Activated carbon molasses number

Six common isotherm shapes are shown in Figure 14.4. In fact, those are the classic isotherm types suggested by Brunauer et al. (1940). Each can be represented by numerous empirical equations, some of which are discussed later. The inherent shapes or types arise from the pore structure of the adsorbent, the nature of the forces between the adsorbent surface and adsorbate, and the dependence on concentration. Besides isotherms, other properties are related to adsorption capacity, especially surface area and pore size distribution. Some other properties are application oriented, such as CTC (carbon tetrachloride) index, iodine number, methylene blue factor, and molasses number, all defined in Table 14.1. They are frequently employed to describe activated carbons. 

The liquid-phase materials are usually characterized by sorption tests using phenol, iodine, or "molasses number." The vapor-phase activated carbons are usually characKiized by carbon tetrachloride or benzene adsorption tests. The adsorption capacity and the bulk density define the volumetric treatii capability of the material. 

J. There are separate tests for the capacity of activated carbon used in water service to hold impurities. They are known as the Iodine Number test (ASTM D4607-94) and the Molasses Number test (no ASTM test). 

Pore volumes of carbons are typically of the order of 0.3 cm /g. Porosities are commonly quoted on the basis of adsorption with species such as iodine, methylene blue, benzene, carbon tetrachloride, phenol or molasses. The quantities of these substances adsorbed under different conditions give rise to parameters such as the Iodine Number, etc. Iodine, methylene blue and molasses numbers are correlated with pores in excess of 1.0,1.S and 2.8 nm, respectively. Other relevant properties of activated carbons include the kindling point (which should be over STO C to prevent excessive oxidation in the gas phase during regeneration), the ash content, the ash composition, and the pH when the carbon is in contact with water. Some typical properties of activated carbons are shown in Table 2.2. 

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