The Na-Cs and Na-Sr exchange properties of Na-montmorillonite heated at various temperatures under dry conditions have been studied at 25°C and a constant normality of solution. The standard free energy changes were-2.6 kcal/eq for Na-Cs and-0.99 kcal/eq for Na-Sr in the air-dried montmorillonite. In the montmorillonite pre-heated at 100°C-600°C, the Cs-selectivity increased in the smaller Cs-equivalent fraction in clay but such an increase did not appear in the Na-Sr exchange. In addition, complete exchange from Na-form to Cs-and Sr-forms was not achieved in the pre-heated materials because of fixation of interlayer Na. The proportions of fixed Na were less than 10% upon heating at <300°C but increased to 25-30% for Na-Cs and 15-20% for Na-Sr by heating at 600°C. These values were nearly constant indifferent to normality of solution and exchange temperature.

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Electron spin resonance spectra were recorded for 13 halloysite samples of various geneses and morphologies. The spectra are similar to those of kaolinite. Signals near g=4 are due to Fe³⁺ at the octahedral sites of halloysite as confirmed by Fe determination after dithionite treatment. A very broad signal around g=2 is attributed to Fe minerals coexisting as impurities, and therefore ESR is useful in distinguishing between these two kinds of Fe.

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Since the texture of the clay-aerogel is the replica of ice crystals appeared inthe process of freezing, an attempt has been made to control the aerogel texture by varying some factors related to the ice crystallization. As was expected, OM and SEM observations of the aerogels indicated that the size and the shape of a pore in the aerogel was strongly dependent on both the concentration of clay suspension and its freezing rate in the ranges from 5 to 20 wt% and from 1×10^-1 to 1×10^-3 ml/sec, respectively. For decreasing the concentration and the freezing rate of the clay suspensions, the shapes of pores changed from a polygonal cell to a thin lens. The pores tended to be arranged almost parallel to the heat-flow direction. By the heat-treatment at high-temperatures up to at least 800°C, the aerogel still retained its texture and strength, although the shrinkage was not avoidable.

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Coal fly ash was treated with 3.5 M NaOH water solution by heating to 80-90°C for 24 h. The alkali treatment caused an increase in cation exchange capacity (CEC) from 12-20 me/100 g to 158-360 me/100 g for the fly ash. X-ray powder diffraction analysis showed that hydroxy-sodalite, faujasite and phillipsite formed in the ash after the treatment. The formation of such zeolite was most likely responsible for the increase of CEC. It is possible to apply the zeolitized fly ash tomaterial for soil amendment, removal of NH₄⁺ and heavy metals from waste water, deodorization and moisture desorption. The present results may lead a technologyfor utilization or recycling of the waste coal ash.

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Mechanochemical structure change of allophane by dry grinding and their effects on the allophane-mullite thermal reaction have been examined by powder Xray diffraction (XRD), differential thermal analysis (DTA), infrared absorption (IR) spectra, transmission electron microscopy (TEM) and X-ray radial distribution function analysis (RDF). RDF analysis revealed that dry grinding caused change of a part of Al coordination number from six to four and also caused the configurationof polyhedra more random state. Breakdown of the Si-O-Al linkage was deduced from the shift of the IR absorption band around 900-1100cm^-1. Almost simultaneous formations of spinel phase and mullite were obserted when untreated allophane was fired at around 1000°C, whereas formation temperature of spinel phase was lowered by about 30°C and that of mullite was raised by about 100°C by dry grinding. These changes may be due to the breakdown of the Si-O-Al linkage and segregation into condensed Al₂O₃ and SiO₂ configurations.

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