Nonthermal methods

The recent addition of criteria for continuous water disinfection using UV light as described in the Pasteurized Milk Ordinance (FDA, 2009) also may lead to the develop of systems for CIP based on UV light and other so-called nonthermal methods described earlier. 

Waste may be stabilized or solidified by either thermal or non thermal treatments. Thermal treatments are ideal for destmction of organic contaminants. They reduce the volume of the waste and, hence, disposal costs. They are, however, energy intensive and more expensive than nonthermal methods, and release volatile elements that need to be contained. If the waste stream contains inorganic contaminants, the residue left after the thermal treatment is often more concentrated in these contaminants because they cannot be destroyed by such treatment. They also contaminate equipment such as furnaces and filters used during the treatment, which also ultimately need proper disposal. Thus, there is... 

Other nonthermal methods of activating the release of the Pd(0) nanoparticles... 

Abiotic nonthermal methods include chemical processes such as reaction with molten sodium, sodium naphthalide, sodium salt in amine, catalytic dechlorination, wet air oxidation, ozonation, and physical methods including adsorption, microwave plasma, and photolysis. 

Nonthermal Destruction Three processes for nonthermal destruction of PCB have been applied (a) chemical, (b) UV radiation, and (c) biological. These less-violent procedures have the potential advantage of stripping the chlorines from the PCB molecule leaving unchlorinated biphenyl and achieving a decontamination of originally PCB-contaminated oil. Thus, the oil can be reused. (Nonthermal methods are not very effective for PCB concentrations >>10,000 mg/kg.)... 

There are distinct advantages of these solvent-free procedures in instances where catalytic amounts of reagents or supported agents are used since they provide reduction or elimination of solvents, thus preventing pollution at source . Although not delineated completely, the reaction rate enhancements achieved in these methods may be ascribable to nonthermal effects. The rationalization of microwave effects and mechanistic considerations are discussed in detail elsewhere in this book [25, 193]. A dramatic increase in the number of publications [23c], patents [194—203], a growing interest from pharmaceutical industry, with special emphasis on combinatorial chemistry, and development of newer microwave systems bodes well for micro-wave-enhanced chemical syntheses. 

Pulsed electric field is another alternative to conventional methods of extraction. PEF enhances mass transfer rates using an external electrical field, which results in an electric potential across the membranes of matrix cells that minimizes thermal degradation and changes textural properties. PEF has been considered as a nonthermal pretreatment stage used to increase the extraction efficiency, increasing also permeability throughout the cell membranes. 

A striking feature of the ILs is their low vapor pressure. This, on the other hand, is a factor hampering their investigation by MS. For example, a technique like electron impact (El) MS, based on thermal evaporation of the sample prior to ionization of the vaporized analyte by collision with an electron beam, has only rarely been applied for the analysis of this class of compounds. In contrast, nonthermal ionization methods, like fast atom bombardment (FAB), secondary ion mass spectrometry (SIMS), atmospheric pressure chemical ionization (APCI), ESI, and MALDI suit better for this purpose. Measurement on the atomic level after burning the sample in a hot plasma (up to 8000°C), as realized in inductively coupled plasma (ICP) MS, has up to now only rarely been applied in the field of IE (characterization of gold particles dissolved in IE [1]). This method will potentially attract more interest in the future, especially, when the coupling of this method with chromatographic separations becomes a routine method. 

Increasingly stringent environmental regulations imposed on both the military and civilian sectors has created a growing demand for alternative abatement methods for a variety of hazardous compounds. One alternative, the nonthermal plasma, shows promise of providing an efficient means for the destraction of dilute concentrations of hazardous air pollutants. Promising results have been obtained for toluene, methylene chloride, and dichlorodifluoromethane in air at concentrations of a few hundred parts per million. The device has been operated at voltages up to 30 kV, pulse repetition rates up to 1.4 kHz, and flow rates up to 60 1/min (Korzekwa et al., 1998). 

The main goal of destructive methods is to conveniently alter the physicochemical characteristics of the spent material before its final disposal. These processes can be classified as thermal and nonthermal processes. 

Nonthermal processes There are a number of chemical treatment methods developed and used for the processing of hazardous chemical waste. These methods are briefly discussed in the next sections. 

The distillation method of moisture determination requires collection and determination of the water evolved from the coal when the sample is heated in a boiling solvent that is itself immiscible with water. The solution and extraction methods require either solvent extraction of the water from the coal (followed by subsequent determination of the water content of the solvent) or use of a standard reagent that will exhibit differences in concentration by virtue of the water in the coal. A nonthermal solvent method of determining moisture involves the use of an extraction procedure in which the coal is shaken with a solvent that extracts the water from the coal. The degree of change in some physical property of the solvent, such as density, is then used as a measure of the water extracted. 

Bauer (1999b) found that the alkamide, dodeca-2 ,4E,8Z, 1 OE/Z-tetra-enoic acid isobutylamide, level was influenced by the preparation method. Nonthermal preparations appeared to have slightly higher levels of the tested alkamide than thermally treated products. Thus, the drying process may not be the best method for preparing Echinacea products. Pressing of the plant material to obtain an expressed juice is a common preparation method however, preservation of the juice with ethanol is required. Direct ethanol extraction of the plant material can be used in place of the pressing operation. 

The thermal polymers are incapable of mimicing a peptide or protein to the exact extent that the product of a stepwise synthesis does. An exact duplication of a functional protein, however, does little to elucidate the reason for its activity modification and study of the effect on activity are necessary. Systematic synthetic modification of polymeric models is easily achieved in the case of thermal polyamino acids. They are prepared with much ease and in large numbers, and their quantitative compositions can be regulated and controlled simply. Examples are already at hand to illustrate the use of the thermal method to evaluate qualitatively the kinds of amino acid residue that are necessary for, contributory to, or detrimental to, activity. Such studies augment information from enzymes and from nonthermal models. 

The observed rate accelerations and sometimes altered product distributions compared to classical oil-bath experiments have led to speculation on the existence of specific or nonthermal microwave effects. " Historically, such effects were claimed when the outcome of a synthesis performed under microwave conditions was different from that of the conventionally heated counterpart. When reviewing the present literature, it appears that most scientists now agree that in the majority of cases the reason for the observed rate enhancements is a purely thermal/kinetic effect. Even though for the industrial chemist this discussion seems largely irrelevant, the debate on microwave effects is undoubtedly going to continue for many years in the academic world. Today, microwave chemistry is as reliable as the vast arsenal of synthetic methods that preceded it. Microwave heating not only reduces reaction times significantly, but is also known to reduce side reactions, increase yields, and improve reproducibility. 

Very little is known about the nature of rotational energy transfer in a collision between an electronically excited molecule and a ground-state atom or molecule. In the few reported studies the experimental method is fundamentally the same as that described at the beginning of Section III.A. An initial rotational distribution is established by narrow-band excitation. The fluorescence emission contour is recorded twice, under collision-free and thermal equilibrium conditions, and then again under conditions such that there is one collision during the lifetime of the excited state. The differences in the rotational contours of the three emission spectra are then used to infer the pathway of rotational energy transfer, and the rate of that transfer. Some examples of the emission spectra recorded under these conditions are shown in Fig. 22. Because of the small spacings between the rotational levels of polyatomic molecules most excitation sources prepare nonthermal superpositions of rotational states rather than pure rotational states, and this complicates interpretation of the observations. 

Electron impact ionization of the parent molecule is only one of several important ion formation processes in nonthermal plasmas. Secondary processes such as electron impact ionization of neutral fragments produced by dissociation of the parent molecule and ion-molecule reactions are other mechanisms contributing to the formation of plasma ions. It is interesting to compare ion abundances in a realistic plasma with the ion abundances predicted from electron impact ionization cross sections measured under single-collision conditions. Although mass spectrometry of plasma ions is a known and well-developed diagnostic method (Osher, 1965 Drawln, 1968 Schmidt et al., 1999), its application to plasmas for thin-film deposition is not very common. The main reasons are deleterious effects of insulating deposits on the ion collection orifice (which connects the mass spectrometer to the plasma) and on the ion transfer optics, which render it... 

Significantly, microwave processing frequently leads to noticeable reduction in reaction times and higher yields. The rate improvements observed may simply be a consequence of the high reaction temperatures that can be achieved rapidly by use of this nonclassical heating method, or may result from the involvement of so-called specific or nonthermal microwave effects (cf Chapter 4 in this book). 

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