Net Charge Characteristics of Dystrandept B and Theoretical Prediction1
- Koji Wada and
- Yutaka Okamura2
The net charge characteristics of five Dystrandept B samples containing components with variable charge were described by combining the two empirical equations that relate the retention of NH4+ and Cl- with the pH (4 to 8) and NH4Cl concentration (0.005 to 0.1M) of the solution. There were two characteristic pH values; the point of zero charge (PZC) and the point of constant charge (PCC). The variation of PZC with NH4Cl concentration was appreciable, whereas that of PCC was very small or insignificant. The PZC was found in the range from pH 4.4 to 6.3, and the PCC pH was 4.9 to 6.0. The small net charge at PCC was positive for the soils containing allophane and imogolite and negative for the soil containing 2:1 layer silicates and gibbsite but not containing allophane and imogolite. The effects of the pH and NH4Cl concentration on the magnitude of the net charge are compatible with those calculated using the Stern theory of the electric double layer with an assumption that the thickness of the Stern layer (0.3 to 0.5 nm) decreases with increasing electrolyte concentration. The order of magnitude of the net charge measured is in agreement with that calculated.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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