(2)- group is the dominant reaction channel, and the displacement process may be negligible because of the high barrier. The rate constants for individual reaction channels are calculated by the improved canonical variational transition-state theory with small-curvature tunneling correction over the temperature range of 220-1500 K. Our results show that the tunneling correction plays an important role in the rate constant calculation in the low-temperature range. Agreement between the calculated and experimental data available is good. The Arrhenius expression k(T) = 2.33 x 10(-16) T(1.83) exp(-185.01/T) over a wide temperature range is obtained. Furthermore, the kinetic isotope effects for the reaction C(2)H(5)I + Cl are estimated so as to provide theoretical estimation for future laboratory investigation.

Structural stability and electronic property of C68X4 (X=H, F, and Cl) fullerene compounds.

A systematic study on the geometrical structures and electronic properties of C(68)X(4) (X=H, F, and Cl) fullerene compounds has been carried out on the basis of density functional theory. In all classical C(68)X(4) isomers with two adjacent pentagons and one quasifullerene isomer [C(s):C(68)(f)] containing a heptagon in the framework, the C(s):0064 isomers are most favorable in energy. The addition reaction energies of C(68)X(4) (C(s):0064) are high exothermic, and C(68)F(4) is more thermodynamically accessible. The C(68)X(4) (C(s):0064) possess strong aromatic character, with nucleus independent chemical shifts ranging from -22.0 to -26.1 ppm. Further investigations on electronic properties indicate that C(68)F(4) and C(68)Cl(4) could be excellent electron-acceptors for potential photonic/photovoltaic applications in consequence of their large vertical electron affinities (3.29 and 3.15 eV, respectively). The Mulliken charge populations and partial density of states are also calculated, which show that decorating C(68) fullerene with various X atoms will cause remarkably different charge distributions in C(68)X(4) (C(s):0064) and affect their electronic properties distinctly. Finally, the infrared spectra of the most stable C(68)X(4) (C(s):0064) molecules are simulated to assist further experimental characterization.

Search for the most stable Ca@C44 isomer: structural stability and electronic property investigations.

Stimulated by the mass spectroscopic observation of the metallofullerene Ca@C(44), we have performed a systematic investigation to search for the most stable isomer using HF/3-21G approximately LanL2DZ, HF/6-31+G(d), B3LYP/6-31+G(d), and MP2/6-31+G(d)//B3LYP/6-31+G(d) methods. The Ca@C(44) (D(2):53) isomer with eight adjacent pentagons in the fullerene framework is predicted to possess the lowest energy. The thermodynamics stability explorations of Ca@C(44) isomers at different temperatures show that Ca@C(44) (D(2):53) is the most thermodynamically stable in the temperature range of absolute zero to 4000 K. The encapsulation of Ca atom in C(44) fullerene is exothermic, and the electronic structure of Ca@C(44) (D(2):53) can be described formally as Ca(2+)@C(44) (2-). Further analysis on the frontier molecular orbitals and density of states of Ca@C(44) (D(2):53) suggests that both highest occupied molecular orbital and lowest unoccupied molecular orbital are carbonlike with low Ca character, and the carbon cage possesses high chemical activity. In addition, the vibrational spectrum of Ca@C(44) (D(2):53) has been simulated and analyzed to gain an insight into the metal-cage vibrations.

Construction of a three-dimensional polynuclear zinc compound based on unique metallophthalocyanine-like subunits.

A polynuclear zinc compound, [Zn(7)(BTA)(7)(OABDC)(mu(3)-OH)(2)(mu(2)-OH)(2).H(2)O] (1), has been prepared by using benzotriazole (HBTA) and 5-oxyacetatoisophthalic acid (H(3)OABDC) as ligands under hydrothermal conditions. For compound 1, an unprecedented metallophthalocyanine-like "Zn(2)(mu(3)-OH)(2) subset [Zn(4)BTA(4)]" subunit is constructed from eta(3)-BTA ligands and Zn atoms and further linked via mu(2)-OH, outer four-connected Zn atoms, and 5-oxyacetateisophthalic acid to form a novel three-dimensional framework.

MP2 theory investigation on the halides of D6hC36:C36Xn (X=F,Cl,Br; n=2,4,6,12).

An investigation of C(36)X(n) (X=F,Cl,Br; n=2,4,6,12) formed from the initial C(36) fullerene with D(6h) symmetry has been performed using the MP2 theory. Their equilibrium structures, reaction energies, strain energies, lowest unoccupied molecular orbital-highest occupied molecular orbital (LUMO-HOMO) gap energies, and aromaticities have been studied. The calculation results showed that those addition reaction were highly exothermic and C(36)X(n) were more stable than C(36). Moreover, from the view of thermodynamics it should be possible to detect C(36)X(6). The LUMO-HOMO gap energies of C(36)X(n) were higher than D(6h)C(36) and the redox characteristics of C(36)X(n) were weaker comparing to D(6h)C(36). The analyses of pi-orbital axis vector indicated that the chemical reactivity of C(36) was the result of the high strain, and the nucleus independent chemical shifts research showed that the stabilities of the C(36)X(6) were correlative with the conjugation effect.

[Occupational exposure profiles of polycyclic aromatic hydrocarbons in coke oven workers].

OBJECTIVE: To study the characteristics of occupational exposure of polycyclic aromatic hydrocarbons (PAHs) in coke oven workers. METHODS: Samples were collected individually and PAHs concentration in the ambient air were assayed by high performance liquid chromatography (HPLC) and toxic equivalency factors (TEFs) were introduced to assess the carcinogenic potency. RESULTS: The levels of PAHs occupational exposure in oven workers at topside was higher than at side oven and bottom oven (P < 0.05). Non-carcinogenic PAHs were more than 70% of total PAHs and benzo[a]pyrene accounted for 65.5% approximately 72.4% of total benzo[a]pyrene equivalents. Total occupational exposure level of PAHs in coke oven workers was positively related to the content of benzo[a]pyrene and pyrene, respectively (r(2) = 0.84, r(2) = 0.94, P < 0.05). CONCLUSION: Coke oven workers were exposed to a high level of PAHs which possessed some extent of carcinogenic potency, and benzo[a]pyrene is the chief carcinogenic substance.