Chemical adsorption of silicic acid to aluminum combined with cation exchange and chelate resins as model compounds of the surface of microbes

To elucidate the biodeposition mechanism of silicic acid from hot spring water that metal ions participate, the coordination structure of aluminum ions combined with functional groups on Bio-Rex 70 (cation exchange resin with carboxyl groups) and Chelex 100 (chelate resin with iminodiacetate groups) as model compounds of the surface of microbes and the adsorption of silicic acid to the aluminum ions were investigated. Aluminum ions combined on the Bio-Rex 70 were present as monodentate complex with carboxyl groups. Most of aluminum ions combined on the Chelex 100 were present as monodentate complex, however, 1:1 and 1:2 tridentate complexes were formed under low concentration of aluminum. Aluminum ions of the monodentate complexes on Bio-Rex 70 and Chelex 100 eliminated into silicic acid solution, and could not take up silicic acid from solution. However, aluminum ions of the tridentate 1:1 complexes on Chelex 100 took up effectively silicic acid from solution. It was suggested that the 1:1 chelate complexes on the surface of resin (microbes) play an important role for biodeposition of silicic acid from hot spring water: the aluminum ions of the complexes act as adsorption sites of silicic acid.