Search

Fe 3 O 4 has the advantages of unique magnetic stability and low biological toxicity, which can improve pollutants separation efficiency. MXenes are two-dimensional materials and easy surface functionalization that can provide suitable carriers for Fe 3 O 4. In this work, we synthesized magnetic MXene composites by a one-pot method that relies on doping Fe 3 O 4 particles onto Ti 3 C 2 MXene nanosheets by heat treatment. The Fe 3 O 4 /Ti 3 C 2 MXene was analyzed by SEM, XRD, FTIR and XPS techniques, which showed that the material has good tetracycline (TC) removal properties and magnetic separation ability. The results showed that the adsorption capacity of it was 46.42 mg g−1, and the removal efficiency of 0.06 g adsorbent for 50 mL of 30 mg L−1 TC could reach 92.1% in a wide pH range of 4–10, when the adsorption temperature was 25 °C, and the adsorption time was 3 h. The adsorption data were consistent with Langmuir and the proposed second-order kinetic model, and the thermodynamic experiments confirmed that the adsorption of TC was a monolayer physicochemical adsorption coexisting heat-trapping process (ΔH = 15.72 kJ mol−1). In addition, the adsorption of TC by Fe 3 O 4 /Ti 3 C 2 MXene was attributed to the synergistic effect of electrostatic attraction, hydrogen bonding and π-π packing. In conclusion, the saturation magnetization of Fe 3 O 4 /Ti 3 C 2 MXene is 27.3 emu/g and it can not only be separated from water using its strong magnetic properties to avoid secondary contamination, but also can be used as a promising material to effectively remove antibiotics from aqueous media. [Display omitted] • A kind of magnetically recyclable, regenerative adsorbent for tetracycline adsorption (Q max = 46.42 mg g−1) has been obtained. • The mechanisms of Fe 3 O 4 /Ti 3 C 2 adsorbing tetracycline: endothermic adsorption; the quick absorption of pollutants is facilitated by the electrostatic interactions, π−π bonds and hydrogen bonds. • The adsorption occurs over a wide pH range of 4–10. [ABSTRACT FROM AUTHOR]

Abstract Naphthols are industrial contaminants occurring widely in soils and waters. Remediation of organic pollutants can be done by chemical oxidation using persulfate. However, most research experiments testing degradation of organic pollutants have been done in ideal conditions, e.g. using a pure compound in pure water, and thus are weakly representative of real natural conditions where pollutants occur in complex mixtures of numerous organic compounds. Therefore we tested here the effect of the presence of small organic acids, as typical compounds occurring in natural media, on the degradation of 1-napthol with persulfate and iron oxides. Results show that organic acids decreased naphthol transformation by 3.7% for malic acid, 53.2% for tartaric acid, 72.3% for citric acid and 77% for oxalic acids, in a magnetite/persulfate system during 10 h. Meanwhile, the dissolved Fe species increased gradually with the reaction time; the highest concentration of Fe ions reached to ∼18 μM L−1 in aqueous phase. Electron paramagnetic resonance technique was applied to determine reactive oxygen species (ROS). The spin density of ·OH, detected as the main ROS, decreased initially, followed by gradually increase, suggesting that organic acids might inhibit the degradation of 1-naphthol by competing with ·OH. These findings disclose the high inhibition of the transformation by organic acids, and thus, more generally, imply that studies using only pure contaminants are weakly representative for remediation of real, natural samples. Graphical abstract Image 1 Highlights • LMWOAs exhibit inhibitory effect on 1-naphthol degradation in iron oxide/PS systems • Both of LMWOA molecular structure and iron oxide type affect 1-naphthol degradation • LMWOAs inhibit the heterogeneous activation via competition sorption on Fe surface • LMWOAs can dissolve iron oxides ions and improve the homogeneous activation of PS [ABSTRACT FROM AUTHOR]

ortho -Nitroaniline (o -NA) compounds are deemed to be a strongly toxic pollutant in nature and potentially carcinogenic; however, they are frequently utilized to synthesize dyes, pesticides, medicines, fungicides, pigments, and other organic chemicals. Their detection in an aqueous medium is fundamentally required to avoid the potential hazardous being created by these compounds. In this study, a novel sensor based on an Iron oxide (Fe 3 O 4) containing highly dispersed nitrogen-doped carbon quantum dots (N -CQDs@Fe 3 O 4 NFs) was demonstrated for the electrochemical detection of o -NA using differential pulse voltammetry (DPV) and cyclic voltammetry (CV) techniques. N -CQDs@Fe 3 O 4 NFs were synthesized by hydrothermal method and studied by various analytical and spectroscopy techniques, which collectively reveal that the as-prepared composite has superior physical and chemical properties. The DPV study indicated that the o -NA sensor had a good limit of detection, linear range, and sensitivity in the range of 1.2 nm, 0.03–386.84 μ M, and 36.5575 μ A μM−1 cm−2, respectively, along with the sensor showed superior sensitivity when compared to the previously reported modified electrodes. Further, N -CQD/Fe 3 O 4 NFs worked as heterogeneous catalysts for the photocatalytic reduction of o -NA to o -phenylenediamine (o -PD) in an aqueous medium. The reaction was examined under UV–Visible spectroscopy, and the complete photocatalytic reduction was observed for the N -CQD/Fe 3 O 4 NFs in about 6 min with 96% as compared to other control samples; thus, authenticating the superiority of the synthesized composite in rendering the real-time applications. [Display omitted] • N -CQDs@Fe 3 O 4 NFs catalyst was prepared by hydrothermal method to detect the environmentally hazardous organic pollutant. • The o -NA sensor showed an excellent limit of detection of about 1.2 nM. • In addition, the N -CQDs@Fe 3 O 4 NFs catalyst is used for the photo-catalytic reduction of o -NA to OPD. • The electrocatalytic and photocatalytic studies are performed by CV, DPV, and UV–Visible spectroscopy. [ABSTRACT FROM AUTHOR]

Iron oxide-lignin composites (GLS) were prepared based on the significant role of Fe-OM in the environmental behaviour of heavy metals and lignin binding with iron oxide preferentially in soil. GLS was applied in Cd/Pb immobilization and the stability under acid rain was investigated. The results show that the iron oxide appeared weakly crystalline or amorphous similar to 2-line ferrihydrite after the addition of lignin. Agglomerates of nanoparticles with higher adsorption capacity were observed for GLS. The mobility factor (MF) of Cd/Pb in the soil decreased rapidly after adding GLS. At the 3% dosage, the MF of Cd and Pb in the soil was decreased by 58.94% and 78.15% respectively, which was approximately 5 times that of goethite (GE). The mobile and exchangeable Cd/Pb were converted to organic, amorphous Fe oxide-bound and residue fractions. Under acid rain conditions, MF continues to decline for the GLS group, increasing the organic and amorphous Fe oxide-bound fractions, while for control group (CK) and GE, the trend was the opposite. Lignin could inhibit iron oxide dissolution and stabilize the combination of Cd/Pb and iron oxides in soil. The better stability performance of GLS for Cd/Pb may be related to the higher adsorption capacity and microstructural difference after iron oxide combined with lignin. [Display omitted] • Iron oxide-lignin composites (GLS) show a higher adsorption capacity than goethite. • The mobility of Cd/Pb was decreased significantly after GLS application. • The stability of iron oxide was enhanced after combining with lignin. • GLS application consistently reduces the Cd/Pb leaching under acid rain conditions. [ABSTRACT FROM AUTHOR]

Successful mining soil reclamation promotes ecosystem recovery, reduces negative environmental effects, adds more area for forestry or agricultural purposes, and increases carbon (C) sequestration. In order to increase soil erosion management, improve soil quality, reduce pollutants, and assure safe land application of traditional amendment materials, nanoparticles with exceptionally high deliverability and reactivity may be used as amendments. Iron oxide is being researched for the remediation of industrial soil that is co-contaminated with arsenic (AS) due to the absence of Nano enhanced materials for mine soil reclamation. In order to improve the soil quality of a mine waste that was heavily polluted with As (1807 mg/kg), the effects of iron oxide on the non-specifically and specifically-sorbed As were investigated. Iron oxide was added to the polluted soil at concentrations of 0.5 percent, 2 percent, and 5 percent (w/w). The goal of this work is to define the effect of iron oxide and Zero Valent I nanoparticles (nZVI) in reducing the contamination of soil by the use of soft computing models of extreme learning machines (ELM) with particle swarm optimization (PSO). In this case, the hybrid ELM-PSO has shown good performance as a trustworthy approach after the regression study of RMSE, R-square, and r. The addition of iron oxide dosages decreased the easily accessible As by 92.4 when compared to the untreated soil, with the 5 percent doses having a noticeably greater effect. [Display omitted] • Effects of iron oxide on the non-specifically and specifically-sorbed As were investigated. • Iron oxide was added to the polluted soil at concentrations of 0.5, 2 and 5 percent (w/w). • Effect of iron oxide and Zero Valent I nanoparticles in reducing the contamination of soil assessed. • Combination of soft computing models of ELM with PSO as hybrid model used. • Addition of iron oxide dosages decreased the easily accessible As by 92.4. [ABSTRACT FROM AUTHOR]

Arsenic (As) is a redox-active metalloid whose toxicity and mobility in soil depend on its oxidation state. Arsenite [As(III)] can be oxidized by microbes and adsorbed by minerals in the soil. However, the combined effects of these abiotic and biotic processes are not well understood. In this study, the fate of arsenic in the presence of an isolated As(III)-oxidizing bacterium ( Pseudomonas sp. HN-1, 10 9 colony-forming units (CFUs)·ml −1 ) and three iron oxides (goethite, hematite, and magnetite at 1.6 g L −1 ) was determined using batch experiments. The total As adsorption by iron oxides was lower with bacteria present and was higher with iron oxides alone. The total As adsorption decreased by 78.6%, 36.0% and 79.7% for goethite, hematite and magnetite, respectively, due to the presence of bacteria. As(III) adsorbed on iron oxides could also be oxidized by Pseudomonas sp. HN-1, but the oxidation rate (1.3 μmol h −1 ) was much slower than the rate in the aqueous phase (96.2 μmol h −1 ). Therefore, the results of other studies with minerals only might overestimate the adsorptive capacity of solids in natural systems; the presence of minerals might hinder As(III) oxidation by microbes. Under aerobic conditions, in the presence of iron oxides and As(III)-oxidizing bacteria, arsenic is adsorbed onto iron oxides within the adsorption capacity, and As(V) is the primary form in the solid and aqueous phases. [ABSTRACT FROM AUTHOR]

The disposal of paint waste from bridge rehabilitation is a significant issue because of the potential release of contaminants and the consequent impact to human health and the environment. In this study, leaching behavior of paint waste was evaluated for 24 bridges in New York State. Although elevated Pb (5–168,090 mg kg −1 ) and other metal concentrations were observed in the paint samples, leaching experiments that included the toxicity characteristic leaching procedure (TCLP) and the multiple extraction procedure (MEP) revealed toxicity characteristic (TC) limits were not exceeded. The relatively low concentrations observed are attributed to the use of iron-based abrasives (steel grit) in the paint removal process. In this research, trace metals are hypothesized to be sequestered through interactions with iron oxide coatings formed on the steel grit surface resulting in reduced leachable concentrations. Through sequential extraction iron oxides were observed at 11.03% by wt and X-ray diffraction (XRD) further corroborated the presence of iron oxide coatings on the steel grit surface. Sequential extraction demonstrated that less than 6.8% of Pb, Cr, and Ba were associated with the exchangeable and carbonate forms, while greater contributions were found with iron oxides. The largest fraction, however, greater than 80%, was associated with the residual phase comprised of minerals in the paint including SiO 2 and TiO 2 . [ABSTRACT FROM AUTHOR]

Highlights: [•] Coating with Fe or Al oxides increases the sorption of P by LECA. [•] At pH greater than 6 the sorption by AOCL is more efficient than that by IOCL. [•] The sorption by AOCL is less reversible than that by IOCL. [•] AOCL is not redox sensitive and, thus, superior to IOCL as sorbent in CWs. [ABSTRACT FROM AUTHOR]

Artificially mimicking structures/morphologies available in the nature to develop multifunctional materials for catalysis is receiving greater attention. Particularly, the burdock flower morphology, which has a hollow-globe surrounded by spiky sheets, represents a multifunctional structure helpful in adsorption as well as intercalation of molecules. Given this, we have strategically developed a robust microwave (MW) bubble-template process to achieve highly uniform α-Fe 2 O 3 and carbon-enriched Fe 3 O 4 (Fe 3 O 4 @C) phases resembling the characteristics of spiky hollow burdock morphologies. The utilization of the MW bubble-templates as a pretreatment to the iron-based precursor solution helps in producing hollowed open-space ferrous glycolate burdock flower morphology with rapid production rate and without any addition of extra agents. Such burdock flower structures remain intact even after annealing in air/N 2 ambiance providing highly photoactive α-Fe 2 O 3 or magnetic Fe 3 O 4 @C, respectively. Utilizing the hollow burdock flower structures together with the individual photo/magnetic properties of iron oxide phases, a dual-layer filter was designed to remove hazardous dye molecules from water, which efficiently photodegraded (99.2 %) in natural sunlight as well as showed excellent adsorption (99.7 %) within minutes. Comparatively, a lower catalytic activity using simple iron oxide nanoparticles, closed, and faded burdock morphologies were seen. Hence, the high catalytic activity in removing the dye molecules, retention of structural phases after repeated use, and strong durability were a result of the synergetic effect of photo/magnetic properties, activated surface/spiky open burdock structure. Polymerized growth of FG nanoflakes on MW-induced glycol bubble templates.Their smooth transitions towards α-Fe 2 O 3 (photocatalyst) and Fe 3 O 4 @C (efficient adsorbent) hollowmicrourchins under suitable annealing conditions. Inset: (Right) shows structural/morphological transformation of product with concentration/MW-dose. [Display omitted] [ABSTRACT FROM AUTHOR]

We prepared two-dimensional (2D) stack-structured magnetic iron oxide (Fe 3 O 4) nanoparticle anchored titanium carbide (Ti 3 C 2 T x) MXene material (Ti 3 C 2 T x /Fe 3 O 4). It was used as a potential adsorbent to remove carcinogenic cationic dyes, such as methylene blue (MB) and rhodamine B (Rh B), from aqueous solutions. Ti 3 C 2 T x /Fe 3 O 4 exhibited maximum adsorption capacities of 153 and 86 mg g−1 for MB and Rh B dyes, respectively. Batch adsorption experimental data fits the Langmuir model well, revealing monolayer adsorption of MB and Rh B onto the adsorption sites of Ti 3 C 2 T x /Fe 3 O 4. Additionally, Ti 3 C 2 T x /Fe 3 O 4 showed rapid MB/Rh B adsorption kinetics and attained equilibrium within 45 min. Moreover, Ti 3 C 2 T x /Fe 3 O 4 demonstrated recyclability over four cycles with high stability due to the presence of magnetic Fe 3 O 4 nanoparticles. Furthermore, it exhibited remarkable selectivities of 91% and 88% in the presence of co-existing cationic and anionic dyes, respectively. Given the extraordinary adsorption capacities, Ti 3 C 2 T x /Fe 3 O 4 may be a promising material for the effective removal of cationic dyes from aqueous media. [Display omitted] • Magnetic 2D MXene material towards multiple cationic dye sequestration. • Unprecedented MB and Rh B adsorption capacities of 153 and 86 mg g−1, respectively. • Presence of Fe 3 O 4 provides excellent regeneration capability with high stability. • High selectivities of 91 % and 88 % for MB and Rh B, respectively, with rapid kinetics. • MB and Rh B removal via electrostatic attraction and hydrogen bonding with MXene. [ABSTRACT FROM AUTHOR]

Abstract: Methane (CH4) formation under aerobic conditions has been intensely debated, especially since the discovery of CH4 generation by both dried plant material and living plants. In this study we test the hypothesis that non-microbial CH4 formation also occurs in soils. All lyophilised soil samples investigated under aerobic conditions released CH4 at temperatures ranging from 30 to 70°C exceeding that allowing normal enzymatic activity to proceed. No emissions were observed for single mineral soil components such as quartz sand, clay mineral and iron oxide. Methane release rates from the soils investigated were found to increase both with increasing temperature and higher organic carbon content. Addition of water to dried soils increased CH4 release rates up to 8-fold those observed with the dried material. Our results suggest the existence of a chemical process in soils that produces CH4 under aerobic conditions, a finding which has not been hitherto reported. [Copyright &y& Elsevier]

Abstract: In this study, we examined the experimental catalytic oxidation of gaseous monochlorobenzene (MCBz) with O3 over Fe2O3 in a packed bed reactor to investigate the feasibility of economical low temperature decomposition at a high space velocity (SV). We investigated the effects of several reaction parameters (temperature, O3 concentration, and SV) on the MCBz oxidation. At 150°C, the conversion of MCBz over Fe2O3 in the absence of O3 was only 3%; it increased to 91% over Fe2O3 in the presence of 1200ppm of O3 at a high SV of 83s−1. A long-term operation study revealed that the conversion of MCBz was stable for more than 96h. In the steady state, the carbon and chlorine balances were 88% and 86%, respectively. Applying a Langmuir–Hinshelwood kinetic model, we estimated an activation energy of 16.7kJmol−1 for MCBz oxidation over Fe2O3 in the presence of O3. [ABSTRACT FROM AUTHOR]

Airstreams polluted with H2S at inlet loads ranging from 2.4 to 40.9g H2Sm−3 h−1 were treated in a biotrickling reactor packed with hematite bearing, open pore foam units, at Empty Bed Residence Times (EBRT) ranging from 20 to 60s over a period of 80d, with almost complete removal of the pollutant from the startup of the system. The media had been seeded with sludge from a local water works facility, and removal efficiencies in excess of 80% were consistently observed along the operation of the reactor, with an average of 98%. Based on section performance, being a section one third of the bed length, observed elimination capacities (EC) reached up to 88.7g H2Sm−3 h − 1 and 72.0g H2Sm−3 h−1 at section EBRT of 10 and 7s, respectively. The observed EC values compared much better than data reported on other packed bed reactors using biological iron oxidization to treat H2S airstreams indirectly, and so did it when comparing the EC per unit of specific area in a similar study using polyurethane (PU) foams. Further, and unlike PU packed biofilters, no compaction occurred due to the iron foam rigidity, which translated in much better observed gas phase pressure drop as opposed to other conventional biofilters. Denaturing gel gradient electrophoresis was performed on the biomass collected in the packing after the biofilter service, and it was found that though a multi bacterial colony was seeded in the system via the sludge, the only surviving genus was the iron oxidizing Alicyclobacillus spp. [Copyright &y& Elsevier]

Arsenic poses a major environmental and human health problem because of its carcinogenic nature and effect on the ecosystem. Therefore, a cost effective and socially acceptable technique is needed for its remediation. The effect of different combinations of compost amended with zeolite and/or iron oxide (up to 20% w/w) was tested on a contaminated soil with high arsenic levels (34470mgkg−1). The bioavailability of arsenic was determined in terms of uptake by rye grass (Lolium perenne L.) under greenhouse experimental conditions. The results indicated that the arsenic concentrations in the rye grass was reduced to 2mgkg−1 dry weight by using 15% compost with 5% iron oxide and 15% compost with 5% zeolite. Less than 0.01% of the total arsenic content in the soil was being taken up by the plants. Both treatments were effective in establishing significantly higher plant growth on the contaminated soil compared to other treatments. The results from sequential extraction tests indicated that in all the compost-amended soils, there was a reduction in the soluble fraction (10–37%). Arsenic in soil was examined using Scanning Electron Microscopy coupled with Energy Dispersive X-ray spectroscopy. The results indicated that arsenic was distributed mostly within the matrix of iron and oxygen in treated samples. Amongst various treatment mixtures tested, high percent of compost (15%) with zeolite (5%) and/or iron oxide (5%) is effective in reducing arsenic uptake by plants and establish re-vegetation on the contaminated soil. [Copyright &y& Elsevier]

Catalytic oxidation of PCDD/Fs (polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans) with ozone (catalytic ozonation) over nano-sized iron oxides (denoted as Fe x O y ) was carried out at temperature of 120–180°C. The effects of operating temperature, ozone concentration, space velocity (SV) and water vapor contents on PCDD/F removal and destruction efficiencies via catalytic ozonation were investigated. High activity of the iron oxide catalyst towards PCDD/F decomposition was observed even at low temperatures with the aid of ozone. The PCDD/F removal and destruction efficiencies achieved with Fe x O y /O3 at 180°C reach 94% and 91%, respectively. In the absence of ozone, the destruction efficiencies of all PCDD/F congeners are below 20% and decrease with increasing chlorination level of PCDD/F congener at lower temperature (120°C). However, in the presence of ozone, the destruction efficiencies of all PCDD/F congeners are over 80% on Fe x O y /O3 at 180°C. Higher temperature and ozone addition increase the activity of iron oxide for the decomposition of PCDD/Fs. Additionally, in the presence of 5% water vapor, the destruction efficiency of the PCDD/Fs is above 90% even at lower operating temperature (150°C). It indicates that the presence of appropriate amount of water vapor enhances the catalytic activity for the decomposition of gas-phase PCDD/Fs. [Copyright &y& Elsevier]

Abstract: The present work extended our knowledge on the binding and complexation of a fulvic acid (FA) derived from leonardite and the iron oxides (hematite, goethite and akaganeite) by Fourier transform infrared spectroscopy (FTIR). As a prerequisite, the iron oxides were firstly prepared and characterized by transmission electron micrograph (TEM). All iron phases were single and well-described crystalloid. The FTIR data obtained by two different sampling preparation methods gave the consisting evidences that under our experimental conditions the interaction mechanism was to the ligand-exchange involving carboxylic functional groups of the FA and the surfaces sites of both hematite and goethite, while no complexation can be evidenced in the case of akaganeite, only surface adsorption. In general, the binding affinities of the iron oxides with the FA was in the order of hematite>goethite>akaganeite. The present method, although associated with some uncertainties, provided an opportunity to increase the knowledge in the field of the humic chemistry. [Copyright &y& Elsevier]

Our previous work applied a novel supported iron oxyhydroxide (FeOOH) catalyst to effectively treat benzoic acid by hydrogen peroxide. The FeOOH catalyst was prepared via the oxidation of Fe2+ by H2O2 in the acidic condition using a fluidized-bed crystallization reactor. The major components coated on the surface were identified as amorphous FeOOH and γ-FeOOH.In terms of the crystallization conditions of FeOOH, some parameters including the operational pH, superficial velocity, specific iron loading, and influent H2O2 concentration were investigated to quantify their effects on the crystallization efficiency. All these parameters were found to significantly influence the crystallization efficiency. Two types of FeOOH catalysts were synthesized: FeOOH I was prepared at pH 3.5, and FeOOH II was formed by aging FeOOH I at pH 13. The percentages of surface amorphous FeOOH reduced from 70% to 30% after aging. The FeOOH II catalyst presented a higher reactivity toward H2O2 but lower stoichiometric efficiency in oxidizing benzoic acid than FeOOH I, similar to the result of the commercial goethite. Therefore, it is concluded that the crystalline property significantly affects the performance of catalytic oxidation. [Copyright &y& Elsevier]