Zero point charge and surface stability constants for Co2+ adsorption fromaqueous solutions on kaolin

Surface charge of kaolin was estimated from the potentiometric titrations o f kaolin in various background electrolyte solutions at 298 IC No point of intersection for the zero charge was observed at pH 3.5 as the starting poi nt indicating that at low pH, the amorphous components of kaolin were adsor bed in the aqueous phase whereas the three various electrolyte solutions in itially adjusted to about pH 8.48 gave the point of intersection The pH(PZC ) was 5.96. The surface stability constants were measured in the temperatur e range (298 - 328 K) at pH 6.5. As the reaction was exothermic, like X-m, the maximum adsorption the values of the stability constants also decreased with increasing temperature showing high strength of bond between the adso rbent and adsorbate at low temperatures.