Fig. 1. Plots of 1/A vs. 1/c for tight Mn(II) binding by solid NHA at 20.0 °C and 30.0 °C and pH 2.0. The linear plots are consistent with one binding step.

Fig. 2. Plots of 1/A vs. 1/c for tight binding by solid NHA at 10.0 °C and 20.0 °C. The straight lines indicate one binding step at both temperatures.

Fig. 3. Plot of log K_A vs. 1/T for tight binding by solid NHA. The data are from Table 2.

Fig. 4. Plots of 1/A vs. 1/c for tight Hg(II) binding by solid NHA at different temperatures and pH 2.0.

Fig. 5. Plots of log K_i vs. 1/T for tight Hg(II) binding by solid NHA in steps O and A.

Fig. 6. Schematic views of metal binding by (a) a bidentate site [A₁, A₂] and (b) by two separated sites A₁ and A₂. The binding mode in (b) helps to explain the ability of metal-loaded HAs to encapsulate molecules like pyrene and prevent quenching of their fluorescence by species like Br⁻ (Engebretson and Von Wandruska, 1998).

Fig. 7. Correlation of enthalpy and entropy changes for metal binding by solid and dissolved HSs. The data are from Table 3 (solid HAs, filled circles) and Table 4 (dissolved HSs and acetate, filled triangles).

Analytical data for solid NHA

Isotherm parameters for metal binding by solid NHA at pH 2.0

Tight metal binding parameters for binding of metal cations by solid HAs

Thermodynamic parameters for metal binding by humic and fulvic acids and by acetate