Surface Charging of Materials Other than Metal Oxides

For numerous samples of pure sparingly soluble metal oxides, the lEPs and PZCs (CIPs) obtained by titration matched or nearly matched. A matching PZC obtained 

Several models allow differences between the PZC, CIP, and lEP, and the equality of these quantities has been challenged in a few publications [638-641], even for sparingly soluble metal oxides. Rejection of the assumption that CIP = PZC implies that the correction for an acid or base associated with solid particles illustrated in Eigure 2.7 is not applicable, and the correction term in Equation 2.12 has to be determined by another means. 

With materials other than sparingly soluble metal oxides, the charging curves obtained at different ionic strengths often do not exhibit a CIP, and even if they do, it is not necessarily equal to the lEP. Discrepancies between CIP and lEP have been reported for various activated carbons [619]. 

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