The existence of a variable surface charge in the tropical residual soils may be an important consideration with respect to the use of these soils for geoenvironmental containment applications, such as soil liners for waste containment in landfills and impoundments, or as constituent materials in permeable reactive barriers for in situ groundwater remediation. In such cases, the point of zero charge (PZC) for the soil plays a fundamental role in determining its adsorption behavior. Accordingly, measurements of the PZC for a Dark-red latossol from Sao Paulo were performed using the potentiometric titration methodology. The measurements resulted in a PZC range from 4.0 to 4.5 (pH units), which is in general agreement with previously published PZC data for soils with amphoteric adsorption behavior.
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