Humic acids thorium complexes

Humic acids and fulvic acids interact with a wide variety of cations. In addition to interacting with iron and aluminium, the species with which they are complexed in soils (57), they also form stable complexes with zirconium, thorium, the lanthanides and the uranyl ion. In the case of uranium it has been suggested that humic acids could be of considerable importance in the geological formation of secondary deposits of uranium (58). 

Removal of Radioisotopes Some data also exists for the removal of the radioactive element thorium (Th) by nanomaterials. The experiment utilizing Ti02 nanoparticles to remediate Th(IV) contamination was conducted specifically with contaminated soils. Experiments conducted in the presence or absence of soil humic acid and fulvic acid demonstrated that both the fulvic and humic acids increased the sorption of Th(lV) to Ti02 nanoparticles at acidic pH (90). Bare Ti02 nanoparticles by themselves were able to form surface complexes with 94% of the available Th(IV) this percentage increased to 97%-98% in the presence of fulvic or humic acids and remained stable with increasing pH. This technique could be utilized to remediate soils contaminated with Th(TV), and in fact would likely be more effective in soils than in water. 

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