Although oxidative reactivity of FeIII oxides as a single oxide has been extensively reported, we examined for the first time how the interactions between goethite and a second oxide affect the oxidative reactivity of goethite. Experiments showed that goethite reactivity was inhibited to different extents mainly due to heteroaggregation between oxide particles and the inhibition effect followed TiO2 > Al2O3 > SiO2. Soluble Al3+ or silicate of greater or less than 1-2.5 mM increased or decreased goethite reactivity, respectively. This is due to sorption of the ions by goethite, which at low concentrations prevents sorption of the formed Fe2+ but at high concentrations blocks reactive sites. With the addition of humic acid, alginate or pyrometallic acid to binary oxide mixtures, the net inhibition on goethite reactivity was less than the sum of that of the second oxide and the NOM. Adsorption of the NOM by both oxides has changed the heteroaggregation pattern that most likely contributed to the observed changes in goethite reactivity.

Oxidative reactivity of goethite in mixtures with secondary oxides and natural organic matter (NOM)

248th National Meeting (2014)

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