A General Rate Law for Surface Controlled Dissolution

We would like to provide the reader first with a qualitative understanding of the subject of dissolution kinetics. 

The reactivity of the surface (Fig. 5.3), i.e., its tendency to dissolve, depends on the type of surface species present e.g., an inner-sphere complex with a ligand such as that shown for oxalate 

Similarly, surface protonation tends to increase the dissolution rate, because it leads to highly polarized interatomic bonds in the immediate proximity of the surface central ions and thus facilitates the detachment of a cationic surface group into the solution. On the other hand, a surface coordinated metal ion, e.g., Cu2+ or Al3+, may block a surface group and thus retard dissolution. An outer-sphere surface complex has little effect on the dissolution rate. Changes in the oxidation state of surface central ions have a pronounced effect on the dissolution rate (see Chapter 9). 

The ideas developed here are largely based on the concept of the coordination at the (hydr)oxide interface the ideas apply equally well to silicates. Somewhat modified concepts for the surface chemistry of carbonate, phosphate, sulfide and disulfide minerals have to be developed. 

Surface complex formation with ligands that form bidentate, mononuclear surface complexes, e.g., oxalate, salicylate, citrate, diphenols, etc. 

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