The Electrical Double Layer at Hydrous Manganese Dioxide/Electrolyte Interface.
The interfacial properties of two hydrous oxides of manganese, namely an amorphous variety and a poorly crystalline synthetic birnessite, in different electrolyte media, have been studied by using a batch potentiometric titration procedure with a 72-h equilibration period. The data obtained by this procedure are more relevant to a natural water system than those obtained by the rapid titration method as reported earlier [J. Colloid Interface Sci. 131, 103 (1989).]. Although the points of zero charge do not show any major variations, the surface dissociation and complexation (with Na(+) in NaCl) constants differ with the method of titration. Both of the samples are characterized by their high surface charge (low DeltapK(a)) and surface potential, and as a result, complexation takes place possibly within the inner helmholtz plane. It is concluded that the triple-layer model is not applicable to this colloid system and that a basic Stern model would be more suitable in this case. Copyright 2001 Academic Press.
Tripathy
Sushree Swarupa
SS
Regional Research Laboratory, Bhubaneswar, Orissa, 751 013, India
Kanungo
Sukriti Bhusan
SB
Mishra
Santosh Kumar
SK