Adsorption - Introduction to Carbon Capture and Sequestration - page 262

Figure 6.5.2 Molecular model of a clay
Atomistic model of sodium Montmorillonite with a monolayer of adsorbed water (O: red,
H: white, Si: yellow, Na: blue, Al: purple, and Mg: green). Figure reprinted with permis-
sion from Hensen and Smit [6.16]. Copyright (2002) American Chemical Society.
compounds (HTlcs) (see Figure 6.5.2 ) or layered double hydroxides
(LDHs). These types of clays behave as chemical bases and are used as
catalysts, adsorbents, and as ion exchangers for treatment of liquid
waste. The proposed mechanism of adsorption is that CO 2 forms a com-
plex on the clay surface [6.17]. Because of this complexation chemistry,
the binding of CO 2 is stronger than in comparable zeolites. One of the
interesting aspects of these clays is that the capacity of CO 2 adsorption
actually increases when water is co-adsorbed [6.18, 6.19].