Smectite absorbents

Many clay minerals have aluminosilicate layer structures. For example, in kaolinite, Al2(0H)4[Si205] (Fig. 7.5), the Al3+ are all in octahedral locations. Clay minerals of the smectite or swelling type, such as montmo-rillonite, can absorb large amounts of water between the aluminosilicate... 

Bentonite and hectorite clays consist primarily of hydrated aluminum and magnesium silicates, respectively. Bentonite is recognized for its swelling capacity one gram can absorb up to 11 ml of water. A commonly used smectite clay is aluminum magnesium... 

Box 13.10 Kaolin, smectite and hormite clays from ceramics to natural absorbers... 

In the TPB-smectite system, temporal studies alleviate matrix issues because the same sample is being probed over time. Reference samples were prepared by reducing clay samples with dithionite and washing excess salts under inert atmospheric conditions (43). Wet chemical determinations of Fe(II) and total Fe were determined by digesting the reduced smectites in the presence of excess tris 1,10-phenanthroline and recording the absorbance of the Fe " -phenanthroline complex at 510 nm (44). XANES was conducted on dry powdered subsamples stored under inert conditions within days of the chemical analyses. The wet chemical results were used to standardize the edge shift of the XANES spectra for Fe(II)/Fe(III) content (45). 

Illite is the most dominant mineral present in soil samples. Apart from this mineral even smectite, kaolite, and chlorite will be present in the soil. Illite absorbs, in practice, some potassium, ammonium, cesium, and rubidium species. The solubility of clay mineral is quite high under acidic (pH <4) environmental conditions. 

PCNs, acid-activated bentonites, organophilic montmorillonites, and pillared clays with designed micro- and mesoporosity (Giiven, 2009) find specific and selective applications as catalysts and catalyst carriers in the petrochemical industry, and also in environmental applications. The capabUily of smectites to absorb not... 

Smectite clay adsorbents (bentonites) offer a broad scale of applications and bind different kinds of compounds (Table 3). Percolation experiments are now widely used to test the adsorption behavior of absorbents for practical purposes. An enormous pool of data is produced. 

Saponite, a high magnesium smectite, is similar in strueture to talc but with limited substitution of tetrahedral Sf by while heetorite has the talc structure but with limited substitution of Li for octahedral Mg and F for OH". As with montmorillonite, the resulting charge imbalanee is eompensated by Na or Ca residing with oriented water in the interlaminar spaces. Saponite and heetorite have swelling, ion exchange, and absorbent properties similar to those of montmorillonite. 

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