Anionic Polyacrylamide Polymer Research Articles

Third-Generation Anticancer Photodynamic Therapy Systems Based on Star-like Anionic Polyacrylamide Polymer, Gold Nanoparticles, and Temoporfin Photosensitizer.

Photodynamic therapy (PDT) is a non-invasive anticancer treatment that uses special photosensitizer molecules (PS) to generate singlet oxygen and other reactive oxygen species (ROS) in a tissue under excitation with red or infrared light. Though the method has been known for decades, it has become more popular recently with the development of new efficient organic dyes and LED light sources. Here we introduce a ternary nanocomposite: water-soluble star-like polymer/gold nanoparticles (AuNP)/temoporfin PS, which can be considered as a third-generation PDT system. AuNPs were synthesized in situ inside the polymer molecules, and the latter were then loaded with PS molecules in an aqueous solution. The applied method of synthesis allows precise control of the size and architecture of polymer nanoparticles as well as the concentration of the components. Dynamic light scattering confirmed the formation of isolated particles (120 nm diameter) with AuNPs and PS molecules incorporated inside the polymer shell. Absorption and photoluminescence spectroscopies revealed optimal concentrations of the components that can simultaneously reduce the side effects of dark toxicity and enhance singlet oxygen generation to increase cancer cell mortality. Here, we report on the optical properties of the system and detailed mechanisms of the observed enhancement of the phototherapeutic effect. Combinations of organic dyes with gold nanoparticles allow significant enhancement of the effect of ROS generation due to surface plasmonic resonance in the latter, while the application of a biocompatible star-like polymer vehicle with a dextran core and anionic polyacrylamide arms allows better local integration of the components and targeted delivery of the PS molecules to cancer cells. In this study, we demonstrate, as proof of concept, a successful application of the developed PDT system for in vitro treatment of triple-negative breast cancer cells under irradiation with a low-power LED lamp (660 nm). We consider the developed nanocomposite to be a promising PDT system for application to other types of cancer.

Experimental investigations on the physico-mechanical and microstructural properties of loess reinforced with anionic polyacrylamide

The typical characteristics of loess, such as macropores, weak cementation, and strong collapsibility, can adversely affect the stability of building foundations, transportation infrastructure, and other geotechnical systems. To address this problem, a water-soluble anionic polyacrylamide (APAM) was used to improve the characteristics of loess. A series of multi-scale geotechnical engineering tests, such as sedimentation column, zeta potential, Atterberg limits, standard compaction, permeability, triaxial compression strength, scanning electron microscope (SEM), nuclear magnetic resonance (NMR), and X-ray diffraction (XRD) tests were conducted on the loess samples. The results showed that the APAM polymer could flocculate fine loess particles into stable agglomerates via a series of physical actions, including charge neutralization, adsorption and bridging, and hydrophobic interactions. The contact form among the loess particles changed from loose point contact to strong mosaic contact with the addition of the APAM polymer, the surface porosity, fractal dimension, and interplanar spacing of the treatment material decreased significantly. The considerable improvement of loess microstructure affected its macroscopic physical and mechanical properties. The optimum moisture content and permeability coefficient of the treated loess decreased with the increases of the APAM content, whereas the plasticity index and maximum dry density increased. Additionally, the failure strength of the loess samples first increased then decreased as the APAM content increased, which showed the maximum value at an addition amount of 0.30% content, beyond which its strength value decreased. The test results demonstrated that the APAM polymer treatment could provide significant improvement in the macroscopic physico-mechanical and microstructural properties of loess. This study will serve as a crucial resource for loess foundation stabilization using the environmentally friendly and cost-effective polymer.

Effect of Anionic Polyacrylamide Polymer on Frost Heave Mitigation and Its Implication for Frost-Susceptible Soil.

Seasonally frozen ground regions occupy approximately 55% of the exposed land surface in the Northern Hemisphere, and frost heave is the common global problem in seasonally frozen soil areas. Frost heave induces uneven deformation of ground and damages railways, road paving, and buildings. How to mitigate frost heave is the most important technical issue in this field that has provoked great interest. Here, using freezing experiments, we investigate the effect of anionic polyacrylamide (APAM) polymer on frost susceptible soil. The results demonstrate a so-far undocumented inhibition of frost heave by APAM in freezing soil, namely APAM (tested at concentrations from 0.0 wt% to 0.60 wt%) slows down the frost heave by a factor of up to 2.1 (since 0.60 wt% APAM can decrease frost heave from 8.56 mm to 4.14 mm in comparison to the control experiment). Moreover, it can be observed that the maximum water content near the frozen fringe decreased from 53.4% to 31.4% as the APAM content increased from 0.0 wt% to 0.60 wt%, implying a mitigated ice lens growth. Hydrogen bonding between APAM and soil particles triggers an adsorption mechanism that accumulates soil particles, and thus can potentially inhibit the separation and growth of the ice lens. Moreover, the residue of APAM due to hydrogen bonding-induced adsorption in the pores of granular media may narrow seepage channels (capillary barriers) and provide an unfavourable condition for water migration. The use of APAM can also increase the viscosity of the solution, which causes a greater water migration resistance. This research provides new insights into APAM-influenced frost heave (introducing APAM into the soil can induce bridging adsorption between APAM polymer segments and a particle surface), can enable engineers and researchers to utilise chemical improvement design and to consider suitable actions (e.g., by injecting APAM solution into a frost susceptible soil or using APAM-modified soil to replace the frost susceptible soil) to prevent frost heave from having a negative impact on traffic roads and buildings in cold regions.

Performance of eco-friendly polymers for soil stabilization and their resistance to freeze–thaw action

Soil improvement methods using environmentally friendly additives have gained popularity with increased environmental awareness. In the future, environmentally friendly polymers can be preferred in the stabilization of many geotechnical applications like the base of roads, landfills, and sub-base of foundations. This means the mechanical properties of these eco-friendly polymers should be investigated in detail. For this purpose, changes in the mechanical properties of specimens treated with different polymer types under freeze–thaw action were investigated. Three types of polymers which are xanthan gum, guar gum, and anionic polyacrylamide polymer were used to improve the strength properties of kaolin clay. The specimens were prepared in 3 different anionic polymer contents and 4 different biopolymer content. After 7, 14, and 28-day curing periods specimens were subjected to 5 and 10 cycles of freezing–thawing to observe freeze–thaw action by conducting unconfined compression tests and the control specimens were directly subjected to unconfined compression tests after the curing period. Regarding the outcomes obtained, both synthetic and biological polymer use induced strength gain. Guar gum which is a biological polymer is the most effective that improves the strength by around 8 times than pure clay. This increment ratio varied between 2 and 3.5 times in polyacrylamide polymer, which is a greater strength increase than in previous studies. In addition, curing time has no significant effect on strength gain in anionic polyacrylamide-contained specimens. It was also observed that freezing–thawing caused a drastic reduction in strength by around 5 to 60%, however, the anionic polymer is the most resistant to freeze–thaw considering the strength loss. As a result, eco-friendly polymers are suitable in regions exposed to freeze–thaw action between the seasons.

Improving aggregate stability and hydraulic properties of Sandy loam soil by applying polyacrylamide polymer

Improving soil properties, especially in arid and semiarid regions, is an urgent need for sustainable food production. This study aims to evaluate the effect of applying two types of anionic polyacrylamide polymers (PAMs) with different molecular weights on: (1) soil aggregate stability, (2) infiltration rate and (3) saturated hydraulic conductivity of sandy loam soil and introduce a novel modelling approach to predict the effect of PAM addition on the mentioned soil properties. Polymers were applied at five different concentrations; 0, 100, 250, 500 and 1000 mg L−1. Direct positive relations between the concentrations of PAM (low and high molecular weight) and saturated hydraulic conductivity and infiltration rate were observed. Nevertheless, the relations were more pronounced in case of low molecular weight PAM. The difference between the effect of the two PAMs on infiltration rate was statistically significant at α = 0.05. On the other hand, the differences were not significant except for the 1000 mg L−1 concentration in case of saturated hydraulic conductivity. Meanwhile, concentration has an effect on increasing soil aggregate stability only in case of low molecular weight PAM. At the concentration 1000 mg L-1 of low molecular weight PAM, aggregate stability and saturated hydraulic conductivity increased 3-fold while infiltration rate increased by more than 7-fold compared to the control. It is hypothesized that the change in the mentioned properties is correlated to the amount of PAM adsorbed by the soil and hence they can be used as surrogate parameters of adsorption. Modified versions of the Langmuir and Freundlich isotherm equations were used to model the change in aggregate stability and saturated hydraulic conductivity in response to the PAM concentration. The pseudo-first and second kinetics models were applied to predict the change in infiltration rate. The models showed excellent fit to the experimental data, thus supporting our hypothesis. The results suggest that low molecular weight PAM is more efficient in improving the physical properties of sandy loam soil. The modelling approach presented in this work may be extended to other types of soil. Other isotherm models may be used to predict the response of soil to PAM concentration where the Langmuir or Freundlich isotherms do not apply. This modelling approach provides land managers with a decision support tool to optimize PAM application.

Investigation the Efficiency of Soil Stabilizers against Soil Loss and their Effects on Chemical Properties of Soil

Soil erosion and dust storms are the main causes of air pollution in regions where there are dust emitting centers and in their adjacent locations. In recent years, various methods have been considered for stabilizing soil surface against wind erosion. In this study, the effects of two stabilizers (anionic polyacrylamide polymer and vegetable-based mulch) for reducing soil loss at four levels of concentration (0, 15%, 30%, and 60%) on three kinds of soils in western Khuzestan, Iran have been studied. The study was conducted in natural and laboratory-based conditions in four, time intervals (0, 3, 6, and 12 months). Moreover, the study covered the persistence and influence of stabilizers on soil chemical properties. The results showed that wind erosion in no treatment was between of 16.36 kg/m2/hand 26.73 kg/m2/ h. The statistical results showed that there was a significant difference between the no treatment and soils treated with stabilizers. The polymer reduced soil loss by more than 90%. Mulch efficiency reduced in natural conditions after 6 months; however, there were no changes in laboratory conditions. There was no significant difference between polymer efficiency in the laboratory and natural conditions and the polymer was resistant in natural and laboratory conditions. Polymer increased EC, pH, and SAR in the soil after 1 year. Mulch decreased pH and SAR but did not change EC.

An experimental study of the performance of low-molecular weight polymer for enhanced heavy oil recovery in a heterogeneous media

The goal of enhanced oil recovery is to improve sweep efficiency in the reservoir by the injection of artificial materials in order to reduce the trapped oil saturation. In this study, the application of an anionic polyacrylamide polymer was investigated for heavy oil recovery based on the results of rheological measurements and oil recovery experiments. The properties of the polymer solution were interpreted by the use of well-known rheological models and oil recovery experiments were performed using a heterogeneous two-dimensional glass micromodel saturated with heavy oil of 270 cP. To provide a better understanding of the microscopic efficiency of the process, analysis of continuously provided pictures during the experiments by the use of image processing technique was performed. Rheological results combined with microscopic observations revealed that the non-Newtonian behavior of the solution enhances the sweep efficiency of the both pore throats and pore bodies. Macroscopic observations showed the ultimate oil recovery of 56% and dramatic improvement in breakthrough time during polymer flood in comparison to water flood. In addition, the microscopic pictures disclosed that the pulling effect and stripping mechanisms are responsible mechanisms for the high microscopic sweep efficiency during polymer flooding.

Clarification and solvent extraction studies of a high talc containing copper aqueous solution

Effects of different flocculants on the clarification of a copper aqueous solution destined for solvent extraction were investigated. The test work was conducted on the pregnant leaching solution (PLS) of a high talc containing copper ore that had a high propensity of bearing a large amount of suspended solids. The clarification test work was conducted using three commercial high molecular anionic polyacrylamide polymer flocculants: rheomax® DR 1050, brontë 103, and senfloc® 2660. Solvent extraction tests were done using 30% (v/v) LIX 984N at pH 1.8. The parameters of clarification and solvent extraction were the flocculant dosage (0, 58.14, 116.28, 232.56 and 348.84g/t) and the ratio O/A (1/5, 1/2, 2/3, 1/1, 3/2, 2/1, and 5/1), respectively. The analysis results of the PLS showed it contained 2000ppm of solids in suspension. The optimal conditions for clarification and solvent extraction were a dosage of 116.28g/t and an O/A of 1.5, respectively. Under optimal conditions, the residual total suspended solids (TSS) in the clarified solutions were 1196ppm, 954ppm, and 928ppm; the phases disengagement time (PDT) for organic continuous dispersion were 70s, 80s and 60s; the percent TSS entrained in the organic phase were 26.76%, 28.93% and 25.32%; copper recoveries were 97.63%, 98.98% and 95.13%, with rheomax® DR 1050, brontë 103 and senfloc® 2660, respectively.

Adsorptive removal of As(III) ions from water using spent grain modified by polyacrylamide

In order to enhance the removal efficiency of As(III), a pre-oxidation process is generally applied first to convert As(III) to As(V), which may cause unwanted new contaminants. To overcome this problem, efforts were made to develop an effective way to remove As(III) directly without an oxidation step. The effect of polyacrylamide polymers (PAMs) such as anionic PAM, cationic PAM and nonionic PAM, on As(III) ion adsorption by spent grain (SG) was investigated. The physico-chemical properties of the three PAM-polymerized SGs (APSG (anionic PAM-polymerized modified spent grain), CPSG (cationic PAM-polymerized spent grain) and NPSG (nonionic PAM-polymerized spent grain)) were analyzed using Fourier transform infrared (FT-IR), scanning electron microscope (SEM) and zeta potential. Batch experimental data showed that the sequence of preferential adsorption for As(III) was APSG>CPSG>NPSG. Active functional groups such as amino group (NH2), carbonyl group (CO), C–N bond of the amide group (CONH2), and hydroxyl group (O–H) were responsible for As(III) adsorption. Many tubular structures occurring on the surface of APSG possibly increase the specific surface areas and favor the adsorption of As(III) ions. A fixed-bed study was carried out by using APSG as an adsorbent for As(III) from water. Three factors such as bed height, initial concentration and flow rate were studied, and breakthrough curves of As(III) were obtained. The Adams–Bohart model was used to analyze the experimental data and the model parameters were evaluated.

The removal of COD, TSS and colour of black liquor by coagulation–flocculation process at optimized pH, settling and dosing rate

Pulp and Paper mills are generating millions of tons of wastewater and are major source of water pollution. In this research work, pulping wastes have been characterized and found to contain very high COD, TSS and colour. Coagulation–flocculation process was performed to find out the performance of different coagulants and flocculants like alum, ferric chloride, aluminium chloride, ferrous sulphate, poly aluminium chloride (PAC), cationic and anionic polyacrylamide polymers in individual form as well as in different combinations. The effects of dosing rate, settling time and pH were examined for reduction of COD, TSS and colour. Coagulants used in combinations were found to be more effective in reducing COD, TSS and colour instead of using individual form. The initial pH of the effluent for coagulation process was found to have remarkable effect on COD, TSS and colour removal. The most effective results were found using cationic and anionic polyacrylamide combination with ferric chloride and aluminium chloride and reduction of 76% COD, 95% TSS and 95% colour were observed at pH<3.

Effects of anionic polyacrylamide on maize growth: a short term 14C labeling study

Aims Various anionic polyacrylamide polymers (PAMs) are frequently used to improve soil properties and reduce erosion. However, the effects of their application on plant growth remain unclear. Methods Aggregate-free loess with high water holding capacity was used as growing substrate to test the effects of two rates (10 and 40 kgha �1 ) of a linear PAM on the growth of maize (Zea maize L.) for a period up to one month. The PAM effects were evaluated at three levels of soil water content (SWC) and three plant ages, based on water consumption, shoot and root biomass, as well as allocation of recently assimilated C in plants and soil using 14 C labeling. Results Both SWC and maize age significantly affected water consumption, biomass accumulation, and 14 C allocation in plant parts and soil. Even though consistent increases in plant biomass and total assimilated 14 C were observed, the effects of PAM application were insignificant on either of these variables. Conclusions The effects of PAM application were directly connected to soil rather than to maize, and could be masked by the non-structural loess. The effects tended to be age and soil-moisture specific, and were modulated by the rhizodeposition processes. The possible mechanisms of PAM application on plant growth were also discussed.

Uso de poliacrilamida como estrategia de control de erosión en un suelo altamente erodado de Puerto Rico.

La alta sedimentación procedente de terrenos dedicados a la agricultura y la construcción es una de las principales fuentes de contaminación de los cuerpos de agua superficiales de Puerto Rico. El uso de polímeros amónicos de poliacrilamida (PAM) ha ganado rápido reconocimiento como una alternativa costo-efectiva para el control de la erosión. En este estudio evaluamos la efectividad de varias formulaciones y dosis de PAM aniónico en un suelo altamente meteorizado del trópico (Corozal Arcilloso—Typic Hapludult) en condiciones de alta pendiente (20%). Se llevó a cabo una serie de experimentos con cajas de escorrentía siguiendo el protocolo del Proyecto Nacional de Simulación de Lluvia. Se evaluaron tres formulaciones de PAM: SOILFLOCâ"¢ 300 E, SOILFIXâ"¢ LDP, y una formulación sintética (PAMAld) de la compañía Aldrich Chemical. Cada formulación se evaluó en las siguientes dosis: 0 (control), 20 kg/ha, 80 kg/ha, y 120 kg/ha de ingrediente activo. Los experimentos de lluvia simulada se realizaron a uno, dos, ocho, 30, y 60 días luego de la aplicación del polímero. Las dosis de PAM de 80 y 120 kg/ha redujeron significativamente la concentración de sedimentos en el agua de escorrentía comparadas con el control y la dosis de 20 kg/ha. En sus dosis más altas todas las formulaciones de PAM redujeron la concentración de sedimentos en el agua de escorrentía en más de 75% comparado con la del control en todos los eventos de lluvia realizados. La efectividad de PAM a la dosis de 20 kg/ha se perdió luego del segundo evento de lluvia. Durante el tercer evento de lluvia la reducción en la concentración de sedimentos (comparado con la del control) fue menos de 50% en el caso de la formulación PAM-Ald y menos de 20% en el caso de SoilFloc para la dosis de 20 kg/ha. El tiempo requerido para la generación de escorrentía dependió grandemente del contenido de humedad del suelo. Durante los dos últimos eventos de lluvia (30 y 60 días luego de la aplicación de PAM), el tiempo requerido para la generación de escorrentía se afectó significativamente por las dosis de PAM. En el tratamiento control y en el de la dosis más baja de PAM la escorrentía ocurrió más rápido que en aquéllos con las dosis más altas de PAM. Estos resultados pudieran atribuirse a los efectos de sellado de superficie y aumentos en la formación de surcos o zanjillas en la superficie del control y en la de la dosis más baja (20 kg/ha) de PAM. Sesenta días luego de la aplicación del polímero, los estimados de producción de sedimentos cumulativos para un evento de 30 minutos de escorrentía fueron de 2.3 Mg/ha para el tratamiento control vs. 0.18, 0.07, y 0.08 Mg/ha para las dosis de 120 kg/ha de SoilFloc, SoilFix y PAM-Ald, respectivamente.

Dewatering of phosphorus extracted from liquid swine waste

Phosphorus (P) recovery from liquid swine manure is an attractive technology when on-farm application of liquid swine manure is not an option. We developed a technology that enables separation of this P, but its high moisture content makes transportation difficult. In this work, we investigated dewatering procedures to concentrate the P product. Sludge rich in calcium phosphate (>20% P 2O 5) was obtained using a field prototype, and it was further dewatered using a combination of polymer treatment and filter bags. Anionic polyacrylamide polymer treatment (⩾20 mg/L) was effective to flocculate the P-rich sludge, which enhanced filtration and dewatering. Without polymer, filtration was incomplete due to clogging of filters. Non-woven polypropylene and monofilament filter bag fabrics with mesh size ⩽200 μm retained >99% of suspended solids and total P. Solids content dramatically increased from about 1.5% to >90%. These dewatered solids can be transported more economically off the farm for use as a valuable fertilizer material.

Wastewater treatment polymers identified as the toxic component of a diamond mine effluent.

The Ekati Diamond Mine, located approximately 300 km northeast of Yellowknife in Canada's Northwest Territories, uses mechanical crushing and washing processes to extract diamonds from kimberlite ore. The processing plant's effluent contains kimberlite ore particles (< or =0.5 mm), wastewater, and two wastewater treatment polymers, a cationic polydiallydimethylammonium chloride (DADMAC) polymer and an anionic sodium acrylate polyacrylamide (PAM) polymer. A series of acute (48-h) and chronic (7-d) toxicity tests determined the processed kimberlite effluent (PKE) was chronically, but not acutely, toxic to Ceriodaphnia dubia. Reproduction of C. dubia was inhibited significantly at concentrations as low as 12.5% PKE. Toxicity identification evaluations (TIE) were initiated to identify the toxic component of PKE. Ethylenediaminetetraacetic acid (EDTA), sodium thiosulfate, aeration, and solid phase extraction with C-18 manipulations failed to reduce PKE toxicity. Toxicity was reduced significantly by pH adjustments to pH 3 or 11 followed by filtration. Toxicity testing with C. dubia determined that the cationic DADMAC polymer had a 48-h median lethal concentration (LC50) of 0.32 mg/L and 7-d median effective concentration (EC50) of 0.014 mg/L. The anionic PAM polymer had a 48-h LC50 of 218 mg/L. A weight-of-evidence approach, using the data obtained from the TIE, the polymer toxicity experiments, the estimated concentration of the cationic polymer in the kimberlite effluent, and the behavior of kimberlite minerals in pH-adjusted solutions provided sufficient evidence to identify the cationic DADMAC polymer as the toxic component of the diamond mine PKE.

Anionic Polyacrylamide Polymer Adsorption by Pyrophyllite and Montmorillonite

AbstractThe mechanism by which the anionic polymers interact with platelets of 2:1 clay minerals is not fully understood. The objective of the present study was to evaluate the effect of the electric field associated with the basal and edge surfaces of the clay minerals on the adsorption of anionic polymers. Two negatively charged polymers, PAM90 and ACC86, of the same molecular weig ht (2 × 105 g mol−1) but with different degrees of hydrolysis (90 and 20%, respectively), were used. The effect of pH (6, 10), NaCl concentration (0, 10 mmolC L−1) and clay particle size on PAM90 adsorption by pyrophyllite and the effect of NaCl concentration on the adsorption of these polymers by Na-montmorillonite in aqueous suspensions were studied. Adsorption of PAM90 on pyrophyllite was greater at pH 6 than at pH 10 and greater in 10 mmol L−1 NaCl than in distilled water. Adsorption of PAM90 on pyrophyllite increased with decreasing particle size. On pyrophyllite the high-charge-density PAM90 was adsorbed to a greater extent than the low-charge-density ACC86; by contrast, ACC86 adsorption was greater than that of PAM90 on Na-montmorillonite. These results were attributed to the repulsive forces which develop between the negatively charged extended-chain polymer and the extended negative electric field associated with the basal surfaces, around the Na-montmorillonite platelets. The results may suggest that the edge surfaces play a major role in PAM adsorption.

Anionic Polyacrylamide Polymers Effect on Rheological Behavior of Sodium-Montmorillonite Suspensions

Polyacrylamide (PAM) is a long-chain synthetic polymer that acts as a strengthening agent, binding clay particles together. The interaction between anionic PAM and clay particles is not well understood yet. This interaction was evaluated by rheological measurements for Na-montmorillonite suspensions. Three anionic PAMs of three molecular weights (MWs) (3.5 × 103, 2 × 105, and 8 × 106 g mol −1) at similar hydrolysis levels (>85%) and three anionic PAMs at various degrees of hydorlysis (DH) (15, 33, and 92%) of similar MW were studied. In an electrolyte-free clay suspension at DH >85%, only the polymers with high MWs (2 × 105, and 8 × 106) could form a three-dimensional structure of clay platelets. The smallest polymer molecule size (3.5 × 103) was too short for bonding two adjacent platelets. At similar MW, the effect of the polymers increased with DH. At NaCl concentration of 10 mmolc L−1, at which the attractive forces between clay platelets were weak, the polymers had a significant impact on flow behavior. The effectiveness of the polymers increased with increasing MW and DH. At NaCl concentration of 100 mmolc L−1, the three polymers of DH > 85% stabilized flocs that already existed in the clay suspension. The effectiveness of the polymers in bridging adjacent clay flocs increased as their DH decreased. The polymer conformation factor has a greater impact on clay structure stabilization in suspension than the electrostatic repulsion effect. The clay structure stability was increased with increasing polymer electrostatic negative charge for similar molecular weights.

Anionic Polyacrylamide Polymers Effect on Rheological Behavior of Sodium‐Montmorillonite Suspensions

Polyacrylamide (PAM) is a long‐chain synthetic polymer that acts as a strengthening agent, binding clay particles together. The interaction between anionic PAM and clay particles is not well understood yet. This interaction was evaluated by rheological measurements for Na‐montmorillonite suspensions. Three anionic PAMs of three molecular weights (MWs) (3.5 × 103, 2 × 105, and 8 × 106 g mol −1) at similar hydrolysis levels (&gt;85%) and three anionic PAMs at various degrees of hydorlysis (DH) (15, 33, and 92%) of similar MW were studied. In an electrolyte‐free clay suspension at DH &gt;85%, only the polymers with high MWs (2 × 105, and 8 × 106) could form a three‐dimensional structure of clay platelets. The smallest polymer molecule size (3.5 × 103) was too short for bonding two adjacent platelets. At similar MW, the effect of the polymers increased with DH. At NaCl concentration of 10 mmolc L−1, at which the attractive forces between clay platelets were weak, the polymers had a significant impact on flow behavior. The effectiveness of the polymers increased with increasing MW and DH. At NaCl concentration of 100 mmolc L−1, the three polymers of DH &gt; 85% stabilized flocs that already existed in the clay suspension. The effectiveness of the polymers in bridging adjacent clay flocs increased as their DH decreased. The polymer conformation factor has a greater impact on clay structure stabilization in suspension than the electrostatic repulsion effect. The clay structure stability was increased with increasing polymer electrostatic negative charge for similar molecular weights.

Primary treatment of a soybean protein bearing effluent by dissolved air flotation and by sedimentation

The present paper reports on work performed on the recovery of proteins suspended in the effluent of a soybean protein plant. The work involved studies of effluent characterization, protein suspension destabilization, dissolved air flotation (DAF) and gravity settling. The flotation and settling tests were performed both at a batch bench scale and at a continuous plant scale in the actual industrial operation. The soybean proteins, present as a colloidal suspension in the effluent, are dispersed by combined electrostatic repulsion and steric stabilization mechanisms. The destabilization and aggregation of the proteins into high quality flocs were achieved by addition of 200–300 mg/l FeCl 3, setting the pH at the isoelectric point of the proteins (pH 4.5) and an anionic polyacrylamide polymer (high molecular weight) dosage of 2–3 mg/l. The bench scale tests indicated under these conditions that a solid-liquid separation can be made by both DAF and gravity settling with DAF giving superior results. However, in the industrial plant tests, gravity settling proved generally to give better separation efficiencies. In plant operation the DAF process worked well only if the flocs were sufficiently hydrophobic and resistant to mechanical degradation, which was not always true in the actual operation. The settling process was much less sensitive to feed stock variations.

Flocculation of hematite fines by anionic polyacrylamide polymers

Flocculation studies on iron-ore fines (size < 10 μm) were conducted using three anionic polyacrylamide polymers over the pH range 4.0–10.0 and flocculant dosages up to 0.20 kg/ton. The flocculation was favourable under acidic conditions and was helped substantially by CaCl 2 additions in alkaline conditions. Zeta potential measurements indicated a specific adsorption of polymers. Adsorption studies on the system indicated a pseudo-Langmuir type isotherm. Specific free energy of adsorption was estimated to be −26 to −34 kJ/mole for the three flocculants. Hydrogen bonding and electrostatic forces mainly appeared to influence flocculation in the system studied. Selective flocculation of iron-ore-silica fines mixtures was favourable with the above polymers, with the help of sodium silicate.

Polyacrylamide to Improve Water Flow and Salt Removal in a High Shrink‐Swell Soil

AbstractReclamation of salt‐affected high shrink‐swell soils using chemical amendments combined with deep loosening and tile drainage is very expensive. As an alternative, the utilization of cracks as pathways for water and salts is possible if these cracks could be stabilized by the application of a polyacrylamide (PAM) polymer and their complete closure prevented upon rewetting. A laboratory column study was conducted on two soil samples with exchangeable sodium percentages (ESP) of 8 and 25 from a heavy‐textured, swelling soil. The soil samples were packed into columns, ponded with irrigation water for 24 h, then drained and dried to create cracks. After drying, the soil samples were ponded for 24 h with irrigation water containing 0, 25, 75, and 200 mg L−1 of an anionic polyacrylamide polymer, allowed to drain, and dried. The treated soils were then ponded without drainage for 1, 6, 12, and 24 h to allow crack closure and the hydraulic conductivity (HC) and effluent salinity were measured. The experiment was repeated except that the polymer solution was added to the soil without initially creating the cracks. An additional study was carried out to test the durability of the polymer when subjected to wetting and drying cycles. Increasing the amount of polymer significantly increased the HC and salt removal in the cracked soils. When the polymer solution was applied directly onto soils without initially creating cracks, there was no increase in HC on the ESP 8 soil and a small increase on the ESP 25 soil. The polymer had a stabilizing effect on soil cracks, but the increase in HC did not persist through several wetting and drying cycles.