Extraction methods chemical

This chapter includes introduction of fibers from different agro-residual sources, extraction methods, chemical constituents and properties of fibers and physical and chemical treatments applied to fibers to provide higher quahty reinforcement elements of biocomposites. Due to the broadness of the scope, this chapter will undoubtedly be unfinished, but it will hopefully provide guidance to researchers who want to contribute to the environment and to the rural society, together with the composite industry. 

Chemometrics is the discipline which deals wdth the application of statistical and, in a more general sense, of mathematical methods to chemical data. Chemometric methods are used for the extraction of chemical information from chemical data. 

Physticochemical coiiatrainla Further constraints can be imposed on the atoms and bonds of the reaction center, such as those physicochemical factors calculated by the PETRA package (see Section 7.1). For example, the partial charges calculated by the PEOE method can be used to extract the chemically feasible reaction from the two conceivable ones as illustrated in Figure 10.3-11. 

Analytical and test methods for the characterization of polyethylene and PP are also used for PB, PMP, and polymers of other higher a-olefins. The C-nmr method as well as k and Raman spectroscopic methods are all used to study the chemical stmcture and stereoregularity of polyolefin resins. In industry, polyolefin stereoregularity is usually estimated by the solvent—extraction method similar to that used for isotactic PP. Intrinsic viscosity measurements of dilute solutions in decahn and tetraHn at elevated temperatures can provide the basis for the molecular weight estimation of PB and PMP with the Mark-Houwiok equation, [rj] = KM. The constants K and d for several polyolefins are given in Table 8. 

Recovery of Uranium from Leach Solutions. The uranium can be recovered from leach solutions using a variety of approaches including ion exchange (qv), solvent extraction, and chemical precipitation. The most common methods in practice are ion exchange and solvent extraction to purify and concentrate the uranium prior to final product precipitation. 

Extraction methods, amounts, and lengths of various natural fibers and their physical and chemical properties are given in Tables 2 and 3. 

Sulfur is widely distributed as sulfide ores, which include galena, PbS cinnabar, HgS iron pyrite, FeS, and sphalerite, ZnS (Fig. 15.11). Because these ores are so common, sulfur is a by-product of the extraction of a number of metals, especially copper. Sulfur is also found as deposits of the native element (called brimstone), which are formed by bacterial action on H,S. The low melting point of sulfur (115°C) is utilized in the Frasch process, in which superheated water is used to melt solid sulfur underground and compressed air pushes the resulting slurry to the surface. Sulfur is also commonly found in petroleum, and extracting it chemically has been made inexpensive and safe by the use of heterogeneous catalysts, particularly zeolites (see Section 13.14). One method used to remove sulfur in the form of H2S from petroleum and natural gas is the Claus process, in which some of the H2S is first oxidized to sulfur dioxide ... 

Depending on the extraction method and the source of Rb and Cs, the elements are obtained in industry as chlorides, nitrates and carbonates. Methods of preparing and purifying all of the alkali metals are described with examples. Methods for Rb and Cs are governed by the relative ease of reduction of their compounds, the volatility of the extracted metal and the extreme chemical reactivity of these heavier alkali metals toward air and moisture. 

In the past decade, new sample extraction techniques have been introduced to meet stricter criteria in the areas of food and agriculture, for example, enviromnentally friendly, non-toxic, fast, automated, robust, and cost-efficient techniques. Accelerated solvent extraction (ASE) and pressurized liquid extraction (PEE) are two methods developed for the extraction of chemicals of interest " and provide high yields and efficiency from a wide range of botanical, - animal, and biological samples. ASE and PLE combine solvents at elevated temperatures (40 to 200°C)... 

The same methods (chemicals, enzymes, physical treatments) can be also applied on the cell wall materials not with the aim of extracting polysaccharides but with the aim of obtaining modified fibres. New properties concerning for exemple fermentability, ratio soluble/insoluble dietary fibre, hydration., can be obtained (1). 

The other extraction method is an SEE procedure, which is a much easier procedure for extracting the nonpolar chemicals compared with polar chemicals. 

Sample preparation techniques vary depending on the analyte and the matrix. An advantage of immunoassays is that less sample preparation is often needed prior to analysis. Because the ELISA is conducted in an aqueous system, aqueous samples such as groundwater may be analyzed directly in the immunoassay or following dilution in a buffer solution. For soil, plant material or complex water samples (e.g., sewage effluent), the analyte must be extracted from the matrix. The extraction method must meet performance criteria such as recovery, reproducibility and ruggedness, and ultimately the analyte must be in a solution that is aqueous or in a water-miscible solvent. For chemical analytes such as pesticides, a simple extraction with methanol may be suitable. At the other extreme, multiple extractions, column cleanup and finally solvent exchange may be necessary to extract the analyte into a solution that is free of matrix interference. 

Extraction or rather leaching of colourants is the first and a very important step in the analytical procedure for the analysis of natural dyes. The chemical composition of extracts from historical materials depends on many factors, such as the source of natural dyes, the technological procedure of their production, storage conditions over the centuries, ageing processes and extraction conditions. The choice of the extraction method depends on the properties of the components and the matrix from which they are isolated, as well as on the mechanism of dyeing with the particular dyestuff. In this regard, they are usually divided into three groups direct, vat and mordant dyestuffs. 

Another characteristic to take into account is that ATP is an endogenous component of the cells, both somatic and bacterial. Therefore, an extraction step must to be included in the assay protocol it is very simple and quick to perform. Several extraction methods have been reported, both physical and chemical, such as heating and the use of surfactants, trichloroacetic acid, and organic solvents [89, 120, 121], The chemical methods are generally preferred the addition of a surfactant can be effective in most cases. The use of mild or strong extraction... 

Soil geochemistry is widely applied in mineral exploration, and with advancing knowledge of speciation and residence phases of trace elements in soils, a variety of partial and selective extractions for chemical analysis have been developed over the past decades. Each of these methods has been designed to target and dissolve only those elements that are adsorbed onto labile phases in soil, from carrier fluids and gases that transported them from a deposit to the surface (e.g. Hall etal. 1996). 

In terms of sample preparation, we indicated that in nearly every case, preanalysis procedures must be performed to get the sample into a form that can be utilized by the chosen analytical method. Common sample preparation schemes can involve any number of physical or chemical processes, such as drying, dissolving, extracting, or chemical alteration. 

Supercritical fluid extraction (SFE), microwave-assisted extraction (MAE) and Soxhlet extraction under various experimental conditions were applied for spiked poly(vinyl) chloride samples. Extracted dyes were separated in an ODS column (250 X 4.6 mm i.d. particle size 5 jum) using methanol as the mobile phase. Dyes are well separated by this method as demonstrated in Fig. 3.59. The optimal parameters of the extraction methods are compiled in Table 3.23. Recoveries depended on both the type of extraction method and the chemical structure of the dye. It was found that the highest recovery can be obtained by MAE and the extraction efficacy was the lowest for Solvent red 24 [129],... 

A recent and extremely important development lies in the application of the technique of liquid extraction to metallurgical processes. The successful development of methods for the purification of uranium fuel and for the recovery of spent fuel elements in the nuclear power industry by extraction methods, mainly based on packed, including pulsed, columns as discussed in Section 13.5 has led to their application to other metallurgical processes. Of these, the recovery of copper from acid leach liquors and subsequent electro-winning from these liquors is the most extensive, although further applications to nickel and other metals are being developed. In many of these processes, some form of chemical complex is formed between the solute and the solvent so that the kinetics of the process become important. The extraction operation may be either a physical operation, as discussed previously, or a chemical operation. Chemical operations have been classified by Hanson(1) as follows ... 

The greatest benefit of RACHEL S component extraction method is that a massive property index of the entire corporate database is created. Along with the atomic coordinates of each component, a wealth of chemical information characterizing each building block is stored. Data such as the size of the component, atom composition, connectivity, ring structure, and electrostatic charges are included. As such, a means of rapidly cross-referencing chemical components on demand is available. 

Potential treatment and disposal methods for drilling fluids include (1) fluid ejection, (2) pit and solids encapsulation, (3) injection into safe formations, (4) removal to disposal sites off location, (5) incineration, (6) microorganism processing, and (7) distillation, liquid extraction, and chemical fixation [13]. 

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