1. Effects of Polymer Molecular Weight on Adsorption and Flocculation in Aqueous Kaolinite Suspensions Dosed with Nonionic Polyacrylamides.
- Author
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Byung Joon Lee and Schlautman, Mark A.
- Subjects
POLYACRYLAMIDE ,FLOCCULATION ,KAOLINITE ,MEASUREMENT of viscosity ,ADSORPTION capacity - Abstract
The effects of polyacrylamide (PAM) molecular weights (MWs) on the PAM adsorption capacities and PAM-mediated flocculation of kaolinite suspensions were investigated using a series of nonionic PAMs with different MWs. Adsorption tests using aqueous kaolinite suspensions dosed with a series of PAMs with MWs of 1.5 kg/mol, 10 kg/mol, 0.6-1 Mg/mol, 5-6 Mg/mol, and 18 Mg/mol (referred to as 1.5 K, 10 K, 0.6-1 M, 5-6 M, and 18 M PAMs) indicated that the adsorption capacity of the kaolinite for PAM increased with increasing MW. However, the capacity for 18 M PAM was 20 times smaller than those for the 0.6-1 M and 5-6 M PAMs, although it has the highest MW. In steady-shear viscosity tests, a 1 g/L stock solution of 18 PAM was found to cause polymeric chain entanglements, which reduced the adsorption capacity. The 0.6-1 M and 5-6 M PAMs were further used in flocculation tests, in order to investigate the effect of PAM MW on the flocculation capability. The 5-6 M PAM was found to have higher flocculation capabilities than 0.6-1 M PAM; 5-6 M PAM was more subject to nonequilibrium flocculation, resulting in the development of unstable, stretched polymeric structures on solid surfaces and increasing particle-particle bridging and flocculation. Higher-MW PAMs are more effective flocculation agents, because of their higher adsorption capacities and flocculation capabilities. However, an extremely high-MW PAM, such as 18 M PAM, decreases adsorption/flocculation, and the preparation and handling of working solutions become difficult, because of polymeric chain entanglements. [ABSTRACT FROM AUTHOR]
- Published
- 2015
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