Coagulation of submicron colloids in water treatment by incorporation into aluminum hydroxide floc
- Univ. of Arizona, Tucson (United States)
In a series of laboratory experiments it was observed that the rate and stoichiometry of aluminum hydroxide precipitation depended on pH and Al dose, and on HCO{sub 3}{sup {minus}}, SO{sub 4}{sup 2{minus}}, and natural organic matter concentrations. Incorporation of hydrous aluminum oxide colloids into the precipitate followed either of two paths. At pH 7.5 a loose floc formed; colloid removal involved subsequent aggregation of the colloids with the floc. At pH 6.5, the precipitate coated the seed particle surface; removal involved rapid self-coagulation of the colloids. Removal was {ge} 99.9% at both pH's. At pH 5.5, colloid removals were insignificant. Results suggest that heterogeneous nucleation and growth of precipitate at pH 6.5 gives destabilized particles and smaller, compact floc. The homogeneous pathway involving precipitation and subsequent particle aggregation was less efficient. The heterogeneous pathway had a lower precipitate OH/Al ratio and a lower electrophoretic mobility.
- OSTI ID:
- 5148697
- Journal Information:
- Environmental Science and Technology; (United States), Journal Name: Environmental Science and Technology; (United States) Vol. 25:10; ISSN ESTHA; ISSN 0013-936X
- Country of Publication:
- United States
- Language:
- English
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ADDITIVES
ALUMINIUM COMPOUNDS
ALUMINIUM HYDROXIDES
COLLOIDS
DISPERSIONS
FLOCCULATION
HYDROGEN COMPOUNDS
HYDROXIDES
KINETICS
OXYGEN COMPOUNDS
PERFORMANCE
PH VALUE
PRECIPITATION
REACTION KINETICS
SEPARATION PROCESSES
WATER TREATMENT PLANTS