Schwertmannite formation

AMD are often very heterogeneous and reactive systems. Therefore, to describe their properties is often an issue of analytical concern as it is difficult to obtain representative samples of the affected watercourses. The instability of AMD is related to the formation and transformations of ochre-products, such as jarosite, schwertmannite and goethite (Bigham et al. 1996). Mineralogical transformations involving these ochre-precipitates have been the subject of intensive research (Kawano Tomita 2001 Kim et al. 2002 Knorr Blodau... 

After 45 days, XRD indicated the formation of schwertmannite in reactors A and C. There were no significant chemical changes in the reactor B. 

Plate VIII. Microbiological formation of schwertmannite in a bioreactor with Thiobacillus ferrooxidans (Courtesy J.M. Bigham Ohio University). 

Randall et al. (1999) studied the structure and composition of Cd-+ complexes sorbed on several iron oxyhydroxide minerals goethite, lepidocrocite, akagenite, and schwertmannite using EXAFS. In all cases, adsorbed Cd-+ formed inner-sphere complexes over a wide range of solution pH and Cd-+ concentration. However, the bonding mechanism differed between minerals and depended on the availability of different types of adsorption sites at the mineral surface. For example, sorbed to goethite by the formation of bidentate surface com-... 

The solid formed by precipitation of Fe(in) at pH 2.0-4.0 during mixing and neutralization of the AMD solutions is usually schwertmannite [6-9]. This mineral is a poorly crystallized iron oxyhydroxysulfate whose formation from acid-sulfate waters can be described as follows [8] ... 

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