Synthesis, Characterization And Activity Of New Iron-Based Materials

In recent years, with the development of economic, our life becomes more and more convenient However, serious environment pollution also came into being. Pollutants came from increasing population, emissions of industrial and domestic sewage, emission of motor vehicle exhaust, bring serious pollution to atmosphere, water and soil. How to deal with environmental pollution has become a focus of global concern. Among the treatment of environmental pollution, as one of the most abundant metal element, iron plays a very important role in the field of environmental catalysis. Iron-based materials (IBMs) have advantages of non-pollution to the environment, high activity, low cost and so on. Thus they have a promising application prospects. Therefore, the exploration of novel iron-based materials has become more and more attractive.Iron-based materials, including multiferroic composite material, ferrous iron (hydrogen) oxide, iron alloy, zero valent iron and so on, all exhibit excellent activity for the treatment of environmental pollution. During the decomposition of organic pollutants, IBMs can react with absorbed H2O, O2, and OH", resulting in large amount of active oxygen radicals including H2O2,·O2-,·OH, which can oxide pollutants in gas and water effectively. Therefore, investigation of the reaction mechanism during the degradation of pollutants, improving the amount of active species can extend the application field of IBMs.Therefore, our work mainly focused on exploring novel IBMs with simple preparation, low energy consumption, and excellent catalytic activity. Then we investigated the role and mechanism of IBMs in the treatment of air and water pollution. This disssertation first introduced the current situation of environmental pollution, and highlighted the pollution of gas and water, current atmospheric and water control technology, and researches about IBMs. Then we elaborated the synthesis of patterned hierarchical LaFeO3fibers, FeCl3/AC catalyst, and core-shell Fe@Fe2O3nanowires. The crystal structure, composition, morphology, activity, and mechanism of these resulting materials were characterized by XRD, XPS, SEM, TEM and so on.The detailed works were shown as the following:1. Hierarchical LaFeO3fibers were prepared by a sol-gel nanocasting method using a cotton cloth as the template. The resulting products were characterized by scanning electron microscopy, powder X-ray diffraction, X-ray photoelectron spectroscopy, transmission electron microscopy, nitrogen adsorption and test of CO oxidation. It was discovered that the resulting LaFeO3fibers inherited the initial network morphology of the template very well. The high-magnification SEM images revealed that the hierarchical cellulosic structure of LaFeO3fibers comprises subunits of numerous nanoparticles with diameters of about30～40nm. While conventional sol-gel synthesized LaFeO3was composed of irregular aggregates of nanoparticles with about30-200nm in size. We also proposed apossible formation processes of LaFeO3particles and fibers. LaFeO3fibers produced by sol-gel nanocasting method showed enhanced catalytic CO oxidation activity and satisfactory stability compared to the counterpart particles prepared by the conventional sol-gel method.2. We synthesized FeCl3-loaded active carbon (FeCl3AC) catalyst under room temperature by a simple impregnation method. Then we demonstrated a rapid catalytic microwave method to deal with Microcystis aeruginosa with FeCl3/AC cataylst. Microcystis aeruginosa damage process was monitored by measuring optical density, chlorophyll-a content, superoxide dismutase activity, L-glutathione content, and turbidity of the treated Microcystis aeruginosa suspension. It was discovered that Microcystis aeruginosa could be damaged in a very short time of2.5min under microwave irradiation with FeCl3/AC catalyst. We also investigated the damage mechanism. When Fe3+was added into M. aeruginosa alone, the ions hydrolyzed to form Fe(OH)3, then M. aeruginosa cells likely adhered on the surface of Fe(OH)3to result in precipitation, M. aeruginosa was not damaged. From XPS result of FeCl3/AC, we discovered that during the microwave catalytic reaction, the peak of Fe increased. So we ascribed the excellent activity of FeC13/AC induced M. aeruginosa damage under microwave irradiation to the charge transfer-induced doping effect. That is, when FeCl3/AC was added into M. aeruginosa suspension, the cells could quickly be adsorbed on the surface of AC. Meanwhile, the so-called charge transfer-induced doping effect could realize electrons transferring from AC to Fe ions, thus leaving holes on AC to attack and oxidize the cells. This work provides a fast and green treatment method for cyanobacterial blooms.3. Core-shell Fe@Fe2O3nanowires were prepared in this work. Oxygen diffusion cathode Fe@Fe2O3/ACF was obtained by loading the nanowires on active carbon fibers. Then Fe@Fe2O3/ACF was used in E-Fenton oxidation system at neutral pH to degrade RhB. It was found that Fe@Fe2O3nanowires could enhance RhB degradation significantly. On the basis of the experiment, it was discovered that in the E-Fenton system, Fe@Fe2O3nanowires could induce the activation of molecular oxygen to produce superoxides which could enhance RhB degradation. The obtained superoxides could react with protons and electrons subsequently to generate H2O2. These extra H2O2and the cationically generated H2O2could react with in-situ released ferrous ions to produce more abundant hydroxide radicals, which could enhance the degradation of RhB.4. On the basis of the previous work, we further investigated the activity of Fe@Fe2O3nanowires on CO2reducntion in a microbial fuel cell (MFC). Fe@Fe2O3/carbon felt electrode was perpared and used in MFC as cathode. We investigated the influence parameters in the reduction of CO2and got the optimal conditions for CO2reduction. Products of the reduction were monitored by Ion Chromatograph. And we found that the main product was HCOOH. Loading of Fe@Fe2O3nanowires on carbon felt could significantly enhance the production of HCOOH. Also the anode was very stable in MFC system. We suggested that Fe2O3participated in the pathway of CO2reduction on Fe and enabled CO2redution to occur by stabilizing·CO2-(intermediate product during CO2reducion). We investigated for the first time that in MFC system, CO2can be reduced with Fe@Fe2O3/carbon felt cathode without any extra voltage.