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At least 1,045 records · Page 58
All sourcesNASA NTRSDOE OSTI
DOE OSTI2010

Operation characteristics of cylindrical miniature grooved heat pipe using aqueous CuO nanofluids

An experimental study was performed to investigate the operation characteristics of a cylindrical miniature grooved heat pipe using aqueous CuO nanofluid as the working fluid at some steady cooling conditions. The experiments were carried out under both the steady operation process and the unsteady startup process. The experiment results show that substituting the nanofluid for water as the working fluid can apparently improve the thermal performance of the heat pipe for steady operation. The total heat resistance and the maximum heat removal capacity of the heat pipe using nanofluids can maximally reduce by 50% and increase by 40% compared with that of the heat pipe using water, respectively. For unsteady startup process, substituting the nanofluid for water as the working fluid, cannot only improve the thermal performance, but also reduce significantly the startup time. (author)

42 ENGINEERING↗
DOE OSTI2010

Molecular Simulation of the Diffusion of Uranyl Carbonate Species in Aqueous Solution

Molecular dynamics simulations of aqueous uranyl carbonate species were carried out with two different potential models to gain molecular-level insight into the hydration properties of these species and evaluate the ability of the two models to reproduce published ab initio and experimental data. The simulation results were used to estimate the self-diffusion coefficients of uranyl carbonate species that often dominate uranyl speciation in groundwater systems. The first potential model was based on a series of shell models developed by Parker and co-workers (including (DE LEEUW and PARKER, 1998; KERISIT and PARKER, 2004; PAVESE et al., 1996). The second potential model was a rigid-ion model based on the flexible SPC water model (TELEMAN et al., 1987), the uranyl model of Guilbaud and Wipff (GUILBAUD and WIPFF, 1996), and the parameters for the carbonate ion given by Greathouse and co-workers (GREATHOUSE and CYGAN, 2005; GREATHOUSE et al., 2002). Analysis of structural (mean interatomic distances and coordination numbers) and dynamical (water residence times in hydration shell and self-diffusion coefficients) properties showed that, overall, the first potential model performed best when compared to published data, although the only major discrepancy with the second model was a misrepresentation of the configuration adopted by the alkaline-earth uranyl carbonate ions. The diffusion coefficients obtained for the alkaline-earth cations and the uranyl ion were compared with three variants of the Stokes-Einstein (SE) equation and it was found that none of the three SE models were able to reproduce both the absolute values and the overall trend determined from the molecular dynamics simulations. However, as would be expected based on the SE equation, a plot of the diffusion coefficients of the uranyl carbonate complexes as a function of the inverse of the equivalent spherical radius showed a general linear dependence with the two models yielding almost identical gradients. The nature of the alkaline-earth cation in the uranyl carbonate complexes was found to have only a small effect on the ion’s diffusion coefficient.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2016

Study of the photocatalytic activity of Fe 3+ , Cr 3+ , La 3+ and Eu 3+ single-doped and co-doped TiO 2 catalysts produced by aqueous sol-gel processing

An aqueous sol-gel process, previously developed for producing undoped and Cu 2+ , Ni 2+ , Zn 2+ or Pb 2+ doped TiO 2 photocatalysts with remarkably high photocatalytic activity without requiring any calcination step, has been adapted to produce Fe 3+ , Cr 3+ , La 3+ or Eu 3+ single-doped TiO 2 photocatalysts as well as La3+-Fe3+ and Eu3+-Fe3+ co-doped TiO 2 catalysts. The physicochemical properties of the obtained catalysts have been characterized using a suite of complementary techniques, including ICP-AES, XRD, UV-Vis spectroscopy, nitrogen adsorption-desorption and Fe-57 M ssbauer. The active crystalline phase is obtained without requiring any calcination step and all the different catalysts are composed of nanocrystallites of anatase with a size of 6-7 nm and a high specific surface area varying from 181 to 298 m 2 g -1 . In this study, the effect of the NO 3 :Ti(IV) mole ratio used to induce the peptisation reaction during the synthesis has been studied and the results revealed that this ratio can influence significantly the textural properties of the resulting catalyst. A screening of the photocatalytic activity of the undoped and Fe 3+ , Cr 3+ , La 3+ or Eu 3+ single-doped and co-doped photocatalysts has been performed by evaluating the degradation of 4-nitrophenol under UV-Visible light (330 nm < < 800 nm). This study suggests that the photocatalytic activity is significantly influenced by the dopant nature and content with an optimal dopant content being observed in the case of Fe 3+ or La 3+ single-doped as well as in the case of La 3+ -Fe 3+ and Eu 3+ -Fe 3+ co-doped catalysts. In the case of Cr 3+ single-doped catalysts, a detrimental effect of the dopant on the photocatalytic degradation of 4-nitrophenol has been observed while no significant influence of the dopant has been detected in the case of Eu 3+ single-doped catalysts. In conclusion, the role of the different dopants in modulating the photocatalytic activity is discussed.

36 MATERIALS SCIENCE↗
DOE OSTI2012

Correlation of Pt-Re Surface Properties with Reaction Pathways for the Aqueous-Phase Reforming of Glycerol

The surface properties of Pt-Re catalytic nano-particles supported on carbon following exposure to a hydrogen reducing environment and subsequent hydrothermal conditions have been studied using in-situ X-ray photoelectron spectroscopy (XPS) and ammonia temperature programmed desorption (TPD). These properties have been correlated with the catalyst selectivity for the aqueous phase reforming of glycerol. We show that Pt in reduced Pt-Re/C becomes electron deficient, and a fraction of the Re becomes oxidized when the catalyst is subsequently exposed to hydrothermal reaction conditions. Oxidation of Pt-Re generates surface acidity, which drastically affects the reaction pathways. The acid site concentration, but not acid site strength, increases with Re loading. This acidity increase with Re addition favors C-O over C-C cleavage, which results in higher selectivity to liquid products and alkanes at the expense of hydrogen production. We propose a model for the Pt-Re active site and the origin of acidity enhanced by the addition of Re.

08 HYDROGEN↗
DOE OSTI2018

Osmotic and activity coefficients for five lithium salts in three non–aqueous solvents

To obtain osmotic coefficients, a classic static–view apparatus was used to measure the difference between the vapor pressure of a solvent and that of its salt solution at 25 °C. Vapor–pressure lowering was measured for solutions containing a lithium salt (LiCl, LiBr, LiNO 3 , LiPF 6 and LITFSI) dissolved in a non–aqueous solvent (dimethyl carbonate, dimethyl sulfoxide and acetonitrile) that may be used in a lithium–ion battery. The osmotic–coefficient data are represented by Archer's extended Pitzer equation. As a result, mean ionic activity coefficients for the salts are calculated from the osmotic–coefficient data.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2024

Boron and lithium aqueous thermochemistry to model crud deposition in pressurized water reactors

Here, a comprehensive database of boron and lithium aqueous thermochemistry has been developed for use at elevated temperatures. The Helgeson-Kirkham-Flowers (HKF) formalism provides a framework to describe thermodynamic properties over a broad range of temperatures and pressures. Accuracy at high temperatures is vital to modeling nickel oxide and ferrite fuel deposits that occur in pressurized water nuclear reactors (PWRs). CALPHAD (CALculation of PHAse Diagrams) calculations are performed at PWR crud conditions to predict the stability regions of the solid lithium metaborate (LiBO 2 ) and lithium tetraborate (Li 2 B 4 O 7 ) precipitates. In addition, similar calculations are performed using sodium and potassium instead of lithium in order to assess the thermodynamics associated with preventing the formation of such precipitates. This database contributes to understanding of crud formation and composition and will aid in the prediction of phenomena such as Crud-Induced Power Shifts (CIPS).

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2023

A high-capacity Sn metal anode for aqueous acidic batteries

Aqueous acidic batteries as a good choice to respond battery diversity, delivering safety, cost, environmental friendliness and high-power necessary for renewable energy storage. However, the practical adoption is greatly challenged by low-voltage and energy density due to the inadequate metal anode materials. Here we report an interfacial regulated Sn metal anode as the solution of the last piece of the puzzle. In this study, the ease of recycling, low potential, fast redox kinetics, and high capacity of Sn perfectly fit the battery system, and the Sn metal shedding critical issue is successfully suppressed by promoting uniform deposition for added interaction from alloying. Consequently, this reversible Sn anode with 442 mAh g -1 matches well to different types of cathodes. The as-assembled acidic batteries also demonstrate sufficient output voltage (up to 1.7 V), energy density (up to 312 Wh kg -1 based on both electrodes), kinetics (up to 24 C) and stability (up to 2400 cycles).

25 ENERGY STORAGE↗
DOE OSTI2025

A hybrid numerical and machine learning framework for evaluating the performance of a 780 cm 2 aqueous organic redox flow battery

Aqueous organic redox flow battery (AORFB) is a promising cost-competitive technology for large-scale energy storage. Among existing work, the dihydroxyphenazine (DHP)-based AORFB has demonstrated high energy density and low capacity degradation in 10 cm2 cells during lab tests. However, its commercial-scale performance in more complex environments remains unknown, posing a barrier for commercialization. To address this gap, this work presents a comprehensive performance evaluation of a 780 cm 2 DHP-based AORFB by combining physics-based numerical model, machine learning (ML)-based surrogate models, and ML-derived sensitivity quantification. Specifically, we first select 12 key battery parameters that include 10 physicochemical quantities and 2 operation quantities, then select 6 performance metrics that include energy efficiency (EE), discharging capacity, charging energy, and power losses due to concentration, activation, and ohmic over-potentials. With such selection, 12800 combinations of the 12 parameters are subsequently generated using the Latin Hypercube Sampling method. These combinations, together with 38 pre-defined State of Charge, are then integrated to a validated AORFB model developed in COMSOL to compute the performance metrics. With both input parameters and performance metrics, 60 deep neural network (DNN) surrogate models are then trained to approximate the relationship between the 10 physicochemical quantities and 6 performance metrics at each flow rate and current density. Sensitivity scores are then calculated based on the DNN models. Two additional sensitivity analysis tools, i.e., MARS, and SHAP, are also used to cross-validate the sensitivity scores from the DNN. The results demonstrate that 1) the standard potential ranks the first in controlling EE and charging energy, 2) the membrane conductivity is most critical for power loss and EE, and 3) specific area and reaction rate control activation power loss.

25 ENERGY STORAGE↗
DOE OSTI2010

Application of Brazilian kaolinite clay as adsorbent to removal of U(VI) from aqueous solution: Kinetic and thermodynamic of cation-basic interactions

The compound N{sup 1}-[3-(trimethoxysilyl)propyl]diethylenetriamine was anchored onto Amazon kaolinite surface by heterogeneous route. The modified and natural kaolinite samples were characterized by transmission electron microscopy, scanning electron microscopic, X-ray diffraction, and nuclear magnetic nuclei of {sup 29}Si and {sup 13}C. The well-defined peaks obtained in the {sup 13}C NMR spectrum in the 5.0-62.1 ppm region confirmed the attachment of organic functional groups as pendant chains bonded into the porous clay. The ability of these materials to remove U(VI) from aqueous solution was followed by a series of adsorption isotherms adjusted to a Sips equation at room temperature and pH 4.0. The kinetic parameters analyzed by the Lagergren and Elovich models gave a good fit for a pseudo-second order reaction with k{sub 2} values 16.0 and 25.1 mmol g{sup -1} min{sup -1} ranges for natural and modified kaolinite clays, respectively. The energetic effects caused by metal ion adsorption were determined through calorimetric titrations. - Graphical abstract: This investigation reports the use of original and modified kaolinites as alternative absorbents. The compound N-[3-trimethoxysilyl)propyl]diethylenetriamine was anchored onto Amazon kaolinite surface by heterogeneous route.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2013

Uniform Cu{sub 2}Cl(OH){sub 3} hierarchical microspheres: A novel adsorbent for methylene blue adsorptive removal from aqueous solution

Using the solution phase method without any surfactants or templates, the hierarchical of Cu{sub 2}Cl(OH){sub 3} microspheres were synthesized by freeze drying. The size and surface area of the microspheres are ca. 1–2 µm and 76.61 m{sup 2} g{sup −1}, respectively. A possible formation mechanism is presented based on the experimental results. Methylene blue was chosen to investigate the adsorption capacity of the as-prepared adsorbent. The effects of various experimental parameters, such as pH, initial dye concentration, and contact time were investigated. The results showed that the dye removal increased with the increasing in the initial concentration of the dye and also increased in the amount of microspheres used and initial pH. Adsorption data fitted well with the Freundlich adsorption isotherm. The thermodynamic analysis presented the exothermic, spontaneous and more ordered arrangement process. The microspheres could be employed effective for removal of dyes from aqueous solution. - Graphical abstract: The single-crystalline hierarchical Cu{sub 2}Cl(OH){sub 3} spheres can be prepared for the first time by using a template-free process through freeze-drying. Meanwhile, the hierarchical spheres exhibited high adsorption capacity to methylene blue. Display Omitted - Highlights: • Cu{sub 2}Cl(OH){sub 3} microspheres were successfully synthesized through a freeze drying process. • A possible formation mechanism of hierarchical microspheres was presented. • The Cu{sub 2}Cl(OH){sub 3} microspheres have high methylene blue adsorption capacity. • Methylene blue adsorption is a spontaneous and exothermic process. • The adsorption mechanism of microspheres onto dye was proposed in detail.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2015

Synthesis and utilization of a novel carbon nanotubes supported nanocables for the adsorption of dyes from aqueous solutions

Using multiwalled carbon nanotubes(MWCNTs) as mechanical support and glucose as carbon resource, a hydrothermal carbonization route was designed for the synthesis of MWCNTs@carbon nanocables with tunable diameter and length. MWCNTs are firstly used as templates for the formation of carbon-rich composite nanocables, and the diameter of the nanocables could be tailored through adjusting the hydrothermal time or the ratio of MWCNTs and glucose. Owing to abundant superficial oxygen-containing functional groups, porous surface and remarkable reactivity, the as-synthesized nanocables are capable of efficiently adsorbing cationic dye methylene blue (MB) and crystal violet (CV). Furthermore, the optimum adsorption conditions, kinetics, adsorption isotherms and adsorption thermodynamics of dyes were studied systematically. Additionally, the maximum adsorption capacities calculated from data analysis (298.5 mg/g for MB and 228.3 mg/g for CV) are significant higher than those of raw MWCNTs and some other adsorbents reported previously, which provides strong evidence for using MWCNTs@carbon nanocables as adsorbent to remove dyes from aqueous solutions. - Graphical abstract: MWCNTs@carbon nanocables has been successfully fabricated by a hydrothermal carbonization method. The as-synthesized novel samples were used as adsorbents and exhibited high adsorption capacity on MB and CV. - Highlights: • A simple, cost-effective and “green” method for the synthesis of the material. • The diameter and length of the material are relatively easy to control. • The surface has large oxygen-containing groups and preferable chemical reactivity. • Compared with raw MWCNTs and some other adsorbents, the adsorption capacity is much high.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2016

Conditions and mechanisms for the formation of nano-sized Delafossite (CuFeO{sub 2}) at temperatures ≤90 °C in aqueous solution

In this study, we present the mechanism of CuFeO{sub 2} formation in aqueous solution at low temperatures ≤90 °C, using sulfate salts as reactants. Furthermore, we demonstrate the influence of experimental conditions (alkalization, reaction and ageing temperature and time) on the synthesized nanoparticles. In all cases, GR–SO{sub 4}, a Fe(II–III) layered double hydroxysulphate (Fe{sup 2+}{sub 4}Fe{sup 3+}{sub 2}(OH){sub 12}·SO{sub 4}) and Cu{sub 2}O precipitate first. During further OH{sup −} supply GR–SO{sub 4} oxidizes and forms Fe{sub 10}O{sub 14}(OH){sub 2}, Cu{sub 2}O and CuFeO{sub 2} crystals. Due to the high pH further CuFeO{sub 2} crystals grow at the cost of the unstable intermediate products. The reaction rate increases with increasing ageing temperature, reaction pH and, in particular, NaOH concentrations in the solution. As a result, highly crystalline CuFeO{sub 2} (3R and 2H polytypes) nanoparticles showing hexagonal morphology can be synthesized at 70 °C within 10 h or at 50 °C within 1 week. The formation of 2H polytype is favored by additional OH{sup −} supply during the pH-stat time and rather low temperatures. - Highlights: • We solve the formation mechanism of pure CuFeO{sub 2} using sulfates as reactants. • CuFeO{sub 2} nanoparticles crystallize on cost of green rust, Fe{sub 10}O{sub 14}(OH){sub 2} and Cu{sub 2}O. • The reaction rate increases with increasing temperature and OH- concentration. • CuFeO{sub 2} nanoparticles form at 50 °C within one week and at 70 °C within 10 h. • 2H-polytype of CuFeO{sub 2} is favored by additional NaOH supply during pH-stat-time.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2013

Photocatalytic degradation of pentachlorophenol in aqueous solution by visible light sensitive N-F-codoped TiO{sub 2} photocatalyst

Graphical abstract: Schematic representation for the visible light photocatalytic process of N and F codoped TiO{sub 2}. Highlights: ► Visible light sensitive N-F-codoped TiO{sub 2}. ► Photocatalytic degradation of pentachlorophenol. ► Effect of oxidants on photocatalytic degradation of pentachlorophenol. ► PMS is a more efficient oxidant for the photodegradation of PCP. - Abstract: In this present study, N-F-codoped titanium dioxide nanocatalyst (NFTO) has been synthesized by simple sol–gel assisted solvothermal method for the effective utilization of visible light in photocatalytic reactions. Structural characterization of the photocatalyst is analyzed by XRD, UV–vis diffuse reflectance spectra (DRS), SEM and TEM. Moreover the chemical statuses of NFTO are gathered by X-ray photoelectron spectroscopy (XPS). The results show that a high surface area with photoactive anatase phase crystalline is obtained. In addition, nitrogen and fluorine atoms are doped into TiO{sub 2} crystal lattice to extend the visible light absorption and higher photocatalytic activity. The photocatalytic degradation of pentachlorophenol in aqueous solution is examined under visible light irradiation, the addition of oxidants such as PMS, PDS and H{sub 2}O{sub 2} is analyzed in detail. The rate of photocatalytic degradation of pentachlorophenol is obtained in the following order: PMS > PDS > H{sub 2}O{sub 2}.

36 MATERIALS SCIENCE↗
DOE OSTI2013

New porous titanium–niobium oxide for photocatalytic degradation of bromocresol green dye in aqueous solution

Graphical abstract: The photocatalytic activity of different porous titanium–niobium oxides was evaluated toward degradation of bromocresol green (BG) under UV light. A better catalytic activity was observed for all samples at lower pH. Catalysts have a stronger ability for degradation of BG in acid media than in alkaline media. - Highlights: • Different highly structured titanium–niobium oxides have been prepared using improved methods of synthesis. • Photo-degradation of bromocresol green dye (BG) with nanostructure titanium–niobium oxide catalysts was carried out under UV light. • The photo-catalytic activity of all catalysts was higher in lower pH. • Titanium–niobium oxide catalysts are considerably stable and reusable. - Abstract: In this study, high surface area semiconductors, non porous and porous titanium–niobium oxides derived from KTiNbO{sub 5} were synthesized, characterized and developed for their utility as photocatalysts for decontamination with sunlight. These materials were then used in the photocatalytic degradation of bromocresol green dye (BG) in aqueous solution using UV light and their catalytic activities were evaluated at various pHs. For all catalysts, the photocatalytic degradation of BG was most efficient in acidic solutions. Results show that the new porous oxides have large porous and high surface areas and high catalytic activity. A topotactic dehydration treatment greatly improves catalyst performance at various pHs. Stability and long term activity of porous materials (topo and non-topo) in photocatalysis reactions was also tested. These results suggest that the new materials can be used to efficiently purify contaminated water.

36 MATERIALS SCIENCE↗
DOE OSTI2014

Preparation and lithium intercalation behavior of TiO{sub 2} in aqueous solutions

Highlights: • The poor crystalline anatase phase or amorphous TiO{sub 2} was prepared by TiCl{sub 4} hydrolysis under different pH conditions. • Phase transition behavior and lithium intercalation ability of the obtained TiO{sub 2} were found to be related to TiO{sub 2} property. • The results indicate that TiO{sub 2} products obtained from TiCl{sub 4} hydrolysis at lower pH are favorable for lithium intercalation. - Abstract: The low crystalline or amorphous TiO{sub 2} was prepared by TiCl{sub 4} hydrolysis in aqueous solutions under different pH conditions at 45 °C. The products obtained at lower pH (1.23–3.10) appear to be nano-sized particles with poor crystalline anatase structure and an uniform particle size distribution, while the product prepared at pH 4.10 presents in a poor crystalline anatase structure and the regular morphology starts to disappear, and the products obtained at higher pH (>6.00) are amorphous and irregular morphology. The hydrolysis products obtained at pH 2.60 and 8.80 were heat-treated at 300, 400, 600, 700 and 800 °C for 3 h, respectively, to figure out the phase transition. The differences in phase transition process were observed, which verified the properties difference. The lithium intercalation abilities of the obtained TiO{sub 2} were studied. The results indicated that the TiO{sub 2} obtained at lower pH are more favorable for lithium intercalation and are better precursors.

36 MATERIALS SCIENCE↗
DOE OSTI2014

Structural, chemical and optical evaluation of Cu-doped ZnO nanoparticles synthesized by an aqueous solution method

Highlights: • Cu-doped ZnO nanoparticles obtained by chemical synthesis. • Substitutional or interstitial Cu into ZnO lead specific structural, chemical, and optical changes. • Incorporation efficiency of Cu atoms in ZnO as a function of the Cu concentration in the precursor dissolution. - Abstract: In this work a study of ZnO and Cu-doped ZnO nanoparticles obtained by chemical synthesis in aqueous media was carried out. Structural analysis gave the dominant presence of wurtzite ZnO phase forming a solid solution Zn{sub 1−x}Cu{sub x}O. For high Cu doping CuO phase is also present. For low Cu concentration the lattice shrinks due to Cu atoms substitute Zn atoms. For high Cu concentration the lattice enlarges due to predominance of interstitial Cu. From elemental analysis we determined and analyzed the incorporation efficiency of Cu atoms in Zn{sub 1−x}Cu{sub x}O as a function of the Cu concentration in the precursor dissolution. Combining structural and chemical results we described the Cu/Zn precursor concentrations r{sub w} in which the solid solution of Cu in ZnO is predominant. In the region located at r{sub w} ≈ 0.2–0.3 it is no longer valid. For Cu/Zn precursor concentration r{sub w} > 0.3 interstitial Cu dominates, and some amount of copper oxide appears. As the Cu concentration increases, the effective size of nanoparticles decreases. Photoluminescence (PL) measurements of the Cu-doped ZnO nanoparticles were carried out and analyzed.

36 MATERIALS SCIENCE↗
DOE OSTI2015

Adsorption of La(III) in aqueous systems by N-(2-hydroxyethyl) salicylaldimine-functionalized mesoporous silica

Highlights: • HESI-SBA-15 as a new adsorbent was synthesized for the first time. • This adsorbent was selective for lanthanum ion removal in presence of other ions. • The factors that affected adsorption of La(III) in aqueous solution were studied. • La{sup 3+} uptake process was according to pseudo-second-order kinetic model. - Abstract: In this work, a novel modified SBA-15 with covalently bonded N-(2-hydroxyethyl) salicylaldimine Schiff base as a ligand (HESI-SBA-15) was successfully synthesized, characterized and used as a selective absorbent for lanthanum ions removal from water systems. The structure and physicochemical properties were identified by elemental analysis, X-ray diffraction, nitrogen adsorption–desorption, thermogravimetric analysis and FTIR spectroscopy, scanning electron microscopy, BET surface area and BJH pore size. These techniques have confirmed that the Schiff base ligand was successfully grafted on the SBA-15 surface and ordered arrangement of the silica support was preserved under functionalization. The effect of pH, adsorbent dose, contact time, ionic strength and initial metal ions concentration were studied by using a batch method. This new adsorbent showed high adsorption capacity and selectivity for lanthanum in the presence of other ions. The adsorption process was exactly according to the pseudo-second-order kinetic model. The adsorbent showed a good reusability after four cycles recovery.

36 MATERIALS SCIENCE↗
DOE OSTI2015

Synthesis of kaolin supported nanoscale zero-valent iron and its degradation mechanism of Direct Fast Black G in aqueous solution

Graphical abstract: UV–visible spectra of DFBG solution using K-nZVI (1:1) nanoparticles. (a) Before reaction; (b) during reaction; (c) after reaction. - Highlights: • Kaolin-supported Fe{sup 0} nanoparticle (K-nZVI) was synthesized. • Degradation of Direct Fast Black by K-nZVI was studied. • K-nZVI was characterized by SEM, XRD, UV and FIIR. • Degradation mechanism of Direct Fast Black was proposed. - Abstract: Calcinated kaolin supported nanoscale zero-valent iron (K-nZVI) was synthesized and used for the removal of tetrad azo-group dye-Direct Fast Black G (DFBG) from aqueous solution. The results demonstrated that after reacting for 10 min with an initial concentration of DFBG 100 mg L{sup −1} (pH 9.49), 78.60% of DFBG was removed using K-nZVI, while only 41.39% and 12.56% of DFBG were removed using nZVI and kaolin, respectively. K-nZVI with a mass ratio of nZVI nanoparticles versus kaolin at 1:1 was found to have a high degree of reactivity. Furthermore, scanning electron microscopy (SEM) confirmed that nZVI was better dispersed when kaolin was present. XRD patterns indicated that iron oxides were formed after reaction. Fourier transforms infrared spectra (FTIR) and UV–visible demonstrated that the peak in the visible light region of DFBG was degraded and new bands were observed. Kinetics studies showed that the degradation of DFBG fitted well to the pseudo first-order model. The degradation of DFBG by K-nZVI was based on its adsorption onto kaolin and iron oxides, and subsequently reduction using nZVI was proposed. A significant outcome emerged in that 99.84% of DFBG in wastewater was removed using K-nZVI after reacting for 60 min.

36 MATERIALS SCIENCE↗