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A Cl'-intercalated hydrotalcite-like compound (HTAL) was prepared by neutralizing magnesium and aluminum chlorides with sodium hydroxide. The HTALs were characterized by chemical analyses, X-ray diffraction (XRD), differential thermal (DTA)/thermogravimetry (TG) analyses, and scanning electron microscopic (SEM) observation. The HTAL crystal with a single unit cell, aa = b0 = 0.31 and c0 = 2.33 nm as the lattice constant, was formed by aging at 353 K. The crystal growth proceeded for all three axes a, b, and c up to 5 h of aging, while the stacking along the c axis was preferentially observed by aging beyond 5 h. Phosphate ion-exchange properties of HTAL were investigated by a batch method. The HTAL obtained by longer aging time showed a slightly larger phosphate uptake, owing to better crystallization of the hydrotalcite structure. The pH dependence of the phosphate ion exchange showed that phosphate uptake has a maximum around pH 7. Chemical analyses of HTALs before and after the phosphate loading showed that phosphate ions are mostly ion-exchanged with interlayer Cl' ions, and the composition of phosphate ions in the solid phase is similar to that in the solution phase. The isotherm for phosphate uptake followed the Langmuir equation at pH 7.53 and 310 K; it gave an ion-exchange capacity of 2.37 mmol of P/g for phosphate.

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Rates of phosphate adsorption to PT-A (a new type of aluminium oxide hydroxide) and ALG (aluminum hydroxide gel) from a pH 3 phosphate solution were measured by a batch method. Phosphate uptake progressed mainly by the adsorption mechanism for PT-A, but dissolution of aluminum and precipitation of aluminum phosphate took place in addition to phosphate adsorption for ALG. The intraparticle diffusivities (Dp'S) of phosphate were evaluated from the time courses of adsorption using the model of pore diffusion with a Freundlich-type adsorption isotherm. The Dp values were approximately 7 x 10(-7) cm2 S-1 for PT-A and 1 x 10(-6) cm2 s(-1) for ALG. The tortuosity factors calculated from a model of parallel plate pore were 5.1 for PT-A and 6.7 for ALG; these values resembled those for porous inorganic ion exchangers. The adsorption rates are high enough for each of the samples to be utilized as a phosphate adsorbent to prevent hyperphosphatemia in patients on chronic dialysis. PT-A is favored as a phosphate adsorbent because of its high chemical stability against acid.

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Long silver nanowires with a high aspect ratio of up to 2000 could be obtained from Ag-containing matrix with NASICON structure by electron beam irradiation.