pH‐sensitive flocculation: Settling rates and sediment densities

Franks, George V.; Sepulveda, Carola V.; Jameson, Graeme J.

doi:10.1002/aic.10891

Cited by 16 publications

(11 citation statements)

References 21 publications

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“…Obviously, PNIPAM has an advantage over PAM because it produces denser sediments and slightly faster settling. Therefore, more water can be recovered, although the consolidation stage will take some time (typically 3 h or less) 15. The only disadvantages of using PNIPAM are that the supernatant clarity is not as good as conventional PAM and the cost of PNIPAM may be more than conventional polymeric flocculants.…”

Section: Resultsmentioning

confidence: 99%

“…The development of novel flocculants with better performance than PAM would be useful in managing tailings dewatering. One class of new flocculants are stimuli‐sensitive polymers,13, 14 such as chitosan and Polyacrylicacid (pH‐sensitive polymers),15 methylcellulose (a low MW temperature‐sensitive polymer),14 and poly( N ‐isopropyl acrylamide) (PNIPAM) (a temperature‐sensitive polymer) 2, 13, 16–19. These polymers have been tested in flocculating for example, TiO 2 with a 2 × 10 5 Da MW (weight average MW) PNIPAM,17 kaolin with a 3.95 × 10 6 Da MW (number or weight average not specified) PNIPAM,18 zircon with an 86,000 Da MW (approximately according to the manufacturer) methylcellulose,14 and kaolinite with 3.2 × 10 6 Da M n (number average MW) PNIPAM 19.…”

Section: Introductionmentioning

confidence: 99%

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Effect of molecular weight of poly(N‐isopropyl acrylamide) temperature‐sensitive flocculants on dewatering

2009

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(PNIPAM) (temperature-sensitive flocculant) on sedimentation rate, sediment density, and supernatant clarity of silica suspensions was investigated. The addition of PNI-PAM resulted in rapid sedimentation (T [ critical solution temperature, CST) and low sediment moisture (T \ CST). Higher MW polymers resulted in more effective flocculation and sediment consolidation. At 10 ppm, PNIPAM (3.6 million Da) produced 20 m/h settling rate and 48 vol % solids sediment density, whereas 0.23 million Da polymer produced 0.1 m/h settling rate. PNIPAM produces effective flocculation and consolidation by cycling the interparticle interactions between repulsion and attraction as temperature is cycled around the CST. The change in temperature produces a hydrophilic/hydrophobic transition of the polymer, influencing adsorption onto the surface and the inter-particle forces. Conventional polyacrylamide flocculants (not influenced by temperature), cannot be used to produce both rapid sedimentation and dense sediments.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Effect of molecular weight of poly(N‐isopropyl acrylamide) temperature‐sensitive flocculants on dewatering

2009

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“…The complexity of the surface modification is not an issue for applications such as biofilm growth prevention. , However, for industrial applications such as mineral flotation or tailings treatment, the polymer layers are formed through straightforward adsorption from aqueous solution. In this area, the study and application of stimulus-responsive polymers is still in its infancy, − in spite of the potential for stimulus-responsive polymers to improve mineral separation processes.…”

Section: Introductionmentioning

confidence: 99%

Reduction of Surface Hydrophobicity Using a Stimulus-Responsive Polysaccharide

et al. 2010

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The adsorption of carboxymethyl cellulose (CMC) onto a hydrophobic self-assembled monolayer has been characterized using the quartz crystal microbalance (with dissipation monitoring, QCM-D). Adsorption was studied as a function of initial solution conditions. CMC adsorbs to a greater extent at high ionic strength (10(-1) M KCl as opposed to 10(-2) M KCl) or low pH (3 as opposed to 9). The solution conditions that yielded the lowest initial adsorbed amount (10(-2) M KCl, pH 9) were used as a reference to investigate the response of the adsorbed layer to a switch in solution conditions after adsorption (i.e., to higher ionic strength (10(-1) M KCl) or lower pH (pH 3)). The adsorbed layer released significant amounts of hydration water after each solution switch, as determined by the QCM-D measurements. This expulsion of hydration water was fully reversible. For the two solution switches, reducing the solution pH resulted in a more pronounced change in the amount of hydration water within the adsorbed CMC, accompanied by a distinct conformational change, as determined from a QCM D-f plot. In addition to studying adsorption using QCM-D, the effect of adsorbed CMC on surface hydrophobicity has been investigated using captive bubble contact angle measurements. The effect of the polymer on the contact angle of the surface was seen to be greatest when adsorbed at low pH or at higher ionic strength. CMC was also seen to have a significantly enhanced ability to reduce the surface hydrophobicity after both the ionic strength and pH switches, lowering the advancing water contact angle by 6 and 23° and the receding water contact angle by 10 and 40° for the ionic strength and pH switches, respectively. As with the change in hydration water content, the change in the contact angle of the polymer-coated surface following the solution switches was reversible.

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“…This difference occurred because the positively charged DMDAAC well maintained in side chain of AM/A‐β‐CD/DMDAAC can flocculate the negatively charged kaolin through electrical neutralization . Moreover, the high molecular polymer with β‐CD can extend the chain through intermolecular and intramolecular hydrogen bonds and is more conducive to the settling of flocs …”

Section: Resultsmentioning

confidence: 99%

β‐Cyclodextrin modified cationic acrylamide polymers for flocculating waste drilling fluids

Zou

Liang

Xiu-li

et al. 2013

J of Applied Polymer Sci

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In this article, the P(AM/A-b-CD/DMDAAC) is used as flocculant. The synthesis and characterization of the cationic polyacrylamide flocculant modified by b-cyclodextrin have been studied in the early article. This article stresses its excellent flocculated performance and mechanism. In the flocculated process, the bridging flocculation played a dominant role. Through the flocculation experiments, it can be seen that the flocculating rate of the P(AM/A-b-CD/DMDAAC) on four solutions can go up to 93.4%, 89.7%, 85.1%, and 96.7%, respectively. As can be seen from experiment data, the flocculated property of P(AM/A-b-CD/DMDAAC) is superior to polyacrylamide and poly (dimethyl diallyl ammonium chloride).

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pH‐sensitive flocculation: Settling rates and sediment densities

Cited by 16 publications

References 21 publications

Effect of molecular weight of poly(N‐isopropyl acrylamide) temperature‐sensitive flocculants on dewatering

Effect of molecular weight of poly(N‐isopropyl acrylamide) temperature‐sensitive flocculants on dewatering

Reduction of Surface Hydrophobicity Using a Stimulus-Responsive Polysaccharide

β‐Cyclodextrin modified cationic acrylamide polymers for flocculating waste drilling fluids

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