Activated Carbon Adsorption from Solutions

Adsorption from liquid phase can take place at any of the three interfaces liquid-solid, liquid-liquid, or liquid-vapor. In practice, however, more attention has been directed and more is known about the liquid-solid interface. This is due to the fact that purification of liquids such as water, wine, and oils, and their decolorization and detoxification have been carried out for centuries using charcoals and active carbons. With the expansion of chemical, pharmaceutical and food industries the range of substances to be purified by carbons has increased enormously. 

It may be worthwhile mentioning here that the term specific surface area has a definite meaning in the case of microporous carbons, because the size of the solute molecule has a profound influence on the measured surface area. Thus, if a carbon is to be used for a particular application, its surface area should be determined with a molecular probe of the appropriate size and shape. 

The above procedures for measuring surface area and pore-size distribution appear to be very simple, but recent work has shown that the description of adsorption from solutions is over-simplified. There is need for a more critical approach if reliable conclusions are to be derived from solution adsorption experiments. 

The adsorption isotherms from the data obtained from solution adsorption on solids, in general, and on active carbons, in particular, can be obtained by plotting the amount adsorbed as a function of change in concentration of the two components in the solution. In reality, this change in concentration is caused by the removal of 

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