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The Gains-Thomas ion exchange selectivity coefficients, KGTof Fe2and Mn2on three types of Ca2-saturated clay minerals (kaolinite, montmorillonite, and illite) were determined in an oxygen-free condition in order to understand better the behaviors of these ions in anaerobic soils. The average ion exchange selectivity coefficientsKGTof Fe2to Ca-kaolinite was 1.13, with a variation of 0.72–1.46, regardless of the charge fractions of Fe2adsorbed on the surface sites (EFe), indicating that the selectivity of Fe2to the surface of kaolinite was similar to that of Ca2. The KGTvalues of Fe2to Ca-montmorillonite were high at low EFeand shifted to near 1.0 with an increase of EFe. In contrast, the KGTvalues of Fe2to Ca-illite were apparently high, near 40, at low EFeand decreased to a range of 2 to 3 with an increase of EFe, being markedly higher than those for kaolinite and montmorillonite. For both Ca-kaolinite and Ca-montmorillonite, the selectivity coefficients KGTvalues of Mn2were constant, near 1.0 with a variation of 0.66–1.51, regardless of EMn. The KGTvalues of Mn2in Ca-illite were approximated 1.4 with a range of 0.52 – 2.41. These results suggest that the solution systems composed of Mn-clay minerals and Ca-clay minerals can be regarded as thermodynamically ideal behavior. This confirms that Mn2can be adsorbed uniformly on the surface of the clay minerals with selectivity similar to that of alkaline-earth ions.

Imogolites in which a part or all of Si was substituted with Ge were synthesized from solutions containing aluminum ion and silicic and/or germanic acid. The products were similar to natural imogolite in their tubular morphology, electron diffraction patterns, and differential thermal analysis curves. However, the external diameter of the tube increased with increasing Ge substitution up to about 33 Å, and associated changes appeared in the X-ray powder diffraction patterns, suggesting that the substitution of Ge for Si caused a decrease in the curvature of the gibbsite sheet with which SiO- or GeO-tetrahedra are associated. Infrared absorption bands at 995 and 930 cm-1in imogolite disappeared and new bands appeared at 910 and 810 cm-1on substitution of Ge for Si, whereas those in the region between 700 and 300 cm-1remained unchanged or changed little. The former two bands were assigned to Si-O vibrations and the latter bands to Al-O vibrations. ?????????, ? ??????? ????? ??? ??? Si ???? ???????? Ge, ??????????????? ?? ????????, ??????????? ??? ????????, ? ????? ????????? ?/??? ??????????? ???????. ???????? ???? ??????? ???????????? ????????? ?? ????????? ??????????, ???????? ??????????? ????????? ? ?????? ????????????????? ??????????? ???????. ??????, ??????? ??????? ????? ???????????? ? ??????????? ?????? Ge ?? ????? 33 Å, ? ?????????, ????????? ? ????, ?????????? ? ???????? ?????????? ????????????? ?????????. ??? ????????? ?? ??, ??? ??????????? ?????? Ge ?????? Si ???????? ?????????? ???????? ??????????? ?????????, ? ??????? ??????? ????????? SiO ??? GeO. ?????? ???????????? ????????? ????????? ??? 995 ? 930 cm-1???????, ? ????? ?????? ????????? ??? 910 ? 810 ???1????? ?????? Ge ?????? Si, ? ?? ????? ??? ?????? ? ??????? 700–300 cm-1???????? ????????????? ??? ?????????? ????????. ??????? ??? ?????? ???????? ??????????? ????????? Si-O, ? ????????? ??????—????????? Al-?. [?.?.] Imogolite, in denen ein Teil oder das ganze Si durch Ge substituiert wurde, wurden aus Lösungen synthetisiert, die Aluminiumionen und Silizium- und/oder Germaniumsäure enthielten. Die Produkte waren im Hinblick auf die Röhren-förmige Morphologie, die Elektronendiffraktometeraufnahmen und die Differentialthermoanalyse natürlichem Imogolit ähnlich. Der äußere Röhrendurchmesser stieg jedoch mit zunehmender Ge-Substitution bis auf etwa 33 Å an, was mit Veränderungen in den Röntgenpulverdiffraktometerdiagrammen verbunden war. Dies deutet darauf hin, daß die Substitution von Ge für Si eine Abnahme der Krümmung der Gibbsitlage, mit der SiO- oder GeO-Tetraeder verbunden sind, verursachte. Die Infrarotabsorptionsbanden bei 995 und 930 cm-1des Imogolit verschwanden, und neue Banden traten bei 910 und 810 cm-1durch die Substitution von Ge für Si auf, während die Banden im Bereich zwischen 700 und 300 cm-1unverändert oder nahezu unverändert blieben. Die ersten zwei Banden werden Si-O-Schwingungen und die letzten Banden Al-O-Schwingungen zugeordnet. [U.W.] Des imogolites dans lesquelles Si était partiellement ou entièrement substitué par Ge ont été synthétisées à paritir de solutions contenant l’ion aluminium et l’acide silicique et/ou germanique. Les produits étaient semblables à l’imogolite naturelle au point de vue de leur morphologie tubulaire, des clichés de diffraction aux rayons-X, et des courbes d’analyse thermale différentielle. Le diamètre externe de tube a cependant augmenté proportionnellement à une augmentation de la substitution par Ge jusqu’à à peu près 33 Å, et les changements associés ont apparu sur les clichés de diffraction poudrée aux rayons-X, suggérant que la substitution de Si par Ge avait causé une diminution de la courbature de la feuille de gibbsite avec laquelle les tétraèdres SiO ou GeO étaient associés. Les bandes d’absorption infrarouge à 995 et 930 cm-1dans l’imogolite avaient disparu, et de nouvelles bandes avaient apparu à 910 et 810 cm-1lorsque Ge avait été substitué pour Si, tandis que celles dans la région entre 700 et 300 cm-1sont restées inchangées ou n’ont changé que très peu. Les deux premières bandes ont été assignées à des vibrations Si-O, et les deux dernières bandes ont été assignées à des vibrations Al-O. [D.J.]

We studied the formation and polymerization of silicatoaluminate (SA) monomer ions in dilute, aqueous solutions of aluminate ions, orthosilicic acid, and sodium hydroxide by stepwise neutralization with hydrochloric acid. We inferred SA formation from the increase in the proportion of “monomer aluminum” and the decrease in removal of silicon and aluminum from the solution by polymerization, with increasing silicon-to-aluminum ratio. The products that were formed at 100 percent neutralization and retained on the Millipore filter were similar to allophane; they had silicon-to-aluminum ratios of 0.4 to 1.2 and appeared as hollow spheres with diameters of 30 to 50 angstroms, though there were some differences between them and allophane on the infrared spectra. The strong surface acidity of some products suggested that they contained four-fold coordinated aluminum.

Hollow spherical particles of aluminosilicate having diameters of 80 to 100 Å and high electric charge were synthesized by heating solutions containing Si and Al concentrations of about 2 mM (Si/Al molar ratio = 1.0–1.2; pH = 9.0) at 95°–100°C for 7 days. Electron microscopy, X-ray powder diffraction, and infrared spectroscopy suggested that the walls of the spherical particles consisted of monolayer aluminosilicate, most probably having a 1:1 layer structure. Chemical analysis supported this supposition but indicated modifications as shown in the formula (Si1.85Alo0.62)IV(Al1.38)VI(OH)4.10O4.96Na0.62, compared with (Si2)lv(Al2)VI(OH)4O5for an ideal 1:1 layer silicate. High-resolution 29Si and 27A1 nuclear magnetic resonance spectroscopy indicated the substitution of Al for Si in the tetrahedral sheet, the presence of A1IVand A1VI, and the presence of Si bonded through oxygen to three Al atoms and one H. A natural counterpart of the synthesized aluminosilicate may be a precursor of halloysites formed by weathering of volcanic ash and pumice and have a close structural relation with allophane and imogolite

The Bingham yield stress for suspensions of illite-iron oxide complexes is examined as a function of pH and iron oxide content. Addition of iron oxides to illite increased the yield stress over a pH range of 3 to 10. With increasing pH the yield stress decreased for the complexes with iron oxides of 2 and 5% while the complexes with iron oxides of 7, 10, and 20% exhibited the maximum yield stresses at pH values from 6 to 8. The iron oxides which are not associated with the illite enhanced the yield stress more than the iron oxides precipitated on the illite surfaces. The yield stress for the complexes was correlated with their zeta potential, and the higher yield stress is considered due to smaller interparticle repulsion.

Imogolite was synthesized at 25°C by aging partially neutralized solutions containing monomeric silicic acid and polymeric hydroxy-aluminum ions for 7 years. Solutions having an initial Si/Al molar ratio of about 0.5 and pHs of 4.0–4.5 produced the largest yields of imogolite, followed by those having an initial Si/Al ratio of about 1, although imogolite was not the principal product. Electron microscopic examination showed a small amount of imogolite fibers embedded in a noncrystalline gel-like substance. Traces of imogolite were detected in solutions having an initial Si/Al ratio of about 2, but no imogolite was found by electron microscopy in products from solutions having an initial Si/Al ratio of about 4. Only gibbsite formed from solutions having initial Si/Al ratios of <0.27. The diameter of the tubular structural unit of the imogolite produced in these experiments was 23 ± 2Å, close to that of natural imogolite.