Objective To investigate reductive dechlorination of 4-chlorophenol (4-CP) by nanoscale Fe^0 under different conditions. Methods Nanoscale Fe^0 was synthesized by using reductive method. 4-CP and its intermediate pr...Objective To investigate reductive dechlorination of 4-chlorophenol (4-CP) by nanoscale Fe^0 under different conditions. Methods Nanoscale Fe^0 was synthesized by using reductive method. 4-CP and its intermediate products were analyzed by HPLC. Chlorine ion was quantified with DX-100 ion chromatograph. Nano-iron particles were observed under a FEI Quanta 200 FEG environmental scanning electron microscope (ESEM). Results The size of the particles was in the range of 10-100 nm. The nano-iron particles could reduce 4-CP effectively. The initial concentration of 4-CP increased with the decrease of the relative degradation rate, whereas the reduced amount of 4-CP increased. Temperature could influence both the dechlorination rate and the reaction pathway. Moreover, the stability and durability of nanoscale Fe^0 was evaluated through batch studies over extended periods of time. Conclusion The nanoscale Fe^0 can be used for sustainable treatment of contaminants in groundwater.展开更多
The principal forces driving the efficient enrichment and encapsulation of arsenic(As) into nanoscale zero-valent iron(nZVI) are the disordered arrangement of the atoms and the gradient chemical potentials within the ...The principal forces driving the efficient enrichment and encapsulation of arsenic(As) into nanoscale zero-valent iron(nZVI) are the disordered arrangement of the atoms and the gradient chemical potentials within the core-shell interface. The chemical compositions and the fine structure of nZVI are characterized with a combination of spherical aberration corrected scanning transmission electron microscopy(Cs-STEM), X-ray energy-dispersive spectroscopy(XEDS), electron energy loss spectroscopy(EELS), and high-resolution X-ray photoelectron spectroscopy(HR-XPS). Atomically resolved EELS at the oxygen K-edge unfolds that the Fe species in nZVI are well stratified from Fe(Ⅲ) oxides in the outermost periphery to a mixed Fe(Ⅲ)/Fe(Ⅱ) interlayer, then Fe(Ⅱ) oxide and the pure Fe(0) phase. Reactions between As(Ⅴ)and nZVI suggest that a well-structured local redox gradient exists within the shell layer, which serves as a thermodynamically favorable conduit for electron transfer from the iron core to the surface-bound As(Ⅴ). HR-XPS with ion sputtering shows that arsenic species shift from As(Ⅴ), As(Ⅲ)/As(Ⅴ) to As(Ⅴ)/As(Ⅲ)/As(0) from the iron oxide shell–water interface to the Fe(0) core. Results reinforce previous work on the efficacy of nZVI for removing and remediating arsenic while the analytical TEM methods are also applicable to the study of environmental interfaces and surface chemistry.展开更多
Two challenges persist in the applications of nanoscale zero-valent iron(nZVI) for environmental remediation and waste treatment: limited mobility due to rapid aggregation and short lifespan in water due to quick oxid...Two challenges persist in the applications of nanoscale zero-valent iron(nZVI) for environmental remediation and waste treatment: limited mobility due to rapid aggregation and short lifespan in water due to quick oxidation. Herein, we report the nZVI incorporated into mesoporous carbon(MC) to enhance stability in aqueous solution and mobility in porous media. Meanwhile, the reactivity of nZVI is preserved thanks to high temperature treatment and confinement of carbon framework. Small-sized(~16 nm) nZVI nanoparticles are uniformly dispersed in the whole carbon frameworks. Importantly, the nanoparticles are partially trapped across the carbon walls with a portion exposed to the mesopore channels. This unique structure not only is conductive to hold the nZVI tightly to avoid aggregation during mobility but also provides accessible active sites for reactivity. This new type of nanomaterial contains ~10 wt% of iron. The nZVI@MC possesses a high surface area(~ 500 m^2/g) and uniform mesopores(~ 4.2 nm) for efficient pollutant diffusion and reactions. Also, high porosity of nZVI@MC contributes to the stability and mobility of nZVI. Laboratory column experiments further demonstrate that nZVI@MC suspension(~4 g Fe/L) can pass through sand columns much more efficiently than bare nZVI while the high reactivity of nZVI@MC is confirmed from reactions with Ni(II). It exhibits remarkably better performance in nickel(20 mg/L) extraction than mesoporous carbon, with 88.0% and 33.0%uptake in 5 min, respectively.展开更多
Solid phase reactions of Cr(Ⅵ) with Fe(0) were investigated with spherical-aberration-corrected scanning transmission electron microscopy(Cs-STEM) integrated with X-ray energy-dispersive spectroscopy(XEDS). N...Solid phase reactions of Cr(Ⅵ) with Fe(0) were investigated with spherical-aberration-corrected scanning transmission electron microscopy(Cs-STEM) integrated with X-ray energy-dispersive spectroscopy(XEDS). Near-atomic resolution elemental mappings of Cr(Ⅵ)–Fe(0) reactions were acquired. Experimental results show that rate and extent of Cr(Ⅵ) encapsulation are strongly dependent on the initial concentration of Cr(Ⅵ) in solution. Low Cr loading in nZⅥ(〈1.0 wt%) promotes the electrochemical oxidation and continuous corrosion of n ZⅥ while high Cr loading(〉1.0 wt%) can quickly shut down the Cr uptake. With the progress of iron oxidation and dissolution, elements of Cr and O counter-diffuse into the nanoparticles and accumulate in the core region at low levels of Cr(Ⅵ)(e.g., 〈 10 mg/L). Whereas the reacted n ZⅥ is quickly coated with a newly-formed layer of 2–4 nm in the presence of concentrated Cr(Ⅵ)(e.g., 〉 100 mg/L). The passivation structure is stable over a wide range of pH unless pH is low enough to dissolve the passivation layer. X-ray photoelectron spectroscopy(XPS) depth profiling reconfirms that the composition of the newly-formed surface layer consists of Fe(Ⅲ)–Cr(Ⅲ)(oxy)hydroxides with Cr(Ⅵ) adsorbed on the outside surface. The insoluble and insulating Fe(Ⅲ)–Cr(Ⅲ)(oxy)hydroxide layer can completely cover the n ZⅥ surface above the critical Cr loading and shield the electron transfer. Thus, the fast passivation of nZⅥ in high Cr(Ⅵ) solution is detrimental to the performance of nZⅥ for Cr(Ⅵ) treatment and remediation.展开更多
Integrating nanoscale zero-valent iron(nZVI) with biological treatment processes holds the promise of inheriting significant advantages from both environmental nano-and biotechnologies. nZVI and microbes can perform i...Integrating nanoscale zero-valent iron(nZVI) with biological treatment processes holds the promise of inheriting significant advantages from both environmental nano-and biotechnologies. nZVI and microbes can perform in coalition in direct contact and act simultaneously, or be maintained in separate reactors and operated sequentially. Both modes can generate enhanced performance for wastewater treatment and environmental remediation. nZVI scavenges and eliminates toxic metals, and enhances biodegradability of some recalcitrant contaminants while bioprocesses serve to mineralize organic compounds and further remove impurities from wastewater. This has been demonstrated in a number of recent works that nZVI can substantially augment the performance of conventional biological treatment for wastewaters from textile and nonferrous metal industries. Our recent laboratory and field tests show that COD of the industrial effluents can be reduced to a record-low of 50 ppm. Recent literature on the theory and applications of the nZVI-bio system is highlighted in this mini review.展开更多
Nanoscale zero-valent iron (nZVI) possesses unique chemistry and capability for the separation and transformation of a growing number of environmental contaminants. A nZVI particle consists of two nanoscale componen...Nanoscale zero-valent iron (nZVI) possesses unique chemistry and capability for the separation and transformation of a growing number of environmental contaminants. A nZVI particle consists of two nanoscale components, an iron (oxyhydr)oxides shell and a metallic iron core. This classical "core-shell" structure offers nZVI with unique and multifaceted reactivity of sorption, complexation, reduction and precipita- tion due to its strong small particle size for engineering deployment, large surface area, abundant reactive sites and electron-donating capacity for enhanced chemical activity. For over two decades, research has been steadily expanding our understanding on the reaction mechanisms and engineering performance of nZVI for soil and groundwater remediation, and more recently for wastewater treatment.展开更多
基金The work was supported by the National Natural Science Foundation of China (Grant No. 50325824 50678089).
文摘Objective To investigate reductive dechlorination of 4-chlorophenol (4-CP) by nanoscale Fe^0 under different conditions. Methods Nanoscale Fe^0 was synthesized by using reductive method. 4-CP and its intermediate products were analyzed by HPLC. Chlorine ion was quantified with DX-100 ion chromatograph. Nano-iron particles were observed under a FEI Quanta 200 FEG environmental scanning electron microscope (ESEM). Results The size of the particles was in the range of 10-100 nm. The nano-iron particles could reduce 4-CP effectively. The initial concentration of 4-CP increased with the decrease of the relative degradation rate, whereas the reduced amount of 4-CP increased. Temperature could influence both the dechlorination rate and the reaction pathway. Moreover, the stability and durability of nanoscale Fe^0 was evaluated through batch studies over extended periods of time. Conclusion The nanoscale Fe^0 can be used for sustainable treatment of contaminants in groundwater.
基金the National Natural Science Foundation of China(11475127,51578396,41673096,and 41772243)National Postdoctoral Program for Innovative Talents(BX201700172)
文摘The principal forces driving the efficient enrichment and encapsulation of arsenic(As) into nanoscale zero-valent iron(nZVI) are the disordered arrangement of the atoms and the gradient chemical potentials within the core-shell interface. The chemical compositions and the fine structure of nZVI are characterized with a combination of spherical aberration corrected scanning transmission electron microscopy(Cs-STEM), X-ray energy-dispersive spectroscopy(XEDS), electron energy loss spectroscopy(EELS), and high-resolution X-ray photoelectron spectroscopy(HR-XPS). Atomically resolved EELS at the oxygen K-edge unfolds that the Fe species in nZVI are well stratified from Fe(Ⅲ) oxides in the outermost periphery to a mixed Fe(Ⅲ)/Fe(Ⅱ) interlayer, then Fe(Ⅱ) oxide and the pure Fe(0) phase. Reactions between As(Ⅴ)and nZVI suggest that a well-structured local redox gradient exists within the shell layer, which serves as a thermodynamically favorable conduit for electron transfer from the iron core to the surface-bound As(Ⅴ). HR-XPS with ion sputtering shows that arsenic species shift from As(Ⅴ), As(Ⅲ)/As(Ⅴ) to As(Ⅴ)/As(Ⅲ)/As(0) from the iron oxide shell–water interface to the Fe(0) core. Results reinforce previous work on the efficacy of nZVI for removing and remediating arsenic while the analytical TEM methods are also applicable to the study of environmental interfaces and surface chemistry.
基金supported by the National Natural Science Foundation of China(Nos.51578398,and 21707104)the National Postdoctoral Program for Innovative Talents(No.BX201700172)the Fundamental Research Funds for the Central Universities(No.0400219376)
文摘Two challenges persist in the applications of nanoscale zero-valent iron(nZVI) for environmental remediation and waste treatment: limited mobility due to rapid aggregation and short lifespan in water due to quick oxidation. Herein, we report the nZVI incorporated into mesoporous carbon(MC) to enhance stability in aqueous solution and mobility in porous media. Meanwhile, the reactivity of nZVI is preserved thanks to high temperature treatment and confinement of carbon framework. Small-sized(~16 nm) nZVI nanoparticles are uniformly dispersed in the whole carbon frameworks. Importantly, the nanoparticles are partially trapped across the carbon walls with a portion exposed to the mesopore channels. This unique structure not only is conductive to hold the nZVI tightly to avoid aggregation during mobility but also provides accessible active sites for reactivity. This new type of nanomaterial contains ~10 wt% of iron. The nZVI@MC possesses a high surface area(~ 500 m^2/g) and uniform mesopores(~ 4.2 nm) for efficient pollutant diffusion and reactions. Also, high porosity of nZVI@MC contributes to the stability and mobility of nZVI. Laboratory column experiments further demonstrate that nZVI@MC suspension(~4 g Fe/L) can pass through sand columns much more efficiently than bare nZVI while the high reactivity of nZVI@MC is confirmed from reactions with Ni(II). It exhibits remarkably better performance in nickel(20 mg/L) extraction than mesoporous carbon, with 88.0% and 33.0%uptake in 5 min, respectively.
基金supported by the National Natural Science Foundation of China(Nos.21677107,51578398)the Fundamental Research Funds for the Central Universities(No.0400219363)
文摘Solid phase reactions of Cr(Ⅵ) with Fe(0) were investigated with spherical-aberration-corrected scanning transmission electron microscopy(Cs-STEM) integrated with X-ray energy-dispersive spectroscopy(XEDS). Near-atomic resolution elemental mappings of Cr(Ⅵ)–Fe(0) reactions were acquired. Experimental results show that rate and extent of Cr(Ⅵ) encapsulation are strongly dependent on the initial concentration of Cr(Ⅵ) in solution. Low Cr loading in nZⅥ(〈1.0 wt%) promotes the electrochemical oxidation and continuous corrosion of n ZⅥ while high Cr loading(〉1.0 wt%) can quickly shut down the Cr uptake. With the progress of iron oxidation and dissolution, elements of Cr and O counter-diffuse into the nanoparticles and accumulate in the core region at low levels of Cr(Ⅵ)(e.g., 〈 10 mg/L). Whereas the reacted n ZⅥ is quickly coated with a newly-formed layer of 2–4 nm in the presence of concentrated Cr(Ⅵ)(e.g., 〉 100 mg/L). The passivation structure is stable over a wide range of pH unless pH is low enough to dissolve the passivation layer. X-ray photoelectron spectroscopy(XPS) depth profiling reconfirms that the composition of the newly-formed surface layer consists of Fe(Ⅲ)–Cr(Ⅲ)(oxy)hydroxides with Cr(Ⅵ) adsorbed on the outside surface. The insoluble and insulating Fe(Ⅲ)–Cr(Ⅲ)(oxy)hydroxide layer can completely cover the n ZⅥ surface above the critical Cr loading and shield the electron transfer. Thus, the fast passivation of nZⅥ in high Cr(Ⅵ) solution is detrimental to the performance of nZⅥ for Cr(Ⅵ) treatment and remediation.
基金supported by the Research and Development Program of Guangdong Province (No. 2020B0202080001)by the China Postdoctoral Science Foundation (No. 2019M651583)+1 种基金by the Education Commission of Shanghai (No. 0400106005)by the National Science Foundation of China (Nos. 21277102, 21003151)。
文摘Integrating nanoscale zero-valent iron(nZVI) with biological treatment processes holds the promise of inheriting significant advantages from both environmental nano-and biotechnologies. nZVI and microbes can perform in coalition in direct contact and act simultaneously, or be maintained in separate reactors and operated sequentially. Both modes can generate enhanced performance for wastewater treatment and environmental remediation. nZVI scavenges and eliminates toxic metals, and enhances biodegradability of some recalcitrant contaminants while bioprocesses serve to mineralize organic compounds and further remove impurities from wastewater. This has been demonstrated in a number of recent works that nZVI can substantially augment the performance of conventional biological treatment for wastewaters from textile and nonferrous metal industries. Our recent laboratory and field tests show that COD of the industrial effluents can be reduced to a record-low of 50 ppm. Recent literature on the theory and applications of the nZVI-bio system is highlighted in this mini review.
基金supported by the National Natural Science Foundation of China (Nos. 51578398 and 41772243)the National Postdoctoral Program for Innovative Talents (No. BX201700172)
文摘Nanoscale zero-valent iron (nZVI) possesses unique chemistry and capability for the separation and transformation of a growing number of environmental contaminants. A nZVI particle consists of two nanoscale components, an iron (oxyhydr)oxides shell and a metallic iron core. This classical "core-shell" structure offers nZVI with unique and multifaceted reactivity of sorption, complexation, reduction and precipita- tion due to its strong small particle size for engineering deployment, large surface area, abundant reactive sites and electron-donating capacity for enhanced chemical activity. For over two decades, research has been steadily expanding our understanding on the reaction mechanisms and engineering performance of nZVI for soil and groundwater remediation, and more recently for wastewater treatment.