Textures surface content

Among the characteristics of the adsorbent are its pore texture, surface chemistry, and mineral matter content. The characteristics of the adsorptive are its molecular size, solubility, polarity, pIC, (for electrolytes), and nature of the substituents if it is aromatic. Finally, the solution chemistry factors are the pH and the ionic strength [5]. I shall focus in this section only on the role of the characteristics of the adsorbent, especially its carbon surface chemistry, on the adsorption processes, because although its importance has long been recognized [6, 7], the exact nature of this importance has often been controversial and misunderstood [1]. 

Fig. 11.15 Vertical section of a Co-rich Mn crust from the flanks of a guyot on the Ogasawara Plateau N.W. Pacific (25°18.9 N, 143°54.8 E 1515 m) collected by dredge during a cruise of the GSJ with R.V. Hakurei-maru in 1986. The substrate (not clearly seen) is phosphatized limestone. The crust is more than 20 cm across, about 10 cm thick and has a knobby surface texture. Element contents are Mn 21.7%, Fe 18.9%, Co 0.81%, Ni 0.31%, Cu 0.04%, Pb 0.26% and Pt 0.29 ppm. The upper layer of the crust displays the highest Co content and the bottom layer the highest Pt (0.78 ppm). 6Mn02 is the principal mineral present with minor quartz and plagioclase. Photograph courtesy of A. Usui, GSJ.

The dielectric breakdown strength in vitreous siUca depends on its impurity content, its surface texture, and the concentration of stmctural defects, such as cord and bubbles. Good quaUty glasses have room temperature breakdown strength in the range of 200—400 kV/cm. 

Transmission electron micrographs show hectorite and nontronite as elongated, lath-shaped units, whereas the other smectite clays appear more nearly equidimensional. A broken surface of smectite clays typically shows a "com flakes" or "oak leaf surface texture (54). High temperature minerals formed upon heating smectites vary considerably with the compositions of the clays. Spinels commonly appear at 800—1000°C, and dissolve at higher temperatures. Quartz, especially cristobalite, appears and mullite forms if the content of aluminum is adequate (38). 

Modification techniques for activated carhon were used to increase the removal capacity by surface adsorption and to improve the selectivity to volatile organic compounds (VOCs). Modified activated carbons (MACs) were prepared by modifying the purified activated carbon with various acids or bases. The effects of adsorption capacity and modified contents on the textural properties of the MACs were investigated. Furthermore, VOC adsorption and desorption experiments were carried out to determine the relationship between the adsorption capacity and the chemical properties of the adsorbents. High adsorption capacity for the selected VOCs was obtained over lwt%-H3P04/AC (lwt%-PA/AC). As a result, MAC was found to be very effective for VOC removal by adsorption with the potential for repeated use through desorption by simple heat treatment. 

French fries are made from potatoes that have been cut into thin strips (around 1 cm square in cross-section), washed briefly in cold water, partly dried to remove surface moisture and deep fired in vegetable oil at around 180°C to a light golden color. The final product comprises around 10% fat, most of which is retained on the surface. Frozen fry manufacturers ship their products raw, par-fried, or partially cooked and drizzled with oil for baking, to suit the end user. The product is frozen at —40°C and stored at —20°C. Moisture content needs to be less than 70% in par-fried fries to prevent limpness and separation of the interior and the cmst. Heterogeneity in moisture content between strips can result in variability in texture. Fr5dng is finished by immersing the frozen product in deep fat at about 200°C until the desired color and texture are achieved. 

Few comprehensive classification schemes for CCP exist. The American Society for Testing and Materials (ASTM 1994) classifies two catgories of fly ash (Class F and Class C) based upon chemical and physical properties of the fly ash (the total amount of Si + A1 + Fe, sulphate, loss on ignition). This classification system was developed for the use of fly ash as an admixture in concrete. More recently, new classification schemes have been developed that place emphasis on textural descriptions, the form of carbon (or char ), and the surface properties of fly ash (Hower Mastalerz 2001). These new classification schemes for fly ash may be the result of growing concern over mercury emissions from coal-fired boilers. Studies have shown that mercury adsorption onto the surface of fly ash particles is a function of both the total carbon content and the gas temperature at the point of fly ash collection (Hower et al. 2000). 

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