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Iron nanomaterials including nanoscale zero valent iron (NZVI), NZVI-based bimetallic reductants (e.g., Pd/NZVI) and naturally occurring nanoscale iron mineral phases represent promising treatment tools for impaired water supplies. However, questions pertaining to fundamental and practical aspects of their reactivity may limit their performance during applications.
Nanotechnology has a great potential for providing efficient, cost-effective, and environmentally acceptable solutions to face the increasing requirements on quality and quantity of fresh water for industrial, agricultural, or human use. Iron nanomaterials, either zerovalent iron (nZVI) or iron oxides (nFeOx), present key physicochemical properties that make them particularly attractive as contaminant removal agents for water and soil cleaning. The large surface area of these nanoparticles imparts high sorption capacity to them, along with the ability to be functionalized for the enhancement of their affinity and selectivity. However, one of the most important properties is the outstanding capacity to act as redox-active materials, transforming the pollutants to less noxious chemical species by either oxidation or reduction, such as reduction of Cr(VI) to Cr(III) and dehalogenation of hydrocarbons. This book focuses on the methods of preparation of iron nanomaterials that can carry out contaminant removal processes and the use of these nanoparticles for cleaning waters and soils. It carefully explains the different aspects of the synthesis and characterization of iron nanoparticles and methods to evaluate their ability to remove contaminants, along with practical deployment. It overviews the advantages and disadvantages of using iron-based nanomaterials and presents a vision for the future of this nanotechnology. While this is an easy-to-understand book for beginners, it provides the latest updates to experts of this field. It also opens a multidisciplinary scope for engineers, scientists, and undergraduate and postgraduate students. Although there are a number of books published on the subject of nanomaterials, not too many of them are especially devoted to iron materials, which are rather of low cost, are nontoxic, and can be prepared easily and envisaged to be used in a large variety of applications. The literature has scarce reviews on preparation of iron nanoparticles from natural sources and lacks emphasis on the different processes, such as adsorption, redox pathways, and ionic exchange, taking place in the removal of different pollutants. Reports and mechanisms on soil treatment are not commonly found in the literature. This book opens a multidisciplinary scope for engineers and scientists and also for undergraduate or postgraduate students.
Metal contamination of subsurface environments and engineered water systems can be derived from natural processes and anthropogenic activities associated with industrial processes, past weapons production, and mining works. The toxic and carcinogenic effects of uranium and chromium pose a significant risk to the environment and human health. For uranium contamination in subsurface environments, phosphate addition has been performed for in-situ immobilization, which can avoid the costs associated with pump-and-treat or excavation-based remediation strategies. The interactions of uranium and phosphate in Hanford sediments had been insufficiently explored in terms of its site-specific groundwater chemistry and aquifer sediment properties. For water treatment system, novel materials such as engineered magnetite nanoparticles have gained attention due to their promising performance in separating heavy metals from the aqueous phase. As a result, the study of the interaction between metals with either sediments or nanocomposites is imperative in designing and implementing subsurface in-situ remediation and improving water treatment processes.To investigate the impact of phosphate on the immobilization of U(VI) in Hanford sediments, batch and column experiments were performed with artificial groundwater prepared to emulate the conditions at the site. Batch experiments revealed enhanced U(VI) sorption with increasing phosphate addition. X-ray absorption spectroscopy (XAS) measurements of samples from the batch experiments found that U(VI) was predominantly adsorbed at conditions relevant to most field sites (low U(VI) loadings, 25 [mu]M), and U(VI) phosphate precipitation occurred only at high initial U(VI) (25 [mu]M) and phosphate loadings. While batch experiments showed the transition of U(VI) uptake from adsorption to precipitation, the column study was more directly relevant to the subsurface environment because of the high solid:water ratio in the column and the advective flow of water. In column experiments, more U(VI) was retained in sediments when phosphate-containing groundwater was introduced to U(VI)-loaded sediments than when the groundwater did not contain phosphate. This enhanced retention persisted for at least one month after cessation of phosphate addition to the influent fluid. Sequential extractions and laser-induced fluorescence spectroscopy (LIFS) of column sediments suggested that the retained U(VI) was primarily in adsorbed forms. These results indicate that in-situ remediation of groundwater by phosphate addition provides lasting benefit beyond the treatment period via enhanced U(VI) adsorption to sediments. U(VI) transport through sediment-packed columns have been demonstrated to be kinetically controlled and the heterogeneous system contributed to the transport behavior under different flow rates.In water treatment processes, surface-functionalized magnetite nanoparticles have high capacity for U(VI) and Cr(VI) adsorption and can be easily separated from the aqueous phase by applying a magnetic field. A surface-engineered bilayer structure enables the stabilization of nanoparticles in aqueous solution. Functional groups such as carboxylic or amine groups in stearic acid (SA), oleic acid (OA), octadecylphosphonic acid (ODP), and trimethyloctadecylammonium bromide (CTAB) coatings led to different adsorption extents towards U(VI) and Cr(VI). The adsorption of U(VI) to OA-coated nanoparticles was examined as a function of initial loading of U(VI) (5-15 [mu]M), pH (4.5 to 10), and the presence or absence of carbonate. CTAB-coated nanoparticles possess higher Cr(VI) adsorption affinity than nanoparticles with carboxyl groups (SA), due to the strong electrostatic interactions between opposite charges. For both U(VI) and Cr(VI), the entire adsorption dataset were successfully simulated with surface complexation models with a small set of adsorption reactions. The results show that the adsorption behavior was related to the changing aqueous species and properties of surface coatings on nanoparticles. The models could also capture the trend of pH-dependent surface potential that are consistent with measured zeta potentials.While developing novel materials for metal removal, the stability and treatment efficiency of the material need to be tested in real water systems. The application of CTAB-coated nanoparticles was tested with the presence of two drinking water supplies, and decreases in Cr(VI) adsorption were associated with the presence of Ca2+. When the Ca2+ concentration increased from 0 to 3.3 mM, adsorption decreased. Because only slight aggregation was associated with Ca2+ and an observed increase in zeta potential with Ca2+ addition should actually enhance Cr(VI) adsorption, the causes of inhibition of Cr(VI) by Ca2+ are not associated with particle size or surface charge. Instead it is likely that Ca2+ influences the structure of the organic bilayer on the nanoparticle surfaces in a way that decreased the availability of surface sites.The information gained from these research projects improved our understanding of metal interactions with both sediments from subsurface environments and engineered nanoparticles. It broadened knowledge of the controlling processes during the in-situ remediation of field sites and the separation of heavy metals from in water treatment. For remediation, the results illustrate the consideration of optimizing the timing and doses of phosphate addition in remediation strategies could lead to slower U(VI) release with effectively controlled levels. For water treatment the application of the material-based treatment processes needs more consideration of its stability and treatment performance with real water resources.
Iron Oxide Nanoparticles for Biomedical Applications: Synthesis, Functionalization and Application begins with several chapters covering the synthesis, stabilization, physico-chemical characterization and functionalization of iron oxide nanoparticles. The second part of the book outlines the various biomedical imaging applications that currently take advantage of the magnetic properties of iron oxide nanoparticles. Brief attention is given to potential iron oxide based therapies, while the final chapter covers nanocytotoxicity, which is a key concern wherever exposure to nanomaterials might occur. This comprehensive book is an essential reference for all those academics and professionals who require thorough knowledge of recent and future developments in the role of iron oxide nanoparticles in biomedicine. Unlocks the potential of iron oxide nanoparticles to transform diagnostic imaging techniques Contains full coverage of new developments and recent research, making this essential reading for researchers and engineers alike Explains the synthesis, processing and characterization of iron oxide nanoparticles with a view to their use in biomedicine
A pilot study conducted at the Gilze water treatment plant of Water Supply North West Brabant demonstrated that adsorptive filtration has several potential advantages over floc filtration, namely: longer filter runs due to slower head loss development; better filtrate quality; shorter ripening time; and less backwash water use. In existing groundwater treatment plants, the high iron (II) adsorption capacity of the iron oxide coated filter media makes it potentially possible to switch the governing mode of operation from floc filtration to adsorptive filtration. To achieve this two options can be considered: iron (II) adsorption under anoxic conditions followed by oxidation with oxygen-rich water; and adsorption of iron (II) in the presence of oxygen and simultaneous oxidation. The first option might be attractive specifically when two filtration steps are available.
Nanotechnology is already having a dramatic impact on improving water quality and the second edition of Nanotechnology Applications for Clean Water highlights both the challenges and the opportunities for nanotechnology to positively influence this area of environmental protection. This book presents detailed information on cutting-edge technologies, current research, and trends that may impact the success and uptake of the applications. Recent advances show that many of the current problems with water quality can be addressed using nanosorbents, nanocatalysts, bioactive nanoparticles, nanostructured catalytic membranes, and nanoparticle enhanced filtration. The book describes these technologies in detail and demonstrates how they can provide clean drinking water in both large scale water treatment plants and in point-of-use systems. In addition, the book addresses the societal factors that may affect widespread acceptance of the applications. Sections are also featured on carbon nanotube arrays and graphene-based sensors for contaminant sensing, nanostructured membranes for water purification, and multifunctional materials in carbon microspheres for the remediation of chlorinated hydrocarbons. Addresses both the technological aspects of delivering clean water supplies and the societal implications that affect take-up Details how the technologies are applied in large-scale water treatment plants and in point-of-use systems Highlights challenges and the opportunities for nanotechnology to positively influence this area of environmental protection
Contamination of aqueous environments by hazardous chemical compounds is the direct cause of the decline of safe clean water supply throughout the globe. The use of unconventional water sources such as treated wastewater will be a new norm. Emerging nanotechnological innovations have great potential for wastewater remediation processes. Applications that use smart nanomaterials of inorganic and organic origin improve treatment efficiency and lower energy requirements. This book describes the synthesis, fabrication, and application of advanced nanomaterials in water treatment processes; their adsorption, transformation into low toxic forms, or degradation phenomena, and the adsorption and separation of hazardous dyes, organic pollutants, heavy metals and metalloids from aqueous solutions. It explains the use of different categories of nanomaterials for various pollutants and enhances understanding of nanotechnology-based water remediation to make it less toxic and reusable.
Nanoscale zero-valent iron (nZVI) is one of the most extensively applied nanomaterials for groundwater and hazardous waste treatment. Despite its high potential for environmental applications, there is limited knowledge about the fundamental properties of nZVI, particularly, its structure, surface composition, and changes in these characteristics in the aqueous media as the nanoparticles interact with aqueous contaminants. This research aims to investigate the structure and surface chemistry of nZVI and to understand how these attributes influence the material's reactivity towards various water contaminants. This work first involved a detailed examination of the metallic-core-oxide-shell structure using a variety of microscopic and spectroscopic tools. It was found that the polycrystalline metallic iron nuclei are spontaneously enclosed by a disordered layer of iron oxide that is 2--3 nm thick. Using a group of water contaminants (Hg(II), Zn(II) and hydrogen sulfide) as molecular probes, it was shown that the nanoparticles were able to utilize multiple pathways including adsorption, precipitation, reduction and surface mineralization to effectively immobilize these contaminants. The observed multiplexed reactivity is imparted by the particular core-shell configuration allowing both the oxide and metal components to exert their reactive tendency without undue kinetic hindrance. The second theme of this research was to examine the structural changes experienced by Pd-doped nZVI during exposure to aqueous media. With scanning-TEM X-ray energy-dispersive spectroscopy (STEM-XEDS), the translocation of Pd from the surface to regions underneath the oxide layer and the rapid loss of the Fe(0) core due to accelerated aqueous corrosion were observed. The morphological changes resulted in a severe reduction in the reductive dechlorination rate of trichloroethylene (TCE), suggesting that the activity of Pd-doped nZVI is a dynamic function of time and particle structure. The close relationship between the structure and reactivity of nZVI is further illustrated by reactions with aqueous arsenite (As(III)). Notably, nZVI caused simultaneous oxidation and reduction of arsenite in the solid phase. Using depth-resolved high-resolution X-ray photoelectron spectroscopy (HR-XPS), multi-layered distributions of different arsenic valence states in the nanoparticles were observed, where the oxidized arsenic (As(V)) was predominantly present at the surface and the reduced form (As(0)) was located at the oxide/metal interface. The observed dual redox capability is therefore enabled by the metal core and oxide layer independently. The findings presented in this work establish that nZVI possesses more complex functionality than bulk-scale ZVI or iron oxides. The improved understanding of sequestration mechanisms studied here may inform optimal design of nZVI treatment systems and aid development of materials and new applications.
Iron Oxide Nanoparticles for Biomedical Applications: Synthesis, Functionalization and Application begins with several chapters covering the synthesis, stabilization, physico-chemical characterization and functionalization of iron oxide nanoparticles. The second part of the book outlines the various biomedical imaging applications that currently take advantage of the magnetic properties of iron oxide nanoparticles. Brief attention is given to potential iron oxide based therapies, while the final chapter covers nanocytotoxicity, which is a key concern wherever exposure to nanomaterials might occur. This comprehensive book is an essential reference for all those academics and professionals who require thorough knowledge of recent and future developments in the role of iron oxide nanoparticles in biomedicine.
Global environmental pollution and energy issue are considered as two greatest challenges that human society is facing now. Semiconductor photocatalysis is expected as a highly promising strategy for both harvesting solar energy and decomposing unwanted organics in water and air by solar light irradiation. The main problem of TiO2, the most widely studied photocatalyst material by now, is that its band gap is as wide as 3.1 eV, making it absorb only the UV part of the incident solar irradiation. Iron oxide has a proper band gap of about 2.1 eV which lies in the visible region of solar spectrum and allows utilization of 45% of the solar radiation. Together with the environmental compatibility and low cost, iron oxide is considered as a good candidate for visible light photocatalyst. For the purpose of exploiting iron oxide as effective photocatalyst, we have prepared iron oxide nanoparticles of various shapes and investigated their photocatalytic activities. The objective of the present dissertation is to develop and characterize iron oxide photocatalyst which is highly responsive to visible light. Nanostructured iron oxide and oxyhydroxide nanoparticles with various morphologies were designed and synthesized via hydrothermal route. Stabilizer molecules with different capping groups were applied in the reaction system to control the morphology of the final products. The effects attributed to the interaction between capping groups of stabilizer molecules and iron oxide surfaces. To elucidate the growth mechanism of iron oxide particles, a TEM based trace method was proposed to characterize the crystalline planes and directions of a faceted nanoparticle, and therefore its shape. The Miller indices of surface planes can be determined through coordinate transformation after the determination of the edge vectors in the TEM screen coordinate system. Methyl orange, a representative azo dye pollutant in textile industry, was chosen as the model contaminant molecule to evaluate the photocatalytic performance of the obtained powders. A systematic study, including the influence of the reaction conditions, the kinetics and the route of the oxidation of the methyl orange molecules, was carried out to explore the mechanism of photocatalytic degradation of organic molecules over iron oxide under visible light irradiation. It was found that the photodegradation of methyl orange over iron oxide was more like a semiconductor photocatalysis process, rather than a surface reaction process of ligands to metal charge transfer. Moreover, the visible light photocatalytic activities of iron oxide can be tuned by controlling the morphologies, especially the crystallographic facet of the iron oxide nanoparticles. II Post-treatment techniques were adopted to enhance the ability of iron oxide photocatalyst to decompose organic pollutant molecules. The iron oxide nanopowders were modified by loading noble metals, such as Ag and Au nanoparticles. Photocatalytic experimental results showed that the abilities of loaded metal particles to inhibit the electron-hole pair recombination depend on the relative positions between their work functions and conductive band position of the iron oxide. To overcome the problem caused by the short free distance of charge carriers inside iron oxide, nanorod arrays of iron oxide were prepared. The results show that the photocatalytic activity of iron oxides can be improved by microstructure optimization and surface modification.