Presence Of Polyacrylamide Research Articles

Influence of temperature on adsorption mechanism of anionic polyacrylamide in the Al2O3 –aqueous solution system

The influence of temperature on the adsorption mechanism of anionic polyacrylamide (PAM) on the alumina surface was studied in the temperature range 15–35 °C. The structure of polymer adsorption layer was determined from spectrophotometric, surface charge and zeta potential measurements. These methods enable determination of the following parameters: adsorbed amount of polymer, surface charge density and zeta potential of Al2O3 particles in the absence and presence of PAM. The influence of carboxyl groups content in the polyacrylamide macromolecules (varying from 5 to 50%) was also examined. The obtained results indicate that temperature influences the adsorption behaviour of anionic polyacrylamide on the Al2O3 surface. Slight increase of PAM adsorbed amounts with the temperature rise was obtained for the polymer samples characterized by the higher anionic group content (20, 30 and 50%). In the case of PAM with 5% content of these groups significantly larger adsorption was observed at 25 °C. The PAM presence causes also changes in electrokinetic properties (zeta potential and surface charge density values, as well as pHpzc and pHiep positions) of the examined system in the temperature range 15–35 °C.

Synthesis and Characterization of Ag@C Core–Shell Structures

Ag @ C core–shell structures were prepared using hydrothermal methods by AgNO 3 reduction with ascorbic acid in the presence of polyacrylamide (PAM). Temperature plays a key role in the formation of the core–shell structures. The roles of reactants, surfactant concentrations and reaction time on the morphologies of core–shell nanoparticles were investigated in detail. This synthetic method is one-pot synthesis, which is fast, high-yield and environmental-friendly for fabrication of Ag @ C core–shell structures. The surface properties of core–shell Ag @ C nanoparticles were characterized by Raman spectroscopy.

Effect of Polyacrylamide and Dextran-Polyacrylamide Graft Polymers on Absorption and Fluorescence Spectra of Hematoporphyrin

Absorption and fluorescence spectra of hematoporphyrin (HP) solutions in distilled water and in the presence of polyacrylamide and three dextran-graft-polyacrylamide branched polymers are studied. HP is shown to interact with the studied polymers leading to the destruction of HP aggregates, which is positive for the use of porphyrin as a photosensitizer in the photodynamic therapy. For the concentrations of the polymers of 0.001%, the studied polymers demonstrated a similar impact on HP.

Controllable immobilization of polyacrylamide onto glass slide: synthesis and characterization.

A novel route was introduced to synthesize dense polyacrylamide (PAM) onto the glass slide surface. To investigate the surface chemistry of the PAM on the glass slides, X-ray photoelectron spectroscopy (XPS) was utilized to obtain detailed chemical state information on the PAM layer constituents. The XPS peak data were consistent with the presented model of the PAM on the glass slide surface. Scanning electron microscopy and atomic force microscope data indicated the presence of PAM on the glass slides, which consist of nodules. The results showed that PAM was successfully immobilized onto glass slides with a two-tier structure under aqueous condition and a monolayer structure under anhydrous condition. Compared with those under aqueous condition, the controllability of the molecular layer on glass slides and the reproducibility under anhydrous condition were much better, which makes anhydrous condition an advisable condition for the study of the reaction mechanisms of glass slides modified by PAM.

Influence of fumed silica and additives on the gel formation and performance of gel valve-regulated lead-acid batteries

The gel electrolyte is an important factor that controls both the manufacturing process and the performance of gel valve-regulated lead-acid (gel VRLA) batteries. In this study, the influence of the concentration of fumed silica and four additives in the gel electrolyte formulation on the gelling process, electrochemical behavior and battery performance was investigated. Higher fumed silica concentrations and the presence of polyacrylamide and vaniline led to a shorter gelling time and a firmer gel. Of the gel formulations studied, gel VRLA batteries with or without 0.005% (w/v) vaniline had a higher discharge capacity than the conventional liquid VRLA battery.

Preparation of hollow ZSM-5 crystals in the presence of polyacrylamide

Hollow ZSM-5 crystals were successfully synthesized through a simple one-step hydrothermal crystallization method in the presence of polyacrylamide (PAM) as template. The influences of crystallization temperature, PAM concentration, and the type of PAM on the morphology and pore structure of hollow ZSM-5 zeolite as well as the stability and formation mechanism of hollow structure were investigated. Hollow ZSM-5 crystals could be synthesized by adding three types of PAM with different surface groups. Crystallization temperature and PAM concentration played crucial roles in the formation of hollow ZSM-5 crystals. Low crystallization temperature or high PAM concentration was beneficial for the formation of hollow ZSM-5 crystals with embedded large voids in the framework structure. Egg-shell like hollow ZSM-5 crystals formed with less amount of PAM at high temperature due to the decomposition of the PAM network. Moreover, the surface walls of those hollow ZSM-5 crystals possessed microporous crystalline framework. Hollow ZSM-5 crystals exhibited good thermal and hydrothermal stability, and anti-pressure ability. ZSM-5 crystallization in the presence of PAM was in good agreement with the surface-to-core crystallization process. The fast growth of ZSM-5 nuclei on the surfaces of PAM hydrogel resulted in the formation of single crystals with hollow structure after they consumed the synthesis gel and ZSM-5 nuclei in the PAM hydrogel network.

Investigation of the stability of an alumina suspension in the presence of ionic polyacrylamide

The influence of solution pH on the adsorption mechanism of polyacrylamide (PAM) on the alumina surface and stability of its suspension in the presence of polymer were investigated. The structure of polymer adsorption layer was determined from the spectrophotometric, viscosity, surface charge and zeta potential measurements which enable determination of adsorbed amount of polymer, thickness of the polymer adsorption layer, surface charge density and zeta potential of Al2O3 particles in the absence and presence of PAM. The measurements of stability of alumina suspension without and with adsorbed polyacrylamide were also carried out using two methods: spectrophotometry and turbidimetry. The obtained results indicate that solution pH influences the structure of PAM adsorption layer (decrease of adsorbed amounts of polymer and increase of its adsorption layer thickness with the increasing pH). These conformational changes of polyacrylamide molecules with the rising pH have an impact on stability of the alumina suspension. The most pronounced effect of polymer on the stabilization properties of investigated systems is observed for PAM addition at pH 6 resulting in a great destabilization of the alumina particles by bridging flocculation.

The temperature effect on the adsorption mechanism of polyacrylamide on the silica surface and its stability

The influence of temperature on the adsorption mechanism of polyacrylamide (PAM) on the silica surface was studied in the temperature range 15–35°C. The structure of polymer adsorption layer was determined from spectrophotometric, viscosity, surface charge and zeta potential measurements. These methods enable determination of the following parameters: adsorbed amount of polymer, macromolecules conformation in the solution and thickness of the polymer adsorption layer, surface charge density and zeta potential of SiO2 particles in the absence and presence of PAM. The measurements of stability of silica suspension without and with adsorbed polyacrylamide were also carried out. The obtained results indicate that temperature influences the conformation of PVA chains in the solution and the structure of polymer adsorption layer. The temperature rise causes polymer coils developing which results in: the decrease of polymer adsorption, the increase of linear dimensions of PAM chains in the solution, the creation of thicker adsorption layer of the polymer on the solid surface and the slight lowering of zeta potential of solid particles. Taking into account the conformational changes of polymer chains with the increasing temperature main reasons responsible for stability of the investigated system were given.

Worm-Like Palladium/Carbon Core−Shell Nanocomposites: One-Step Hydrothermal Reduction−Carbonization Synthesis and Electrocatalytic Activity

Worm-like palladium/carbon (Pd/C) core−shell nanocomposites have been hydrothermally prepared starting from PdCl2 and α-lactose monohydrate (α-LM) in the presence of polyacrylamide (PAM) at 200 °C. The thickness of carbonaceous shells varied from 5 to 45 nm with increasing temperature from 140 to 200 °C. When the dose of PAM or PdCl2 was increased, spherical Pd/C core−shell nanocomposites were obtained. Time-dependent experiments confirmed that formation of Pd/C core−shell nanocomposites underwent an entrapment−reduction−carbonization process. Such a route has also been extended to synthesize spherical Ag/C core−shell composites. A cyclic voltammetry (CV) study reveals that the as-prepared Pd/C core−shell nanocomposites exhibit electrocatalytic activity toward oxidation of ascorbic acid (AA).

Solution-phase synthesis of nanomaterials at low temperature

This paper reviews the solution-phase synthesis of nanoparticles via some routes at low temperatures, such as room temperature route, wave-assisted synthesis (γ-irradiation route and sonochemical route), directly heating at low temperatures, and hydrothermal/solvothermal methods. A number of strategies were developed to control the shape, the size, as well as the dispersion of nanostructures. Using diethylamine or n-butylamine as solvent, semiconductor nanorods were yielded. By the hydrothermal treatment of amorphous colloids, Bi2S3 nanorods and Se nanowires were obtained. CdS nanowires were prepared in the presence of polyacrylamide. ZnS nanowires were obtained using liquid crystal. The polymer poly (vinyl acetate) tubule acted as both nanoreactor and template for the CdSe nanowire growth. Assisted by the surfactant of sodium dodecyl benzenesulfonate (SDBS), nickel nanobelts were synthesized. In addition, Ag nanowires, Te nanotubes and ZnO nanorod arrays could be prepared without adding any additives or templates.

Impact of polyacrylamide on surface properties of solutions of chlorides of alkylpyridinium during their removal

It has been shown that in diluted aqueous solutions of alkylpyridinium chlorides (APC) containing polyacrylamide (PAA) one can detect synergism of their effect on surface tension. Maximum manifestation of synergism in the course of adsorption of components occurs at their molar ratio nAPC: nPAA—1: 0.25. By design values of the minimal area falling at the COD-PAA particles in surface layers a pattern of the structure of mixed layers at the boundary with air depending on the ratio of the components and the length of the COD hydrocarbon radical is proposed. It was found that the process of COD floatation removal is advisable to be carried out in weakly acid, neutral, and weakly alkaline media in the presence of PAA at the indicated molar ratio.

A Practical Method for Synthesis of Stable Phosphorus Ylides in the Presence of Polyacrylamide in Aqueous Media

Stable crystalline phosphorus ylides were obtained in good to excellent yields from the 1:1:1 addition reaction between triphenylphosphine, dialkyl acetylenedicarboxylates and β -dicarbonyl or heterocyclic compounds such as, diethyl malonate, acetyl acetone, 1, 3-dimethylbarbituric acid, meldrum's acid, 2-benzoxazolinone, pyrrole-2-carboxaldehyde, benzotriazole, 5-methyl benzotriazole, and 5-chloro benzotriazole, in the presence of polyacrylamide in water. The green and mild reaction conditions, medium to short reaction time, low cost, ready preparation are the main advantages of this method.

Polymer‐acid solutions: Their use for the enhancement of oil reservoir stimulation

AbstractA reduction in permeability occurring around the wellbore resulting from drilling, completion and/or workover fluids increases the flow resistance to the petroleum reservoir fluids and is defined as formation damage. Acidizing process removes near‐wellbore damage and enhances hydrocarbon production from producing wells. This study investigates the effect of adding polymer as a retarding agent to acid solutions to slow and control the reaction in matrix acidizing treatment of carbonate rocks. Two different polymers, polyacrylamide (PAA) and polysaccharide (xanthan) and two different acids, acetic acid and formic acid, were used through this study. The results revealed that the presence of PAA did not change the viscosity of the acid solution significantly, while the viscosity of xanthan‐acid solutions was decreased with increasing the acid concentration. Additionally, the reaction of polymer‐acid solutions with the rock material was monitored under microscope. Original rock samples obtained from Saudi reservoirs containing mainly carbonate were used in the reaction. The PAA‐acid solution did not show any decrease in the reaction rate compared to that of acid solution. Thus, the PAA solution applied in this study is not recommended as a retarder. However, xanthan‐acid solutions showed a significant decrease in the reaction time. Therefore, xanthan was selected to perform further investigations in Rotating Disk Reactor at different pressures. Scanning electronic microscopy (SEM) was conducted on pretreated and posttreated rock samples. This provides the opportunity to perform a detailed description of the rock surface and facilitates the identification of the changes occurring due to polymer‐acid treatment. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008

Iron ore flotation in the presence of polyacrylamides

Flotation is an important process used in the concentration of iron ores. One of the challenges for process engineers is the low metallurgical recovery associated mainly with the fines fraction. In this work, the use of synthetic flocculants in iron ore reverse cationic flotation was investigated. The flocculants utilised were polyacrylamides of high molecular weight and different ionic degrees. Bench scale flotation tests were performed to compare the flotation performance with and without addition of polyacrylamides. It was observed that cationic and non-ionic polyacrylamides cause a significant increase in the metallurgical recovery. The anionic flocculant did not improve the flotation performance. An adverse effect was a slight increase in the silica content of the concentrate. Flotation with polyacrylamides was influenced by the hydrodynamic conditions of the pulp, such as agitation and the weight percentage of solids in the flocculant conditioning and flotation stages.

Molecular dynamics simulation of polyacrylamides in potassium montmorillonite clay hydrates

We present molecular dynamics simulation results for polyacrylamide in potassium montmorillonite clay–aqueous systems. Interlayer molecular structure and dynamics properties are investigated. The number density profile, radial distribution function, root-mean-square deviation (RMSD), mean-square displacement (MSD) and diffusion coefficient are reported. The calculations are conducted in constant NVT ensembles, at T = 300 K and with layer spacing of 40 Å. Our simulation results showed that polyacrylamides had little impact on the structure of interlayer water. Density profiles and radial distribution function indicated that hydration shells were formed. In the presence of polyacrylamides more potassium counterions move close to the clay surface while water molecules move away, indicating that potassium counterions are hydrated to a lesser extent than the system in which no polyacrylamides were added. The diffusion coefficients for potassium and water decreased when polyacrylamides were added.

The effect of water-soluble polymers on the stability and rheological properties of suspensions of fibrous activated charcoal

The stability and rheological characteristics of polymer-containing aqueous suspensions of fibrous activated charcoal are determined. It is shown that the improved stability of suspensions is observed in the presence of carboxymethyl cellulose, oxypropyl methyl cellulose, polyvinylpyrrolidone, and a new water-soluble cellulose derivative, whereas the presence of polyacrylamide, poly(acrylic acid), poly(vinyl alcohol), and starch leads to the formation of unstable suspensions having a broad particle size distribution. A correlation between the concentration of dispersed-phase particles corresponding to the transition to non-Newtonian flow and the characteristics of suspension stability (such as the rate of sedimentation, the volume of the sediment, and the particle size distribution) is established. It is suggested that the high degree of charcoal particle surface hydrophilization by polyvinylpyrrolidone and by the water-soluble cellulose derivative is mainly responsible for the stability of the modified suspensions.

The effect of polyacrylamide on the crystallization of calcium carbonate: Synthesis of aragonite single-crystal nanorods and hollow vatarite hexagons

CaCO 3 nanorods were synthesized via a facile solution route by polymer-controlled crystallization in the presence of polyacrylamide (PAM). The morphology, size and crystal structure were characterized by means of scanning electron microscope (SEM), transmission electron microscope (TEM), and X-ray diffraction (XRD). The results suggest that the as-synthesized product was CaCO 3 (aragonite) nanorods with diameter ca. 50 nm and length ca. 1 μm. Selected area electron diffraction (SAED) pattern shows the single-crystal nature of CaCO 3 nanorods. The reaction time, temperature, pH and reactant concentration were systemically investigated. With the increase in the reaction time, hollow vaterite hexagonal disks can be obtained.

Physico‐Chemical Studies on Cu(II) Complexes of Acrylate Chelating Polymers

Metal chelating polymers containing amide and carboxylic groups were prepared by gamma‐radiation polymerization of acrylic acid (AA) monomers in the presence of polyacrylamide (PAM). The resins obtained were loaded by copper ions and characterized by FT‐IR spectroscopy, electron spin resonance (ESR), thermogravimetric analysis (TGA), and differential scanning calorimetery (DSC). The IR spectra indicated a lower frequencies shift in the carbonyl bands due to copper ion chelation with carbonyl groups in the polymer resins. Also, the IR spectra reveal a splitting in the band at 3600–3200 cm−1 that due to the coordination of the NH and OH groups with copper ions. The ESR spectrum was anisotropic with hyperfine structure having the following values 2.3808 and 2.07218 for g ∥ and g ⊥, respectively. These spectra for copper ions have square planar coordination with two nitrogen and two oxygen atoms. TGA and DSC studies show that radiation crosslinking and complexation with copper ion increase the thermal stability of PAM–AA resins. Meanwhile, resin complexes with copper ion showed a higher thermal stability than pure resin. The increase in thermal stability may be correlated with the metal ions coordination with NH and OH groups; this coordination prevents the splitting of ammonia and water molecules. Also, the metal ions providing a coordination crosslink between polymer chains could increase thermal stability.

Mechanochemical synthesis of Co, Ni, Fe nanoparticles in polymer matrices

We report on synthesis of Co, Ni, and Fe nanoparticles by the action of elastic wave pulses on solid phase sandwich type samples containing metal salt, reducing agent, polyethylene, and polyacrylamide. The formation of metal nanoparticles is evidenced by ferromagnetic resonance and scanning electron microscopy. The product yield for the nanoparticles formation has a threshold character with the pressure in the elastic wave pulse. The maximum amount of Co, Ni, and Fe nanoparticles is observed around 20 kbar of pressure in elastic wave pulses. The presence of polyacrylamide in reaction composites increases the stability of metal nanoparticles to oxidation by two orders of magnitude.

Study of the CaSO 4 deposits in the presence of scale inhibitors

The water state in the CaSO 4 solutions where concentrations ranged from 0.68–7.08 g/l was studied by the differential-scanning calorimetry. In the low-temperature range, 248.8 K, a peak was detected at the beginning of a CaSO 4 concentration of 1.7 g/l. Its appearance could be attributed to an initial moment of the crystallization, that is, a formation of the CaSO 4 nuclei. The resulting increase in the CaSO 4 concentration (up to 4.7 g/l) promotes a growth of the low-temperature peak. The effect of the inhibitors on the water state in the CaSO 4-containing solutions was examined to clarify the role played by these potential scalants. Solutes of different chemical natures were used as inhibitors. As the thermograms demonstrated, an addition of the inhibitors into the system tested did not influence the formation of the CaSO 4 nuclei but it precluded the resulting growth of crystals. An increase in concentration of the inhibitors results in a decrease of low-temperature peak. This testifies to the slowing down of the formation process of the CaSO 4 nuclei. Better results were established by the presence of polyacrylamide and carboxymethyl cellulose while those with the presence of PE-1 polyelectrolyte were somewhat worse. The use of polyacrylamide as an inhibitor has been shown to increase the retentivity of the OPAM-KN membrane up to 0.90.