Adsorption Of Polyacrylate Research Articles

Performance improvement of chemical enhanced oil recovery by divalent ion–complexing agents

The performance of chemicals used in chemical enhanced oil recovery (EOR) is sensitive to the local ionic environment. Divalent ions are in particular known to reduce polymer solution viscosity and mediate the adsorption of surfactants and polymers to the rock surface. Here, we study whether the addition of divalent ion–complexing agents can mitigate these interactions and thus improve the performance of EOR chemicals. The addition of sodium polyacrylate (NaPA) is found to be highly effective in reducing surfactant adsorption and increasing polymer viscosity. The reduction in surfactant adsorption is attributed to a combination of divalent ion complexation and the adsorption of polyacrylate to the rock surface. The increase in polymer viscosity is also attributed to complexation of divalent ions that would otherwise interact with the polymer. Polymer flooding experiments in a limestone core show that the addition of NaPA also significantly enhances solution injectivity and propagation, thus providing a host of benefits to chemical EOR performance.

Reducing anionic surfactant adsorption using polyacrylate as sacrificial agent investigated by QCM-D

Surfactant losses by adsorption to rock surfaces make surfactant-based enhanced oil recovery economically less feasible. We investigated polyacrylate (PA) as a sacrificial agent in the reduction of anionic surfactant adsorption with focus on calcite surfaces by using quartz crystal microbalance with dissipation monitoring. It was found that the adsorption of the anionic surfactant alcohol alkoxy sulfate (AAS) followed a Langmuir adsorption isotherm, and the adsorbed amount reached saturation above its critical micellar concentration. Adsorption of PA was a much slower process compared to AAS adsorption. Increasing the calcium ion concentration also increased the amount of AAS adsorbed as well as the mass increase rate of PA adsorption. Experimental results combined with density functional theory calculations indicated that calcium cation bridging was important for anionic surfactant AAS and PA adsorption to calcite surfaces. To effectively reduce the amount of surfactant adsorption, it was needed to preflush with PA, rather than by a simultaneous injection. Preflushing with 30 ppm of PA gave a reduction of AAS adsorption of 30% under high salinity (HS, 31,800 ppm) conditions, compared to 8% reduction under low salinity (LS, 3180 ppm) conditions. In the absence of PA, the amount of adsorbed AAS was reduced by already 50% upon changing from HS to LS conditions. Lower calcium ion concentrations, as under LS conditions, contributed to this observation. On different mineral surfaces, PA reduced the AAS adsorption in the order of alumina > calcite > silica. These results offer important insights into mitigating surfactant adsorption using PA polyelectrolyte as sacrificial agent and contribute to improved flooding strategies with reduced surfactant loss.

Removal of polyacrylate in aqueous solution by activated sludge: Characteristics and mechanisms

Abstract The aim of this study is to evaluate the removal potential of polyacrylate in aqueous solution by activated sludge. Batch experiments investigated the effects of contact time, pH value, temperature, and concentration of adsorbate on polyacrylate removal by activated sludge to evaluate the isotherms, kinetics, thermodynamics, and mechanisms. The materials were characterized by N2 adsorption-desorption isotherms, scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), and Fourier transform infrared spectroscopy (FT-IR). The experimental results indicate that more than 90% of polyacrylate was removed by activated sludge in a short time. The adsorption capacity increase with the increase in initial polyacrylate concentration and temperature. Increasing pH value resulted in a decrease in adsorption capacity. The adsorption process fitted well to Langmuir isotherm and pseudo-second-order kinetic models. Thermodynamic parameters indicate that the adsorption of polyacrylate onto activated sludge was feasible, spontaneous, and endothermic. The results of kinetics, thermodynamics, SEM-EDS, and FT-IR showed that surface binding, hydrophobic interaction, and hydrogen bond force may play a major role in the removal process. Microbial community structure analysis by 16S rRNA gene revealed that short-term exposure with polyacrylate had a little negative impact on the activated sludge microorganisms. A better understanding of polyacrylate adsorption onto activated sludge is essential for improving predictions of the fate and transport of polyacrylate in waste water treatment process.

Layered double hydroxide nanoparticles customization by polyelectrolyte adsorption: mechanism and effect on particle aggregation

Adsorption of polyelectrolytes (PEs) is a common strategy for stabilizing nanoparticles and customizing their properties. Although scarcely explored for layered double hydroxide nanoparticles (LDH-NPs), it can be used to increase their functionality in pharmaceutical and biomedical applications, among others. In this work, LDH-NPs intercalated with chloride, ibuprofen and ketoprofen were synthesized and modified with carboxylate containing PEs with different structures and physicochemical properties. The PEs adsorption mechanism on LDH-NPs and its effect on the aggregation of the obtained hybrids were studied by zeta potential and hydrodynamic diameter determinations on chloride intercalated LDH-NPs dispersions in the presence of polyacrylate (PA) at different concentrations. PA adsorption behavior was compared to that of citrate anion to contrast the adsorption mechanism of PEs and anions. Afterwards, the study was extended to other PEs (alginate and carbomer) as well as to drug intercalated LDH-NPs. PA adsorbed at the surface of LDH-NPs with high affinity: at low concentrations, PA was irreversibly adsorbed due to the positive structural charge of LDH-NPs and the flexible and negatively charged structure of PA. This high affinity caused a particle charge inversion, which results in negatively charged LDH-NPs stabilized by both electrostatic interactions and steric hindrance. Due to their structure, alginate and carbomer showed a lower affinity and, consequently, a lower capacity to produce LDH-NPs disaggregation. Finally, PEs adsorption allowed enhancing the disaggregation and modifying the interfacial properties of both ibuprofen and ketoprofen intercalated LDH-NPs producing only a small release of the drug loading.

Reducing adsorption of anionic surfactant for enhanced oil recovery: Part I. Competitive adsorption mechanism

Although injection of surfactants in oil reservoirs often can lead to production of more oil, loss of surfactant due to adsorption on porous media can make this process economically unfeasible. In this work, we examine the adsorption of an anionic surfactant blend and sodium polyacrylate on dolomite and demonstrate that, under certain conditions, the sodium polyacrylate adsorbs preferentially and inhibits the adsorption of surfactant. The addition of sodium polyacrylate significantly reduces the amount of surfactant adsorption above a critical polyacrylate molecular weight. On the other hand, presence of anionic surfactant has no significant effect on the adsorption of polyacrylate. We also demonstrate high concentrations of anhydrite acts against preferential adsorption of sodium polyacrylate.This study demonstrates that polyacrylate molecular weight and concentration as well as polyacrylate-to-anhydrite molar ratio are key variables governing the competitive adsorption of anionic surfactant and polyacrylate, which are interpreted by negligible desorption and high surface coverage of polyacrylate.

The effect of polymer adsorption on the wetting properties of partially hydrophobized magnetite

Upon reverse flotation of iron ore, the surface of the iron ore concentrate may become partially hydrophobized due to adsorption of flotation collector, which is facilitated by the calcium ions present in the process water. Hydrophobic areas on the concentrate surface may introduce problems in subsequent pelletization of the concentrate. A possible way to restore the wettability of the surface could be by modifying the surface with a hydrophilic polymer. The effect of hydrophilic polymers of different types, viz. cationic, anionic, and non-ionic, on the wettability of the magnetite surface after adsorption of a surfactant was investigated. Although all the polymers could adsorb on magnetite at pH 8.5, the contact angle measurements revealed that only anionic ammonium polyacrylate could decrease the contact angle of synthetic magnetite after surfactant adsorption to a level close to that of as-synthesized magnetite. Such effect was probably achieved due to shielding of the hydrophobic surfactant chains from the aqueous phase by hydrophilic polyacrylate molecules. The fact that polyacrylate adsorption on magnetite occurred via calcium ions makes polyacrylate suitable for application in calcium-rich process water. The results presented in this work illustrate that ammonium polyacrylate could be successfully used to improve the wettability of magnetite after adsorption of surfactants.

Pancytopenia with severe thrombocytopenia in a patient treated with twice‐weekly LDL‐apheresis by polyacrylate adsorption from whole blood

Pancytopenia with severe thrombocytopenia occurred in a patient treated with low-density lipoprotein (LDL)-apheresis by polyacrylate adsorption from whole blood, after treatment frequency had been increased from once to twice a week. Cell counts recovered with discontinuation of LDL-apheresis, but thrombocytopenia recurred after resumption of twice-weekly treatments. Thrombocyte counts remained stable following the replacement of polyacrylate adsorption from whole blood by double-filtration plasmapheresis. The complications' close coincidence with twice-weekly polyacrylate adsorption from whole blood suggests a causal relationship, although by a still unknown mechanism. Monitoring of thrombocytes should be advised in patients treated with LDL-apheresis by polyacrylate adsorption from whole blood.

Dextran‐sulfate‐adsorption of atherosclerotic lipoproteins from whole blood or separated plasma for lipid‐apheresis—Comparison of performance characteristics with DALI and lipidfiltration

For many years dextran sulfate adsorption (DSA) treatment of separated plasma has been an established technology for low-density lipoprotein (LDL)-elimination. Recently a system for the treatment of whole blood based on DSA was introduced into clinical practice. To further characterize DSA treatment of whole blood, the performance characteristics of both DSA modalities were compared at two investigational sites with two alternative LDL apheresis systems being already in routine clinical use. In prospective cross-over design, DSA whole blood treatment was compared with a whole blood polyacrylate LDL adsorption system (DALI) in one study group. DSA for plasma treatment was compared with Lipidfiltration in cross-over design in a second study group. In total, 12 patients on chronic LDL apheresis received 169 treatments. Six patients were treated twice with whole blood polyacrylate adsorption and twice with whole blood DSA. LDL-cholesterol (74.9-78.0%) and lipoprotein (a) (72.1-73.3%) were reduced by both with equal efficacy. DSA achieved a significantly higher reduction rate of fibrinogen. Another six patients were treated eight times with DSA plasma adsorption followed by 16 Lipidfiltration treatments. LDL-cholesterol (67.0-70.2%) and lipoprotein (a) (69.2-73.7%) were reduced by both with equal efficacy. Fibrinogen was eliminated more efficiently by Lipidfiltration (50.2 vs. 38.5%). DSA proved to be a safe and effective in both treatment modes, for plasma as well as for whole blood. At the discretion of the apheresis specialist, depending upon the status of national approval, DSA of whole blood complements the armamentarium of powerful modalities for extracorporeal elimination of atherosclerotic lipoproteins to meet specific individual, medical, or logistic needs.

Sodium Polyacrylate Adsorption onto Anionic and Cationic Silica in the Presence of Salts

Sodium polyacrylate is well known for its application as a scale inhibitor in common household products, and the effects of both monovalent and divalent metal cations on its structure have been covered by a range of previous publications. In the present article, we extend this work by using solvent relaxation NMR to look at the adsorption of the polyelectrolyte onto both positively and negatively charged silica and how this is altered by calcium chloride. In the anionic case, we found that polyacrylate adsorption was predictably very weak, and interestingly, perhaps counterintuitively, it was further reduced by calcium ions. This is probably linked to NaPA-Ca2+ binding, which changes the conformation and charge of the polyelectrolyte. In contrast, NaPA adsorbs very strongly on cationic silica, to the point that precipitation often occurs, particularly on addition of salt.

An in Situ FTIR-ATR Study of Polyacrylate Adsorbed onto Hematite at High pH and High Ionic Strength

FTIR-ATR was used to examine in situ the interaction of polyacrylate and hematite at pH 13. Static light scattering and mobility measurements were used to assess solution polyacrylate dimensions and hematite surface charge, respectively. Polyacrylate adsorption occurred only with the addition of electrolyte (e.g., NaCl), and it was found that excess cations, up to approximately 1 M, facilitated adsorption, above which the effect was found to plateau. At pH 13 and at low ionic strength, adsorption of polyacrylate onto hematite is facilitated by cations in solution shielding both the negative acrylate functionality of the polymer and the negative hematite surface. The shielding of the hematite surface continues to increase with increasing salt concentration up to a measured 3 M. Similarly, the shielding of the polymer increased with electrolyte concentration up to approximately 1 M salt, beyond which no further increase in shielding was observed. At this concentration the polymer assumes a finite minimum size in solution that ultimately limits the amount adsorbed. The dimension of the polymer in solution was found to be independent of monovalent cation type. Thus, at high pH and high ionic strength adsorption is determined by the degree of hematite surface charge reduction. The cation-hematite surface interaction was found to be specific, with lithium leading to greater polyacrylate adsorption than sodium, which was followed by cesium. The stronger affinity of lithium for the hematite surface over sodium and cesium is indicative of the inverse lyotropic adsorption series and has been rationalized in the past by the "structure-making-structure-breaking" model. These results provide a useful insight into the likely adsorption mechanism for polyacrylate flocculants at high pH and ionic strength onto residues in the Bayer processing of bauxite.

Ammonium polyacrylate adsorption on “aluminium hydroxides and oxyhydroxide” coated silicon nitride powders

Si 3N 4 powders coated with pseudoboehmite, Al hydroxide with a OH/Al mol ratio ( R) lower than 3 and bayerite, were prepared from different coating solutions and dispersed in water with an ammonium polyacrylate (NH 4PA) to produce 11.8 vol% slips. The coated powders showed isoelectric points at pH 7, 7.5 and 7.5 close to that of the precipitate coatings of pseudoboehmite, Al hydroxide ( R<3) and bayerite, respectively, indicating that the surface coverages were almost complete. The bayerite coated powders had the lowest specific surface area values. The coatings on Si 3N 4 particles were shown to improve the adsorption of NH 4PA dispersant on Si 3N 4. The maximum adsorption of the polyelectrolyte at pH 9.5 increased from 0.01 for the uncoated powder to 0.03, 0.055 and 0.08 mg/m 2 for the coated powders with pseudoboehmite, Al hydroxide ( R<3) and bayerite, respectively.

Improvement of ammonium polyacrylate adsorption on Si 3N 4 powders by an aluminium hydroxide coating

A precipitate coating Al(OH) 3 on Si 3N 4 particles was shown to improve the adsorption of ammonium polyacrylate (NH 4PA) dispersant on Si 3N 4. The coating of Al(OH) 3 on Si 3N 4 particles resulted in a bayerite-like surface with a small amount of gibbsite-like structure which improved the adsorption of a NH 4PA dispersant. The maximum adsorption at pH 9.5 increased from 0.01 to 0.075 mg/m 2 for the as-received and coated Si 3N 4 powders, respectively.

Infrared spectral investigation of polyacrylate adsorption on alumina

Diffuse reflectance infrared Fourier transform spectroscopy was used to investigate the structural nature of polyacrylates adsorbed on alumina from aqueous solution. The presence of sodium bicarbonate or sodium ions on the alumina surface could inhibit the carboxylate groups on the polymer chains from forming covalent bonds with aluminium ions on the surface. More carboxylate groups of the chains were adsorbed on surface sites at lower polymer concentration and higher pH. Also, an increased loop formation of the polyacrylate chains occurred with a decrease in treatment of pH and an increase in polymer concentration. When the pH changed from higher to lower values in steps, the adsorbed polymer did not increase as much from the stretched-out form to the coiled form as was noted if one initially only treated the aqueous polyacrylate/alumina slurry at the lower pH. The adsorption of water on the polyacrylate-treated surface changed the ratio between covalently and ionically bonded carboxylate groups, causing more ionically bonded species.

Transient adsorption of a tri(ethyleneglycol) polyacrylate on a plasmapheresis membrane

We study the adsorption of polyacrylate of tri(ethyleneglycol) in water on a plasmapheresis membrane, whose main constituent is a copolymer of acrylonitrile and methylmethacrylate. The amount of adsorbed polymer has a strong dependence on pH. Adsorbance is high at low pH and very low at high pH, while in the intermediate range the interfacial concentration Γ is not a monotonic function of the solution concentrationC. Viscosimetry andUV adsorbance measurements in solution suggest the existence of plurimolecular structures, aggregates, or micelles. We propose a kinetic model, where these latter objects act as detergents at highC and, therefore, contribute to decreasing the interfacial concentration Γ when increasingC.

Adsorption of polyacrylate and carboxy methyl cellulose on kaolinite: Salt effects and competitive adsorption

The adsorption of sodium polyacrylate (NaPAA) and sodium carboxy methyl cellulose (NaCMC) on homoionic sodium and calcium kaolinite has been investigated. Adsorption is strongly dependent on Ca 2+ /polyelectrolyte interactions in solution, while the nature of the kaolinite is of less importance. Adsorption takes place on two types of sites where the energetically more favorable sites appear to be the edges and the other sites are the basal planes. On addition of Ca 2+ to a PAA solution, a maximum binding (saturation) corresponding to 0.306 Ca 2+ /PAA segment is reached. An adsorption model has been developed in which it is assumed that while any PAA may be adsorbed on the more favorable sites, only PAA molecules that are saturated with Ca 2+ adsorb on the other sites. Equilibrium calculations using apparent binding constants of Ca 2+ to the PAA determined from potentiometric titration show that this model is able to predict the experimentally determined isotherms with good accuracy. Although detailed calculations have not been performed, the model appears to be applicable also to the adsorption of NaCMC.

Exchange and competitive adsorption of polyelectrolytes on barium sulphate

The desorption of polyelectrolyte molecules adsorbed on barium sulphate in the presence of various displacing species is reported. When polyacrylate (PAA) was both the adsorbed and displacing species, no significant desorption occurred when the dispersion medium was water. However, significant desorption occurred in 0.1 mol dm −3 NaCl, but only when the displacing PAA had a higher molecular mass than that adsorbed. The simultaneous adsorption of PAA and polystyrene sulphonate (PSS) is also reported as a function of the molecular mass of the two species and at different relative concentrations. The adsorption of PAA decreased with increase in the ratio of the weight of barium sulphate to the volume of polymer solution ( W/V), whilst that of PSS increased. In H 2O there was a critical W/V ratio below which there was no detectable adsorption of PSS. The amount of PSS excluded from the surface increased as the ratio of PAA to PSS concentrations increased. The results indicate that the diffusion rate of PAA is the dominating factor in determining the surface composition. This suggests that the PSS must require a significant time from first contact of the molecule to complete adsorption, and in this time, newly arriving PAA molecules displace the PSS.

Adsorption of Organic Diacids and Sodium Polyacrylate Onto Montmorillonite

AbstractOrganic diacid (oxalic and succinic) adsorption onto montmorillonite is feasible, but weak (~1 mg/g). The comparison of chemical and radiochemical determinations reveals that 80% of the acid in contact with the smectite is used to attack the clay lattice. The pH is the main parameter involved in adsorption, and fixation passes through a minimum for pH 6 to 7. Polyacrylate adsorption is also weak (~1.5 mg/g). It changes with the nature of the exchangeable cation of smectite. Its pH-dependence displays a pronounced maximum for a value corresponding to the pKa of the acidic functions (pH ~6.8), and a minimum at about pH 8. On the assumption that a polyacrylate macromolecule is 100% hydrolyzed, it follows that the-COOH groups carried by 20% hydrolyzed Polyacrylamide molecules (such as those used in the tertiary recovery of petroleum) contribute at the very most to 10% of the total adsorption onto clay. Fixation, therefore, involves predominantly protonation of the amide functions at the edge surfaces of the clay. The acidic functions play a minor role in the adsorption phenomenon in that they affect the length of the macromolecule. The extent of this contribution, however, is virtually impossible to estimate.