Pretreatment Method

Raw biomass is extremely persistent to enzymatic degradation. Therefore, methods of thermochemical pretreatment have been developed to improve the digestibility of biomass (18). For example, ammonia explosion, aqueous ammonia recycle, controlled pH, dilute acid, flow through, and hme treatment were applied to prepare com stover, i.e., the leaves and stalks of maize, for a subsequent conversion to sugars. 

In general, the digestibility of cellulose is improved by the removal of lignin and hemicellulose (19). This can be achieved by a 

On the other hand, an acidic pretreatment will hydrolyze the hemiceUulose but the cellulose and lignin remains intact (21). An acidic pretreatment may also result in high concentrations of furfural compounds in the liquid phase (13). Such compmmds may act as fermentation inhibitors. 

Another problem is the bacterial contamination of fermentation mixtures. Bacterial contamination can be hardly avoided xmder 

It was established that a range of concentrations exists in which fermentation inhibitors derived from pretreatments of lignocellu-losic feedstocks are not affecting the yeast, but will inhibit further growth of lactic acid bacteria. By an optimization of the levels of fermentation inhibitors the fermentation of biomass can be conducted under non-sterile conditions. Here, the yield of ethanol is comparable to those achieved under sterile conditions (22). Optimized inhibitor levels can be achieved by controlling the ratio of water to biomass of a lignocellulosic biomass during and after the pretreatment. 

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Primary or pretreatment methods. Primary or pretreatment processes serve two purposes ... 

Ultrafiltration. Ultrafiltration was described under pretreatment methods. It is used to remove finely divided suspended solids, and when used as a tertiary treatment, it can remove virtually all the BOD remaining after secondary treatment. 

Adsorption. Some organics are not removed in biological systems operating under normal conditions. Removal of residual organics can be achieved by adsorption. Both activated carbon and synthetic resins are used. As described earlier under pretreatment methods, regeneration of the activated carbon in a furnace can cause carbon losses of perhaps 5 to 10 percent. 

The success of a reverse osmosis process hinges direcdy on the pretreatment of the feed stream. If typical process streams, without pretreatment to remove partially some of the constituents Hsted, were contacted with membranes, membrane life and performance would be unacceptable. There is no single pretreatment for all types of foulants. Pretreatment methods range from pH control, adsorption (qv), to filtration (qv), depending on the chemistry of the particular foulant. Some of the pretreatment methods for each type of foulant are as foUow (43—45) ... 

Phosphorus and Silicon in Waters, Effluents and Sludges [e.g. Phosphorus in Waters, Effluents and Sludges by Spectrophotometry-phosphomolybdenum blue method. Phosphorus in Waters and Acidic Digests by Spectrophotometry-phosphovanadomolybdate method. Ion Chromatographic Methods for the Determination of Phosphorus Compound, Pretreatment Methods for Phosphorus Determinations, Determination of silicon by Spectrophotometric Determination of Molybdate Reactive Silicon-1 -amino-2-naphthol-4, sulphonic acid (ANSA) or Metol reduction methods or ascorbic acid reduction method. Pretreatment Methods to Convert Other Eorms of Silicon to Soluble Molybdate Reactive Silicon, Determination of Phosphorus and Silicon Emission Spectrophotometry], 1992... 

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 usual means of identifying and quantifying the level of these additives in polymer samples is performed by dissolution of the polymer in a solvent, followed by precipitation of the material. The additives in turn remain in the Supernatant liquid. The different solubilites of the additives, high reactivity, low stability, low concentrations and possible co-precipitation with the polymer may pose problems and lead to inconclusive results. Another sample pretreatment method is the use of Soxhlet extraction and reconcentration before analysis, although this method is very time consuming, and is still limited by solubility dependence. Other approaches include the use of supercritical fluids to extract the additives from the polymer and Subsequent analysis of the extracts by microcolumn LC (2). 

Where hardness removal is required, the simplest pretreatment method for smaller, lower pressure boiler plants (below 200-300 psig) is to use a cation-exchange softener. This removes the calcium and magnesium at source and converts the bulk of temporary hardness salts into sodium bicarbonate (NaHC03), which decomposes to form sodium carbonate (soda ash) but does not scale under normal boiler operating conditions. 

The most common method to extract xylan is the alkaline extraction. Several pretreatment methods can be used in association in order to break the covalent bonds that exist between xylan and other carbohydrates during the extraction (Wang Zhang, 2006). A number of articles studied the use of ultrasound on the xylan extraction. Hromadkova and coworkers reported that 36.1% of xylan was extracted from corn cobs with 5% NaOH solution at 60°C for 10 min of ultrasonication in comparison with 31.5% of xylan in the classical extraction. Both extractive methods yielded xylan with immunogenic properties (Hromadkova et al., 1999). 

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. 

Cellulase enzyme complexes consist of three major types of proteins that synergistically catalyze the breakdown of a cellulosic substrate. Because the enzymes are strictly substrate-specific in their action, any change in the structure or accessibility of the substrate can have a considerable influence on the course of the hydrolysis reaction. A pretreatment method based on exposing cellulosic substrate to phosphoric acid solution [9] and addition of the nonionic... 

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 ... 

Oil skimming as a pretreatment method is effective in removing naturally floating waste material. It can also improve the performance of subsequent downstream treatments. Many coil coating plants employ this treatment process. 

Fetsch PA, Abati A. The effects of antibody clone and pretreatment method on the results of HER2 immunostaining in cytologic samples of metastatic breast cancer a query and a review of the literature. Diagn. Cytopathol. 2007 35 319-328. 

Other methods reported for the determination of beryllium include UV-visible spectrophotometry [80,81,83], gas chromatography (GC) [82], flame atomic absorption spectrometry (AAS) [84-88] and graphite furnace (GF) AAS [89-96]. The ligand acetylacetone (acac) reacts with beryllium to form a beryllium-acac complex, and has been extensively used as an extracting reagent of beryllium. Indeed, the solvent extraction of beryllium as the acety-lacetonate complex in the presence of EDTA has been used as a pretreatment method prior to atomic absorption spectrometry [85-87]. Less than 1 p,g of beryllium can be separated from milligram levels of iron, aluminium, chromium, zinc, copper, manganese, silver, selenium, and uranium by this method. See also Sect. 5.74.9. 

Table 5. Effect of Variation in Pretreatment Methods on 15N Values of Contemporary and Late Pleistocene Bone Samples9.

Volatile samples are usually analyzed by gas chromatography. There are many different sample pretreatment methods for gases. Let us review these techniques ... 

Regardless of the pretreatment method, simple manipulations in sample preparation remain one of the most labor-intensive areas of analytical work [491]. 

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). 

NF has been also been studied as a potential form of pretreatment for reverse osmosis desalination processes (Hassan et al. 1998, 2000). Based on the feed water, it may be a suitable pretreatment method that allows for operation with little or even no use of antisealants. 

This actually refers to a family of similar spectral pretreatment methods that involve the snbtraction of a... 

Like SNV, this pretreatment method [1,21] is a sample-wise scaling method, which has been effectively used in many spectroscopic applications where multiplicative variations are present. However, unlike SNV, the MSC correction parameters are not the mean and standard deviation of the variables in the spectrum x, but rather the result of a linear lit of a reference spectrum x f to the spectrum. The MSC model is given by the following equation ... 

Improved x-data pretreatment Newly discovered effects in the on-line analyzer data could be more effectively filtered out using a different pretreatment method. More effective pretreatment would then reduce the burden on the modeling method to generate an effective model. 

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