Magnetite-platinum nanoparticles-modified glassy carbon electrode as electrochemical detector for nitrophenol isomers

A glassy carbon electrode was modified with magnetite and platinum nanoparticles stabilized with 3-n-propyl-4-picoline silsesquioxane chloride. This chemically-modified electrode is proposed for the first time for the individual or simultaneous electrochemical detection of nitrophenol isomers. Nanoparticles act as catalysts and also increase the surface area. The polymer stabilizes the particles and provides the electrochemical separation of isomers. Under optimized conditions, the reduction peak currents, obtained by differential-pulse voltammetry, of 2-, 3-, and 4-nitrophenol increased linearly with increases in their concentration in the range of 0.1-1.5μmolL^-1. In individual analysis, the detection limits were 33.7nmolL^-1, 45.3nmolL^-1 and 48.2nmolL^-1, respectively. Also, simultaneous analysis was possible for 2-, and 4-nitrophenol. In this case, the separation of the peak potentials was 0.138V and the detection limits were 69.6nmolL^-1 and 58.0nmolL^-1, respectively. These analytical figures of merit evidence the outstanding performance of the modified electrode, which was also successfully applied to the individual determination of isomers in environmental and biological samples. The magnetite and platinum nanoparticles modified glassy carbon electrode was able to detect nitrophenol isomers at the ppm level in rain water and human urine samples.

Electrochemical regeneration of a reduced graphene oxide/magnetite composite adsorbent loaded with methylene blue

In this work, two different reduced graphene oxide/iron oxide (rGO-IO) nanocomposites with different iron oxide loadings were fabricated using a one-step solvothermal method. The structure, properties and applications of the synthesized nanocomposites were evaluated with Raman spectroscopy, attenuated total reflectance Fourier transform infrared spectroscopy, thermogravimetric analysis, X-ray diffraction, electron microscopy, and energy-dispersive X-ray spectroscopy. The iron oxide is in the form of magnetite (Fe₃O₄), so that the resultant adsorbent can readily be separated from the treated water using a magnetic field. The ability of the nanocomposites to remove methylene blue (MB) from water by adsorption was investigated. The highest adsorptive capacity observed was 39 mg g^-1, for the composite containing 60 wt% iron oxide. The adsorptive capacity of the rGO-IO decreased to 26 mg g^-1 when the mass fraction of iron oxide was increased to 75 wt%. Electrochemical regeneration of MB loaded rGO-IO was also investigated. The electrochemical regeneration was found to be rapid and with low electrical energy consumption relative to conventional adsorbents, due to the high electrical conductivity and nonporous surface of the rGO. A regeneration efficiency of 100% was obtained after 30 min of electrochemical treatment using a 2 mm thick bed of rGO-IO loaded with 39 mg g^-1 MB, using a current density of 10 mA cm^-2. Multiple adsorption-electrochemical regeneration cycles demonstrated that the surface of the rGO was modified leading to increase in the adsorptive capacity to around 80 mg g^-1 after the second regeneration cycle. The morphology of the rGO was observed to change significantly after electrochemical regeneration, suggesting that the rGO based adsorbent materials could only be used for a few cycles.

Effect of microscale ZVI/magnetite on methane production and bioavailability of heavy metals during anaerobic digestion of diluted pig manure

Low methane production and high levels of heavy metal in pig slurries limit the feasibility of anaerobic digestion of pig manure. In this study, changes in the methane production and bioavailability of heavy metals in the anaerobic digestion of diluted pig manure were evaluated using single and combined action of microscale zero-valence iron (ZVI) and magnetite. After 30 days of anaerobic digestion, the methane yield ranged from 246.9 to 334.5 mL/g VS added, which increased by 20-26% in the group added with microscale ZVI and/or magnetite relative to that in the control group. Results of the first-order kinetic model revealed that addition of microscale ZVI and/or magnetite increased the biogas production potential, rather than the biogas production rate constant. These treatments also changed the distribution of chemical fractions for heavy metal. The addition of ZVI decreased the bioavailability of Cu and Zn in the solid digested residues. Moreover, a better performance was observed in the combined action of microscale ZVI and magnetite, and the ZVI anaerobic corrosion end-product, magnetite, might help enhance methane production through direct interspecies electron transfer in ZVI-anaerobic digestion process.

Characterization of ceramic ware fragments from Aizanoi-Turkey by micro Raman, XRPD and SEM-EDX spectrometry

Ceramic fragments from the antique city of Aizanoi, Turkey were investigated by micro Raman spectrometry in conjunction with XRPD and SEM-EDX analyses. Some basic physical characteristics of the ceramic samples were also investigated. Illite and muscovite were determined as the main clay types in the ceramic fragments. Clay used in the production of ceramic wares was found to be calcareous in most of the samples. No high temperature clay minerals were detected in the ceramics. All ceramic fragments were found to be rich in iron content. Hematite and magnetite were identified to be the principle coloring agents in the investigated samples. The ceramics with hematite content were assessed to be fired in an oxygen rich atmosphere whereas the samples having magnetite were proposed to be fired in an inadequately ventilated kiln. Based on the presence of calcite, dolomite and TiO₂ in the crystal form of anatase in the samples, firing temperature during production was estimated to be below 750°C.

Enhanced heterogeneous photo-Fenton process modified by magnetite and EDDS: BPA degradation

In this research, magnetite and ethylenediamine-N,N'-disuccinic acid (EDDS) are used in a heterogeneous photo-Fenton system in order to find a new way to remove organic contaminants from water. Influence of different parameters including magnetite dosage, EDDS concentration, H₂O₂ concentration, and pH value were evaluated. The effect of different radical species including HO^· and HO₂^·/O₂^·- was investigated by addition of different scavengers into the system. The addition of EDDS improved the heterogeneous photo-Fenton degradation of bisphenol A (BPA) through the formation of photochemically efficient Fe-EDDS complex. This effect is dependent on the H₂O₂ and EDDS concentrations and pH value. The high performance observed at pH 6.2 could be explained by the ability of O₂^·- to generate Fe(II) from Fe(III) species reduction. GC-MS analysis suggested that the cleavage of the two benzene rings is the first degradation step followed by oxidation leading to the formation of the benzene derivatives. Then, the benzene ring was opened due to the attack of HO^· radicals producing short-chain organic compounds of low molecular weight like glycerol and ethylene glycol. These findings regarding the capability of EDDS/magnetite system to promote heterogeneous photo-Fenton oxidation have important practical implications for water treatment technologies.

Selective and sensitive fluorimetric determination of carbendazim in apple and orange after preconcentration with magnetite-molecularly imprinted polymer

In this study, magnetite-molecularly imprinted polymer has been used for the first time as selective adsorbent before the fluorimetric determination of carbendazim. Adsorption capacity of the magnetite-molecularly imprinted polymer was found to be 2.31±0.63mgg^-1 (n=3). Limit of detection (LOD) and limit of quantification (LOQ) of the method were found to be 2.3 and 7.8μgL^-1, respectively. Calibration graph was linear in the range of 10-1000μgL^-1. Rapidity is an important advantage of the method where re-binding and recovery processes of carbendazim can be completed within an hour. The same imprinted polymer can be used for the determination of carbendazim without any capacity loss repeatedly for at least ten times. Proposed method has been successfully applied to determine carbendazim residues in apple and orange, where the recoveries of the spiked samples were found to be in the range of 95.7-103%. Characterization of the adsorbent and the effects of some potential interferences were also evaluated. With the reasonably high capacity and reusability of the adsorbent, dynamic calibration range, rapidity, simplicity, cost-effectiveness and with suitable LOD and LOQ, the proposed method is an ideal method for the determination of carbendazim.

Synthesis and characterization of magnetic chitosan microspheres as low-density and low-biotoxicity adsorbents for lake restoration

We propose a novel magnetic adsorbent for optimal Phosphorus (P) removal from the upper sediment layers. For this aim, magnetic chitosan microparticles were prepared using a reverse-phase suspension cross-linking technique. The resulting particles and suspensions were characterized using scanning electron microscopy, X-ray powder diffraction, Fourier transform infrared spectroscopy, magnetometry, thermogravimetric analysis, electrophoretic mobility and turbidity measurements. The hybrids are multicore particles consisting of well dispersed magnetite nanoparticles (approx. 10% w/w) homogeneously distributed within the biopolymer matrix. These microparticles can be easily separated from the water column and sediment using magnetic field gradients. Their P adsorption capacity is evaluated in batch conditions resulting in a maximum P adsorption capacity of M_L = 4.84 mg g^-1 at pH = 7. We demonstrate that these particles are excellent candidates to remove P from water column and also P mobile from the upper sediment layers due to two main reasons: they sediment slower and present lower potential toxicity (due to a their larger size) than conventional iron/iron oxide microparticles previously proposed for lake restoration.

The effect of arsenic chemical form and mixing regime on arsenic mass transfer from soil to magnetite

This study investigated the effect of chemical forms of arsenic (As) and soil-magnetite mixing regimes on As mass transfer in magnetite-amended soil. Two soil samples with different component ratios of As chemical forms were prepared. In the absence of magnetite, the amount of desorbable As was strongly dependent on the fraction of easily extractable As in soil. Contact of the soils with magnetite in a slurry phase significantly reduced soil As concentration for both soils. Changes in As concentrations in soil, magnetite, and water by the slurry phase contact were simulated using an As mass transfer model. The model parameters were determined independently for each process of As soil desorption and magnetite sorption. The experimentally measured As mass transfer from soil to magnetite was significantly greater than the simulation result. By sequential extraction, it was observed that the soil As concentration was significantly reduced not only for easily extractable As, but also for relatively strongly bound forms of As. Enclosing the magnetite in a dialysis bag substantially limited the As mass transfer from soil to magnetite. These results suggest that improving the mixture between Fe oxides and soils can facilitate the effectiveness of As stabilization using Fe oxides.

Ultrasound-assisted removal of Acid Red 17 using nanosized Fe3O4-loaded coffee waste hydrochar

The Fe₃O₄-loaded coffee waste hydrochar (Fe₃O₄-CHC) was synthesized using a simple precipitation method. The as-prepared adsorbent was characterized using scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET) and Fourier transform infrared spectroscopy (FT-IR). The EDX analysis indicated the presence of Fe in the structure of Fe₃O₄-CHC. The specific surface area of hydrochar increased from 17.2 to 34.7m²/g after loading of Fe₃O₄ nanoparticles onto it. The prepared Fe₃O₄-CHC was used for removal of Acid Red 17 (AR17) through ultrasound-assisted process. The decolorization efficiency decreased from 100 to 74% with the increase in initial dye concentration and from 100 to 91 and 85% in the presence of NaCl and Na₂SO₄, respectively. The synthesized Fe₃O₄-CHC exhibited good stability in the repeated adsorption-desorption cycles. The high correlation coefficient (R²=0.997) obtained from Langmuir model indicated that physical and monolayer adsorption of dye molecules occurred on the Fe₃O₄-CHC surface. Furthermore, the by-products generated through the degradation of AR17 was identified by gas chromatography-mass spectrometry analysis.

Cytotoxic effect of ferrimagnetic glass-ceramic nanocomposites on bone osteosarcoma cells

This work pointed out the anti-cancer effect of ferrimagnetic glass ceramic nanocomposites (CaO-ZnO-Fe₂O₃-SiO₂)_, which contain high amount of magnetite (∼60%), crystallite size <100nm, and different nucleating agents on bone cancer Saos-2 cells. The cell viability was inhibited by FH and FW to <50% and <25%, respectively, with/without magnetism, and both also reduced mitochondrial transmembrane potential (ΔYm), with/without magnetism (no influence of magnetism). Histone deacetylase (HDAC) activity was inhibited by FH, FW, and FHPNT, with/without magnetism. FHP3/magnetism resulted in HDAC inhibition. In absence of magnetism, FH and FW increased both necrotic and apoptotic cell death, while FW/magnetism induced late apoptosis. DNA fragmentation was increased by FH- and FW-treatment, with/without magnetism. At the same time, FW and FH/magnetism can efficiently induce the intrinsic apoptotic pathway in Saos-2 cells, whereas FW with/without magnetism and FH/magnetism enhanced cytochrome-C release. Similarly, caspase-7 activity was elevated by FH and FW, with/without magnetism. However, the presence of P₂O₅ in the composition of the nanocomposites inhibited their apoptotic properties and diminished their anti-cancer activity.

Magnetite recovery from copper tailings increases arsenic distribution in solution phase and uptake in native grass

Reprocessing magnetite-rich copper (Cu) tailings prompted a concern about arsenic (As) risks in seepage water and revegetated plants at Ernest Henry Cu Mine (EHM) in North Queensland, Australia, due to the closely coupled relationship between iron (Fe) minerals and As mobility. The magnetite removal alone significantly decreased the content of crystalline Fe minerals and the maximum arsenate (As(V)) sorption capacity of the resultant tailings. A glasshouse experiment with native grass Red Flinders (Iseilema Vaginiflorum) was conducted with the reprocessed (low magnetite (LM)) and original (high magnetite (HM)) tailings, which were amended with 5% sugarcane residue (SR) as a basal treatment in combination with 0, 1 and 5% pine-biochar (BC). The organic matter treatments and plant growth stimulated the formation of secondary Fe minerals. The amount of extractable amorphous Fe in the amended and revegetated HM tailings was significantly higher than those in the LM. Arsenic forms in the specifically sorbed and the sorbed by amorphous Fe oxides were significantly increased by the SR amendment in the LM tailings, but which were decreased in the HM, compared to the unamended tailings. Soluble As levels in the porewater of the LM under revegetation were significantly higher (300-1150 μg As L^-1) than those (up to 45-90 μg As L^-1) in HM tailings in the same treatment, which led to the higher As concentrations in the plants grown in the LM tailings. In particular, root As concentration (62-146 mg kg^-1) in the LM tailings was almost a magnitude higher than those (8-17 mg kg^-1) in the HM. The present results confirmed the initial expectation that the recovery of magnetite from the Cu tailings significantly elevated the risk of As solubility in the tailings by decreasing As sorption capacity and increasing soluble As levels. Thus, it would be beneficial to retain high contents of magnetite in the top layer (e.g., root zone) of the Cu tailings for managing As risk and revegetation in the future.

Influence of the bacterial growth phase on the magnetic properties of magnetosomes synthesized by Magnetospirillum gryphiswaldense

BACKGROUND

The magnetosome biosynthesis is a genetically controlled process but the physical properties of the magnetosomes can be slightly tuned by modifying the bacterial growth conditions.

METHODS

We designed two time-resolved experiments in which iron-starved bacteria at the mid-logarithmic phase are transferred to Fe-supplemented medium to induce the magnetosomes biogenesis along the exponential growth or at the stationary phase. We used flow cytometry to determine the cell concentration, transmission electron microscopy to image the magnetosomes, DC and AC magnetometry methods for the magnetic characterization, and X-ray absorption spectroscopy to analyze the magnetosome structure.

RESULTS

When the magnetosomes synthesis occurs during the exponential growth phase, they reach larger sizes and higher monodispersity, displaying a stoichiometric magnetite structure, as fingerprinted by the well defined Verwey temperature. On the contrary, the magnetosomes synthesized at the stationary phase reach smaller sizes and display a smeared Verwey transition, that suggests that these magnetosomes may deviate slightly from the perfect stoichiometry.

CONCLUSIONS

Magnetosomes magnetically closer to stoichiometric magnetite are obtained when bacteria start synthesizing them at the exponential growth phase rather than at the stationary phase.

GENERAL SIGNIFICANCE

The growth conditions influence the final properties of the biosynthesized magnetosomes. This article is part of a Special Issue entitled "Recent Advances in Bionanomaterials" Guest Editors: Dr. Marie-Louise Saboungi and Dr. Samuel D. Bader.

Release and cytotoxicity studies of magnetite/Ag/antibiotic nanoparticles: An interdependent relationship

Though the cytotoxic properties of magnetite nanoparticles (NPs) are rather well investigated and known to be dose dependent and rather low, surface functionalization can drastically change their properties. To determine whether the cytotoxicity of magnetite/Ag/antibiotic NPs may be associated, among other things, with iron, silver and antibiotic release, this study investigates the release profiles and cytotoxicity of magnetite/Ag/rifampicin and magnetite/Ag/doxycycline NPs compares it similar profiles from magnetite, magnetite/Ag NPs and antibiotics. It was established that the studied NPs released not only water-soluble substances, such as antibiotics, but also poorly-soluble ones, such as iron and silver. The deposition of silver on the magnetite surface promotes the release of iron by the formation of a galvanic couple. Antibiotic adsorbed on the magnetite/Ag surface plays a dual role in the galvanic corrosion processes: as a corrosion inhibitor for iron oxides and as a corrosion promoter for silver. Magnetite/Ag/rifampicin and magnetite/Ag/doxycycline. NPs were found to have greater cytotoxicity towards the HEK293T cell line than magnetite NPs. These results were attributed to the combined toxic action of the released iron, silver ions and antibiotics. Intensive and simultaneous release of the NP components caused cell stress and suppressed their growth.

Renewable hybrid nanocatalyst from magnetite and cellulose for treatment of textile effluents

A hybrid catalyst was prepared using cellulose nanofibrils and magnetite to degrade organic compounds. Cellulose nanofibrils were isolated by mechanical defibrillation producing a suspension used as a matrix for magnetite particles. The solution of nanofibrils and magnetite was dried and milled resulting in a catalyst with a 1:1 ratio of cellulose and magnetite that was chemically and physically characterized using light, scanning electron and transmission electron microscopies, specific surface area analysis, vibrating sample magnetometry, thermogravimetric analysis, Fourier transform infrared spectroscopy, X-ray diffraction, catalytic potential and degradation kinetics. Results showed good dispersion of the active phase, magnetite, in the mat of cellulosic nanofibrils. Leaching and re-use tests showed that catalytic activity was not lost over several cycles. The hybrid material produced was tested for degradation of methylene blue dye in Fenton-like reactions resulting in a potential catalyst for use in degradation of organic compounds.

Ultrasound irritation enhanced heterogeneous activation of peroxymonosulfate with Fe3O4 for degradation of azo dye

Magnetic Fe₃O₄ nanoparticles were synthesized and used as peroxymonosulfate (PMS) activator in the presence of ultrasound (US) irritation for azo dye degradation in this study. At pH 7.0 and temperature 298K, Fe₃O₄ nanoparticles were able to activate PMS under ultrasound irritation to produce sulfate radicals for acid orange 7 (AO7) removal in 30min. Higher catalysts dosage, neutral pH as well as optimum values of PMS dosage and ultrasound power favored the AO7 degradation. Fe₃O₄ displayed excellent stability and reusability in the US/PMS system. Both of the sulfate radicals and hydroxyl radicals were produced in the reaction and sulfate radicals were the dominant according to the scavenging tests and electron paramagnetic resonance (ESR) tests. The mechanisms of ultrasound irritation enhanced PMS activation in the presence of Fe₃O₄ were proposed based on the results and literatures.

Degradation of landfill leachate compounds by persulfate for groundwater remediation

In this study, batch and column experiments were conducted to evaluate the feasibility of using persulfate oxidation to treat groundwater contaminated by landfill leachate (CGW). In batch experiments, persulfate was compared with H₂O₂, and permanganate for oxidation of organic compounds in CGW. It was also compared with the potential of biodegradation for contaminant removal from CGW. Persulfate was observed to be superior to H₂O₂ and permanganate for degradation of total organic carbon (TOC) in the CGW. Conversely, biodegradation caused only partial removal of TOC in CGW. In contrast, persulfate caused complete degradation of the TOC in the CGW or aged CGW, showing no selectivity limitation to the contaminants. Magnetite (Fe₃O₄) enhanced degradation of leachate compounds in both CGW and aged CGW with limited increase in persulfate consumption and sulfate production. Under dynamic flow condition in 1-D column experiments, both biodegradation and persulfate oxidation of TOC were enhanced by Fe₃O₄. The enhancement, however, was significantly greater for persulfate oxidation. In both batch and column experiments, Fe₃O₄ by itself caused minimal consumption of persulfate and production of sulfate, indicating that magnetite is a good persulfate activator for treating CGW in heterogeneous systems The results of the study show that the persulfate-based in-situ chemical oxidation (ISCO) method has great potential to treat the groundwater contaminated by landfill leachate.

Layer-by-layer encapsulated nano-emulsion of ionic liquid loaded with functional material for extraction of Cd2+ ions from aqueous solutions

Ionic liquids can serve as an environmentally-friendly replacement for solvents in emulsions, therefore they are considered suitable to be used as an emulsified medium for various active materials one of which are extractors of metal ions. Increasing the extraction efficiency is considered to be one of the key objectives when working with such extraction systems. One way to improve the extraction efficiency is to increase the contact area between the extractant and the working ionic solution. This can be accomplished by creating a nano-emulsion of ionic liquid containing such an extractant. Since emulsification of ionic liquid is not always possible in the sample itself, there is a necessity of creating a stable emulsion that can be added externally and on demand to samples from which metal ions need to be extracted. We propose a method of fabrication of a highly-stable extractant-loaded ionic liquid-in-water nano-emulsion via a low-energy phase reversal emulsification followed by continuous layer-by-layer polyelectrolyte deposition process to encapsulate the nano-emulsion and enhance the emulsion stability. Such a multilayered stabilized nano-emulsion was tested for extraction of Cd²⁺ and Ca²⁺ ions in order to determine its extraction efficiency and selectivity. It was found to be effective in the extraction of Cd²⁺ ions with near 100% cadmium removal, as well as being selective since no Ca²⁺ ions were extracted. The encapsulated emulsion was removed from samples post-extraction using two methods - filtration and magnetic separation, both of which were shown to be viable under different circumstances - larger and mechanically stronger capsules could be removed by filtration, however magnetic separation worked better for both smaller and bigger capsules. The long-term stability of nano-emulsion was also tested being a very important characteristic for its proposed use: it was found to be highly stable after four months of storage time.

In vitro biocompatibility of a ferrimagnetic glass-ceramic for hyperthermia application

Ferrimagnetic glass-ceramics containing magnetite crystals were developed for hyperthermia applications of solid neoplastic tissue. The present work is focused on in vitro evaluation of the biocompatibility of these materials, before and after soaking in a simulated body fluid (SBF). X-ray diffraction, scanning electron microscopy, atomic absorption spectrophotometry, X-ray photoelectron spectrometry and pH measurements were employed in glass-ceramic characterisation. The free-radical mediated reactivity of the glass-ceramic was evaluated by Electron Paramagnetic Resonance (EPR) spin trapping. Cell adhesion and proliferation tests were carried out by using 3T3 murine fibroblasts. Cytotoxicity was performed by qualitative evaluation of human bone osteosarcoma cells U2OS cell line. The results show that almost two times more 3T3 cells proliferated on the samples pre-treated in SBF, compared with the untreated specimens. Moreover a decrease of confluence was observed at 48 and 72h for U2OS cells exposed to the untreated glass-ceramic, while the powder suspensions of glass-ceramic pre-treated in SBF did not influence the cell morphology up to 72h of exposition. The untreated glass-ceramic exhibited Fenton-like reactivity, as well as reactivity towards formate molecule. After pre-treatment with SBF the reactivity towards formate was completely suppressed. The concentration of iron released into the SBF solution was below 0.1ppm at 37°C, during one month of soaking. The different in vitro behaviour of the samples before and after SBF treatment has been correlated to the bioactive glass-ceramic surface modifications as detected by morphological, structural and compositional analyses.

Decrease of dissolved sulfide in sewage by powdered natural magnetite and hematite

Natural magnetite and hematite were explored to decrease sulfide in sewage, compared with iron salts (FeCl₃ and FeSO₄). A particle size of magnetite and hematite ranging from 45 to 60μm was used. The results showed that 40mgL^-1 of powdered magnetite and hematite addition decreased the sulfide in sewage by 79%and 70%, respectively. The achieved decrease of sulfide production capacities were 197.3, 210.6, 317.6 and 283.3mgSg^-1Fe for magnetite, hematite, FeCl₃ and FeSO₄ at the optimal dosage of 40mgL^-1, respectively. Magnetite and hematite provided a higher decrease of sulfide production since more iron ions are capable of being released from the solid phase, not because of adsorption capacity of per gram iron. Besides, the impact on pH and oxidation-reduction potential (ORP) of hematite addition was negligible; while magnetite addition resulted in slight increase of 0.3-0.5 on pH and 10-40mV on ORP. Powdered magnetite and hematite thus appear to be suitable for sulfide decrease in sewage, for their sparing solubility, sustained-release, long reactive time in sewage as well as cost-effectiveness, compared with iron salts. Further investigation over long time periods under practical conditions are needed to evaluate the possible settlement in sewers and unwanted (toxic) metal elements presenting as impurities.

CAPSULE ABSTRACT

Powdered magnetite and hematite were more cost-effective at only 30% costs of iron salts, such as FeCl₃ and FeSO₄ for decreasing sulfide production in sewage.

Magnetic Nanocomposites as Efficient Sorption Materials for Removing Dyes from Aqueous Solutions

Magnetic composite sorbents based on saponite clays with different content of magnetite (2-7 wt%.) were synthesized. The samples were analyzed by X-ray diffraction methods, and it was found that the Fe3O4 in composites is in the nanorange. It has been shown that the magnetic nanocomposites have more developed microporosity and mesoporosity compared to saponite clay. The sorption properties of magnetic nanocomposite sorbents were determined, and the results evidenced that their efficiency is significantly higher than the individual phases of the composite. It was shown that all waste composite magnetic sorbents are successfully removed from the water environment by magnetic separation.

A long-term study on the effect of magnetite supplementation in continuous anaerobic digestion of dairy effluent - Enhancement in process performance and stability

Interspecies electron transfer (IET) between microbial populations with different functions is critical to stable anaerobic digestion. This study, in an attempt to facilitate IET, investigated the effect of magnetite supplementation on the biomethanation of dairy effluent in continuous mode. The magnetite-added reactor (RM) was significantly more resistant and resilient to process imbalance than the reactor run without magnetite addition (RC). RC showed unstable performance with repeated process upsets, but its performance improved to be comparable to that of RM after applying magnetite supplementation. Magnetite was particularly effective in stabilizing a build-up of propionic acid and therefore improving the process robustness and reliability. The enhanced biomethanation in terms of productivity and stability was attributed to the facilitated direct IET (DIET) between exoelectrogens and methanogens via magnetite particles. Methanosaeta was the predominant methanogen group in the experimental reactors and likely played a key role in both DIET-mediated carbon dioxide-reducing and aceticlastic methanogenesis.

Lanthanide-Functionalized Hydrophilic Magnetic Hybrid Nanoparticles: Assembly, Magnetic Behaviour, and Photophysical Properties

The lanthanide-functionalized multifunctional hybrid nanoparticles combining the superparamagnetic core and the luminescent europium complex were successfully designed and assembled via layer-by-layer strategy in this work. It is noted that the hybrid nanoparticles were modified by a hydrophilic polymer polyethyleneimine (PEI) through hydrogen bonding which bestowed excellent hydrophilicity and biocompatibility on this material. A bright-red luminescence was observed by fluorescence microscopy, revealing that these magnetic-luminescent nanoparticles were both colloidally and chemically stable in PBS solution. Therefore, the nanocomposite with magnetic resonance response and fluorescence probe property is considered to be of great potential in multi-modal bioimaging and diagnostic applications.

Gd-DTPA Adsorption on Chitosan/Magnetite Nanocomposites

The synthesis of the chitosan/magnetite nanocomposites is presented. Composites were prepared by co-precipitation of iron(II) and iron(III) salts by aqueous ammonia in the 0.1 % chitosan solution. It was shown that magnetite synthesis in the chitosan medium does not affect the magnetite crystal structure. The thermal analysis data showed 4.6 % of mass concentration of chitosan in the hybrid chitosan/magnetite composite. In the concentration range of initial Gd-DTPA solution up to 0.4 mmol/L, addition of chitosan to magnetite increases the adsorption capacity and affinity to Gd-DTPA complex. The Langmuir and Freundlich adsorption models were applied to describe adsorption processes. Nanocomposites were characterized by scanning electron microscopy (SEM), differential thermal analysis (DTA), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and specific surface area determination (ASAP) methods.

Development of New Effective Sorbents Based on Nanomagnetite

Magnetic hybrid nanocomposite material based on the kraft lignin was prepared by the co-precipitating method. Kraft lignin was modified by iron nanooxide in order to enhance its sorption properties towards heavy metal ions. The composite material was characterized by physicochemical methods such as BET N2, ATR-FTIR, TGA, DSC, pHpzc, XRD and SEM. Its adsorption behaviour was studied using the batch mode by varying different parameters like pH, initial concentration of metal ions and shaking time as well as the presence of interfering ions. Adsorption of Cu(II), Cd(II) and Pb(II) ions from the aqueous solutions was studied in comparison with the commercial kraft lignin. The adsorption capacity and kinetic sorption characteristics of the composite material were determined.

Carboxymethyl chitosan-modified magnetic-cored dendrimer as an amphoteric adsorbent

Carboxymethyl chitosan-modified magnetic-cored dendrimers (CCMDs) were successfully synthesized in a three step method. The synthesized samples were characterized using X-ray diffraction, transmission electron microscopy, scanning electron microscopy, vibrating sample magnetometer, thermogravimetry analysis, zeta potential analyzer, X-ray photoelectron spectroscopy, surface area analysis, and Fourier transform infrared spectroscopy. The CCMD exhibited selective adsorption for anionic and cationic compounds at specific pH conditions. With the substitution of amino groups of MD with carboxymethyl chitosan moieties, the adsorption sites for cationic compounds were greatly increased. Since the adsorption onto CCMD was mainly electrostatic interaction, the adsorption of MB and MO was significantly affected by the pHs. The optimal adsorption pH values were 3 and 11 for MO and MB. The maximal adsorption of MO and MB on the CCMD at pH values of 3 and 11 were 20.85mgg(-1) and 96.31mgg(-1), respectively. Reuse of the CCMD as an adsorbent was experimentally tested through adsorption and desorption with simple pH control. More than 99% and 91% of the initial adsorption of MB and MO on the CCMD was maintained with five consecutive recycling.

Facile synthesis of magnetic biochar/Fe3O4 nanocomposites using electro-magnetization technique and its application on the removal of acid orange 7 from aqueous media

This study introduces a new methodology to synthesize magnetic biochar/Fe3O4 nanocomposites (M-BC) from marine macroalgae using a facile electro-magnetization technique. M-BC was prepared by stainless steel electrode-based electrochemical system, followed by pyrolysis. Physical and chemical analyses revealed that the porosity and magnetic properties were simultaneously improved via the electro-magnetization process, which enabled not only higher adsorption performance, but also easier separation/recovery from aqueous media at post-adsorption stage using a bar magnet. The adsorption equilibrium studies reveal that the Sips model satisfactorily predicts the adsorption capacity, which found to be 190, 297, and 382mgg(-1) at 10, 20, and 30°C, respectively. The overall findings indicate that one-step electro-magnetization technique can be effectively utilized for the fabrication of biochar with concurrent acquisition of porosity and magnetism, which can bring about new directions in the practical use of adsorption process in environment remediation and mitigate crises originating from it.

Mechanochemical removal of carbamazepine

Carbamazepine (CBZ) is a drug used for treating epilepsy, neuropathic pain, schizophrenia and bipolar disorder. Its widespread use is indicated by its listing in the WHO's Model List of Essential Medicines. The accumulation of CBZ in various environmental compartments, specifically in crops irrigated with treated effluent or grown on soils containing biosolids, is often reported. Being a persistent PPCP (a pharmaceutical and personal care product), developing procedures to remove CBZ is of great importance. In the present study, the breakdown of CBZ by surface reactions in contact with various minerals was attempted. While Al-montmorillonite enhanced CBZ disappearance without the need to apply mechanical force, the efficiency of magnetite in enhancing the disappearance increased considerably upon applying such force. Ball milling with magnetite generated a virtually complete disappearance of CBZ (∼94% of the applied CBZ disappeared after milling for 30 min). HPLC, LC/MS and FTIR were employed in an attempt to elucidate the rate of disappearance and degradation mechanisms of CBZ. A small amount of the hydrolysis product iminostilbene was identified by LC/MS and the breaking off of carbamic acid from the fused rings skeleton of CBZ was indicated by FTIR spectroscopy, confirming the formation of iminostilbene.

The Role of Surface Defects in the Adsorption of Methanol on Fe3O4(001)

The adsorption of methanol (CH₃OH) at the Fe₃O₄(001)−(√2 × √2)R45° surface was studied using X-ray photoelectron spectroscopy, scanning tunneling microscopy, and temperature-programmed desorption (TPD). CH₃OH adsorbs exclusively at surface defect sites at room temperature to form hydroxyl groups and methoxy (CH₃O) species. Active sites are identified as step edges, iron adatoms, antiphase domain boundaries in the (√2 × √2)R45° reconstruction, and above Fe atoms incorporated in the subsurface. In TPD, recombinative desorption is observed around 300 K, and a disproportionation reaction to form methanol and formaldehyde occurs at 470 K.

New hybrid magnetic nanoparticles based on chitosan-maltose derivative for antitumor drug delivery

The aim of the present study is to obtain, for the first time, polymer magnetic nanoparticles based on the chitosan-maltose derivative and magnetite. By chemically modifying the chitosan, its solubility in aqueous media was improved, which in turn facilitates the nanoparticles' preparation. Resulting polymers exhibit enhanced hydrophilia, which is an important factor in increasing the retention time of nanoparticles in the blood flow. The preparation of nanoparticles relied on the double crosslinking technique (ionic and covalent) in reverse emulsion which ensures the mechanical stability of the polymer carrier. The characterization of both the chitosan derivative and nanoparticles was accomplished by Fourier Transform Infrared Spectroscopy, Nuclear Magnetic Resonance Spectroscopy, Scanning Electron Microscopy, Transmission Electron Microscopy, Atomic Force Microscopy, Vibrating Sample Magnetometry, and Thermogravimetric Analysis. The evaluation of morphological, dimensional, structural, and magnetical properties, as well as thermal stability and swelling behavior of nanoparticles was made from the point of view of the polymer/magnetite ratio. The study of 5-Fluorouracil loading and release kinetics as well as evaluating the cytotoxicity and hemocompatibility of nanoparticles justify their adequate behavior in their potential use as devices for targeted transport of antitumor drugs.

Learning from magnetotactic bacteria: A review on the synthesis of biomimetic nanoparticles mediated by magnetosome-associated proteins

Much interest has gained the biomineralization process carried out by magnetotactic bacteria. These bacteria are ubiquitous in natural environments and share the ability to passively align along the magnetic field lines and actively swim along them. This ability is due to their magnetosome chain, each magnetosome consisting on a magnetic crystal enveloped by a lipid bilayer membrane to which very unique proteins are associated. Magnetotactic bacteria exquisitely control magnetosome formation, making the magnetosomes the ideal magnetic nanoparticle of potential use in many technological applications. The difficulty to scale up magnetosome production has triggered the research on the in vitro production of biomimetic (magnetosome-like) magnetite nanoparticles. In this context, magnetosome proteins are being used to mediate such in vitro magnetite precipitation experiments. The present work reviews the knowledgement on the magnetosome proteins thought to have a role on the in vivo formation of magnetite crystals in the magnetosome, and the recombinant magnetosome proteins used in vitro to form biomimetic magnetite. It also summarizes the data provided in the literature on the biomimetic magnetite nanoparticles obtained from those in vitro experiments.

Effect of magnetic pulses on Caribbean spiny lobsters: implications for magnetoreception

The Caribbean spiny lobster, Panulirus argus, is a migratory crustacean that uses Earth's magnetic field as a navigational cue, but how these lobsters detect magnetic fields is not known. Magnetic material thought to be magnetite has previously been detected in spiny lobsters, but its role in magnetoreception, if any, remains unclear. As a first step toward investigating whether lobsters might have magnetite-based magnetoreceptors, we subjected lobsters to strong, pulsed magnetic fields capable of reversing the magnetic dipole moment of biogenic magnetite crystals. Lobsters were subjected to a single pulse directed from posterior to anterior and either: (1) parallel to the horizontal component of the geomagnetic field (i.e. toward magnetic north); or (2) antiparallel to the horizontal field (i.e. toward magnetic south). An additional control group was handled but not subjected to a magnetic pulse. After treatment, each lobster was tethered in a water-filled arena located within 200 m of the capture location and allowed to walk in any direction. Control lobsters walked in seemingly random directions and were not significantly oriented as a group. In contrast, the two groups exposed to pulsed fields were significantly oriented in approximately opposite directions. Lobsters subjected to a magnetic pulse applied parallel to the geomagnetic horizontal component walked westward; those subjected to a pulse directed antiparallel to the geomagnetic horizontal component oriented approximately northeast. The finding that a magnetic pulse alters subsequent orientation behavior is consistent with the hypothesis that magnetoreception in spiny lobsters is based at least partly on magnetite-based magnetoreceptors.

Comparative evaluation of magnetite-graphene oxide and magnetite-reduced graphene oxide composite for As(III) and As(V) removal

Arsenic removal using Fe3O4-graphene oxide composite (M-GO) and Fe3O4-reduced graphene oxide composite (M-rGO) was investigated. The M-GO was more effective to adsorb both As(III) and As(V) than M-rGO, because the more functional groups existing on the M-GO could lead to synthesize more Fe3O4 with M-GO. As(III) was more favorable to be adsorbed than As(V) onto both M-GO and M-rGO. According to the effect of pH on arsenic removal, the electrostatic interaction between the positively charged surface of Fe3O4-graphene based adsorbents and anionic As(V) species was a major factor to adsorb As(V). The adsorption mechanism of As(III), on the other hand, was strongly affected by a surface complexation, rather than electrostatic interactions. Consequently, in terms of the process energy consumption, energy saving could be achieved via omitting the reduction process to fabricate M-rGO from M-GO and the pre-oxidation process to convert As(III) to As(V).

Nanosized Fe3O4 an efficient PCR yield enhancer-Comparative study with Au, Ag nanoparticles

Nanomaterials-assisted PCR is a promising field of nanobiotechnology that amalgamates nanomaterials into the conventional PCR system to achieve better amplification of desired product. With literature documenting the variable effects of these nanomaterials on the PCR yield and amplification; it was thought worthwhile to compare the PCR enhancing efficiency of three transition metal nanoparticles in form of stable colloidal suspensions at varying concentrations.The nanoparticles(NPs) of silver, gold and magnetite were chemically synthesized by reducing their respective salts and characterized using UV-vis spectroscopy. Their morphology was assessed using nanoparticle tracking system and AFM. The effect of these nanofluids on amplification of 800 bp prokaryotic DNA template with 30% GC content was studied using conventional thermal cycler. The reaction kinetics for all the three nanofluids yielded a Gaussian curve of amplification with varying concentrations. The ammonium salt of oleic acid coated magnetite (Fe3O4) nanoparticles at a concentration of 0.72 × 10(-2)nM and average size of 33 nm demonstrated highest amplification efficiency of 190% as compared to the citrate stabilized AgNP-25 nm (45%) and AuNP-15.19 nm (134%) using a conventional PCR system. The major reasons that allow Fe3O4 NPs outperform the other 2 transition metal NP's seem to be attributed to its heat conduction property as well as effective adsorption of PCR components onto the ammonium salt of oleic acid coated magnetite nanofluids. The data from our study offers valuable information for the application of ferrofluids as economically, efficient and effective alternative for nanomaterial-assisted PCR yield enhancers.

Enhanced and stabilized arsenic retention in microcosms through the microbial oxidation of ferrous iron by nitrate

Magnetite strongly retains As, and is relatively stable under Fe(III)-reducing conditions common in aquifers that release As. Here, laboratory microcosm experiments were conducted to investigate a potential As remediation method involving magnetite formation, using groundwater and sediments from the Vineland Superfund site. The microcosms were amended with various combinations of nitrate, Fe(II) (aq) (as ferrous sulfate) and lactate, and were incubated for more than 5 weeks. In the microcosms enriched with 10 mM nitrate and 5 mM Fe(II) (aq), black magnetic particles were produced, and As removal from solution was observed even under sustained Fe(III) reduction stimulated by the addition of 10 mM lactate. The enhanced As retention was mainly attributed to co-precipitation within magnetite and adsorption on a mixture of magnetite and ferrihydrite. Sequential chemical extraction, X-ray absorption spectroscopy and magnetic susceptibility measurements showed that these minerals formed at pH 6-7 following nitrate-Fe(II) addition, and As-bearing magnetite was stable under reducing conditions. Scanning electron microscopy and X-ray diffraction indicated that nano-particulate magnetite was produced as coatings on fine sediments, and no aging effect was detected on morphology over the course of incubation. These results suggest that a magnetite based strategy may be a long-term remedial option for As-contaminated aquifers.

A universal magnetic ferrofluid: Nanomagnetite stable hydrosol with no added dispersants and at neutral pH

A facile method to produce highly stable magnetite magnetic fluid at neutral pH without any stabilizing agents, resulting in pure Fe3O4 nanoparticles dispersed in water is described. The hydrosol which consists of only two components - magnetite and water - behaves as a typical ferrofluid, that is, although it responds to a magnetic field, the magnetic particles cannot be phase-separated from the water by that field. No such pure magnetic fluid have been described before, making it a universal carrier which can be easily modified for any application in materials science and chemistry, and in particular for a range of applications where non-corrosivity, low viscosity, and mild conditions are needed, such as in most bioapplications and in nano electro-mechanical systems. Under optimal conditions the hydrosol is stable for at least three months.

Ultrasound-assisted heterogeneous Fenton-like degradation of tetracycline over a magnetite catalyst

The degradation of tetracycline over Fe3O4 catalyst was studied by using a coupled ultrasound/heterogeneous Fenton process. The effects of some key reaction parameters, the evolution of toxicity, and the reaction mechanism were investigated. Experimental results showed that the stability of catalyst was significantly improved when ultrasound was employed. Under optimal conditions, 93.6% of tetracycline was removed after 60 min of treatment. The removal efficiency of the total organic carbon (TOC) at 60 min was 31.8%. The surface hydroxyl radicals were identified as the major reactive species during the oxidation process. Toxicity tests with Daphnia magna indicated that the toxicity of the solution increased during the first 60 min and then decreased as the oxidation proceeded.

AN in vitro evaluation of a carmustine-loaded Nano-co-Plex for potential magnetic-targeted intranasal delivery to the brain

Targeted delivery of carmustine (BCNU), an efficient brain tumor therapeutic, has been challenged with bioavailability issues due to the Blood Brain Barrier (BBB). The currently effective delivery approach is by implants at the site of the tumor, but this is highly invasive. The intranasal route, which is non-invasive and bypasses the BBB, may be alternative route for delivering BCNU to the brain. In this work, polyvinyl alcohol/polyethyleneimine/fIuorecein isothiocyanate complex (Polyplex) coated iron-oxide nanoparticles (Magnetite) were synthesized employing co-precipitation, epoxidation and EDC/NHS coupling reactions. The Polyplex coated magnetite (Nano-co-Plex) was loaded with BCNU for potential magnetically targeted delivery to the brain following intranasal administration. The Nano-co-Plex was characterized employing Thermogravimetric analysis (TGA), Superconducting Quantum Interference Device (SQUID) magnetometry, Fourier Transform Infrared Spectroscopy (FTIR), Nuclear Magnetic Resonance (NMR), X-ray Diffractometry (XRD), Transmission Electron Microscopy (TEM) and Zetasize analysis. Results revealed superparamagnetic hexagonally shaped "core-shell" nanoparticles with cell labeling attributes, of size ranging between 30-50 nm, and a zeta potential value of + 32 ± 2 mV. The Nano-co-Plex synthesized was found to possess high degree of crystallinity with 32% Polyplex coating. The loading and release studies indicated a time-dependent loading with maximum loading capacity of 176.82 μg BCNU/mg of the carrier and maximum release of 75.8% of the loaded BCNU. Cytotoxicity of the BCNU-loaded Nano-co-Plex displayed superiority over the conventional BCNU towards human glioblastoma (HG) cells. Cell studies revealed enhanced uptake and internalization of BCNU-loaded Nano-co-plex in HG cells in the presence of an external magnetic field. These Nano-co-Plexes may be ideal as an intranasal magnetic drug targeting device for BCNU delivery.

Effect of nanoscale zero-valent iron and magnetite (Fe3O4) on the fate of metals during anaerobic digestion of sludge

Anaerobic digestion (AD) is one of the most widely used processes to stabilize waste sewage sludge and produce biogas renewable energy. In this study, two different iron nanoparticles [nanoscale zero-valent iron (nZVI) and magnetite (Fe3O4)] were used in the mesophilic AD processes (37 ± 1 °C) to improve biogas production. In addition, changes of heavy metal (Cd, Co, Cu, Zn, Ni and Cr) speciation during AD of sludge with and without iron nanoparticles have been investigated. Concentrations of metals in the initial sludge were as follows: 63.1, 73.4, 1102.2, 2060.3, 483.9 and 604.1 mg kg(-1) (dry sludge basis) for Cd, Co, Cu, Zn, Ni and Cr, respectively. Sequential fractionation showed that metals were predominantly bonded to organic matter and carbonates in the initial sludge. Compared with AD without iron nanoparticles, the application of iron nanoparticles (at dose of 0.5% in this study) showed positive impact not only on biogas production, but also on improvement of metals stabilization in the digestate. Metals were found concentrated in Fe-Mn bound and residual fractions and little was accumulated in the liquid digestate and most mobile fractions of solid digestate (water soluble, exchangeable and carbonates bound). Therefore, iron nanoparticles when properly used, could improve not only biogas yield, but also regulate and control the mobilization of metals during AD process. However, our study also observed that iron nanoparticles could promote the immobilization of phosphorus within the sludge during AD, and more research is needed to fully address the mechanism behind this phenomenon and the impact on future phosphorus reuse.

Effects of common groundwater ions on chromate removal by magnetite: importance of chromate adsorption

BACKGROUND

Reductive precipitation of hexavalent chromium (Cr(VI)) with magnetite is a well-known Cr(VI) remediation method to improve water quality. The rapid (<a few hr) reduction of soluble Cr(VI) to insoluble Cr(III) species by Fe(II) in magnetite has been the primary focus of the Cr(VI) removal process in the past. However, the contribution of simultaneous Cr(VI) adsorption processes in aged magnetite has been largely ignored, leaving uncertainties in evaluating the application of in situ Cr remediation technologies for aqueous systems. In this study, effects of common groundwater ions (i.e., nitrate and sulfate) on Cr(VI) sorption to magnetite were investigated using batch geochemical experiments in conjunction with X-ray absorption spectroscopy.

RESULTS

In both nitrate and sulfate electrolytes, batch sorption experiments showed that Cr(VI) sorption decreases with increasing pH from 4 to 8. In this pH range, Cr(VI) sorption decreased with increasing ionic strength of sulfate from 0.01 to 0.1 M whereas nitrate concentrations did not alter the Cr(VI) sorption behavior. This indicates the background electrolyte specific Cr(VI) sorption process in magnetite. Under the same ionic strength, Cr(VI) removal in sulfate containing solutions was greater than that in nitrate solutions. This is because the oxidation of Fe(II) by nitrate is more thermodynamically favorable than by sulfate, leaving less reduction capacity of magnetite to reduce Cr(VI) in the nitrate media. X-ray absorption spectroscopy analysis supports the macroscopic evidence that more than 75 % of total Cr on the magnetite surfaces was adsorbed Cr(VI) species after 48 h.

CONCLUSION

This experimental geochemical study showed that the adsorption process of Cr(VI) anions was as important as the reductive precipitation of Cr(III) in describing the removal of Cr(VI) by magnetite, and these interfacial adsorption processes could be impacted by common groundwater ions like sulfate and nitrate. The results of this study highlight new information about the large quantity of adsorbed Cr(VI) surface complexes at the magnetite-water interface. It has implications for predicting the long-term stability of Cr at the magnetite-water interface.Graphical abstractEffects of background anions (sulfate and nitrate) on the Cr(VI) surface coverage at the magnetite-water interface at pH 4 and 9.

Preparation and in vitro evaluation of 5-flourouracil loaded magnetite-zeolite nanocomposite (5-FU-MZNC) for cancer drug delivery applications

In this work, super paramagnetic magnetite nanoparticles were synthesized onto/into zeolite, then loaded with anti-cancer drug 5-fluorouracil (5-FU). The physical properties of the prepared nanocomposite and drug loaded nanocomposite were characterized using different techniques. The drug loading and releasing behavior of the magnetic nanocarrier was investigated and the drug-loaded nanoparticles exhibited a sustained release of drug without any burst release phenomenon. Furthermore, 5-FU loaded MZNC were evaluated for its biological characteristics. The functional 5-FU-MZNC has been triggered intra-cellular release of the cancer therapeutic agent 5-fluorouracil (5-FU). Cytotoxic effects of 5-FU loaded MZNC on human gastric carcinoma (AGS) cells were determined by real time cell analysis and colorimetric WST-1 cell viability assay. Apoptosis of cells was further investigated by Annexin-V staining which indicates the loss of cell membrane integrity. According to our results, 5-FU-MZNC showed a concentration-dependent cell proliferation inhibitory function against AGS cells. Morphologic and apoptotic images were consistent with the cytotoxicity results. In conclusion, 5-FU loaded MZNC efficiently inhibit the proliferation of AGS cells in vitro through apoptotic mechanisms, and may be a beneficial agent against cancer, however further animal study is still required.

Disturbance of ion environment and immune regulation following biodistribution of magnetic iron oxide nanoparticles injected intravenously

Although it is expected that accumulation of metal oxide nanoparticles that can induce redox reaction in the biological system may influence ion homeostasis and immune regulation through generation of free radicals, the relationship is still unclear. In this study, mice received magnetic iron oxide nanoparticles (M-FeNPs, 2 and 4 mg/kg) a single via the tail vein, and their distribution in tissues was investigated over time (1, 4, and 13 weeks). In addition, we evaluated the effects on homeostasis of redox reaction-related elements, the ion environment and immune regulation. The iron level in tissues reached at the maximum on 4 weeks after injection and M-FeNPs the most distributed in the spleen at 13 weeks. Additionally, levels of redox reaction-related elements in tissues were notably altered since 1 week post-injection. While levels of K(+) and Na(+) in tissue tended to decrease with time, Ca(2+) levels reached to the maximum at 4 weeks post-injection. On 13 weeks post-injection, the increased percentages of neutrophils and eosinophils, the enhanced release of LDH, and the elevated secretion of IL-8 and IL-6 were clearly observed in the blood of M-FeNP-treated mice compared to the control. While expression of antigen presentation related-proteins and the maturation of dendritic cells were markedly inhibited following distribution of M-FeNPs, the expression of several chemokines, including CXCR2, CCR5, and CD123, was enhanced on the splenocytes of the treated groups. Taken together, we suggest that accumulation of M-FeNPs may induce adverse health effects by disturbing homeostasis of the immune regulation and ion environment.

Removing pentachlorophenol from water using a nanoscale zero-valent iron/H2O2 system

Nanoscale zero-valent iron (nZVI) is an environmentally benign material that has been widely used as a reducing agent to treat environmental pollutants. In this study, nZVI was used as a heterogeneous Fenton catalyst in an nZVI/H2O2 system to remove pentachlorophenol (PCP) from water. The PCP degradation process in the nZVI/H2O2 system was completed within 1h. The relative Cl(-) concentration increased throughout the test period (6h), indicating that the performance of the oxidative system in terms of dechlorination was excellent. The initial H2O2 concentration significantly influenced the PCP removal rate, and nZVI performed better than commercial zero-valent iron as a catalyst. Moreover, magnetite (Fe3O4), which was the main product of the corrosion of nZVI, was found to perform well as an adsorbent and catalyst, so it allowed the nZVI to be effectively reused.

Magnetic susceptibility and isothermal remanent magnetization in human tissues: a study case

This study evaluated the magnetic properties, magnetic susceptibility and isothermal remanent magnetization (IRM) of tissue samples from the brain, liver, spleen, pancreas, heart and lungs, resected from human corpses, with the aim of identifying the magnetic mineral structures and understanding their possible connection to diseases, professional activity, age and gender of the individual, smoking habits and the environment. The heart was the organ with the highest values of magnetic susceptibility and the pancreas showed the lowest values. No relationship was found between magnetic susceptibility, IRM values and ages of the individuals. However the samples obtained in females showed lower values of magnetic susceptibility than those resected from males. The samples collected from the lungs of smokers have higher values of magnetic susceptibility and IRM indicating the presence of magnetic particles with an anthropic origin. Moreover, the complexity of the magnetic behaviour of these tissues may suggest a contribution of both biogenic and anthropogenic magnetic particles also due to some professional activities. In the brain a heterogeneous distribution of the magnetic susceptibility values was found, which might be related mainly to the diamagnetic behaviour of myelin-rich structures. This study suggests that although the diamagnetic and paramagnetic behaviour is common to all structures, magnetite-type structures are always present in the tissues and hematite-type structures may also contribute to the magnetic signal of the sample. IRM values are only dependent on the presence of magnetite or hematite-type magnetic structures and so this technique seems more suitable to achieve the characterization of biomagnetic structures than magnetic susceptibility.

Accelerated methanogenesis from effluents of hydrogen-producing stage in anaerobic digestion by mixed cultures enriched with acetate and nano-sized magnetite particles

Potential for paddy soil enrichments obtained in the presence of nano-sized magnetite particles (named as PSEM) to promote methane production from effluents of hydrogen-producing stage in two-stage anaerobic digestion was investigated. The results showed that the addition of magnetite significantly accelerated methane production from acetate in a dose-independent manner. The results from high-throughput sequencing analysis revealed that Rhodocyclaceae-related species were selectively enriched, which were likely the key players for conversion of acetate to methane in PSEM. Compared to the paddy soil enrichments obtained in the absence of magnetite (named as PSEC), the maximum methane production rate in PSEM was significantly higher (1.5-5.5times higher for the artificial medium and 0.2-1.7times higher for the effluents). The accelerated methane production from the effluents indicated remarkably application potential of PSEM for improving performance of anaerobic digestion.

Facile synthesis of magnetically separable reduced graphene oxide/magnetite/silver nanocomposites with enhanced catalytic activity

In this study, the combination of magnetite (Fe3O4) with reduced graphene oxide (RGO) generates a new hybrid substrate for the dispersion of noble metal nanoparticles. Well-dispersed silver (Ag) nanoparticles loaded on the surface of Fe3O4 modified RGO are achieved by an efficient two-step approach. Through reducing Ag(+) ions, highly dispersed Ag nanoparticles are in-situ formed on the RGO/Fe3O4 substrate. It is found that the existence of Fe3O4 nanocrystals can significantly improve the dispersity and decrease the particle size of the in-situ formed Ag nanoparticles. Magnetic study reveals that the as-prepared RGO/Fe3O4/Ag ternary nanocomposites display room-temperature superparamagnetic behavior. The catalytic properties of the RGO/Fe3O4/Ag ternary nanocomposites were evaluated with the reduction of 4-nitrophenol into 4-aminophenol as a model reaction. The as-synthesized RGO/Fe3O4/Ag ternary catalysts exhibit excellent catalytic stability and much higher catalytic activity than the corresponding RGO/Ag catalyst. Moreover, the RGO/Fe3O4/Ag catalysts can be easily magnetically separated for reuse. This study further demonstrates that nanoparticles modified graphene can act as an effective hybrid substrate for the synthesis of multi-component and multifunctional graphene-based composites.

Effective treatment of alkaline Cr(VI) contaminated leachate using a novel Pd-bionanocatalyst: Impact of electron donor and aqueous geochemistry

Palladium catalysts offer the potential for the effective treatment of a variety of priority reducible pollutants in natural waters. In this study, microbially synthesized magnetite nanoparticles were functionalized with Pd(0), creating a highly reactive, magnetically recoverable, nano-scale catalyst (Pd-BnM). This was then investigated for the treatment of model Cr(VI) contaminated solutions at a range of pH values, and also alkaline Cr(VI) contaminated leachates from chromite ore processing residue (COPR); a contaminant issue of global concern. The sample of COPR used in this study was obtained from a site in Glasgow, UK, where extensive Cr(VI) contamination has been reported. In initial experiments Pd-BnM was supplied with H₂ gas or formate as electron donors, and Cr(VI) removal from model synthetic solutions was quantified at various pH values (2-12). Effective removal was noted at neutral to environmentally relevant alkaline (pH 12) pH values, while the use of formate as an electron donor resulted in loss of performance under acidic conditions (pH 2). Reaction kinetics were then assessed with increasing Pd-BnM loading in both model pH 12 Cr(VI) solutions and the COPR leachate. When formate was used as the electron donor for Pd-BnM, to treat COPR leachate, there was significant inhibition of Cr(VI) removal. In contrast, a promotion of reaction rate, was observed when H₂ was employed. Upon sustained reaction with model Cr(VI) solutions, in the presence of excess electron donor (formate or H₂), appreciable quantities of Cr(VI) were removed before eventual inactivation of the catalyst. Faster onset of inactivation was reported in the COPR leachates, removing 4% and 64% of Cr(VI) observed from model Cr(VI) solutions, when formate and H₂ were used as electron donors, respectively. XAS, TEM-EDX and XPS analysis of the catalysts that had been inactivated in the model solution, showed that the surface had an extensive covering of reduced Cr(III), most likely as a CrOOH phase. COPR reacted catalysts recorded a lower abundance of Cr(III) alongside a high abundance of the leachate components Ca and Si, implicating these elements in the faster onset of inactivation.

pH-Triggered Magnetic-Chitosan Nanogels (MCNs) For Doxorubicin Delivery: Physically vs. Chemically Cross Linking Approach

PURPOSE

This paper evaluates the impact of cross linking strategy on the characteristics of magnetic chitosan nanogels (MCNs) as targeted drug delivery system for doxorubicin.

METHODS

Sodium tripolyphosphate (TPP) and glutaraldehyde were used as physical (electrostatic) and chemical (covalent binding) cross-linker agents, respectively. MCNs were characterized by means of X-ray diffraction (XRD), Scanning electron microscopy (SEM), fourier transform infrared (FT-IR) spectroscopy and vibrating sample magnetometer (VSM). Scanning electron microscopy (SEM) indicated the formation of spherical nanostructures with the final average particle size of around 35-40 nm.

RESULTS

The finding proved the superparamagnetic properties of the MCNs with relatively high-magnetization values which indicate that the MCNs were enough sensitive to external magnetic fields as a magnetic drug carrier. To understand the differences between the drug delivery properties of chemically and physically cross linked MCNs, the drug release studies were also conducted. Altogether, the results of this study clearly indicate that, however, both MCNs exhibited sustained drug release behaviour, the chemically cross linked MCNs provided enhanced controlled drug release characteristics in comparison to physically cross linked MCNs. Besides, according to the drug release behaviour of MCNs in buffer solutions in two different medium with the pH values of 5.3 and 7.4, it was clear that both nanoparticles exhibited pH sensitivity where the extent of drug release in the acidic media was significantly higher than neutral media.

CONCLUSION

It can be concluded that chemically cross linked MCNs may serve as an ideal carrier for stimuli-triggered and controlled anticancer drug delivery.

Functional biocompatible magnetite-cellulose nanocomposite fibrous networks: Characterization by fourier transformed infrared spectroscopy, X-ray powder diffraction and field emission scanning electron microscopy analysis

The preparation and characterization of functional biocompatible magnetite-cellulose nano-composite fibrous material is described. Magnetite-cellulose nano-composite was prepared by a combination of the solution-based formation of magnetic nano-particles and subsequent coating with amino celluloses. Characterization was accomplished using X-ray powder diffraction (XRD), fourier transformed infrared (FTIR) and field emission scanning electron microscopy (FESEM) analysis. The peaks of Fe3O4 in the XRD pattern of nanocomposite confirm existence of the nanoparticles in the amino cellulose matrix. Magnetite-cellulose particles exhibit an average diameter of roughly 33nm as demonstrated by field emission scanning electron microscopy. Magnetite nanoparticles were irregular spheres dispersed in the cellulose matrix. The vibration corresponding to the NCH3 functional group about 2850cm(-1) is assigned in the FTIR spectra. Functionalized magnetite-cellulose nano-composite polymers have a potential range of application as targeted drug delivery system in biomedical field.

Removal of Hg(II) by poly(1-vinylimidazole)-grafted Fe3O4@SiO2 magnetic nanoparticles

Fe3O4@SiO2 magnetic nanoparticles modified by grafting poly(1-vinylimidazole) oligomer (FSPV) was fabricated as a novel adsorbent to remove Hg(II) from water. Fourier transform infra-red spectroscopy confirmed the successful grafting of oligomer, and thermogravimetric analysis showed FSPV had a high grafting yield with organic content of 22.8%. Transmission electron microscopy image displayed that FSPV particles were polymer-coated spheres with size of 10-20 nm. With saturation magnetization of 44.7 emu/g, FSPV particles could be easily separated from water with a simple magnetic process in 5 min. The Hg(II) adsorption capacity of FSPV was found to be 346 mg/g at pH 7 and 25 °C in 10 mM NaCl. Moreover, the removal of Hg(II) by FSPV was not obviously affected by solution pH (from 4 to 10) or humic acid (up to 8 mg/L as TOC). The presence of seven common ions including Na(+), K(+), Ca(2+), Mg(2+), Cl(-), NO3(-), and SO4(2-) (up to 100 mM ionic strength) slightly increased the adsorption of Hg(II) by FSPV. X-ray photoelectron spectroscopy analysis revealed that the N atom of the imidazole ring was responsible for the bonding with Hg(II), whereas the bonding of Hg with N did not result in cleavage of Hg-Cl bond in HgCl2 and HgClOH. The regeneration of Hg(II)-loaded FSPV could be achieved with 0.5 M HCl rapidly in 10 min, and the removal of Hg(II) maintained above 94% in five consecutive adsorption-desorption cycles. Therefore, FSPV could serve as a promising adsorbent for Hg(II) removal from water.

Measuring and modeling the magnetic settling of superparamagnetic nanoparticle dispersions

In this paper, we present settling experiments and mathematical modeling to study the magnetic separation of superparamagnetic iron-oxide nanoparticles (SPIONs) from a brine. The experiments were performed using SPIONs suspensions of concentration between 3 and 202g/L dispersed in water and separated from the liquid under the effect of a permanent magnet. A 1D model was developed in the framework of the sedimentation theory with a conservation law for SPIONs and a mass flux function based on the Newton's law for motion in a magnetic field. The model describes both the hindering effect of suspension concentration (n) during settling due to particle collisions and the increase in settling rate due to the attraction of the SPIONs towards the magnet. The flux function was derived from the settling experiments and the numerical model validated against the analytical solution and the experimental data. Suspensions of SPIONs were of 2.8cm initial height, placed on a magnet, and monitored continuously with a digital camera. Applying a magnetic field of 0.5T of polarization, the SPION's velocity was of approximately 3·10(-5)m/s close to the magnet and decreases of two orders of magnitude across the domain. The process was characterized initially by a classical sedimentation behavior, i.e., an upper interface between the clear water and the suspension slowly moving towards the magnet and a lower interface between the sediment layer and the suspension moving away from the magnet. Subsequently, a rapid separation of nanoparticle occured suggesting a non-classical settling phenomenon induced by magnetic forces which favor particle aggregation and therefore faster settling. The rate of settling decreased with n and an optimal condition for fast separation was found for an initial n of 120g/L. The model agrees well with the measurements in the early stage of the settling, but it fails to describe the upper interface movement during the later stage, probably because of particle aggregation induced by magnetization which is not accounted for in the model.