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 Al3+ 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 Al3+ ions were present as 1:1 tridentate complex with iminodiacetate (IDA) group. After adsorption of silicic acid to Al type Chelex 100, a IDAAlOSi(OH)3 site formed. The site acted as a template for the successive adsorption of silicic acids to form silica sheets around Al type Chelex 100 particles. In conclusion, Al3+ ions bound to the surface of microbes play a key role as a trigger for the biodeposition of silica in hot spring water.