After leaching

Moving-bed percolation systems are used for extraction from many types of ceUular particles such as seeds, beans, and peanuts (see Nuts). In most of these cases organic solvents are used to extract the oils from the particles. Pre-treatment of the seed or nut is usually necessary to increase the number of ceUs exposed to the solvent by increasing the specific surface by flaking or rolling. The oil-rich solvent (or misceUa) solution often contains a small proportion of fine particles which must be removed, as weU as the oil separated from the solvent after leaching. 

In 1997 and 1998, the authors306 307 also examined acid leached Raney copper catalysts, whereby the alloy was leached with either nitric or perchloric acid of 5, 14, or 27.5 wt% strength. The acid solution was added dropwise over 15 min to an equal volume of deionized water containing the alloy particles. After leaching at 50 °C, the particles were removed and washed to a pH of 7. Air drying at 120 °C was then carried out for one hour. The dissolution rates of catalyst components were observed to be functions of the extraction time (Table 56). 

If the desired catalyst is to consist of two or more catalytic metals after leaching or if a promoter metal is to be included, the precursor alloy becomes even more complicated with respect to phase diagrams. The approximate proportion of reactive metal (aluminum) in these ternary and higher alloys usually remains the same as for the binary metal system for the best results, although the different catalytic activities, leaching behavior and strengths of the various intermetallic phases need to be considered for each alloy system. 

Another source of chlordecone release to water may result from the application of mirex containing chlordecone as a contaminant and by the degradation of mirex which was used extensively in several southern states. Carlson et al. (1976) reported that dechlorinated products including chlordecone were formed when mirex bait, or mirex deposited on soil after leaching from the bait, was exposed to sunlight, other forms of weathering, and microbial degradation over a period of 12 years. Chlordecone residues in the soil could find their way to surface waters via runoff. 

Before considering particular applications, the potential for the recovery of values from wastes is discussed. In other chapters the various applications of solvent extraction have been presented and the technology has been shown to be highly selective, easy to operate and control, and versatile in terms of scale. Therefore, it seems to be ideal for application in the treatment of wastes, both solid (after leaching) and liquid. As noted earlier, however, there are environmental limitations mainly caused by unintentional release of the solvent into the environment. These problems can be minimized by ensuring that the treated solutions are recycled within the plant and that any solutions discharged into the environment are treated appropriately to... 

Figure 12.4 shows the spatial distribution of terbuthylazine and bromacil concentrations in a vertical cross section, after leaching by successive irrigations. Differences between the concentrations of the two herbicides may be explained in terms of the chemical properties and the soil spatial variability. The bnUc of the terbnthylazine remained close to the surface, being strongly affected by adsorption. In contrast, bromacil has a higher solubility in water and is leached downward under the inflnence of the spatial variability in hydranUc conductivity. 

Fig. 12.4 Distribution of the resident concentration of (A) terbuthylazine and (B) bromacil in a vertical cross-section after leaching with (Al, Bl) 7.3 cm and (A2, B2) 89.5cm of applied water. Contour spacing is 0.1 times the mean concentration. (Toiber-Yasur et al. 1999)...

Ni and Co are immiscible elements with Ag or Cu. Especially Ag is not miscible with Ni or Co even in liquid state. Therefore, there were no previous attempts to make Raney Ni or Co with dissolved Ag and no studies on their catalytic properties, ffere, we will show an approach to make Raney Ni or Co with Cu or Ag. In the case of Al-Co-Cu system precursor, MA was an effective process to prepare a supersaturated single solid solution as shown in Fig.9 (11). The crystallographic structure after leaching of this specimen showed a broad fee phase and no other phases were observed. To examine the as-leached state, the variation of magnetization was measured with the temperature (12). Figure 10 shows the result. The magnetization... 

Similar result was obtained for skeletal Si . The solubility of Si in the a -A1 solid solution is negligibly small so that the two phases a -A1 and relatively coarse Si existed in the conventionally prepared Al-Si alloy. By hydrochloric acid leaching, only the coarse stable Si remains after leaching, so that it is difficult to form fine Si particles by leaching. In this case, the rapid solidification increases the solubility to about 12 at%. The specific surface area of skeletal Si formed from RWA was in the range of 65-75mVg and the mean particles size was about 30-50nm by direct observation of the skeletal Si. 

Fig. 10. Change in composition of thin hollandite grains, lifted from the surface of Synroc-C, as determined by AEM after leaching in pure water at 150 °C for up to 532 days. The measured concentrations of BaO and Cs20 decrease whereas the concentrations of AI2O3 and Fe203 increase with time. There is also a slight increase in the lit), concentration out to 532 days (not shown). See text and Fig. 11 for further discussion and an illustration of hollandite alteration.

N-[2-Hydroxyethyl]ethylenediaminetriacetic acid [150-39-0] M 278.3, m 212-214 (dec). Crystd from warm H2O, after filtering, by addition of 95% EtOH and allowing to cool. The crystals, collected on a sintered-glass funnel, were washed three times with cold absolute EtOH, then again crystd from H2O. After leaching with cold H2O, the crystals were dried at 100° under vacuum. [Spedding, Powell and Wheelwright JACS 78 34 1956]. 

A survey of leach rate measurements has been made by Mendel ( 3). As examples of relatively simple procedures, three methods are described below. All such methods require either analyses of bulk liquids for ionic constituents (at low concentrations) after leaching or a drastic increase in the surface area prior to leaching to get higher concentrations that are easier to measure. 

The experimental technique devised in this work is based on a NAA method. Neutron irradiation of solid waste forms of simulated HLW (see Table II) produces activation of the elements in the sample. The activation products can be readily measured before and after leaching by radiochemical and/or instrumental techniques. In order to be useful for these purposes, the activation product must have a sufficiently energetic and abundant radiation (either 6 or y) to be easily detected, as well as a sufficiently long half-life several days or more) to be useful for relatively... 

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