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Competitive Adsorption of 2-Ketogluconate and Inorganic Ligands onto Gibbsite and Kaolinite

Biosystems Engineering and Soil Science Dep., 2506 E.J. Chapman Dr., Univ. of Tennessee, Knoxville, TN 37996-4531

View larger version (31K): [in this window] [in a new window]   Fig. 1. Schematic representation of possible 2-ketogluconate (kG) surface species according to the 1-pK basic Stern surface complexation model.

View larger version (24K): [in this window] [in a new window]   Fig. 2. The adsorption of 2-ketogluconate (kG) by gibbsite and kaolinite as a function of pH and ionic strength. In (a), the symbols represent experimentally determined kG adsorption and the solid lines represent the 1-pK basic Stern optimized fit to the experimental data using the chemical models described in Tables 2, 3, and 4. The dashed lines represent the model-predicted adsorption of kG by kaolinite using the surface complexation model developed for kG adsorption by gibbsite. The dotted lines represent the model-predicted adsorption of kG by gibbsite using the AlOH–1kG–1.5(s) species rather than the Al2O2H–1kG–(s) species. Graph (b) illustrates model-predicted adsorbed kG species composition as a fraction of the total predicted adsorbed kG for gibbsite (filled symbols) and kaolinite (open symbols).

View larger version (25K): [in this window] [in a new window]   Fig. 3. The adsorption of (a) PO4, (b) AsO4, and (c) SO4 by gibbsite (G) and kaolinite (K) as a function of pH and ionic strength. The solid lines represent the 1-pK basic Stern optimized fit to the experimental data using the chemical models described in Tables 2, 3, and 4. The dashed lines represent the model-predicted ligand adsorption by kaolinite using the surface complexation model developed for gibbsite.

View larger version (15K): [in this window] [in a new window]   Fig. 4. The single-ligand adsorption of 2-ketogluconate (kG) and the competitive binary-ligand (L) adsorption of kG and (a) PO4, (b) AsO4, (c) and SO4 at equal total concentrations of 0.1 mmol L–1 and 10 g gibbsite L–1 as a function of pH and ionic strength. The solid lines represent the 1-pK basic Stern optimized fit to the experimental data. The dashed lines represent the model-predicted adsorption of kG in the binary systems using the surface complexation model developed for adsorption in the single-ligand gibbsite system.

View larger version (15K): [in this window] [in a new window]   Fig. 5. The single-ligand adsorption of 2-ketogluconate (kG) and the competitive binary-ligand (L) adsorption of kG and (a) PO4, (b) AsO4, (c) and SO4 at equal total concentrations of 0.1 mmol L–1 and 10 g kaolinite L–1 as a function of pH and ionic strength. The solid lines represent the 1-pK basic Stern optimized fit to the experimental data. The dashed lines represent the model-predicted adsorption of kG in the binary systems using the surface complexation model developed for adsorption in the single-ligand gibbsite system.

View larger version (16K): [in this window] [in a new window]   Fig. 6. The single-ligand adsorption of (a) PO4, (b) AsO4, (c) and SO4 and the competitive binary adsorption of ligands (L) and 2-ketogluconate (kG) at equal total concentrations of 0.1 mmol L–1 and 10 g gibbsite L–1 as a function of pH and ionic strength. The solid lines represent the 1-pK basic Stern optimized fit to the experimental data. The dashed lines represent the model-predicted adsorption of kG in the binary systems using the surface complexation model developed for adsorption in the single-ligand gibbsite system.

View larger version (15K): [in this window] [in a new window]   Fig. 7. The single-ligand adsorption of (a) PO4, (b) AsO4, (c) and SO4 and the competitive binary adsorption of ligands (L) and 2-ketogluconate (kG) at equal total concentrations of 0.1 mmol L–1 and 10 g kaolinite L–1 as a function of pH and ionic strength. The solid lines represent the 1-pK basic Stern optimized fit to the experimental data. The dashed lines represent the model-predicted adsorption of kG in the binary systems using the surface complexation model developed for adsorption in the single-ligand gibbsite system.

View larger version (14K): [in this window] [in a new window]   Fig. 8. The influence of solution composition and preadsorbed PO4 or 2-ketogluconate (kG) on kG adsorption by gibbsite as a function of pH in 0.001 mol L–1 NaCl.

View larger version (18K): [in this window] [in a new window]   Fig. 9. The influence of solution composition and preadsorbed PO4 or 2-ketogluconate (kG) on PO4 adsorption by gibbsite as a function of pH in 0.01 mol L–1 NaCl.