Zero-valent Iron Particles Research Articles

Treatment of wastewater from the flocculation process of waste cutting fluid by zerovalent iron catalyst

Waste cutting fluids are considered as hazardous wastes because they contain numerous different components causing environmental problems. Normally, a flocculation method is applied to treat preliminarily. However, the output wastewater still needs treating further to meet the national standards of industrial wastewater before disposal. So, this research reports the secondary treatment stage of the waste cutting fluid collected from an industrial factory in Vietnam using zero valent iron (ZVI) catalyst. This catalyst was synthesized via a redox reaction between sodium borohydride (NaBH4) and ferric chloride (FeCl3). Key factors affecting the quality of the ZVI particles such as the concentration of the NaBH4 reductant, reaction temperature, and dropping rate were investigated systematically. At the optimum synthesis conditions, viz. the NaBH4 concentration of 0.2 M, reaction temperature of 25 oC and the dropping rate of 3 ml/min, the synthesized ZVI exhibited a narrow range of particle size distribution with a mean size of 3.9 μm, followed by a high surface area, and good catalytic activity. As a catalyst for secondary treatment of the waste cutting fluid, the synthesized ZVI demonstrated a moderate chemical oxygen demand (COD) removal performance of 49%, corresponding to COD reduction for from 4023 mg/l to about 2059 mg/l.

Design and optimization of a sequential and hybrid advanced oxidation process system using response surface methodology

Of different approaches for refinery effluent treatment, the application of Advanced Oxidation Processes (AOPs) (e.g. electro-Fenton) and nano Zero-Valent Iron (nZVI) particles have been of great interest lately. Associated constraints with these methods inspired the design of a sequential hybrid system by which higher treatment efficiency and less energy consumption were acquired compared to a conventional system. The hybrid system consisted of an electro-Fenton and an nZVI slurry system working in sequence. Both sub-systems were first optimized using the Response Surface Methodology (RSM), and the hybrid system was then designed accordingly. 94.06% of COD removal was achieved by the hybrid system in only 47.5 min at its optimum condition (CODinitial = 500 mg/L, [nZVI] = 0.9 g/L, and H2O2/Fe2+ = 3.6). Whereas it took more than 75 min for the single electro-Fenton system to acquire similar efficiency. GC–MS analysis also supported the superiority of the hybrid system over the conventional one.

Trichloroethylene remediation using zero-valent iron with kaolin clay, activated carbon and bacteria

Nanoscale particles of zero-valent iron were used to form a permeable reactive barrier whose performance in dechlorinating a solution of trichloroethylene was compared with that of a barrier formed from limestone. The iron was combined with kaolin by calcination. The test liquid contained sewage sludge, and also added NH4Cl and KH2PO4. The average removal rates of trichloroethylene and phosphorus over 365 days both exceeded 94%. Chemical oxygen demand was reduced by 92% and ammonium nitrogen by 43.6%. All were significantly greater than the removals with the limestone barrier. The ceramsite barrier retained 85% of its effectiveness even after 365 days of use. Dechloromonas sp. was the main dechlorinating bacterium, but its removal ability is limited. The removal of trichloroethylene in such a barrier mainly depends on reduction by the zero-valent iron and biodegradation. The results show that the prepared ceramsite is stable and effective in removing trichloroethylene from water. It is a promising in-situ remediation material for groundwater.

Disposal of MIEX desorbent at high salinity by ZVI/H2O2 Fenton-like system: Optimization, performance and mechanisms

Magnetic ion exchange resin (MIEX) pretreatment has been widely used to enhance the performance of waterworks, but the high-salinity organic desorbent produced during the resin regeneration is difficult to be safely disposed of. The present study aimed to investigate the removal of DOM and retention of salts from MIEX desorbent via zero-valent iron (ZVI)-assisted Fenton reaction. ZVI/H2O2 mediated Fenton reaction was further validated by various analytical approaches such as 3D-EEM, Molecular weight distribution, Zeta potential, size, dissolution of iron ions, etc. In batch experiments, 73.26% reduction of DOC and 97.66% of UV254 were achieved in 40 min at optimal H2O2 concentration (20 mM), 2 g/L dose of ZVI, and pH of 3, respectively. The removal of organics was ascribed to the direct oxidation of ZVI/H2O2 and flocculation of the iron released during the oxidation. It should be noted that the high concentration of Cl- in system favored the organic removal and its enhanced performance lied in the production and oxidation of HOCl/OCl-. The treated liquid can be reused to regenerate the saturated resin with only a small amount of salt supplementation to obtain a similar recovery performance to that of a freshly configured 10% NaCl solution. Moreover, the retrieval and utilization of ZVI particles and other properties of MIEX desorbent after ZVI/H2O2 treatment were all promising and up to the mark: after four reuses, the mineralization of organic matter differs by 8.81% from the first time, which could be compensated by supplying new ZVI. This research will facilitate the recycling of resin desorbate and expand the market for MIEX applications.

Polyethyleneimine stabilized nanoscale zero-valent iron-magnetite (Fe3O4@nZVI-PEI) for the enhanced removal of arsenic from acidic aqueous solution: Performance and mechanisms

Nanoscale zero-valent iron (nZVI) particles have a high removal affinity toward arsenic. However, particle agglomeration and surface passivation hinder their practical application in wastewater treatment. Herein, we report the design and synthesis of an economically viable polyethyleneimine stabilized nZVI-magnetite (Fe3O4@nZVI-PEI) that exhibits a fast and efficient removal of arsenic (As(III/V)) from wastewater. Microstructure analyses by SEM and TEM indicated that PEI efficiently minimized particle agglomeration. The higher the point of zero charge (pHpzc) value of Fe3O4@nZVI-PEI (∼9.4) over bare Fe3O4@nZVI (∼8.2) is indicative of the role of PEI in the sorption of the arsenic species. The experimental results showed a removal efficiency of 95.8% for As(III) and 90.5% for As(V) at an optimum pH of 3.0. The adsorption kinetics followed the pseudo-second-order and the equilibrium isotherm data fitted to the Sips model with the superior maximum adsorption capacities of 572.40 mg/g for As(III) and 548.80 mg/g for As(V). FTIR, XRD, and XPS analyses provided insight into the possible adsorption mechanism that arsenic is taken up by generating monodentate and bidentate inner-sphere complexes with -OH, electrostatic interactions with primary amines, and partial oxidation of As(III) to As(V). In contrast to Cl-, NO3-, and SO42-, PO43- showed a significant competitive effect on the sorption of both As(III/V) species. Overall, this work provides a practical and highly efficient approach for arsenic remediation in wastewater and contaminated soils, and simultaneously resolves the stabilization problems of nZVI nanoparticles.

Effects of operational parameters on methyl tert-butyl ether removal by permeable reactive barrier from polluted waters

Background: Recalcitrant organics remediation from water resources continues to be a significant environmental problem and there is a continued effort to demonstrate practicable and economical treatment options for pollution removal. Methods: In this study, the efficiency of the permeable reactive barrier (PRB) in a column reactor using zero-valent iron (ZVI) particles and sand mixture in the removal of methyl tert-butyl ether (MTBE) from aquatic phases was investigated. The system performance was MTBE removal while initial pH, reaction time, pollutant content, catalyst load, hydraulic loading rate (HLR), and the reaction rate constant were independent variables. Results: The results showed that the process efficiency decreased by increasing pH, HLR, and pollutant concentration. In this case, the optimal conditions were obtained at pH=7, HLR=0.23 m3 /m2 ·d, and C0=1 mg/L, which achieved a remarkable removal efficiency up to 90.32%. The high nitrate concentrations and hardness as intervening factors reduced process efficiency to less than 44.61 and 51.4%, respectively. The lack of interfering factors had a considerable effect on the reaction rate of MTBE reduction, which is approximately 2.65 and 4.11 times higher than that in the presence of calcium hardness and nitrate, respectively. Conclusion: The PRB technology can be suggested as a reliable and robust system to remediate groundwater containing hydrocarbons based on filling media and hydraulic conditions.

In Situ Synthesis of Zero-Valent Iron-Decorated Lignite Carbon for Aqueous Heavy Metal Remediation

Lignite’s large abundance, physicochemical properties and low cost are attractive for industrial wastewater remediation. However, directly applying lignite for wastewater treatment suffers low efficiency. Here, we synthesize highly efficient zero-valent iron (ZVI)-decorated lignite carbon through the in-situ carbonization of a lignite and FeCl2 mixture for heavy metal removal. The effect of carbonization temperature on the morphology, structure and crystallite phases of ZVI-decorated lignite carbons (ZVI-LXs) was investigated. At an optimized temperature (i.e., 1000 °C), ZVI particles were found evenly distributed on the lignite matrix with the particles between 20 to 190 nm. Moreover, ZVI particles were protected by a graphene shell that was formed in situ during the carbonization. The synthesized ZVI-L1000 exhibited higher Cu2+, Pb2+ and Cd2+ stripping capacities than pristine lignite in a wide pH range of 2.2–6.3 due to the surface-deposited ZVI particles. The maximum Langmuir adsorption capacities of ZVI-L1000 for Cd2+, Pb2+ and Cu2+ were 38.3, 55.2 and 42.5 mg/g at 25 °C, respectively, which were 7.8, 4.5 and 10.6 times greater than that of pristine lignite, respectively. ZVI-L1000 also exhibited a fast metal removal speed (~15 min), which is ideal for industrial wastewater treatment. The pseudo-second-order model fits well with all three adsorptions, indicating that chemical forces control their rate-limiting adsorption steps. The reduction mechanisms of ZVI-L1000 for heavy metals include reduction, precipitation and complexation.

Fabrication and response optimization of Moringa oleifera-functionalized nanosorbents for the removal of diesel range organics from contaminated water.

The purpose of this research is to synthesize environmentally friendly nanosorbents for the novel adsorption of diesel range organics (DRO) from contaminated water. Central composite design (CCD) analysis of response surface methodology (RSM) was employed in a model fitting of the variables predicting the adsorption efficiency of Moringa oleifera-functionalized zerovalent iron particles (ZINPs) for the removal of DRO. The effects of the reaction parameters on the response were screened using 24 factorial designs to determine the statistically significant independent variables. A quadratic model predicting the DRO adsorption efficiency of ZINPs with an F value of 276.84 (p value < 0.0001) was developed. Diagnostic plots show that the predicted values were in excellent agreement with actual experimental values (R2 = 0.99). The maximum percentage removal of DRO of 92.6% was achieved after optimization, using the synthesized ZINPs after 8h of contact between DRO substrates and ZINPs at pH of 8, the temperature of 25°C, with an adsorbent dosage of 2g/L and at composite desirability of 1. Characterization of ZINPs revealed the formation of quasi nanospheres and nanocubes with an average particle diameter of 50.9 ± 9.7, a crystallite size of 15.31nm, a crystallinity index of 32.47% and a pore width of 75.69-88.59nm. The adsorption equilibrium data modelling of ZINPs for adsorption of DRO was best described by Langmuir isotherm with the maximum monolayer coverage capacity of 7.194mg/g. The separation factor [Formula: see text], indicated favourable adsorption. The adsorption kinetic data were consistent with pseudo-second-order kinetics indicating probable chemisorption.

Promotion of ciprofloxacin adsorption from contaminated solutions by oxalate modified nanoscale zerovalent iron particles

• Oxalate addition greatly enhanced the removal of CIP by Fe 0 from 45.04% to 95.74%. • 0.3 g L −1 of Fe 0 , 0.3 mM of oxalate, pH 7, and 25℃ are the optimal removal conditions. • Oxalate addition promoted the adsorption of CIP instead of oxidation by ROS. • The maximum adsorption capacity of CIP by (Fe 0 /oxalate) system is 294.66 mg g −1 . • Oxalate addition significantly reduced the treatment cost from ¥65.72 to ¥29.12. Water contamination by ciprofloxacin (CIP) is a global and emerging issue because it increases the risk of infection by antimicrobial resistant bacteria. CIP removal from water by iron nanoparticles (Fe 0 ) with the presence of oxalate hasn't been reported yet. The present study demonstrated that the addition of oxalate to Fe 0 nanoparticles improved the removal of 100 mg L −1 of CIP from 45.04% to 95.74% under the following optimum conditions: [Fe 0 ] = 0.3 g L −1 , [oxalate] = 0.3 mM, initial pH = 7, and temperature = 25 ℃. Furthermore, the experimental results illustrated that high concentrations of dissolved oxygen in the aqueous solution greatly decreased the removal efficiency of CIP by (Fe 0 /oxalate) system from 97.69% (N 2 atmosphere) to 67.47%. Similarly, the performance of (Fe 0 /oxalate) system declined from 95.43% to 85.23% because of increasing the ionic strength of the solution from 0 to 100 mM. In contrast, the influence of humic acid (0 – 40 mg L −1 ) on the removal of CIP by (Fe 0 /oxalate) system was neglectable. Also, the negative impact of coexisting ions on the competence of (Fe 0 /oxalate) system was in the following order: Mg 2+ > NO 3 – > SO₄ 2- > Ca 2+ > CO 3 2– > K + . In addition, the desorption experiments and the results of SEM-EDS, XRD, and FTIR revealed that physisorption and chemisorption were responsible for CIP removal by (Fe 0 /oxalate) system as the addition of 0.3 mM of oxalate boosted the surface complexation between Fe 0 nanoparticles and the carboxylic, ketone, and piperazinyl groups in CIP. These results were supported by the outcomes of kinetics, isotherm, and thermodynamic analysis. Moreover, oxalate addition significantly reduced the treatment cost of 1 L of 100 mg L −1 of CIP and the generated sludge by approximately 55.68% and 57%, respectively. Finally, this study proved that (Fe 0 /oxalate) system is inexpensive, practical, and more efficient than most of the reported Fe 0 -based systems with a maximum adsorption capacity of 294.66 mg g −1 .

Effective phosphate removal from sewage water using zerovalent iron nanomaterial as an adsorbent

Abstract In recent times, nano zerovalent iron (nZVI) particles have attracted significant attention from researchers for their effectiveness in removing phosphates, a hazardous contaminant found in groundwater and surface water. nZVI possesses some excellent characteristics such as high reactivity, high surface area, and effective surface-to-volume ratio. In this study, nZVI was characterized by X-ray diffraction, Brunauer–Emmett–Teller (BET) surface area analyzer, Fourier transform infra-red (FT-IR), field emission scanning electron microscopy (FESEM), and transmission electron microscopy (TEM) techniques. The effect of variations in nZVI dosage, pH, ionic strength, and coexisting anions on the removal of phosphate from laboratory-based synthetic water was explored. A maximum phosphate removal efficiency of 96% was achieved at an initial phosphate concentration of 25 mg/L, an nZVI dosage of 560 mg/L, and a shaking rate of 500 rpm, and pH 2 was attained within 120 min. Kinetic and equilibrium studies revealed that the adsorption of phosphate follows a pseudo-2nd-order kinetic model and a Temkin isotherm model, respectively. A thermodynamic study confirmed that phosphate adsorption is a spontaneous and endothermic process. Finally, nZVI was proved to be stable up to five cycles. nZVI was further applied for the removal of phosphate from sewage water, which was collected from Saheb bandh, Purulia district of West Bengal, Eastern India.

Toxicity of zero-valent iron nanoparticles to soil organisms and the associated defense mechanisms: a review.

Nanoscale zero-valent iron particles (NZVI) are widely used in a variety of industries owing to their advantageous mechanical, physical, and chemical properties. These particles can be released into environmental media, including water, soil, and air, through several pathways. NZVI in the ecosystem can be taken up, excreted and distributed within organisms, which is harmful to plants, animals and humans. Plants play a significant role as producers in the ecological circle and can both positively and negatively affect the ecological behavior of NZVI. Therefore, understanding the relationship between plants and NZVI is likely to be of great value for the assessment of NZVI-associated risks and future research directions. In this review, we summarize the current knowledge on the uptake, distribution, and accumulation of NZVI in plants; the phytotoxicity triggered by NZVI exposure at the physiological, biochemical, and molecular levels; and the defense mechanism used by plants to defend against NZVI-induced insults. We further discuss the toxic effects of NZVI on soil animals and microorganisms as well as the risk posed by the presence of NZVI in the food chain.

Zero valent iron or Fe3O4-loaded biochar for remediation of Pb contaminated sandy soil: Sequential extraction, magnetic separation, XAFS and ryegrass growth

In this study, the feasibility of using zero-valent iron (ZVI) and Fe3O4-loaded biochar for Pb immobilization in contaminated sandy soil was investigated. A 180-day incubation study, combined with dry magnetic separation, chemical extraction, mineralogical characterization, and model plant (ryegrass, namely the Lilium perenne L.) growth experiment was conducted to verify the performance of these two materials. The results showed that both amendments significantly transferred the available Pb (the exchangeable and carbonates fraction) into more stable fractions (mainly Fe/Mn oxides-bound Pb), and ZVI alone showed a better performance than the magnetic biochar alone. The magnetic separation and extended X-ray absorption fine structure (EXAFS) analysis proved that Fe (oxyhydr)oxides on aged ZVI particles were the major scavengers of Pb in ZVI-amended soils. In comparison, the reduced Pb availability in magnetic biochar-amended soil could be explained by the association of Pb with Fe/Mn (oxyhydr)oxides in aged magnetic biochar, also the possible precipitation of soil Pb with soluble anions (e.g. OH−, PO43−, and SO42−) released from magnetic biochar. ZVI increased ryegrass production while Fe3O4-loaded biochar had a negative effect on the ryegrass growth. Moreover, both markedly decreased the Pb accumulation in aboveground and root tissues. The simple dry magnetic separation presents opportunities for the removal of Pb from soils, even though the efficiencies were not high (17.5% and 12.9% of total Pb from ZVI and biochar-treated soils, respectively). However, it should be noted that the ageing process easily result in the loss of magnetism of ZVI while the magnetic biochar tends to be more stable and has high retrievability during the dry magnetic separation application.

Synthesis and Characterization of Zero Valent Iron Prepared Using Green Synthesis Method

This research was conducted to develop a green synthesis method for zero valent iron (ZVI) preparation. The ZVI was synthesized by reacting FeCl2 with polyphenols extracted from kepok banana peels. This polyphenol extraction process was carried out using three different solvents, namely: water, chloroform, and ethyl acetate. Gas chromatography mass spectroscopy test showed three main phenolic compounds contained in the banana peel extract, namely: 2-methoxy-4-vinylphenol, 4-methoxy-2-vinylphenol, and 2-methoxy-5-vinylphenol. The optimum composition of FeCl2 and polyphenol was 3:2. Fourier transform infra red spectroscopy data confirmed that the synthesized ZVI contains organic compounds having –OH and C=O groups which are assumed to be capping agents that can maintain stability. This has also been supported by the results of the energy dispersive X-ray analysis where there are carbon atoms (C) and oxygen atoms (O) in ZVI. The ZVI particle size was uneven and form a compact solid. The largest particle size distribution of ZVI is in the range of 234.49 nm - 407.49 nm with the average size of ZVI beings 616.26 nm. The results of the XRD analysis have also confirmed the formation of a simple cubic ZVI with fine crystallite size of ca 26.64 nm.

Porous boron nitride intercalated zero-valent iron particles for highly efficient elimination of organic contaminants and Cr (VI)

Developing novel bifunctional materials to high efficiently degrade organic pollutants and eliminate hexavalent chromium (Cr (VI)) is significantly desired in the wastewater treatment field. The porous boron nitride (p-BN) was fabricated by a two-stage calcination strategy and was innovatively employed to support zero-valent iron (ZVI), achieving the bifunctional material (p-BN@ZVI) to degrade carbamazepine (CBZ) and eliminate Cr (VI). p-BN@ZVI could degrade more than 98% CBZ in 6 min with the high apparent first-order constant (kobs) of 0.536 min−1, almost 5 times higher than that of the ZVI/PMS system and outperformed most previous reported ZVI supported catalysts, which was mainly ascribed to the fact that the introduction of p-BN with high surface area (793.97 m2/g) improved the dispersion of ZVI and exposed more active sites. Quenching tests coupled with electron paramagnetic resonance (EPR) suggested that •OH was the major reactive oxygen species with a contribution of 71.6%. Notably, the p-BN@ZVI/PMS system expressed low activation energy of 8.23 kJ/mol and reached a 65.69% TOC degradation in 20 min even at 0 °C. p-BN@ZVI possessed remarkable storage stability and could still degrade 92.3% CBZ despite three-month storage. More interestingly, p-BN@ZVI was capable to eliminate 98.1% of 50 mg/L Cr (VI) within 5 min through adsorption and reduction, where nearly 80% Cr (VI) was transformed to Cr (III), and exhibited the maximum Cr (VI) elimination capacity of 349 mg/g. This study provides new insights into the efficient organic contaminants degradation and Cr (VI) elimination in the treatment of wastewater.

A novel way for hydroxyl radicals generation: Biochar-supported zero-valent iron composite activates oxygen to generate hydroxyl radicals

As the cheapest oxidant, it is significant to investigate how to use oxygen to generate hydroxyl radicals (·OH) effectively. Though the oxidation of zero-valent iron (ZVI) by O2 can generate ·OH, the yield is too low for application. Here, we successfully prepared the biochar-supported zero-valent iron composites (BC-ZVI) and applied them to generate ·OH. The ·OH quantitative experiments presented that the BC-ZVI (1:1) has the strongest ability to activate oxygen to generate ·OH among the different mass ratios of BC-ZVI, which can reach 20.19 μM at the concentration of 1.0 g/L. Materials characterization results demonstrated that the uniform dispersion of ZVI particles and the catalytic capacity of biochar led to the superior performance of BC-ZVI (1:1) in ·OH generation. The O2·- and H2O2 are proved to be the intermediate reactive oxygen species in the generation of ·OH through reactive oxygen species (ROS) capture experiments. Our findings presented that the BC-ZVI (1:1) exhibited high performance in TC removal (186.26 mg/g) and the role of ·OH was demonstrated by quenching experiments. Overall, those results indicated that BC-ZVI (1:1) composite could be a promising material to generate ·OH and remove pollutants.

Encapsulating carbon-coated nano zero-valent iron particles with biomass-derived carbon aerogel for efficient uranium extraction from uranium-containing wastewater

Encapsulating nano zero-valent iron particles with biomass-derived carbon is a promising strategy to achieve efficient uranium extraction by avoiding agglomeration and oxidation of nano zero-valent iron. Herein, we develop distinctive carbon-encapsulated nano zero-valent iron particles with konjac glucomannan-derived carbon aerogel for reduction-assisted uranium extraction. The nano zero-valent iron particles encapsulated in konjac glucomannan-derived carbon are composed of γ-Fe and a small part of α-Fe, in which γ-Fe with a stable carbon shell reduces the passivation rate, and the konjac glucomannan-derived carbon support prevents the nano zero-valent iron particles from agglomerating. U(VI) enrichment ratio via carbon-encapsulated nano zero-valent iron particles with konjac glucomannan-derived carbon aerogel reached up to 90.1% within 60 min in 200 mg/L uranium-containing wastewater, with U(VI) enrichment capacity of 720.8 mg/g. The mechanistic research revealed the oxygen-containing functional groups on konjac glucomannan-derived carbon confine UO22+, electrons on the nano zero-valent iron particles further transferred to konjac glucomannan-derived carbon, thereby realizing the reduction and fixation of uranium. Carbon-encapsulated nano zero-valent iron particles with konjac glucomannan-derived carbon aerogel can be a promising adsorption-reduction coupling material for multi-environment systems, providing a successful example for the purification of uranium-containing wastewater.

Choose your amendment wisely: Zero-valent iron nanoparticles offered no advantage over microparticles in a laboratory study on metal immobilization in a contaminated soil

The potential use of zero-valent iron (ZVI) nanoparticles (i.e., <100 nm in size) for the remediation of metal-contaminated soils has sparked a flurry of research in recent years. However, even reading a large number of these papers cannot completely dispel doubts that ZVI nanoparticles are indeed superior to ZVI microparticles (e.g., iron powder or grit) in immobilizing metals and metalloids in soils. Our primary objective was to compare the adsorption properties of iron-based amendments (ZVI micro- and nanoparticles, natural iron oxides) supplied in a biochar matrix in soils contaminated by a copper-nickel (Cu/Ni) smelter on the Kola Peninsula in Russia. The following iron-containing amendments were added to the studied soil: a composite of ZVI nanoparticles and biochar (synthesized by pyrolysis of iron-impregnated biochar), a mixture of iron powder (i.e., ZVI microparticles) with biochar, and a mixture of iron oxides (from natural ferromanganese nodules) with biochar. Perennial ryegrass (Lolium perenne L.) was grown in pots on untreated and amended soils for 21 days under laboratory conditions. In our time-limited study, ZVI nanoparticles did not prove superior to ZVI microparticles or natural iron oxides at immobilizing metals in copper- and nickel-contaminated soil. In other words, ZVI particles size was irrelevant under the experimental setup of this study in its effects on exchangeable metal concentrations, foliar elemental concentrations, and plant growth.

Effect of zero-valent iron and iron-carbon particles on the denitrification efficiency of anammox process under gradual cooling conditions

Nitrogen pollution in water bodies mainly comes from industrial wastewater discharge, urban sewage discharge, and agricultural pollution. Nitrogen in a nitrate form can adversely affect human health and the environment. In this study, the effects of adding zero-valent iron (ZVI) and iron-carbon (Fe-C) particles on the performance of the anaerobic ammonia oxidation (anammox) process and sludge properties under gradual cooling conditions were investigated. Inoculating a portion of mature anammox granular sludge can speed up the rapid start of anammox. After 90 d of domestication and cultivation, the sludge granulation was achieved, and the influent load was increased. After 30 d of incubation, the total nitrogen (TN) removal efficiency can reach 95.08%. Through batch tests, the short-term effects of adding ZVI and Fe-C particles on anammox sludge were studied. It was found that when 100 mg/L dosage of ZVI was added, the denitrification effect of anammox sludge is the best. When Fe-C particles with Fe/C ratio of 2:1 were added, the anammox sludge had the best denitrification effect. Fe-C particles addition increased the pH of the reaction environment and sludge activity was affected. Continuous flow experiments under gradual cooling conditions showed that the effect of adding Fe-C particles on anammox was better than that of ZVI. After adding ZVI under 15 °C, NH 4 + -N and NO 2 - -N removal efficiency was 78% and 86%. Compared with the low temperature non-dosing ZVI, TN removal load was 1.77 kg/(m 3 ·d), and efficiency was improved by 10.2%. Addition of Fe-C particles promoted the denitrification efficiency, NH 4 + -N and NO 2 - -N removal efficiency was 83.90% and 88.84%. As compared to control the TN removal load was 1.90 kg/(m 3 ·d), and efficiency was improved by 8.4%. The sludge concentration showed a positive correlation with temperature. Results from this study show that simple addition of ZVI and Fe-C particles can stimulate microorganisms to secrete more EPS even under lower temperature. The outcomes of study are significant for wastewater management and pollution control in the waterbodies.

Transformation of sulfidized nanoscale zero-valent iron particles and its effects on microbial communities in soil ecosystems

Sulfidized nanoscale zero-valent iron (S-nZVI) is a promising material for in situ soil remediation. However, its transformation (i.e., aging) and effects on the microbial community in soil ecosystems are largely unknown. In this study, S-nZVI having low (S-nZVI (L)) and high sulfur-doping (S-nZVI (H)) were incubated in soil microcosms and bare nZVI was used as a control. Their aged products were characterized using microspectroscopic analyses and the changes in the corresponding soil microbial community were determined using high-throughput sequencing analyses. The results indicate that severe corrosion of both bare and S-nZVI occurred over 56 days of aging with significant morphological and mineral changes. Magnetite, lepidocrocite, and goethite were detected as the main aged products. In addition, sulfate ions, pyrite, and iron polysulfide were formed in the aged products of S-nZVI. Cr(VI) removal test results indicated that S-nZVI(L) achieved the best results after aging, likely because of the optimal FeS arrangement on its nanoparticle surfaces. The presence of nZVI and S-nZVI increased the abundance of some magnetotactic microorganisms and altered bacterial and fungal community structures and compositions. Moreover, the addition of S-nZVI enriched some bacterial and fungal genera related to sulfur cycling because of the presence of sulfide-bearing material. The findings reveal the transformation of S-nZVI during aging and its effects on microbial communities in soil ecosystems, thereby helping to the evaluation of S-nZVI application in soil remediation.

Combat antimicrobial resistance emergence and biofilm formation through nanoscale zero-valent iron particles

The emergence of antimicrobial resistance (AMR) and bacterial biofilm formation in water-related systems (e.g., drinking water distribution pipes) have been posing challenges to public health. Compared to conventional disinfection processes, nanomaterial-based approaches hold promise for mitigating AMR emergence and controlling biofilm formation. In this study, we investigated the performance and mechanisms of nanoscale zero-valent iron (nZVI) and its derivates (carboxymethyl cellulose-nZVI, oxidized or “Aged” nZVI, and Fe3O4 nanoparticles) on preventing AMR emergence and biofilm formation. Results show that the long-term exposure to subminimum inhibitory concentrations of nanoparticles except for Fe3O4 are able to prevent AMR emergence and biofilm formation. Except for Fe3O4, other nZVI nanoparticles are also capable of eradicating pre-established biofilms. The capability of these nanoparticles against AMR and biofilm can be attributed to the overproduction of reactive oxygen species, cell membrane damage and repression of efflux pumps. Collectively, our findings suggest that nZVI nanoparticles are promising alternatives to combat bacterial AMR emergence and biofilm formation in water-related systems.