Zero-valent Iron Particles Research Articles

Integrated green complexing agent and biochar modified nano zero-valent iron for hexavalent chromium removal: A characterisation and performance study

In this study, nano zero-valent iron (nZVI) was loaded on biochar (BC) prepared from recycled waste peanut shells. The loaded BC in the nZVI@BC composite was assumed to weaken the agglomeration of nZVI and the environmentally-friendly complexing agents sodium citrate (Cit) and sodium carboxymethyl cellulose (CMC) were used to establish Cit-nZVI@BC and CMC-nZVI@BC for the effective removal of Cr(VI) from aqueous environments. The characterisation results suggested that Cit and CMC not only inhibited the oxidation of nZVI, but also effectively improved its reactivity. The experimental results demonstrated that the Cr(VI) removal efficiency by nZVI was less than 20%, while CMC-nZVI@BC enhanced the Cr(VI) removal efficiency to 80.73%, because CMC was coated on the nZVI surface for anti-passivation and improved the surface activity of nanoparticles. In addition, the Cr(VI) removal efficiency reached almost 100% with Cit-nZVI@BC, and the citrate dissociated the passivation layer on the surface of the zero-valent iron particles to ensure the reactivity of the zero-valent iron. The reaction mechanism of Cit-nZVI@BC includes adsorption, reduction, and co-precipitation, whereas CMC-nZVI@BC also involves surface complexation reactions. The kinetic studies revealed that the removal of Cr(VI) by Cit-nZVI@BC and CMC-nZVI@BC followed the second-order reaction kinetic model, and the reaction rates of Cit-nZVI@BC and CMC-nZVI@BC were both higher than that of nZVI. The results indicate that the prepared systems are promising for Cr(VI) remediation in contaminated environments.

Removal of Organoselenium from Aqueous Solution by Nanoscale Zerovalent Iron Supported on Granular Activated Carbon

Nanoscale zerovalent iron particles (nZVI) immobilized on coconut shell-based granular activated carbon (GAC) were studied to remove organoselenium from wastewater. A chemical reduction technique that involves the application of sodium borohydride was adopted for the adsorbent preparation. The texture, morphology and chemical composition of the synthesized adsorbents were analyzed with a scanning electron microscope (SEM), nitrogen adsorption–desorption isotherms and X-ray diffraction (XRD). Batch experiment with various pHs and contact times were conducted to evaluate nZVI/GAC adsorption performance. The results showed that nZVI/GAC has a strong affinity to adsorb selenomethionine (SeMet) and selenocysteine (SeCys) from wastewaters. The maximum removal efficiency for the composite (nZVI/GAC) was 99.9% for SeCys and 78.2% for SeMet removal, which was significantly higher than that of nZVI (SeCy, 59.2%; SeMet, 10.8%). The adsorption kinetics were studied by pseudo-first-order (PFO) and pseudo-second-order (PSO) kinetic models. Amongst the two, PSO seemed to have a better fit (SeCy, R2 > 0.998; SeMet, R2 > 0.999). The adsorption process was investigated using Langmuir and Freundlich isotherm models. Electrostatic attraction played a significant role in the removal of organoselenium by nZVI/GAC adsorption. Overall, the results indicated that GAC-supported nZVI can be considered a promising and efficient technology for removing organoselenium from wastewater.

Green synthesis of Fe0 nanoparticles using Eucalyptus grandis leaf extract: Characterization and application for dye degradation by a (Photo)Fenton-like process

Zero-valent iron nanoparticles (EGnZVI) were synthesized using Eucalyptus grandis (EG) leaf extract as a reducing/stabilizing agent. The studied materials (EG leaves, extract and EGnZVI) were characterized using the XRD, FTIR, Raman spectroscopy, SEM, TEM/EDS techniques. The results indicate that several organic compounds, including phenolics, present in the EG leaves were successfully extracted and incorporated into the structure of the material, possibly promoting the capping and stabilization of the formed zero-valent iron particles. The EGnZVI presented low crystallinity, varied size (50–500 nm), approximately spherical shape, and formed aggregates. The EGnZVI were utilized in the removal of the Direct Red 80 (DR80), an azo dye. The effects of the temperature (15–35 °C), initial DR80 concentration (10–250 mg L−1), initial pH (2.5–8.5), the doses of H2O2 (0.5–5 mmol L−1) and EGnZVI (0.2–10 mg L−1), and the incidence of UV-light were evaluated. The EGnZVI did not present reactivity towards the DR80 in the absence of H2O2. However, in the presence of H2O2, the EGnZVI was highly efficient at removing the DR80 at slightly acidic pH0 values (4 and 5.5). Under these pH0 conditions, the EGnZVI/Fenton process proved to be more effective than the classic homogenous Fenton. Finally, in the presence of the UV-light, the process was highly efficient throughout the studied pH0 interval, with increased removal rates. Therefore, the nZVI/Fenton process, using the synthesized material, presents itself as a promising alternative for the degradation of organic pollutants, and the incidence of UV light can considerably improve its efficiency.

Degradation of atrazine by Ni-doped sulfidated microscale zero-valent iron: Mechanistic insights for enhanced reactivity and selectivity

Sulfidation of microscale zero-valent iron particles (S/mZVI) has been considered as a general means to enhance its reactivity and selectivity. However, further improving of S/mZVI over water while still maintaining high reactivity with target contaminants is still a great challenge. In this study, Ni and Na2S were chosen as the catalyst and sulfidation regent, respectively, to synthesize three different kinds of nickel-sulfidated composite mZVI particles (NSC-mZVI), namely, post-sulfidation (Ni/mZVI-S), pre-sulfidation (S/mZVI-Ni), and co-sulfidation (Ni/S-mZVI), by adjusting the sequence of nickel doping and sulfidation. The reactivity and selectivity performance of NSC-mZVI toward atrazine (ATZ) in groundwater were compared, and the underlying mechanisms for the enhancement effect of ATZ and selectivity were also elucidated. Compared with S/mZVI, Ni/S-mZVI not only further increased the ATZ removal rate, but also reduced the hydrogen accumulation, which simultaneously improved the reactivity and selectivity of target contaminants. The enhanced removal rate of ATZ by Ni/S-mZVI could be ascribed to the generated atom hydrogen and the direct reduction of Fe0 core mediated by the electron transfer of FeS2 and Fe3O4. Meanwhile, the reduced hydrogen evolution reaction (HER) of Ni/S-mZVI can be explained by that Fe oxides conducting minor electrons mediated HER. The pH value of Ni/S-mZVI eventually reached 5.1 with high release of Fe2+. Overall, bimetallic modification of S/mZVI is a promising strategy to improve its reactivity, selectivity, and longevity for groundwater remediation.

Effects of different particle size of zero-valent iron (ZVI) during anaerobic digestion: Performance and mechanism from genetic level

Although zero valent iron (ZVI) has been widely studied as an additive in anaerobic digestion, the effect of ZVI particle size on anaerobic methane production and the mechanism by which this occurs have not been reported. This study investigated the effects of ZVI particles with different diameters (0.1 μm to 250 μm) on the glucose-substrate anaerobic digestion process. It was found that different particle sizes of ZVI had different optimal dosages, as 2 g/L of 48 μm ZVI increased methane production by 84.12% when compared with the blank group, whereas ZVI of 0.1 μm reached its optimal dosage at 0.5 g/L, increasing methane production by only 37.32%. Further study of the mechanism showed that 4 μm ZVI could increase the abundance of bacteria Bacteroidota and Proteobacteria (from 1.46% and 0.07% to 15.56% and 2.27%, respectively) and Archaea Methanosaeta (from 3.59% to 51.64%). Gene’s prediction showed that ZVI particles with a size range of 4–48 μm could facilitate cell replication and increase enzyme activity involved in methane production. Additionally, it could mediate direct interspecies electron transfer between fermentative bacteria and methanogens while avoiding cell lysis caused by the nano effect.

Wet Milling of Zerovalent Iron in Sulfide Solution: Preserving and Securing the Metallic Iron

Herein, a critical problem regarding the milling of zerovalent iron (ZVI) to produce fine ZVI particles is solved. During milling, ZVI is prone to be rapidly oxidized by oxygen, water, and other potential oxidants in the milling environment, which results in significant metallic iron (Fe(0)) loss and raises safety concerns. In this work, a sulfide solution (using Na2S) is introduced as the milling solvent; as benchmarks, ZVI milling under a pure aqueous solution (ZVI(W)) and organic solvents (pure ethanol, ZVI(E)) is also investigated. Produced ZVIs are characterized with six different techniques to assess their Fe(0) content, safety, reactivity, and reductive capacity. The obtained results show that the sulfide solution is effective in minimizing Fe(0) oxidation during milling; the Fe(0) content (∼63%, w/w) of ZVI milled in sulfide solution (ZVI(S)) is more than 10 times that of ZVI(W) after 5 h of milling. ZVI(S) is comparable to ZVI(E) in their Fe(0) contents, reductive reactivity, and capacity, but ZVI(S) is more stable and safer in use; an optimal Na2S concentration of 10 g Na2S/L is recommended. A mechanistic study shows that Fe(0) preservation in a sulfide solution results from a combined effect of the alkaline pH of the solution and the coating of iron sulfides on ZVI. This exploratory study demonstrates an original milling solution for a highly scalable, economical, and safe scheme to produce ultrafine and reactive ZVI with a high Fe(0) content for environmental applications.

Controllable shell corrosion of coated nanoscale zero valent iron induces long-term potentiation of its reactivity for uranium removal

Coating a soluble shell material on the surface of nanoscale zero-valent iron (nZVI) particles to eliminate the problems of agglomeration and rapid aqueous corrosion of Fe(0) in groundwater is an effective strategy for long-term maintaining uranium removal efficiency. However, the precise role of controllable shell corrosion on uranium removal mechanism remains unclear. In this study, a homogeneously dispersed Mg(OH)2 shell coated on nZVI (nZVI@Mg(OH)2) prepared by one-step surface precipitation was exploited to investigate the relationship between shell corrosion and uranium removal mechanism. The results confirm that nZVI with uniform coating shell (Mg(OH)2/Fe(0) = 1:2, mass ratio) was synthesized by simply mixing magnesium hydroxide with Fe2+ and NaBH4 solution under the flowing stream of N2 (25 ± 1 °C). The longevity and reactivity release rate of coated nZVI depended upon the initial pH value of the aqueous solution. At initial pH = 5, coated nZVI showed a high reduction activity, its ORP measured was 1.3 times that measured at initial pH = 3, and the duration could be prolonged to more than 4.5 times. The exposed Fe(0) core rapidly elimination U(VI) by synergistic attributed to the adsorptive (44.1%) and reductive (55.9%) processes after the passivation shell was eroded by reaction with H+. The results provide an efficient approach to improve the long-distance transport capacity and controllable release of nZVI, which can maintain its long-term reactivity in groundwater remediation.

Mechanistic insight into the adsorption of mercury (II) on the surface of red mud supported nanoscale zero-valent iron composite

Recently, nanoscale zero-valent iron (nZVI) particles have been efficiently used in the remediation of many heavy metals, yet potential agglomeration and loss of nZVI remain a critical area of research. In this study, we used red mud as a stable supporting medium to develop red mud modified nZVI to form (RM-nZVI) composite. We assessed its sorptive/reductive removal of mercury (Hg2+) from aqueous solutions. The RM-nZVI was synthesized through the reduction of ferric iron by sodium borohydride (NaBH4) in the presence of red mud. Morphological characterization of RM-nZVI confirmed its diffusion state with lesser aggregation. The RM-nZVI has the BET surface area, pore diameter, and pore volume as 111.59 m2g−1, 3.82 nm, and 0.49 cm3g−1, respectively. Adsorption of mercury (Hg2+) by RM-nZVI exhibits pH-dependent behavior with increased removal of Hg2+ with the increase in pH up to 5, and the removal rate decreased gradually as the pH increased from 5 to 10. Extensive characterization of RM-nZVI corroborated the evidence that the removal of Hg2+ was initially by rapid physical adsorption, followed by a reduction of Hg2+ to Hg0. The adsorption data were best fitted with Langmuir isotherm with R2 (correlation coefficient) > 0.99 with high uptake capacity of 94.58 (mg g−1). The novel RM-nZVI composite with enhanced sorptive and reductive capacity is an ideal alternative for removing Hg2+ from contaminated water.

Enhanced degradation of sulfamethoxazole by a modified nano zero-valent iron with a β-cyclodextrin polymer: Mechanism and toxicity evaluation

Rising concern about emerging and already persisting pollutants in water has urged the scientific community to develop novel remedial techniques. A new group of remediation methods is based on the modification of nanoscale zero-valent iron particles (nZVI), which are well known for treating volatile organic compounds and heavy metals. The properties of nZVI may be further enhanced by modifying their structure or surface using “green” polymers. Herein, nZVI was modified by a β-cyclodextrin polymer (β-CDP), which is considered an environmentally safe and inexpensive adsorbent of contaminants. This composite was used for the first time for the degradation of sulfamethoxazole (SMX). Coating by β-CDP not only enhanced the degradation of SMX (>95%, under 10 min) by the nanoparticles in a wide pH range (3–9) and enabled their efficient reusability (for three cycles) but also made the coated nZVI less toxic to the model bioindicator microalga Raphidocelis subcapitata. Moreover, degradation products of SMX were found to be less toxic to Escherichia coli bacteria and R. subcapitata microalga, contrary to the SMX antibiotic itself, indicating a simple and eco-friendly cleaning process. This research aims to further stimulate and develop novel remedial techniques based on nZVI, and provides a potential application in the degradation of antibiotics in a wide pH range. Moreover, the wealth of available cyclodextrin materials used for surface modification may open a way to discover more efficient and attractive composites for environmental applications.

Removal of Cd, Cu, Ni, and Pb from Nanoscale Zero-Valent Iron Amended Soil Using 0.1 M Acetic Acid Solution

Abstract The purpose of the study was to evaluate the possibility of removing heavy metal cations from single-metal spiked soil samples, which were pretreated with nanoscale zero-valent iron (nZVI) particles. Sandy soil was artificially contaminated with copper (Cu), cadmium (Cd), nickel (Ni), and lead (Pb). Contaminated soil samples were amended with different doses of nZVI (0.35, 0.70 and 1.05 %). A sequential extraction method was used to determine the fractionation of heavy metal cations in the control and nZVI amended soil samples. A solution of 0.1 M acetic acid (pH 3.0) was used to investigate the removal of heavy metals from control and nZVI-amended soil samples. The results showed that nZVI reduced the amount of metals in the exchangeable form and increased the proportion of these metals associated with amorphous iron (Fe) oxides. The results also showed that the removal efficiencies of heavy metals increased with increasing nZVI dose, that is, from 46.9 %, 5.77 %, 33.5 %, and 2.70 % to 55.9 %, 12.3 %, 46.2 %, and 3.79 % for Cd, Cu, Ni, and Pb, respectively. The study indicated that the application of nZVI in soil could be beneficial for subsequent removal of heavy metals from soil using 0.1 M acetic acid solution.

One-pot green synthesis of Zero-Valent iron particles supported on N-Doped porous carbon for efficient removal of organic pollutants via Persulfate Activation: Low iron leaching and degradation mechanism

In this work, zero-valent iron particles supported on nitrogen doped porous carbon (Fe-NPC) was successfully prepared by a green and convenient one-pot method through pyrolysis. In Fe-NPC/PS system, 96.44% orange II (OGII) was almost removed within 35 min, which was much higher than NPC and Fe-PC of 53.27% and 54.67%, respectively. Factors influencing the degradation process of OGII were investigated, including PS concentration, catalyst dosage, initial pH and ions disturbance. The radical quenching studies, electron paramagnetic resonance (EPR) measurements and chronoamperometry experiments verified the degradation mechanism of OGII in Fe-NPC/PS system included both radical and non-radical pathways in which •HO and SO4-· were the dominant active radicals and electron transfer was involved. Fe-NPC exhibited excellent tolerance toward a wide pH conditions with only 88 µg/L iron leaching in initial pH of 3.1, which was much lower than literature reported. The low iron leaching of Fe-NPC was attributed to the protection of carbon matrix and doped nitrogen in catalyst. Moreover, the surface CO group of the catalyst contributed to better performance in alkaline system. Furthermore, the supported iron species introduced magnetism into the catalyst for easily separation. The Fe-NPC/PS system also exhibited high removal efficiencies for Congo red (CR), Reactive blue 19 (RB 19), 4-Nitrophenol (4-NP) and tetracycline (TC). These results provided a sight for economically and efficiently fabricating stable iron based nitrogen doped porous carbon catalyst for water contaminant degradation.

Volatilization of Zn and Pb and preparation of integrated micro-electrolysis filter from copper slag and its application for removing Cr(VI) from aqueous solution

In this study, copper slag was treated by carbothermal reduction technology for preparing an integrated micro-electrolysis filter (IMEF) and recovery of Zn and Pb. The influence of roasting conditions on the volatilization of Zn and Pb, and on the performance of IMEF in removing Cr(VI) from water were studied. The results showed that increasing the roasting temperature, time, and dosage of coal facilitated the generation of zero-valent iron (ZVI) and volatilization of Zn and Pb. The IMEF, roasted at 1150 °C for 40 min with 25% anthracite, had the best reduction effect on Cr(VI), and the volatilization efficiencies of Zn and Pb were 97.38% and 96.77%, respectively. The prepared IMEF had a porous structure with a porosity of 75.20%. A great number of nano/micro-sized ZVI particles were generated on the surface of silicate pore, and had super reactivity. The removal of Cr(VI) was promoted by increasing IMEF dosage and solution temperature, and decreasing the pH of the Cr(VI) solution. The IMEF presented good mechanical strength and excellent long-term performance in removing Cr(VI). Cr(VI) was reduced into Cr(III) and then mineralized to FeCr2O4 during reaction.

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

Anodic coulometry of zero-valent iron nanoparticles

Nanoscale zero-valent iron (nZVI) particles are currently used for environmental remediation due to their ion sequester ability. This trait plus their magnetic behavior, and biocompatibility, makes them a promising alternative for heavy metal poisoning treatment, development of MRI dye, and drug delivery loads, among others. Their rapid passivation in aqueous media inhibit their differentiation from magnetite (Fe 3 O 4 ) by electrochemical methods, due to its surface oxide. Herein, this work is focused on applying the electrochemical method known as anodic particle coulometry (APC) to detect and characterize nZVI. During the experiments, current blips are observed as a result of a current increase when the electroactive nZVI particle reaches the Au working ultra-microelectrode surface. The integration of current blips resulted in a charge distribution between 4 pC and 5 pC, which correlates with nanoparticles in a size range between 70 nm and 100 nm. The size distribution obtained were compared to the size distribution found using scanning transmission electron microscopy (STEM) and nanoparticle tracking analysis (NTA). The results were compatible with the results obtained by the other two techniques. Characterization of nZVI particles using x-ray photoelectron spectroscopy (XPS) and electron energy loss spectroscopy (EELS) validate the presence of elemental iron which differentiates the material from magnetite. A chemical shift of ca. 1 eV from metallic iron to iron oxide (L 3 : 708 eV and L 2 : 721.2 eV versus L 3 : 709 eV and L 2 : 722.2 eV) is observed from EELS at nZVI particle center and edge, respectively. This suggests the presence of a passivated surface and a metallic core, a metallic core and oxide shell structure.

A zero-valent iron and zeolite filter for nitrate recycling from agricultural drainage water

Nitrate reduction to ammonium followed by ammonium capture and reuse, represent a new pathway to recycle nitrogen, prevent eutrophication, and to save energy used for industrial ammonium production. The present study investigates the principle of nitrogen recycling to agricultural drainage water using a coupled zero-valent iron (ZVI) and zeolite-based filter column system tested in laboratory and field continuous-flow experiments. A 40-day laboratory test showed 82% nitrate removal, of which 70% was converted to ammonium. In the following pilot scale field test, a total of 59.2 m3 (1700 pore volumes) drainage water with a nitrate concentration of 2–8 mg L−1 NO3−-N was filtrated. An oxidizing unit inserted after the ZVI unit removed iron(II) and optimized ammonium retention in the zeolite unit. Nitrate removal efficiency was 94% for the entire 56-day period with a slight pH increase (pH 8.9). All ammonium produced was retained by the zeolite unit. Formation of green rust carbonate (layered FeII–FeIII-hydroxide) was observed on ZVI particle surfaces, which may increase the redox capacity of the filter system by up to 50% and contribute to its cost-efficiency. Moreover, all phosphate in the influent waters with concentrations between 0.1 and 0.5 mg L−1 was retained due to sorption by iron oxides in the system. Corrosion products formed cause partial filter clogging and should be removed by regular cleaning and backflushing. In conclusion, the ZVI – zeolite coupled filter system serves as a promising and cost-effective technology for nutrient removal and ammonium retention from agricultural drainage water.

Nanoscale zero-valent iron particles supported on sludge-based biochar for the removal of chromium (VI) from aqueous system.

Biochar (BC) obtained by the co-pyrolysis of municipal sewage sludge (MSS) and sunflower seed shells (SSS) was utilized to support nanoscale zero-valent iron particles (nZVI) for the synthesis of a composite material (nZVI-BC) for Cr(VI) removal from aqueous systems. A series of characterization methods confirmed successful immobilization of nZVI on the surface of biochar with no aggregation. Batch experiments showed that the initial pH, initial Cr(VI) concentration, and nZVI-BC dose all significantly affected the Cr(VI) removal using nZVI-BC. The kinetics for Cr(VI) removal via nZVI-BC could be better explained by the pseudo-second-order (PSO) adsorption model. Adsorption isotherms analysis demonstrated the superior Cr(VI) removal capability of nZVI-BC in comparison to bare nZVI and BC. nZVI-BC can be reused after the regeneration process by applying 0.1 M H2SO4 and 0.1 M NaBH4 solutions. The reaction mechanism for Cr(VI) removal might involve its chemical reduction on the nZVI-BC surface. Overall, environmentally friendly nZVI-BC was highly efficient in Cr(VI) removal from aqueous systems.

Reactivity characterization of SiO2-coated nano zero-valent iron for iodoacetamide degradation: The effects of SiO2 thickness, and the roles of dehalogenation, hydrolysis and adsorption

The effect of SiO2-layer thickness in SiO2-coated nano zero-valent iron (nZVI) particles on the reactivity characteristics of iodoacetamide (IAcAm) degradation was evaluated. SiO2-layer thicknesses ranging from 3.6 to 27.3 nm were obtained through varying tetraethyl orthosilicate dosages of 0.001–1 M. The crystallinity, surface chemical composition, and physicochemical properties were evaluated for their effects on synergetic degradation mechanisms, dehalogenation, hydrolysis, and adsorption. At a thickness of 3.6 nm, the SiO2 layer offered the highest observed pseudo-first-order rate (kobs) and higher rates of IAcAm degradation were maintained under pH fluctuations (pH 5–7) and aerobic conditions compared to pristine nZVI. At this SiO2-layer thickness (3.6 nm), the rate of iron oxide-layer formation was reduced and the migration of reactive iron species (Fe0 and Fe2+) for the dehalogenation and hydrolysis reactions was enabled. In a single-solute solution, IAcAm elimination was greater than bromoacetamide and chloroacetamide elimination due to the weak ionic I–C bond. In mixed solute conditions, the hydrophobicity of chloroacetamide played a more significant role in competitive degradation through greater adsorption. The proportion of dehalogenation relative to hydrolysis during IAcAm degradation by pristine nZVI and SiO2-coated nZVI was approximately 0.6:0.4. Iodoacetic acid and acetic acid were detected as intermediates in the degradation pathway of IAcAm by pristine nZVI. In contrast, the SiO2 layer on nZVI can accelerate the transformation of IAcAm to acetamide and iodoacetic acid. The electrolyte background of tap water exhibited a slight inhibitory effect on the degradation of IAcAm for both nZVI and SiO2-coated nZVI.

Amplification effects of magnetic field on hydroxylamine-promoted ZVI/H2O2 near-neutral Fenton like system

This study has demonstrated an interesting amplification effect of magnetic field (MF) on the hydroxylamine (HA)-promoted zero valent iron (ZVI)/H2O2 Fenton-like system. Sulfamethoxazole (SMX) could be efficiently degraded at near neutral pH. Conditional parameters affecting the SMX degradation in the ZVI/H2O2/HA/MF system, e.g., pH and the dosages of ZVI, HA and H2O2, were investigated. Unlike the acid-favorable ZVI/H2O2 and ZVI/H2O2/HA systems, the MF-assisted system exhibited good performances even at pH up to 6.0 and highest degradation rate at pH of 5.0. •OH was still identified as the responsible oxidant. A mechanism involving the MF-enhanced heterogeneous-homogeneous iron cycle was proposed in the near-neutral ZVI/H2O2/HA system. Without MF, HA-induced reductive dissolution of the surface iron oxides occurred and thus leaded to homogeneous Fenton reactions. After the introduction of MF, the gradient magnetic field formed on the ZVI particles would induce the generation of concentration cells of Fe(II) and local corrosion of iron. Large amounts of aqueous and bounded Fe(II) catalyzed H2O2 to efficiently produce •OH, while HA maintained the surface and bulk cycles of Fe(II)/Fe(III). The result of study is expected to provide a green, energy-free method in improving the effectiveness of ZVI-based Fenton-like technologies at weak-acidic circumstances.

A novel green synthesis of zero valent iron nanoparticles (nZVI) using walnut green skin: characterisation, catalytic degradation and toxicity studies

ABSTRACT In the present study, green synthesised nanoparticles were used to activate persulphate and used for the oxidation of metronidazole (MTZ). In the process of green synthesis, the walnut green skin was used for the synthesis of zero-valent iron (nZVI) particles. These nanoparticles’ FESEM images revealed that they were spherical-shaped nanoparticles with a diameter ranging from 18 to 72 nm. Also, the FTIR spectra indicated the functional groups of polyphenols on the surfaces of the nZVI nanoparticles. Moreover, the XRD pattern illustrated that the synthesised particles possessed a high crystalline quality structure. According to the results, under the optimum conditions, the removal efficiency of the process in degradation of MTZ was 90.3%. LC-MS chromatography showed 7 by-products with reduced toxicity in the reactor outputs. It was found that the green synthesised nZVI had a good effect on the activation of the PS and the PS/nZVI process had a high ability in degradation of MTZ from aqueous solutions.

Nanoscale zero-valent iron particles supported on MIL-96: a novel material for adsorption-degradation of trichloronitromethane.

As an emerging class of nitrogenous disinfection by-products, halonitromethanes have caused public health concerns owing to their high toxicity. More and more attention has been paid to the new materials and technologies for the removal of halonitromethanes. In this study, a novel material, nanoscale zero-valent iron (nZVI) supported on MIL-96 (nZVI@MIL-96) with favorable stability and reusability, was synthesized and applied to the adsorption-degradation of trichloronitromethane (TCNM) in the water. The results revealed that almost all the TCNM could be removed under 20 mg/L nZVI@MIL-96 dosage with a wide temperature range. The optimum mass ratio of nZVI to MIL-96 was 1:2, and the TCNM adsorption-degradation followed a pseudo-first-order model. The coexisting ions, such as SO42-, PO43-, and NO3-, with high concentration brought adverse effects on the removal of TCNM; however, the effects of Cl- and CO32- were insignificant. The concentrations of aluminum and iron ions in water were all within the standard value after adsorption with the nZVI@MIL-96. The degradation mechanism of TCNM by nZVI@MIL-96 included two steps, namely, adsorption and degradation, and methylamine was the terminal dechlorination and denitration products. In a word, the as-prepared nZVI@MIL-96 nanoparticles demonstrated the capabilities as a material of adsorption-degradation of TCNM in the water.