Liquid-phase adsorptions factors, controlling

Applications of activated carbons (AC) in liquid-phase adsorptions are extensive, the number running into thousands. This Chapter makes no attempt to summarize such involvements, but concerns itself with explanations of mechanisms of adsorption of inorganic and organic species from the aqueous phase. In this way, an understanding of the factors which control extents of adsorption is made available and can be extended to other systems. This Chapter also highlights applications of major industrial importance. 

To conclude, it appears that the aforementioned properties and the possibility of macroscopic shaping make CNTs and CNFs attractive competitive catalyst supports when compared with activated carbons. Indeed, resistance to abrasion, thermal and dimensional stabilities, and specific adsorption properties are important factors controlling the final activity and reproducibility of the catalytic system. In particular, CNTs and CNFs could replace activated carbons in liquid-phase reactions since the properties of the latter cannot be easily controlled, and since their microporosity has often slowed down catalyst development. 

Gas-liquid relationships, in the geochemical sense, should be considered liquid-solid-gas interactions in the subsurface. The subsurface gas phase is composed of a mixture of gases with various properties, usually found in the free pore spaces of the solid phase. Processes involved in the gas-liquid and gas-solid interface interactions are controlled by factors such as vapor pressure-volatilization, adsorption, solubility, pressure, and temperature. The solubility of a pure gas in a closed system containing water reaches an equilibrium concentration at a constant pressure and temperature. A gas-liquid equilibrium may be described by a partition coefficient, relative volatilization and Henry s law. 

Mass transfer in a bulk stationary phase as in partition systems, is analogous to retention on an adsorptive surface in that a certain average time is required to absorb and desorb the molecule. However, whereas the mean desorption time is determined by the rate constant (kd) for the desorption process, in a partition system the controlling factor is the solute diffusion coefficient in the stationary phase, Ds. The mean desorption time is replaced by the average diffusion time, tD, the time taken for a molecule to diffuse a distance d in the liquid. Then ... 

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