The shear degradation of high-molecular-weight flocculant solutions

Abstract

SYNOPSISSolutions of polyacrylamide and poly(acry1amide-co-sodium acrylate) flocculants with varying molecular weights were shear degraded under a range of mixing conditions. The viscosity and flocculant activity of the solutions generally decreased with time to limiting values dependent on the mixing intensity. The activity of 10 and 20% anionic flocculants displayed quite different trends from those for nonionic flocculants of equivalent molecular weight, with less apparent degradation due to mixing, particularly at low dosages. However, viscosity measurements on sheared solutions diluted with a salt buffer suggest that nonionic and anionic flocculants with similar initial molecular weights were degraded to the same degree. Multiangle laser light-scattering measurements were used to confirm that the shearing process resulted in a reduction in molecular weight which was independent of anionic character. The apparent shear resistance of anionic flocculants observed from activity measurements was attributed to different flocculation mechanisms for the nonionic and anionic flocculants. 0 1996 John Wiley & Sons, Inc.

Study on chain deformation of polyacrylamides in solutions and its flocculation performance during the flocculation process

“…Polyacrylamide (PAAm) is one of the widely used organic flocculants for wastewater treatment 1, 2. The flocculation performance of PAAm flocculants primarily depends on the type of flocculants, the ionic‐PAAm and nonionic‐PAAm,3, 4 the ionic content,5 the molecular weight,6, 7 the type of wastewater, and their suspensions concentrations,8 and also depends on some operation processes such as the shear rate 9. In our previous work,10, 11 the effect of the flocculant dose and the parent solution concentration on the flocculation performance of PAAm flocculants has also been documented.…”

Adsorption behavior and shear degradation of ultrahigh‐molecular‐weight hydrolyzed polyacrylamide in a capillary flow

“…The degradation of polymer solution is classified into light degradation, thermal degradation, biodegradation, chemical degradation, and mechanical degradation . It should be mentioned that all other conditions on the capillary experiments are kept the same except flow rate.…”

Depressing effect of flocculants on molybdenite flotation

“…Shear degradation of polyacrylamides is well documented (Scott et al, 1996). Sheared flocculant solutions show reduced viscosity, and reduced performance as flocculants (Henderson and Wheatley, 1987).…”