Addition Of Magnetite Nanoparticles Research Articles

Enhancing reductive dechlorination of trichloroethylene in bioelectrochemical systems with conductive materials

The incorporation of conductive materials to enhance electron transfer in bioelectrochemical systems (BES) is considered a promising approach. However, the specific effects and mechanisms of these materials on trichloroethylene (TCE) reductive dechlorination in BES remains are not fully understood. This study investigated the use of magnetite nanoparticles (MNP) and biochars (BC) as coatings on biocathodes for TCE reduction. Results demonstrated that the average dechlorination rates of MNP-Biocathode (122.89 μM Cl·d−1) and BC-Biocathode (102.88 μM Cl·d−1) were greatly higher than that of Biocathode (78.17 μM Cl·d−1). Based on MATLAB calculation, the dechlorination rate exhibited a more significantly increase in TCE-to-DCE step than the other dechlorination steps. Microbial community analyses revealed an increase in the relative abundance of electroactive and dechlorinating populations (e.g., Pseudomonas, Geobacter, and Desulfovibrio) in MNP-Biocathode and BC-Biocathode. Functional gene analysis via RT-qPCR showed the expression of dehalogenase (RDase) and direct electron transfer (DET) related genes was upregulated with the addition of MNP and BC. These findings suggest that conductive materials might accelerate reductive dechlorination by enhancing DET. The difference of physicochemical characteristics (e.g. particle size and specific surface area), electron transfer enhancement mechanism between MNP and BC as well as the reduction of Fe(III) by hydrogen may explain the superior dechlorination rate observed with MNP-Biocathode.

Adhesion of Escherichia coli and Lactobacillus fermentum to Films and Electrospun Fibrous Scaffolds from Composites of Poly(3-hydroxybutyrate) with Magnetic Nanoparticles in a Low-Frequency Magnetic Field.

The ability of materials to adhere bacteria on their surface is one of the most important aspects of their development and application in bioengineering. In this work, the effect of the properties of films and electrospun scaffolds made of composite materials based on biosynthetic poly(3-hydroxybutyrate) (PHB) with the addition of magnetite nanoparticles (MNP) and their complex with graphene oxide (MNP/GO) on the adhesion of E. coli and L. fermentum under the influence of a low-frequency magnetic field and without it was investigated. The physicochemical properties (crystallinity; surface hydrophilicity) of the materials were investigated by X-ray structural analysis, differential scanning calorimetry and "drop deposition" methods, and their surface topography was studied by scanning electron and atomic force microscopy. Crystal violet staining made it possible to reveal differences in the surface charge value and to study the adhesion of bacteria to it. It was shown that the differences in physicochemical properties of materials and the manifestation of magnetoactive properties of materials have a multidirectional effect on the adhesion of model microorganisms. Compared to pure PHB, the adhesion of E. coli to PHB-MNP/GO, and for L. fermentum to both composite materials, was higher. In the magnetic field, the adhesion of E. coli increased markedly compared to PHB-MNP/GO, whereas the effect on the adhesion of L. fermentum was reversed and was only evident in samples with PHB-MNP. Thus, the resultant factors enhancing and impairing the substrate binding of Gram-negative E. coli and Gram-positive L. fermentum turned out to be multidirectional, as they probably have different sensitivity to them. The results obtained will allow for the development of materials with externally controlled adhesion of bacteria to them for biotechnology and medicine.

Polyaniline‐co‐polyindole functionalized magnetic porous carbon derived from MIL‐53(Fe) for separation/enrichment of nitrophenols pollutants before determination with high‐performance liquid chromatography‐ultraviolet detection

Herein, a novel polyaniline-co-polyindole functionalized magnetic porous carbon derived from MIL-53(Fe) was prepared and employed as an excellent nano-adsorbent to preconcentrate trace amounts of nitro-phenols in water and wastewater samples. Briefly, magnetic MIL-53(Fe) was synthesized by the addition of magnetite nanoparticles, terephthalic acid, and FeCl3 to the reaction medium. The magnetic MIL-53(Fe) was pyrolyzed under nitrogen protection to obtain a magnetic porous carbon nanocomposite, and finally, the nanomaterial was functionalized with polyaniline-co-polyindole via oxidation polymerization. The obtained nano-adsorbent was characterized via X-ray diffraction, Fourier-transform infrared spectroscopy, vibrating sample magnetometry, and transmission and scanning electron microscopies. After that, the fabricated nano-material was utilized as an excellent nano-adsorbent for the preconcentration of trace nitro-phenols (2-nitrophenol, 4-nitrophenol, and 2,4-dinitrophenol) in environmental water, and wastewater samples. The detection limits were obtained from 0.1 to 0.15μg/L after performing the optimization process. The new method was in the range of 0.4-300μg/L. The proposed method exhibited a good precision from 3.2% to 9.6% for within-day assay, and 5.2%-13.2% for between-day assay at three concentration levels (1, 50, and 250μg/L). Eventually, this method was utilized to preconcentrate/determine the target analytes in three water, and wastewater samples, satisfactory (relative standard deviations, 5.4%-9.3%; relative recovery, 88%-109%).

BIOGENIC AND ANTHROPOGENIC MAGNETIC NANOPARTICLES IN THE PHLOEM SIEVE TUBES OF PLANTS

The samples of leaves and roots of Nicotiana tabacum, the stems and tubers of Solanum tuberosum and the stems of pea Pisum sativum were examined by scanning probe microscopy in atomic force and magnetic force modes after cultivation without and with addition of magnetite nanoparticles in soil. Chains of both biogenic and anthropogenic magnetic nanoparticles are detected in the wall of the phloem sieve tubes i.e., the vascular tissue of plants. Such a localization of biogenic magnetic nanoparticles supports the idea that the chains of magnetic nanoparticles in different organs of plants have common metabolic functions. Stray gradient magnetic fields about several thousand Oe, which are created by chains of both biogenic and anthropogenic magnetic nanoparticles, can significantly affect the metabolic processes through the influence on mass transfer of vesicles, granules, organelles and other components. In view of the results of this investigation, both BMNs and anthropogenic magnetite nanoparticles chains can significantly affect the processes of mass transfer of vesicles, organelles, structural elements of the membrane and others components because they create stray magnetic fields and gradient magnetic forces.

Electrochemical paper-based analytical devices containing magnetite nanoparticles for the determination of vitamins B2 and B6

Disposable electrochemical paper-based analytical devices were developed from a conductive ink using graphite powder, automotive varnish and magnetite nanoparticles. The addition of magnetite nanoparticles in the conductive ink improved the sensitivity of the analytical devices. The devices were applied in the quantification of vitamins B2 (VB2) and B6 (VB6) in commercial dietary supplements. The characterization of the analytical devices was carried out by microscopy and electrochemical techniques. Square wave voltammetry (SWV) was used to study the electrochemical behavior of the vitamins and the experimental parameters were optimized (pH, supporting electrolyte and SWV parameters). The calibration plot for VB2 (−484 mV vs. graphite) was obtained in Britton-Robinson buffer (pH 2.0) in the range of 2.0 to 20.0 μmol L−1 with a detection limit of 0.25 µmol L−1. Similarly, for the VB6 (+675 mV vs. graphite), the calibration plot was obtained in McIlvaine buffer (pH 4.0) in the range of 0.2 to 2.0 mmol L−1 with a detection limit of 29.5 µmol L−1. The analytical devices were employed to determine VB2 and VB6 levels in B-complex supplements (capsules and sublingual liquid) and the results were compared with those provided by fluorescence spectrometry. The statistical analysis showed no considerable difference in terms of the precision and accuracy of the data obtained by both methods.

Improve direct injection compression ignition engine behavior using magnetite nano-fuel and hydrogen induction: a dual fuel approach

ABSTRACT Direct injection compression ignition (DICI) engine behavior can be improved by adding metallic nanoparticles as an additive in a pilot fuel. However, the effects of metallic-based additive in a dual-fuel engine with hydrogen as a secondary fuel are not well known. Therefore, the present work investigates the effects of magnetite nanoparticles (nano-metallic additive) and hydrogen induction (secondary fuel) on the behavior of an employed dual fuel DICI engine fueled with chicken fat biodiesel (CFB) blend. The magnetite nano-fuels were prepared by an ultrasonication process through suspending magnetite nanoparticles in a CFB30 blend (30% chicken fat biodiesel + 70% pure diesel) in quantities of 50, 100, and 150 ppm. All experiments were executed at a constant speed of 1500 rpm, and different brake power (BP) of 0 kW, 0.85 kW, 1.71 kW, 2.56 kW, and 3.42 kW. Results showed that the neat CFB30 blend gave trivial lower BTE compared to diesel. However, CFB30 blend lessened the smoke by 11.65%, UHC by 12%, and CO by 0.038 (% vol.), but it increased the NOx emission by 25%. The addition of magnetite nanoparticles (100 ppm) in a CFB30 blend demonstrated an enhancement in BTE by 7.49% and reduction in BSFC by 22.86 and NOx by 15.72%, besides nanoparticles inclusion further declined the smoke by 15.64%, UHC by 22.27%, and CO by 0.119 (% vol.) corresponding to neat CFB30 blend. Ultimately, 10 lpm of hydrogen injection further increased the BTE by 5.08% and lessened the BSFC by 14.17%, smoke by 11.57%, UHC by 14.7%, and CO by 0.037 (%vol.), although increased the NOx emission slightly. From the investigational results, it is concluded that magnetite nanoparticles in CFB30 fuel along with 10 lpm hydrogen demonstrate an overall improvement in DICI engine behavior.

Accelerated anaerobic biodecolorization of sulfonated azo dyes by magnetite nanoparticles as potential electron transfer mediators

Anaerobic decolorization of azo dyes has been evidenced to be an economical and effective pretreatment method, but its generally limited by the low decolorization efficiency, especially for biodecolorization sulfonated azo dyes. In this study, magnetite nanoparticles (MNPs) as a conductive material, was coupled into anaerobic system for enhancing decolorization of sulfonated azo dyes, i.e., methyl orange (MO), with technology feasibility and system stability emphasized. The results showed that the anaerobic decolorization capacity was significantly enhanced with addition of MNPs (at dose of 1 g/L), where the efficiencies of MO decolorization and aromatic amines formation were as high as 97.28 ± 0.78 % and 99.44 ± 0.25%, respectively. In addition, both electron transport system activity and sludge conductivity were also significantly improved, suggesting that a direct extracellular electron transfer had been successfully established via MNPs as RMs. Under continuous-flow experiments, addition of MNPs not only improved anaerobic system resistance environmental stress (e.g., high MO concentration, low hydraulic retention time and low co-substance concentration) but also accelerated sludge granulation. The relative abundance of functional species related to dissimilatory iron reduction and MO biodegradation were also enriched under MNPs stimulation. The observed long-term stable performance suggests the full-scale application potential of this coupled system for treatment of wastewater containing sulfonated azo dyes.

Modeling cobalt ion adsorption with synthesized magnetite bentonite (SMB) nano-absorbent: by CCD

Magnetic nanoparticles are very effective in removing heavy metals from wastewater that can be produced by adding to mineral adsorbents, a modified adsorbent with high adsorption properties. The addition of magnetite nanoparticles to bentonite increases the cationic adsorption power of bentonite. In this paper, the adsorption of cobalt ions on metal ions is investigated using synthesized magnetite bentonite nano-absorbent (SMB) (30-40 nm). First, the nano-absorbents were produced by co-precipitation and analyzed by Scanning electron microscope (SEM), X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FT-IR), then used as adsorbent. The experiments were designed and evaluated by design expert software. Optimal conditions were obtained by CCD model for metal ion adsorption (removal). The optimum amount of adsorption of Co 2+ ion from the solution was 95%.

Improving hydrogen and methane co-generation in cascading dark fermentation and anaerobic digestion: The effect of magnetite nanoparticles on microbial electron transfer and syntrophism

The efficiency of microbial electron transfer is fundamental for determining the performance of fermentative hydrogen/methane production. To facilitate microbial electron transfer, conductive magnetite nanoparticles (MNPs) were added into a cascading dark fermentation and anaerobic digestion system that was inoculated with Enterobacter aerogenes ZJU1 and methanogenic activated sludge (MAS), respectively. During the hydrogen-producing stage, the ratio of NADH/NAD+ and the activities of hydrogenase and electron transport system (ETS) of E. aerogenes ZJU1 were all increased by dosing 200 mg/L MNPs, which was conducive to hydrogen production through the NADH-dependent pathway. In the presence of 200 mg/L MNPs, hydrogen production increased by 21.1%, while subsequent methane production improved by 22.9%. Electrochemical analysis demonstrated the improvement in extracellular electron transfer capacity of MAS after adding MNPs, which can be ascribed to the contribution of MNPs and electrochemically active extracellular polymeric substances (EPS) induced by MNPs, such as humic acid-like and fulvic acid-like substances. Bacteria Syntrophomonas and Archaea Methanosarcina were the dominating enriched syntrophic partners, and the expression of functional genes involved in CO2 reduction to methane pathway was found to increase. Therefore, a more efficient fermentative hydrogen and methane co-production system was established by improving microbial electron transfer with the addition of MNPs.

Reduced graphene oxide decorated with magnetite nanoparticles enhance biomethane enrichment

The addition of magnetite nanoparticles (MNPs), reduced graphene oxide (rGO), and reduced graphene oxide decorated with magnetite nanoparticles (rGO-MNPs) was evaluated during biomethane enrichment process. rGO-MNPs presented the highest beneficial impact on the hydrogenotrophic assays with an improvement of 47 % in CH4 production. The improvement was linked to the increase of the electron shuttling capacity (ESC) by rGO-MNPs addition, which boosted the hydrogenotrophic activity of microorganisms, to the rGO and rGO-MNPs, which served as reservoirs of hydrogen, improving H⁠2 transport from the gas to the liquid phase, and to the iron ions released, which acted as a dietary supply for microorganisms. Raman and XRD confirmed a greater disorder and lower crystallinity of rGO-MNPs after the hydrogenotrophic assays, with a lower effect at a nanoparticle concentration of 50 mg/L. Moreover, FTIR analysis indicated that rGO-MNPs were oxidized during the hydrogenotrophic tests. This study highlights the advantages of adding rGO-MNPs as a magnetic nanocomposite. Furthermore, rGO-MNPs can be easily recovered, minimizing their release to the environment.

Hybrid Process of Electrochemistry with Magnetite Nanoparticles for Treatment of Turbid Water

Magnetic nanoparticles are now being investigated widely in field of water treatment. The aim of this study was to evaluate the feasibility of electrocoagulation process combined with addition of magnetite nanoparticles as a turbidity removal process. Bentonite was used as source of turbidity for the synthetic turbid water. Experiments were conducted in a bench scales electrocoagulation reactor where voltage was applied across a perforated plate of aluminum as anode, and iron mesh as cathode. Commercial grade of magnetite (Fe3O4) with an average nanoparticle size of 50 nm was used. The effect of some factors such as initial pH of the solution (5-9), current density (5-25 mA/cm2), and magnetite dosage (0.4-2.5 gm) on the efficiency of the process were studied. The residual turbidity obtained by using electrocoagulation process alone was (7.47 NTU) from initial turbidity of (200 NU) at constant conditions of pH 6, current density 15 mA/cm2 and electrolysis time 20 min. While under these same conditions the combined electrocoagulation + magnetite process with the added (1.4 gm) of magnetite and under the same operating conditions the residual turbidity was (4.34 NTU), which indicate that the magnetite nanoparticles enhanced the electrocoagulation process.

Magnetite nanoparticles enhance the bioelectrochemical treatment of municipal sewage by facilitating the syntrophic oxidation of volatile fatty acids

AbstractBACKGROUNDMicrobial electrochemical technologies (METs) represent a novel platform to harvest the energy trapped in municipal wastewater. At the anode of METs, electro‐active bacteria (EAB) anaerobically oxidize wastewater constituents using the electrode as the terminal electron acceptor and, by so doing, generate an electric current. To convert complex wastewater constituents into electricity, EAB must not only establish syntrophic relationships with other members of the microbial community, but also compete with methanogens for consumption of hydrogen and acetate. Here, we examined the addition of magnetite nanoparticles (NPs) (250 mg Fe L−1) as a novel strategy to manipulate such metabolic interactions and in turn maximize the efficiency of wastewater treatment and the yield of electric current generation.RESULTSBatch experiments carried out either in the presence of a mixture of volatile fatty acids or of a synthetic sewage demonstrated that magnetite addition accelerate the rate of electrogenic oxidation of specific compounds, particularly propionate (up to 120%), an intermediate which frequently accumulates during anaerobic treatment processes, while correspondingly enhancing electric current generation (up to 90%), and diminishing the rate of competing methane generation (up to 50%). Notably, the composition of the microbial community was not substantially affected by the presence of magnetite nanoparticles, possibly suggesting that these latter facilitated extracellular electron transfer mechanisms (among microbes and with the electrode), rather than enriching conditions for specific microorganisms.CONCLUSIONThe addition of magnetite NPs may represent a practical strategy to kick‐start a bioelectrochemical system designed for wastewater treatment and improve the effectiveness of electrogenic substrate oxidation processes. © 2019 Society of Chemical Industry

Increasing activated sludge aggregation by magnetite nanoparticles addition.

The behavior of mixed samples (activated sludge and wastewater) was investigated after the addition of magnetite nanoparticles (NP-magnetite) in jar tests, with objective to increase the aggregation of sludge and improve its settleability, aiming for future application in granular sequencing batch reactors. The NP-magnetite was synthesized by the method of ion co-precipitation of Fe2+ and Fe3+ and characterized. The process of sludge sedimentation was evaluated for two different experimental strategies, with NP-magnetite concentrations between 25 and 150 mg L-1. The concentration of 75 mg L-1 was the most favorable to process, as evidenced by sludge volumetric index and density. The results presented indicate that the addition of nanoparticles has the potential to improve aerobic granular systems, increasing the settleability of seed sludge.

Electrical properties of epoxy nanocomposites containing Fe3O4 nanoparticles and Fe3O4 nanoparticles deposited on the surface of electrochemically exfoliated and oxidized graphite

Electrical conductivity, electromagnetic interference shielding and microwave absorption properties of epoxy composites containing magnetite nanoparticles and modified electrochemically exfoliated graphite (mEEG) were described in this work. Different nanoparticles were prepared by co-precipitation method and electrochemical exfoliation. Structure of synthesized Fe3O4 NPs and graphite based nanostructures was described in detail. The X-ray diffractometry, Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy as well as scanning and transmission electron microscopy were used in order to characterize samples. Fe3O4 nanoparticles with average crystallite size equal to 8.45 nm and 8.30 nm were obtained in highly agglomerated structure and on the surface of mEEG. Reconstruction of graphite structure during precipitation of Fe3O4 on the surface of oxidized, exfoliated graphite was observed. In order to describe dispersion of AC electrical conductivity, correlated barrier hopping model was used. It was noticed, that addition of nanoparticles changes the values of hopping energy and activation energy as well as electromagnetic interference shielding and microwave absorption properties. Epoxy composite containing Fe3O4 NPs had the highest value of activation energy of electrical conductivity. It was shown, that the addition of magnetite nanoparticles has also improved electromagnetic interference shielding and microwave absorption properties of epoxy resin.

Stimulatory Effect of Magnetite Nanoparticles on a Highly Enriched Butyrate-Oxidizing Consortium.

Syntrophic oxidation of butyrate is catabolized by a few bacteria specialists in the presence of methanogens. In the present study, a highly enriched butyrate-oxidizing consortium was obtained from a wetland sediment in Tibetan Plateau. During continuous transfers of the enrichment, the addition of magnetite nanoparticles (nanoFe3O4) consistently enhanced butyrate oxidation and CH4 production. Molecular analysis revealed that all bacterial sequences from the consortium belonged to Syntrophomonas with the closest relative of Syntrophomonas wolfei and 96% of the archaeal sequences were related to Methanobacteria with the remaining sequences to Methanocella. Addition of graphite and carbon nanotubes for a replacement of nanoFe3O4 caused the similar stimulatory effect. Silica coating of nanoFe3O4 surface, however, completely eliminated the stimulatory effect. The control experiment with axenic cultivation of a Syntrophomonas strain and two methanogen strains showed no effect by nanoFe3O4. Together, the results in the present study support that syntrophic oxidation of butyrate is likely facilitated by direct interspecies electron transfer in the presence of conductive nanomaterials.

Influence of magnetite nanoparticles on electrical, magnetic and thermal properties of chitin/cashew gum biopolymer nanocomposites

In this study, we report the preparation of polymer blend nanocomposites based on chitin (CT)/cashew gum (CG) with various contents of magnetite nanoparticles (Fe3O4). The fabricated nanocomposites were characterised by FT infrared (FTIR), X‐ray diffraction (XRD), high‐resolution transmission electron microscopy (HRTEM), magnetic property (vibrating sample magnetometry (VSM)), differential scanning calorimetry (DSC), thermogravimetry (TGA) and impedance analyser. FTIR study revealed the characteristic absorption and shifts of peaks of the blend matrix, the shifts being attributed to the intermolecular interaction of Fe3O4 nanoparticles with CT/CG segments. The amorphous domain of the blend decreased with an increase in the concentration of nanoparticles was observed from XRD analysis. The HRTEM images showed the uniform arrangement of nanoparticles within the CT/CG network. VSM studies showed the ferromagnetic nature of the blend composite with an increasing saturation of magnetism with super‐paramagnetic behavior. DSC and TGA results revealed that the glass transition temperature and thermal stability of the composites were increased by the addition of magnetite nanoparticles. AC and dielectric properties were much improved in the entire range of frequencies due to the interaction with Fe3O4 nanoparticles. The role of nanoparticles on mechanical properties has been carefully studied. The tensile strength and hardness of magnetite filled nanocomposites become significantly higher in comparison to unfilled compounds and the nanocomposite with 10 wt. % of nanoparticles showed the maximum tensile strength. POLYM. COMPOS., 39:E540–E549, 2018. © 2017 Society of Plastics Engineers

A novel bioelectrode and anaerobic sludge coupled system for p-ClNB degradation by magnetite nanoparticles addition.

A novel laboratory-scale bioelectrode and anaerobic sludge coupled system was established for the enhancement of p-chloronitrobenzenes (p-ClNB) reductive transformation with addition of magnetite nanoparticles. In this coupled system, the bioelectrodes were supplied with a voltage of 0.8V and the amount of magnetite nanoparticles was set at 7.4mL/400mL. Results showed that high p-ClNB transformation rate of 0.284h-1 and high p-chloroaniline (p-ClAn) dechlorination rate of 0.082h-1 were achieved in the coupled system at p-ClNB initial concentration of 30mgL-1, and p-ClAn is one of the reductive products of p-ClNB. The cyclic voltammetry curve showed that when the potential was -1000mV, the magnetite-biocathode current was about 10.7 times of the abiotic cathode. Also, a shift in the reductive peak potential and a dramatic increase in reductive peak current were observed. These findings suggest that magnetite nanoparticles could enhance the electrocatalytic activity and may act as electron conduits between microorganisms or between electrodes and microorganisms to promote the extracellular electron transfer.

Magnetic chitosan grafted (alkyl acrylate) composite particles: Synthesis, characterization and evaluation as adsorbents

An efficient process for preparing a series of magnetic chitosan grafted (alkyl acrylate) composite particles as novel adsorbent materials has been proposed. Magnetite nanoparticles (Fe3O4) were produced by co-precipitation. Modified chitosan (CSg) bearing surface vinyl groups was synthesized by glycidyl methacrylate coupling in acidic aqueous solution through an epoxide ring opening mechanism. The magnetic chitosan grafted (alkyl acrylate) composites were prepared by radical copolymerization of butyl acrylate (BA), butyl methacrylate (BMA) or hexyl acrylate (HA) with ethylene glycol dimethacrylate (EGDMA) onto the modified chitosan vinyl groups, with addition of magnetite nanoparticles in suspension. The prepared particles were characterized by TEM, SEM, XRD, VSM and FTIR. Adsorption batch experiments on the newly synthesized composites were conducted using Ni(II) ions in aqueous solutions. The variables that influence the sorption capacity, namely the solution pH, initial metal ion concentration, sorbent mass, adsorption time and temperature have been investigated. The adsorption kinetics was analyzed by fitting the data into the following models: pseudo-first-order, pseudo-second-order and intraparticle diffusion. The Langmuir, Freundlich and Dubinin–Radushkevich models were used to fit the adsorption isotherms. The proven high stability and recovery capacity of the composite particles suggest their potential use for Ni(II) ions removal from wastewater by using magnetically aided adsorption technology.

Magnetite nanoparticles facilitate methane production from ethanol via acting as electron acceptors.

Potential for interspecies hydrogen transfer within paddy soil enrichments obtained via addition of magnetite nanoparticles and ethanol (named as PEM) was investigated. To do this, PEM derived from rice field of Hangzhou (named as PEM-HZ) was employed, because it offered the best methane production performance. Methane production and Fe (III) reduction proceeded in parallel in the presence of magnetite. Inhibition experiments with 2-bromoethane sulfonate (BES) or phosphate showed that interspecies hydrogen transfer and Fe (III) reduction also occurred in methane production from ethanol. 16S rRNA-based Illumina sequencing results showed that Dechloromonas, Thauera, Desulfovibrio and Clostridium were the dominant putative Fe (III) -reducers, and that hydrogenotrophic Methanobacterium accounted for about 88% of the total archaeal community. These results indicated that magnetite nanoparticles that acted as electron acceptor could facilitate rapid oxidation of ethanol by members of the Fe (III) -reducers in PEM-HZ and establishment of the syntrophic relationship of Fe (III) -reducers with Methanobacterium via interspecies hydrogen transfer. Our results could offer a model to understand the microbial interaction with magnetite from a novel angle during methanogenesis.

Determination of Triacetone Triperoxide with a N,N-Dimethyl-p-phenylenediamine Sensor on Nafion Using Fe3O4 Magnetic Nanoparticles

The explosive triacetone triperoxide (TATP) can be easily manufactured from readily accessible reagents and is extremely difficult to detect, owing to the lack of UV absorbance, fluorescence, or facile ionization. The developed method is based on the acidic hydrolysis of TATP into H2O2, pH adjustment to 3.6, and the addition of magnetite nanoparticles (Fe3O4 MNPs) to the medium to produce hydroxyl radicals from H2O2, owing to the peroxidase-like activity of MNPs. The formed radicals converted the N,N-dimethyl-p-phenylenediamine (DMPD) probe to the colored DMPD(+) radical cation, the optical absorbance of which was measured at a wavelength of 554 nm. The molar absorptivity (ε) of the method for TATP was 21.06 × 10(3) L mol(-1) cm(-1). The colored DMPD(+) product in solution could be completely retained on a cation-exchanger Nafion membrane, constituting a colorimetric sensor for TATP and increasing the analytical sensitivity. The proposed method did not respond to a number of hand luggage items like detergent, sweetener, sugar, acetylsalicylic acid (aspirin), and paracetamol-caffeine-based analgesic drugs. On the other hand, TATP could be almost quantitatively recovered from a household detergent and sweetener that can be used as camouflage for the analyte. Neither common soil and groundwater ions (e.g., Ca(2+), Mg(2+), K(+), Cl(-), SO4(2-), and NO3(-)) at 100-fold ratios nor nitro-explosives of trinitrotoluene (TNT), hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX), and pentaerythritol tetranitrate (PETN) at 10-fold amounts interfered with the proposed assay. The method was statistically validated against the standard GC/MS reference method.