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 Enhanced As(III) sequestration using nanoscale zero-valent iron modified by combination of loading and sulfidation: characterizations, performance, kinetics and mechanism

2021 ◽  
Author(s):  
Shun Cheng ◽  
Hong Liu ◽  
Emmanuella Anang ◽  
Chunxia Li ◽  
Xianyuan Fan
Keyword(s):  
Arsenic Removal ◽  
Average Particle Size ◽  
Zero Valent Iron ◽  
Maximum Adsorption Capacity ◽  
Average Particle ◽  
Order Kinetic ◽  
Arsenic Adsorption ◽  
Nanoscale Zero Valent Iron ◽  
Wide Ph Range ◽  
Co Precipitation

Abstract Nanoscale zero-valent iron (nZVI) and sulfides have been confirmed to be effective in arsenic sequestration from aqueous solution. In this study, attapulgite supported and sulfide-modified nanoscale zero-valent iron (S-nZVI@ATP) are synthesized to realize the superposition effect of enhanced arsenic sequestration. The results indicated that nZVI clusters were well disaggregated and the BET specific surface area increased from 19.61 m2·g−1 to 46.04 m2·g−1 of S-nZVI@ATP, resulting in an enhanced removal efficiency of arsenic from 51.4% to 65.1% at 20 min. The sulfides in S-nZVI@ATP mainly exists as mackinawite (FeS) and causes the spherical nanoparticles exhibiting a larger average particle size (94.6 nm) compared to bare nZVI (66.0 nm). In addition, S-nZVI@ATP exhibited a prominent ability for arsenic sequestration over a wide pH range of 3.0–6.0. The presence of anions SO42− and Cl− can enhance the arsenic removal whereas HCO3− inhibited it. The arsenic adsorption by S-nZVI@ATP could be explained by the pseudo-second-order kinetic model and the Langmuir model, with the maximum adsorption capacity of 193.8 mg·g−1. The mechanism of As(III) sequestration by S-nZVI@ATP involved multiple processes, mainly including precipitation conversion from FeS to As2S3, surface-complexation adsorption and co-precipitation.

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.

Changes in Particle Size Distributions on a Fixed Bed of Granular Activated Carbon

1986 ◽  
Vol 18 (1) ◽  
pp. 31-42 ◽  
Author(s):  
E. A. Shpirt ◽  
K. T. Alben
Keyword(s):  
New York ◽  
Particle Size ◽  
Activated Carbon ◽  
Average Particle Size ◽  
Fixed Bed ◽  
Treatment Plant ◽  
Granular Activated Carbon ◽  
Water Treatment Plant ◽  
Average Diameter ◽  
Average Particle

The particle size distribution at different bed depths of a fixed bed of granular activated carbon (GAC) has been monitored during 50 weeks of a pilot column run at the Waterford, New York potable water treatment plant. Initial backwashing resulted in significant stratification of GAC in the column: larger particles (average diameter 1.18 mm) settled in the bottom of the column (105 cm), and smaller particles (average diameter 0.97 mm) were concentrated near the top (24 cm), compared to samples of unstratified virgin Calgon F400 (average diameter 1.09 mm). During column loading and initial backwashing, more fines were created than were present in the virgin GAC (average 6.5% of GAC fines in the > 40 mesh fraction, compared to only 0.3% in the > 40 mesh fraction for virgin Calgon F400). After 50 weeks of service there was an overall trend toward a smaller average particle size (0.9 mm) with development of a more regular pattern of bed stratification (1.08 mm at the bottom and 0.75 mm at the top). These changes are attributed to breaking of large particles (12-20 mesh) and creation of intermediate size particles (20-30 and 30-40 mesh).

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.

scholarly journals Nanoscale Zero-Valent Iron for Sulfide Removal from Digested Piggery Wastewater

2014 ◽  
Vol 2014 ◽  
pp. 1-10 ◽  
Author(s):  
Sheng-Hsun Chaung ◽  
Pei-Fung Wu ◽  
Yu-Lin Kao ◽  
Weile Yan ◽  
Hsing-Lung Lien
Keyword(s):  
Activated Carbon ◽  
Adsorption Capacity ◽  
Surface Characterization ◽  
Iron Sulfide ◽  
Ph Effect ◽  
Zero Valent Iron ◽  
Laboratory Studies ◽  
Sulfide Removal ◽  
Nanoscale Zero Valent Iron ◽  
The Impact

The removal of dissolved sulfides in water and wastewater by nanoscale zero-valent iron (nZVI) was examined in the study. Both laboratory batch studies and a pilot test in a 50,000-pig farm were conducted. Laboratory studies indicated that the sulfide removal with nZVI was a function of pH where an increase in pH decreased removal rates. The pH effect on the sulfide removal with nZVI is attributed to the formation of FeS through the precipitation of Fe(II) and sulfide. The saturated adsorption capacities determined by the Langmuir model were 821.2, 486.3, and 359.7 mg/g at pH values 4, 7, and 12, respectively, for nZVI, largely higher than conventional adsorbents such as activated carbon and impregnated activated carbon. The surface characterization of sulfide-laden nZVI using XPS and TGA indicated the formation of iron sulfide, disulfide, and polysulfide that may account for the high adsorption capacity of nZVI towards sulfide. The pilot study showed the effectiveness of nZVI for sulfide removal; however, the adsorption capacity is almost 50 times less than that determined in the laboratory studies during the testing period of 30 d. The complexity of digested wastewater constituents may limit the effectiveness of nZVI. Microbial analysis suggested that the impact of nZVI on the change of microbial species distribution was relatively noticeable after the addition of nZVI.

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