Chemistry and structure of aggregates formed with Fe-salts and natural organic matter

Influence of Addition Order and Contact Time on Thorium(IV) Retention by Hematite in the Presence of Humic Acids

“…solid-humic-metal, revealed that the additivity rule cannot be simply applied (46)(47)(48). As a matter of fact, a large number of authors has clearly shown that slow sorption kinetic, fractionation phenomena and solid phase dissolution were implied (9,12,(61)(62)(63)(64)(65)(66). Thus, a reliable thermodynamic modelling of these systems is difficult to assess without prior assessment of an actual equilibrium state.…”

The Iron Biogeochemical Cycle Past and Present

“…Adsorbed fulvic acids are able to slow down the rate at which ferrihydrite transforms to more stable (oxyhydr)oxides by blocking dissolution sites or hindering the nucleation of the more stable phases (Jones et al, 2009). Might the retardation effects on transformation (Vilge-Ritter et al, 1999) be less efficient with discontinuous coatings or with coprecipitated organic matter? A more mineralogical-based approach to the filterable Fe fraction in seawater should be high on everyone's wish list.…”

Competitive effect of iron(III) on metal complexation by humic substances: Characterisation of ageing processes

“…Concerning the mechanism of flocculation, there is some controversy about whether organic compounds are scavenged by adsorption onto precipitated iron hydroxide colloids (Ying et al, 1988;Tseng et al, 1989) or the organic colloids are precipitated as a consequence of charge compensation by dissolved Fe (Schmitt et al, 1996;Vilgé-Ritter et al, 1999;Cheng, 2002;Jung et al, 2005). In fact, precipitates of humic acid and colloidal iron hydroxide look very similar.…”

“…In flocculated Fe/HA precipitates, the presence of iron oligomers could be detected by X-ray spectroscopy (Vilgé-Ritter et al, 1999;Jung et al, 2005).…”