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Water 2015, 7(11), 5896-5909;

Effects of Polymer Molecular Weight on Adsorption and Flocculation in Aqueous Kaolinite Suspensions Dosed with Nonionic Polyacrylamides

Department of Construction and Environmental Engineering, Kyungpook National University, 2559 Gyeongsang-daero, Sangju, Gyeongbuk 742-711, Korea
Department of Environmental Engineering & Earth Sciences, Clemson University, Anderson, SC 29625-6510, USA
Author to whom correspondence should be addressed.
Academic Editor: Wilhelm Püttmann
Received: 25 September 2015 / Revised: 22 October 2015 / Accepted: 22 October 2015 / Published: 28 October 2015
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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. View Full-Text
Keywords: polyacrylamide; adsorption; reconfiguration; nonequilibrium flocculation polyacrylamide; adsorption; reconfiguration; nonequilibrium flocculation

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Lee, B.J.; Schlautman, M.A. Effects of Polymer Molecular Weight on Adsorption and Flocculation in Aqueous Kaolinite Suspensions Dosed with Nonionic Polyacrylamides. Water 2015, 7, 5896-5909.

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