The overall goal of this project was to develop reactive membrane barriers--a new and flexible technique to contain and stabilize subsurface contaminants. Polymer membranes will leak once a contaminant is able to diffuse through the membrane. By incorporating a reactive material in the polymer, however, the contaminant is degraded or immobilized within the membrane. These processes increase the time for contaminants to breakthrough the barrier (i.e. the lag time) and can dramatically extend barrier lifetimes. In this work, reactive barrier membranes containing zero-valent iron (Fe°) or crystalline silicotitanate (CST) were developed to prevent the migration of chlorinated solvents and cesium-137, respectively. These studies were complemented by the development of models quantifying the leakage/kill time of reactive membranes and describing the behavior of products produced via the reactions within the membranes. First, poly(vinyl alcohol) (PVA) membranes containing Fe° and CST were prepared and tested. Although PVA is not useful in practical applications, it allows experiments to be performed rapidly and the results to be compared to theory. For copper ions (Cu{sup 2+}) and carbon tetrachloride, the barrier was effective, increasing the time to breakthrough over 300 times. Even better performance was expected, and the percentage of the iron used in the reaction with the contaminants was determined. For cesium, the CST laden membranes increased lag times more than 30 times, and performed better than theoretical predictions. A modified theory was developed for ion exchangers in reactive membranes to explain this result. With the PVA membranes, the effect of a groundwater matrix on barrier performance was tested. Using Hanford groundwater, the performance of Fe° barriers decreased compared to solutions containing a pH buffer and high levels of chloride (both of which promote iron reactivity). For the CST bearing membrane, performance improved by a factor of three when groundwater was used in place of deionized water. The performance of high density polyethylene (HDPE) membranes containing Fe° was then evaluating using carbon tetrachloride as the target contaminant. Only with a hydrophilic additive (glycerol), was the iron able to extend lag times. Lag times were increased by a factor of 15, but only 2-3% of the iron was used, likely due to formation of oxide precipitates on the iron surface, which slowed the reaction. With thicker membranes and lower carbon tetrachloride concentrations, it is expected that performance will improve. Previous models for reactive membranes were also extended. The lag time is a measurement of when the barrier is breached, but contaminants do slowly leak through prior to the lag time. Thus, two parameters, the leakage and the kill time, were developed to determine when a certain amount of pollutant has escaped (the kill time) or when a given exposure (concentration x time) occurs (the leakage). Finally, a model was developed to explain the behavior of mobile reaction products in reactive barrier membranes. Although the goal of the technology is to avoid such products, it is important to be able to predict how these products will behave. Interestingly, calculations show that for any mobile reaction products, one half of the mass will diffuse into the containment area and one half will escape, assuming that the volumes of the containment area and the surrounding environment are much larger than the barrier membrane. These parameters/models will aid in the effective design of barrier membranes.

A polyvinyl alcohol (PVA) membrane containing iron (Fe0) particles was developed and tested as a model barrier for contaminant containment. Carbon tetrachloride, copper (Cu2+), nitrobenzene, 4-nitroacetophenone, and chromate (CrO4 2- ) were selected as model contaminants. Compared with a pure PVA membrane, the Fe0/PVA membrane can increase the breakthrough lag time for Cu2+ and carbon tetrachloride by more than 100 fold. The increase in the lag time was smaller for nitrobenzene and 4-nitroacetophenone which stoichiometrically require more iron and for which the PVA membrane has a higher permeability. The effect of Fe0 was even smaller for CrO4 2- because of its slow reaction. Forty-five percent of the iron, based on the content in the dry membrane prior to hydration, was consumed by reaction with Cu2+ and 19% by reaction with carbon tetrachloride. Similarly, 25%, 17%, and 6% of the iron was consumed by nitrobenzene, 4-nitroacetophenone, and CrO4 2-, respectively. These percentages approximately double when the loss of iron during membrane hydration is considered. The permeability of the Fe0/PVA membrane after breakthrough was within a factor of three for that of pure PVA, consistent with theory. These results suggest that polymer membranes with embedded Fe0 have potential as practical contaminant barriers.

Remediation of groundwater is complex and often challenging. But the cost of pump and treat technology, coupled with the dismal results achieved, has paved the way for newer, better technologies to be developed. Among these techniques is permeable reactive barrier (PRB) technology, which allows groundwater to pass through a buried porous barrier that either captures the contaminants or breaks them down. And although this approach is gaining popularity, there are few references available on the subject. Until now. Permeable Reactive Barrier: Sustainable Groundwater Remediation brings together the information required to plan, design/model, and apply a successful, cost-effective, and sustainable PRB technology. With contributions from pioneers in this area, the book covers state-of-the-art information on PRB technology. It details design criteria, predictive modeling, and application to contaminants beyond petroleum hydrocarbons, including inorganics and radionuclides. The text also examines implementation stages such as the initial feasibility assessment, laboratory treatability studies (including column studies), estimation of PRB design parameters, and development of a long-term monitoring network for the performance evaluation of the barrier. It also outlines the predictive tools required for life cycle analysis and cost/performance assessment. A review of current PRB technology and its applications, this book includes case studies that exemplify the concepts discussed. It helps you determine when to recommend PRB, what information is needed from the site investigation to design it, and what regulatory validation is required.

Among the various nanomaterials, inorganic nanoparticles are extremely important in modern technologies. They can be easily and cheaply synthesized and mass produced, and for this reason, they can also be more readily integrated into applications. Inorganic Nanoparticles: Synthesis, Applications, and Perspectives presents an overview of these special materials and explores the myriad ways in which they are used. It addresses a wide range of topics, including: Application of nanoparticles in magnetic storage media Use of metal and oxide nanoparticles to improve performance of oxide thin films as conducting media in commercial gas and vapor sensors Advances in semiconductors for light-emitting devices and other areas related to the energy sector, such as solar energy and energy storage devices (fuel cells, rechargeable batteries, etc.) The expanding role of nanosized particles in the field of catalysis, art conservation, and biomedicine The book’s contributors address the growing global interest in the application of inorganic nanoparticles in various technological sectors. Discussing advances in materials, device fabrication, and large-scale production—all of which are urgently required to reduce global energy demands—they cover innovations in areas such as solid-state lighting, detailing how it still offers higher efficiency but higher costs, compared to conventional lighting. They also address the impact of nanotechnology in the biomedical field, focusing on topics such as quantum dots for bioimaging, nanoparticle-based cancer therapy, drug delivery, antibacterial agents, and more. Fills the informational gap on the wide range of applications for inorganic nanoparticles in areas including biomedicine, electronics, storage media, conservation of cultural heritage, optics, textiles, and cosmetics Assembling work from an array of experts at the top of their respective fields, this book delivers a useful analysis of the vast scope of existing and potential applications for inorganic nanoparticles. Versatile as either a professional research resource or textbook, this effective tool elucidates fundamentals and current advances associated with design, characterization, and application development of this promising and ever-evolving device.

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.