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Surface Titrations of Perlite Suspensions
Journal of Colloid and Interface Science
|October 21, 1998
Summary
Perlite samples exhibit a negative surface charge across a pH range of 3-10, with no point of zero charge detected. This behavior was consistent in both potassium nitrate (KNO3) and sodium chloride (NaCl) solutions.
Area of Science:
- Materials Science
- Surface Chemistry
- Geochemistry
Background:
- Perlite, a volcanic glass, possesses unique surface properties influenced by its geological origin.
- Understanding perlite's surface charge is crucial for applications in soil amendment, filtration, and construction materials.
Purpose of the Study:
- To investigate the surface charge behavior of unexpanded and expanded perlite.
- To determine the effect of pH and ionic strength on perlite's surface charge in KNO3 and NaCl solutions.
Main Methods:
- Potentiometric titration was employed to measure the surface charge of perlite samples.
- The double extrapolation method was utilized to calculate intrinsic equilibrium constants.
Main Results:
- Perlite samples demonstrated a consistent negative surface charge within the pH range of 3-10.
- No point of zero charge was observed for either unexpanded or expanded perlite.
- Intrinsic equilibrium constants (pKinta2, p*KintK+, p*KintNa+) were determined for both perlite types in varying ionic strength solutions.
Conclusions:
- Perlite's surface is predominantly negatively charged under typical environmental conditions.
- The surface charge characteristics are influenced by the type of electrolyte (KNO3 vs. NaCl) and perlite's expansion state.