This chapter focuses on the structure and porosity of activated carbons because the origins, extents, and characteristics of porosity are intimate functions of structure. Activated carbon is a powerful adsorbent and exhibit extreme specificity of application via variations in structure. An activated carbon can be considered as molecular space, this space being contained within a three-dimensional network of carbon atoms arranged in layers composed of ring structures joined together somewhat imperfectly. Quite diverse source (parent) materials are currently used in active carbon production. Structures produced by their carbonization may be considered as segments of graphene sheets of different sizes reaching nanometer dimensions and degree of perfection bonded together in an infinite number of ways. The success and continuing use of activated carbons are a direct consequence of the uniqueness and versatility of activated carbons. Such a unique and versatile material, naturally, has attracted the attention of a wide range of investigators, from water engineers, environmental groups, design engineers, to chemists, physicists, mathematicians, and computer modelers.
