Stabilized Nano Zero-valent Iron Research Articles

Portable SA/CMC entrapped bimetallic magnetic fly ash zeolite spheres for heavy metals contaminated industrial effluents treatment via batch and column studies

Heavy metals are perceived as a significant environmental concern because of their toxic effect, bioaccumulation, and persistence. In this work, a novel sodium alginate (SA) and carboxymethylcellulose (CMC) entrapped with fly ash derived zeolite stabilized nano zero-valent iron and nickel (ZFN) (SA/CMC-ZFN), followed by crosslinking with CaCl2, is synthesized and applied for remediation of Cu(II) and Cr(VI) from industrial effluent. The characterization of the adsorbent and its surface mechanism for removing metals were investigated using advanced instrumental techniques, including XRD, FT-IR, SEM–EDX, BET, and XPS. The outcomes from the batch experiments indicated that monolayer adsorption on homogeneous surfaces (Langmuir isotherm model) was the rate-limiting step in both heavy metals sorption processes. The maximum adsorption capacity of as-prepared SA/CMC-ZFN was 63.29 and 10.15 mg/g for Cu(II) and Cr(VI), respectively. Owing to the fact that the wastewater released from industries are large and continuous, a continuous column is installed for simultaneous removal of heavy metal ions from real industrial wastewater. The outcomes revealed the potential of SA/CMC-ZFN as an efficient adsorbent. The experimental breakthrough curves fitted well with the theoretical values of Thomas and Yoon-Nelson models. Overall, the results indicated that SA/CMC-ZFN is a viable, efficient, and cost-effective water treatment both interms of batch and column processes.

Biochar stabilized nano zero-valent iron and its removal performance and mechanism of pentavalent vanadium(V(V))

In recent years, with the rapid development of economy and industry, the increasing pollution of pentavalent vanadium (V(V)) in water has led to potential dangers to human health, which cannot be ignored. In this study, nano zero-valent iron (nZVI) was successfully stabilized by biochar (BC) to remediate vanadium(V(V)) contaminated wastewater. The removal process of V(V) from water by the synthesized nZVI/BC under different conditions was systematically discussed. The results showed that the removal efficiency of V(V) increased with the increase of nZVI/BC dosage, which was related to the corresponding increase of reaction sites. Moreover, the removal capacity (48.5 mg/g) was independent on the pH of solution in the range of 2.0∼10.0 and the adsorption kinetic fitted well with the pseudo-second-order model (R2 = 0.9998). When the initial V(V) concentration was below 25 mg/L, the removal efficiency of V(V) was higher than 99%. The removal mechanism of V(V) by the nZVI/BC composite was analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectrometer (EDS), and X-ray photoelectron spectroscopy (XPS). The results showed that the interaction between nZVI/BC and V(V) was primarily controlled by electrostatic attraction, redox and precipitation processes. In a word, the nZVI/BC composite can be used as an effective alternative for V(V) removal from wastewater.

Polyethylene glycol-stabilized nano zero-valent iron supported by biochar for highly efficient removal of Cr(VI)

In this study, polyethylene glycol (PEG)-stabilized nano zero-valent iron (nZVI) supported by biochar (BC) (PEG-nZVI@BC) was prepared to remedy Cr(VI) with high efficiency. The morphology, functional groups, and crystalline structure of PEG-nZVI@BC composites were characterized, revealing that when PEG was added, a large number of –OH functional groups were introduced, and nZVI was effectively dispersed on the BC surface with a smaller particle size. The results of Cr(VI) remediation experiments showed Cr(VI) removal rate by PEG-nZVI@BC (97.38%) was much greater than that by BC-loaded nZVI (nZVI@BC) (51.73%). The pseudo second-order and Sips isotherm models provide the best simulation for Cr(VI) removal experimental data, respectively. The main remediation mechanism of Cr(VI) was reduction and co-precipitation of Cr-containing metal deposits onto PEG-nZVI@BC. Ecotoxicity assessment revealed PEG-nZVI@BC (1.00 g/L) has little influence on rice germination and growth, but resisted the toxicity of Cr(VI) to rice. The modified Community Bureau of Reference (BCR) sequential extraction showed pyrolysis could increase the percentage of oxidizable and residual Cr and diminish the environmental risk of Cr release from post-removal composites.

Carboxymethyl nanocellulose stabilized nano zero-valent iron: an effective method for reduction of hexavalent chromium in wastewater

The present work describes a novel material, carboxymethyl nanocellulose (CMNc) and its use for stabilization of nano zero-valent iron (nZVI) composites. The CMNc stabilized nano zero-valent iron composite was further utilized for effective reduction of hexavalent chromium [Cr(VI)] in aqueous media. The FTIR studies showed peaks corresponding to the nanocellulose and carboxymethylation of nanocellulose (CMNc). The x-ray diffraction pattern of CMNc-stabilized nZVI composites was confirmed the presence of nZVI nanoparticles. The morphology of nanocomposites was observed by scanning electron microscope (SEM) and transmission electron microscope (TEM). The thermograms of thermogravimetric analysis showed that thermal stability of the CMNc-stabilized nZVI composites was much improved as compared to bare nZVI. The maximum adsorption capacity of CMNc-stabilized nZVI composites for Cr(VI) was 87.71 mg g−1 as determined by Langmuir and Freundlick adsorption isotherms. At a constant dose of 0.015 g, CMC-stabilized nZVI nanoparticles were able to reduce almost 100% of 15 mg l−1 of Cr(VI) in 90 min. Therefore, the CMNc-stabilized nZVI composites material showed a promising potential for the adsorption of Cr(VI) in wastewater and can impel advancements in CMNc-based nanomaterials for their application in environmental remediation of heavy metals.

Application of Stabilized Nano Zero Valent Iron Particles for Immobilization of Available Cd2+, Cu2+, Ni2+, and Pb2+ Ions in Soil

The present manuscript studies the effectiveness of commercial nano zero valent iron (nZVI) particles in decreasing the availability of Cd, Cu, Ni, and Pb in spiked soil samples and to remove the same heavy metals from aqueous solutions. The difference of nZVI efficiency between single and multi-metal contamination was evaluated. The application of nZVI in water samples showed higher effectiveness in the cases of single metal contamination. The effectiveness of single- and multi-metal (mixtures of Cu, Ni, Pb and Cd, Cu, Ni, Pb) immobilization in soil using different doses (0%, 0.85%, 1.7%, 2.55%, and 5.1%) of nZVI was determined. Immobilization efficiency was assessed using the leaching procedure and depended on a particular metal and the dose of nZVI. In all cases, it was determined that an increasing amount of nZVI resulted in decrease in the leaching of analysed metals. In cases, where higher nZVI doses were used, higher immobilization efficiency was observed for heavy metals in multi-metal contamination. The application of nZVI significantly reduced leaching of all heavy metals and this strategy can be successfully used for heavy metals stabilization in soils.

Greywater Treatment Using Single and Combined Adsorbents for Landscape Irrigation

Greywater reuse can be considered as an additional supply of water not only to protect water resources but also to reduce water shortage. Thus, the aim of this research is to examine the feasibility of three adsorbents (activated carbon (AC), Iranian natural zeolite (Z) and stabilized nano zero-valent iron (nZVI)) in single and combined forms to treat greywater for reuse in landscape irrigation. For this purpose, greywater samples were collected from student hostel of Fasa University and analyzed in a batch mode experiment. Also, the adsorption of COD was studied in terms of kinetic, isotherm and thermodynamic models. The results indicated that among the seven treatments, the combination of AC, Z and nZVI had the best performance in greywater treatment. 85.75% removal of COD, 91.81% of TDS and 98.1% of turbidity were achieved by triple combined treatment. In double combined adsorbents, the highest adsorption rate of COD, TDS and turbidity was accomplished when AC+nZVI, AC+Z and nZVI+Z were used, respectively. The results also indicate that single adsorbents alone are not adequate to guarantee a sufficient reduction of COD, TDS and turbidity. Kinetics of COD removal by all treatments obeyed to pseudo-second-order model and the Freundlich isotherm closely fitted the experimental data. The COD data demonstrated that the sorption process is spontaneous and endothermic. The results indicated that the triple combined adsorbents were able to reduce the COD, TDS, turbidity and pH level to the required reuse in landscape irrigation and the results were satisfactory according to Iranian standards.

A novel biochar supported CMC stabilized nano zero-valent iron composite for hexavalent chromium removal from water

In this study, novel biochar supported nano-scale zero-valent iron (biochar-CMC-nZVI) stabilized by carboxymethyl cellulose (CMC) was developed and used for the removal of hexavalent chromium (Cr(VI) from aqueous solution. With the stabilization of CMC, nZVI particles (about 80 nm) were effectively dispersed onto the surface of biochar, which inhibited the aggregation of nZVI and resulted in the smaller particle size of nZVI on the surface of biochar. The results showed that the specific surface area of the composite was 11.1 m2/g, lower than that of pristine biochar. The basic element composition was C, O, and Fe with a large number of oxygen-containing functional groups (−COOH, OH, and OCO) observed on the surface. Cr(VI) was reduced to Cr(III) by the composite material, mainly due to the reduction of nZVI on the biochar surface. Upon reaction with Cr(VI), CrxFe1-x(OH)3 and FexCryO4 were deposited on the surface of biochar-CMC-nZVI composite. Electrostatic attraction, reduction, and surface complexation were the dominant removal mechanisms. The results showed that the 100 mg/L Cr(VI) could be removed completely by biochar-CMC-nZVI within 18 h, at a dosage of 1.25 g/L and an initial pH of 5.6. Cr(VI) removal by biochar-CMC-nZVI was favored by lower pH. The pseudo-second-order kinetic model and the Langmuir isothermal adsorption model fitted well with the sorption kinetic and isotherm data, indicated Cr(VI) adsorption mechanism was a chemisorption based multi-layer adsorption. The present study demonstrated the promise of biochar-CMC-nZVI composite as a low-cost, “green”, and effective sorbent for removal of Cr(VI) in the environment.

Field Scale Mobility and Transport Manipulation of Carbon-Supported Nanoscale Zerovalent Iron in Fractured Media.

In field applications, mostly in porous media, transport of stabilized nano zerovalent iron particles (nZVI) has never exceeded a few meters in range. In the present study, the transport of Carbo-Iron Colloids (CIC), a composite material of activated carbon as a carrier for nZVI stabilized by carboxymethyl cellulose (CMC), was tested under field conditions. The field site lies within a fractured chalk aquitard characterized by moderately saline (∼13 mS) groundwater. A forced gradient tracer test was conducted where one borehole was pumped at a rate of 8 L/min and CMC-stabilized CIC was introduced at an injection borehole 47 m up-gradient. Two CIC-CMC field applications were conducted: one used high 100% wt CMC (40 g/L) and a second used lower 9% wt loading (∼2.7 g/L). Iodide was injected as a conservative tracer with the CIC-CMC in both cases. The ratio between the CIC-CMC and iodide recovery was 76% and 45% in the high and low CMC loading experiments, respectively. During the low CMC loading experiment, the pumping rate was increased, leading to an additional CIC recovery of 2.5%. The results demonstrate the potentially high mobility of nZVI in fractured environments and the possibility for transport manipulation through the adjustment of stabilizer concentration and transport velocity.

Removal of 2,4-dichlorophenol in Underground Water by Stabilized Nano Zero-valent Iron

To restrain the nano zero-valent iron (NZVI) in aqueous solution from being reunited and oxidized, this paper used sodium carboxymethyl starch (CMS), which is an environmentally friendly and cheap material, for coating and surface modification of NZVI so as to improve its dispersity and suspension property. Transmission Electron Microscope (TEM) and X-ray diffraction (XRD) were used to study the microstructure and components of the modified NZVI, and the 2,4-dichlorophenol 2,4-(DCP) removal efficiency was researched through chemical experiment. Experiments showed that the modified NZVI was about 80~100 nm in diameter, present as chain or dispersed particles. The main component was zero-valent iron, and it had strong reducibility. When the proportion of CMS was 80.00%, the suspension property was the best; The NZVI after CMS coating and surface modification retained the original activity. In the experiment investigating the removal effect of 2,4-DCP using different proportion of cladding, the same finding was obtained. When the CMS's proportion was 80%, the removal effect was the best, reaching up to 83.69%, and the dechlorination and degradation were apparent.

Removal of Nitrate from Aqueous Solutions by Starch Stabilized nano Zero-Valent Iron(nZVI)

Removal of Nitrate from Aqueous Solutions by Starch Stabilized nano Zero-Valent Iron(nZVI)

Ultrasonic-assisted synthesis of reactive carboxymethyl cellulose stabilized nano zero-valent iron and its application for removal of Cr6+ and Cu2+ ions

Ultrasonic-assisted synthesis of reactive carboxymethyl cellulose stabilized nano zero-valent iron and its application for removal of Cr6+ and Cu2+ ions

Ultrasonic-assisted synthesis of reactive carboxymethyl cellulose stabilized nano zero-valent iron and its application for removal of Cr6+ and Cu2+ ions

Ultrasonic-assisted synthesis of reactive carboxymethyl cellulose stabilized nano zero-valent iron and its application for removal of Cr6+ and Cu2+ ions

Synthesis of MCM-41 stabilized NZVI and its use in removal of Cr(VI) from aqueous solution

In this study, MCM-41 stabilized nano zero-valent iron (M-NZVI) is synthesized using the rheological phase reaction method. Characterization with transmission electron microscopy validates the hypothesis that the introduction of MCM-41 leads to a decrease in aggregation of iron nanoparticles. X-ray diffraction confirms the existence of Fe0 and the strong antioxidant activity of Fe0 nanoparticles. Batch Cr(VI) reduction experiments exhibit that solution pH, M-NZVI dosage, and reaction time have significant effects on Cr(VI) removal. A high removal efficiency of Cr(VI) (84.5%) is obtained within 60 min for 100 mg/L of Cr(VI) solution at an initial pH of 6.0 and M-NZVI dosage of 0.5 g/L at 35 °C. The Cr(VI) removal rates follow modified pseudo-first-order kinetic equations. The observed removal rate constant was 0.0168/min for the M-NZVI dosage of 1.0 g/L. Our study suggests that the introduction of an innocuous stabilizer such as MCM-41 can significantly improve the performance of Fe0 nanoparticles for environmental remediation applications.

Removal of Hexavalent Chromium from Aqueous Solutions by Sodium Dodecyl Sulfate Stabilized Nano Zero-Valent Iron: A Kinetics, Equilibrium, Thermodynamics Study

Sodium dodecyl sulfate stable nanoscale zero-valent iron (SDS-nZVI) was synthesized by the sodium borohydride reduction method, characterized with SEM and XRD. SDS-nZVI was used for the removal of Cr (VI) from aqueous solutions at different conditions in a batch process. XRD analysis indicated the presence of iron oxide and iron-chromium hydroxide coprecipitation on the surface of SDS-nZVI after reaction some time. The reaction kinetics, mechanism, isotherms, and thermodynamics for Cr (VI) removal of aqueous solution via SDS-nZVI were investigated. The pseudo-second-order model was relatively suitable for describing the reaction process. Intraparticle diffusion model was used to analysis the mechanism, the results indicated that there were two processes (bulk diffusion and surface diffusion) controlling the reaction rate, while only one was rate limiting in any particular time range. The fitted Temkin and D-R model satisfactorily explanted the experimental data in the range of 303–343 K. The maximum removal capacity of SDS-nZVI for Cr (VI) was obtained for 336.7 mg g−1 at 303 K. The overall removal process was endothermic. These results demonstrated that SDS-nZVI could potentially be used as an effective material for environmental remediation.

Preparation of stabilized nano zero-valent iron particles via a rheological phase reaction method and their use in dye decolourization

In this study, sodium carboxymethyl cellulose (NaCMC)-stabilized nano zero-valent iron (C-nZVI) was synthesized using a rheological phase reaction method. The orthogonal method was used to evaluate the factors influencing C-nZVI properties and this showed that the reaction time, solid–liquid ratio (w/v), grinding time and NaCMC concentration were all important factors. Characterization with scanning electron microscopy validated the hypothesis that the introduction of CMC led to a decrease in aggregation of iron nanoparticles. X-ray diffraction confirmed the existence of Fe0 and the strong antioxidant activity of the iron particles. Batch decolourization experiments exhibited that solution pH, C-nZVI dosage and reaction time have significant effects on dye decolourization. A high decolourization efficiency (94.5%) was obtained within 30 min for 100 mg/L of reactive blue-19 at the optimal pH value of 5 and C-nZVI loading of 6 g/L at room temperature. The decolourization rates followed modified pseudo-first-order kinetic equations with respect to dye concentration. The observed removal rate constant was 0.0447 min−1 for the C-nZVI loading of 6 g/L.

Characteristics of two types of stabilized nano zero-valent iron and transport in porous media

Nano-scale zero-valent iron (NZVI) has been shown to be suitable for remediating contaminated aquifers. However, they usually aggregate rapidly and result in a very limited migration distance that inhibits their usefulness. This study employed poly acrylic acid (PAA) and carboxymethyl cellulose (CMC) to synthesize two types of stabilized styles of NZVI with finer sizes (namely PNZVI and CNZVI). The mobility of stabilized NZVI was also demonstrated on the basis of transport in porous media. The results show that the PNZVI has a uniform particle size of 12 nm. However, tens of CNZVI particles with diameters of 1–3 nm were packed into secondary particles. Both the PNZVI and the CNZVI exhibited amorphous structures, and the stabilizer was bound to particle surfaces in the form of bidentate bridging via the carboxylic group, which could provide both electrostatic and steric repulsion to prevent particle aggregation. This study also proposes presumed stabilized configurations of PNZVI and CNZVI to reasonably illustrate their different dispersed suspension types. On the basis of the breakthrough curves and mass recovery, this study observed that the mobility of PNZVI in classic Ca 2+ concentration of groundwater was superior to CNZVI. Nonetheless, the mobility of CNZVI would be decreased less significantly than PNZVI when encountering high Ca 2+ concentrations (40 mM). Presumably, increasing the pore flow velocity would enhance the mobility of stabilized NZVI. Overall, the results of this study indicate that PNZVI has the potential to become an effective reactive material for in situ groundwater remediation.