Chapter 2.10 Micropore filling mechanism in inorganic sorbents

Abstract

The two types of pores are intraparticle and interparticle pores. The intraparticle pores are in the primary particle itself, while the interparticle pores originate from the interparticle void spaces. There are many minerals that have intrinsic intraparticle pores. Zeolites are the most representative porous solids whose pores come from the structurally intrinsic intraparticle pores. The pore geometry can be evaluated by their crystallographic data. The carbon nanotube of which pore wall is composed of graphitic sheets is also the structurally intrinsic intraparticle pore. There are other types of pores in a single solid particle. Modification of intrinsic particle structures by specific evolution, leaching, and reaction procedures can create pores in solid particles. Porous metal oxides are produced by decomposition of their hydroxides. Acid treatment of sodium silicate glass creates pores due to leaching of sodium ions. Activated carbons of the most popular adsorbent are obtained by the activation reaction of carbonous materials using H 2 O or CO 2 . Thus, the modification also provides intrinsic intraparticle pores, although particles are not necessarily crystalline. Recently, activated carbons such as activated carbon fibers (ACFs) and superhigh surface area carbons have been developed. New activated carbons have more uniform micropore size distribution and greater surface area than traditional activated carbons. The carbon membranes for gas separation have been also developed lately. Scientific studies on activated carbon have been increasing according to development of these new carbon adsorbents with a special relevance to energy and environmental demands. In particular, control of an adsorptive ability of activated carbon is requisite for new application. The chapter shows basic principles for control of the micropore filling mechanism of activated carbons.