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Nucleation of Flocs in Dilute Colloidal Suspensions
Author(s) -
Agrawal Dinesh C.,
Raj Rishi,
Cohen Claude
Publication year - 1989
Publication title -
journal of the american ceramic society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.9
H-Index - 196
eISSN - 1551-2916
pISSN - 0002-7820
DOI - 10.1111/j.1151-2916.1989.tb06047.x
Subject(s) - nucleation , coagulation , flocculation , colloid , chemical physics , economies of agglomeration , particle (ecology) , colloidal particle , chemistry , chemical engineering , phase (matter) , materials science , thermodynamics , physics , psychology , oceanography , organic chemistry , psychiatry , engineering , geology
In contrast to earlier theories which assume that coagulation of particles in dilute colloidal suspensions occurs by random collisions, we present evidence that coagulation is limited by a nucleation and growth phenomenon, typical of a phase transformation. We show that suspensions of well‐dispersed particles, which are almost indefinitely stable, flocculate rapidly when seeded with pregrown flocs. The nucleation argument is supported further by the observation that flocs which are grown at low ζ potential, where the particle strongly attract, do not peptize when the pH is changed to high ζ potential, where the attraction is weak. The experiments were carried out with aqueous dispersions of alumina particles. The time‐dependent change in cluster sizes was measured by in situ photon correlation spectroscopy. The observations raise the question of agglomeration as a phase transformation, involving a change in entropy, when the system moves from a dispersed to a flocculated state.