Nanoscale Zero-valent Iron Research Articles

Removal of Aqueous Cr(VI) by Tea Stalk Biochar Supported Nanoscale Zero-Valent Iron: Performance and Mechanism

Removal of Aqueous Cr(VI) by Tea Stalk Biochar Supported Nanoscale Zero-Valent Iron: Performance and Mechanism

Sulfide-modified nanoscale zero-valent iron as a novel therapeutic remedy for septic myocardial injury

IntroductionMyocardial injury is a serious complication in sepsis with high mortality. Zero-valent iron nanoparticles (nanoFe) displayed novel roles in cecal ligation and puncture (CLP)-induced septic mouse model. Nonetheless, its high reactivity makes it difficult for long-term storage. ObjectivesTo overcome the obstacle and improve therapeutic efficiency, a surface passivation of nanoFe was designed using sodium sulfide. MethodsWe prepared iron sulfide nanoclusters and constructed CLP mouse models. Then the effect of sulfide-modified nanoscale zero-valent iron (S-nanoFe) on the survival rate, blood routine parameters, blood biochemical parameters, cardiac function, and pathological indicators of myocardium was observed. RNA-seq was used to further explore the comprehensive protective mechanisms of S-nanoFe. Finally, the stability of S-nanoFe-1d and S-nanoFe-30 d, together with the therapeutic efficacy of sepsis between S-nanoFe and nanoFe was compared. ResultsThe results revealed that S-nanoFe significantly inhibited the growth of bacteria and exerted a protective role against septic myocardial injury. S-nanoFe treatment activated AMPK signaling and ameliorated several CLP-induced pathological processes including myocardial inflammation, oxidative stress, mitochondrial dysfunction. RNA-seq analysis further clarified the comprehensive myocardial protective mechanisms of S-nanoFe against septic injury. Importantly, S-nanoFe had a good stability and a comparable protective efficacy to nanoFe. ConclusionsThe surface vulcanization strategy for nanoFe has a significant protective role against sepsis and septic myocardial injury. This study provides an alternative strategy for overcoming sepsis and septic myocardial injury and opens up possibilities for the development of nanoparticle in infectious diseases.

Post-sulfidation of biochar supported nanoscale zero-valent iron with different sulfur precursors: Reactivity and selectivity on tetrabromobisphenol A reduction

Herein, post-sulfidation method is applied for the first time to synthesize biochar supported sulfidated nanoscale zero valent iron (S-nZVI/BC), and the impact of sulfur (S) precursors (Na2S, Na2S2O3, and Na2S2O4) on the physicochemical properties, reactivity, selectivity, pH resistance, and long-term performance of S-nZVI/BC was investigated for tetrabromobisphenol A (TBBPA) degradation. Detailed characterizations indicated that S-nZVI/BC with different S precursors altered distribution/content of S species (i.e., S2−, Sn2−, and SO42−) in shell and core (>10 nm). The BC largely contributed to increase the sulfidation efficiency and dispersion of S-nZVI. The reactivity of S2−-nZVI/BC was ∼ 9.6 and ∼ 3.0–6.7 times higher than that of nZVI/BC and other S-nZVI/BCs, respectively, deriving from the higher Fe0 crystallinity, more hydrophobicity and proportion of reduced S species. Remarkably, the adverse effect of surface oxidized S species (i.e., SO42−) was more significant than the promoting effect induced by the surface reduced S species (i.e., S2− and Sn2−) on reactivity when there were excessive SO42− species. The selectivity of S2O42−-nZVI/BC was ∼ 203 and ∼ 1.5–3.5 times higher than that of nZVI/BC and other S-nZVI/BCs at same dosed S/Fe molar ratio (0.3), respectively, which was well correlated with the [S/Fe]particle molar ratio. Besides, increased electron efficiency with pH rise was because the passivation of surface FexOy layer (hydrogen evolution reaction sites) enabled electrons more selectively transported to FeSx surface (debromination sites). S2−-nZVI/BC remained more reactive after aging in water over 30 d than nZVI/BC and other S-nZVI/BCs. This work suggested that S precursors had crucial effects on the property and performance of S-nZVI/BC, which can be designed for specific application scenarios.

One-step self-assembly of Fe-biochar composite for enhanced persulfate activation to phenol degradation: Different active sites-induced radical/non-radical mechanism

Persulfate (PS) activation by nanoscale zerovalent iron (nZVI) is promising for water purification, while is limited due to its easy agglomeration and oxidation. Herein, nZVI encapsuled in carbon matrix shell was synthesized via one-step carbothermal reduction. The core-shell structure effectively inhibited oxidation and agglomeration of nZVI core, and graphitized porous structures facilitated phenol binding with maximal adsorption capacity of 117.10 mg/g achieved by nZVI0.6-BC800. Both reactive oxygen species (SO4•−, O•H, O2•− and 1O2) and electron transfer process resulted in phenol decomposition. Owing to diversified active sites, the nZVI0.6-BC800/PS system could completely degrade phenol degradation within short time, and exhibited great adaptation to extensive pH range (3.0–9.0) and coexisting substances. Additionally, the nZVI0.6-BC800/PS system could maintain over 85% removal of phenol after three recycles or 50 days of storage, and was highly-efficient to different water environments, thus proposing rational design of iron-carbon catalyst with potential in water treatment.

Utilization of red clay brick waste in the green preparation of an efficient porous nanocomposite for phenol adsorption: Characterization, experiments and statistical physics treatment

Red clay brick waste was utilized, for the first time, in the green preparation of nanoscale zero-valent iron (nZVI) to impregnate with activated charcoal (ACh). The as-synthesized nZVI@ACh composite was characterized via X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectrometry, thermogravimetric analysis (TG) and its derivative thermogravimetry (DTG), field-emission scanning electron microscopy (FESEM), and transmission electron microscopy (TEM). This novel material was employed for phenol remediation at 25, 35, and 45 °C and pH 7. The results indicated that the prepared ZVI nanoparticles could be either trapped or distributed on the ACh structure. Experimental studies and their modeling with statistical physics theory were applied to analyze the phenol adsorption performance and mechanism using the nZVI@ACh. The phenol adsorption data fitted well to the Langmuir model, with maximum adsorption capacities of 122.85, 137.46, and 152.22 mg/g at 25°, 35°, and 45 °C, respectively. Theoretical calculations via statistical physics indicated that phenol molecules were removed on the nZVI@ACh following the hypothesis of the advanced monolayer model. The number of molecules adsorbed per site (n) ranged from 1.13 to 1.26 suggesting the involvement of vertical geometry and multi-molecular mechanism at all temperatures. The increment of the receptor sites density (NM) from 83.47 to 121.40 mg/g and the adsorption capacity at saturation (Qsat) from 104.75 to 137.19 mg/g with increasing temperature suggested the endothermic behavior of this removal process. Energetically, the phenol adsorption was directed by physical forces with adsorption energies (ΔE) ranging from 13.85 to 16.45 kJ/mol. Macroscopically, phenol adsorption onto nZVI@ACh was spontaneous according to the calculated thermodynamic functions. The developed nZVI@ACh adsorbent can be easily regenerated and reused preserving its competitive adsorption performance. Overall, these results offer a new approach that takes the Fe-rich solid wastes to the next standard in the design of outstanding and low-cost adsorbents for wastewater remediation. Also, the experimental study supported by the theoretical analysis generated new insights of the adsorption system at the micro- and macroscopic scales.

Simultaneous stabilization of Pb, Cd, and As in soil by rhamnolipid coated sulfidated nano zero-valent iron: Effects and mechanisms.

Sulfidation effectively improves the electron transfer efficiency of nanoscale zero-valent iron (nZVI), but decreases the specific surface area of nZVI. In this study, sulfidated nZVI (S-nZVI) coated with rhamnolipid (RL-S-nZVI) was synthesized and used to stabilize Pb, Cd, and As in combined polluted soil. The stabilization efficiency of 0.3% (wt) RL-S-nZVI to water soluble Pb, Cd, and As in soil reached 88.76%, 72%, and 63%, respectively. Rhamnolipid coating inhibited the reduction of specific surface area and successfully encapsulated nZVI, thus reducing the oxidation of Fe0. The types of iron oxides in RL-S-nZVI were reduced compared to S-nZVI, but the content and strength of Fe0 iron were obviously enhanced. Furthermore, rhamnolipid functional groups (-COOH and -COO-) were also involved in the stabilization process. In addition, the stabilization efficiency of RL-S-nZVI to the bioavailable Pb, Cd, and As in soil increased by 41%, 41%, and 50%, respectively, compared with nZVI. The presence of organic acids, especially citric acid, improved the stabilization efficiency of RL-S-nZVI to the three metals. The result of BCR sequential extraction indicated that RL-S-nZVI increased the residual state of Pb, Cd, and As and reduced the acid-soluble and reducible state after 28 days of soil incubation. XRD and XPS analyses showed that the stabilization mechanisms of RL-S-nZVI on heavy metals involved in ion exchange, surface complexation, adsorption, co-precipitation, chemisorption, and redox.

Attenuation of tetracyclines and related resistance genes in soil when exposed to nanoscale zero-valent iron

Antibiotics pollution in soil poses increasing threats to human health due to stimulated proliferation and transmission of antibiotic resistance genes (ARGs). Nanoscale zero-valent iron (NZVI) is a promising material for the remediation of antibiotics, but how NZVI affects the diversity, abundance, and horizontal gene transfer potentials of ARGs remains unclear. Herein, the biotic and abiotic effects of NZVI at different concentrations on tetracyclines (TCs) and the associated ARGs were investigated. Results showed NZVI could effectively accelerate the degradation of TCs, which increased from 51.38% (without NZVI) to 57.96%− 71.66% (1–10 g NZVI/kg) in 20 days. Biotic degradation contributed to 66.10%− 76.30% of the total TCs removal. NZVI induced TCs biodegradation was probably due to alleviated toxicity of TCs on cells and increased microbial biomass and enzyme activities. Additionally, TCs-related ARGs were attenuated with decreased horizontal gene transfer potentials of intI1 and ISCR1, but opposite effects were observed for non TC-related ARGs, especially during excess exposure to NZVI. This study illustrated the possibility of remediating of antibiotic contaminated soil by NZVI and meanwhile reducing the potential risks of ARGs.

Supporting nanoscale zero-valent iron onto shrimp shell-derived N-doped biochar to boost its reactivity and electron utilization for selenite sequestration

Nanoscale zero-valent iron (nZVI) has been widely used in the reductive removal of contaminants from water, yet it still fights against the inherent passive cover and the raise of medium pH. In this study, nZVI was supported onto a nitrogen-doped biochar (NBC) that was prepared by pyrolyzing shrimp shell for efficiently sequestrating aqueous selenite (Se(IV)). The resultant composite (NBC-nZVI) revealed a higher reactivity and electron utilization efficiency (EUE) than the bare nZVI in Se(IV) sequestration because of the positive charge, the buffering effect and the good conductivity of NBC. The kinetic rate and EUE of NBC-nZVI were increased by 143.4% and 15.3% compared to the bare nZVI, respectively, at initial pH of 3.0. The high removal capacity of 605.4 mg g−1 for NBC-nZVI was obtained at Se(IV) concentration of 1000 mg L−1, initial pH of 3.0, NBC-nZVI dosage of 1.0 g L−1 and contact time of 12 h. Moreover, NBC-nZVI exhibited a strong tolerance to solution pHs and coexisting compounds (e.g., humic acid) and could reduce the Se(IV) concentration from 5.0 mg L−1 to below the limit of drinking water (50 μg L−1) in real-world samples. This work exemplified a utilization of shrimp shell-derived NBC to simultaneously enhance the reactivity and EUE of nZVI for reductively removing contaminants.

Efficient and comparative adsorption of trinitrotoluene on MOF MIL-100(Fe)-derived porous carbon/Fe composite adsorbents with rod-like morphology: Behavior, mechanism, and new perspectives

Porous carbon (PC) materials containing nanoscale zero-valent iron (nZVI) often exhibit higher removal efficiency for water pollutants due to the strong influence of nZVI reactivity. However, despite the advantages of nZVI, its presence can sometimes affect the adsorptive properties of the PC materials by blocking the pores and masking adsorption sites, thereby inhibiting efficient adsorption. Herein, we synthesized and used an iron-containing rod-like metal-organic framework, MIL-100(Fe), as a precursor to prepare PC rods with and without surface nZVI, namely, Fe-PCR and PCR, respectively. The prepared materials were characterized, and their adsorption properties for 2,4,6-trinitrotoluene (TNT) – an explosive contaminant – were studied. TNT adsorption onto Fe-PCR and PCR occurred rapidly within 10 min and reached equilibrium after 60 min. Moreover, the results from the kinetics studies showed that TNT adsorption process well-fitted the pseudo-second order (PSO) model due to the higher correlation value (R2 > 0.99), indicating a chemosorption process. The results from the adsorption isotherm and thermodynamic investigations revealed that TNT adsorption onto the prepared adsorbents occurred via a single-to-multilayer adsorption process in which exothermic chemisorption adsorption was dominant. The adsorption capacity of PCR reached 409.38 mg/g, which was significantly higher than Fe-PCR (249.97 mg/g) under ambient conditions. This revealed that the presence of surface-abundant nZVI in Fe-PCR limited the adsorption of TNT compared to PCR. Moreover, analysis of the TNT-loaded adsorbents revealed that TNT was not altered by nZVI but adsorbed onto the PC-rods surfaces via π-π EDA interactions, hydrogen bonding, and physical adsorption via pore filling. Thus, the improved structural properties of PCR due to Fe removal (SBET: 720 m2/g; Vpore: 1.76 cm3/g) compared to Fe-PCR (SBET: 408.72 m2/g; Vpore: 0.762 cm3/g) provided greater accessibility to adsorption sites, thereby resulting in better adsorption performance.

Combining nanoscale zero-valent iron and anaerobic dechlorinating bacteria to degrade chlorinated methanes and 1,2-dichloroethane

Nanoscale zero-valent iron (nZVI) has the potential to degrade a diversity of chlorinated compounds, and it is widely used for remediation of contaminated groundwaters. However, some frequently detected contaminants such as dichloromethane (DCM) and 1,2-dichloroethane (1,2-DCA) have shown nearly no reactivity with nZVI. Here, we tested the feasibility of combining anaerobic dechlorinating bacteria, Dehalobacterium and Dehalogenimonas, and nZVI as a treatment train to detoxify chlorinated methanes (i.e., chloroform-CF- and DCM), and 1,2-DCA. First, we showed that CF (500 μM) was fully degraded by 1 g/L nZVI to DCM as a major by-product, which was susceptible to fermentation by Dehalobacterium to innocuous products. Our results indicate that soluble compounds released by nZVI might cause an inhibitory impact on Dehalobacterium activity, avoiding DCM depletion. The DCM dechlorination activity was recovered when transferred to a fresh medium without nZVI. The increase in H2 production and pH was discarded as potential inhibitors. Similarly, a Dehalogenimonas-containing culture was unable to dichloroeliminate 1,2-DCA when exposed to 1 g/L nZVI, but dechlorinating activity was also recovered when transferred to nZVI-free media. The recovery of the dechlorinating activity of Dehalobacterium and Dehalogenimonas suggests that combination of nZVI and bioremediation techniques can be feasible under field conditions where dilution processes can alleviate the impact of the potential inhibitory soluble compounds.

Nanoscale zero-valent iron mitigates arsenic mobilization and accumulation in Sinapis alba grown on a metal(loid)-polluted soil treated with a dunite mining waste-compost amendment

Background and aimThe use of amendments to immobilize metals in polluted soils is a widely accepted remediation approach, and in the framework of the circular economy, amendments produced from mining and/or biomass waste have gained relevance. However, the application of such amendments can also mobilize metalloids. Here we propose the combination of nanoscale zero-valent iron nanoparticles (nZVI) with dunite (mining waste) and compost for the remediation and restoration of soil affected by high concentrations of As and metals.MethodsTo this end, we treated pots containing the polluted soil with combinations of dunite, compost, and nZVI for 75 days. In addition, Sinapis alba was used to evaluate the effects of the amendments on pollutant accumulation in the plant. The mobility of the pollutants was monitored through TCLP extraction and by sampling pore water. Furthermore, pH, available P, and cation exchange capacity (CEC) were also determined.ResultsDunite application led to the immobilization of metals, and supplied Mg, thus improving CEC. On the other hand, compost increased nutrient content, and also promoted plant growth. However, this amendment caused a dramatic increase in As accumulation in the plants. Finally, the application of nZVI in combination with the other two amendments was found to be the most appropriate strategy since it not only prevented As mobilization and accumulation but also added nutrients to the soil, thus promoting plant growth.ConclusionThe combination of nZVI with dunite mining waste and compost proved effective for the remediation of soil simultaneously polluted by As and metals.

Immobilization of uranium by S-NZVI and UiO-66-NO2 composite through combined adsorption and reduction

Radioactive uranium removal plays a key role in energy development and environmental security. Sulfide nanoscale zero-valent iron (S-NZVI) has good antioxidant capacity, dispersibility and activity to eliminate U(VI) from wastewater, but the removal efficiency is limited. To improve the reduction and adsorption capacity of S-NZVI, through treating Fe3+ solution by nitro-functionalized UiO-66 (UiO-66-NO2) with high porosity, UiO-66-NO2 enhanced S-NZVI adsorbent (S-NZVI/UiO-66) was prepared by liquid phase reduction method. The smaller size and larger specific surface area of S-NZVI/UiO-66 were confirmed by a variety of characterization techniques. Based on the excellent surface structure and reactivity, the U(VI) removal capacity of S-NZVI/UiO-66 (895 mg g−1) was much better than S-NZVI (434 mg g−1) and UiO-66-NO2 (267 mg g−1). The impacts of pH, background ion strength, coexisting ions and different water environments on adsorption were studied via macroscopic batch experiments. The results showed that S-NZVI/UiO-66 could remove U(VI) adequately in a wide pH range. The removal rate was basically not affected by the concentration of NaNO3, demonstrating that the adsorption process of U(VI) on S-NZVI/UiO-66 tended to inner surface complexation. From XPS technique combined with the results of batch adsorption experiments, it was clear that the elimination mechanisms of U(VI) by S-NZVI/UiO-66 were mainly the physical adsorption, electrostatic attraction and complexation of UiO-66-NO2, and the reduction and complexation of S-NZVI. Therefore, it is believed that S-NZVI/UiO-66 has a great potential to be an excellent adsorbent in the field of the environment remediation. Moreover, S-NZVI/UiO-66 promises to be a novel nanomaterial for solving the problem of radionuclide contamination in practical environments.

Attenuation of Pb and Sb in shooting range soils by Fe amendments

Lead (Pb) and antimony (Sb) contamination pose a major environmental risk at firing ranges and threaten land sustainability. Methods for the stabilization of metal (loid) contaminants are necessary to prevent off-site migration of metals in surface and ground water or from soil erosion. In the present study, two remediation treatments (ferric chloride/calcium carbonate and nanoscale zero-valent iron (nZVI)) were applied to flow-through soil columns containing four types of soils (sand, sandy loam, loamy sand, and silty loam) to study Pb and Sb behavior. Water runoff was continuously monitored for three months prior to amendment addition and for the following ten months. Soils were characterized before and after reaction. We found Sb was more mobile than Pb in all soil systems and was primarily present in the dissolved fraction whereas Pb was associated with both soil organic matter (SOM) and Fe colloids. Dominant Pb solid phase species were comprised of Pb0, PbO, PbCO3, and Pb sorbed to Fe(III) oxides while Sb was present as fully oxidized Sb(V) in soil and soil solution. The nZVI addition had minimal impact on Pb and Sb immobilization compared to control soil. The FeCl2 and CaCO3 amendment decreased pore water Sb concentrations by >80% for all soil types and >96% reduction in the fine- and coarse-grained soil types (silt loam and sand). Lead was initially mobilized coinciding with a decrease in pH from the hydrolysis of Fe(II) in solution. Additional soil treatments have the potential to be effective for system-wide immobilization with adequate additions of CaCO3 buffer. Though this study focused on bullet fragment weathering as a source of Pb and Sb the results have application to environmental monitoring and remediation efforts at mining or industrial runoff sites.

Formation and mechanism of nanoscale zerovalent iron supported by phosphoric acid modified biochar for highly efficient removal of Cr(VI)

The effect of phosphoric acid modified biochar on activity of nanoscale zero valent iron particles is not clear until now. In this research, Egeria najas powder driven biochar-supported nanoscale zero valent iron was modified by phosphoric acid (P-BC/nZVI) for highly effective removal of Cr(VI) from wastewater. The TEM and XRD of P-BC/nZVI indicated that nZVI particles were successfully immobilized on the P-BC surface. The batch experiment results show that the Cr(VI) removal efficiency by P-BC/nZVI was higher than that of BC/nZVI, nZVI, P-BC and BC. Moreover, the optimal ratio of nZVI to P-BC lies at 3:1 with fixed P-BC/nZVI dosage of 0.75 g/L, initial Cr(VI) concentration of 20 mg/L, solution pH of 2, and reaction temperature of 333 K. Additionally, Cr(VI) removal capacities by nZVI, BC/nZVI and P-BC/nZVI aged for 15 days in water were 12.9 %, 28.55 % and 99.35 %, respectively. Furthermore, corresponding reaction kinetics fitted well with pseudo-second order model, and adsorption isotherm fitted to Sips isothermal model. The SEM-EDS and XPS confirm that Cr(VI) was participated in the reaction, and about 63.43 % of Cr(VI) was reduced to Cr(III), and the rest was adsorbed on the surface of P-BC/nZVI. The removal mechanism of Cr(VI) by P-BC/nZVI was complex, including adsorption, reduction and surface complex formation.

Efficient degradation of cefadroxil by peroxymonosulfate activation with nanoscale zero-valent iron supported on MnFe2O4

A magnetic Fe0/MnFe2O4 nanocomposite was prepared, characterized and used to activate peroxymonosulfate (PMS) for the degradation of cefadroxil (CDX) in water. The results suggested that a synergistic effect existed between Fe0 and MnFe2O4, since Fe0/MnFe2O4 presented higher catalytic activity than that of the pure Fe0 and MnFe2O4. A 93.4 % CDX removal and 58.2 % TOC removal was reached in the Fe0/MnFe2O4/PMS system at 120 min. Based on radical quenching and electron paramagnetic resonance (EPR) tests, the generation of SO4•−, •OH, O2•− and 1O2 was proved and the mechanism of PMS activation by Fe0/MnFe2O4 was proposed. Overall, this work indicated that Fe0/MnFe2O4/PMS system showed a good potential for the elimination of antibiotics in the aquatic environment.

The remediation of hexavalent chromium-contaminated soil by nanoscale zero-valent iron supported on sludge-based biochar

The remediation of hexavalent chromium-contaminated soil by nanoscale zero-valent iron supported on sludge-based biochar

Regulating the reaction pathway of nZVI to improve the decontamination performance through magnetic spatial confinement effect

Nanoscale zero-valent iron (nZVI) shows high effectiveness in the catalyzed removal of contaminants in wastewater treatment. However, the uncontrolled interfacial electron transfer behavior and formation of surface iron oxide (FeOx) layer led to severe electron wasting and occasionally form highly toxic intermediates. Here, we constructed magnetic mesoporous SiO2 shell on surface of nZVI to stimulate a magnetic spatial confinement effect and regulate the electron transfer pattern. Therein, Fe atom facilely spread out from the nZVI core, orderly release electron to surface adsorbed H2O molecule, which is efficiently transformed into active hydrogen (H*). Meanwhile, in-situ Raman revealed that Fe atoms were involved in the formation of penetrable γ-FeOOH rather than FeOx layer, enabling the continuous inward diffusion of H2O and outward diffusion of H* . Employing the catalyzed removal of halogenated phenols as demo reaction, the presence of magnetic mesoporous SiO2 shell utilized the reaction between electrons and H2O to switch the reaction pathway from the reduction/oxidation hybrid process to hydrodehalogantion, and increased the conversion of halogenated phenols-to-phenols by 5.53 times. This study shows the forehand of improving the decontamination performance of nZVI through sophisticated designed surface coating, as well as fine regulating the environmental behavior of magnetic material via micro-magnetic field.

NZVI-Based Nanomaterials Used for Phosphate Removal from Aquatic Systems.

In the last decade, the application of nanoscale zero-valent iron (nZVI) has garnered great attention as an adsorbent due to its low cost, non-toxicity, high porosity, and BET-specific surface area. In particular, the immobilization of nZVI particles onto inorganic and organic substrates (nanocomposites) decreased its agglomeration, allowing them to be effective and achieve greater adsorption of pollutants than pristine nanoparticles (NPs). Although nZVI began to be used around 2004 to remove pollutants, there are no comprehensive review studies about phosphate removal from aquatic systems to date. For this reason, this study will show different types of nZVI, pristine nZVI, and its nanocomposites, that exist on the market, how factors such as pH solution, oxygen, temperature, doses of adsorbent, initial phosphate concentration, and interferents affect phosphate adsorption capacity, and mechanisms involved in phosphate removal. We determined that nanocomposites did not always have higher phosphate adsorption than pristine nZVI particles. Moreover, phosphate can be removed by nZVI-based nanoadsorbents through electrostatic attraction, ion exchange, chemisorption, reduction, complexation, hydrogen bonding, and precipitation mechanisms. Using the partition coefficient (PC) values, we found that sepiolite-nZVI is the most effective nanoadsorbent that exists to remove phosphate from aqueous systems. We suggest future studies need to quantify the PC values for nZVI-based nanoadsorbents as well as ought to investigate their phosphate removal efficiency under natural environmental conditions.

Green Synthesis of Nanoscale Zero-Valent Iron Aggregates for Catalytic Degradation of Textile Dyes

Green Synthesis of Nanoscale Zero-Valent Iron Aggregates for Catalytic Degradation of Textile Dyes

Degradation behaviors and accumulative effects of coexisting chlorobenzene congeners on the dechlorination of hexachlorobenzene in soil by nanoscale zero-valent iron.

It is well known that many chlorinated organic pollutants can be dechlorinated by nanoscale zero-valent iron. However, in the real chlorinated organic compounds contaminated soil, the congeners of high- and low-chlorinated isomer often coexist and their dechlorination behaviors are poorly known, such as hexachlorobenzene (HCB). In this work, the degradation behaviors of three coexisting chlorobenzene congeners pentachlorobenzene (PeCB), 1,2,4,5-tetrachlorobenzene (1,2,4,5-TeCB) and 1,2,4-trichlorobenzene (1,2,4-TCB) and the influence of initial pH and reaction temperature on the dechlorination of HCB in HCB-contaminated soil by nanoscale zero-valent iron were studied. The amount and extent of accumulated coexisting chlorobenzenes was analyzed under different environmental conditions. The results indicate that nanoscale zero-valent iron can improve the degradation efficiency of highly toxic chlorinated benzenes and reduce the accumulative effects of highly toxic chlorinated benzenes on dechlorination of HCB. The accumulative effects of three coexisting chlorobenzene congeners on the dechlorination of HCB were ranked as follows: 1,2,4-TCB > 1,2,4,5-TeCB > PeCB.