Physical Pretreatment Methods

Hydroth nnal High pressure steaming Expansion Extrusion Pyrolysis 

Schematic overview of different methods for pretreatment of lignocellulosic 

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The specific purpose of this chapter is to describe the chemical and physical pretreatment methods required for nickel-chromium plating wastewater, to describe the upgrades needed by a municipal wastewater treatment system to manage this waste, and to relate the methods and upgrades to the operation of the total treatment system. Special emphasis is placed on presentation of the following ... 

In applying these general criteria, one should focus on the intended application. In wastewater treatment applications, filtration can be applied at various stages. It can be applied as a pretreatment method, in which case the objective is often to remove coarse, gritty materials from the waste-stream. This is a preconditioning step for waste waters which will undergo further chemical and physical treatment downstream. 

The mechanical properties of composites are mainly influenced by the adhesion between matrix and fibers of the composite. As it is known from glass fibers, the adhesion properties could be changed by pretreatments of fibers. So special process, chemical and physical modification methods were developed. Moisture repel-lency, resistance to environmental effects, and, not at least, the mechanical properties are improved by these treatments. Various applications for natural fibers as reinforcement in plastics are encouraged. 

The problem of adhesion between a polymer and a metal is strongly dependent on the specific type of polymer and metal involved, as well as on the deposition process under which the interface between the two is formed. In order to improve adhesion, different pretreatment methods can be used, but the development of such techniques requires detailed information about metal-polymer interfaces. Particularly, in the case of thin metal films deposited by physical vapor deposition (PVD) in ultra high vaccum (UHV), X-ray and ultraviolet photoelectron spectroscopy (XPS and UPS) have been used to obtain chemical information about initial film growth modes,... 

Grinding, brushing or sanding (with the exception of the above-mentioned Saco method) do not cause chemical modifications of the material s surface. A clean surface results with a characteristic structure corresponding to the composition of the material, as shown in Figure 7.6. Therefore, physical and chemical pretreatment methods are aimed at the chemical modification of the surfaces. Thus, on the one hand it is possible to further enhance the adhesive forces for extremely high demands on bonded joints, and on the other hand, to make poorly bondable material (e.g., plastics) bondable at all. Since physical methods are mainly used in bonding of plastics, they are described in Section 9.2.4. 

Many pretreatment techniques are used in practice (Table 8.2). The normal physical method used to improve the adhesive strength of the coating to the substrate is to slightly roughen the surface by solvent treatment, abrasion, or blasting. Some plastics (e.g., polyolefins) require special pretreatment methods processes that modify the surface molecular layers of the plastic to increase their polarity have proved suitable (e.g., flaming, immersion in an oxidizing acid, immersion in a benzophenone solution with UV irradiation, corona treatment, plasma treatment). 

H. Fung, J. Tang, D.S. Mattinson, and J.K. FeUman, Microwave and spouted bed drying of frozen blue berries The effect of drying and pretreatment methods on physical properties and retention of flavour volatiles, J. Food Process. Pres., 23(6) 463-479 (1999). 

There is a common requirement in water analysis to separate the dissolved or suspended component in the sample before analysis. This is usually achieved by a physical separation step. Filtration is the most commonly used sample pretreatment method. Membrane and glass fiber filters are available in a variety of pore sizes and membranes are available in different materials. Water analysts normally use GF/C glass fiber filters for suspended solids determinations and 0.45 pm cellulose-based filters to define the soluble/ insoluble fraction in samples. However, all filters and filtration apparatus must be checked to confirm... 

Chemical pretreatment methods have an advantage of being easily applied as soon as it is required (Mohan, 2008). However, one of the inherent disadvantages of chemical treatment methods, as compared to physical methods, is that they are additive processes (Metcalf Eddy, 1991). As a result, there is usually a positive increase in the dissolved constituents in the wastewater. This additive aspect is in contrast to physical and biological treatment methods that may be described as being subtractive because material is removed from the wastewater. Another drawback of chemical methods is that they are all intensive in operating costs (Metcalf Eddy, 1991). The costs of some of the chemicals are tied to the cost of energy and thus can be expected to increase similarly. 

Filtration is an important unit operation in the treatment of many industrial waste streams. In the industry sources described in this chapter, filtration is often relied upmi for the removal of coarse and fine particles, and as both a pietFeatment and posttreatment step. One must recognize however, that most filtration operations involve physical separation, or in some instances, are combined as a part of biological treatment or with chemical pretreatment methods as described in earlier chapters. Because many of the waste streams described are highly toxic in nature, chemical techniques including extraction, precipitation and others are the primary methods of treatment. The references cited below provide more in depth coverage of this subject along with additional examples on the use of filtration with chemical treatment methods. 

With some suspensions it is not possible to use chemical pretreatments, typical examples are in the processing of pharmaceutical and food products. Under such circumstances physical pretreatments may be employed to beneficially modily suspension properties, however, many of these methods are either relatively expensive to implement or only suitable for use in specialised situations and thus have limited application. A useful summary is provided by Hermia (1980). 

Physical pretreatment also has an important role to play not just to improve the performance of filters in general but in the case of vacuum filters it may even decide whether or not a vacuum filter can be used at all. Without such pre-treatment, a generally more expensive pressure filter may have to be used. Pretreatment may include crystallization, freezing, temperature adjustment, thermal treatment or ageing, but the three main methods used with vacuum filters are ... 

Based on Fahma et al. (2010) nanofiber from palm oil EFB, which also known as cellulose nanofiber, are produce by hydrolyzing oil palm empty fruit bunches fiber with sulfuric acid and through other chemical and physical process. Method describes EFB cellulose nanofiber isolation comprises two process steps, pretreatment and bleaching, and acid hydrolysis, will be described further. 

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