Cationic Polyacrylamide Flocculant Research Articles

High sedimentation efficiency and enhanced rare earth recovery in the impurity removal process of rare earth leachate by flocculation system

The main impurity ion in rare earth (RE) leachate are aluminum ions, which can be effectively removed by precipitation in the form of aluminum hydroxides. The flocculent colloidal precipitation formed by aluminum ions has a loose structure and high liquid content, resulting in lower sedimentation efficiency and higher RE loss. The addition of flocculants in the impurity removal process of RE leachate is expected to solve this problem. The cationic polyacrylamide flocculant (CPAM) was screened as the flocculant to accelerate the sedimentation of the impurity removal process as well as to effectively improve the recovery of RE. The effects of CPAM concentration, dosage, stirring rate and stirring time on the flocculation process was investigated. The optimal flocculation effect could be obtained under conditions of dosage of 0.5 mL, concentration of 0.1%, stirring speed of 700 r/min and stirring time of 2 min. Under this condition, RE recovery efficiency was 97%, Al removal efficiency was 96%, and the sedimentation time of the flocs was 20 min. Compared with absence of flocculants in this process, Al removal efficiency remained almost unchanged, while RE recovery efficiency and the sedimentation time of flocs increased by 4% and shortened by 40 min, respectively. The flocculation mechanism was discussed by the theory of two-dimensional fractal dimension, and it was found that the flocculation was mainly based on the combined effect of bridge flocculation and electrical neutralization.

A new solvent-free pathway for inducing quaternized lignin-derived high molecular weight polymer

In this work, kraft lignin (KL) was polymerized with vinylbenzyl chloride (VBC) in a molar ratio of 1.8:1 (KL: VBC) using sodium persulfate (Na2S2O8) as an initiator at pH 9–10 and temperature of 80–90 °C for 3 h to produce polymer kraft lignin-g-poly(4-vinylbenzyl chloride) KL-poly(VBC) 1. Then, the grafting reaction was conducted with two different imidazole-based monomers of different side-chain lengths (methyl and n-butyl), namely, 1-methylimidazole (MIM), 1-n-butylimidazole (BIM), which led to the formation of novel polymers, kraft lignin-g-poly(4-vinylbenzyl-1-methylimidazolium chloride) KL-poly(VBC-MIM) 2a and kraft lignin-g-poly(4-vinylbenzyl-1-n-butyl imidazolium chloride) KL-poly(VBC-BIM) 2b. The polymer 2a generated a larger molecular weight polymer with a higher charge density and solubility than polymer 2b since the n-butyl group would cause steric hindrance and weaker monomer to react with intermediate polymer 1 in the second stage. The contact angle analysis confirmed more hydrophilicity of polymer 2a, and elemental analysis confirmed the more successful polymerization of polymer 2a. Applying the generated polymers as flocculants for a kaolin suspension confirmed that polymer 2a had similar performance with commercial cationic polyacrylamide (CPAM) flocculants, even though polymer 2a had a smaller molecular weight. This polymerization offers a promising pathway for generating cationic polymers with excellent performance as a flocculant for suspensions.

Determination of polyacrylamide based flocculants in sewage sludge by off-line thermochemolysis-GC–MS analysis

This study aimed to develop an offline thermochemolysis method for the determination of cationic polyacrylamide (cPAA) flocculants in environmental samples, using trimethylanilline hydroxide as a thermochemolytic agent. This method induces degradation of cPAA into defined substituted glutarimide derivates, as specific pyrolysis products. These pyrolysis products appeared in typical pattern of homologues allowing not only an unambiguous identification of the polymer but, more important, also a reliable pyrolysis based quantification in environmental concentration levels. Pyrolysis analysis were carried out on pure cPAA and spiked samples for method optimization, as well as on four sewage sludge samples from Germany as proof of applicability. All four specific degradation products were identified in three out of four sewage sludge samples indicating that the developed TMAH-thermochemolysis method is suitable for PAA detection in complex matrices and on environmentally relevant concentration levels. Nevertheless, experiments on sewage sludge samples revealed cPAA contamination in a concentration range between 29 and 76 μg/g. However, it has to be noted that the presence of all four specific degradation products has to be validated in order to have a doubtless cPAA confirmation in environmental samples.

Preparation and properties of cationic polyacrylamide flocculant for drilling fluid based on modified nano SiO2

Preparation and properties of cationic polyacrylamide flocculant for drilling fluid based on modified nano SiO2

Digestate mechanical separation in industrial conditions: Efficiency profiles and fertilising potential.

The growing number of biogas plants has resulted in problems with the digestate management. In the studies carried out in industrial conditions in the biogas plant fed with sugar beet pulp, the influence of the decanter centrifuge operating parameters such as the retention time and differential speed on the effectiveness of digestate mechanical separation was evaluated. During the studies, the impact of the addition of cationic polyacrylamide flocculants with different charge density on the liquid and solid fraction composition was also determined. It was shown that the dry matter and organic matter concentrations in the solid fraction were about 88.80 g/kg FM and 66.20% DM, respectively and in the liquid fraction 25.50 g/kg FM and 77.00% DM after the centrifugation of the digestate without flocculant at an optimal retention time of 225s and differential speed of 4rpm. The removal efficiency of dry matter and organic matter was 32.00% and 39.39%. The best separation results were obtained centrifuging the digestate with addition of 20 g/kg DM flocculant with a charge density of 80%. The flocculant addition increased the removal efficiency of dry matter and organic matter in comparison to centrifugation without flocculant by 49.60% and 46.86%, respectively. After centrifugation and flocculation, about 60.83% of nitrogen, 74.55% of potassium and 33.23% of phosphorus remained in the liquid fraction. The liquid fraction contained lower concentrations of nickel, lead, cadmium and chromium in comparison to solid fraction.

Research on the Settlement Performance of Flocculants on the Sediment of Mine River

In view of adding different flocculant to the mine river sediment, the influence of different flocculants on the sedimentation performance of the mine river sediment was investigated. The experimental results show that the selected flocculant, cationic polyacrylamide (CPAM), has an evident effect on the flocculation and settlement of the mine river sediment. The final flocculation effect was enhanced with faster settling speed. The flocculation effect was optimized when 10 mL CPAM flocculant (0.2wt%) was added, followed by 3 minutes of stirring. The dewatering effect of the flocculated sediment can be enhanced with decreased solid content of the sediment.

Application of Polyacrylamide Flocculant for Stabilization of Anaerobic Digestion under Conditions of Excessive Accumulation of Volatile Fatty Acids

Excessive accumulation of volatile fatty acids (VFA) is one of the major factors destabilizing methanogenic digestion of organic wastes in anaerobic bioreactors. Existing methods of stabilization of this process are mostly expensive and labor-intensive, often requiring removal of a considerable portion of acidified biomass from the bioreactor. We propose a method for methanogenesis restoration in such soured reactors by the addition of a cationic polyacrylamide flocculant (PAM) at 20 mg/g total solids. After flocculant addition, mixing should be minimized to prolong the existence of the floccules formed in the presence of the flocculant. While partial microbial degradation of the polyacrylamide flocculant was observed during the thermophilic anaerobic process, complete PAM mineralization did not occur. Significant inhibition of anaerobic processes, primarily in the activity of syntrophic propionate-oxidizing bacteria, was observed at PAM concentrations above 40 mg/g total solids.

Evaluation of newly developed reverse demulsifiers and cationic polyacrylamide flocculants for efficient treatment of oily produced water

For treating oily produced water (OPW) originating from the steam-assisted gravity drainage (SAGD) process, we prepared three water-soluble and cationic reverse demulsifiers - poly aluminium chloride and quaternary ammonium salt (PAC-QAS), polyamine (PA), and polyamine and poly aluminium chloride (PA-PAC). Their effectiveness in destabilizing the emulsion and removing oil and suspended solids from OPW and the synergistic effect with cationic polyacrylamide flocculants (CPAMs) were examined through bench-scale and field tests. The effects of chemical properties, injection dosage, and influent water quality on separation efficiency were discussed in detail. Results from microscopic observations and bottle tests reveal that polyamine-type reverse demulsifier could effectively separate oil from OPW. Its surface-active components enabled to induce morphological changes of the emulsified oils in the aqueous phase by absorbing at the oil-water interface, replacing the natural surfactants, and weakening the interfacial film strength, which promoted the collision and coalescence of small oil droplets. The subsequent bridging and sweeping effects driven by flocculant further strengthened the treatment performance. The optimal combination of PA and CPAM-2 could remove up to 90 % oil and 85 % suspended solids from OPW. Compared to flocculant, the insufficient dosage of reverse demulsifier resulted in worse separation, signifying that the demulsification played a more significant role. The correlation of treatment performance obtained from bench-scale and field tests showed that lower chemical dosages were required in the practical application, indicating the economic applicability and operability for oily wastewater treatment.

Preparation of octopus-like lignin-grafted cationic polyacrylamide flocculant and its application for water flocculation

High efficiency lignin-grafted cationic polyacrylamide (L-CPA) flocculant was synthesized via “grafting to” method using acrylamide (AM), methylacryloyloxyethyltrimethyl ammonium chloride (DMC) and enzymatic hydrolysis lignin (EHL) as raw materials. The linear pre-polymer of cationic polyacrylamide (CPA) terminated with chlorine was first synthesized and then grafted onto EHL via reactions of chlorine with phenolic hydroxyl groups in lignin molecules. The synthesized L-CPA could self-assemble into octopus-like nanospheres with CPA segments dissolved in water and hydrophobic lignin skeletons concentrated in the core, which endowed the L-CPA with excellent flocculation efficiency for kaolin suspension under faintly acid, neutral or alkalescent conditions (pH = 5–9). Only a small dosage between 4.0–4.5 mg/L of L-CPA was needed for flocculation of the kaolin suspension. The charge neutralization and bridging effect was proposed for the flocculation mechanism of the lignin-grafted cationic polyacrylamide. The octopus-like L-CPA was cheap, environmentally friendly and technically feasible, showing a great prospect in wastewater treatment.

Fabricating a hydrophobic modified flocculant through UVC irradiation initiation for metalworking wastewater treatment

In this work, a hydrophobically modified cationic polyacrylamide (CPAC) flocculant was polymerized by short-wave ultraviolet (UVC) initiation with acrylamide, acryloyloxyethyl trimethylammonium chloride, and coconut diethanolamide (CDEA) as monomers to enhance the destabilization and separation efficiency of emulsified oil and particles/colloids from metalworking fluids wastewater (MWFs). The parameters for flocculant polymerization were optimized, and the features of UVC-initiated polymerization were studied. Moreover, the structural and morphological characteristics of the polymers were explored, and the flocculation performance of CPAC in MWFs treatment was evaluated. The characterization results suggested that flocculants with a multilayer, loose-sheet morphology and intrinsic viscosity of 11.32dLg−1 could be successfully polymerized by UVC-initiated polymerization. Compared with traditional UV, UVC irradiation initiation promoted the copolymerization of flocculants with a high monomer conversion rate and intrinsic viscosity. We observed the low dosage requirement and acid resistance of the flocculant synthesized by UVC-initiated polymerization, which produced the lowest residual turbidity, highest chemical oxygen demand, and most efficient oil removal during MWFs treatment among the samples studied. Besides charge neutralization and bridging effects, the adsorption effect between hydrophobic CDEA blocks and nonpolar oil/colloids facilitated the formation of microflocs and improved the flocculation efficiency of the flocculant.

Validation of a cationic polyacrylamide flocculant for the harvesting fresh and seawater microalgal biomass

Abstract A simple, efficient, and fast settling flocculation technique to harvest microalgal biomass was demonstrated using a proprietary cationic polyacrylamide flocculant for a freshwater (Chlorella vulgaris) and a marine (Phaeodactylum tricornutum) microalgal culture at their mid-stationary growth phase. The optimal flocculant doses were 18.9 and 13.7 mg/g of dry algal biomass for C. vulgaris and P. tricornutum, respectively (equivalent to 7 g per m3 of algal culture for both species). The obtained optimal dose was well corroborated with changes in cell surface charge, and culture solution optical density and turbidity. At the optimal dose, charge neutralization of 64 and 86% was observed for C. vulgaris and P. tricornutum algal cells, respectively. Algae recovery was independent of the culture solution pH in the range of pH 6 to 9. Algal biomass recovery was achieved of 100 and 90% for C vulgaris and P. tricornutum respectively, and over 98% medium recovery was achievable by simple decanting.

Enhanced treatment of flush-dairy manure in anaerobic sequencing batch reactors using a cationic polymer

Anaerobic sequencing batch reactors (ASBR) are preferred for treating dilute wastewaters but the retention of adequate active biomass, in successive-cycles, is always a challenge. This research investigated the efficacy of using a cationic polyacrylamide (PAM) flocculant for enhanced sludge retention in an ASBR treating flushed dairy manure, operated under psychrophilic conditions. Three PAM doses (10, 25, and 50 mg [PAM] l−1) were tested in duplicate reactors. At 6 d hydraulic retention time (HRT) and dosing of the feed-manure, steady state specific biogas yield for the 50 mg [PAM] l−1 treatment was 491 ± 7 ml g−1 [TCOD] (56% greater than control). At 4 d HRT the 50 mg [PAM] l−1 dose resulted in 465 ± 8 ml g−1 [TCOD] (20% higher than the control) at steady state conditions. The ratio of total volatile fatty acid to alkalinity was 0.29 ± 0.08 during the 6 d HRT and 0.14 ± 0.02 during the 4 d HRT, which were both below the trigger point for digester souring. This study shows that the use of PAM for high sludge retention in ASBR is a viable approach for, not only enhancing biogas yield, but also for improved and high-rate treatment of flushed dairy manure under psychrophilic conditions.

Up-scaling of tannin-based coagulants for wastewater treatment: performance in a water treatment plant.

Tannin extracts from the bark of Acacia mearnsii and wood of Schinopsis balansae, commonly known as Quebracho, were employed. These were modified at laboratory sale via the Mannich aminomethylation with formaldehyde and dimethylamine hydrochloride. Some reaction conditions were varied, namely the formaldehyde dosage and reaction time, while keeping the Mannich solution activation time constant, and their influence on the shear viscosity of the created bio-coagulants was evaluated. The effect of the final pH of the products on their shear viscosity was also analyzed. Up-scaling of the Mannich reaction for tannin from South Africa was performed and the procedure developed at 1-L scale was reproducible in upscaled conditions. One example of a modified South Africa tannin and the modified Quebracho tannin was subsequently selected for the treatment of an industrial wastewater and tested for color and turbidity reduction in jar tests. The effluent treatment was carried out in a single and dual system with cationic synthetic flocculation agents of different charge degree. Good turbidity and decoloration results (93 and 89% reduction, respectively) were obtained with the simultaneous introduction of a cationic, 40% charged polyacrylamide, with minimal dosage (5ppm) of the latter additive. The tannin-based coagulant from Acacia mearnsii was successfully applied in dual system with cationic polyacrylamide flocculant for industrial wastewater treatment at pilot plant scale. It was shown to satisfactorily treat the water and generate less sludge.

Removal of emulsified oil from water using hydrophobic modified cationic polyacrylamide flocculants synthesized from low-pressure UV initiation

Abstract This study investigated a hydrophobic-modified cationic polyacrylamide (PAMP) synthesized through low-pressure UV-initiated copolymerization by using monomers of acrylamide (AM), diallyl dimethyl ammonium chloride aqueous solution (DADMAC), and dodecyl polyglucoside (DPL) to effectively remove emulsified oil from water. Various analytical methods were used to characterize the microstructure of PAMP, including Fourier transform infrared spectroscopy (FTIR), unclear magnetic resonance (13C NMR and 1H NMR), and thermal gravimetric and differential analysis (TG-DTA). Results confirmed that cationic and hydrophobic monomers were successfully grafted onto the molecular chain of the PAMP. Furthermore, the flocculation efficiency of PAMP was evaluated and optimized in emulsified oily wastewater treatment. PAMP exhibited satisfactory emulsified oil removal efficiency, and optimal oil and turbidity removal efficiencies of 94.5–98.6% and 95.1–98.9% were achieved with DADMAC content of 40%, DPL content of 30%, dosage of 8.5–9 mg/L, pH of 6–8, rapid stirring speed of 400 rpm, rapid stirring time of 35 min, slow stirring time of 15 min, and standing time of 25 min. Moreover, charge neutralization and hydrophobic association interaction dominate the emulsion breaking in oily wastewater flocculation.

Fabricating an enhanced sterilization chitosan-based flocculants: Synthesis, characterization, evaluation of sterilization and flocculation

Modified natural polymer flocculants has been the focus of research in environmental engineering field. Natural large molecular compound, chitosan (CTS) with many functional amino and hydroxyl groups can be easily modified to enhance its original functions. This work presents an environmentally friendly chitosan-based cationic polyacrylamide flocculants (CTS-g-PAMA) with enhanced function of sterilization and flocculation. CTS-g-PAMA was synthesized through Ultraviolet (UV)-initiated copolymerization. Structure characterization of FTIR, 1H NMR, XRD and UV spectrum confirmed the successful grafting of AM and MAPTAC. Scanning electron microscopy (SEM) analysis results showed that CTS-g-PAMA exhibited a porous structure with a prodigious surface area. CTS-g-PAMA was then applied to treat a series of simulated waste water containing kaolin or Escherichia coli. Flocculation tests indicated that CTS-g-PAMA not only showed excellent flocculation effect but also showed high sterilization capability. A series of ONP concentration measurement tests through UV spectra analysis and 3D EEM analysis of suspension before and after flocculation were conducted to study sterilization mechanism, and results revealed the sterilization effect of CTS-g-PAMA was essentially bactericidal, not just antibacterial.

UV-initiated template copolymerization of AM and MAPTAC: Microblock structure, copolymerization mechanism, and flocculation performance

Flocculation as the core technology of sludge pretreatment can improve the dewatering performance of sludge that enables to reduce the cost of sludge transportation and the subsequent disposal costs. Therefore, synthesis of high-efficiency and economic flocculant is remarkably desired in this field. This study presents a cationic polyacrylamide (CPAM) flocculant with microblock structure synthesized through ultraviolet (UV)-initiated template copolymerization by using acrylamide (AM) and methacrylamido propyl trimethyl ammonium chloride (MAPTAC) as monomers, sodium polyacrylate (PAAS) as template, and 2,2'-azobis [2-(2-imidazolin-2-yl) propane] dihydrochloride (VA-044) as photoinitiator. The microblock structure of the CPAM was observed through nuclear magnetic resonance (1H NMR and 13C NMR) spectroscopy, Fourier transform infrared (FTIR) spectroscopy, and scanning electron microscopy (SEM) analyses. Furthermore, thermogravimetric/differential scanning calorimetry (TG/DSC) analysis was used to evaluate its thermal decomposition property. The copolymerization mechanism was investigated through the determination of the binding constant MK and study on polymerization kinetics. Results showed that the copolymerization was conducted in accordance with the I (ZIP) template polymerization mechanism, and revealed the coexistence of bimolecular termination free-radical reaction and mono-radical termination in the polymerization process. Results of sludge dewatering tests indicated the superior flocculation performance of microblock flocculant than random distributed CPAM. The residual turbidity, filter cake moisture content, and specific resistance to filtration reached 9.37 NTU, 68.01%, and 6.24 (1012 m kg−1), respectively, at 40 mg L−1 of template poly(AM-MAPTAC) and pH 6.0. Furthermore, all flocculant except commercial CPAM showed a wide scope of pH application.

Influence of fibers on the shear strength and dewatering performance of geotextile tubes

Geotextile tubes have been widely used for the dewatering of high water content fine sediments. Fine sediments include lake sediments, organic soils and coal combustion products, which generally have low shear strength. Several researchers have emphasized the effect of the retained sediment (filter cake) properties on dewatering performance and stability of the geotextile tubes. Maintaining retained sediment properties, in particular permeability and shear strength, allows for faster dewatering time, better retention of sediments and improved stability of the geotextile tubes during multiple filling stages and during the tube stacking process. Several studies have shown that the use of synthetic fibers can increase the shear strength of sand, silt and clays. However, the use of fibers to improve the strength of retained sediments in geotextile tubes has not been explored. In this study, three synthetic fibers varying in length and diameter were used to evaluate the effect of fibers on the dewatering performance and shear strength of the fine sediments. A cationic polyacrylamide flocculant was used as an optimum conditioner for the selected sediment. The fibers were mixed with the flocculant conditioned slurry at 0.25, 0.5, 1 and 2% fiber concentration by mass of the dry solids. The effect of fibers on the undrained shear strength of the dewatered sediments was evaluated using a lab vane test, fall cone test and undrained unconsolidated triaxial test. Jar tests and pressure filtration tests were also conducted to evaluate the effect of fiber on the required flocculant dosage and on the dewatering performance. Based on the results of this study, 0.5% of F1 fiber type was found to be the optimum fiber concentration, yielding an approximately 100% increase in undrained shear strength. It was also found that the diameter and length of the fibers play a significant role in altering the undrained shear strength of the tested sediments. The relatively short (6 mm) and thick (38 μm) fiber did not yield an increase in shear strength for all the tested fiber concentrations, whereas thin fibers (9 μm) of similar length increased the shear strength by 100%. Furthermore, it was found that the use of fibers at any concentration decreases the required optimum doses of flocculant by about 15%, and increases the dewatering rate of the effluents by about 50%.

Study on the Settlement Experiment of Iron Tailings

The settlement experiment of representative iron tailings was studied, the iron tailings were from a processing plant of Wuhan Iron and Steel Group. There were four experiments were conducted which includes nature sedimentation test, coagulation sedimentation test of inorganic salt coagulant, flocculation sedimentation test of polymer flocculant and the mix coagulation sedimentation test. The test results showed that the size of sample is relatively fine and unevenly distributed, what's more, the velocity of natural sediment is very slow, and the effect that concentration has on the settling velocity of particles is obvious. The inorganic salt coagulant could reduce turbidity of supernatant, but it play a limited role in improving settling rate, it was found that FeCl3 is the best coagulation agent, PAM is effective flocculant for the sample, and the coagulation effect of cationic flocculation (molecular weight is six million) is better than that of anionic and nonionic. The settling velocity of particles was improved and the solid content of supernatant was reduced in the mix coagulation sedimentation test, but the improvement of settling velocity was not obvious. The author suggests that the single cationic polyacrylamide flocculant which was used for pretreatment on the tailings could meet the requirement of the tailings settlement.

Synthesis Star-Shaped Cationic Polyacrylamide- Dimethyl- Diallyl- Ammonium- Chloride by "Core-First" Method

A star-shaped cationic polyacrylamide(star-P(AM-DMDAAC)) was synthesized by free radical copolymerization of monomer of acrylamide(AM) and dimethyl diallyl ammonium chloride (DMDAAC) using the redox system of pentaerythritol(PETL) and (NH4)2S2O8 as initiator. And the factor influence the polymer molecular weight were detailed studied. The results indicate that the effects of polymerization temperature, the dosage of initiator, molar ratio of AM to DMDAAC have a greater influence on the viscosity-average molecular weight of the copolymer. and adding urea and ethylenediamine tetraacetic acid(EDTA) for additive and adding ammonia for adjustment the acidity of catalyst system can also increase the polymer molecular weight. The sludge dewatering performance of self-made star-P(AM-DMDAAC) is better than the commercial linear type cationic polyacrylamide flocculants in the market. The structures of the resulting products were characterized by nuclear magnetic resonance(1H-NMR), the PETL as "core" of the star polymer, the AM and DMDAAC as "arms" of the star polymer. And the synthesis mechanism was proposed in this paper.

Preparation of Cationic Polyacrylamide Flocculant and its Application in the Treatment of Coal Slurry Wastewater

A cationic polyacrylamide flocculant (CPAM) for the coal slurry wastewater, was firstly synthesized using acrylamide and cationic monomer ethylene methyl propenoyl trimethylammonium chloride (DMC). The structure of the synthesized CPAM was characterized by means of FT-IR measurement, and the effects of various factors on flocculation performance were studied. The optimum flocculation can be achieved according to the dosage of flocculant between 2 and 5 mg/L, pH value of 6, temperature of 40°C, and the dosage of DMC in CPAM of 17.5%.