Macroporous carbon materials

Here, the sorption of viscous organics, heavy oils, different oils such as engine and cooking oils, and also biomedical fluids are discussed on macroporous carbon materials, mainly three kinds of materials, i.e., exfohated graphite, carbonized fir fibers, and carbon fiber felts. The recovery of sorbed heavy oils from macroporous carbon materials is also discussed. 

So far, mats of some polymers, such as poly(propylene) and poly(urethane), have been used for the sorption of spilled oil. Their maximum sorption capacity is about 10-30 g of heavy oil per 1 g of polymer [35]. However, they sorb water, as well as heavy oil, and show no special selectivity for heavy oils. Therefore, the effective sorption capacity of the polymer mats for heavy oils floating on water must be lower than the figures mentioned above. Some natural sorbents prepared from cotton fibers, milkweed flosses, and kenaf plants were reported to have rather high sorption capacity and certain potential for oil recovery and sorbent reusability [35—41]. The sorption capacity of macroporous carbon materials, exfoliated graphite, and carbonized fir fibers, is very high in comparison with these materials. Preferential sorption of oils is an advantage of carbon materials in addition to their high sorption capacity. 

Certain possibilities of these macroporous carbon materials to be used for the protection of environment from heavy oil pollutions and the reuse of spilled heavy oils were demonstrated. 

The synthesis of macroporous carbon materials was first realised by Zakhidov et al. in 1998. Macroporous carbon materials with inverse opal structures, as shown in Figure 4.14, were obtained using silica opals as hard templates and phenol resin and/or propylene gas as carbon precursor. The macroporous carbons had different structures depending... 

In principle, the morphology of macroporous carbon materials is largely dependent on the degree of void infiltration of the opal template. In order to maximise the filling of the interstitial voids of the colloid crystal with carbon precursors, liquid phase carbon precursors such as phenolic resin and sucrose solution are usually used to achieve better replication.1 2 -194] variety of carbon precursors, including propylene gas, benzene and divinylbenzene can also be successfully utilised to make three-dimensional macroporous carbon materials using colloid crystals as hard templates. The... 

Figure 4.15 SEM images of macroporous carbon materials fabricated (a) by surface templating and (b) by volume templating using 250 nm silica spheres as template. The insets show carbon-colloidal silica composites. Reprinted with permission from J.S. Yu, S. Kang, S.B. Yoon and G. Chai,/. Am. Chem. Soc., 124, 9382. Copyright (2002) American Chemical Society...

The use of dual templating strategies to synthesise three-dimensional macroporous carbon materials has been explored by the groups of Zhao and of Stein. In this case, the two templates play different roles ... 

Lee et al. studied the electrochemical properties of colloidal-crystal-tem-plated macroporous carbon materials in secondary batteries [306]. They found that the characteristics of 3-D ordered macroporous (3-DOM) carbon composed of interconnected pores with wall thickness of a few tens of nanometers enhances the kinetic performance. The authors suggested that improved performance originates from (1) a short solid-state diffusion length for lithium ions, (2) a large... 

In January 1997, the oil tanker Nakhodka spilled almost 4.5 x 10 tons of oil near the coast of Japan Sea. This accident had a strong impact because the spilled oil moved along the coastline, extending over some 250 km, and it seriously contaminated the shoreline [3]. Actually, this particular tanker accident motivated the present series of investigations, that is, sorption, recovery, and recycling of spilled heavy oils using macroporous carbon materials. 

Metallurgical coke is produced by carbonization of coals or coal blends at temperatures up to 1400K to produce a macroporous carbon material of high strength and relatively large lump size. 

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