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Issue 42, 2018
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In situ polymer flocculation and growth in Taylor–Couette flows

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Abstract

Flocculation of small particulates suspended in solution is a key process in many industries, including drinking water treatment. The particles are aggregated during mixing to form larger aggregates, known as flocs, through use of a polyelectrolyte flocculant. The flocculation of these particulates in water treatment, however, are subject to a wide spatial variation of hydrodynamic flow states, which has consequences for floc size, growth rate, and microstructure. Floc assembly dynamics are explored here using a commercially available cationic polyacrylamide, commonly used in water treatment, and anisotropic Na-bentonite clay particles under a variety of hydrodynamic mixing conditions. A Taylor–Couette cell with the unique ability to radially inject fluid into the rotating annulus was used to study how specific hydrodynamic flow fields affect assembly and structure of these materials during the flocculation process. Faster floc growth rates and decreased floc fractal dimensions were observed for higher order flow states, indicating improved mass transfer of the polymer flocculant and breakage at the edges of the flocs (shear rounding), respectively. This work sheds more light on the complexities of polymer-induced flocculation, towards improving dosing and efficiency of large-scale operations.

Graphical abstract: In situ polymer flocculation and growth in Taylor–Couette flows

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Publication details

The article was received on 17 Aug 2018, accepted on 06 Oct 2018 and first published on 08 Oct 2018


Article type: Paper
DOI: 10.1039/C8SM01694A
Citation: Soft Matter, 2018,14, 8627-8635
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    In situ polymer flocculation and growth in Taylor–Couette flows

    A. Metaxas, N. Wilkinson, E. Raethke and C. S. Dutcher, Soft Matter, 2018, 14, 8627
    DOI: 10.1039/C8SM01694A

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