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Today, new energy sources alternative to fossil fuels are needed to meet the increasing energy demand. It is becoming increasingly important to constitute new energy sources from waste biomass through the liquefaction process. In this study, walnut shells (WS) were liquefied catalytically and non-catalytically under different parameters using the liquefaction method. In this process, the effect of silica fume/nano zero-valent iron (SF/NZVI) catalysts on the conversion rates was investigated. The catalyst was synthesized by reducing NZVI using a liquid phase chemical reduction method on SF. The SF/NZVI catalyst was characterized by scanning electron microscopy- energy dispersive X-ray (SEM–EDX), transmission electron microscope (TEM), Brunauer–Emmett–Teller (BET), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS) analysis. The effect of various process parameters on the liquefaction process was investigated. In this context, the reaction temperature ranged from 300 to 400 °C, the solid/solvent ratio ranged from 1/1 to 1/3, the reaction time ranged from 30 to 90 min, and the catalyst concentration ranged from 1 to 6%. According to the results obtained, the most suitable operating conditions for non-catalytic experiments in liquefaction of WS were found to be temperature of 400 °C, reaction time of 60 min, and solid/solvent of 1/3. In catalytic conditions, the optimum values were obtained as temperature of 375 °C, reaction time of 60 min, solid/solvent ratio of 1/3, and catalyst concentration of 6%. The highest total conversion and (oil + gas) % conversion were 90.4% and 46.7% under non-catalytic conditions and 90.7% and 62.3% under catalytic conditions, respectively. Gas chromatography/mass spectrometry (GC/MS) analysis revealed the bio-oil was mainly composed of aromatic compounds (benzene, butyl-, indane and their derivatives,) and polyaromatic compounds (naphthalene, decahydro-, cis-, naphthalene, 1-methyl-.). The aim of increasing the quantity and quality of the light liquid product in the study has been achieved. [ABSTRACT FROM AUTHOR]

The aggregation of nanoscale zero-valent iron (NZVI) is one of the biggest challenges for its application when treating contaminants in aquatic environment. We report a study on synthesis of sodium carbonate-modified biochar (BC-600) combined with sodium alginate (SA)-modified NZVI (SA/NZVI@BC-600) for the removal of tetracycline (TC). When the initial concentration of TC was 20 mg/L, 100% TC was removed by SA/NZVI@BC-600 at an initial pH of 7 under room temperature of 25 °C within 90 min. In addition, the reactivity of the SA/NZVI@BC-600 composites toward TC removal was not obviously declined after 4 cycles. SA/NZVI@BC-600 shows high reactivity, stability, and reusability. This excellent performance of SA/NZVI@BC-600 was related to the addition of SA and BC-600. The best performance of the SA/NZVI@BC-600 system was observed under weakly acidic and neutral conditions. Increasing the initial concentration and lowering the reaction temperature had a slight negative effect on the removal of TC by SA/NZVI@BC-600. In addition, the presence of CO32− and HCO3− had a significant negative effect on the degradation of TC. Meanwhile, ·OH and ·O2− played the leading role in TC degradation. This study not only reported a novel strategy of synthesizing an excellent BC modified NZVI based catalyst but also evaluated its promising application for antibiotic degradation in aqueous solution. [ABSTRACT FROM AUTHOR]

The degradation of formaldehyde in a photo-Fenton reaction was studied using n-ZVI/TiO2 as the catalyst. The effects of %n-ZVI loading, catalyst dosage, H2O2, and pH on formaldehyde degradation were studied. The n-ZVI/TiO2 catalysts were prepared by impregnation with chemical reduction, and their catalytic activity was evaluated in a batch reactor under UVC light. Transmission electron microscopy (TEM) was used to determine that the n-ZVI nanoparticle size was 39.41 nm. X-ray photoelectron spectroscopy (XPS) was used to study the oxidation states of 2%n‑ZVI/TiO2, and the Fe 2p spectrum of 2%n-ZVI/TiO2 indicated the presence of Fe0. The optimal conditions for the complete removal of formaldehyde within 30 min were an n-ZVI loading of 2 wt.%, a catalyst dosage of 0.5 g/L, 30 mM H2O2, and an initial pH of 3. After the reaction, the C–H functional group of formaldehyde was not observed due to the •OH radicals generated by Fe0 and H2O2 attacking the formaldehyde molecule. Moreover, no Fe leaching was observed, presenting an advantage compared with homogeneous Fe catalysts. Therefore, 2%n‑ZVI/TiO2 shows excellent potential as a photo-Fenton catalyst for the environmentally friendly degradation of formaldehyde. [ABSTRACT FROM AUTHOR]

A novel composite (nZVI/HNTs) was prepared via incorporating nano zero-valent iron (nZVI) on halloysite nanotubes (HNTs) for degrading tetracycline hydrochloride (TCH) with existence of persulfate (PS). The adsorption process of nZVI/HNTs to TCH conformed to the Freundlich isotherm model and pseudo-second-order kinetic model, and its maximum adsorption capacity was 76.62 mg·g−1. Furthermore, the nZVI/HNTs + PS system exhibited satisfactory degradation efficiency (84.21%) for TCH, and stable nZVI/HNTs (Fe leaching < 0.001 mg·L−1) could be reused. When nZVI/HNTs dosage, PS dosage and temperature increased, TCH degradation could be enhanced. After four cycling, nZVI/HNTs + PS system had still 65.8% degradation for TCH. The quenching tests and EPR analysis evidenced that SO4•− was predominant instead of •OH in such system. Three possible pathways of TCH degradation were provided through the liquid chromatograph-mass spectrometer (LC–MS) determination. Meanwhile, the biological toxicity prediction analysis indicated that the nZVI/HNTs + PS system would be an environment friendly treatment method toward TCH pollution. [ABSTRACT FROM AUTHOR]

In this study, nano zero-valent iron (nZVI) was used as the Fe2+ source in the Fenton reaction, and a UV-nZVI-H2O2 system was constructed to efficiently degrade and mineralize refractory organic matter in landfill leachate. The results showed that under the optimal conditions (initial pH = 3, UV = 14 W, nZVI = 0.5 g/L, and [H2O2] = 30 mM), the removal efficiencies of total organic carbon, absorbance at 254 nm, and color number were 61.38%, 83.89%, and 85.79%, respectively. Control experiments show that the UV-nZVI-H2O2 system has the highest removal rate and mineralization rate of refractory organic matter. The excellent performance of the UV-nZVI-H2O2 system is related to a higher H2O2 utilization rate. The H2O2 residue in the UV-nZVI-H2O2 system was the lowest, and the effective utilization rate of H2O2 was as high as 98.80%. Alcohol quenching experiments and hydroxyl radical quantitative experiments showed that the dominant reactive oxygen species in the UV-nZVI-H2O2 system was HO• and the yield of HO• was as high as 2007.80 μM, which was much higher than that in other systems. The results of spectra analysis showed that the low molecular weight, high fluorescence frequency organic matter, and relatively stable aromatic organic matter were significantly degraded after treatment with the UV-nZVI-H2O2 system and the aromatic degree, humification degree, molecular weight, and molecular polymerization degree of refractory organic matter were also significantly decreased. The mechanism of the UV-nZVI-H2O2 reaction includes homogeneous and heterogeneous Fenton reactions and adsorption and precipitation of organic matter by iron-based colloids. This study can provide theoretical and technical support for the advanced treatment of refractory organic matter in landfill leachate. [ABSTRACT FROM AUTHOR]

The new composite material was synthesised bonding nano zero-valent iron (NZVI) with liquid-phase chemical reduction method on the support material obtained by carbonising the organic waste mandarin peel, and the surface characteristics of it were determined by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), transmission electron microscope (TEM), X-ray diffraction (XRD), Brunauer–Emmett–Teller (BET) and zero point of charge (pHzpc). The effectiveness of the composite as an adsorbent in the removal of malachite green (MG) was investigated with different parameters. Equilibrium data were employed to different adsorption isotherms used in aqueous solutions, and the most suitable isotherm was found as Freundlich isotherm with the highest R2 =0.999 and the lowest chi-square (χ2) and residual root-mean-square error (RMSE) values. The maximum adsorption capacity was 909.09 mg/g according to Langmuir isotherm. When the kinetic data were analysed, the most appropriate kinetic model was determined as pseudo-second-order with the lowest χ2 and RMSE and the highest R2 (≥0.987) values. The adsorption process was carried out as endothermic (∆H°=145.79 kJ/mol) and spontaneously (∆G°≤−2.89kJ/mol) according to thermodynamic parameters. Also, it was possible to say that the irregularity at the adsorbent-adsorbate interface increased due to positive entropy. NZVI/carbonised mandarin peel (CMP) with high adsorption capacity could be used effectively to remove many industrial wastes. [ABSTRACT FROM AUTHOR]

In the present study, attapulgite (ATP)-maintained nanoscale zero-valent iron (nZVI) at different Fe/ATP mass ratios (1:3 and 1:5) was synthesized by liquid phase reduction for its use to remove chromium Cr(VI) in aqueous solution. The morphology, crystalline structure, chemical composition, and valent states of these nZVI/ATP composites were evaluated before and after the reaction. Obtained characterization data indicated an effective dispersion of nZVI on ATP surface, preventing the agglomeration of nZVI particles. Results showed that the introduction of ATP has higher Cr(VI) removal efficacy as compared to the bare nZVI or ATP. At Cr(VI) initial level of 40 mg L−1, the remediation efficacy of Cr(VI) in nZVI/ATP(1:3) reached 91.63%, which was substantially higher than that of bare nZVI (48.68%) and ATP (2.52%). Co-precipitation and reduction of Cr-containing metal deposited onto nZVI/ATP were found as the major reaction mechanisms. At lower initial level of Cr(VI) (20 mg L−1), the reduction was the dominant process where Fe(II) was the major form of iron in the reaction product. However, adsorption was the major mechanism at higher initial level of Cr(VI) (100 mg L−1) whereas the reaction product mainly comprised the ferric form of iron (Fe(III). The main reaction product was the FeCr2O4 under low or high Cr(VI) concentrations which can reduce the risk of secondary pollution because of its high stability. [ABSTRACT FROM AUTHOR]

Nano zero-valent iron (nZVI) coated with magnetite and an imidazolium-based ionic liquid (1-hexyl-3-methylimidazolium hexafluorophosphate (HMIMPF6)) core/shell nanoparticles (NPs) (nZVI@Fe3O4@HMIMPF6) were successfully green synthesized for the first time using industrial iron waste. Polyphenols were extracted from dried leaves of Camellia sinensis and applied as the reducing agent for nZVI synthesis. Synthesized NPs were characterized by FT-IR, XRD, VSM, BET, SEM, TEM, and mapping analysis. According to the results, NPs were in the size range of less than 30 nm and the values of a s , BET = 3.5975 m 2 g - 1 , V m (BET monolayer capacity) = 0.8265 cm 3 STP g - 1 , C = 47.378, total pore volume ( p p 0 = 0.990) = 0.14998 cm 3 g - 1 and mean pore diameter = 16.68 nm were obtained. These NPs were used for the Cr (VI) removal from aqueous samples. Taguchi orthogonal array design was used to optimize the various affecting variables on the efficiency of Cr (VI) removal. Results showed that about 90.0% of Cr (VI) were removed at the optimum conditions. Kinetic and isotherm studies were conducted, and the pseudo-second order kinetic model was determined as the most appropriate kinetic model. The equilibrium data displayed proper linearity with the Freundlich isotherm model (R2 = 0.9697), and the maximum adsorption capacity was found to be 56.49 mg g - 1 (in terms of CrO42− ions). Also, Redlich-Peterson, Sips, and Toth as three-parameter isotherm models were compared to two-parameter models using MATLAB's fmincon function. Thermodynamic studies showed negative ΔG°, ΔH° = 50.255 kJ mol−1, and ΔS° = + 0.1799 kJ mol−1 K−1 indicating spontaneous and endothermic adsorption process. According to the results, the nZVI @ Fe 3 O 4 @ IL NPs can be recovered by an external magnet and exhibit good applicability for Cr (VI) removal from real samples. Article Highlights: Core-shell structures of nZVI @ Fe 3 O 4 @ IL were synthesized for the first time Steel slag and waste rusted iron shavings were used as ferrous ion sources Polyphenols were extracted fromCamellia sinensisand used for biosynthesis of nZVI The obtained NPs were used for the removal of Cr (VI) ions from aqueous samples Two and three parameter isotherm models, kinetic and thermodynamic studies were investigated [ABSTRACT FROM AUTHOR]

The addition of nano zero-valent iron (nZVI) is a promising technology for the in situ remediation of soil. Unfortunately, the mobility and, consequently, the reactivity of nZVI particles in contaminated areas decrease due to their rapid aggregation. In this study, we determined how nZVI particles can be stabilized using different types of biochar (BC) as a support (BC@nZVI). In addition, we investigated the transport behavior of the synthesized BC@nZVI particles in a column filled with porous media and their effectiveness in the removal of BDE209 (decabromodiphenyl ether) from soil. The characterization results of N2 Brunauer-Emmett-Teller (BET) surface area analyses, scanning electron microscopy (SEM), X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR) indicated that nZVI was successfully loaded into the BC. The sedimentation test results and the experimental breakthrough curves indicated that all of the BC@nZVI composites manifested better stability and mobility than did the bare-nZVI particles, and the transport capacity of the particles increased with increasing flow velocity and porous medium size. Furthermore, the maximum concentrations of the column effluent for bagasse-BC@nZVI (B-BC@nZVI) were 19%, 37% and 48% higher than those for rice straw-BC@nZVI (R-BC@nZVI), wood chips-BC@nZVI (W-BC@nZVI) and corn stalks-BC@nZVI (C-BC@nZVI), respectively. A similar order was found for the removal and debromination efficiency of decabromodiphenyl ether (BDE209) by the aforementioned particles. Overall, the attachment of nZVI particles to BC significantly increased the reactivity, stability and mobility of B-BC@nZVI yielded, and nZVI the best performance. [ABSTRACT FROM AUTHOR]

Nano zero-valent iron (nZVI) particles have been identified as one of the potential candidate for the removal of various metal ions. This study addresses the effectiveness of nZVI on iron removal from an aqueous solution containing Fe2+/Fe3+ in the ratio of 2.5:0.5, which is not studied so far. Liquid-phase reduction technique was utilized to synthesize the nZVI. The characterization of nZVI and its interaction with iron in aqueous solution was found using transmission electron microscopy (TEM), scanning electron microscopy–energy dispersive X-ray (SEM–EDX), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), ultraviolet–visible spectroscopy (UV–Vis spectroscopy) and Fourier transform infrared spectroscopy (FTIR). It was found that the nZVI particles were largely spherical with size varying from 80–99 nm. Abundant oxygen functional groups detected in the FTIR spectrum serve as the accessible sites for iron adsorption. SEM and XRD studies provided a clear image of core-shell structure of nZVI. The study also investigated the role of pH, iron concentration, nZVI dosage and contact time on the uptake behaviour of contaminant iron. A removal efficiency of 63% was achieved in 3 h, with optimum nZVI loading of 5 g l−1, from a solution having initial iron concentration of 0.5 mg l−1 at natural solution pH 6.85. This efficiency was increased to 70% at optimum pH 10. The batch study revealed that adsorption kinetics followed pseudo-second-order kinetics with R2 value of 0.99 and data followed Dubinin–Radushkevich isotherm. Outcomes of the study recommend that nZVI could turn into a promising adsorbent for iron removal from aqueous solutions. [ABSTRACT FROM AUTHOR]

Sulfadiazine (SDZ) was effectively removed by the heterogeneous catalytic sulfate radical (SO4•−) oxidation using a novel composite material of mesoporous carbon (MC) loaded nano zero-valent iron (nZVI). Possessing larger specific area (433.3 m2 g−1) and high mesopores volume (2.537 cm3 g−1), the composite material (nZVI/MC) was used as the activator to activate persulfate for the degradation of SDZ. The results of degradation experiments indicated that the removal efficiency of SDZ in nZVI/MC+ persulfate (PS) process reached the highest, due to good dispersing property of MC for nZVI. The removal of SDZ was further enhanced by the increase of nZVI loading as well as the nZVI/MC composite content. Quenching experiments showed that SO4•− acted a crucial role in the degradation process of SDZ. Both the FT-IR and XPS analyses showed that the FeO contents decreased after degradation reaction, which indicated the occurrence of active oxidation reaction between SO4•− and Fe2+ from the breakage of the Fe–O bond. The LC-MS analysis indicated that the cleavages of C–N bond in the heterocyclic ring and N–S bond were the major degradation pathway of SDZ, attributing to the attack of SO4•− and •OH. These results demonstrated that the novel nZVI/MC composite with excellent stability could be used for the effective degradation of SDZ through activating PS to produce SO4•−. [ABSTRACT FROM AUTHOR]

Given their considerable solubility in water and potentially high toxicity to human health, organoarsenic compounds have become an emerging contaminant. Herein, a heterogeneous Fenton process mediated by SiO2-coated nano zero-valent iron (SiO2-nZVI) was employed to simultaneously remove the p-arsanilic acid (p-ASA, a typical organoarsenic compound) and the released arsenic. The initial pH value significantly influenced on the degradation of p-ASA and at the optimal pH (3.0), p-ASA (10 mg L−1) could be completely oxidized to As(V), NH4+, and plentiful phenolic compounds such as phenol and p-hydroquinone via the cleavage of C–N and C–As bonds within 60 min in pure water. Meanwhile, although the formed lepidocrocite and magnetite on the surface of SiO2-nZVI significantly limited the reutilization, they played a vital role in the adsorption of the released As(V) and the residual arsenic levels in the effluent were as low as 0.031 mg L−1, meeting both the drinking water standard of the World Health Organization (WHO) and the surface water standard of China (0.05 mg L−1). Furthermore, high-level dissolved organic matters (DOM) (> 2 mg C L−1) exhibited strong interference with both the oxidation of p-ASA and adsorption of arsenic, but the interference could be eliminated by increasing the SiO2-nZVI dosage or adding H2O2. Importantly, this system could completely remediate p-ASA in a short time and simultaneously avoid the secondary pollution caused by inorganic arsenic, which was significant for the remediation of organoarsenic pollutants in swine wastewater. [ABSTRACT FROM AUTHOR]

Nano zero-valent iron (nZVI) is one of the most paramount nanoparticles (NPs) applied in environmental remediation, leading to great concerns for the potential impacts on soil ecosystem health. The objective of this study was to link toxicokinetics and consumer–resource dynamics in the Caenorhabditis elegans–Escherichia coli (worm–bacteria) ecosystem. The biokinetic parameters of bacteria and worms were obtained from toxicokinetic experiments and related published literature. Biomass dynamics of bacteria and worms were estimated by employing the modified Lotka–Volterra model. Dynamics of bacteria and worm biomass, internal concentrations of nZVI, bioconcentration factors (BCFs), and biomagnification factors (BMFs) were simulated based on the consumer–resource dynamics. Results showed that the biomass of worms steadily increased from 22.25 to 291.49 g L−1, whereas the biomass of bacteria decreased from 17.17 to 4.70 × 10−8 g L−1 after 96-h exposures of nZVI. We also observed ratios of nZVI concentrations in worms and bacteria increased from 0.06 to 26.60 after 96 h. Moreover, decrements of the bioconcentration factor of E. coli (BCFE) values from 0.82 to 0.03 after 96 h were observed, whereas values of BMFs increased from 0.06 to 57.62 after 96 h. Internal concentrations of nZVI in worms were found to be mainly influenced by the ingestion rate of bacteria by worms, and the biomass conversion of bacteria had the lowest effect. Implementation of the integrated bioaccumulation–consumer–resource model supports the hypothesis that the C. elegans–E. coli dynamics of internal nZVI concentrations could be effectively associated with the predator–prey behavior and was dominated by the same physiological parameter in the two biological systems. [ABSTRACT FROM AUTHOR]

The effects of humic acid (HA) and its different molecular weight (MW) fractions on the sedimentation of nanoscale zero-valent iron (NZVI) in the absence and presence of cations (i.e., Na+/Mg2+/Ca2+) were investigated. Ultrafiltration (UF) was used as the method of fractionation to obtain four different MW fractions (separated by ultrafiltration membranes of 10 kDa, 50 kDa, and 100 kDa). Differing sedimentation behavior was observed for NZVI with different MW fractions of HA. Generally, the degree of settling of NZVI particles in the presence of high MW fractions of HA was lower than that of low MW fractions of HA and that without HA. The results were mainly attributed to the steric stabilization provided by the high MW fractions of HA. The presence of Na+/Mg2+/Ca2+ alone had insignificant influence on the settling of NZVI, but both Mg2+ and Ca2+ exerted an obvious influence on the settling of NZVI in the co-presence of HA. The settling behavior of NZVI was further examined in the co-presence of different MW fractions of HA and Ca2+. The co-presence of low MW HA fractions and Ca2+ led to a lower settling of NZVI. This might be due to the formation of a layer of HA-Ca2+ complex on the particle surface, providing stronger steric stabilization. Nevertheless, in the co-presence of high MW HA fractions and Ca2+, the settling of NZVI was initially reduced but accelerated with time, which might be due to the gradual aggregation of NZVI with time resulted from the bridging effect of HA-Ca2+ complex. [ABSTRACT FROM AUTHOR]

Aging effects play a crucial role in determining applications of green-synthesised iron-based nanoparticles in wastewater treatment from laboratory scale to practical applications. In this study, iron-based nanoparticles (Ec-Fe-NPs) were synthesised using the extract of Eichhornia crassipes and ferric chloride. Scanning electron microscopy (SEM) revealed that the fresh Ec-Fe-NPs were spherical and had a narrow particle size range (50 to 80 nm). X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) demonstrated that the Ec-Fe-NPs were mainly amorphous in nature and consisted of Fe0, FeO, Fe2O3 and Fe3O4. As they aged, the particle size of the liquid Ec-Fe-NPs gradually increased and then tended to stabilise. Ec-Fe-NPs that were aged for 28 days were only 19% less efficient than fresh material at removing Cr(VI). Extracts aged up to 28 days were also tested, and their antioxidant capacity was found to be 15.4% lower than that of the fresh extracts. Furthermore, the removal efficiency of Cr(VI) using iron-based nanoparticles synthesised with the aged extracts was 67.2%. Finally, the active components of the extracts, which were responsible for the reactivity and stability of the iron-based nanoparticles, were identified by liquid chromatography–mass spectrometry. Overall, green-synthesised iron-based nanoparticles show promise for Cr(VI) removal from wastewater in practical applications. [ABSTRACT FROM AUTHOR]

Photocatalytic degradation of 4-chlrophenol (4-CP) using UVA-LED assisted persulfate and hydrogen peroxide activated by the nZVI (Nano Zero Valent Iron) in a batch photocatalytic reactor was investigated. The reaction involved a lab-scale photoreactor irradiated with UVA-LED light emitted at 390 nm. The efficiency of the reaction was evaluted in terms of 4-CP degradation and mineralization degree at different pH of solution, initial concentrations of nZVI, persulfate, hydrogen peroxide and 4-CP. In UVA-LED/H2O2/nZVI process, complete degradation of 4-CP (>99%) and 75% mineralization was achieved at pH of 3, hydrogen peroxide concentration of 0.75 mM, nZVI dosage of 1mM and initial 4-CP concentration of 25mg/L at the reaction time of 30 min. The optimum conditions obtained for the best 4-CP degradation rate were at an initial concentration of 25mg/l, persulfate concentration of 1.5mM, nZVI dosage of 1mM, pH of 3 and reaction time of 120min for UVA-LED/persulfate/nZVI process. It was also observed that the 4-CP degradation rate is dependent on initial 4-CP concentrations for both processes. The pseudo-first-order kinetic constant at 25mg/L initial concentration of 4-CP was found to be 1.4×10−1 and 3.8×10−2 in UVA-LED/H2O2/nZVI and UVA-LED/persulfate/nZVI processes, respectively. Briefly, the UVA-LED/H2O2/nZVI process enhanced the degradation rate of 4-CP by 3.67-times in comparison to UVA-LED/persulfate/nZVI process at 30min contact time, which serves as a new and feasible approach for the degradation of 4-CP as well as other organic contaminants containing wastewater. [ABSTRACT FROM AUTHOR]

Recently, nano zero-valent iron (nZVI) has emerged as an effective adsorbent for the removal of arsenic from aqueous solutions. However, its use in various applications has suffered from reactivity loss resulting in a decreased efficiency. Thus, the aim of this study was to develop an effective arsenic adsorbent as a core/shell structural nZVI/manganese oxide (or nZVI/Mn oxide) to minimize the reactivity loss of the nZVI. As the major result, the arsenic adsorption capacities of the nZVI/Mn oxide for As(V) and As(III) were approximately two and three times higher than that of the nZVI, respectively. In addition, the As(V) removal efficiency of the nZVI/Mn oxide was maintained through 4 cycles of regeneration whereas that of the nZVI was decreased significantly. The enhanced reactivity and reusability of the nZVI/Mn oxide can be successfully explained by the synergistic interaction of the nZVI core and manganese oxide shell, in which the manganese oxides participate in oxidation reactions with corroded Fe and subsequently retard the release of aqueous iron providing additional surface sites for arsenic adsorption. In summary, this study reports the successful fabrication of a core/shell nZVI/Mn oxide as an effective adsorbent for the removal of arsenic from aqueous solutions. [ABSTRACT FROM AUTHOR]

Monoethanolamine (shortly ethanolamine (ETA)), usually used as a corrosion inhibitor, is a contaminant of wastewater from the secondary cooling system of nuclear power plants (NPPs) and is not readily biodegradable. We conducted various experiments, including treatments with nano zero-valent iron (nZVI), nano-iron/calcium, and calcium oxide (nFe/Ca/CaO) with ozone (O) or hydrogen peroxide (HO) to reduce the concentration of ETA and to decrease the chemical demand of oxygen (COD) of these wastewaters. During this study, wastewater with ETA concentration of 7465 mg L and COD of 6920 mg L was used. As a result, the ETA concentration was reduced to 5 mg L (a decrease of almost 100%) and COD was reduced to 2260 mg L, a reduction of 67%, using doses of 26.8 mM of nZVI and 1.5 mM of HO at pH 3 for 3 h. Further treatment for 48 h allowed a decrease of COD by almost 97%. Some mechanistic considerations are proposed in order to explain the degradation pathway. The developed hybrid nano zero-valent iron-initiated oxidation process with HO is promising in the treatment of ETA-contaminated wastewaters. [ABSTRACT FROM AUTHOR]

Some problems exist in the current remediation of polybrominated diphenyl ethers (PBDEs) from aqueous solution by using iron-based nanoparticles. Our efforts have contributed to the synthesis of biochar-supported Ni/Fe bimetallic nanoparticle composites (BC@Ni/Fe). Under the optimum operating parameters of BC@Ni/Fe, the morphologic analysis revealed that biochar effectively solved the agglomeration of Ni/Fe nanoparticles and the removal efficiency of BDE209 obtained by BC@Ni/Fe (91.29%) was seven times higher than the sum of biochar (2.55%) and Ni/Fe (11.22%) in 10 min. The degradation products of BDE209 in the solution and absorbed on the BC@Ni/Fe were analyzed with gas chromatography-mass spectroscopy, which indicated that the degradation of BDE209 was mainly a process of stepwise debromination. Meanwhile, compared with Ni/Fe nanoparticles, the adsorption ability of the by-products of BDE209 by BC@Ni/Fe was greater, to a certain extent, which reduced the additional environmental burden. In addition, the concentration of nickle ion leaching from the Ni/Fe nanoparticles was 3.09 mg/L; conversely, the concentration of nickle leaching from BC@Ni/Fe was not detected. This excellent performance in our study indicates a possible means to enhance the reactivity and reduce the secondary risks of Ni/Fe nanoparticles. [ABSTRACT FROM AUTHOR]

This study reports on the direct reduction of hexavalent chromium [Cr(VI)] by green tea polyphenols, including a green tea solution and pure epigallocatechin gallate (EGCG) solution. A linear trend was observed between the amount of reduced Cr(VI) and the amount of added polyphenols. The green tea solution showed a continued decrease in the observed stoichiometry with increasing pH, from a maximum of 1.4 mol per gallic acid equivalent (GAE) of green tea at pH 2.5, to 0.2 mol/GAE at pH 8.8. The EGCG solution exhibited different behavior, with a maximum stoichiometry of 2 at pH 7 and minimum of 1.6 at pH 4.4 and 8.9. When green tea was used to first react with Fe and form GT-nZVI, the amount of Cr(VI) reduced by a certain volume of GT-nZVI was double compared to green tea, and 6 times as high considering that GT-nZVI only contains 33 % green tea. [ABSTRACT FROM AUTHOR]

In this paper, the mesoporous silica MCM-41 supporting nano zero valent iron (MSNZVI) composite was synthesized in a facile way and characterized by XRD, FT-IR, TEM and N adsorption-desorption. The catalytic activity of the as-prepared MSNZVI composite as a catalyst was evaluated on the p-nitrophenol reduction in the presence of excess NaBH. And the rate constant is 4.89 × 10 s when the mole ratio of NaBH to p-nitrophenol is 500. MSNZVI composite can be reused for at least five cycles with stable catalytic activity. Moreover, a possible catalytic mechanism of MSNZVI was proposed to explain the reduction of p-nitrophenol by NaBH. [ABSTRACT FROM AUTHOR]

This study examined the transport behavior of nano zero-valent iron (NZVI) coated with three types of stabilizers (i.e., polyacrylic acid, Tween-20, and starch) in saturated sand- and soil-packed columns under varying geochemical conditions. The cations or ionic strength and humic acid (HA) affected the transport of NZVI in varying degrees for different types of surface-modified NZVI (SM-NZVI). The effects of HA on the transport of SM-NZVI were different in sand- and soil-packed columns. In the sand-packed column, the presence of HA exerted an effect on the particle-particle interaction (i.e., aggregation), resulting in either enhanced or decreased transport of SM-NZVI. However, in the soil-packed column, the HA not only influenced the particle-particle interaction but also exerted an effect on the particle-soil grain interaction (i.e., deposition). Additionally, a significant enhancement in the transport of SM-NZVI in the soil-packed column was observed with increasing particle concentration. Moreover, the adsorption of arsenic on the surface of SM-NZVI exhibited insignificant effect on the transport of SM-NZVI. The release of arsenic from the arsenic-loaded SM-NZVI was detected when subjected to flushing with phosphate-containing groundwater. This fundamental understanding of the subsurface transport of SM-NZVI is of critical importance for the benign use and risk management of SM-NZVI. [ABSTRACT FROM AUTHOR]