U-phosphate biomineralization induced by Bacillus sp. dw-2 in the presence of organic acids

Abstract

In this paper, we systematically investigated the influence of some selected ligands on the U-phosphate precipitation induced by soil bacteria. These organics are widely ranging from acetate, lactate, salicylate and citrate to oxalate. The results revealed that uranium could be biomineralized on bacteria as UO2HPO4·4H2O or (UO2)3(PO4)2·4H2O. The influence of organic ligands on the biomineralization had clear-cut correlations with its complexation abilities to uranyl. It was clearly found that the U-phosphate biomineralization was affected noticeably by the strong ligands (oxalate and citrate). Further study discovered that when the organic ligands were uncompetitive with biotic PO43− for uranyl, the transformation of uranyl species from β-UO2(OH)2 colloidal particles to free UO22+-ligands ions could facilitate the U-phosphate biomineralization. However, when the organic ligands competed with biotic PO43− for uranyl, the U-phosphate biomineralization were inhibited. Our results highlight the importance of complex interactions of strong organic ligands with uranyl during the bacterial precipitation of UP compounds and thus for the mobilization and immobilization of radio-nuclides in the nature. Keywords: Uranium contamination, Bioremediation, Complexation, Organic ligands