Chemical pretreatment method

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. 

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. 

Suhardi VSH, Prasai B, Samaha D, Boopathy R. Combined biological and chemical pretreatment method for lignocellulosic ethanol production from energy cane. Renewable Bioresources 2013 1 1-5. 

To fully assess the practical, real-world applicability of this automated online chemical pretreatment method, accuracy, detection capability, and stability tests were carried out. Accuracy was evaluated by analyzing a seawater certified reference material. The average of four separate analyses of the NASS 5 ocean seawater are shown in Table 20.4. All the data generated are well within the error of the certified values except for zinc, which is approximately three-fold higher. It is well-recognized that zinc is a notoriously difficult element to determine by ICP-MS because of contamination issues. For that reason, it is likely that the NASS 5 certified reference material (CRM) was contaminated with zinc from an external source before or during the analysis. 

In general, the pretreatment of the substrates is accomplished by cleaning the surface by means of solvents such as 2-butanon, isopropanol, or propanone. Alternatively, it is possible to clean the surfaces with water and tensides. The aim of using these wet-chemical pretreatment methods is to remove contaminations that are located on the surface and influence the performance of the bond between the polymer adhesive or coating and the substrate negatively. 

Beside wet-chemical pretreatment methods, mechanical pretreatments are widely used and comprise sandblasting and grinding. Sandblasting is carried out by means of a transportable... 

Silverstein, R. A., Y. Chen, R. R. Sharma-Shivappa, M. D. Boyette and J. Osborne (2007). A comparison of chemical pretreatment methods for improving sacchariUcation of cotton stalks. Bioresource Technology 9S(16) 3000-3011. 

The chemical pretreatment methods mentioned are mostly used for TPOs, but in some cases can also be effective when used on polyamide (PA), polybutylene terephthalate (PBT), or other crystalline polymers, as well as some blends like poly(phenylene oxide)/polyamide (PPO/PA), are flamed. As a possible future trend, research is currently underway (plasma polymerization) attempting to combine a pretreatment for adhesion and to provide the surface conductivity on necessary on plastic parts for acceptable electrostatic application (15). 

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. 

Methods for recycling used plastic materials are reviewed. Emphasis is placed on the research projects into chemical recycling methods for used plastics at the Leuna location. These include development of a process for the thermaL thermooxidative pretreatment of used plastic materials, utilisation of pretreated used plastic materials in the visbreaker by gasification and by hydrogenation and the production of wax oxidates from pretreated used plastics. The results are discussed. 

Assays of ciguatoxin. Determination of ciguatoxin levels in fish was carried out in many laboratories by mouse assays. Enzyme immunoassay to screen inedible fish has been proposed by Hokama (9). No specific chemical assay has been developed, as information on functional groups suitable for fluorescence labeling is not available. Analyses conducted in the authors laboratory on remnant fish retrieved from patients meals indicated that ciguatoxin content as low level as 1 ppb could cause intoxication in adults. An extremely high sensitivity and a sophisticated pretreatment method will be required for designing a fluorometric determination method for the toxin. 

Scale prevention methods include operating at low conversion and chemical pretreatment. Acid injection to convert COs to CO2 is commonly used, but cellulosic membranes require operation at pH 4 to 7 to prevent hydrolysis. Sulfuric acid is commonly used at a dosing of 0.24 mg/L while hydrochloric acid is to be avoided to minimize corrosion. Acid addition will precipitate aluminum hydroxide. Water softening upstream of the RO By using lime and sodium zeolites will precipitate calcium and magnesium hydroxides and entrap some silica. Antisealant compounds such as sodium hexametaphosphate, EDTA, and polymers are also commonly added to encapsulate potential precipitants. Oxidant addition precipitates metal oxides for particle removal (converting soluble ferrous Fe ions to insoluble ferric Fe ions). 

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 ... 

For many of the organic materials in seawater, some form of chemical pretreatment is necessary before analysis is possible. The obvious cases are the hydrolysis of polysaccharides and proteins before the analysis for monomeric constituents, and the formation of volatile derivatives to permit analysis by gas chromatography. These methods will be discussed further in Chap. 9. 

Membrane pretreatment can improve the feed water quality and reduce particulate matter to a greater degree than other pretreatment methods. This reduces the required cleaning frequency of the downstream membranes and the amount of cleaning chemicals that are required and subsequently disposed of (Pearce 2007). 

Alternatively, for an ABS polymer, a photocatalytic reaction can be applied as a pretreatment method prior to electroless plating. Unlike the conventional wet chemical method, this method can improve the adhesion strength without severe morphological changes (96). The pretreatment method uses a photocatalytic reaction in a TiC>2 dispersed solution. 

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