Investigation of the Interaction of the Uranyl Group UO_2~2+ and Fe(III) with Natural Humic Acid in Aqueous Solutions by X-Ray Photoelectron Spectroscopy

摘要

Complexes of uranyl UO_2~2+ and Fe(III) withnatural humic acid (NHA) were synthesized. The reaction isheterogeneous, the NHA reacting as a particle. The concentrationsof the elements on the surface and inside this particle are different.In the absence of iron, uranyl reacts with NHA more completelythan Fe(III) with NHA in the absence of uranyl. However, in thejoint reaction of NHA with Fe(III) and uranyl, the NHApreferentially forms complexes with Fe(II). The UO_2~2+complexes in comparison with the Fe(III) complexes arepreferentially formed inside the NHA; consequently, when theparticles are ground, the U/Fe concentration ratio is increased.Accordingly, Fe(III) salts may be used to prevent migration ofuranyl in the form of soluble complexes with NHA. Natural humicacid and its complexes also contain small amounts of sulfate andRSH-type groups, the sulfate/sulfide ratio on the surface being 0.5,but the ratio decreases by a factor of two after grinding theparticles. The NR_2 group in the complex is found mainly in theionic form HNR_2~+.