Study Of The Biomineralization Process And Mechanism Of Uranium In The Presence Of Phytic Acid Or Siderophore

Uranium is commonly found in natural minerals,on the surface and in the subsurface environment in the form of uranyl ions(UO₂²⁺)of oxidized state.UO₂²⁺has a complex configuration and active properties that lead to complex interactions with natural environmental media.However,the process and mechanism of the influence of the cellular metabolism of organic media on uranium biomineralization in the real environment are not yet clear.In this dissertation,the dominant strain of S.putrefaciens as a model microorganism and phytic acid（IP₆）and hydroxyformic acid-type iron carrier（DFOB）,which are widely present in environmental media and closely related to phosphorus and iron metabolism,respectively,were selected as biocharacteristic organic molecules.By means of batch adsorption experiments,microscopic characterization and spectroscopic analysis,combined with quantum chemical theoretical calculations,the critical dominant factors of phytic acid/siderophore to prevent U（VI）biomineralization and the spatio-temporal effects leading to the inhibition differences were preliminarily investigated.From a combination of macroscopic experiments,microscopic characterization to quantum chemical theoretical calculations,the processes of complexation of phytic acid/siderophore with U（VI）,co-precipitation of Ca²⁺and Mg²⁺,phytic acid with U（VI）,and regenerated minerals due to highly specific of DFOB to Fe³⁺,molecular isomeric geometry,relative energies,hydrogen bonding patterns,bonding orbitals and ligand structure information of phytic acid/siderophore clusters were analyzed qualitatively and quantitatively.The rules and mechanisms of the influence of common environmental media（organic matter-inorganic cations-microorganisms）on the fugitive forms of U（VI）in the environment were explored from the viewpoint of the formation of hydrogen bonding networks and molecular reconfiguration.The main findings are as follows:Phytic acid has a significant inhibitory effect on the removal of U（VI）by S.putrefaciens,which decreased from 382.77 mg/g to 102.45 mg/g.The inhibition was mainly due to the strong chelating effect of phytic acid on U（VI）through an extensive hydrogen bonding network between monomers and clusters,leading to the formation of amorphous colloidal polymers present in the solution,thus hindering the formation of biogenic uranium mineralizers.Under the conditions of the coexistence of Mg²⁺/Ca²⁺and phytic acid,phytic acid preferentially binds Mg²⁺/Ca²⁺via ionic bonds while these could carry free uranyl ions in the solution to form amorphous minerals,thus alleviating the inhibitory effect of phytic acid in solution by breaking the hydrogen bonding network,but the bioinduced mineralization effect of uranium is still suppressed.Thus,this mechanism can be explained as follows:The Combination of Mg²⁺/Ca²⁺with phytic acid is relieved the inhibits effect by disrupting the hydrogen bonding network,but the bioinduced mineralization effect of uranium is still inhibited.The organic ligand DFOB,due to its extensive intra-and intermolecular hydrogen bonding network,has a stronger complexing ability with uranyl ions than active functional groups on the cell surface.Thus the soluble complex（DFOB-U（VI））in the solution also exhibits a strong inhibitory effect on U（VI）binded by S.putrefaciens,and the biogenic uranium mineralization products are partially dissociated by DFOB.In uranium and bacteriophage reaction systems,the delayed addition of DFOB will slow down the inhibitory effect of uranium mineralization.The complexation preference of DFOB to cationic systems is shown by:Fe³⁺+UO₂²⁺>Fe³⁺>UO₂²⁺.Therefore,in the DFOB and Fe³⁺coexistence system,the high specificity of DFOB for Fe³⁺will force the dissociation of uranium from the DFOB-U complex,thus facilitating the process of uranium biomineralization reaction.This study investigated the behavior of simulated microorganisms on the influence of common environmental media:organic matter（phytic acid,siderophore）and common cations(Ca²⁺,Mg²⁺,Fe³⁺)on the biomineralization of uranium and their mechanisms of action.It is a fundamental exploration of the effective sequestration method of uranium in anthropogenically enhanced contaminated environments,which can provide a reference for the study of biogeochemical processes in the migration transformation of real uranium-contaminated sites.