Flocculation Of Kaolin Suspension Research Articles

Magnetic coagulation and flocculation of kaolin suspension using Fe3O4 with plant polyphenol self-assembled flocculants

In this work, magnetic flocculant (Fe3O4@PP) was synthesized using plant polyphenol (PP) as a shaping ligand via in situ self-assembly. Characterization results revealed that Fe3O4@PP exhibited uniform particle size and excellent dispersibility with PP coating amount of 16.4 %. Experimental results suggested that Fe3O4@PP showed excellent turbidity removal efficiency in a wide pH range (3.0–10) and initial turbidity range (50–2000 NTU). Under the optimal conditions, Fe3O4@PP achieved 95.2 % of turbidity removal for simulated kaolin suspension and 96.9 % for actual wastewater. Fe3O4@PP exhibited excellent recycling and reusability properties, with high recycling efficiency of 93.3 % even after the fifth cycle. Microscopic observation revealed the formation process of magnetic flocs, involving particle aggregation, chain and cluster formation, and dense network aggregate formation. The structural characteristics and size of magnetic flocs were found to be significantly influenced by the combined effects of magnetic force, electric charge, van der Waals force, and functional groups on the surface of PP. The extended Deryaguin-Landau-Verwey-Overbeek models indicated that magnetic interactions were the primary mechanism for magnetic flocculation, accompanied by charge neutralization, adsorption bridging, sweeping, and net trapping.

Synthesis of chitosan-based grafting magnetic flocculants for flocculation of kaolin suspensions

A series of novel chitosan-based magnetic flocculants FS@CTS-P(AM-DMC) was prepared by molecular structure control. The characterization results showed that FS@CTS-P(AM-DMC) had a uniform size of about 21.46 nm, featuring a typical core-shell structure, and the average coating layer thickness of CTS-P(AM-DMC) was about 5.03 nm. FS@CTS-P(AM-DMC) exhibited excellent flocculation performance for kaolin suspension, achieved 92.54% turbidity removal efficiency under dosage of 150 mg/L, pH 7.0, even at high turbidity (2000 NTU) with a removal efficiency of 96.96%. The flocculation mechanism was revealed to be dominated by charge neutralization under acidic and neutral conditions, while adsorption and bridging effects play an important role in alkaline environments. The properties of magnetic aggregates during flocculation, breakage, and regeneration were studied at different pH levels and dosages. In the process of magnetophoretic, magnetic particles collide and adsorb with kaolin particles continuously due to magnetic and electrostatic attraction, transform into magnetic chain clusters, and then further form three-dimensional network magnetic aggregates that can capture free kaolin particles and other chain clusters. Particle image velocimetry confirmed the formation of eddy current of magnetic flocs and experienced three stages: acceleration, stabilization, and deceleration.

Preparation of carboxymethylated lignin-based multifunctional flocculant and its application for copper-containing wastewater

High efficiency lignin-grafted cationic polyacrylamide multifunctional flocculant (CL-CPAs) was synthesized via “grafting to” strategy using carboxymethylated lignin (CL), acrylamide (AM) and methylacryloyloxyethyltrimethyl ammonium chloride (DMC) as raw materials. The synthesized CL-CPAs showed high flocculation efficiency. Only a small dosage between 3.6 and 4.2 mg‧L−1 of CL-CPAs and a short flocculation time of 1–2 min were needed for sedimentation of kaolin suspension. Meanwhile, the carboxyl groups on the modified lignin endowed CL-CPAs with good copper ion capture function through complexation and electrostatic interaction. In addition, simultaneous flocculation of kaolin suspension and removal of copper ion was achieved for CL-CPAs attributing to the charge neutralization, bridging, and electrostatic complexation. The synthesized carboxymethylated lignin-based flocculants are cheap, environmentally friendly and technically feasible, showing broad prospects in wastewater treatment.

Sustainable cationic cellulose for highly efficient flocculation of Kaolin suspension

Sustainable cationic cellulose for highly efficient flocculation of Kaolin suspension

Implications of turbulence shear by non-cohesive sediments on the break-up of kaolin flocs

The present study investigated the role of non-cohesive fraction of sediments on the flocculation of kaolin suspension. The floc characterization was achieved through micro-scale investigations using an image capturing system followed by an image processing technique. Initially, the variations in the characteristics of flocs of kaolin with salinity and turbulence were examined, followed by characterization of flocs under the addition of sand fraction at different proportions (10%, 20%, 40% and 50%). The presence of sand imparts additional shear causing the break-up of macro-flocs of size >100μm. The variation of floc volume fraction of macro-flocs with turbulence follows a power law, which was used to quantify the additional turbulence shear created by different % of sand. The breakage coefficient of macro-flocs was determined from the experimental results and a relationship for it in terms of turbulence shear is proposed. The developed relationship was further applied to predict the breakage coefficient of macro-flocs due to the addition of sand. The sensitivity analysis conducted between predicted and observed breakage coefficient of macro-flocs due to the addition of sand yielded a correlation coefficient of 0.99. The study proves that the binary breakage model, which propose the break-up of a floc into two equal sized flocs, can be applied to predict breakage coefficient only at intermediate turbulence shear in the range of 20–40 s−1; further it fails to predict the breakage coefficient of macro-flocs in mixed sediment suspensions. The study highlights the role of sand in floc break-up and suggests that the developed model can very well predict the breakage coefficient of macro-flocs in estuaries with mixed sediments as well as at all ranges of turbulence shear encountered in estuaries.

Structural characterization and functional properties of novel exopolysaccharide from the extremely halotolerant Halomonas elongata S6

Production of extracellular polysaccharides by halophilic Archaea and Bacteria has been widely reported and the members of the genus Halomonas have been identified as the most potential producers. In the present work, a novel exopolysaccharide (EPS-S6) produced by the extremely halotolerant newly isolated Halomonas elongata strain S6, was characterized. According to the HPAE-PAD results, EPS-S6 was mainly composed of glucosamine, mannose, rhamnose and glucose (1:0.9:0.7:0.3). EPS-S6 was highly negatively charged and its molecular weight was about 270 kDa. Studies on its functional properties showed that EPS-S6 had several potential features. It has noticeable antioxidant activities on 2,2-diphenyl-1-picrylhydrazyl (DPPH•) inhibition and DNA protection, good ability to inhibit and to disrupt pathogenic biofilms, excellent flocculation of kaolin suspension and interesting emulsifying properties at acidic, neutral and basic pH. Therefore, EPS-S6 could have potential biotechnological concern in several fields such as in food, cosmetic and environmental industries.

Evaluation of the structural factors for the flocculation performance of a co-graft cationic starch-based flocculant

Three series of co-graft cationic starch (St)-based flocculants with distinct structural characteristics, namely, charge density (CD), graft-chain length (L), and graft-chain distribution (N), were successfully synthesized through graft copolymerization of [(2-methacryloyloxyethyl) trimethyl ammonium chloride] and acrylamide. These St-based flocculants with different molecular structures were used to flocculate various kaolin suspensions with different initial turbidities and a sodium humate (NaHA) aqueous solution. The experimental results indicated that CD contributed to flocculation evidently, whereas average L and its N were insignificant in experimentally measured ranges. On the basis of phenomenological theory, a second-order polynomial equation was used to further quantitatively analyze the effects of the three structural factors on the flocculation performance of these St-based flocculants, which were fully consistent with the experimental results. Besides, the optimal dose and its corresponding removal rate could be predicted exactly, and the flocculation mechanisms were discussed in detail according to the established models. With the combination of floc properties and zeta potentials, the flocculation mechanisms of these St-based flocculants for flocculation of kaolin suspensions and NaHA aqueous solution were mainly ascribed to charge patching and simple charge neutralization, respectively. These results improve the understanding of the structure–activity relationship of these graft St-based flocculants, which is of significant guidance for the utilization and design of novel flocculants.

Flocculation of kaolin from aqueous suspension using low dosages of acrylamide‐based cationic flocculants

ABSTRACTFlocculation of kaolin from aqueous streams has become very important in view of its wide range of applications. In this work, cationic flocculants based on copolymers of acrylamide (AM) and 3‐acrylamidopropyltrimethylammonium chloride (APTMAC) were synthesized with two different mole ratios of monomers, 80 mol % of AM (CP‐8020) and 40 mol % of AM (CP‐4060). The chemical structures of copolymers were confirmed by 1H and carbon‐13 nuclear magnetic resonance (13C NMR) spectroscopy. The molecular weight (MW) and zeta potential of the copolymers were determined. High MW was obtained for copolymer with high content of AM (CP‐8020) and high zeta potential was observed for copolymer with high content of APTMAC (CP‐4060). Flocculation of kaolin suspension was performed using both CP‐8020 and CP‐4060 and the flocculation was correlated to the zeta potential and MW of the copolymers. The optimum dosages of flocculants were determined. The mechanism of flocculation was discussed in terms of charge neutralization and bridging. The flocs of kaolin were characterized in terms of moisture content and size. To the best of our knowledge, this copolymer system was used for the first time for kaolin flocculation and found out to be efficient. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 47286.

Polyacrylamides revisited: flocculation of kaolin suspensions and mature fine tailings

A series of acrylamide‐based water‐soluble (co)polymers was synthesized and they were investigated as flocculants of model kaolin suspensions and mature fine tailings of oil sands. The effects of molar mass, charge density, and polymer concentration on flocculation efficiency were studied by monitoring the initial settling rate during sedimentation. Hydrolyzed polyacrylamide (HPAM) with high molar mass and intermediate acrylic acid contents (0.14–0.41 mol/mol (14–41 mol%)) performed better in flocculation tests on kaolin suspensions requiring lower dose for maximum initial settling rate than native polyacrylamide (PAM). Surface force measurements showed that at low polymer concentrations (1 ppm), the partially‐adsorbed polymer induced a bridging attraction between the mica surfaces. Increasing the polymer concentration to 10 and 50 ppm caused purely repulsive forces. The presence of anionic groups in HPAM led to stronger repulsion, which was also demonstrated by the higher viscosity and larger hydrodynamic radius of the charged polymer. The charge‐induced increase in the viscosity of polymer solutions was suppressed by the screening effect of salts in a buffer solution and reducing the viscosity is desirable in the injection of flocculants in the industrial process.

Polyacrylamide and poly(N,N-dimethylacrylamide) grafted cellulose nanocrystals as efficient flocculants for kaolin suspension

Natural polymer flocculants for wastewater treatment have received close attention in recent years. Here we used two flocculants, polyacrylamide and poly(N,N-dimethylacrylamide) grafted cellulose nanocrystals synthesized by a “macro-RAFT assisted” strategy, for the flocculation of kaolin suspension. The flocculation performance of these two flocculants, including flocculants dosage, settling time and floc size, was carefully studied and compared. Results suggested that poly(N,N-dimethylacrylamide) grafted cellulose nanocrstyals showed better flocculation performance than polyacrylamide grafted ones. Meanwhile, their flocculation behavior was also compared with other cellulose-based flocculants in literature and we suggested polymer modified cellulose nanocrstals as flocculants might have higher flocculation performance, but this needs further verification.

Flocculation Behavior of Starch Betainate

Starch betainate was applied in flocculation of kaolin suspension. The flocculation efficiency of starch betainate increased with the increase of both DS and molecular weight of starch betainate, which demonstrated that the flocculation was realized mainly by charge neutralization and bridging of the particles. When the dose of crosslinked starch betainate with DS of 0.33 was 3ppm, the removal ratio of turbidity could reach 90.5%, which was similar to the effect of traditional etherified cationic starch. The flocculation efficiency of starch betainate decreased with the increasing amount of salt in the kaolin suspension. Besides, pH of 5-7 was shown reasonable for starch betainate in the application.

Flocculation and antimicrobial properties of a cationized starch

In this study, a series of cationized starch-based flocculants (starch-3-chloro-2-hydroxypropyl triethyl ammonium chloride, St-CTA) containing various quaternary ammonium salt groups on the starch backbone were prepared using a simple etherification reaction. All of the prepared starch-based flocculants show effective performance for the flocculation of kaolin suspension, two bacterial (Escherichia coli and Staphylococcus aureus) suspensions, and two contaminant mixtures (kaolin and each bacterium) under most pH conditions. St-CTA with a high substitution degree of CTA demonstrates improved contaminant removal efficiency because of the strong cationic nature of the grafted quaternary ammonium salt groups and the charge naturalization flocculation effect. The antibacterial effects of St-CTA were also evaluated, considering that many quaternary ammonium salt compounds elicit bactericidal effects. Three-dimensional excitation–emission matrix spectra and direct cell morphological observation under scanning electron microscopy reveal that the starch-based flocculants exhibit better antibacterial effects on the Gram-negative bacterium E. coli than on the Gram-positive bacterium S. aureus. The thicker cell wall due to the presence of abundant peptidoglycan and teichoic acids of S. aureus than E. coli explains the uneasy breakage of S. aureus cell wall after being attacked by the cationized starch-based flocculants.

Optimization of coag-flocculation processes of a newly synthesized quaternized oil palm empty fruit bunch cellulose by response surface methodology toward drinking water treatment process application

An optimization of coagulation and flocculation of kaolin suspension by a newly synthesized quaternized oil palm empty fruit bunch cellulose denoted as a 9QC was investigated using the central composite design of the response surface methodology. The influences of coag-flocculant dosage, pH, and kaolin suspension on turbidity removal efficiency and sludge volume index responses were studied and assessed according to a 23 full factorial design. The developed quadratic models revealed that the overall optimum values to obtain the highest performance of the responses were 62.5 mg/L of coag-flocculant dosage, pH 7, and 1400 mg/L of kaolin concentration. The predicted optimum responses were found to be in close proximity to the observed responses. The coag-flocculating of river water using 9QC carried out at the optimum values showed encouraging results as compared to alum which is commonly used in drinking water treatment process.

Adsorption of organic–inorganic hybrid polymers on kaolin from aqueous solutions

Adsorption of two in-house synthesized organic-inorganic hybrid polymers, Al(OH)3-polyacrylamide (Al-PAM) and Fe(OH)3-polyacrylamide (Fe-PAM) on kaolin and corresponding flocculation of fluid fine kaolin suspensions were investigated. For comparison, a commercial anionic flocculant (partially hydrolyzed polyacrylamide or known as H-PAM) was also examined. The flocculation dynamics of fine kaolin suspensions were determined using an on-line focused beam reflectance measurement (FBRM) probe. As an example of applications, flocculation of a laboratory oil sands extraction tailings sample was studied. A quartz crystal microbalance with dissipation (QCM-D) was used to determine adsorption kinetics of the polymers on silica and alumina as representative of T- and O-basal planes of kaolin.Al-PAM, Fe-PAM and H-PAM were shown to be excellent flocculant of kaolin suspensions, with H-PAM being less effective and more sensitive to overdosing. The flocculation performance was greatly influenced by proper mixing. Strong flocculation of kaolin suspension by Al-PAM and Fe-PAM is attributed to their ability to adsorb on both basal planes of kaolin, in contrast to relatively weak flocculation of kaolin by H-PAM which adsorbs only on positively charged aluminum oxy-hydroxyl basal planes. The electrostatic attraction or repulsion is identified as a critical parameter in determining polymer adsorption and hence corresponding flocculation of kaolin suspensions.

Assessing the effect of flow fields on flocculation of kaolin suspension using microbial flocculant GA1

CFD simulations were employed to assess the effect of flow fields on flocculation of kaolin suspension using microbial flocculant GA1.

Influence of the concentration of water-soluble polyelectrolytes on the kinetics of flocculation of kaolin suspension and strength of formed floccules

The influence of the concentration and the charge of water-soluble (WS) polyelectrolytes on the kinetics aggregation of particles kaolin was investigated. It is shown that with the alternation of slow and fast mixing result to the formation of large and strong flocs. The rate of aggregation and size of particles formed flocs increases with the concentration of the reagent and the charge density of the polyelectrolyte. It was found that at low concentrations (10 -5 ~2,5·10 -3 %) polyelectrolytes (cationic - Zetag 89, Zetag 92, anionic - Magnafloc 155, Magnafloc 156 flocculants) flocculation of kaolin suspensions increases and the higher concentrations of flocculants (more on 2,5·10 -3 %) - suspension of kaolin is stabilized.

Structural characteristics and flocculation properties of amphoteric starch

Starch ampholytes (AmS) – cationic starch succinates – with the degree of substitution according to cationic groups of 0.29 or 0.36 and the degree of substitution according to anionic groups from 0.11 to 0.34 were prepared by succinylation of precationized starch. FT-IR spectra confirmed the incorporation of carboxylic groups into the backbone of cationic starch. Scanning electron microscopy was used for evaluation of the granular structure and surface morphology of modified polysaccharides. The decrease in accessibility of cationic quaternary ammonium groups in AmS was detected by means of polyelectrolyte titration. Colloidal dispersions of AmS were verified in the flocculation of kaolin suspensions and the sedimentation of wastewater sludge. Their flocculation performance was studied in connection with ξ-potential measurements and compared with that of cationic starch. The main advantage of AmS application is broadening of the flocculation window. The mechanism of flocculation by starch ampholytes has been proposed.

Characterization of a bioflocculant MBF-5 by Klebsiella pneumoniae and its application in Acanthamoeba cysts removal

This study evaluated the potential of an extracellular, novel biopolymeric flocculant produced by a strain of Klebsiella pneumoniae isolated from a sputum sample for removal of Acanthamoeba cysts, a potent pathogen prevalent in water, soil, air, and dust. The presence of cations did not enhance flocculating activity. The component of MBF-5 was mainly polysaccharide and protein with proportional of 96.8% and 2.1% respectively. Infrared spectrum analysis showed the presence of carboxyl and hydroxyl groups in MBF-5. MBF-5 is nontoxic and can be used for removal of amoebae cysts from water. Conditions for flocculation of kaolin suspension and Acanthamoeba cysts were optimized by response surface methodology (RSM) and determined to be 54.38 mg/L dosage, 26.14°C and pH 3.32 and 129.73 mg/L dosage, 30.75°C and pH 4.36, respectively. The results of this study indicates a possible use of the K. pneumoniae biopolymer as an alternative to typically used chemical flocculants for removal of amoebae cysts from water.

Study of Kaolin for Synthesis of Aluminum Chloride

Aluminum chloride enhanced polyacrylamide (AlCl3-PAM) hybrid polymer has been synthesized in this study. Aluminium chloride was synthesized with polyacrylamide via free radical solution polymerization to fabricate inorganic-organic hybrid polymer (AlCl3-PAM). A redox initiation system - (NH4)2S2O8 and NaHSO3 was used to initiate the polymerization at 50ºC in aqueous medium. Fourier Transform Infrared Spectrometer (FT-IR) was used to characterize aluminium chloride-polyacrylamide hybrid polymer by determining its functional groups exist in the hybrid polymer chain. Inorganic aluminium chloride salt was incorporated into the polyacrylamide to enhance the aggregation ability at kaolin particle interface. A physico-chemical method which is flocculation was used in this study to flocculate kaolin suspension. The effect of pH on the flocculation of kaolin suspension was studied between pH 5 to 7.5. The result showed the aluminium chloride-polyacrylamide (AlCl3-PAM) hybrid polymer was able to remove >99% of turbidity at pH 6.5 using 5 mg/L of dosage.

Characteristics and Flocculating Mechanism of a Bioflocculant M-1 Produced by <i>Enterobacter sp.</i> EP3

A bioflocculant M-1 produced by Enterobacter sp. EP3 was investigated with regard to its flocculanting characteristics and mechanism. 2.0 mg/l M-1 showed the maximum flocculating activity of 96% in 5.0g/l Kaolin suspension containing 8mM CaCl2 and that its flocculating activity was more than 80% in a wide pH range (4.0-12.0). Chemical analyses indicated that the biopolymer M-1 was mainly a polysaccharide, mainly consist of rhamnose and glucose with a molar ratio of 9:1. Infrared spectrophotometry showed the presence of carboxyl, hydroxyl and methoxyl groups in M-1 molecular. Flocculation of Kaolin suspension with M-1 acted as a model to explore the flocculating mechanism in which bridging mediated by Ca2+ was proposed as the primary action based on the experimental observations.