Environmental remediation applications

Shoemaker SH, Greiner JF, Gillham RW. Permeable reactive barriers. In Bodocsi A, Ryan ME, Rumer RR, eds. Barrier Containment Technologies for Environmental Remediation Applications (Final Report of the International Containment Technology Workshop, Baltimore, MD, 29-31 August 1995). New York Wiley, 1995 301-353. 

Daylight Photocatalysis by Carbon-Modified Titanium Dioxide. Titanium tetrachloride precursor hydrolyzed with nitrogen bases to yield (surprisingly) C-doped (instead of N-doped) Ti02. Study oriented toward environmental remediation applicability. 309... 

Barrier Containment Technologies for Environmental Remediation Applications, John Wiley Sons, Inc. New York, 1995. 

Nano BaTiOs, like nano-SrTiOs prepared by coprecipitation, can effectively remove Cu from solutions by adsorption and can be used for environmental remediation applications [61]. 

Bodocsi, A., Michael E. Ryan, and Ralph R. Rumer, Eds., Barrier Containment Technologies for Environmental Remediation Applications, John Wiley Sons, New York, 1995. 

Despite the research progress mentioned above, none of the above techniques has been widely adopted commercially for environmental remediation applications due to one or more limitations of each method. For example, incineration of concentrated chlorinated organic compounds requires special treatments to remove the HCl generated. HCl corrodes the equipment if not removed. In addition, incineration of PCBs and other chlorinated organics often produces more toxic compounds (e.g. dioxins) if it is not carefully controlled. Thus, Erickson et al (87) reported that combustion of PCBs leads to the formation of small amounts of the most highly toxic polychlorinated dibenzofurans (PCDFs) and polychlorinated dibenzodioxins (PCDDs). Moreover, disposal of chlorinated solvents, neat PCBs, and related chemicals by... 

Katepalli H, Bikshapathi M, ShtirmaCS, VermaN, Shaima A (2011) Synthesis of hierarchictd fabrics by electrospinning of PAN nanofibers on activated caibon microfibeis for environmental remediation applications. Chem Eng J 171(3) 1194-1200. doi 10.1016/j.cej.2011.05.025... 

One of the major breakthroughs in nanotechnology is the use of nanomaterials as catalysts for environmental applications [149]. Nanomaterials have been developed to improve the properties of catalysts, enhance reactivity towards pollutants, and improve their mobility in various environmental media [150]. Nanomaterials offer applications to pollution prevention through improved catalytic processes that reduce the use of toxic chemicals and eliminate wastes. Nanomaterials also offer applications in environmental remediation and, in the near future, opportunities to create better sensors for process controls. 

Forrester Environmental Services, Inc., has developed a group of technologies for the stabilization of wastes containing heavy metals, such as lead, cadmium, arsenic, mercury, copper, zinc, and antimony. These technologies have been used in both industrial pollution prevention and remediation applications. One version of the technology involves the use of water-soluble phosphates and various complexing agents to produce a less soluble lead waste. This process results in a leach-resistant lead product. 

Foster-Miller has developed robotics technologies with applications to environmental remediation. These robots include FERRET, a materials handling robot Mini-Mucker, a remotely operated dump truck Lemming, a robot designed for the retrieval of unexploded ordnance and TALON, used for explosives detection and ordnance removal. Foster-MiUer can also custom-design robots for specialized tasks. Foster-MiUer s robotics technologies are commercially available. 

This technology is currently commercially available from the MIOX Corporation, an affiliate of Los Alamos Technical Associates, Inc. While the MIOX system for disinfection applications is fully commercialized, applications for environmental remediation and Resource Conservation and Recovery Act (RCRA) waste treatment are still in the early stages of development. 

Sobolev, I. A., Stefanovsky, S. V., Knyazev, O. A., Lashtchenova, T. N., Vlasov, V. I. Lopukh, D. B. 1997a. Application of the cold crucible melting for production of rock-type waste-forms. In Baker, R., Slate, S. Benda, G. (eds) Proceedings of the Sixth International Conference on Radioactive Waste Management and Environmental Remediation ICEM 97. The American Society of Mechanical Engineers, New York, 265-269. 

Another major theme is the application of nanocrystalline Ti02 as a photocatalyst for environmental remediation. During the past several decades a broad research community composed of chemists, engineers, and materials scientists has developed technologies that use 2 as the light absorber and primary oxidant to mineralize organic pollutants in water- and air-streams. Three chapters in this... 

As stated, we will take a different route despite the tradition of beginning with a discussion of the molecules that constitute polyurethanes. We want to investigate the effects on the fluids that pass through or come into contact with polyurethane. In the simplest example, if air contaminated by polycyclic hydrocarbons passes through polyurethane foam, the concentration of hydrocarbons will change. In that sense, the foam is not truly inert. By the application of certain techniques, we will discuss how this effect can be controlled to provide an environmental remediation mechanism. We will discuss this effect in detail in this and subsequent chapters. 

In this first chapter, we seek to reinforce this perspective by including a series of case studies. We will propose problems in various areas of investigation and include specific examples of environmental remediation and advanced medical research issues addressed by polyurethanes in one form or another. While each example deals with a specific discipline, it is important to recognize that we have chosen all the examples in this chapter as surrogates with much broader applicabilities beyond the specific fields cited in the examples. 

Once a polymer is fuUy saturated, the physical tests described above can be conducted with confidence. Naturally, minimizing the evaporation of water should be considered. The one exception in this new category of testing is flow of water through the foam. This is not covered in the standard but will be very important for some applications, particularly in environmental remediation. If the intent is to build a biofilter or a continuous flow enzyme reactor, we must know the hydrodynamic properties of the materials we produce. Since polyurethanes are rarely used in these environments, the flow of water even through a reticulated foam is not described by the manufacturers. Furthermore, if we are to make composites of reticulated foams, the amount of polymer grafted to the surface will have a dominating effect on the flow of water. In a later chapter, we will describe our work in this area. 

Abiotic environmental reductants are not as well characterized as the oxidants because there are fewer remediation applications of reductants, and natural reducing environments are characterized by especially complex biogeochemistry. The most familiar natural reduc-... 

Several of the key issues are reflected in the debate over the appropriate use of pe to describe redox conditions in natural waters (129-131). The parameter is defined in terms of the activity of solvated electrons in solution (i.e., pe = - log e ), but the species e aq does not exist under environmental conditions to any significant degree. The related concept of pe (132), referring to the activity of electrons in the electrode material, may have a more realistic physical basis with respect to electrode potentials, but it does not provide an improved basis for describing redox transformations in solution. The fundamental problem is that the mechanisms of oxidation and reduction under environmental conditions do not involve electron transfer from solution (or from electrode materials, except in a few remediation applications). Instead, these mechanisms involve reactions with specific oxidant or reductant molecules, and it is these species that define the half-reactions on which estimates of environmental redox reactions should be based. 

For the same reason as above, excess solvent molecules in the cavitation bubble also seriously limit the applicability of many volatile organic solvents as a medium for sonochemical reactions [2,25,26]. In fact, water becomes a unique solvent in many cases, combining its low vapor pressure, high surface tension, and viscosity with a high yield of active radical output in solution. Its higher cavitation threshold results in subsequently higher final temperatures and pressures upon bubble collapse. Most environmental remediation problems deal with aqueous solutions, whereas organic solvents are mostly used in synthesis and polymer modifications processes. 

Although the majority of interest in remediation applications of corrodable metals revolves around Fe°, other possibilities have been investigated, including magnesium, tin, and zinc. The bulk of this work has used Zn° as a model system for comparison with Fe° (e.g., Refs. 95, 96, 125, and 126), but a few studies have surveyed a range of metals as possible alternatives to Fe° in environmental applications other than PRBs (e.g., Refs. 127 and 128). 

Our review here will highlight the role of semiconductor-initiated photochemistry as an environmental remediation method for the treatment of organic chemicals. While the role of sunlight-induced photochemistry in creating environmental problems such as urban photochemical smog and the polar ozone holes has been well documented, the potential applications of photochemical methods in resolving environmental problems are less obvious. 

Although nanoscale materials promise to revolutionize many of our industries including electronics, health care, energy and more, the near term uses are in environmental remediation and green chemistry applications. One reason for this is that nanomaterials possess unique properties as adsorbents and catalysts, because (1) they possess high surface areas with large surface to bulk ratios so that the nanomaterial is used efficiently (2) nanocrystals have... 

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