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"Accidental spills and past improper disposal practices of chlorinated solvents have led to widespread soil and groundwater contamination. Drinking water standards for trichloroethylene (TCE) and many other chlorinated organic contaminants are in the range of 5 μg/L and these compounds have received extensive regulatory attention because these compounds are often carcinogenic and neurotoxic. Direct injection of reactive nanoscale zerovalent iron particles (NZVI) is considered to be a promising approach for remediation of chlorinated compounds. NZVI is a strong reducing agent that can effectively transform TCE and other chlorinated organic compounds to non-toxic end products. The objective of the research was to assess various biogeochemical conditions on the reactivity of iron nanoparticles in particular sulfidation of NZVI for remediation of TCE. In addition, the feasibility of coupled NZVI-based remediation and bioremediation using polymer-coated bimetallic NZVI and a dechlorinating mixed culture consortia (KB-1) was investigated. We demonstrated that the extent of sulfidation of NZVI enhances the rate of dechlorination of TCE compared to non-sulfidated NZVI, and this enhancement depends on the Fe/S molar ratio of the sulfidated NZVI particles. Batch experiments where TCE was reacted with NZVI sulfidated to different extents (Fe/S molar ratios 0.62 to 66) showed that the surface-area normalized first-order TCE degradation rate constant increased 40 fold compared to non-sulfidated NZVI. FX-ray photoelectron spectroscopy analyses showed formation of a surface layer of FeS and FeS2. This indicates sulfide ions reacted with NZVI iron sulfide on surface of S-NZVI. We propose that more electrons are preferentially conducted from sulfidated NZVI than from unamended NZVI to TCE, likely because of greater binding affinity of TCE on the reactive sites of the iron sulfide outer layer. Aging of sulfidated iron nanoparticles (S-NZVI) and their influence on rate of TCE dechlorination was compared to the aged non-sulfidated NZVI. Long-term experiments indicate that pseudo-first order H2 evolution rate constant for non-sulfidated NZVI was 0.092 ± 0.005 d-1 and was significantly higher than the S-NZVI (Fe/S=25) at 0.051 ± 0.005 h-1. This difference in hydrogen evolved corresponds to the amount of reactive Fe(0) consumed in the absence of TCE. To further support, the efficacy of long-term reactivity S-NZVI batch TCE degradation experiment with anaerobically aged S-NZVI (40 days) degraded significantly more TCE than the non-sulfidated NZVI. Bimetallic, palladium-doped iron nanoparticles (Pd-NZVI) are capable of rapid transformation of higher initial TCE concentration, and the ability to form rapid H2 (electron donor for bacteria) may facilitate TCE biodegradation. Dehalococcoides are the only species of bacteria that are capable of degrading TCE completely to ethene under anaerobic conditions. Therefore, we investigated the interaction of carboxymethyl cellulose (CMC) stabilized palladium (Pd-NZVI) on the dechlorinating mixed culture KB-1 for reductive dechlorination of 1, 2 dichloroethane (DCA). Results suggest that systems with CMC alone as a sole carbon source and electron donor were capable of degrading 1, 2-DCA, and methane formation. The microcosms with KB-1 and polymer coated Pd-NZVI degraded 1, 2-DCA at a significantly higher rate constant compared to KB-1 and CMC systems. In addition, methanogenesis by KB-1 showed no statistically significant difference in the methane formation rate constants between Pd-CMC-NZVI and CMC only systems.Overall, this research demonstrates NZVI reactivity towards TCE and its longevity (efficacy) under anaerobic conditions can be enhanced with sulfidation. In addition, this research also shows that CMC stabilized bimetallic NZVI, is not inhibitory to Dehalococcoides spp. and could promote complete bioremediation." --
This is the first complete edited volume devoted to providing comprehensive and state-of-the art descriptions of science principles and pilot- and field-scaled engineering applications of nanoscale zerovalent iron particles (NZVI) for soil and groundwater remediation. Although several books on environmental nanotechnology contain chapters of NZVI for environmental remediation (Wiesner and Bottero (2007); Geiger and Carvalho-Knighton (2009); Diallo et al. (2009); Ram et al. (2011)), none of them include a comprehensive treatment of the fundamental and applied aspects of NZVI applications. Most devote a chapter or two discussing a contemporary aspect of NZVI. In addition, environmental nanotechnology has a broad audience including environmental engineers and scientists, geochemists, material scientists, physicists, chemists, biologists, ecologists and toxicologists. None of the current books contain enough background material for such multidisciplinary readers, making it difficult for a graduate student or even an experienced researcher or environmental remediation practitioner new to nanotechnology to catch up with the massive, undigested literature. This prohibits the reader from gaining a complete understanding of NZVI science and technology. In this volume, the sixteen chapters are based on more than two decades of laboratory research and development and field-scaled demonstrations of NZVI implementation. The authors of each chapter are leading researchers and/or practitioners in NZVI technology. This book aims to be an important resource for all levels of audiences, i.e. graduate students, experienced environmental and nanotechnology researchers, and practitioners evaluating environmental remediation, as it is designed to involve everything from basic to advanced concepts.
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.
Examines the suitability of nanoscale zero-valent iron (ZVI) for degradation of agrochemicals. This book identifies by-products produced from the ZVI-mediated degradation process of particular contaminants, and explains the reaction mechanism by which ZVI degrades a chosen contaminant.
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
Over the past 4 billion years, microorganisms have contributed to shaping the earth and making it more habitable for higher forms of life. They are remarkable in their metabolic diversity and their ability to harvest energy from oxidation and reduction reactions. Research on these microbiological processes has led to the newly evolving fields of geomicrobiology and biogeochemistry, linking the geosphere and the biosphere. This volume of the Soil Biology series provides an overview of the biogeochemical processes and the microorganisms involved, with an emphasis on the industrial applications. Topics treated include aspects such as bioremediation of contaminated environments, biomining, biotechnological applications of extremophiles, subsurface petroleum microbiology, enhanced oil recovery using microbes and their products, metal extraction from soil, soil elemental cycling and plant nutrition.