Variations in the molecular weight response of anionic polyacrylamides under different flocculation conditions

Costine, Allan; Cox, James P.; Travaglini, Shaun; Lubansky, A.S.; Fawell, Phillip D.; Misslitz, Holger

doi:10.1016/j.ces.2017.10.031

Cited by 63 publications

(27 citation statements)

References 37 publications

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“…Aggregate density and hindered settling profiles of kaolin suspension flocculated with high and low molecular weight anionic polyacrylamide under mild mixing. Reproduced with permission . Copyright 2018, Elsevier.…”

Section: Performance Assessment Of Flocculantsmentioning

confidence: 99%

“…This method has gained much attention recently in the characterization of aggregates and sediment structures formed in the polymer flocculation of mineral and oil sands tailings, from which quantitative evaluation of polymer microstructure on aggregate structure has also been possible. [231,246,248,249] In a recent work, Costine et al [231] characterized the structure of aggregates formed by polymer flocculation of oil sands tailings using two different classes of flocculants and found out that sediments with hyperbranched functionalized polyethylene (HBf PE) produced denser aggregates than with anionic polyacrylamide, giving access to faster dewatering as indicated by CST measurements.…”

Section: Aggregates Characterizationmentioning

confidence: 99%

“…Another example is the work by Costine et al, where the authors used the settling velocities and density measurements (Figure 47) to study kaolin flocculation response to variations in average molecular weight of a series of anionic polyacrylamides of the same average anionicity under tight shear control in a continuous coquette flocculator. [249] The authors found out that flocculation response to variations in molecular weight is a strong function of the applied mixing intensity. When the applied mixing was mild, they observed that low molecular weight flocculant consistently formed denser aggregates and more dose-effective settling profiles, giving access to faster settling velocity in low (starving) dosages.…”

Section: Aggregates Characterizationmentioning

confidence: 99%

See 2 more Smart Citations

Water Soluble Polymer Flocculants: Synthesis, Characterization, and Performance Assessment

Vajihinejad

Gumfekar

Bazoubandi

et al. 2018

Macro Materials & Eng

137

108

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Water soluble polymer flocculants are important constituents of solid–liquid separation units for the treatment of a variety of process‐affected effluents. The systematic development of a flocculant relies on a good understanding of flocculation process, polymer synthesis, polymer characterization, and, not the least, flocculation performance assessment as desired for a particular treatment process, all of which are essential to establish meaningful relationships between flocculant microstructure and flocculation efficiency. The aim of this article is to communicate the bigger picture of this research area to the readers. The recent advances in the application of bio/natural, synthetic, and stimuli‐responsive flocculants are reviewed. Then, the basic polymer reaction engineering tools to control the microstructure of flocculants are provided and the techniques for the quantification of flocculant microstructure are concisely discussed. This is followed by a review of the methods used for the characterization of particle‐polymer force measurement, and flocculation/dewatering assessment with attention to the characterization of aggregate structures.

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Section: Performance Assessment Of Flocculantsmentioning

confidence: 99%

Section: Aggregates Characterizationmentioning

confidence: 99%

Section: Aggregates Characterizationmentioning

confidence: 99%

See 1 more Smart Citation

Water Soluble Polymer Flocculants: Synthesis, Characterization, and Performance Assessment

Vajihinejad

Gumfekar

Bazoubandi

et al. 2018

Macro Materials & Eng

137

108

View full text Add to dashboard Cite

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“…Whereas little information is available on the impact of seawater in the gravity thickening process, there is ample evidence of the influence of salinity on the flocculation mechanisms [8][9][10]. For example, Costine et al [11] analyzed continuous flocculation of kaolin sludge with anionic polyacrylamides of varying molecular weights. Continuous flocculation was achieved in a Couette mixer with a vertical flow arrangement, which allows the settling rate to be measured independently of the operator under controlled mixing conditions.…”

Section: Introductionmentioning

confidence: 99%

Analysis of Kaolin Flocculation in Seawater by Optical Backscattering Measurements: Effect of Flocculant Management and Liquor Conditions

Jeldres

MacIver

et al. 2020

Minerals

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Optical backscattering (OBS) signal values were used to evaluate the flocculation of kaolin slurries and seek the implications of using seawater. Two anionic flocculants were applied to kaolin suspensions at several dosages and in water of varying pH and electrolyte concentration. An OBS height scan method was used to estimate the degree of aggregation, supernatant quality, and solids concentration of the sediments. The residual solids of the supernatant depended of the extent of particle coagulation before flocculant was added, where the pH and salinity displayed a significant impact on flocculation. The OBS results were highly sensitive to the presence of fine particles, which was estimated in parallel from the focused beam reflectance measurements (FBRM.) In seawater, without flocculant added, the samples had increased root-mean-square scattering (Frms) values and larger final sediment volume than samples prepared in water with lower electrolyte concentration. This indicates a higher initial state of aggregation of the particles in seawater. Then, the aggregation degree was best linked to the square-weighted chord length distribution of the FBRM data, which intensifies the sensitivity to coarse aggregates.

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“…highly diluted) individual aggregates and the measurement of both their size and settling rate. Plots of these free (unhindered) settling rates as a function of size provide a strong indication of aggregate density (Costine et al 2017), and the density versus size relationships can be derived through application of a modified version of Stokes' law, as described below.…”

Section: Aggregate Density Measurementsmentioning

confidence: 99%

Understanding factors affecting the stability of inline polymer-amended tailings

Costine¹,

Benn²,

Fawell³

et al. 2018

Proceedings of the 21st International Seminar on Paste and Thickened Tailings

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Tailings rehabilitation, using soil-like properties with chemical and physical stability, can be influenced by surface forces on a particle scale and microstructure. Non-homogeneous structures, manifesting as particle aggregation, alter the permeability/porosity and improve the balance of aerated and water-filled pores that then favours plant growth. Polymer flocculation in tailings thickeners yields large, weak aggregates that are sheared in beds and on pumping. While low-level residual structure may remain, sizes are small and downstream polymer impacts are minor. However, high polymer dosages added in-pipe to high-solids streams lead to further water recovery on deposition, and while this process is poorly understood, it gives aggregates that are likely denser and stronger. If such structures persist, they could potentially offer closure and rehabilitation benefits in some applications. A high-solids (50 wt%) thickener underflow analogue (kaolin, silt, and fine sand) was treated with anionic polyacrylamide (PAM) polymers at elevated dosages (up to 1,000 g t-1) to establish if aggregate structures created during inline tailings flocculation survive or change over longer-term consolidation. Low and high molecular weight (MW) PAM polymers of fixed anionicity (30%) were tested. Focused beam reflectance measurement (FBRM) provided real-time monitoring of the aggregation state after polymer addition. The compressibility of the inline flocculated tailings was assessed over an eight week period. Variations in the size-density relationship of aggregate structures were determined over this period using an image analysis technique, revealing that the shorter polymer chains produced denser, more compact structures immediately after deposition, whereas the longer chains resulted in a much slower re-conformation of the partially adsorbed polymer, leading to additional densification over time. Eight weeks after deposition, inline flocculated tailings produced with the low MW polymer were characterised by a higher compressive yield stress compared with the high MW polymer, consistent with the formation of smaller, more rigid aggregate structures with the shorter chains. The potential impact of such structures on longer-term rehabilitation properties (e.g. metal/metalloid ion adsorption and surface exchange capacity) of the treated tailings is discussed.

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Variations in the molecular weight response of anionic polyacrylamides under different flocculation conditions

Cited by 63 publications

References 37 publications

Water Soluble Polymer Flocculants: Synthesis, Characterization, and Performance Assessment

Water Soluble Polymer Flocculants: Synthesis, Characterization, and Performance Assessment

Analysis of Kaolin Flocculation in Seawater by Optical Backscattering Measurements: Effect of Flocculant Management and Liquor Conditions

Understanding factors affecting the stability of inline polymer-amended tailings

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