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  • 1
    Language: English
    In: Thin Solid Films, 01 February 2017, Vol.623, pp.14-18
    Description: The Mn-doped PbPdO nanograin film with many Pb vacancies was synthesized by using a sol-gel spin-coating method. The valence states for Pb, Pd and Mn ions were found to be 2 +, 2 + and the mixed one of 3 + and 4 +, respectively. The existence of Pb vacancies was believed to result in the increase of the Mn valence. The ferromagnetism and the antiferromagnetism were found to coexist in the formed Mn-doped PbPdO nanograin film. The ferromagnetism which can be maintained to above the room temperature was proved to be intrinsic. The carrier-mediated mechanism bridged to bound magnetic polaron model was used to explain the coexistence of the antiferromagnetism and the ferromagnetism within the Mn-doped PbPdO film.
    Keywords: Mn-Doped Pbpdo2 ; Sol-Gel Spin-Coating Method ; Magnetism ; Xanes Analysis ; Engineering ; Physics
    ISSN: 0040-6090
    E-ISSN: 1879-2731
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  • 2
    Language: English
    In: Water Research, 01 January 2016, Vol.88, pp.199-206
    Description: Microscale zero valent iron (mZVI) is a promising material for in-situ contaminated groundwater remediation. However, its usefulness has been usually inhibited by mZVI particles' low mobility in saturated porous media for sedimentation and deposition. In our study, laboratory experiments, including sedimentation studies, rheological measurements and transport tests, were conducted to investigate the feasibility of xanthan gum (XG) being used as a coating agent for mZVI particle stabilization. In addition, the effects of XG concentration, flow rate, grain diameter and water chemistry on XG-coated mZVI (XG-mZVI) particle mobility were explored by analyzing its breakthrough curves and retention profiles. It was demonstrated that XG worked efficiently to enhance the suspension stability and mobility of mZVI particles through the porous media as a shear thinning fluid, especially at a higher concentration level (3 g/L). The results of the column study showed that the mobility of XG-mZVI particles increased with an increasing flow rate and larger grain diameter. At the highest flow rate (2.30 × 10  m/s) within the coarsest porous media (0.8–1.2 mm), 86.52% of the XG-mZVI flowed through the column. At the lowest flow rate (0.97 × 10  m/s) within the finest porous media (0.3–0.6 mm), the retention was dramatically strengthened, with only 48.22% of the particles flowing through the column. The XG-mZVI particles appeared to be easily trapped at the beginning of the column especially at a low flow rate. In terms of two representative water chemistry parameters (ion strength and pH value), no significant influence on XG-mZVI particle mobility was observed. The experimental results suggested that straining was the primary mechanism of XG-mZVI retention under saturated condition. Given the above results, the specific site-related conditions should be taken into consideration for the design of a successful delivery system to achieve a compromise between maximizing the radius of influence of the injection and minimizing the injection pressure.
    Keywords: Xanthan Gum (Xg) ; Microscale Zero Valent Iron (Mzvi) ; Transport ; Porous Media ; Engineering
    ISSN: 0043-1354
    E-ISSN: 1879-2448
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  • 3
    Language: English
    In: Water Research, 01 September 2016, Vol.100, pp.80-87
    Description: Application of microscale zero-valent iron (mZVI) is a promising technology for in-situ contaminated groundwater remediation; however, its longevity is negatively impacted by surface passivation, especially in saline groundwater. In this study, the aging behavior of mZVI particles was investigated in three media (milli-Q water, fresh groundwater and saline groundwater) using batch experiments to evaluate their potential corrosion and passivation performance under different field conditions. The results indicated that mZVI was reactive for 0–7 days of exposure to water and then gradually lost H -generating capacity over the next hundred days in all of the tested media. In comparison, mZVI in saline groundwater exhibited the fastest corrosion rate during the early phase (0–7 d), followed by the sharpest kinetic constant decline in the latter phases. The SEM-EDS and XPS analyses demonstrated that in the saline groundwater, a thin and compact oxide film was immediately formed on the surface and significantly shielded the iron reactive site. Nevertheless, in fresh groundwater and milli-Q water, a passive layer composed of loosely and unevenly distributed precipitates slowly formed, with abundant reactive sites available to support continuous iron corrosion. These findings provide insight into the molecular-scale mechanism that governs mZVI passivation and provide implications for long-term mZVI application in saline contaminated groundwater.
    Keywords: Microscale Zero-Valent Iron (Mzvi) ; Aging ; Passivation ; Hydrogen Production ; Saline Groundwater ; Engineering
    ISSN: 0043-1354
    E-ISSN: 1879-2448
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  • 4
    Language: English
    In: Science of the Total Environment, 01 June 2018, Vol.626, pp.638-649
    Description: In this study, long-term column experiments were conducted in three media (Milli-Q water, fresh groundwater and saline groundwater) to evaluate the trichloroethylene (TCE) removal performance, electron efficiency (EE), and permeability loss of a microscale zero valent iron-based in situ reactive zone (mZVI-IRZ) under different field conditions. A potential scenario of in situ contamination plume remediation was simulated by adding a TCE-containing influent to columns filled with mixed mZVI particles and silica sand at a flow rate of 4 mL h for 6 months. Results showed that, over the course of 100 pore volumes (PV) for 6 months, mZVI displayed the lowest TCE breakthrough rate (0.0026 PV ) and highest TCE removal capacity (43.72 mg) but the poorest EE value (25–40%) in saline groundwater. Mineral characterization (SEM, XRD), ion concentration analysis, and geochemical modeling corroborated that different dominant solid precipitates (magnetite, siderite, dolomite/magnetite) were identified inside the three columns. The column containing saline groundwater experienced the greatest porosity loss, approximately 30.23 mL over the course of 100 PVs. This study illustrates that, to improve designs of mZVI-IRZs, EE as well as hydraulic conductivity should be taken into consideration for predictive evaluations.
    Keywords: Electron Efficiency ; Fresh Groundwater ; Microscale Zero Valent Iron (Mzvi) ; Permeability Loss ; Saline Groundwater ; Trichloroethylene (Tce) Removal ; Environmental Sciences ; Biology ; Public Health
    ISSN: 0048-9697
    E-ISSN: 1879-1026
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  • 5
    Language: English
    In: Environmental Science and Pollution Research, 2017, Vol.24(30), pp.23538-23548
    Description: A microscale zero-valent iron (mZVI)-based in situ reactive zone is a promising technology for contaminated groundwater remediation. Estimation of mZVI aging behavior after its injection into the subsurface is essential for efficiency and longevity assessments. In this study, batch tests were conducted to investigate the effect of initial pH on mZVI aging dynamics, as well as the formation and evolution of aging products over 112 days. Results indicated that mZVI aging accelerated with decreasing initial pH. Corrosion rates of mZVI particles under pH 6.0 and 7.5 were approximately two orders of magnitude higher than those observed at pH 9.0. The morphological, structural, and compositional evolution of mZVI particles in three systems (pH = 6.0, 7.5, and 9.0) were investigated using scanning electron microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy. In acidic and neutral solutions, a thick passivation layer with loosely and unevenly distributed aging precipitates was observed, and Fe 3 O 4 was the final aging precipitate. Nevertheless, in alkaline solutions, minute aging precipitates were detected on the mZVI surface at 112 day. Characterization results suggested that mZVI was oxidized via the Fe 0 –Fe(OH) 2 –Fe 3 O 4 route. These findings shed new light on mZVI aging mechanisms, particularly its physicochemical characteristics and the structural evolution of mZVI in field-scale groundwater remediation applications.
    Keywords: Microscale zero-valent iron (mZVI) ; Anaerobic corrosion ; Hydrogen production ; Corrosion rate ; Aging products
    ISSN: 0944-1344
    E-ISSN: 1614-7499
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  • 6
    Language: English
    In: Chemical Engineering Journal, 15 September 2017, Vol.324, pp.324-335
    Description: Uncertainties of aging after the injection of microscale zero valent iron (mZVI) into subsurface hinder the widespread application of this technology into in-situ groundwater remediation. As TCE removal by mZVI is usually accompanied by mZVI anaerobic reaction with water, this study investigated the hydrogen evolution kinetics, TCE removal performance, and electron efficiency (EE) of mZVI particles under single and combined effects of organic geochemical constituents (humic acid (HA)), inorganic constituents (hardness (Ca ) and alkalinity (HCO )) in groundwater. The results showed that both H generation and TCE removal were enhanced in the presence of HA (5–20 mg L as DOC), and significant delay of aging precipitates formation was supported by SEM-EDS, XRD and XPS depth-profiling characterization. With increasing Ca -HCO concentrations (0.4–2 mM), the mZVI corrosion were inhibited for the formation of a thin compact passive film on mZVI surface. Furthermore, in co-presence of organic and inorganic constituents, the negatively-impacted iron corrosion kinetics suggested that promotional effects of organic constituents were dwarfed by the inhibitory effects of inorganic constituents. In addition, the EE values in different systems ranged among 1.31–7.40%, and decreased significantly with time. Hence, these findings provide insight into aging mechanism and performance prediction of mZVI under different groundwater geochemical conditions.
    Keywords: Mzvi ; Aging ; Electron Efficiency ; Geochemical Constituent ; Tce ; Engineering
    ISSN: 1385-8947
    E-ISSN: 1873-3212
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  • 7
    Language: Chinese
    In: Zhongguo xiu fu chong jian wai ke za zhi = Zhongguo xiufu chongjian waike zazhi = Chinese journal of reparative and reconstructive surgery, 08 October 2016, Vol.30(10), pp.1270-1275
    Description: To explore the effects on osteogenic differentiation of adipose derived stem cells (ADSCs) by simultaneously down-regulating Noggin combined with up-regulating bone morphogenetic protein 14 (BMP-14) in vitro. Primary ADSCs were isolated and expanded in vitro from 5 Sprague Dawley rats (weighing, 250-300 g). ADSCs were transfected with lentiviral (Lv)-enhanced green fluorescent protein in group A (control group), with Lv-BMP-14 in group B, and with Lv-BMP-14 and Lv-Noggin shRNA in group C. BMP-14 and osteogenesis-related genes[collagen type I, alkaline phosphatase (ALP), and osteocalcin (OCN)] mRNA expression levels were detected by real time fluorescence quantitative PCR at 3, 7, and 14 days after transfection. Alizarin red staining for calcium nodules was also employed to assess the osteogenic ability of co-transfected ADSCs. At 3 days after transfection, no significant difference was found in BMP-14 mRNA expression among groups 〉0.05). At 7 and 14 days after transfection, BMP-14 mRNA expression was significantly higher in group C than groups A and B, and in group B than group A (0.05). At 7 and 14 days, collagen type I, ALP, and OCN mRNA expressions were higher in group C than groups A and B, and in group B than group A, showing significant difference (0.05). The results of alizarin red staining showed that the amount of calcium nodules presented an increased tendency in the order of group A, group B, and group C. BMP-14 is capable of enhancing osteogenic differentiation of ADSCs. A combination of inhibiting Noggin gene expression and enhancing BMP-14 gene expression in ADSCs can significantly strengthen osteogenic differentiation capability, showing significant synergistic effect.
    Keywords: Adipose Derived Stem Cells ; Bone Morphogenetic Protein 14 ; Co-Transfection ; Lentivirus ; Noggin ; Rat
    ISSN: 1002-1892
    Source: MEDLINE/PubMed (U.S. National Library of Medicine)
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  • 8
    Language: English
    In: Talanta, 15 October 2011, Vol.85(5), pp.2534-2541
    Description: ► Kinetics of complex triangular organic reaction in aqueous-ethanol media is studied. ► On-line reaction monitoring carried out using transmission FTIR spectroscopy. ► BTEM analysis provides pure spectra of reactive species and their concentrations. ► Effects of solvent and temperature on the reaction kinetics are investigated. ► Dominant synthetic pathway in the triangular system changes with ethanol:water ratio. The kinetics of the base-catalyzed reaction of methyl 4-hydroxybenzoate in aqueous-ethanol solvent medium was studied and analyzed via combined on-line transmission FTIR spectroscopy and Band-Target Entropy Minimization (BTEM) technique. This reaction is considered complex since it involves simultaneous hydrolysis and ethanolysis reactions of methyl 4-hydrozybenzoate (MP) to form ethyl 4-hydroxybenzoate (EP) as an intermediate and sodium 4-hydroxybenzoate as a final product. The pure component spectra of the reactive species involved in the reaction were reconstructed using BTEM technique. Their corresponding real concentrations were calculated and subsequently used for analyzing the kinetics of this triangular reaction system. The effects of temperature and solvent mixture compositions were studied. In general, the results show that the rates of both hydrolysis and ethanolysis reactions increase with temperature. Addition of ethanol to the solvent mixture also reduces the rates of the hydrolysis reactions. The effect of solvent mixture on the rate of ethanolysis reaction is more complex and influenced by at least two competing factors, namely the concentration of ethoxide ion in the solution and the stabilization effect on the reactant. The enthalpy and entropy activation parameters, Δ and Δ , of both the hydrolysis and ethanolysis reactions were determined using the Eyring equation and the activation parameters confirm the associative nature in the elementary steps in these reactions. Finally, it is shown that the dominant synthetic pathway in this triangular system changes from direct hydrolysis of methyl 4-hydrozybenzoate to the indirect pathway via ethanolysis and then hydrolysis depending on the solvent mixture composition.
    Keywords: On-Line Reaction Monitoring ; Multivariate Analysis ; Solvent Effect ; Spectral Deconvolution ; Chemistry
    ISSN: 0039-9140
    E-ISSN: 1873-3573
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  • 9
    Language: English
    In: Sensors, 01 March 2018, Vol.18(4), p.964
    Description: Strong fluorescent carbon nanodots (FCNs) were synthesized with a green approach using gardenia as a carbon source through a one-step hydrothermal method. FCNs were characterized by their UV-vis absorption spectra, photoluminescence (PL), Fourier transform infrared spectroscopy (FTIR) as well as X-ray photoelectron spectroscopy (XPS). We further explored the use of as-synthesized FCNs as an effective probe for the detection of metronidazole (MNZ), which is based on MNZ-induced fluorescence quenching of FCNs. The proposed method displayed a wide linear range from 0.8 to 225.0 µM with a correlation coefficient of 0.9992 and a limit of detection as low as 279 nM. It was successfully applied to the determination of MNZ in commercial tablets and rabbit plasma with excellent sensitivity and selectivity, which indicates its potential applications in clinical analysis and biologically related studies.
    Keywords: Fluorescent Carbon Nanodots ; Metronidazole ; Fluorescent Quenching ; Biological Analysis ; Engineering
    E-ISSN: 1424-8220
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  • 10
    In: Main Group Metal Chemistry, 01/1/2016, Vol.39(3-4)
    Description:   Metal contamination of soil is a serious environmental problem due to mining and use of synthetic products (e.g. pesticides, paints, batteries, and industrial wastes), which are serious threat to human life. The current research is aimed at the remediation of soil contaminated with lead (II) and chromium (VI) using indigenous fungal strains through the comparative study of bioleaching and chemical leaching methods. The removal efficiencies of Pb (II) and Cr (VI) in bioleaching were higher than chemical leaching, where 99% Cr (VI) and 36% Pb (II) were removed by Aspergillus flavus (F3) in bioleaching through the production of approximately 332 mg L -1 malic acid, 213 mg L-1 succinic acid, and 35 mg L-1 citric acid. The removal efficiencies in chemical leaching were 21.30% for Pb (II) and 1.92% for Cr (VI) by malic acid, 29.30% for Pb (II) and 72% for Cr (VI) by succinic acid, 22.21% for Pb (II) and 60.70% for Cr (VI) by citric acid, and 2.20% for Pb (II) and 2.47% for Cr (VI) by oxalic acid. The sequential extraction procedure for Pb (II) and Cr (VI) before and after bioleaching showed that Pb (II) and Cr (VI) mostly bound to stable fractions after bioleaching. Scanning electron microscopy (SEM) with energy-dispersive X-ray analysis (EDX) helped to identify the characteristic changes in the morphology and elemental composition of A. flavus (F3) biomass before and after bioleaching, whereas Fourier transform infrared spectroscopy (FTIR) showed that fungal biomass contain hydroxyl, carboxyl, fatty acids, and amine groups on its surface. The results implied that the fungal strain A. flavus (F3) can be used to remediate soils contaminated with Pb (II) and Cr (VI).
    Keywords: Aspergillus Flavus (F3) ; Bioleaching ; Contaminated Soil ; Heavy Metal;
    ISSN: 0792-1241
    E-ISSN: 2191-0219
    Source: Walter de Gruyter (via CrossRef)
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