Relevance of Different Intercalation Tests for Distinguishing Halloysite from Kaolinite in Soils

Abstract

--The expandabilities of kaolin-group minerals in different horizons in 10 soils from New Zealand and Fiji were measured immediately after the application offormamide and after the sequential application of hydrazine, water, and glycerol (HWG treatment). The expandabilities of these minerals in some of the soil samples with dimethylsulphoxide (DMSO) and after long-term (4-day) formamide treatments were also measured. The abundance of characteristic halloysite shapes was determined from electron micrographs of selected samples. The cxpandabilities of several non-soil kaolinite samples with the DMSO and HWG treatments were also measured.The expansion of kaolin-group minerals showed the same trends within almost all profiles, whether determined using formamide (by the immediate-formamide treatment) or glycerol (by the HWG treatment). Except where both treatments led to complete intercalation, the HWG treatment always caused more expansion of kaolin-group minerals than obtained immediately after formamide application. The HWG treatment expanded some non-soil kaolinite samples, but well-crystallized kaolinite was not affected by this treatment. The DMSO treatment expanded kaolin-group minerals in the soils to a similar extent as the HWG treatment and also expanded well-crystallized kaolinite. The degree of expansion resulting from the immediate-formamide treatment matched abundance of typical halloysite particle shapes more closely than the degree of expansion given by the other intercalation treatments. The degree of expansion immediately following formamide application could be diminished, if the samples were heated at 40 _+ 5~

The Effect of Kaolinite Intercalation on the Structural Arrangements of N-Methylformamide and 1-Methyl-2-pyrrolidone

“…Results of experimental data, however, have remained speculative as regards the precise arrangements of the guest molecules and the effect on the structures of the kaolinite host (13). It has been reported (14,15) that the expansion of kaolinite by DMSO and subsequent deintercalation results in an increase in disorder in kaolinite while elsewhere the conclusion was that intercalation resulted in a decrease in the defect structures of the clay (16). While intercalated, a three-dimensional ordering involving the DMSO and the kaolinite surfaces occurs (17)(18)(19).…”

“…• C. These can be attributed to the elimination of absorbed water and to a dehydroxylation process to metakaolinite, respectively (14). An exotherm at 995…”

Raman spectroscopy of dimethyl sulphoxide and deuterated dimethyl sulphoxide at 298 and 77 K

“…1,2 Intercalation with dimethyl sulphoxide (DMSO) is often used for kaolinites to distinguish the x-ray diffraction patterns of different types of clay minerals. 3 The reason why molecules such as DMSO, acetamide and formamide are used to expand the kaolinite layers is that these inserting molecules form stronger hydrogen bonds with the siloxane or gibbsitelike kaolinite surfaces than do the adjacent (siloxane and gibbsite-like) surfaces. Recently, DMSO has been used to intercalate highly ordered kaolinites with considerable success.…”

The effect of kauri (Agathis australis) on grain size distribution and clay mineralogy of andesitic soils in the Waitakere Ranges, New Zealand

“…Formamide treatment shifts the 0.7 nm halloysite reflection to 1.0 nm (Churman, 1990) and heating to 105 8C causes 1.0 nm halloysite to lose the interlayer water and shrink to 0.7 nm. The peak height of the 0.7 nm and 1.0 nm reflections were measured before and after formamide treatment to determine the peak height ratio (PHR) of Table 2 The most common plant species at the described sites halloysite to kaolinite as a measure for their relative abundance.…”