Nucleation of flocs in dilute colloidal suspensions

Journal Article · Wed Nov 01 04:00:00 EST 1989 · Journal of the American Ceramic Society; (USA)

DOI:https://doi.org/10.1111/j.1151-2916.1989.tb06047.x· OSTI ID:7224879

Agrawal, D C; Raj, R; Cohen, C ^[1]

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1. Dept. of Materials Science and Engineering, School of Chemical Engineering, Cornell Univ. Ithica, NY (US)

In contrast to earlier theories which assume that coagulation of particles in dilute colloidal suspensions occurs by random collisions, the authors present evidence that coagulation is limited by a nucleation and growth phenomenon, typical of a phase transformation. They 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 {zeta} potential, where the particles strongly attract, do not peptize when the pH is changed to high {zeta} potential, where the attraction is weak. The experiments were carried out with aqueous dispersions of alumina particles. The timedependent 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.

• OSTI ID: 7224879
• Journal Information: Journal of the American Ceramic Society; (USA), Journal Name: Journal of the American Ceramic Society; (USA) Vol. 72:11; ISSN 0002-7820; ISSN JACTA
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360202* -- Ceramics
Cermets
& Refractories-- Structure & Phase Studies
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400102 -- Chemical & Spectral Procedures
400201 -- Chemical & Physicochemical Properties
AGGLOMERATION
ALUMINIUM COMPOUNDS
ALUMINIUM OXIDES
AQUEOUS SOLUTIONS
CHALCOGENIDES
COLLOIDS
DISPERSIONS
ENTROPY
FLOCCULATION
MIXTURES
NUCLEATION
OXIDES
OXYGEN COMPOUNDS
PARTICLE SIZE
PHASE TRANSFORMATIONS
PHYSICAL PROPERTIES
PRECIPITATION
SEPARATION PROCESSES
SIZE
SOLUTIONS
SPECTROSCOPY
THERMODYNAMIC PROPERTIES