The Study On Stability Of Schwertmannite And Adsorption Of Chromate On Schwertmannite

This thesis is a further investigation about synthesizing method, stability of Schwertmannite and Cr(Ⅵ) absorption capability of Schwertmannite based on knowledge of mineralogy, microbiology, geochemistry and environmental science. Through improving the classical synthesizing method of Schwertmannite, the synthesizing efficiency is highly improved. The corresponding synthesizing time is shorted to 1/3. Under anaerobic condition, it is found that A. cryptum JF-5 bacteria is most active when pH value is low (pH 3-4). It can quickly reducing dissolve Schwertmannite and significantly improve the transformation rate of Schwertmannite to goethite in that condition. However, when pH value is higher, the activity of A. cryptum JF-5 bacteria is decreased obviously. It can only reducing dissolve a small quantity of Schwertmannite, but it still can promote the transformation rate of Schwertmannite to goethite. Dry and wet Schwertmannite have the same Cr(Ⅵ) absorption rate, reaching to the maximum after 3 hours. The maximum adsorption capacities of dry and wet Schwertmannite are 273mg/g and 805mg/g, respectively. Increase of temperature can accelerate the Schwertmannite's absorption capacity to Cr(Ⅵ), while it is more remarkably under relatively low Schwertmannite concentration (≤10mM). Chromate can replace the surface sulfate of Schwertmannite to form a bridged bidentate complex.