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ABSTRACT: Extended X-ray absorption fine structure (EXAFS) spectroscopy combined with statistical F-tests is used to investigate the local atomic structures of Ni(II) adsorbed on Na-rectorite. The EXAFS analysis results of Ni(II) sorption samples indicate that the first coordination shell consists of ∼6 O at the Ni-O interatomic distance (R) of ∼2.04Å. The presence of Ni backscattering at RNi-Ni=∼3.06Å in the second coordination shell suggests the formation of Ni(II) precipitate. The results of F-tests show that the Ni(II) precipitate is Ni-Al layered double hydroxide (LDH). Our results demonstrate that Ni(II) ions are retained via different mechanisms depending on solution conditions. At low pH, Ni retention is controlled mainly by the outer-sphere surface complexation. With increasing pH, outer-sphere and inner-sphere surface complexation dominate Ni uptake. Furthermore, Ni surface loading increases with temperature increasing at pH 6.5 due to the formation of inner-sphere surface complexes and Ni-Al LDH. The formation of Ni-Al LDH becomes the dominate mechanism at the elevated pH and temperature. In the presence of humic substances, the sorption of Ni(II) on Na-rectorite is dominated by the formation of ternary surface complexes. These results are important to understand the physicochemical behavior of Ni(II) in the natural environment.
Journal of hazardous materials 02/2013; 252-253C:2-10. · 4.14 Impact Factor
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ABSTRACT: This paper presents a comparative study of Cu(ii) decontamination by three different carbonaceous materials, i.e., graphene oxide, multiwalled carbon nanotubes, and activated carbon. The three carbonaceous materials were characterized by scanning electron microscopy, Fourier transform infrared spectroscopy, N(2)-BET surface area analysis, and potentiometric acid-base titrations in detail. Also, Cu(ii) adsorption on the three types of carbonaceous materials as a function of pH and Cu(ii) ion concentration were investigated. The constant capacitance model was used to determine the appropriate surface reactions of Cu(ii) adsorption on carbonaceous materials with the aid of FITEQL 4.0 software. In addition, how the surface area and the total concentration of acidic functional groups influencing the adsorption capacities of the three carbonaceous materials for Cu(ii) removal were elucidated. The results have an important role in predicting the adsorption capacity of surface modified carbonaceous materials.
Dalton Transactions 02/2013; · 3.84 Impact Factor
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ABSTRACT: In this study, humic acid-coated Fe3O4 magnetic nanoparticles (Fe3O4@HA MNPs) were synthesized by using chemical co-precipitation method and characterized in detail. The XRD analysis results showed that HA coating did not change the phase of Fe3O4 cores. The TEM image suggested that Fe3O4@HA MNPs had nearly uniform size without the observation of aggregation. The Fe3O4@HA MNPs were stable in solution and could be easily separated from aqueous solution by using magnetic separation method. Batch technique was adopted to investigate the removal efficiency of Fe3O4@HA MNPs towards Eu(III) under various environmental conditions. The kinetic process of Eu(III) sorption on Fe3O4@HA MNPs reached equilibrium in less than 30 min. The fast sorption kinetics and high sorption amount were attributed to the plentiful surface sites provided by the surface-coated HA macromolecules. The Fe3O4@HA MNPs was able to remove ~99% of Eu(III) in aqueous solution at pH 8.5. Except for SO42-, the coexisted electrolyte ions had no significant competition effects on the removal of Eu(III) by Fe3O4@HA MNPs. The obvious sorption-desorption hysteresis suggested that the removal of Eu(III) was dominated by inner-sphere surface complexation. The sorption isotherm agreed well to Langmuir model with a maximum sorption capacity of 6.95×10-5 mol/g. The leaching test showed that the Eu(III)-loaded Fe3O4@HA colloids were capable to maintain high thermodynamic stability for long aging time. The findings herein suggested that Fe3O4@HA MNPs could be potentially used as high-effective material for the enrichment and preconcentration of radionuclide Eu(III) or other trivalent lanthanides/actinides in geological repository or in nuclear waste management.
ACS Applied Materials & Interfaces 11/2012; · 4.53 Impact Factor
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ABSTRACT: The mutual effects of Cu(II) and phosphate on their interaction with γ-Al(2)O(3) are investigated by using batch experiments combined with density functional theory (DFT) calculations. The results of batch experiments show that coexisting phosphate promotes the retention of Cu(II) on γ-Al(2)O(3), whereas phosphate retention is not affected by coexisting Cu(II) at low initial phosphate concentrations (≤3.6mg P/L). Cu-phosphate aqueous complexes control Cu(II) retention through the formation of type B ternary surface complexes (where phosphate bridges γ-Al(2)O(3) and Cu(II)) at pH 5.5. This deduction is further supported by the results of DFT calculations. More specifically, the DFT calculation results indicate that the type B ternary surface complexes prefer to form outer-sphere or monodentate inner-sphere binding mode under our experimental conditions. The enhancement of phosphate retention on γ-Al(2)O(3) in the presence of Cu(II) at high initial phosphate concentrations (>3.6mg P/L) may be attributed to the formation of 1:2 Cu(II)-phosphate species and/or surface precipitates. Understanding the mutual effects of phosphate and Cu(II) on their mobility and transport in mineral/water environments is more realistic to design effective remediation strategies for reducing their negative impacts on aquatic/terrestrial environments.
Journal of hazardous materials 08/2012; 237-238:199-208. · 4.14 Impact Factor
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ABSTRACT: The influence of humic acid (HA) on Ni(II) sorption to Ca-montmorillonite was examined by using a combination of batch sorption experiments and extended X-ray absorption fine structure (EXAFS) spectroscopy technique. The sorption of Ni(II) on HA-montmorillonite hybrids is strongly dependent on pH and temperature. At low pH, the sorption of Ni(II) is mainly dominated by Ni-HA-montmorillonite and outer-sphere surface complexation. The EXAFS results indicate that the first coordination shell of Ni(II) consists of ∼6 O atoms at the interatomic distances of ∼2.04 Å in an octahedral structure. At high pH, binary Ni-montmorillonite surface complexation is the dominant sorption mechanism. EXAFS analysis indicates the formation of mononuclear complexes located at the edges of Ca-montmorillonite platelets at pH 7.5, while a Ni-Al layered double hydroxide (LDH) phase at the Ca-montmorillonite surface formed with pH 8.5. At pH 10.0, the dissolved HA-Ni(II) complexation inhibits the precipitation of Ni hydroxide, and Ni-Al LDH phase forms. The rise of temperature increases the sorption capacity of Ni(II), and promotes Ni-Al LDH phase formation and the growth of crystallites. The results are important to evaluate the physicochemical behavior of Ni(II) in the natural environment.
Dalton Transactions 08/2012; 41(35):10803-10. · 3.84 Impact Factor
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ABSTRACT: The sorption of U(VI) from aqueous solution on MX-80 bentonite was studied as a function of contact time, pH, ionic strength,
solid contents, humic acid (HA), fulvic acid (FA) and temperature under ambient conditions using batch technique. The results
indicate that sorption of U(VI) on MX-80 bentonite is strongly dependent on pH and ionic strength. The removal of U(VI) to
MX-80 bentonite is rather quick and the kinetic sorption data is simulated well by a pseudo-second-order rate equation. The
presence of HA enhances the sorption of U(VI) on MX-80 bentonite obviously, but the influence of FA on U(VI) sorption is not
obvious. The thermodynamic parameters (ΔH
0, ΔS
0, and ΔG
0) for the sorption of U(VI) calculated from temperature dependent sorption suggest that the sorption reaction is endothermic
and spontaneous.
Journal of Radioanalytical and Nuclear Chemistry 04/2012; 283(1):253-259. · 1.52 Impact Factor
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Chemical Engineering Journal. 01/2012; 210:475-481.
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ABSTRACT: Graphene has attracted multidisciplinary study because of its unique physicochemical properties. Herein, few-layered graphene oxide nanosheets were synthesized from graphite using the modified Hummers method, and were used as sorbents for the removal of Cd(II) and Co(II) ions from large volumes of aqueous solutions. The effects of pH, ionic strength, and humic acid on Cd(II) and Co(II) sorption were investigated. The results indicated that Cd(II) and Co(II) sorption on graphene oxide nanosheets was strongly dependent on pH and weakly dependent on ionic strength. The abundant oxygen-containing functional groups on the surfaces of graphene oxide nanosheets played an important role on Cd(II) and Co(II) sorption. The presence of humic acid reduced Cd(II) and Co(II) sorption on graphene oxide nanosheets at pH < 8. The maximum sorption capacities (C(smax)) of Cd(II) and Co(II) on graphene oxide nanosheets at pH 6.0 ± 0.1 and T = 303 K were about 106.3 and 68.2 mg/g, respectively, higher than any currently reported. The thermodynamic parameters calculated from temperature-dependent sorption isotherms suggested that Cd(II) and Co(II) sorptions on graphene oxide nanosheets were endothermic and spontaneous processes. The graphene oxide nanosheets may be suitable materials in heavy metal ion pollution cleanup if they are synthesized in large scale and at low price in near future.
Environmental Science & Technology 11/2011; 45(24):10454-62. · 4.80 Impact Factor
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ABSTRACT: Few-layered graphene oxide (FGO) was synthesized from graphite by using the modified Hummers method, and was characterized by scanning electron microscopy, atomic force microscopy, powder X-ray diffraction, X-ray photoelectron spectroscopy and Raman spectroscopy. The prepared FGO was used to adsorb Pb(II) ions from aqueous solutions. The abundant oxygen-containing groups on the surfaces of FGO played an important role in Pb(II) ion adsorption on FGO. The adsorption of Pb(II) ions on FGO was dependent on pH values and independent of ionic strength. The adsorption of Pb(II) ions on FGO was mainly dominated by strong surface complexation. From the adsorption isotherms, the maximum adsorption capacities (C(smax)) of Pb(II) ions on FGO calculated from the Langmuir model were about 842, 1150, and 1850 mg g(-1) at 293, 313, and 333 K, respectively, higher than any currently reported. The FGO had the highest adsorption capacities of today's nanomaterials. The thermodynamic parameters calculated from the temperature dependent adsorption isotherms indicated that the adsorption of Pb(II) ions on FGO was a spontaneous and endothermic process.
Dalton Transactions 09/2011; 40(41):10945-52. · 3.84 Impact Factor
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Plasma Processes and Polymers 04/2011; 8(7):589 - 598. · 2.47 Impact Factor
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ABSTRACT: Aniline molecules were grafted onto multiwalled carbon nanotubes (MWCNTs) by using a plasma-induced grafting technique. The polyaniline (PANI) grafted MWCNTs (PANI/MWCNTs) were characterized by using ultraviolet−visible spectrophotometry, X-ray photoelectron spectroscopy, Raman spectroscopy, thermogravimetric analysis−differential thermal analysis, and field-emission scanning electron microscopy. The results indicated that the magnetic composite consisting of PANI/MWCNTs was synthesized. The application of PANI/MWCNTs for the removal of aniline and phenol from aqueous solutions was investigated under ambient conditions. The grafted PANI on MWCNTs contributed to the enhancement of the adsorption capacity because of the strong conjugate effect between PANI and organic pollutants. PANI/MWCNTs can be separated and recovered from aqueous solution by magnetic separation. The results show that PANI/MWCNTs are a promising magnetic material for the preconcentration and separation of organic pollutants from large volumes of aqueous solutions in environmental pollution cleanup.
11/2010;
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ABSTRACT: The adsorption of 1-naphthylamine on multiwall carbon nanotubes/iron oxides/β-cyclodextrin composite (denoted by MWCNTs/iron oxides/CD) prepared by using plasma-induced grafting technique was investigated by batch technique under ambient conditions. The effect of contact time, pH, adsorbent content, temperature and initial 1-naphthylamine concentration, on 1-naphthylamine adsorption to MWCNTs/iron oxides/CD was examined. The adsorption of 1-naphthylamine on MWCNTs/iron oxides/CD was dependent on pH, adsorbent content, and temperature. The 1-napthylamien was adsorbed rapidly at the first 50h, and thereafter attained the adsorption saturation at 80h. The adsorption kinetic data were well described by the pseuso-second-order rate model. The adsorption isotherms were fitted by the Langmuir model better than by the Freundlich model. The maximum adsorption capacity of 1-naphthylamine was 200.0mg/g. The adsorption thermodynamic parameters of standard enthalpy (ΔH(0)), standard entropy changes (ΔS(0)), and standard free energy (ΔG(0)) were calculated from temperature dependent adsorption isotherms. The values of ΔH(0) and ΔG(0) suggested that the adsorption of 1-naphthylamine on MWCNTs/iron oxides/CD was endothermic and spontaneous. The electron-donor-acceptor interaction, Hydrophobic interaction, and Lewis acid-base interaction may play an important role in 1-naphthylamine adsorption. The results show that MWCNTs/iron oxides/CD is a promising magnetic nanomaterial for the preconcentration and separation of organic pollutants from aqueous solutions in environmental pollution cleanup.
Journal of hazardous materials 09/2010; 185(1):463-71. · 4.14 Impact Factor
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ABSTRACT: In this work, bentonite embedded in the polyacrylamide (PAAm) gels was used as a novel adsorbent for the removal of Cu(II) from aqueous solution. The sorption and desorption of Cu(II) on bentonite-polyacrylamide (BENT-PAAm) was investigated as the function of pH, ionic strength, adsorbent content, Cu(II) concentrations and temperature. The results indicated that the sorption of Cu(II) on BENT-PAAm was strongly dependent on pH, ionic strength and temperature. The sorption increased from about 9% to 97% at pH ranging from 2.4 to 7. The sorption of Cu(II) on BENT-PAAm increased with increasing temperature and decreasing ionic strength. The sorption of Cu(II) on BENT and on BENT-PAAm was an endothermic and irreversible process. The results of desorption indicated that the adsorbed Cu(II) ions on solid particles were difficult to be desorbed from solid to liquid phase. From the comparison with BENT, BENT-PAAm showed higher sorption capacity with C(smax) increasing from 29 to 33 mg/g at pH 6.2 and from 11 to 20mg/g at pH 5.0 for the sorption of Cu(II) from BENT to BENT-PAAm composites. The average standard enthalpy change (Delta H degrees) and the entropy change (DeltaS degrees ) of Cu(II) sorption on BENT-PAAm are higher than those of Cu(II) sorption on BENT. The BENT-PAAm composites can be used as a super-adsorbent for the removal of Cu(II) from aqueous solution.
Journal of hazardous materials 09/2009; 173(1-3):661-8. · 4.14 Impact Factor
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ABSTRACT: The analysis of failure and repair states which relate to the vehicle operation has becoming of increased importance in intelligent transportation system and safety. Monte Carlo method is a powerful and adaptive tool to evaluate the dependability of vehicle operation whose subsystems and/or components which follow to arbitrary failure and repair distributions. We had developed a computer software, Dependability Simulation System (DSS) to evaluate the dependability of vehicle operation in traffic system through simulation, which uses to estimate the reliability, maintainability, MTTRF and MTBCF (MMBCF) parameters. The computer aided dependability analysis of vehicle operation which conducted in this study is based on a proposed priority of subsystems and/or components and event sequencing. The simulation results clearly demonstrated the potential and feasibility to describe the succession of vehicle operation in traffic system with the software.
Intelligent Transportation Systems, 2003. Proceedings. 2003 IEEE; 11/2003
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ABSTRACT: Carbon nanotubes (CNTs) have aroused widespread attention as a new type of adsorbents due to their outstanding ability for the removal of various inorganic and organic pollutants, and radionuclides from large volumes of wastewater. This review summarizes the properties of CNTs and their properties related to the adsorption of various organic and inorganic pollutants from large volumes of aqueous solutions. Their application as adsorbents for the preconcentration and immobilization of all kinds of pollutants from gas streams and large volumes of aqueous solutions are summarized, and the further research trend on CNTs in the removal of pollutants is also given.
Chemical Engineering Journal.
