scholarly journals Nanoscale Zero-Valent Iron Modified by Bentonite with Enhanced Cr(VI) Removal Efficiency, Improved Mobility, and Reduced Toxicity

Nanomaterials ◽  
2021 ◽  
Vol 11 (10) ◽  
pp. 2580
Author(s):  
Jien Ye ◽  
Yating Luo ◽  
Jiacong Sun ◽  
Jiyan Shi
Keyword(s):  
Removal Efficiency ◽  
Quartz Sand ◽  
Environmental Remediation ◽  
Zero Valent Iron ◽  
Transfer Factors ◽  
Environmental Media ◽  
Nanoscale Zero Valent Iron ◽  
Luminous Bacteria ◽  
Application Potential ◽  
Reduced Toxicity

The aggregation of nanoscale zero-valent iron (nZVI) particles and their limited transport ability in environmental media hinder their application in environmental remediation. In this study, the Cr(VI) removal efficiency, transport performance, and toxicity of nZVI and bentonite-modified nZVI (B-nZVI) were investigated. Compared with nZVI, B-nZVI improved the removal efficiency of Cr(VI) by 10%, and also significantly increased the transport in quartz sand and soil. Increasing the flow rate can enhance the transport of nZVI and B-nZVI in the quartz sand columns. The transport of the two materials in different soils was negatively correlated with the clay composition. Besides, modification of nZVI by bentonite could reduce toxicity to luminous bacteria (Photobacterium phosphereum T3) and ryegrass (Lolium perenne L.). Compared with Fe-EDTA, the transfer factors of nZVI and B-nZVI were 65.0% and 66.4% lower, respectively. This indicated that although iron nanoparticles accumulated in the roots of ryegrass, they were difficult to be transported to the shoots. The results of this study indicate that B-nZVI has a strong application potential in in situ environmental remediation.

scholarly journals Efficient Sequestration of Hexavalent Chromium by Graphene-Based Nanoscale Zero-Valent Iron Composite Coupled with Ultrasonic Pretreatment

2021 ◽  
Vol 18 (11) ◽  
pp. 5921
Author(s):  
Haiyan Song ◽  
Wei Liu ◽  
Fansheng Meng ◽  
Qi Yang ◽  
Niandong Guo
Keyword(s):  
Aqueous Solution ◽  
Removal Efficiency ◽  
Inhibitory Effect ◽  
Ultrasonic Cavitation ◽  
Zero Valent Iron ◽  
Ultrasonic Pretreatment ◽  
Nanoscale Zero Valent Iron ◽  
Passivation Layers ◽  
Initial Ph ◽  
Two Phases

Nanoscale zero-valent iron (nZVI) has attracted considerable attention for its potential to sequestrate and immobilize heavy metals such as Cr(VI) from an aqueous solution. However, nZVI can be easily oxidized and agglomerate, which strongly affects the removal efficiency. In this study, graphene-based nZVI (nZVI/rGO) composites coupled with ultrasonic (US) pretreatment were studied to solve the above problems and conduct the experiments of Cr(VI) removal from an aqueous solution. SEM-EDS, BET, XRD, and XPS were performed to analyze the morphology and structures of the composites. The findings showed that the removal efficiency of Cr(VI) in 30 min was increased from 45.84% on nZVI to 78.01% on nZVI/rGO and the removal process performed coupled with ultrasonic pretreatment could greatly shorten the reaction time to 15 min. Influencing factors such as the initial pH, temperature, initial Cr(VI) concentration, and co-existing anions were studied. The results showed that the initial pH was a principal factor. The presence of HPO42−, NO3−, and Cl− had a strong inhibitory effect on this process, while the presence of SO42− promoted the reactivity of nZVI/rGO. Combined with the above results, the process of Cr(VI) removal in US-nZVI/rGO system consisted of two phases: (1) The initial stage is dominated by solution reaction. Cr(VI) was reduced in the solution by Fe2+ caused by ultrasonic cavitation. (2) In the following processes, adsorption, reduction, and coprecipitation coexisted. The addition of rGO enhanced electron transportability weakened the influence of passivation layers and improved the dispersion of nZVI particles. Ultrasonic cavitation caused pores and corrosion at the passivation layers and fresh Fe0 core was exposed, which improved the reactivity of the composites.

scholarly journals Carbothermal Synthesis of Ni/Fe Bimetallic Nanoparticles Embedded into Graphitized Carbon for Efficient Removal of Chlorophenol

Nanomaterials ◽  
2021 ◽  
Vol 11 (6) ◽  
pp. 1417
Author(s):  
Min Zhuang ◽  
Wen Shi ◽  
Hui Wang ◽  
Liqiang Cui ◽  
Guixiang Quan ◽  
...  
Keyword(s):  
Removal Efficiency ◽  
Surface Passivation ◽  
Bimetallic Nanoparticles ◽  
Zero Valent Iron ◽  
Molar Ratio ◽  
Particle Sizes ◽  
Iron Corrosion ◽  
Graphitized Carbon ◽  
Nanoscale Zero Valent Iron ◽  
Iron Nickel

The reactivity of nanoscale zero-valent iron is limited by surface passivation and particle agglomeration. Here, Ni/Fe bimetallic nanoparticles embedded into graphitized carbon (NiFe@GC) were prepared from Ni/Fe bimetallic complex through a carbothermal reduction treatment. The Ni/Fe nanoparticles were uniformly distributed in the GC matrix with controllable particle sizes, and NiFe@GC exhibited a larger specific surface area than unsupported nanoscale zero-valent iron/nickel (FeNi NPs). The XRD results revealed that Ni/Fe bimetallic nanoparticles embedded into graphitized carbon were protected from oxidization. The NiFe@GC performed excellently in 2,4,6-trichlorophenol (TCP) removal from an aqueous solution. The removal efficiency of TCP for NiFe@GC-50 was more than twice that of FeNi nanoparticles, and the removal efficiency of TCP increased from 78.5% to 94.1% when the Ni/Fe molar ratio increased from 0 to 50%. The removal efficiency of TCP by NiFe@GC-50 can maintain 76.8% after 10 days of aging, much higher than that of FeNi NPs (29.6%). The higher performance of NiFe@GC should be ascribed to the significant synergistic effect of the combination of NiFe bimetallic nanoparticles and GC. In the presence of Ni, atomic H* generated by zero-valent iron corrosion can accelerate TCP removal. The GC coated on the surface of Ni/Fe bimetallic nanoparticles can protect them from oxidation and deactivation.

scholarly journals Well-Dispersed Nanoscale Zero-Valent Iron Supported in Macroporous Silica Foams: Synthesis, Characterization, and Performance in Cr(VI) Removal

2017 ◽  
Vol 2017 ◽  
pp. 1-13 ◽  
Author(s):  
Chaoxia Zhao ◽  
Jie Yang ◽  
Yihan Wang ◽  
Bo Jiang
Keyword(s):  
Removal Efficiency ◽  
Shell Structure ◽  
Zero Valent Iron ◽  
Core Shell ◽  
Ambient Atmosphere ◽  
Order Kinetic ◽  
Macroporous Silica ◽  
X Ray ◽  
Nanoscale Zero Valent Iron ◽  
Core Shell Structure

Well-dispersed nanoscale zero-valent iron (NZVI) supported inside the pores of macroporous silica foams (MOSF) composites (Mx-NZVI) has been prepared as the Cr(VI) adsorbent by simply impregnating the MOSF matrix with ferric chloride, followed by the chemical reduction with NaHB4 in aqueous solution at ambient atmosphere. Through the support of MOSF, the reactivity and stability of NZVI are greatly improved. Transmission electron microscopy (TEM) results show that NZVI particles are spatially well-dispersed with a typical core-shell structure and supported inside MOSF matrix. The N2 adsorption-desorption isotherms demonstrate that the Mx-NZVI composites can maintain the macroporous structure of MOSF and exhibit a considerable high surface area (503 m2·g−1). X-ray photoelectron spectroscopy (XPS) and powder X-ray diffraction (XRD) measurements confirm the core-shell structure of iron nanoparticles composed of a metallic Fe0 core and an Fe(II)/Fe(III) species shell. Batch experiments reveal that the removal efficiency of Cr(VI) can reach 100% when the solution contains 15.0 mg·L−1 of Cr(VI) at room temperature. In addition, the solution pH and the composites dosage can affect the removal efficiency of Cr(VI). The Langmuir isotherm is applicable to describe the removal process. The kinetic studies demonstrate that the removal of Cr(VI) is consistent with pseudo-second-order kinetic model.

Research on Foam’s Carrying Capacity of Two Types of nZVI

2017 ◽  
Vol 744 ◽  
pp. 536-541 ◽  
Author(s):  
Lan Xiang Shi ◽  
Jia Jun Chen ◽  
Meng Wei ◽  
Yun Song Liu
Keyword(s):  
Carrying Capacity ◽  
Environmental Remediation ◽  
Organic Pollutant ◽  
Zero Valent Iron ◽  
Precipitation Method ◽  
Sweep Efficiency ◽  
Experimental Conditions ◽  
Initial Concentration ◽  
Nanoscale Zero Valent Iron ◽  
The Stability

Special physical and chemical properties of nanoscale zero valent iron (nZVI), such as small particle size and high reactivity, make it a good choice as a remediation agent. nZVI is widely used in the remediation of various contaminants, including heavy metals and persistent organic pollutant. However, the immobilization of nanoparticles in porous medium limits the application in soil environmental remediation. Foam instead of water is used as the carrier of nanoparticles in in-site soil remediation process, which is a new idea, to improve sweep efficiency of nanoparticles. In this paper, the foam’s carrying ability of two types of nanoscale zero valent iron is studied. One of nZVI is purchased from a reagent Company, the other one is obtained by chemical precipitation method. In addition, the influence factors, the type and concentration of surfactant, foam quality and the initial concentration of nZVI are also discussed. The results demonstrate that foam has a 73% carrying capacity of nZVI-M, while much less capacity (33%) of nZVI-P under certain conditions. Surfactant can be used as dispersant to improve the stability of nZVI suspension. Besides, nZVI has no significant effect on the stability of foam, which provide the premise for foam as carrier. Influencing degree of these factors followed the order of the surfactant type > surfactant concentration > initial concentration of nZVI > foam quality under the experimental conditions.

scholarly journals INVESTIGATION OF REMOVAL OF HEXAVALENT CHROMIUM AND DIVALENT COBALT FROM AQUEOUS SOLUTIONS BY ORGANO-MONTMORILLONITE SUPPORTED IRON NANOPARTICLES

2016 ◽  
Vol 5 ◽  
pp. 81-88 ◽  
Author(s):  
Viktoriia Prus ◽  
Nataliya Zhdanyuk
Keyword(s):  
Environmental Remediation ◽  
Iron Nanoparticles ◽  
Removal Rate ◽  
Environmental Pollutants ◽  
Zero Valent Iron ◽  
Hexadecyltrimethylammonium Bromide ◽  
X Ray Diffraction ◽  
X Ray ◽  
Nanoscale Zero Valent Iron ◽  
Supported Iron

A new class of nanoscale zero-valent iron particles supported on natural montmorillonite and organo-montmorillonite were synthesized and the feasibility for the removal of and was examined through laboratory batch test. The X – ray diffraction (XRD) and Fourier Transform Infrared spectrum (FTIR) investigation has been applied for determination of the particle size and mechanism of remediation process. The aim of this study was to enhance the reduction of persistent environmental pollutants difficult to degrade by immobilization of nanoscale zero-valent iron on an organo-montmorillonite. Batch experiments indicated that the reduction of both and was much greater with organo-montmorillonite supported iron nanoparticles reaching removal rate up to 98.5% and 95.6% respectively at the initial metal concentrations of 50 mg/L. Iron and crystalline iron oxide were detected by X-ray diffraction patterns. In the FTIR spectrum, CH2 groups were found in iron nanoparticles supported on hexadecyltrimethylammonium bromide modified montmorillonite (HDTMA-Mont/nZVI) particles but were significantly weakened in comparison with the spectrum of hexadecyl trimethylammonium bromide (HDTMA). Other factor that affects the efficiency of heavy metals removal such as pH values was also investigated. The obtained data and review of the current literature have given the opportunity to figure out the mechanisms of and removal which may thus promote the industrial application of nZVI technique in environmental remediation by changing the hydrophilic – hydrophobic properties of source systems.

scholarly journals Adsorption of phosphorus onto nanoscale zero-valent iron/activated carbon: removal mechanisms, thermodynamics, and interferences

2022 ◽  
Author(s):  
Adel Adly ◽  
Nagwan G. Mostafa ◽  
Abdelsalam Elawwad
Keyword(s):  
Activated Carbon ◽  
Removal Efficiency ◽  
Kinetic Models ◽  
Average Particle Size ◽  
Zero Valent Iron ◽  
Solution Temperature ◽  
Average Particle ◽  
Phosphorus Adsorption ◽  
Removal Mechanisms ◽  
Nanoscale Zero Valent Iron

Abstract This study investigated removal mechanisms, thermodynamics, and interferences of phosphorus adsorption onto nanoscale zero-valent iron (nZVI)/activated carbon composite. Activated carbon was successfully used as support for nZVI particles to overcome shortcomings of using nZVI include its tendency to aggregate and separation difficulties. A comprehensive characterization was done for the composite particles, which revealed a high specific surface area of 72.66 m2/g and an average particle size of 37 nm. Several adsorption isotherms and kinetic models have been applied to understand the removal mechanisms. Adsorption isotherm is best fitted by Freundlich and Langmuir models, which indicates that the estimated maximum phosphorus adsorption capacity is 53.76 mg/g at pH 4. Adsorption kinetics showed that the chemisorption process behaved according to a pseudo-second-order model. An adsorption mechanism study conducted using the intra-particle diffusion and Boyd kinetic models indicated that the adsorption rate is limited by surface diffusion. A thermodynamic study showed that phosphorus removal efficiency increased as the solution temperature increased from 15 to 37 °C. Finally, the results of an interference study showed that the presence of Ni2+, Cu2+, Ca2+, Na+ cations, nitrate ions (), and sodium acetate improves removal efficiency, while the presence of sulfate ions () and urea reduces removal efficiency.

scholarly journals Nanoscale zero-valent iron loaded vermiform expanded graphite for the removal of Cr (VI) from aqueous solution

2021 ◽  
Vol 8 (8) ◽  
pp. 210801
Author(s):  
Xinwei Cai ◽  
Yangshuai Qiu ◽  
Yanhong Zhou ◽  
Xuan Jiao
Keyword(s):  
Aqueous Solution ◽  
Environmental Remediation ◽  
Chemical Reduction ◽  
Physical Adsorption ◽  
Exothermic Reaction ◽  
Expanded Graphite ◽  
Living Environment ◽  
Zero Valent Iron ◽  
Total Chromium ◽  
Nanoscale Zero Valent Iron

Cr (VI) is indispensable in industrial manufacturing, and its extensive use leads to severe heavy-metal pollution in the water environment around people, posing a great danger to physical health and living environment of multitudinous organisms. Expanded graphite (EG) is considered as a typical material for adsorption, while nanoscale zero-valent iron (nZVI) can be applied to degrade and sedimentate various organic or inorganic pollutants. In this study, a simultaneous collaboration of EG and nZVI is carried out, with the investigation on the influence of different test conditions for adsorption performances. These findings demonstrate that nZVI@EG manifests favourable adsorptive performance on the removal of hexavalent chromium efficiently. nZVI, acting as an electron donor, is supposed to reduce Cr (VI) to Cr (III), turning itself into iron oxide or hydroxide. The whole process is an exothermic reaction, accompanying chemical reduction and physical adsorption. And Cr (III) is fastened on the appearance by deposition of chromium hydroxide or ferrochromium complex precipitation, which greatly reduces the total chromium content in the aqueous solution. Herein, as a new composite adsorbent, nZVI@EG shows promising prospects of practical applications in water contamination and environmental remediation.

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