Effect of bacterial siderophore on cesium dissolution from biotite.

In this study, the adsorption of cesium (Cs) on biotite and dissolution of Cs from Cs-bearing biotite using a siderophore were investigated aiming to contribute to the elucidation of radiocesium migration mechanisms in the soil environment. Thus, a siderophore was extracted and purified from the culture medium of Pseudomonas sp., and the purified siderophore was used in five consecutive dissolution experiments of biotite samples. Prior to the dissolution experiments, Cs was adsorbed on a hardly weathered biotite powder sample. The major components of the biotite (Al, Fe, and Mg) were dissolved almost stoichiometrically, strongly suggesting that the siderophore selectively dissolves the broken edges of the biotite. The amount of the dissolved Cs decreased by increasing the repetition times of the dissolution experiment. Therefore, the Cs adsorbed on the broken edges was dissolved rapidly as the siderophore dissolved the broken edges, and then, the Cs adsorbed on the outer planar surface of the biotite particles was slowly dissolved because the siderophore did not directly dissolve the outer planar surface of the biotite but dissolved the surface edge.