CHAPTER 13.1 LAYERED DOUBLE HYDROXIDES

Abstract

This chapter describes layered double hydroxides. Among the group of minerals referred to as nonsilicate oxides and hydroxides, the layered double hydroxides (LDH) have many physical and chemical properties that are surprisingly similar to those of clay minerals. Their layered structure, wide chemical compositions (because of variable isomorphous substitution of metallic cations), variable layer charge density, ion-exchange properties, reactive interlayer space, swelling in water, and rheological and colloidal properties make LDH clay-like. However, because of their anion-exchange properties, LDH were referred to as “anionic clays.” Most metals in the first transition series can be incorporated into the hydroxyl sheet of the hydrotalcite-like structure. Thus, the formation of mixed metal-Al secondary precipitates may be a general reaction mechanism for transition metal adsorption to clay minerals.