Aluminosilicate clay minerals

The retardation of subsurface transport of TNT arises from this compound s absorption into NOM and adsorption onto mineral siloxane surfaces covered with weakly hydrated cations like potassium (but not sodium and calcium). While components of feldspars exhibit some siloxane surfaces, here we anticipate that most of the silox-anes occur in the aluminosilicate clay minerals (e.g., illite) because these particles have such high specific surface areas (Table 11.3). Hence, the total for TNT may be found at this site ... 

Walker WJ, Cronan CS, Patterson HH. 1988. A kinetic-study of aluminum adsorption by aluminosilicate clay-minerals. Geochim Cosmochim Acta 52 55-62. 

May H.M., Kinniburgh D.G., Helmke P.A. and Jackson M.L. (1986) Aqueous dissolution, solubilities and thermodynamic stabilities of common aluminosilicate clay minerals Kaolinite and smectites. Geochim. Cosmochim Acta 50, 1667-1677. 

Aluminosilicate Clay Minerals (Phyllosilicates). The aluminosilicate clay minerals are sheet silicates. They are sometimes referred to as phyllosilicates, but strictly this term should also include the micas, which are primary minerals. 

Table 6 Properties of the common aluminosilicate clay minerals...

Many of the important chemical reactions controlling arsenic partitioning between solid and liquid phases in aquifers occur at particle-water interfaces. Several spectroscopic methods exist to monitor the electronic, vibrational, and other properties of atoms or molecules localized in the interfacial region. These methods provide information on valence, local coordination, protonation, and other properties that is difficult to obtain by other means. This chapter synthesizes recent infrared, x-ray photoelectron, and x-ray absorption spectroscopic studies of arsenic speciation in natural and synthetic solid phases. The local coordination of arsenic in sulfide minerals, in arsenate and arsenite precipitates, in secondary sulfates and carbonates, adsorbed on iron, manganese, and aluminium hydrous oxides, and adsorbed on aluminosilicate clay minerals is summarized. The chapter concludes with a discussion of the implications of these studies (conducted primarily in model systems) for arsenic speciation in aquifer sediments. 

Table 5. Spectroscopic Studies of Arsenic(V) Sorption on Hydrous Aluminum Oxides and Aluminosilicate Clay Minerals.

Secondary silicates form as clay minerals in soils after weathering of the primary silicates in igneous minerals. The secondary silicates include amorphous silica (opal) at high soluble silica concentrations and the very important aluminosilicate clay minerals kaolinite, smectite (montmorillonite), vermiculite, hydrous mica (il-lite), and others. Kaolinite tends to form at the low silicate concentrations of humid soils, whereas smectite forms at the higher silicate and Ca concentrations of arid and semiarid soils. The clay fraction of soils usually contains a mixture of these day minerals, plus considerable amorphous silicate material, such as allophane and imogolite, which may not be identifiable by x-ray diffraction. 

Largely due to aluminosilicate clay minerals plus soil organic matter. 

The anion forms a tetrahedron of approximately the same size as SiOj and thus, it may be attached to SiOj" along the edges of crystal lattices of stratified aluminosilicates (clay minerals). This irreversible sorption has no exchange character. 

In the preceding two decades a new class of two-dimensional molecular sieves has been synthesized from certain types of aluminosilicate clay minerals. The general procedure is to incorporate a large inorganic cation between the layers to prop them open [6]. The props,... 

---