Oil sorption

Anticipated soil persistence mobility of parent and degfedates Water solubility oil sorption (Kp, K,... 

The same discussion on heavy oil sorption into carbonized fir fibers is reasonably assumed, which have similar pore structure, large spaces among the fibers of fir plants, small pores inside the fibers, and also rough surface of the fibers. In... 

Hydrophobic (oleophilic) nature of the surface of carbon materials seems also to be a factor governing heavy oil sorption, particularly for preferential sorption of heavy oils. 

Inagaki, M., Kawahara, A., Iwashita, N., et al. (2002). Heavy oil sorption and recovery by using carbon fiber felts. Carbon, 40, 1487—92. 

Toyoda, M. and Inagaki, M. (2000). Heavy oil sorption using exfoliated graphite. New application of exfoliated graphite to protect heavy oil pollution. Carbon, 38, 199-210. 

Zheng, Y.P., Wang, H.N., Kang, F.Y., et al. (2004). Sorption capacity of exfoliated graphite for oils - sorption in and among worm-like particles. Carbon, 42, 2603-7. 

Keywords Exfoliated graphite, heavy oil, sorption, recovery, recycling... 

FIGURE 4.7 Dependence of heavy oil sorption capacity of exfoliated graphite on its bulk density, (a) A-grade heavy oil, (b) B- and C-grade heavy oils and crude oil. 

Large void spaces among wormlike particles were quantitatively evaluated by image analysis using thin slices prepared from an exfoliated graphite after impregnation with paraffin oil. To compare the volume of these large spaces with sorptivity, they were found to be responsible for about 70% of total heavy oil sorption capacity [58]. However, crevicelike pores on the surface of particles and the ellipsoidal pores inside the particles also have important roles in heavy oil... 

This strong dependence of sorption capacity on the bulk density of carbonized fir fibers suggests that the spaces formed between entangled fibrous particles with irregular surfaces, as shown in Figure 4.3, are primarily responsible for heavy oil sorption. 

Fibrous components of several plants, such as milkweed, kenaf, cotton, and sugi (don), have been applied for recovery of spilled heavy oils [15-21,70]. In Section III.B, carbonized fir fibers were described as useful sorbents for heavy oils. The hydrophobic (oleophilic) nature of most carbon materials is expected to be advantageous for oil sorption. It seemed interesting from the viewpoint of global environment to apply as oil sorbents porous charcoals with a low bulk density prepared from quickly growing woods and plants. 

The capacity of carbon sorbents for heavy oils was found to depend mainly on their bulk density, rapidly decreasing with increasing bulk density, because the macropores in the sorbent in the range of 1 to 600 pm are primarily responsible for heavy oil sorption. As both exfoliated graphite and carbonized fir fibers can have very low bulk density, for example, 6 to 7 kg/m, they have a very high sorption capacity of about 80 kg/kg. The sorption capacity of exfoliated graphite was also found to depend on the viscosity of the oil. Carbon fiber felts, however, do not have such low bulk density, and so their sorption capacity is correspondingly low. 

FIGURE 4.13 Efficiency of utilization of pores for heavy oil sorption, i.e., ratio of volume of heavy oil sorbed to total pore volume, against average pore radius of charcoals. 

Comparison of heavy oil sorption performance among various materials... 

In Table 4.16 we summarize the heavy oil sorption performance of the three carbon sorbents used by listing their sorption capacity, sorptivity as a measure of sorption rate, and the cycling processes that can be applied. Both sorption capacity and sorptivity K, depend strongly on sorbent bulk density, as shown in Figure 4.43. 

FIGURE 4.43 Dependence of heavy oil sorption parameters on bulk density of three carbon sorbents, (a) Sorption capacity and (b) sorptivity K. ... 

The use of inorganic mineral products as oil sorbents requires in most cases their chemical or surface modification, in order to ameliorate their hydrophobic character and affinity for organic compoimds. For example, modification with CF3-(CH2)2-groups can be used, in order to limit the structure collapse of silica aerogels due to water adsorption, resulting in an excellent oil sorption capacity. Cationic surfactants, such as quaternary ammonium cations can be applied in order to ameliorate the oil sorption capacity of inorganic materials, such as zeolites, clays and fly ash [30-38],... 

A study of exfoliated graphite indicates their high heavy oil sorption capacity compared to polypropylene mats, perlite, cotton, milkweed, and kenaf Perlites have also proven to have a sorption capacity less than, but comparable to, most synthetic sorbents for oil spill cleanup. 

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