A capable adsorption of benzene, toluene, aniline, benzoic acid and phenol in water by pyrophyllite was investigated. Pyrophyllite could adsorb benzene and toluene well, as compared with aniline, benzoic acid and phenol. Benzene and toluene are highly insoluble, while aniline, benzoic acid and phenol are soluble in water. Since the (001) plane of pyrophyllite is almost 0 charges, benzene and toluene would be easily adsorbed on the plane. On the other hand, aniline and benzoic acid would be adsorbed on the edge of pyrophyllite, because hydroxyl groups are exposed on the edge. In the same pH condition, hydroxyl groups of phenol and pyrophyllite would almost change to the same charge. Therefore, phenol would be hardly adsorbed by pyrophyllite. Adsorption of benzene and toluene by phyrophyllite was almost the same ability as that by talc and the complex of montmorillonite with surfactant to be made to remove such aromatic hydrocarbons. Pyrophyllite would be a good adsorbent to remove a highly hydrophobic aromatic hydrocarbon.

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Adsorbents that capture both cations and anions were prepared by addition of zeolite powders to aqueous dispersions of colloidal layered double hydroxide (LDH). Hybrid adsorbents were obtained from the mixtures by removal of water via mild heating. Scanning electron microscope observations revealed that zeolite particles were uniformly coated with LDHs. Targeted ions (IO_3^-, I^-, and Cs^+) were selected from among the probable radioactive substances released in nuclear power plant accidents; non-radioactive counterparts were used in the experiments. The zeolites used in the hybrid adsorbents were Na-type zeolites that produced a high pH environment in aqueous solutions. The hybrid adsorbents were conditioned before adsorption experiments by anion exchange for Cl^- with a NaCl solution. Arising of OH^- anions from zeolites, onto which LDHs closely attached, affected both conditioning and subsequent tests and resulted in poor uptake of IO_3^- and I^-. However, after treatment with a MgCl_2 solution, Na^+ ions in the zeolite moieties in the hybrid adsorbents were partially exchanged for Mg^<2+>, and generation of OH^- anions in aqueous solutions was suppressed. Additionally, Cl contents in the hybrid adsorbents increased probably because of suppression of OH^- anion generation during the treatment. As a result, uptake of IO_3^- and I^- by the hybrid adsorbents was improved. Sufficient adsorptive removal of Cs^+ was also attained, despite the fact that the surfaces of the hybrid adsorbents were covered with a crust of LDH.

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Allophane is a hollow spherical aluminium silicate with some holes, and inner and outer surfaces of the hollow sphere can adsorb cations, anions and molecules. In this study, two natural allophane samples with different Si/Al atomic ratio (KyP: 0.67, KnP: 0.99) and a montmorillonite sample were used to adsorb ammonia and pyridine gases. The amount of adsorption of ammonia and pyridine at lower equilibrium concentrations increased in the order, montmorillonite < KnP < KyP, and the strength of adsorption of the two adsorbates estimated by Langmuir K and Freundlich n values increased in the same order. For all the samples, the amount and strength of adsorption of ammonia were greater than those of pyridine. Ab initio/hybrid (ONIOM) method was used to simulate the formation of five-coordinated Al in the pore region of allophane, and the adsorption of ammonia and pyridine on the Al was also simulated. The five-coordinated Al was speculated to form easily with heating. Binding energy of ammonia to the five-coordinated Al was calculated to be stronger than that of pyridine, and this was in good agreement with the experimental results.

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The cation exchange capacity (CEC) derived from octahedral layer charges (OLC) (CEC_<OLC>), the CEC derived from tetrahedral layer charges (TLC) (CEC_<TLC>), and the amount of Al as a hydroxy-Al polymer in interlayer sites (Al_<HIM>) were determined for natural soil clays fractionated from acidic forest soils (Dystrudepts) developed from sandstone and shale in Kinki-district of Japan. The CEC_<OLC>, determined by the reduced amount of CEC after Li-saturation and heating to 250℃ (Greene-Kelly test), was not correlated with Al_<HIM>, estimated from the amount of Al extracted with hot sodium citrate. In contrast, an approximate index value of CEC_<TLC>, represented by the residual CEC at pH 5.0 after subtracting the CEC_<OLC> was correlated negatively with Al_<HIM>, suggesting that CEC_<TLC> is largely responsible for the stabilization of hydroxy-Al polymers in 2:1 phyllosilicates.

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