The state of coagulation of the naturally occurring I: M interstratified clay minerals has been studied with kaolinite, acid, alkali, polar and non-polar organic solvents in their dilute H-clay form. The role of humic acids and iron compounds associated with them has also been discussed. It has been observed that the interstratified minerals did not show any coagulation due to mutual interaction with kaolinite. Further, they behaved like montmorillonite in acid and kaolinite in alkaline media. The existence of some specific exchangeable spots which undergo mutual interaction with kaolinite for coagulation is postulated.

The x-ray identification and crystal structures of clay minerals

Coagulation Behaviour of the Interstratified Clay Minerals in Dilute Suspension

Homoionised bentonites were prepared from commercial bentonites with hydrochloric acid. The Atterberg limits and the DTA curves were determined for the homoionised and commercial bentonites. This study shows that DTA can be used as a method for differentiation between clays containing mono- and divalent cations.

A differential thermal analysis study of homoionised bentonites

Adsorption properties of metahalloysite

Summary Improved predictions of sorption of hydrophobic organic compounds (HOCs) in soil require a better knowledge of the relative contribution of inorganic and organic soil constituents to the sorption process. In this paper, sorption of a three-ring polycyclic aromatic hydrocarbon (phenanthrene) and a three-ring heterocyclic–aromatic compound (dibenzofuran) by six agricultural soils, their clay-size fractions, and a series of single, binary, and ternary model sorbents was evaluated to elucidate the relative role of soil mineral and organic components in the retention of these two model HOCs. The sorption coefficients for phenanthrene and dibenzofuran on purified soil organic materials (Kd ¼ 821–9080 litre kg � 1 ) were two orders of magnitude greater than those measured on mineral model sorbents (Kd ¼ 0–114 litre kg � 1 ). This, along with the strong correlation between sorption and the organic C content of the soil clay fractions (r ¼ 0.99, P < 0.01), indicated a primary role of soil organic matter in the retention of both compounds. However, weak relationships between phenanthrene and dibenzofuran sorption coefficients and the organic C content of the bulk soils and variability of Koc values among soils, clay fractions, and model sorbents (1340–21020 litre kg � 1 C for phenanthrene and 1685–7620 litre kg � 1 C for dibenzofuran) showed that sorption was not predictable exclusively from the organic C content of the materials. Organic matter heterogeneity and domain blockage arising from organic matter–clay interactions and associated pH shifts were identified as the most likely causes of the different organic C-normalized sorption capacities of the soils. A direct contribution from minerals to the sorption of phenanthrene and dibenzofuran by the soils studied was likely to be small. Our results suggested that suitable descriptors for the extent of organic matter–mineral interactions would help to improve current Koc-based sorption predictions and subsequently the assessment of risk associated with the presence of HOCs in soil.

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The role of mineral and organic components in phenanthrene and dibenzofuran sorption by soil

Field and petrographical descriptions of some volcanic rocks occurring at two outcrops in the Lucanian Apennine (Southern Italy) are reported. The volcanic rocks, belonging to the ophiolite complex of Alpine age present in this area, are represented chiefly by pillow lavas, among which several types may be distinguished structurally, by auto-clastic lavas and volcanoclastic rocks. A Tithonian age is inferred for the pillow lavas associated with a polygenic sedimentary breccia. The mineralogy and fabric of the volcanic rocks are characteristically spilitic. Besides spilites, diabases, of probable hypabyssal occurrence, are also recorded. Some data about the spilite-forming minerals (particularly the chlorites) and four chemical analyses of spilites are reported. The variations in mineral and chemical composition exhibited by spilites are discussed and interpreted as chiefly dependent on the primary features of the extruded lavas. Furthermore, differences between spilites and some intrusive diabases and a gabbro occurring within the same area and in a similar tectonic position are pointed out. A causal relationship between spilitization and a volcanic occurrence is inferred, together with a probable primary origin of the actual essential petrographical features of the spilites. Effects of metamorphic alteration in some volcanic rocks, doubtfully referred to as medium grade burial metamorphism, and in associated sedimentary rocks are pointed out. The extent and importance of this alteration with regard to the petrogenesis of the spilites is, however, very uncertain.

The x-ray identification and crystal structures of clay minerals

Citations

Coagulation Behaviour of the Interstratified Clay Minerals in Dilute Suspension

A differential thermal analysis study of homoionised bentonites

Adsorption properties of metahalloysite

The role of mineral and organic components in phenanthrene and dibenzofuran sorption by soil

Spilites of the Lucanian Apennine (Southern Italy)

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