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ABSTRACT: A promising technique called chemical absorption-biological reduction (CABR) integrated approach has been developed recently for the nitrogen oxides (NO(x)) removal from flue gases. The major challenge for this approach is how to enhance the rate of the biological reduction step. To tackle the challenge, a three-dimensional biofilm-electrode reactor (3D-BER) was utilized. This reactor provides not only considerable amount of sites for biofilm, but also many electron donors for bio-reduction. Factors affecting the performance of 3D-BER were optimized, including material of the third electrode (graphite), glucose concentration (1000mg•L(-1)), and volume current density (30.53 A•m(-3) NCC). Experimental results clearly demonstrated that this method significantly promotes the bio-reduction rate of Fe(II)EDTA-NO (0.313 mmol•L(-1)•h(-1)) and Fe(III)EDTA (0.564 mmol•L(-1)•h(-1))simultaneously. Experiments on the mechanism showed that Fe(II)EDTA serves as the primary electron donor in the reduction of Fe(II)EDTA-NO while the reduction of Fe(III)EDTA took advantage of both glucose and electrolysis-generated H(2) as electron donors. High concentration of Fe(II)EDTA-NO or Fe(III)EDTA interferes the bio-reduction of the other one. The proposed methodology shows a promising prospect for NO(x) removal from flue gas.
Environmental Science & Technology 12/2012; · 4.80 Impact Factor
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ABSTRACT: Biodesulfurization is regarded as a promising alternative technology for desulfurization from diesel oil due to its mild operating conditions and its ability to remove sulfur from alky dibenzothiophenes (C(x)-DBTs). The diesel oil contains complex mixtures of C(x)-DBTs in which individual microbial biodesulfurization may be altered. In this work, interactions among three typical C(x)-DBTs such as dibenzothiophenes (DBT), 4-methyldibenzothiophene (4-MDBT), and 4,6-dimethyldibenzothiophene (4,6-DMDBT) were investigated using Mycobacterium sp. ZD-19 in an airlift reactor. The experimental results indicated that the desulfurization rates would decrease in the multiple C(x)-DBTs system compared to the single C(x)-DBT system. The extent of inhibition depended upon the substrate numbers, concentrations, and affinities of the co-existing substrates. For example, compared to individual desulfurization rate (100 %), DBT desulfurization rate decreased to 75.2 % (DBT + 4,6-DMDBT), 64.8 % (DBT + 4-MDBT), and 54.7 % (DBT + 4,6-DMDBT + 4-MDBT), respectively. This phenomenon was caused by an apparent competitive inhibition of substrates, which was well predicted by a Michaelis-Menten competitive inhibition model.
Applied Microbiology and Biotechnology 04/2012; · 3.42 Impact Factor
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ABSTRACT: Biological reduction of nitric oxide (NO) from Fe(II) ethylenediaminetetraacetic acid (EDTA)-NO to dinitrogen (N2) is a core process for the continual nitrogen oxides (NO
x
) removal in the chemical absorption–biological reduction integrated approach. To explore the biological reduction of Fe(II)EDTA-NO,
the stoichiometry and mechanism of Fe(II)EDTA-NO reduction with glucose or Fe(II)EDTA as electron donor were investigated.
The experimental results indicate that the main product of complexed NO reduction is N2, as there was no accumulation of nitrous oxide, ammonia, nitrite, or nitrate after the complete depletion of Fe(II)EDTA-NO.
A transient accumulation of nitrous oxide (N2O) suggests reduction of complexed NO proceeds with N2O as an intermediate. Some quantitative data on the stoichiometry of the reaction are experimental support that reduction
of complexed NO to N2 actually works. In addition, glucose is the preferred and primary electron donor for complexed NO reduction. Fe(II)EDTA served
as electron donor for the reduction of Fe(II)EDTA-NO even in the glucose excessive condition. A maximum reduction capacity
as measured by NO (0.818mM h−1) is obtained at 4mM of Fe(II)EDTA-NO using 5.6mM of glucose as primary electron donor. These findings impact on the understanding
of the mechanism of bacterial anaerobic Fe(II)EDTA-NO reduction and have implication for improving treatment methods of this
integrated approach.
Applied Microbiology and Biotechnology 04/2012; 79(4):537-544. · 3.42 Impact Factor
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ABSTRACT: The biological reduction of Fe(III) ethylenediaminetetraacetic acid (EDTA) is a key step for NO removal in a chemical absorption–biological
reduction integrated process. Since typical flue gas contain oxygen, NO2
− and NO3
− would be present in the absorption solution after NO absorption. In this paper, the interaction of NO2
−, NO3
−, and Fe(III)EDTA reduction was investigated. The experimental results indicate that the Fe(III)EDTA reduction rate decrease
with the increase of NO2
− or NO3
− addition. In the presence of 10mM NO2
− or NO3
−, the average reduction rate of Fe(III)EDTA during the first 6-h reaction was 0.076 and 0.17mM h−1, respectively, compared with 1.07mM h−1 in the absence of NO2
− and NO3
−. Fe(III)EDTA and either NO2
− or NO3
− reduction occurred simultaneously. Interestingly, the reduction rate of NO2
− or NO3
− was enhanced in presence of Fe(III)EDTA. The inhibition patterns observed during the effect of NO2
− and NO3
− on the Fe(III)EDTA reduction experiments suggest that Escherichia coli can utilize NO2
−, NO3
−, and Fe(III)EDTA as terminal electron acceptors.
Applied Microbiology and Biotechnology 04/2012; 82(3):557-563. · 3.42 Impact Factor
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ABSTRACT: Biological reduction of nitric oxide (NO), chelated by ferrous L (L: chelate reagent), to N2 is one of the core processes in a chemical absorption-biological reduction integrated technique for nitrogen oxide (NOx) removal from flue gases. In this study, a newly isolated strain, Pseudomonas sp., was used to reduce NO chelated by Fe(II)Cit (Cit: citrate) as Fe(II)Cit-NO, and some factors were investigated. The results showed that, at the NO concentration of 670 mg/m3, 65.9% of NO was totally reduced within 25 h under anaerobic conditions, and the optimal conditions for the bioreduction of NO were found. The strain of Pseudomonas sp. could efficiently use glucose as the carbon source for Fe(II)Cit-NO reduction. Though each complex could be reduced by its own dedicated bacterial strain, Fe(III)Cit could also be reduced by the strain of Pseudomonas sp. The nitrite ion, NO2-, could inhibit cell growth and thus affect the Fe(III) reduction process. These findings provide some useful data for Fe(II)Cit-NO reduction, scrubber solution regeneration and NOx removal process design.
Environmental Technology 12/2011; 33(15-16):1947-53. · 1.41 Impact Factor
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Progress in Chemistry -Beijing- 09/2011; 23(12):2567-2578. · 0.56 Impact Factor
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ABSTRACT: A promising chemical absorption-biological reduction integrated process has been proposed. A major problem of the process is oxidation of the active absorbent, ferrous ethylenediaminetetraacetate (Fe(II)EDTA), to the ferric species, leading to a significant decrease in NO removal efficiency. Thus the biological reduction of Fe(III)EDTA is vitally important for the continuous NO removal. Oxygen, an oxidizing agent and biological inhibitor, is typically present in the flue gas. It can significantly retard the application of the integrated process. This study investigated the influence mechanism of oxygen on the regeneration of Fe(II)EDTA in order to provide insight on how to eliminate or decrease the oxygen influence. The experimental results revealed that the dissolved oxygen and Fe(III)EDTA simultaneously served as electron acceptor for the microorganism. The Fe(III)EDTA reduction activity were directly inhibited by the dissolved oxygen. When the bioreactor was supplied with 3% and 8% oxygen in the gas phase, the concentration of initial dissolved oxygen in the liquid phase was 0.28 and 0.68 mg l(-1). Correspondingly, the instinct Fe(III)EDTA reduction activity of the microorganism determined under anoxic condition in a rotation shaker decreased from 1.09 to 0.84 and 0.49 mM h(-1). The oxidation of Fe(II)EDTA with dissolved oxygen prevented more dissolved oxygen access to the microorganism and eased the inhibition of dissolved oxygen on the microorganisms.
Applied Microbiology and Biotechnology 09/2011; 93(6):2653-9. · 3.42 Impact Factor
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ABSTRACT: A mixed absorbent had been proposed to enhance the chemical absorption-biological reduction process for NO(x) removal from flue gas. The mole ratio of the absorbent of Fe(II)Cit to Fe(II)EDTA was selected to be 3. After the biofilm was formed adequately, some influential factors, such as the concentration of NO, O(2), SO(2) and EBRT were investigated. During the long-term running, the system could keep on a steady NO removal efficiency (up to 90%) and had a flexibility in the sudden changes of operating conditions when the simulated flue gas contained 100-500 ppm NO, 100-800 ppm SO(2), 1-5% (v/v) O(2), and 15% (v/v) CO(2). However, high NO concentration (>800 ppm) and relative short EBRT (<100s) had significant negative effect on NO removal. The results indicate that the new system by using mixed-absorbent can reduce operating costs in comparison with the single Fe(II)EDTA system and possesses great potential for scale-up to industrial applications.
Bioresource technology 06/2011; 102(17):7707-12. · 4.25 Impact Factor
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ABSTRACT: A chemical absorption-biological reduction integrated process has been proposed for the removal of nitrogen oxides (NO(x)) from flue gases. In this study, we report a new approach using biofilm electrode reactor (BER) to regenerate Fe(II)EDTA via simultaneously reducing Fe(II)EDTA-NO and Fe(III)EDTA in NO(x) scrubber solution. Biofilm formed on the surface of the cathode was confirmed by Environmental Scan Electro-Microscope. Experimental results demonstrated that it was effective and feasible to utilize the BER to promote the reduction of Fe(II)EDTA-NO and Fe(III)EDTA simultaneously. The reduction efficiency of Fe(II)EDTA-NO and Fe(III)EDTA was up to 85% and 78%, respectively when the BER was continuously operated with electricity current at 30 mA. The absence of electricity induced an immediate decrease in reduction efficiency, indicating that the bio-regeneration of ferrous chelate complex was electrochemically accelerated. The present approach is considered advantageous for the enhanced bio-reduction in the NO(x) scrubber solution.
Bioresource technology 10/2010; 102(3):2605-9. · 4.25 Impact Factor
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ABSTRACT: Biological reduction of Fe(III) to Fe(II) is a key step in nitrogen oxide (NO(x)) removal by the integrated chemical absorption-biological reduction process. NO(x) removal efficiency strongly depends on the concentration of Fe(II) in the scrubbing liquid. In this study, a newly isolated strain, Enterococcus sp. FR-3, was used to reduce Fe(III) chelated with citrate to Fe(II). Strain FR-3 reduced citrate-chelated Fe(III) with an efficiency of up to 86.9% and an average reduction rate of 0.21 mM h(-1). SO(4)(2-) was not inhibitory whereas NO(2)(-) and SO(3)(2-) inhibited cell growth and thus affected Fe(III) reduction. Models based on the Logistic equation were used to describe the relationship between growth and Fe(III) reduction. These findings provide some useful data for Fe(III) reduction, scrubber solution regeneration and NO(x) removal process design.
Bioresource technology 10/2010; 102(3):3049-54. · 4.25 Impact Factor
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ABSTRACT: A new process for the removal of NO(x) by a combined Fe(II)EDTA absorption and microbial reduction has been demonstrated, in which part of the Fe(II)EDTA will be oxidized by oxygen in the flue gas to form Fe(III)EDTA. In former studies, strain FR-2 has been found to reduce Fe(III)EDTA efficiently. Otherwise, it has been reported that bio-electro reactor could efficiently provide a chance for simultaneous denitrification and metal ion removal. Therefore, a use of bio-electro reactor is suggested to promote the reduction of Fe(III)EDTA by strain FR-2 in this paper. The results showed that the concentration of Fe(III)EDTA decreased rapidly when electric current was applied, and that as the current density rose, the Fe(III)EDTA reduction rate increased while followed by a decrease afterward. The formation of the biofilm on the electrode was observed by ESEM (Environmental Scan Electro-Microscope). In addition, the Fe(III)EDTA reduction rate obviously decreased with the existence of NaNO(2).
Bioresource technology 07/2009; 100(12):2940-4. · 4.25 Impact Factor
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ABSTRACT: The biological reduction of Fe(III) ethylenediaminetetraacetic acid (EDTA) is a key step for NO removal in a chemical absorption-biological reduction integrated process. Since typical flue gas contain oxygen, NO(2)(-) and NO(3)(-) would be present in the absorption solution after NO absorption. In this paper, the interaction of NO(2)(-), NO(3)(-), and Fe(III)EDTA reduction was investigated. The experimental results indicate that the Fe(III)EDTA reduction rate decrease with the increase of NO(2)(-) or NO(3)(-) addition. In the presence of 10 mM NO(2)(-) or NO(3)(-), the average reduction rate of Fe(III)EDTA during the first 6-h reaction was 0.076 and 0.17 mM h(-1), respectively, compared with 1.07 mM h(-1) in the absence of NO(2)(-) and NO(3)(-). Fe(III)EDTA and either NO(2)(-) or NO(3)(-) reduction occurred simultaneously. Interestingly, the reduction rate of NO(2)(-) or NO(3)(-) was enhanced in presence of Fe(III)EDTA. The inhibition patterns observed during the effect of NO(2)(-) and NO(3)(-) on the Fe(III)EDTA reduction experiments suggest that Escherichia coli can utilize NO(2)(-), NO(3)(-), and Fe(III)EDTA as terminal electron acceptors.
Applied Microbiology and Biotechnology 02/2009; 82(3):557-63. · 3.42 Impact Factor
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ABSTRACT: A metabolic pathway for the biodesulfurization of model organosulfur compounds e.g., dibenzothiophene (DBT), is proposed. This pathway, defined as extended 4S pathway, incorporates the traditional 4S pathway with the methoxylation pathway from 2-hydroxybiphenyl (HBP) to 2-methoxybiphenyl (2-MBP). The formation of 2-MBP was confirmed by the gas chromatography-mass spectrometry (GC-MS) analysis. A similar pathway was also obtained in the desulfurization of 4,6-dimethyldibenzothiophene (4,6-DMDBT), confirming the methoxylation reaction in the desulfurization process by the Mycobacterium sp. strain. Compared with 2-HBP, 2-MBP has much slighter inhibition effect on the cell growth and desulfurization activity. Thus, the methoxylation pathway from 2-HBP to 2-MBP would make less inhibitory effect on the microbe. The new pathway with 2-MBP as the end product may be an alternative for the further desulfuration of the fossil fuels.
Bioresource technology 12/2008; 100(6):2085-7. · 4.25 Impact Factor
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ABSTRACT: The effect of 2-hydroxybiphenyl (2-HBP), the end product of dibenzothiophene (DBT) desulfurization via 4S pathway, on cell growth and desulfurization activity was investigated by Microbacterium sp. The experimental results indicate that 2-HBP would inhibit the desulfurization activity. Providing 2-HBP was added in the reaction media, the DBT degradation rate decreased along with the increase of 2-HBP addition. By contrast, cell growth would be promoted in the addition of 2-HBP at a low concentration (<0.1mM). At high concentration of 2-HBP, the inhibition on the cell growth occurred. Meanwhile, the inhibitory effect of 2-HBP on DBT desulfurization activity was tested both in the oil/aqueous two-phase system and the aqueous system. A mathematical model was developed to explain the product formation kinetics with DBT as the sole sulfur source. The predicted results were close to the experimental data, it elucidated that along with the 2-HBP accumulation, the inhibitory effect of 2-HBP on DBT desulfurization and cell growth was enhanced.
Bioresource Technology 10/2008; 99(15):6928-33. · 4.98 Impact Factor
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ABSTRACT: Biological reduction of nitric oxide (NO) from Fe(II) ethylenediaminetetraacetic acid (EDTA)-NO to dinitrogen (N(2)) is a core process for the continual nitrogen oxides (NO(x)) removal in the chemical absorption-biological reduction integrated approach. To explore the biological reduction of Fe(II)EDTA-NO, the stoichiometry and mechanism of Fe(II)EDTA-NO reduction with glucose or Fe(II)EDTA as electron donor were investigated. The experimental results indicate that the main product of complexed NO reduction is N(2), as there was no accumulation of nitrous oxide, ammonia, nitrite, or nitrate after the complete depletion of Fe(II)EDTA-NO. A transient accumulation of nitrous oxide (N(2)O) suggests reduction of complexed NO proceeds with N(2)O as an intermediate. Some quantitative data on the stoichiometry of the reaction are experimental support that reduction of complexed NO to N(2) actually works. In addition, glucose is the preferred and primary electron donor for complexed NO reduction. Fe(II)EDTA served as electron donor for the reduction of Fe(II)EDTA-NO even in the glucose excessive condition. A maximum reduction capacity as measured by NO (0.818 mM h(-1)) is obtained at 4 mM of Fe(II)EDTA-NO using 5.6 mM of glucose as primary electron donor. These findings impact on the understanding of the mechanism of bacterial anaerobic Fe(II)EDTA-NO reduction and have implication for improving treatment methods of this integrated approach.
Applied Microbiology and Biotechnology 07/2008; 79(4):537-44. · 3.42 Impact Factor
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ABSTRACT: In this study, adsorption of ammonia on activated carbon from aqueous solutions has been studied in a batch stirred cell. Experiments have been carried out to investigate the effects of temperature, ammonia concentration, and activated carbon dose on ammonia adsorption. The experimental results manifest that the ammonia adsorption rate on activated carbon increases with its concentration in the aqueous solutions. Ammonia adsorption also increases with temperature. The ammonia removal from the solution increases as activated carbon mass increases. The Langmuir and Freundlich equilibrium isotherm models are found to provide a good fitting of the adsorption data, with r2 = 0.9749 and 0.9846, respectively. The adsorption capacity of ammonia obtained from the Langmuir equilibrium isotherm model is found to be 17.19 mg g−1. The kinetic study shows that ammonia adsorption on the activated carbon is in good compliance with the pseudo-second-order kinetic model. The thermodynamic parameters (▵G°, ▵H°, ▵S°) obtained indicate the endothermic nature of ammonia adsorption on activated carbon. © 2008 American Institute of Chemical Engineers Environ Prog, 2008
Environmental Progress 06/2008; 27(2):225 - 233. · 0.92 Impact Factor
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ABSTRACT: A new isolated dibenzothiophene (DBT) desulfurizing bacterium, identified as Mycobacterium sp. ZD-19 can utilize a wide range of organic sulfur compounds as a sole sulfur source. Thiophene (TH) or benzothiophene (BTH) was completely degraded by strain ZD-19 within 10h or 42 h, and 100% DBT or 4,6-dimethyldibenzothiophene (4,6-DMDBT) was removed within 50h or 56 h, respectively. Diphenylsulfide (DPS) possessed the lowest desulfurization efficiencies with 60% being transformed within 50h and 80% at 90 h. The desulfurization activities of five substrates by resting cells are in order of TH>BTH>DPS>DBT>4,6-DMDBT. In addition, when DBT and 4,6-DMDBT were mixed, they could be simultaneously desulfurized by strain ZD-19. However, DBT appeared to be attacked prior to 4,6-DMDBT. The desulfurization rate of DBT or 4,6-DMDBT in mixture is lower than they are desulfurized separately, indicating that the substrate competitive inhibition is existent when DBT and 4,6-DMDBT are mixed.
Bioresource Technology 06/2008; 99(9):3630-4. · 4.98 Impact Factor
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ABSTRACT: A chemical absorption-biological reduction integrated approach, which combines the advantages of both the chemical and biological technologies, is employed to achieve the removal of nitrogen monoxide (NO) from the simulated flue gas. The biological reduction of NO to nitrogen gas (N2) and regeneration of the absorbent Fe(II)EDTA (EDTA:ethylenediaminetetraacetate) take place under thermophilic conditions (50 +/- 0.5 degrees C). The performance of a laboratory-scale biofilter was investigated for treating NO(x) gas in this study. Shock loading studies were performed to ascertain the response of the biofilter to fluctuations of inlet loading rates (0.48 approximately 28.68 g NO m(-3) h(-1)). A maximum elimination capacity (18.78 g NO m(-3) h(-1)) was achieved at a loading rate of 28.68 g NO m(-3) h(-1) and maintained 5 h operation at the steady state. Additionally, the effect of certain gaseous compounds (e.g., O2 and SO2) on the NO removal was also investigated. A mathematical model was developed to describe the system performance. The model has been able to predict experimental results for different inlet NO concentrations. In summary, both theoretical prediction and experimental investigation confirm that biofilter can achieve high removal rate for NO in high inlet concentrations under both steady and transient states.
Environmental Science and Technology 06/2008; 42(10):3814-20. · 5.23 Impact Factor
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ABSTRACT: Biological reduction of nitric oxide (NO) chelated by ferrous ethylenediaminetetraacetate (Fe(II)EDTA) to N2 is one of the core processes in a chemical absorption-biological reduction integrated technique for nitrogen oxide (NOx) removal from flue gases. A new isolate, identified as Pseudomonas sp. DN-2 by 16S rRNA sequence analysis, was able to reduce Fe(II)EDTA-NO. The specific reduction capacity as measured by NO was up to 4.17 mmol g DCW(-1) h(-1). Strain DN-2 can simultaneously use glucose and Fe(II)EDTA as electron donors for Fe(II)EDTA-NO reduction. Fe(III)EDTA, the oxidation of Fe(II)EDTA by oxygen, can also serve as electron acceptor by strain DN-2. The interdependency between various chemical species, e.g., Fe(II)EDTA-NO, Fe(II)EDTA, or Fe (III)EDTA, was investigated. Though each complex, e.g., Fe(II)EDTA-NO or Fe(III)EDTA, can be reduced by its own dedicated bacterial strain, strain DN-2 capable of reducing Fe(III)EDTA can enhance the regeneration of Fe(II)EDTA, hence can enlarge NO elimination capacity. Additionally, the inhibition of Fe(II)EDTA-NO on the Fe(III)EDTA reduction has been explored previously. Strain DN-2 is probably one of the major contributors for the continual removal of NOx due to the high Fe(II)EDTA-NO reduction rate and the ability of Fe(III)EDTA reduction.
Applied Microbiology and Biotechnology 11/2007; 76(5):1181-7. · 3.42 Impact Factor
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ABSTRACT: The naphthalimide derivative NA1 was synthesized, which consists of a bis(2-(ethylthio)ethyl)amine group binding cations and naphthalimide unit as chromogenic and fluorogenic signaling subunit. Absorption and emission spectra and the effect of polarity of solvents and pH values were studied. The photo-induced electron transfer (PET) occurred from the donor of bis(2-(ethylthio)ethyl)amine group to the naphthalimide fluorophore. The present study demonstrates that NA1 is a viable candidate as a fluorescent receptor for a new Ag+ ion sensor. This silver ion chemosensor can discriminate Ag+ ion well among heavy metal ions by an enhancement of the fluorescence intensity in ethanol-water (1:9, V:V). And NA1 is also a pH-sensor because the fluorescence of the compound varies with the pH values.
Chinese Journal of Chemistry 06/2007; 25(6):778 - 783. · 0.75 Impact Factor
