Treatment of the production waste water of Konstantinovka Refractory Plant

Conclusions The coagulating action of aluminum sulfate and of the combination of it with polyacrylamide on a suspension of chamotte and clay, leading to a significant increase in particle size of the dispersed phase, was investigated.The presence of a threshold value of the addition of coagulant as an important production parameter determining the unstable suspension type sedimentation of particles was shown.To disturb the stability of the systems and to accelerate the clarification process of waste waters contaminated with chamotte and clay the necessary additions of reagents are 25–50 mg/liter of aluminum sulfate and 5 mg/liter of polyacrylamide.Translated from Ogneupory, No. 6, pp. 42–44, June, 1985.     

Dewatering of Phosphatic Clay Waste by Flocculation

This work focuses on the dewatering of phosphatic clay waste of Egyptian Abu‐Tartur phosphate ore by flocculation using polyacrylamides to enhance the dewatering rate and recycling of the process water. The experimental program includes sieving, hydrocyclone separation and flocculation of the overflow of hydrocyclone. Results revealed that the coarser fraction larger than 32 micron is enriched with P₂O₅ whereas the undersize fraction is only clay. Hydrocyclone successfully separates two cuts; the underflow fraction is enriched with phosphate while the other is just clay. By this technique, the P₂O₅ content is increased from 15.57 % in the feed to 26 % in the underflow cut which constitutes about 39.8 % by weight. Flocculation helps to increase both the settling rate of phosphatic clay waste and recycling the process water. The former criteria increased 37 times by using anionic polyacrylamide (A130) as compared to the natural settling rate of the same waste. Results were explained in the light of a model which suggests that the flocculation mechanism involves two stages: the first stage involves the adsorption of the reagent on the particles whereas the second forms aggregate flocs. Formation of aggregate flocs takes place by tangling the polymer molecules, so that one polymer molecule will be adsorbed at several points on the surface of the particle, leaving loops which may be of varying lengths, projecting out from the surface. Partially covered particles would collide to form bridges.     

Synthesis of Polyelectrolyte and Studies of its Conductivity Changes with Respect to Molecular Weight

Aqueous solutions of acrylamide monomer were irradiated by γ-rays using a Co-60 source to synthesize polyacrylamide of different molecular weight (M_w). Solubility tests together with ultraviolet and infrared spectroscopic studies were performed for examining the irradiated samples to ensure that the prepared products were gradually converted from monomer to polymer (polyacrylamide), depending on the radiation dose. Various physico-chemical properties like polymer conversion, gel content, viscosity, and molecular weight of the products were determined. The conversion of polymer from monomer is initiated at a dose of 0.06 kGy and completed at about 0.14 kGy. The gel point, which indicates a dose for the onset of a network polymer structure, is identified to be 0.15 kGy providing valuable information about γ-ray synthesis of polyacrylamides. Viscosity and molecular weight are found to increase with radiation dose. Since polyacrylamides exhibit polyelectrolytic behavior in aqueous solutions, studies on conductivity changes of polyelectrolytes with respect to M_w, which is the main issue of this investigation, also were performed. The equivalent conductance of polyelectrolyte solutions was found to decrease with the molecular weight of the synthesized polymer. This change of conducting property of the prepared samples is explained based on the theory of polyelectrolyte solutions.     

The effects of branching and other physical properties of anionic polyacrylamides on the flocculation of domestic sewage

This investigation was undertaken to evaluate the effect of long-chain branching of anionic polyacrylamides on the flocculation of domestic sewage. The polyelectrolytes were polymerized using a redox couple, selectively hydrolyzed, and then characterized by means of light-scattering photometry. Coagulation tests were then employed to evaluate the synthesized polymers. The optimum polymer dose for suspended solids removal was used as the basis for evaluating each anionic polyacrylamide fraction with respect to its ability to flocculate domestic sewage. The results of this investigation indicated that as the weight-average molecular weight increased, the optimum polymer dose decreased. For polymers of similar molecular weights and differing radii of gyration, as the radius of gyration increased, the optimum polymer dose decreased, indicating that the “linear” polymers were more efficient in removing suspended solids than the “branched” polymers.     

Synthetic polyelectrolytes of varying charge densities but similar molar mass based on acrylamide and their applications on palm oil mill effluent treatment

Cationic polyacrylamides of varying charge densities but similar molar mass were synthesized using free radical polymerization and Mannich reaction, characterized by different methods and applied as flocculants for palm oil mill effluents (POME). Flocculant performance was assessed by determining the polymer dosage, pH of POME and the removal efficiency of the resulting supernatants using turbidity, suspended solids and chemical oxygen demand as indicators. The pH of POME was adjusted to 3 prior to flocculation. It was found that varying the charge density of the polymer from 48.2-485 C/g affects flocculant performance significantly. Polymer adsorption increased as the charge density of the polymers increased. High charge density cationic polyacrylamide (485 C/g) is the most effective polymer as it obtains 98% turbidity removal, 98.7% suspended solids removal and 54% chemical oxygen demand removal with a dosage as low as 32 mg/l at pH 3 of POME.     

Factors effecting a loss of flocculation activity of polyacrylamide solutions: Shear degradation,cation complexation,and solution aging

Polyacrylamide and poly(acrylamide-co-acrylic acid) flocculant solutions were subjected to shear degradation in a rotating cone instrument. At constant shear rate, shear degradation was minimized (highest limiting intrinsic viscosity) by the use of a lower solution concentration and high ionic strength of the polymer solution. Resistance to shear degradation also increased with increasing anionic character of the polyacrylamide. Sheared polymers showed reduced performance as flocculants of coal preparation plant tailings, their major commerical application in the U.K. Partially anionic polyacrylamide solutions were completely inactivated in the presence of certain multivalent cations. Aluminium, iron_III, lead, copper, and zinc ions formed complexes with the carboxyl groups on the polymer, resulting in zero flocculation activity. Nonionic polyacrylamides were unaffected. Viscosity–aging of polyacrylamide solutions was observed over a period of several months, but was insufficient to affect the flocculation activity. In the presence of 3% ethanol or methanol, no aging was observed in solutions stored for over a year.     

Effect on 2,2′-bipyridine adsorption of poly(vinyl alcohol) adsorbed on Na-kaolinite

The adsorption (pH 6) of 2,2′-bipyridine (BP) on Na⁺-kaolinite and on samples of the same clay containing 4.35 and 7.45 mg/g, respectively, of previously adsorbed poly(vinyl alcohol) (PVA) was studied. Specific adsorption of BP decreases with increasing clay particle size in the suspension as a result of particle association. Aqueous suspensions with a 1–4% concentration of kaolinite exhibit flocculation in the absence or presence of PVA, forming clusters of 43–64 units of single clay particles. The PVA adsorbed on the surface of sodium kaolinite particles causes partial dispersion of the kaolinite in the aqueous suspension; however, 7.45 mg/g of PVA adsorption or even lower (4.35 mg/g) is not able to fully impede the association of kaolinite particles.     

聚丙烯酰胺的合成技术及应用研究

聚丙烯酰胺 (PAM)是一类新型的功能高分子产品 ,是水溶性高分子的重要组成部分。从聚丙烯酰胺的定义出发 ,简单介绍了聚丙烯酰胺的发展历史。对国内外近年来聚丙烯酰胺合成技术 :水溶液聚合、乳液聚合、辐射聚合、胶束聚合、光引发聚合、沉淀聚合作了归纳总结 ,最后展望了聚丙烯酰胺的应用前景     

Formation and characteristics of cationic-polymer/bentonite complexes as adsorbents for dyes

The adsorption of cationic polymer, i.e., epicholorohydrin-dimethylamine polyamine (EPI-DMA), on bentonite particles was investigated under various conditions of bulk polymer concentration, pH, inorganic salts, and temperature. The resulting high adsorption rate and alkaline solution (pH = 7–11) effect indicated a strong electrostatic interaction between the clay particles and EPI-DMA molecules. Addition of salt can also influence the adsorption of EPI-DMA onto bentonite by affecting the clay particle sizes, the polymer zeta potential and etc. The Freundlich and Langmuir isotherm models were employed and fit the experimental data well in the low EPI-DMA concentration range 0.5–5.0 mg L^− 1. The enthalpy implied by the temperature dependence of adsorption of EPI-DMA on bentonite is 7.93 kJ mol^− 1, suggesting that neither coordination exchange nor chemical bond forces exit in this system. In addition, at high temperatures, larger amounts of EPI-DMA were adsorbed by bentonite, which indicated that increased entropy in the dissolved EPI-DMA molecules contributes to adsorption. The X-ray diffraction (XRD) analysis showed that besides the EPI-DMA molecules intercalated between the layers of bentonite, excess polymer molecules were adsorbed onto polymer loops protruding from the surface of the complex. The TGA and corresponding DSC plots demonstrated that the EPI-DMA polymer had intercalated into the clay layers and thus the EPI-DMA/bentonite was more hydrophobic than natural bentonite. With the addition of EPI-DMA polymer, the negatively charged clay particles increased to a net positive charge and the capacity for dye removal also went up with increasing polymer contents in EPI-DMA/bentonite complexes.     

Surface modification of sepiolite particles with polyurethane and polyvinyl alcohol

Sepiolite is a clay mineral that has many industrial applications due to its advantageous properties such as white color, low specific gravity, high absorption capacity, chemical composition and low thermal conductivity. In this study, the effect of the addition of polymers, polyvinyl-alcohol and polyurethane, on the rheological properties of the sepiolite dispersions have been investigated. The rheological parameters of clay suspensions can be used to examine particle–particle interactions. The polymers that have been added to the clay suspensions interact with clay particles, depending on their ionic or non-ionic character. Firstly, the sepiolite dispersions were characterized by the rheological properties, mineral structure and content. Then the effect of the polymers on the flow, structural, and surface properties of sepiolite dispersions was investigated by rheological, electrokinetical, and scanning electron microscopy (SEM) measurements. The measurements showed that polymer molecules bind on the surface of sepiolite particles and changed the flow properties of the dispersions as stable dispersions at some certain concentrations. It is also determined that PU polymer covered the surface of the sepiolite faster than PVA, but the coverage of the PVA was much more smoothly. The thermal properties of the sepiolite improved with PVA more than PU, as a result of the homogenous surface coverage.     

Mechanical stability of high‐molecular‐weight polyacrylamides and an (acrylamido tert‐butyl sulfonic acid)–acrylamide copolymer used in enhanced oil recovery

High‐molecular‐weight partially hydrolyzed and sulfonated polyacrylamides are widely used in enhanced oil recovery (EOR). Nonionic polyacrylamide and polyacrylamide‐based microgels are also used in water shut‐off treatments for gas and oil wells. A comparative study of the mechanical degradation for three linear polyacrylamides and a microgel is presented. Mechanical degradation is quantified from the loss of the viscosity of the polymer solution as it passes through a stainless steel capillary with a length of 10 cm and an internal diameter of 125 µm. The critical shear rate above which degradation increases exponentially was found to depend on the chemical structure of the polymer, molecular weight, and electrolyte strength. The nonionic polyacrylamide shows higher degradation and lower critical shear rate compared with a sulfonated polyacrylamide with similar molecular weight. Moreover, the nonionic polyacrylamide with a higher molecular weight results in lower mechanical degradation. The higher mechanical stability of the sulfonated polymer is attributed to the higher rigidity of its molecules in solution. On the other hand, the ability of the high‐molecular‐weight polymers to form transient, flow‐induced microgels boost their mechanical stability. This ability increases with the increase in the molecular weight of the polymer. Indeed, the microgel solution used in this study demonstrates exceptional mechanical stability. In general, mechanical stability of linear polymers used in chemical enhanced oil recovery can be enhanced by tailoring a polymer that has large side groups similar to the sulfonated polyacrylamide. Also, polyacrylamide‐based microgels can be applied if high mechanical stability is required. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40921.     

Silver- and Zinc-Decorated Polyurethane Ionomers with Tunable Hard/Soft Phase Segregation

Segmented polyurethane ionomers find prominent applications in the biomedical field since they can combine the good mechanical and biostability properties of polyurethanes (PUs) with the strong hydrophilicity features of ionomers. In this work, PU ionomers were prepared from a carboxylated diol, poly(tetrahydrofuran) (soft phase) and a small library of diisocyanates (hard phase), either aliphatic or aromatic. The synthesized PUs were characterized to investigate the effect of ionic groups and the nature of diisocyanate upon the structure–property relationship. Results showed how the polymer hard/soft phase segregation was affected by both the concentration of ionic groups and the type of diisocyanate. Specifically, PUs obtained with aliphatic diisocyanates possessed a hard/soft phase segregation stronger than PUs with aromatic diisocyanates, as well as greater bulk and surface hydrophilicity. In contrast, a higher content of ionic groups per polymer repeat unit promoted phase mixing. The neutralization of polymer ionic groups with silver or zinc further increased the hard/soft phase segregation and provided polymers with antimicrobial properties. In particular, the Zinc/PU hybrid systems possessed activity only against the Gram-positive Staphylococcus epidermidis while Silver/PU systems were active also against the Gram-negative Pseudomonas aeruginosa. The herein-obtained polyurethanes could find promising applications as antimicrobial coatings for different kinds of surfaces including medical devices, fabric for wound dressings and other textiles.     

Effect of the monomer ratio and initiating system on the disperse composition of polyacrylonitrile copolymers

Conclusions The mean size and polydispersity of polymer particles are increased on increasing the MMA/(AN, NaVS) ratio, as a function of the initiating systems used, in the following order: ammonium persulfate—rongalite, persulfate—bisulfite, and persulfate—metabisulfite.The PAN copolymer suspensions obtained under laboratory and under pilot plant conditions have identical mean particle sizes, but have a different disperse composition of the polymer particles.There is a slight dependence of the filterability resistance of polymer suspensions on the MMA/(AN, NaVS) ratio and on the initiating system used, which exerts no effect on the technological centrifuging regime.Of the investigated redox initiating systems, the most appropriae one for the manufacture of a PAN copolymer with an elevated MMA content is the ammonium persulfate—sodium bisulfite system.Bulgaria. Translated from Khimicheskie Volokna, No. 4, pp. 45–47, July–August, 1985.     

Static filtration of purified sodium bentonite clay suspensions. Effect of clay content

The effect of clay content on the static filtration properties of purified Na-montmorillonite suspensions was studied at two different pressures. The results of filtering parameters are as expected. When the clay percentage increases, the thickness (e) of the obtained cake increases, leading to the decrease of water loss (WL), and consequently, to the decrease of permeability (k). These decreases of WL and k are more important for the low applied pressure than for the high one.The differences between values of the different experimental parameters (WL and e) obtained at applied pressures of 5.7×10⁵ and 1.5×10⁵ Pa, as a function of clay content in the initial samples, show some singular points. At the clay content corresponding to the sol–gel transition (SGT), already determined by rheological measurements, ΔWL presents a change in concavity and Δe shows a maximum. Localisation of this maximum seems to be a simple way to detect the SGT by performing static filtration experiments of two series' of clay suspensions at two different pressures.According to the water contents obtained at the two pressures, all the cakes were localised in region (2), defined by Norrish (1954) as the “macroscopic” swelling paste of Na-montmorillonite. At low applied pressure, the texture of the cakes is identified by transmission electron microscopy (TEM). Generally, at low magnification, all samples are globally homogeneous. However, they present some regions more dense than others. At high magnification, the number of layers per particle seems to depend on SGT. Indeed, in the cake corresponding to 1% w/w of clay in the initial suspension, isolated layers are most frequent and particles with two to four layers per particle are scarce. In the cake obtained from the gel (3% w/w of clay) the most frequent stacking is about three layers per particle, and isolated layers almost disappear. In the cake obtained from gel, at the SGT (5.5% w/w of clay) which is the less oriented sample, the most frequent stacking is statistically also around three layers per particle but with a greater number of particles, some isolated layers appear again. After the sol–gel transition, in the cake obtained from the 7% sample (which is the most oriented sample), the number of particles increases but the number of layers in each particle decreases (two layers per particle most frequently occurs), and the number of isolated layers again rises. The frequent distances between the aggregates and particles were estimated on the TEM images of the cakes obtained at 1.5×10⁵ Pa. The distances between the particles of the cakes obtained under 5.7×10⁵ Pa was identified by X-ray diffraction (XRD). All these distances measured by the two techniques are compared with a linear extrapolation of Norrish's (1954) experimental data. At SGT, the cakes obtained at the two pressures correspond to aggregates connected with several distance configurations. However, the cakes obtained from the 3% initial clay content always show two distances (19 and 39 Å) at high pressure. At low pressure, one distance is about 300 Å, and the other is about 65 Å. This last distance disappears in the cake obtained from the more diluted suspension (1%) and only the higher distance persists. The 3% initial clay suspension seems to correspond to a “local osmotic transition”, which occurs between aggregated particles (or small aggregates) in the semi-diluted suspensions and isolated particles and/or layers in the more diluted suspensions.     

Partial volume and compressibility at infinite dilution of functionalized multilayer latex particles

A series of functionalized multilayer latex particles of P(butyl acrylate–methyl methacrylate–acrylic acid) was synthesized. The total acrylic acid concentration inside particles was varied from 0 to 25 wt.% and the number of particles in the system was held constant. The polymeric particles were studied by means of specific partial volume and specific partial compressibility at infinite dilution, which were calculated from density and sound speed measurements. From the behaviour of the partial properties at infinite dilution of the polar and non-polar groups of the polymer chain, it was concluded that the particle swells at low acrylic acids content due to the electrostatic repulsion between the carboxylic groups of the polymer chain. From 15 wt.% of acrylic acid up, the particle swells due to the electrostatic repulsion and to the incorporation of water molecules in the bounds of the particle layers. In this way, the hydration is non-homogeneous in the interior of each layer. These results are in agreement with the behaviour of the hydrodynamic radius determined by the quasi-elastic light scattering technique.     

Evaluation of a nanocomposite hydrogel for water shut‐off in enhanced oil recovery applications: Design,synthesis, and characterization

This work involves the synthesis of a nanocomposite hydrogel from just polymer and clay without the use of conventional organic crosslinkers. Conventional hydrogel design usually involves a multicomponent reaction that incorporates monomer (or polymer), initiator, and an organic crosslinker. However, because of the many limitations, setbacks, and inconsistencies involved with organic crosslinkers, authors herein present a nanocomposite hydrogel that incorporates polymer and clay only. It was found that these hydrogels show surprising mechanical toughness, tensile moduli, and tensile strengths. Study of gel behavior reveal physical interaction between polymer and clay, due in part to adsorption of polymer chains onto clay surface and ionic interactions between anionic carboxylate groups of polymer chains and positive clay surface. X‐ray diffraction patterns and Scanning Electron Microscopy revealed the formation of intercalated and exfoliated clay morphology. Increase in clay concentration and gel strength had a direct proportionality. The effect of clay concentration on hydrogel decomposition temperature was also reported by thermogravimetric analysis. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Preparation of alkaline PVA-based polymer electrolytes for Ni–MH and Zn–air batteries

Alkaline PVA polymer electrolyte with high ionic conductivity of about 0.047 S cm^–1 at room temperature was obtained by a solution casting method. The PVA polymer electrolytes, blended with KOH and H₂O, were studied by DSC, TGA, cyclic voltammetric and a.c. impedance methods. The PVA polymer electrolytes show good mechanical strength and high ionic conductivity. The electrochemical stability window at the metal–electrolyte interface is ±1.2 V for stainless steel. Ni–MH and Zn–air batteries with PVA polymer electrolytes were assembled and tested. Experimental results show good electrochemical performances of the PVA-based Ni–MH and Zn–air batteries.     

Water soluble acrylamide polymers, 2. Aging and viscous flow of aqueous solutions of polyacrylamide and hydrolyzed polyacrylamide

The aging of aqueous solutions of polyacrylamide which appears experimentally as a decrease of solution viscosity and which is probably caused by microorganisms may be prevented by the addition of a small amount (0.02 wt.-%) of an antimicrobial agent such as sodium azide. Aluminium chloride causes a very strong decrease of the viscosity during a prolongated storing time. The addition of aluminium ions to the polymer solution leads to a complexing of amidic groups with aluminium cations and probably also to decrease of the dimensions of individual polymer coils. The viscous flow of aqueous solutions of polyacrylamide and hydrolyzed polyacrylamides was studied as a dependence of the shear gradient D on the shear stress τ and was described by the relation D = k · τⁿ, where k and n denote constants. Both constants depend on the polymer concentration, the degree of polymerization and the content of carboxylic groups in the polymer. The greatest deviations from the Newtonian behaviour were found in the range of molecular weights over 2 · 10⁶ g/mol and practically no deviations were observed for polyacrylamide with molecular weights below 1 · 10⁶ g/mol. The dependence of the viscosity on the shearing time at different shear rates (300, 600 and 1200 s^?1) which was observed in solutions of polyacrylamide, hydrolyzed polyacrylamide and poly-(N,N-dimethyl)-acrylamide was explained by an entanglement model.     

Behaviour of poly(N-vinylcaprolactam) macromolecules in the presence of organic compounds in aqueous solution

Dynamic light scattering measurements have been performed for aqueous solutions of thermosensitive linear poly(N-vinylcaprolactam) (PVCa) macromolecules in the presence of NaCl and different water soluble amphiphilic organic compounds: pyrogallol (neutral amphiphilic compound), cetylpyridinium chloride (cationic surfactant) and sodium dodecylsulfate (anionic surfactant). A decrease in the macromolecular hydrodynamic diameter is observed upon addition of ionic surfactants (SDS, CPC) at low surfactant concentrations. This trend changes to an increase in the macromolecular hydrodynamic diameter at high surfactant concentration at temperatures below the temperature of polymer aggregation. This effect is in contrast with the behaviour of the systems of PVCa–non-ionic organic compounds (pyrogallol) and NaCl where we always observed the weak monotonic decrease of the hydrodynamic diameter with the increase in the concentration of organic compound, NaCl.

The behaviour of ternary systems PVCa macromolecules–ionic surfactant–pyrogallol and PVCa macromolecules–ionic surfactant–NaCl was studied. The addition of pyrogallol leads to the suppression of the intermacromolecular aggregation induced by temperature increase that is still observed at low surfactant concentrations and to the decrease of macromolecular hydrodynamic diameter. Also, the addition of NaCl to the PVCa/ionic surfactant systems results in the increase of the macromolecular hydrodynamic diameter. It is speculated that these results are due to the suppression of the cross-linking role of surfactant aggregates upon the addition of NaCl and pyrogallol.     

Water-soluble polymers as retention aids in a model papermaking system. III. Modified polyacrylamides

The pigment retention efficiency, in a model papermaking system, of anionically and cationically modified polyacrylamides was compared to that of the unmodified homopolymer. The anionic polyacrylamide is a much less efficient retention aid, especially at high pH's; the nonionic and cationic polymers perform similarly and without any marked pH dependence. However, it is the nonionic and anionic polyacrylamides which are similarly poor at fiber flocculation, at pH's between 4.5 and 7.5, whereas the cationic polymer is a good fiber flocculant. All three polymers stabilize pigment suspensions. The anionic polymer is not effective in heteroflocculation of mixed dispersions of fibers and pigment, whereas both the nonionic and cationic are good flocculants, the latter being less susceptible to overdosing. Equilibrium adsorption isotherms were determined; the cationic polymers is, unlike the other modified polyacrylamide, very well adsorbed by cellulose fibers. Onto titanium dioxide, polymers adsorbed in the order anionic < nonionic < cationic. A further differentiation of the cationic polymer is that it gives high pigment retention in sheet formation without markedly increasing the resistance to fluid flow through the forming sheet. Although a process of heteroflocculation is postulated for both nonionic and cationic polymers, in the former case it is thought that the primary adsorption is onto titanium dioxide, whereas with the latter it is onto cellulose.