Alumina as adsorbent

The expected proportionality of log A versus c° plots with the solute As value has also been demonstrated in numerous LSC systems. For example, Fig. 6 shows a plot of experimental As values (slopes of log k versus e° plots) versus values calculated from the solute molecular dimensions, for various nonlocalizing solutes on an amino-bonded-phase column (aromatic hydrocarbons and ethoxylated nonylphenols). Another study (34) with alumina as adsorbent examined the ratio (kjki) [Eq. (8)) for various pairs (1 and 2) of pure solvents as mobile phase pentane/CCl, CCUAjenzene, benzene/CHzClj, and 52 different solutes (aliphatics, aromatics, polar, nonpolar). The deviation of individual experimental and calculated values of A was 1.5 units (1 standard deviation) for the range 5.1 < As s 21.2. 

Several mobile phases A/C and alumina as adsorbent showed close agreement with Eqs. (12) and (4), as summarized in Fig. 9a. 

Numerous commercial processes have been developed for dehydration of gaseous mixtures containing trace to dilute amounts of water and for removal of trace to bulk amounts of water from liquid mixtures using activated aluminas as adsorbents. The following sections outline a few of these processes. 

This chapter surveys current applications of aluminas as adsorbents. Advances in materials design and adsorption process technologies are also discussed, relating recent trends in applications of adsorbent aluminas to developing specialty process requirements. The ability of these materials to selectively remove desired compounds from the remainder of the process stream has greatly accelerated their use in recent years. 

The crystallographically stable oxides and hydroxides are not usually considered useful as adsorbents since they have little porosity and low surface area. Some of these aluminas are useful in water treatment and are reviewed in a later section. Because the primary mechanisms of separation are usually quite different, this discussion is limited to the use of aluminas as adsorbents in all applications other than water. 

---