High Molecular Weight Cationic Polyacrylamide Research Articles

Flocculation of emulsified oil-in-water with dodecylbenzene sulfonate and polyacrylamide and floc separation by dissolved air flotation

This paper presents bench studies on the treatment of saline oil-in-water emulsions (synthetic and real produced water) by a novel flocculation technique combining sodium dodecylbenzene sulfonate and a high molecular weight cationic polyacrylamide, followed by floc separation by gravity and/or with microbubbles (dissolved air flotation - DAF). The effects of temperature, reagents concentration, medium pH, salinity (sodium chloride concentration), and water hardness on the separation efficiency were investigated. The best results for total oil and grease (TOG) removal were around 90% and residual TOG content between 7 and 13 mg L−1 in the treated water. These results were obtained with 20–40 mg L−1 of sodium dodecylbenzene sulfonate followed by 7 mg L−1 of polyacrylamide, at 25°C and at pH between 6 and 7. The microbubbles were generated by hydrodynamic cavitation in a needle valve after dissolving air in water at a saturation pressure of 4 bar with a 20% recycling ratio. The mechanisms involved were discussed in terms of interfacial phenomena occurring at the oil/water interface with the formation of polymer-surfactant complexes (PSCs). Notably, this instantaneous aggregation process occurs without the need for slow mixing, as in conventional flocculation. The flocculation of the emulsified oil droplets appears to involve, simultaneously, the formation of a polymer-surfactant complex, whereby the hydrophobic forces play an important role, and interactions between the oil droplets (coated with sodium dodecylbenzene sulfonate and the polyacrylamide). Here, large and light (cluster-like) hydrophobic flocs, with enmeshed/entrained oil (de-emulsified), immediately rise (as a phase separation) towards the water/air interface due to the low density, together with the small flocs rising with the microbubbles. Due to the high process efficiency and the high quality of the treated water, this flocculation technique appears to have a very good potential for oil-bearing wastewater treatment at a high rate, especially in refineries and offshore platforms of crude oil extraction.

Evaluation of the flocculation and dewatering performance of dual polymers for treating oil sands tailings

AbstractMature fine tailings produced in the processing of oil sands create serious water‐recovery problems; thus, it is important to characterize them and to improve the applicable dewatering technologies. Existing methods to dewater the tailings are found to be insufficient. Previous research has demonstrated that the addition of dual polymers is more efficient than using a single polymer to flocculate the fine tailings particles. Different from studies that took sophisticated procedures to assess the flocculation and dewatering efficiency of dual polymers, readily available and simple but effective experiments were conducted in this work. Evaluations were conducted with dual polymers comprised of low molecular weight poly(diallydimethylammonium chloride) (polyDADMAC) and high molecular weight cationic or anionic polyacrylamide (PAM). Turbidity and residual solids measurements for dewatered tailings treated with these polymers confirmed that the dual‐polymer approach yield superior performance compared to either polymer functioning alone. Zeta potential and microscopic observations indicated that the dosages of polyDADMAC and PAM that lead to near charge neutralization of the system result in maximal performance. We hypothesize that when dual polymers are added to the tailings, polyDADMAC acts to neutralize the charge and destabilize the fine particles, while high molecular weight PAM, either cationic or anionic, acts to aggregate the destabilized fines by the bridging mechanism. PolyDADMAC forms weak and tiny flocs when mixed with tailings particles. Cationic PAM transforms these small flocs into much larger ones, while anionic PAM connects them into aggregates. Therefore, synergism exists between polyDADMAC and PAM but this synergism is different, based on the charge of the PAM.

Improving the performance of shipboard rotary drum filters in the removal of cyanobacterial blooms by cationic polyacrylamide flocculation

Removing the extensively accumulated cyanobacteria from lake is a straightforward means to tackle cyanobacterial blooms. However, developing removal technology with both high removal efficiency and large treatment capacity remains a great challenge. We developed a shipboard rotary drum filter (RDF) with a 35-μm screen to remove cyanobacterial blooms at a flow rate of 900 m3/h in Lake Dianchi (Kunming, China). Nevertheless, the chlorophyll a (chl.a) concentration of the effluent was approximately 50 μg/L, which is higher than the control target of 20 μg/L. In this study, we aimed to improve the performance of RDF on cyanobacterial removal by the utilization of cationic polyacrylamide (CPAM). High molecular weight CPAM with a 30% cationic degree exhibited excellent flocculation effectiveness, with low flocculant doses, large sized flocs, short flocculation time, and high resistance to shear forces. Both the filtration rate and the cyanobacteria removal efficiency of the 35-μm screen were notably improved by 1 mg/L of CPAM. After being added before the water inlet pump and being agitated by the pump impellers, the CPAM could effectively flocculate cyanobacteria particles at a hydraulic retention time shorter than 20 s. Chl.a concentration and turbidity in the effluents of the shipboard RDF were reduced to lower than 20 μg/L and 12 NTU, respectively. Thus, a shipboard RDF coupled with CPAM flocculation is a promising approach to the removal of cyanobacterial blooms.

Cationic polyacrylamide induced nanoparticles assembly in a cellulose nanofiber network

Polyacrylamides of different molecular weight, charges and dosages allow to control the retention and distribution of nanoparticles (NPs) in composites, and optimise composite properties and functionality. Our aim is to evaluate the effect of high molecular weight (13 MDa) cationic polyacrylamide (CPAM) charge and dosage on SiO2 (74 nm) NP’s assembly in cellulose nanofibers composites.Engineered cellulose/SiO2 composites were investigated by SEM, SAXS and DLS. SEM images show the local area retention of NPs into the cellulose matrix. SAXS provides an average NPs distribution and inter-NPs distance over complete volume of composite. DLS gives the hydrodynamic radius of CPAM adsorbed onto SiO2 NPs in a suspension.SAXS analysis reveals a structure conformation made of spherical SiO2 NPs core of diameter 74 nm surrounded by a CPAM polyelectrolyte shell 2.5 nm thick. Surprisingly, CPAM induced assembly of SiO2 NPs with constant inter-nanoparticle distance, which is irrelevant of polymer charge density. However, NPs retention in the cellulose fibre network increases with CPAM dosage. The assembly mechanism is governed by the balance of electrostatic and steric forces following CPAM coverage onto NPs and the inter-nanoparticle CPAM bridging conformation. This maintains the constant inter-nanoparticle distance and the assembly of NPs in the cellulose network.

Degree of Flocculation and Interparticles Charges of Conditioned Municipal Activated Sludge using Mixed Polymers

ABSTRACTThe present research work focuses on a new conditioning and flocculation mechanism of municipal fresh activated sludge using a dual polymer system combining cationic and anionic polyelectrolytes. Various pairs of three different types of polyelectrolytes, low molecular weight cationic polyacrylamide (CPAM-10), high molecular weight cationic polyacrylamide (CPAM-80) and an anionic polyacrylamide (APAM-30), were selected, being used either individually or as cationic-anionic pairs. The results of use of the dual systems indicated that using mixed polymers for conditioning gave lower turbidity with better settling when compared to that of using individual pure polymers. The mixed polymers improved the sludge volume index (SVI) by 62%. The zeta potentials of the supernatant and solid-like samples of conditioned activated sludge were measured. Slight increases in zeta potential, from –12 to –9, of the mixed polymers for all supernatants were observed. On the other hand, zeta measurements showed that the sludge solid-like particles retained their negative charges despite the addition of the individual cationic polymers in the mixture. This phenomenon was explained in terms of the addition of the polyelectrolytes attracting, primarily, the carboxylic groups of the fine suspended sludge particles, while hydrogen bonds between the larger sludge particles resulted in attraction in accordance with the Van der Waals mechanism, and both attractions caused an immediate dewatering that led to flocculation, but with low compactness. As a result of retaining negative charges on the large sludge particles, dissolved metals were partially attracted, causing reduction in conductivities of the supernatants of 10% to 15% for all pairs. Rheological tests showed that the formed flocs had low shear stress resistances, ranging between 0.2 and 0.4 Pa, and weak flocs strength.

Effect of drag reducing agent on bubble formation in horizontal liquid cross-flow

In the present study, experiments were conducted in a rectangular mixing conduit of an effervescent atomizer to quantify the effect of addition of drag reducing agent on bubble formation from an orifice in horizontal cross-flow. Modified bubble formation behavior in horizontal liquid cross-flow after addition of drag reducing agent was investigated. Shadowgraph images of bubbles evolving at an orifice were taken using a high-speed camera; bubble size and velocity were measured. High molecular weight cationic polyacrylamide was used as a drag reducing agent. Increase in the size of bubble with increase in concentration was observed. Particle image velocimetry in the upstream flow with drag reducing agent provided velocity profile and turbulence characteristics showing of the role of mean flow on increasing the bubble size.

Unmodified Starch Granules for Strengthening Mineral-Filled Cellulosic Fiber Networks Promoted by Starch Pretreatment with a Cationic Polymer Flocculant in Combination with the Use of an Anionic Microparticulate Material

The efficient use of renewable resources (e.g., starch) is essential to the green economy. On the basis of commercially available microparticle retention and drainage systems, the process concept of trapping unmodified starch granules in mineral-filled cellulosic fiber networks for strength enhancement by incorporation of cationic polymer flocculant pretreated/bridged starch granules in combination with the use of an anionic microparticulate material was discussed and demonstrated. Specifically, a high molecular weight cationic polyacrylamide and a modified bentonite, which are commercially available in the market, were used as the polymer flocculant and the anionic microparticulate material, respectively. The paper strength loss upon the addition of precipitated calcium carbonate filler particles was significantly mitigated by employing such a concept, which may provide an alternative strategy for improving the strength properties of mineral-filled paper grades.

Effect of cationic polyelectrolytes on the performance of paper diagnostics for blood typing

We investigated the effect that two common types of cationic polyelectrolytes used in papermaking might have on the performance of paper diagnostics using blood typing as an example. The results were analyzed in terms of red blood cells (RBC) retention and antibody–antigen specificity. Two questions were addressed: (1) can poly(amido-amine) epichlorohydrin (PAE) typically used for paper wet strength affect the diagnostic performance? (2) can high molecular weight cationic polyacrylamide (CPAM) employed as retention aid enhance or affect the selectivity and sensitivity of paper diagnostics?A series of paper varying in type of fibers and drying process were constructed with PAE and tested for blood typing performance. Residual PAE has no significant effect on blood typing paper diagnostics under normal conditions. Positives are unaffected with PAE, while negatives lose slight sharpness as some RBCs are unselectively retained.CPAM, the most common retention aid, can also be used to retain cells and biomolecules on paper. Paper towel was treated with CPAM solutions varying in polymer concentration and charge density and tested for blood typing. We found that CPAM dried on paper can retain RBC. CPAM affects the negative tests by retaining non-specifically individual RBC on fibers. RBC retention increases non-linearly with the CPAM charge density and concentration. As expected, wet CPAM retain RBCs at concentrations higher than 0.1wt%.As paper diagnostics are becoming a reality, more realistic papers than the Whatman filter paper will be engineered. This study provides guidance on how best use the required polymeric wet-strength and retention agents.

Adsorption of cationic polyacrylamide at the cellulose–liquid interface: A neutron reflectometry study

The layer thickness and density of high molecular weight cationic polyacrylamide (CPAM) adsorbed at the cellulose–water interface was quantified by neutron reflectometry. The thickness of a full monolayer of CPAM of constant molecular weight (13MD) but different charge densities, adsorbed with or without NaCl (10−3M), was studied. Thin cellulose films (40±7Å) of roughness <10Å were produced by spin coating a cellulose acetate–acetone solution and regenerating by alkaline hydrolysis. Film smoothness was greatly improved by controlling the concentration of cellulose acetate (0.13wt%) and the hydrolysis time in sodium methoxide. The adsorption thickness of CPAM (40% charge 13MD) at the solid-D2O interface was 43±4Å on cellulose and 13±2Å on silicon, an order of magnitude smaller than the CPAM radius of gyration. At constant molecular weight, the thickness of the CPAM layer adsorbed on cellulose increases with polymer charge density (10±1Å at 5%). Addition of 10−3M NaCl decreased the thickness of CPAM layer already adsorbed on cellulose. However, the adsorption layer on cellulose of a CPAM solution equilibrated in 10−3M NaCl is much thicker (89±11Å for 40% CPAM). For high molecular weight CPAMs adsorbed from solution under constant conditions, the adsorption layer can be varied by 1 order of magnitude via control of the variables affecting electrostatic intra- and inter-polymer chain interactions.

Effect of cationic polyacrylamide on the processing and properties of nanocellulose films

The use of high molecular weight cationic polyacrylamide (CPAM) was investigated to accelerate the drainage of nanocellulose (Microfibrillated Cellulose) suspensions into films. The mechanism was quantified and optimized by measuring the gel point, the lowest solids concentration at which a continuous network is formed. The flocculation of MFC was analysed as a function of the polyelectrolyte dosage, charge density and molecular weight as well as process parameters (drainage time) and material properties. The adsorption isotherms of CPAMs on nanocellulose and their zeta potential curves were also analysed as a function of CPAM charge and dosage. Measured CPAM adsorption capacities for the 50% and 10% charged 13MDa CPAM onto MFC were 5mg/g and 8mg/g, respectively, corresponding to adsorption coverage on cellulose of 0.14mg/m2 and 0.22mg/m2. The floc strength and drainability of MFC suspensions were quantified with the gel point as a function of CPAM properties. For all combinations of polyelectrolyte molecular weight and charge density, the gel point of a nanocellulose suspension goes through a minimum with increasing polymer dosage. The minimum gel point was independent of the polyelectrolyte charge density at constant molecular weight. However, it reduced with decreasing CPAM molecular weight, at a constant addition rate. The drainage time of a nanocellulose suspension into a film is reduced by 2/3 by halving the gel point from 0.2 to 0.1kg/m3; this is due to the more flocculated suspension facilitating drainage between flocs. Nanocellulose films of increased porosity also result from reducing the gel point, signifying that the more open 3D structure of the flocculated cellulose suspension is retained upon drying the 2D film cellulose film structure.

Synthesis of High Molecular Weight Cationic Polyacrylamide

Cationic polyacrylamide is a derivative of polyacrylamide, a cationic polymer flocculant which has an excellent effect on sewage treatment. Our existing cationic polyacrylamide are mostly prepared by the Mannich reaction ,which has the shortcomings of more unreacted material, low cationic degree, poor stability, short validity, etc. Therefore, a cationic polyacrylamide has been prepared by aqueous solution.P(DAC-AM) was synthesized by aqueous copolymerization of acrylamide (AM) and DAC using complex initiated system consisted of (NH4)2S2O8,NaHSO3 and V-50. Mass percent of monomer, amount of initiator, content of cation monomer, pH, reaction time et al on the effect of intrinsic viscosity of polymer were discussed. The suitable conditions of synthesis were concluded. Mass concentration of monomers:35%, initiator amount 0.06 %,V-50 amount 0.005%,pH:5.5~6.5,urea concentration 0.1%,EDTA 0.02%,β-dimethylaminopropionitrile concentration 0.03%,reaction time 5~6h,the intrinsic viscosity of product is 13.95dL·g-1.

Lime mud CaCO3 for use as a filler material in papermaking: Impact of its preflocculation with cationic polyacrylamide

ABSTRACTCationic polyacrylamide with different molecular weights were used to preflocculate the lime mud (LM) before it was added to the paper stock for handsheet preparation. The particle sizes, ζ potential, and morphology of the unpreflocculated and resulting preflocculated LM were studied. We found that high‐molecular‐weight cationic polyacrylamide (H‐CPAM) led to larger LM flocs with a more positive ζ potential. The scanning electron microscopy images indicated that the morphological structure of the filler hardly changed during the preflocculation process. The effects of the preflocculation on the filler retention and paper properties were also investigated. The results show that the handsheets filled with preflocculated LM had better hydrophobicity and strength properties compared to handsheets filled with unpreflocculated LM, especially for H‐CPAM‐preflocculated LM. The paper formation was also improved, and the optical properties nearly remained the same. In addition, the LM preflocculated with H‐CPAM had the highest filler retention. At a filler loading of 30%, the filler retention of the H‐CPAM‐preflocculated LM was higher than 86; it was less than 82.5% in other cases. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 41640.

Preparation and properties of natural rubber latex-g-modified cationic polyacrylamide copolymers and its palm oil absorbent

The grafting of a modified cationic polyacrylamide (MCPAM) onto natural rubber (NR) latex to form a copolymer using potassium persulphate (K2S2O8) to generate active radicals on both the NR particle surface as well as on the MCPAM molecules was confirmed by ATR-FTIR. The copolymers showed a marked ability to absorbe palm oil up to 10 g g−1. First, the high molecular weight cationic polyacrylamide (CPAM) was reduced by using a combination of K2S2O8 and hydrogen peroxide (H2O2) through thermal degradation. The molecular weight of the CPAM as determined by viscosity was about 4000 g mol−1. It was then added to the NR latex in the presence of Terric16A16 at 60°C for 3 h and cast as a film on a glass plate to obtain the NR-g-PAM. In a water medium, the swelling ratio of the modified NR decreased as a function of the CPAM concentration. Also the thermal stability of the modified NR-g-PAM was higher than of the NR/PAM blend as confirmed by TGA. Finally, the ability of NR-g-MCPAM to absorb palm oil was investigated.

Direct measurement of alkaline phosphatase kinetics on bioactive paper

The reaction kinetics of alkaline phosphatase (ALP) adsorbed on paper was quantified by image analysis using a colorimetric technique under conditions of excess enzyme. A classical reaction kinetics approach integrated with image processing technique was used to analyse the coloured product formation from the enzyme substrate reaction against time. The order of reaction and rate constant of enzyme activities on paper surface were calculated. ALP was either physisorbed directly on paper or adsorbed on paper treated with a monolayer of a high molecular weight cationic polyacrylamide (CPAM), an anionic polyacrylic acid (PAA) or a high molecular weight polyethylene oxide (PEO). The reaction rate of enzymatic paper follows a first order reaction with respect to the concentration of enzyme–substrate complex. ALP immobilized on paper has a reaction rate 2 to 3 orders of magnitude lower than the free ALP enzyme in buffer solution. This might be due to a critical loss of enzyme flexibility upon adsorption. No increase in reaction rate was achieved by immobilizing ALP on paper treated with a high molecular weight cationic polyacrylamide (CPAM) or a highly charged anionic polyacrylic acid oligomer (PAA), which suggests the enzyme orientation was not significantly affected. However, the reaction rate for ALP on PEO treated paper was lower than that on CPAM or PAA treated papers. That is probably due to some PEO-enzyme interaction affecting the tertiary structure of the ALP enzyme.

An evaluation of solid waste capture from recirculating aquaculture systems using a geotextile bag system with a flocculant-aid

Two separate geotextile bag systems were evaluated as a means for capturing and dewatering bio-solids in the effluent stream from recirculating aquaculture systems (RAS). Each geotextile bag system used a high molecular weight cationic polyacrylamide (PAM) polymer as a flocculant-aid. The two systems were operated under freshwater and brackish water conditions. A complete analysis including water quality and agronomic sludge analysis was conducted at the North Carolina State University Fish Barn – a large-scale, freshwater RAS demonstration and growout facility. An evaluation of water quality and performance of a similar geotextile bag system was also conducted at the Marine Aquaculture Research Center near Marshallberg, North Carolina, USA, under brackish conditions (15 PPT). Results indicated that performance of each of the systems was similar with TSS, COD, TN, and TP removal greater than 95%, 65%, 50%, and 38%, respectively, for both systems. Analysis of the sludge collected in the freshwater system after 70 days in a dewatering, inactive mode, showed a moisture content (MC) of 86%, or 14% dry matter (DM), indicating the system was effective at passively dewatering the bio-solids. Nutrient removal efficiency may be system specific based on the geotextile bag size and influent flow rate.Geotextile bag systems using flocculant-aids are an efficient means for capturing and dewatering waste solids from RAS effluents. Optimized geotextile bag system designs depend on flow rate, feed rate, and solids dewatering time, and fate of the treated effluent. This evaluation will aid in predicting the expected performance and determining the appropriate size of a geotextile bag system. The type of treatment required downstream from the geotextile bag system used for solids capture in a RAS wastewater treatment system will depend on the intended fate of the treated effluent.

Preparations of Novel Flocculants and its Applications in the Paper-making Wastewater

Abstract Functional monomer [N-(2,4,4-trimethylpentan-2-yl)acrylamide] was synthesized and characterized by MS and NMR. A series of high molecular weight cationic polyacrylamides were prepared with N-(2,4,4-trimethylpentan-2-yl)acrylamide, acrylamide and methacryloxyethyltrimethyl ammonium chloride by copolymerization using complex initiation systems as catalysts in aqueous solution. Then they used as flocculants to treat the paper-making wastewater. The removal of the colour and the chemical oxygen demand (COD) in the treated waste water samples were determined. Results showed that flocculants could efficiently remove the color and the COD. The overall color and COD removal efficiencies reached as high as 80% and 85%, respectively.

Effect of Water Cationic Content on Flocculation, Flocs Resistance and Reflocculation Capacity of PCC Induced by Polyelectrolytes

In papermaking, mill water closure may result in a significant increase of inorganic salts in the white water. The effect of these contaminants on the performance of retention aids was evaluated, in this study, through flocculation of Precipitated Calcium Carbonate with three very high molecular weight cationic polyacrylamides of medium charge density and with different degrees of branching. Furthermore, flocs resistance and reflocculation capacity was also investigated when different types of shear forces were applied. Tests were carried out in distilled water and in industrial water containing a high concentration of cationic compounds. The flocculation, deflocculation, and reflocculation processes were monitored by evaluating particle size distribution using a light diffraction spectroscopy technique. Additionally to the effect of the cationic content of the medium, the influence of the flocculant dosage and degree of polymer branching were also studied. The effect of these parameters on the flocs stru...

Thermally Induced Intramolecular Surface Reactions on a Photoimageable Dielectric

The effect of bake temperature on the surface chemistry of a photoimageable dielectric is investigated. The dielectric contains mixtures of multifunctional bisphenol A based epoxies which are polymerized using cationic aryl sulfonium hexafluoroantimonate. Surface characterization via X-ray photoelectron spectroscopy and contact-angle titration reveals that baking the dielectric yields nucleophilic sulfur substitution of hydroxylated surface species to produce a diphenyl sulfoxide reaction product. Such reactivity provides a convenient means of altering the dielectric surface acidity. Surface acidity is shown to be well correlated to the adsorption of a high molecular weight cationic polyacrylamide deposited from solution during microelectronics fabrication.

Layer thickness for high molecular weight cationic polyacrylamides adsorbed on a surface with a preadsorbed poly-diallyldimethylammonium chloride

The adsorption of two cationic polymers to a silica surface was studied. First, a highly charged poly-diallyldimethylammonium chloride (poly-DADMAC), 6.0 meq g −1 with a molecular weight of 1.2 million, was adsorbed and thereafter a less charged cationic polyacrylamide (C-PAM), 0.42 or 0.97 meq g −1 with molecular weights of 7 or 9×10 6, respectively, was added. The adsorbed amounts and layer thicknesses were measured in situ by null ellipsometry. The thickness of the C-PAM layer was shown to be the same even when the amount of adsorbed C-PAM was reduced due to the preadsorbed poly-DADMAC. A larger total amount of polymer charges was adsorbed to the surface with preadsorbed poly-DADMAC than if only one of the polymers was adsorbed to form a complete layer.

Effect of colloidal silica and electrolyte on the structure of an adsorbed cationic polyelectrolyte layer

The interactions between an adsorbed high molecular weight cationic polyacrylamide (C-PAM) and anionic components have been investigated by ellipsometry. The anionic components used were non-aggregated and microaggregated anionic colloidal silica particles (ACS) and an anionic polyacrylamide (A-PAM). The C-PAM was adsorbed to a silica surface and the different anionic components were then added to the system. The effect of adding an electrolyte (NaCl) to some of these systems was also investigated. The thickness of the adsorbed layer, the adsorbed amount and some kinetic aspects of the adsorption and desorption processes were studied. A three-fold expansion was observed for the C-PAM layer when non-aggregated and microaggregated ACS was added. When large amounts of NaCl are added there is a great decrease in layer thickness for a system with non-aggregated ACS. A system with microaggregated ACS particles is less affected by an increase in the electrolyte concentration. More ACS is adsorbed to a C-PAM layer in the presence of NaCl than in its absence. When A-PAM is added to the C-PAM layer, the thickness and adsorbed amount is much less influenced than if ACS is added. A small increase in adsorption and in layer thickness is first observed and then a desorption process starts. Information about the conformation of the adsorbed cationic polyacrylamide has also been obtained. The ellipsometry measurements indicate that the structure of the adsorbed layer changes as the adsorption process proceeds. The polymers adsorbed first to the surface give a more dense layer than the polymers adsorbed last.