Mv. Biber et al., THE COORDINATION CHEMISTRY OF WEATHERING .4. INHIBITION OF THE DISSOLUTION OF OXIDE MINERALS, Geochimica et cosmochimica acta, 58(9), 1994, pp. 1999-2010
The surface coordinative chemical model of mineral dissolution-surface
chemical interaction with H+, OH-, metal ions, and ligands to form an
array of surface complexes whose reactivities determine the mechanism
s of many surface-controlled processes-has been successfully applied t
o interpret and quantify proton and ligand dependent dissolution rates
of oxides and silicates. Here this model is extended to include the e
ffects of inhibition. Experimental data are presented on the various f
actors which enhance and inhibit the nonreductive dissolution and the
reductive dissolution (by H2S) of various Fe(III)(hydr)oxides (alpha-F
e2O3, alpha-FeOOH, and gamma-FeOOH). The effects observed with iron ox
ides are similar to those expected to occur with other oxide and alumi
numsilicate minerals. Special attention is paid to the effects of chan
ges in surface protonation brought on by the binding of cations and an
ions to the surface. Binuclear surface complexes, especially those for
med by the adsorption of oxoanions such as phosphate, arsenate, borate
, and sulfate, are particularly good at inhibiting both the reductive
and nonreductive dissolutions of a reference system of iron(III) oxide
s. This phenomenon is due to (1) the large activation energy which mus
t be overcome to simultaneously detach two surface metal centers and t
o (2) the lack of additional surface protonation when uncharged binucl
ear or multinuclear complexes are formed.