Influence of polymer adsorption and conformation on flocculation and dewatering of kaolin suspension

Besra, Laxmidhar; Sengupta, Dilip K.; Roy, Sunanda; Ay, Peter

doi:10.1016/j.seppur.2003.10.001

Cited by 100 publications

(50 citation statements)

References 16 publications

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“…On the other hand, coverage of particles was comparably lower in the case of AS#1. It is known that complete coverage of surfaces with polymers adsorbed with flat configuration would lead to steric repulsion resulting in stable suspensions (Besra et al 2004). Our SEM data indicate that the lower performance of AS#4 compared to AS#1 could result from a higher or even full coverage of suspended particle surfaces by this.…”

Section: Characterization Of Flocs Using Semmentioning

confidence: 75%

Guluronic acid content as a factor affecting turbidity removal potential of alginate

Moral

Ertesvåg

Sanin

2016

Environ Sci Pollut Res

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Alginates are natural polymers composed of mannuronic and guluronic acid residues.They are currently extracted from brown algae, however, alginate can also be synthesized by some species of Azotobacter and Pseudomonas. Alginates with different proportion of mannuronic and guluronic acids are known to have different characteristics and form gels at different extents in the presence of calcium ions. The aim of this work was to investigate the usefulness of alginate as a non-toxic coagulant used in purification of drinking water. This study utilized alginates from Azotobacter vinelandii having different guluronic acid levels. These were obtained partly by changing the cultivation parameters, partly by epimerizing a purified alginate sample in vitro using the A. vinelandii mannuronan-C-5-epimerase AlgE1. The different alginates were then used for coagulation together with calcium. The results showed that turbidity removal capability was dependent on the content of guluronic acid residues. For the best performing samples the turbidity decreased from 10 NTU to 1 NTU by the use of only 2 mg/L of alginate and 1.5 mM of calcium chloride.

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Section: Characterization Of Flocs Using Semmentioning

confidence: 75%

Guluronic acid content as a factor affecting turbidity removal potential of alginate

Moral

Ertesvåg

Sanin

2016

Environ Sci Pollut Res

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“…The isoelectric point of the kaolin in the present investigation is found to lie in pH 2.5 and is about 0.3 units higher than the reported values. 18 At pH < 2.5, kaolin particles display a net positive zeta potential due to the protonation of the surface of kaolin. At pH > 2.5, kaolin particles display a net negative zeta potential due to the deprotonation of the surface.…”

Section: Effect Of Flocculant Dosage and Ds On Flocculationmentioning

confidence: 99%

Flocculation properties and adsorption kinetics of cationic starches in kaolin suspensions

Chen

Liu

Wang

2007

J of Applied Polymer Sci

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The flocculation characteristics of cationic starches with degree of substitution (DS 0.32-0.63) have been evaluated in 1.0 wt % kaolin suspension by spectrophotometry and colloid titration. Cationic starch is found to be an effective flocculant for removal of anionic suspension particles. Changes in the electrokinetics of kaolin as a function of pH were investigated in the absence of flocculant. The results show that kaolin in water exhibits a negative surface charge at pH > 2.5. The negative hydrophilic surface sites of kaolin are responsible for the adsorption of cationic starch molecules. The experimental data of the adsorption of cationic starch (DS 0.51) follow a Langmuir isotherm with maximum adsorption capacities of 16.89 mg/g. For the adsorption of cationic starch, chemical reaction seems significant in the rate-controlling step and the pseudosecond-order chemical reaction kinetics provides the best correlation for the experimental data.

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“…[13] On the other hand, an increase in charge density causes an increase in electrostatic repulsive forces between the anionic polymer and negatively charged gibbsite particles at pH 11.5. Increase in repulsion apparently affects the flocculation of positively or negatively charged particles by enhancing the bridging forces leading to high settling rates or by making attachment of the particle to the polymer difficult, respectively.…”

Section: Particle Interactions: Rheologymentioning

confidence: 99%

Polyelectrolyte enhanced flocculation, particle interactions and dewaterability of fine gibbsite dispersions

Addai‐Mensah

Bal

Yeap

2008

Asia-Pacific J Chem Eng

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Enhanced dewaterability of colloidal hydrophilic mineral dispersions, via flocculation and gravity-assisted thickening, remains an important and technically challenging issue. To develop the right customized approach for flocculant selection to improve dewaterability, the influence of eight polyacrylamide (PAM) copolymers on flocculation, particle interactions and dewatering behaviour of fine, 9.5 wt% gibbsite dispersions at pH 7.5, 9.5 and 11.5 at 22• C is investigated. The results show that polymer charge type (anionic vs cationic) and charge density (5-45%) and molecular weight [(5-20) × 106 Da] had a striking, pH-dependent impact on dewaterability and dispersion rheology. Depending upon polymer type and dosage (50-200 g t −1 solid) and pulp pH, good to extremely fast settling rates (14-200 m h −1 ) were obtained upon orthokinetic flocculation. Sediment solid loadings recorded also showed polymer structure-and pH-dependency and were in the range 40-54 wt%. Upon shear of the pre-sedimented pulps, a 6-10 wt% solid improvement in consolidation resulted. The polymer with lower charge density (5% anionic) and lower molecular weight [(5-10) × 106 Da] was more effective in producing enhanced dewaterability of charged and neutral gibbsite particles than the polymers with higher molecular weights and/or charges. The settling rate, sediment consolidation and particle interactions (rheology) correlated positively, where faster settling flocs displayed higher sediment yield stresses which were accompanied by greater compaction behaviour. The findings underscore the need for greater understanding of the interplay between pulp interfacial chemistry and flocculant characteristics for optimum dewaterability.  2008

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Influence of polymer adsorption and conformation on flocculation and dewatering of kaolin suspension

Cited by 100 publications

References 16 publications

Guluronic acid content as a factor affecting turbidity removal potential of alginate

Guluronic acid content as a factor affecting turbidity removal potential of alginate

Flocculation properties and adsorption kinetics of cationic starches in kaolin suspensions

Polyelectrolyte enhanced flocculation, particle interactions and dewaterability of fine gibbsite dispersions

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