Surface complexation model of Pb (II), Cu (II), Zn (II), Cd (II), As (V), Cr (VI), F (I), and B (III) ions on the surface of schwertmannite was examined with the fitting program FITEQL. Total numbers of surface sites and their protonation and deprotonation constants were initially determined by acid-base titration data with FITEQL analysis. Then, ion adsorption experiments were performed and the resulting adsorption data were used for modeling of the surface complexation. Results indicate that the cationic ions (Pb (II), Cu (II), Zn (II), Cd (II)) were strongly adsorped at pH>6-8 by complexation with the negatively charged surface sites. Whereas the anionic ions (As (V), Cr (VI), F (I)) were adsorped progressively with decreasing pH due to complexation with the positively charged sites. These adsorption properties on the schwertmannite surface were evaluated by complexation equilibrium constants of the surface species. In addition, effect of adsorped ions on the stability of schwertmannite structure was investigated by aging at 50°C. X-ray diffraction analysis indicated that adsorption of As (V) inhibited strongly phase transition to goethite.

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In view of recycling and environmental conservation, faujasite type zeolite was synthesized from paper sludge (PS) discharged from a paper-mill as an industrial waste of paper manufacturing processes. Main chemical components of the PS after burning (PS ash) were Al₂O₃ (66.1%), SiO₂ (14.4%), TiO₂ (11.5%) and MgO (7.5%), and talc, anatase, and amorphous aluminum hydroxides were identified. The PS ash (10 g) was mixed with NaOH (12 g) and water (100 g), and kept boiling for 24 h: this process was aimed to dissolve out Al from the PS ash. After cooling, water glass (SiO₂: 28.5%, Na₂O: 9.3%, H₂O: 62.2%) was added and allowed to stand for 24 h (aging process). After aging, the content was again kept boiling for 24 h to obtain faujasite type zeolite. The obtained Na-saturated faujasite (Na-F) had lattice constant of a=24.927 indicating X-type faujasite (SiO₂/Al₂O₃=2.62), and the yield was estimated as about 66%. Acetaldehyde adsorption experiment was carried out on Na-F and Ca-F (Ca saturated faujasite): 0.05 g of each faujasite sample was spread to 6.5 cm² in a 200 mL of closed vessel, and acetaldehyde was introduced to be 1000 ppm. After 80min, acetaldehyde concentration decreased to 444 ppm (Na-F) and 189 ppm (Ca-F), indicating higher adsorption ability of Ca-F than that of Na-F. This shows that calcium ion bound to faujasite has higher bonding force to acetaldehyde than sodium ion bound to faujasite. It was suggested that the zeolites synthesized using from PS ash would have enough ability for the removal of toxic gases in atmospheric environment.

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The Kobe Group distributed in the Sanda basin and eastern Kobe city, Hyogo Prefecture-southwest Japan, contains Palaeogene sedimentary rocks, such as tuff, mud and sand. Smectite and zeolite are formed characteristically in the tuff beds. Many landslides have occurred in areas where the Kobe group is widely distributed. It is generally considered that one of the mineralogical factors of landslide occurrence in these areas is the existence of smectite (Ozaki, 1986; Hirota, 1987). However, the mineralogical characteristics of smectite formed in these areas have not been discussed in detail with special reference to the landslide mechanism.
In this study, the mineralogical characteristics of smectite from the Toyooka tuff formation of the Kobe group was analyzed to discuss the mechanism of landslide occurrence.
Specimens were collected from drill cores obtained in the Kinkai, Toyooka and Toyooka-kita landslide areas. They were examined using X-ray powder diffraction (XRD), transmission electron microscope (TEM), and electron probe microanalysis (EPMA).
A large amount of smectite accompanied with small amounts of kaolinite, Mite and volcanic glass were identified within the tuff beds. Clinoptilolite in the crystallized form was also recognized in the tuff beds. All specimens from the cores were identified as a part of the montmorillonite clay mineral species. Based on the quantitative analysis of montmorillonite, it is mainly concentrated along the slip surface of these landslides, when compared with others landslides. An analysis of the montmorillonite interlayer cations revealed calcium as the main ion with a small amount of sodium. However, montmorillonite formed in the slip surface of these landslides composes of a large amount of sodium as the interlayer cation. The main interlayer cation of montmorillonite with clinoptilolite in a few formations was identified to be potassium.
The analytical results suggest that the occurrences of montmorillonite is as follows; one was formed from volcanic glass in tuff, another was formed from the fine minerals in matrix, and the third was transformed from clinoptilolite; and were considered to be formed by weathering and/or diagenesis.
The transmission electron microscope (TEM) results showed that the montmorillonite found in the slip surface was comparatively larger than the others in particle size. In a comparison of the montmorillonite formed along slip surfaces with the other areas, three characteristics were highlighted as follow, a large amount of montmorillonite was formed, montmorillonite consists mainly of sodium as the interlayer cation, montmorillonite crystals is comparatively larger than the others.

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Synthesis of schwertmannite was undertaken at 60°C and aging time for 12 mins by mixing of two equi-volume solutions of 0.02M Fe (NO₃) ₃ and 0.02M sodium salt solutions with different species of anions such as Cl, CO₃, SO4, SeO₄, CrO₄, As0₄, and PO₄ in order to elucidate the role of anions in the precipitation of ferric iron. At a given experimental condition, precipitates from S0₄, Se0₄, and Cr0₄ containing solutions were schwertmannite and that from Cl containing solution was akaganeite associated with 6L-ferrihydrite, the former two minerals whose structures are basically that of β-FeOOH. Aging of 0.01M Fe (NO₃) ₃ solution formed lepidocrocite (γ-FeOOH) via 6L-ferrihydrite. Ferrihydrite precipitated from CO₃-bearing solutions and amorphous materials from As0₄, and PO₄ solutions. The observed crystallization processes suggest that the formation of Fe polycation precursors took place early in the hydrolysis reaction, and these precursors provided nuclei to the growth and formation of different FeOOH structures by aggregation. In the course of the precursor formation, anion species such as Cl, SO₄, SeO₄, and CrO₄ that have proper values of average electronegativity could form stable complexes with Fe polycations, which resulted in the formation of β-FeOOH stmcture involving schwertmannite and akaganeite. In contrast with the seanions, NO₃ existed as a counter anion in solution because of its higher average electronegativity and consequently formed γ-FeOOH at 60°C. Since electronegativities of As0₄ and PO₄ are too small to form stable complexes with Fe polycations favorable for the formation of β-FeOOH structure, these anions led to form amorphous materials. Thus, the role of dissolved anions on the structure formation of FeOOH minerals was rationalized by taking into consideration the electron-donor characteristics of anion such as the average electronegativity and the bonding strength.

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