¹³C and ²⁷Al NMR study of complexation between aluminium ion and simple dicarboxylic acids under an acidic condition: new peak assignments of ²⁷Al NMR spectra of mixed solutions of Al³⁺ and simple dicarboxylic acids.

Due to a consideration of Al detoxicification by simple carboxylic acid, the interaction between aluminium ion (Al³⁺) and three dicarboxylic acids (oxalic acid (OX), malonic acid (MA) and succinic acid (SU)) under an acidic condition was investigated using ¹³C and ²⁷Al NMR techniques. Based on deconvolution of the ²⁷Al NMR spectra and quantitative ¹³C NMR spectra, the structure of each complex was elucidated. Especially, we focused on the peak assignments of ²⁷Al NMR spectra by combining of the results of quantitative ¹³C NMR spectra.

Quantification method of size distribution of polysilicic acid in supersaturated silicic acid solution.

In order to estimate the absolute size distribution of polysilicic acid particles in geothermal waters, the distribution coefficient (K(av)) of gel permeation chromatography (GPC) for polysilicic acid particles and the hydrodynamic radius for the same polysilicic acid particles from Dynamic Light Scattering (DLS) are combined to quantify the particle size. From the combination, a quantitative relationship between the K(av) from GPC and the hydrodynamic radius for polysilicic acid from DLS was built up. Using this relationship, the change in particle size of polysilicic acid formed during the polymerization of silicic acid at pH 8 and 9 (initial silicic acid concentration: 800 ppm as SiO2) was examined.

Silica deposition induced by isolated aluminum ions bound on chelate resin as a model compound of the surface of microbes.

To elucidate the mechanism of silica biodeposition in hot spring water, which is induced by Al(3+) ions bound to the surface of microbes, a chelate resin (Chelex 100) was used as a model compound of the surface of microbes. No silicic acid was adsorbed on the Na type Chelex 100, whereas silicic acids were significantly adsorbed to the Al type Chelex 100. In the Al type Chelex 100, the Al(3+) ions were present as 1:1 tridentate complex with iminodiacetate (IDA) group.

Interaction between Al3+ and acrylic acid and polyacrylic acid in acidic aqueous solution: a model experiment for the behavior of Al3+ in acidified soil solution.

From the viewpoint of the phytotoxicity and mobility of Al(3+) released from soil minerals due to soil acidification, the interaction between Al(3+) and acrylic acid (AA) and polyacrylic acid (PAA) as a model compound of fulvic acid was investigated. The interaction was examined at pH 3 so as to avoid the hydrolysis of Al(3+). The interaction between Al(3+) and AA was weak.