Expandability and layer charge characteristics of diagenetic illite (IMt-1) and hydrothermal sericite (HS) were investigated after alkylammonium ion exchange with potassium, and subsequently, Na, Ca and Mg ion exchange. After the ion exchange, both mica clay minerals clearly exhibited expandability by intercalation of alkylammonium ion, and glycerol and water saturation in their interlayer. Differences in the expandability are mainly attributed to layer charge characteristics of expandable layers, which enabled an estimation of the distribution and amount of layer charge through Xray diffraction (i.e. expansion test). X-ray diffraction patterns after the expansion tests (after alkylammonium ion exchange, after glycerol treatment for Mg-saturated samples and under various relative humidity for Na-and Ca-saturated samples) revealed the following:
1) IMt-1 and HS consist of three and two phases with different expandability, respectively;
2) IMt-1 consists of three types of domains or layers with segregation interstratified structure. The domains or layers have layer charges about 0.5, 0.7 and 1 (esu/half unit cell).
3) HS consists of two types of particles with different layer charges about 0.7 and 1 (esu/half unit cell).
From the result of the expansion tests, the existence of smectitic layers with layer charge of about 0.5 (esu/half unit cell) was confirmed. Such low layer charges have never been recognized by ordinary X-ray diffraction method and chemical analysis of bulk samples. The difference between the components in IMt-1 and HS is presumably due to different degree of alteration.
Atomic Force Microscopy observations reveal the Ca-saturated samples exfoliate thinly about 2 to 3 layers, which behave as thin particles similar to smectites in water. These observations further suggest the formation of thinly exfoliated layers even in non-expandable mica clay minerals through alkylammonium ion exchange with potassium, and subsequently Ca ion exchange.

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Wasted glassy materials such as coal fly ash, fused garbage slag or aqua-crashed furnace slag are generally classified into two groups in terms of a product of a hydrothermal treatment in NaOH solution (zeolite synthesis process). One group is materials from which zeolites will be crystallized well, and the other is those from which zeolites will be hardly crystallized. Coal fly ash belongs to the former group, and fused garbage slag and aqua-crashed furnace slag the latter. The zeolite synthesis process can be divided into two stages. In the 1st stage, Si and Al are dissolved from glass to the solution. In the 2nd stage, the dissolved Si and Al are gathered in the vicinity of glass surface and crystallized to zeolite. The second group (fused garbage slag and aqua-crashed furnace slag) is characterized by high content of CaO. It has been thought that the high content of Ca0 will prevent the dissolution of Si in the 1st stage, resulting in inhibition for subsequent crystallization of zeolites in the 2nd stage. In this study, validity of this general speculation was examined in terms of a change in amount of Al, Si and Ca in the glass and solution at the hydrothermal condition, being compared with a theoretical calculation based on the molecular orbital method.
The Na-Ca-Si-Al glasses with the composition range of Na₂O+Ca0≥40 mass% were prepared, and then they were subjected to the hydrothermal treatment in 2 M NaOH solution. The zeolite species, NaP1, was dominantly synthesized from glasses in the composition range of CaO<10 mass%. Calcium silicate hydrate or calcium aluminosilicate hydrate, CS (A) H, became dominant in the product from glasses in the range of Ca0> 10 mass%. It was found that the formation of CS (A) H, as well as NaP1 and hydroxy-sodalite, possibly affected the cation exchange capacity (CEC) value. Cross-sectional microanalysis of the glass surface and quantitative analysis of the hydrothermal media after the treatment of the glass of 30 mass% CaO revealed that the Al component was selectively dissolved into the solution and the Si component fairly remained in the glass. Also, the theoretical calculation supported the analytical results, in which Al-0 bond would be weaker than Si-O bond in Al-O-Si bonding when Al was tetrahedral and Na⁺ and CaOH⁺ coexisted. As a result, we proposed the reaction phase model on the alkali hydrothermal treatment of high Ca0-content glass, in which the reaction phase of tight calcium silicate bonding covers upon the glass surface.

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