Discovering the potential of an nZVI-biochar composite as a material for the nanobioremediation of chlorinated solvents in groundwater: Degradation efficiency and effect on resident microorganisms.

Abiotic and biotic remediation of chlorinated ethenes (CEs) in groundwater from a real contaminated site was studied using biochar-based composites containing nanoscale zero-valent iron (nZVI/BC) and natural resident microbes/specific CE degraders supported by a whey addition. The material represented by the biochar matrix decorated by isolated iron nanoparticles or their aggregates, along with the added whey, was capable of a stepwise dechlorination of CEs. The tested materials (nZVI/BC and BC) were able to decrease the original TCE concentration by 99% in 30 days. Nevertheless, regarding the transformation products, it was clear that biotic as well as abiotic transformation mechanisms were involved in the transformation process when nonchlorinated volatiles (i.e., methane, ethane, ethene, and acetylene) were detected after the application of nZVI/BC and nZVI/BC with whey. The whey addition caused a massive increase in bacterial biomass in the groundwater samples (monitored by 16S rRNA sequencing and qPCR) that corresponded with the transformation of trichloro- and dichloro-CEs, and this process was accompanied by the formation of less chlorinated products. Moreover, the biostimulation step also eliminated the adverse effect caused by nZVI/BC (decrease in microbial biomass after nZVI/BC addition). The nZVI/BC material or its aging products, and probably together with vinyl chloride-respiring bacteria, were able to continue the further reductive dechlorination of dichlorinated CEs into nonhalogenated volatiles. Overall, the results of the present study demonstrate the potential, feasibility, and environmental safety of this nanobioremediation approach.

Synthesis of flower-like magnetite nanoassembly: Application in the efficient reduction of nitroarenes.

A facile approach for the synthesis of magnetite microspheres with flower-like morphology is reported that proceeds via the reduction of iron(III) oxide under a hydrogen atmosphere. The ensuing magnetic catalyst is well characterized by XRD, FE-SEM, TEM, N2 adsorption-desorption isotherm, and Mössbauer spectroscopy and explored for a simple yet efficient transfer hydrogenation reduction of a variety of nitroarenes to respective anilines in good to excellent yields (up to 98%) employing hydrazine hydrate. The catalyst could be easily separated at the end of a reaction using an external magnet and can be recycled up to 10 times without any loss in catalytic activity.

Degradation of the cyanotoxin microcystin-LR using iron-based photocatalysts under visible light illumination.

In this study, a simple and low-cost method to synthesize iron(III) oxide nanopowders in large quantity was successfully developed for the photocatalytic degradation of microcystin-LR (MC-LR). Two visible light-active iron(III) oxide samples (MG-9 calcined at 200 °C for 5 h and MG-11 calcined at 180 °C for 16 h) with a particle size of 5-20 nm were prepared via thermal decomposition of ferrous oxalate dihydrate in air without any other modifications such as doping. The synthesized samples were characterized by X-ray powder diffraction, 57Fe Mössbauer spectroscopy, transmission electron microscopy, Brunauer-Emmett-Teller (BET) specific surface area analysis, and UV-visible diffuse reflectance spectroscopy. The samples exhibited similar phase composition (a mixture of α-Fe2O3 and γ-Fe2O3), particle size distribution (5-20 nm), particle morphology, and degree of agglomeration, but different specific surface areas (234 m2 g-1 for MG-9 and 207 m2 g-1 for MG-11). The results confirmed higher photocatalytic activity of the catalyst with higher specific surface area. The highest photocatalytic activity of the sample to decompose MC-LR was observed at solution pH of 3.0 and catalyst loading of 0.5 g L-1 due to large amount of MC-LR adsorption, but a little iron dissolution of 0.0065 wt% was observed. However, no iron leaching was observed at pH 5.8 even though the overall MC-LR removal was slightly lower than at pH 3.0. Thus, the pH 5.8 could be an appropriate operating condition for the catalyst to avoid problems of iron contamination by the catalyst. Moreover, magnetic behavior of γ-Fe2O3 gives a possibility for an easy separation of the catalyst particles after their use.

Fe(0) Nanomotors in Ton Quantities (10(20) Units) for Environmental Remediation.

Despite demonstrating potential for environmental remediation and biomedical applications, the practical environmental applications of autonomous self-propelled micro-/nanorobots have been limited by the inability to fabricate these devices in large (kilograms/tons) quantities. In view of the demand for large-scale environmental remediation by micro-/nanomotors, which are easily synthesized and powered by nontoxic fuel, we have developed bubble-propelled Fe(0) Janus nanomotors by a facile thermally induced solid-state procedure and investigated their potential as decontamination agents of pollutants. These Fe(0) Janus nanomotors, stabilized by an ultrathin iron oxide shell, were fuelled by their decomposition in citric acid, leading to the asymmetric bubble propulsion. The degradation of azo-dyes was dramatically increased in the presence of moving self-propelled Fe(0) nanomotors, which acted as reducing agents. Such enhanced pollutant decomposition triggered by biocompatible Fe(0) (nanoscale zero-valent iron motors), which can be handled in the air and fabricated in ton quantities for low cost, will revolutionize the way that environmental remediation is carried out.

Air stable magnetic bimetallic Fe-Ag nanoparticles for advanced antimicrobial treatment and phosphorus removal.

We report on new magnetic bimetallic Fe-Ag nanoparticles (NPs) which exhibit significant antibacterial and antifungal activities against a variety of microorganisms including disease causing pathogens, as well as prolonged action and high efficiency of phosphorus removal. The preparation of these multifunctional hybrids, based on direct reduction of silver ions by commercially available zerovalent iron nanoparticles (nZVI) is fast, simple, feasible in a large scale with a controllable silver NP content and size. The microscopic observations (transmission electron microscopy, scanning electron microscopy/electron diffraction spectroscopy) and phase analyses (X-ray diffraction, Mössbauer spectroscopy) reveal the formation of Fe3O4/γ-FeOOH double shell on a "redox" active nZVI surface. This shell is probably responsible for high stability of magnetic bimetallic Fe-Ag NPs during storage in air. Silver NPs, ranging between 10 and 30 nm depending on the initial concentration of AgNO3, are firmly bound to Fe NPs, which prevents their release even during a long-term sonication. Taking into account the possibility of easy magnetic separation of the novel bimetallic Fe-Ag NPs, they represent a highly promising material for advanced antimicrobial and reductive water treatment technologies.

Catalytic efficiency of iron(III) oxides in decomposition of hydrogen peroxide: competition between the surface area and crystallinity of nanoparticles.

Various iron(III) oxide catalysts were prepared by controlled decomposition of a narrow layer (ca. 1 mm) of iron(II) oxalate dihydrate, FeC(2)O(4).2H(2)O, in air at the minimum conversion temperature of 175 degrees C. This thermally induced solid-state process allows for simple synthesis of amorphous Fe(2)O(3) nanoparticles and their controlled one-step crystallization to hematite (alpha-Fe(2)O(3)). Thus, nanopowders differing in surface area and particle crystallinity can be produced depending on the reaction time. The phase composition of iron(III) oxides was monitored by XRD and (57)Fe Mössbauer spectroscopy including in-field measurements, providing information on the relative contents of amorphous and crystalline phases. The gradual changes in particle size and surface area accompanying crystallization were evaluated by HRTEM and BET analysis, respectively. The catalytic efficiency of the synthesized nanoparticles was tested by tracking the decomposition of hydrogen peroxide. The obtained kinetic data gave an unconventional nonmonotone dependence of the rate constant on the surface area of the samples. The amorphous nanopowder with the largest surface area of 401 m(2) g(-1) revealed the lowest catalytic efficiency, while the highest efficiency was achieved with the sample having a significantly lower surface area, 337 m(2) g(-1), exhibiting a prevailing content of crystalline alpha-Fe(2)O(3) phase. The obtained rate constant, 26.4 x 10(-3) min(-1) (g/L)(-1), is currently the highest value published. The observed rare catalytic phenomenon, where the particle crystallinity prevails over the surface area effects, is discussed with respect to other processes of heterogeneous catalysis.