Adsorption from Gas Phase

3 PHYSICAL NATURE OF ADSORPTION 4.3.1 Adsorption from Gas Phase 

FIGU RE 4.16 Schematic view of the adsorption of an Ar molecule on a graphite surface. 

---

Adsorption from gas phase. The concentration (activity) a of gas molecules is proportional to the partial pressure P a = KP, where if is a constant. Inserting into Eq. (3.52) ... 

Equations for adsorption isotherms and for the heats of adsorption from gas phase... 

The phenomena presented in this book were discussed in many reviews. For example, Schwarz [13] discussed methods used to characterize the acid base properties of catalysts. The review on sorption on solid - aqueous solution interface by Parks [14] includes also principles of surface science. The book Environmental Chemistry of Aluminum edited by Sposito reviews the solution and surface chemistry of aluminum compounds. Chapter 3 [15] provides thermochemical data for aluminum compounds. Chapter 5 [16] lists the points of zero charge of aluminum oxides, oxohydroxides and hydroxides with many references on adsorption of metal cations and various anions on these materials. Unlike the present book, which is confined to sorption from solution at room temperature, publications on coprecipitation and adsorption from gas phase or at elevated temperatures are also cited there. Brown et al. [17] reviewed on dry and wet surface chemistry of metal oxides. Stumm [18] reviewed sorption of ions on iron and aluminum oxides. The review by Schindler and Stumm [19] is devoted to surface charging and specific adsorption on oxides. Schindler [19] published a review on similar topic in German. Many other reviews related to specific topics are cited in respective chapters. 

Although GAC was used almost exclusively for adsorption from gas phase, whereas PAG was used as a material for purification of liquids these distinctions have become blurred in recent years. Thereby, the use of PAG increased in a limited number of gas phase applications, while GAC is now often used in many liquid phase applications. The summary of practical applications of activated carbon is presented in Table 3. 

A gravimetric technique to study the adsorption from gas phase was described by Lobanov et al. [148]. They employed a piezoelectric crystal as measuring device. 

We now consider the process of adsorption from a microscopical point of view and, as above, start discussing adsorption from gas phase (Adamson and Cast 1997 Hiemenz and Rajagopalan 1997 Levine 2008). Figure 4.16 shows a simpMed view of the process of interaction of a gas molecule such as Ar (black sphere) with a solid surface such as graphite (gray spheres). 

Introduction to Surface Reactions Adsorption from Gas Phase... 

Most earlier theories considered adsorption from gas phase. In principle, the gaseous phase isotherms should be applicable to liquid systems when capillary condensation is neglected. Figure 8.1 show shapes of various isotherms described below. 

---