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Abstract

The surface charge density (σ₀) of colloidal alumina (α-Al₂O₃) suspended in 1:1 electrolytes (NaCl, NaNO₃, CsCl and CsNO₃) at different electrolyte concentration (c₀) was determined using acid-base titration. The data were described in terms of the Triple Layer Model (TLM) of electric double layer. It was observed that the polarity of σ₀ could be varied through a point of zero charge (PZC) by varying the pH of the suspension. The PZCs were observed to occur at pH = 7.8 ± 0.1, 7.6 ± 0.2, 8.5 ± 0.1 and 8.3 ± 0.1 in NaCl, NaNO₃, CsCl and CsNO₃, respectively. It was concluded that the TLM adequately describes the titration data (within ±10%) in the pH and c₀ range of 10⁻⁴ ≤ c₀ ≤ 0.1 M, respectively.

Publisher Name

University of Dar es Salaam

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