Carbon content porosity

A petroleum coke with round grains is available specifically for borehole cathodic protection applications The round grains ensure high porosity and enable gas to escape, allowing the coke to sink to the base of the borehole. This material hjis a higher bulk density than petroleum coke (1 185 kgm" ) which enables it to sink to the bottom of the borehole, yet a lower fixed carbon content (93%), with higher ash (2-06%) and sulphur (5-3%) contents. The resistivity of this material is quoted as 0-1 ohmm. 

Propylene cokage experiments followed by gravimetry have shown that higher is the 5A zeolite calcium content, higher are the cokage kinetics and carbon content inside the pores (Fig. 1). The total carbon contents retained in the porosity after desorption at 350°C of physisorbed propylene are 14.5% and 11% for 5A 86 and 5A 67 samples respectively. These carbon contents are relatively important and probably come from the formation of heavy carbonaceous molecules (coke) as it has been observed by several authors [1-2], The coke formation requires acid protonic sites which seems to be present in both samples but in more important quantity for the highly Ca-exchanged one (5A 86). 

Production. Silicon is typically produced in a three-electrode, a-c submerged electric arc furnace by the carbothermic reduction of silicon dioxide (quartz) with carbonaceous reducing agents. The reductants consist of a mixture of coal (qv), charcoal, petroleum coke, and wood chips. Petroleum coke, if used, accounts for less than 10% of the total carbon requirements. Low ash bituminous coal, having a fixed carbon content of 55—70% and ash content of <4%, provides a majority of the required carbon. Typical carbon contribution is 65%. Charcoal, as a reductant, is highly reactive and varies in fixed carbon from 70—92%. Wood chips are added to the reductant mix to increase the raw material mix porosity, which improves the SiO (g) to solid carbon reaction. Silica is added to the furnace in the form of quartz, quartzite, or gravel. The key quartz requirements are friability and thermal stability. Depending on the desired silicon quality, the total oxide impurities in quartz may vary from 0.5—1%. 

Consider the transport of phenanthrene in an aquifer exhibiting a porosity, 0, of 0.2, and an average density, ps, of the aquifer material of 2.5 kg solid L l. Furthermore, assume that the average organic carbon content of the aquifer material is 0.5% (i.e.,foc = 0.005 kg oc -kg-1 solid). Calculate the retardation factor Rn. see Section 9.2) of phenanthrene in this aquifer if the groundwater... 

Atrazine is still one of the most widely used herbicides. Estimate the fraction of total atrazine present in truly dissolved form (a) in lake water exhibiting 2 mg POC-L1, (b) in marsh water containing 100 mg solids-L-1, if the solid s organic carbon content is 20%, and (c) in an aquifer exhibiting a porosity of 0.2 by volume, a density of the minerals present of 2.5 kg-L l, and an organic carbon content of 0.5%. Assume that partitioning to POM is the major sorption mechanism. You can find Kioc values for atrazine in Fig. 9.9. Comment on which value(s) you select for your calculations. 

For this problem, assume an air-water partition constant, cH4aw = 30 and an organic carbon-water partition coefficient Kch oc = 10 L-kg-1oc. Also assume the air-plus-water-filled soil porosity is 0.4, the soil solid density is 2.5 g-mL"1, the soil water content is 12% by weight, and the organic carbon content is 5% by weight. Finally, assume the methane biodegradation obeys d[methane]totai/[Pg.774]

Estimate the dispersivity of the aquifer, aL, and the relative dissolved fraction of PCE,/. Calculate the organic carbon content, foc, of the aquifer material by using a rough estimate for the solid phase density, ps = 2.5 g cm-1, and for the effective porosity < > = 0.35. 

Early dental caries (incipient lesions) are non-cavitated and limited to the outer enamel surface. Clinically, these lesions are identified as visible white spots when the tooth is air-dried (Fig. 11.1). The incipient lesion is known as a subsurface lesion since the surface appears intact. However, histological investigations have shown that below the surface, there are zones that vary in porosity (voids from mineral loss) as well as biochemical composition (e.g. fluoride, water and carbonate content) [29]. The enamel caries can vary from a depth of 100-250 J.m (for incipient caries) to entirely through the enamel ( 1.5mm deep), at which point the cavitated lesion has extended into the underlying dentin [35]. The diagnostic challenge remains early caries detection and the focus has been on caries lesions that form on the tooth crown affecting the enamel. The remainder of the discussion will therefore concentrate on enamel caries. 

As already noted with respect to coal density (Figure 6.1), the porosity of coal decreases with carbon content (Figure 6.3) (King and Wilkins, 1944 Berkowitz, 1979) and has a minimum at approximately the 89% w/w carbon coals followed by a marked increase in porosity. The nature of the porosity also appears to vary with carbon content (rank) for example, the macropores are usually predominant in the lower carbon (rank) coals whereas higher carbon (rank) coals contain predominantly micropores. Thus, pore volume decreases with carbon content (Figure 6.4) and, in addition, the surface area of coal varies over the range 10 to 200 m2/g and also tends to decrease with the carbon content of the coal. 

FIGURE 6.3 Variation of porosity with carbon content. (Adapted from Berkowitz, 1979.)... 

Accurate determination of the coal volume fraction in the swollen coal particles can be done by calculating and excluding the pore volume, Vp, occupied by the solvent during swelling. Values of the porosity p, expressed according to equation (7) in terms of the pore volume per dry coal weight n, were determined from recent studies for similar coals (13). Where no values of this parameter were available, an interpolation of the porosity versus carbon content data (% C, dmmf basis) was used to determine p. 

So initial effective porosity, [-] Pco initial carbon content, mol/kg... 

The Deeper Unsaturated Soil The deeper unsaturated soil includes the soil layers below the root zone and above the saturated zone, where all pore spaces are filled with water. This compartment can encompass both the B and the C soil horizons. The soil in this layer typically has a lower organic carbon content and lower porosity than the root-zone soil. Contaminants in this layer move downward to the groundwater zone primarily by capillary motion of water and leaching. Chemical transformation in this layer is primarily by biodegradation. 

---