Goethite ligand promoted dissolution

As shown in Figure 13.19a, phosphate and borate inhibit the dissolution of goethite by H2S. Similarly, the dissolution of lepidocrocite (7-FeOOH) by EDTA (Y" ) is inhibited by phosphate and arsenate (Figure 13.19b). Both in the reductive dissolution (by H2S) and the ligand-promoted dissolution (by... 

Fig. 7.15 Inhibitation of reductive- and ligand-promoted dissolution of iron oxides by oxoanions. a The dissolution of goethite by H S is inhibited by borate and phosphate, b The dissolution of lepidocrocite by EDTA is inhibited by phosphate and arsenate (adopted from Stumm and Morgan 1996, original data from Biber et at, 1994).

Examples include the oxalate (10 M) promoted dissolution of goethite, hematite and ferrihydrite over the pH range 3-5 (Fig. 12.2) in the absence of the ligand, dissolution at this pH is essentially zero (Stumm et al., 1985). 

FtG. 3.11. Tests of the rate law in Eq. 3.64 for albite,9 anorthite [C. Amrhein and D. L. Suarez, The use of a surface complexation model to describe the kinetics of ligand promoted anorthite dissolution, Geochim. Cosmochim. Acta 52 2785 (1988)], goethite,36 and S-A1203.36 A linear plot is consistent with the rate law. 

Holmen B. A. and Casey W. H. (1996) Hydroxymate ligands, surface chemistry, and the mechanism of Ugand-promoted dissolution of goethite [a-FeOOH(s)]. Geochim. Cosmochim. Acta 60, 4403-4416. 

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