Abstract: The adsorption and polymerization of dissolved silicates on iron oxides affect the distribution of trace elements in the aquatic environment. The study of silicate chemistry on iron oxide surfaces is theoretically and practically important to understand the migration and distribution of other solution anions or trace contaminants. In this work, the adsorption kinetics of dissolved silicates on goethite was investigated, and their polymerization behavior was characterized by attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR). The results showed that the adsorption of silicates by goethite could be attributed to chemical adsorption and well fitted by pseudosecond order kinetic equation with R²>0.996. The polymerization of silicates occurred when monomeric silicates were adsorbed to goethite surface. Polymerization gradually increased over the reaction time, and the changes in the direction of polymerization might be accompanied. In addition, there was a gradual increase of IR absorption peak in the region of polymerization as the Fe/Si molar ratio decreased. Mineral morphology and surface structure may have effects on silicate polymerization. The infrared results also indicated that the adsorbed polymeric silicates on goethite surface probably showed similar structure to silicic acid (SiO₂xH₂O), which was significantly different from the previous reports on adsorption and polymerization of silicates on ferrihydrite. This indicated that surface structure of goethite could promote the polymerization of silicate on its surface.

Key words: natural evergreen broad-leaved forest., litter decomposition, cellulose, lignin