Anionic Charge Density Research Articles

Effect of PCE anionic charge density on fly ash cementitious system-PCE compatibility

In this study, the compatibility of polycarboxylate-based water-reducing admixtures (PCEs) with cementitious systems containing fly ash (FA) was investigated. For this purpose, PCEs with carboxylate, phosphate, and sulfonate anionic groups having different anionic charge densities were synthesized. The effects of PCEs on fresh properties and compressive strength of cementitious systems containing FA were investigated. The PCE with 9% phosphate substitution and high anionic charge density was found to be the most effective, requiring the least amount for the target flow. Similarly, in terms of the PCE requirement for the minimum Marsh funnel flow time and rheological parameters, the best performance was obtained with 5% sulfonate substituted PCE having high anionic charge density. While FA had a positive effect on the PCE requirement and consistency retention of the mixtures; it had a negative effect on Marsh funnel flow time, rheological properties, and compressive strength. However, the rheological properties of the mortar mixtures were not adversely affected by the FA substitution as much as that of the paste mixtures. Regarding the 28-day compressive strength of mortar mixtures, the optimum FA substitution ratio was 15%. Fly ash substitution above this level reduced the compressive strength at all ages including 28-day strength. Anionic charge density variation of PCE had no significant influence on the compressive strength of the mortars.

Synthesis, performance and mechanism of shrinkage-reducing agents with water-reducing function for cement-based materials

Three shrinkage-reducing agents (SRAs) possessing a water-reducing capacity with different structures were synthesized by aqueous free radical copolymerization. Their structures were characterized by Gel Permeation Chromatography (GPC), specific anion charge density, and Fourier Transform Infrared Spectrometer (FTIR) measurements. Their abilities to reduce surface tension and their adsorption and dispersing effectiveness in cement paste as well as their impacts on cement hydration and compressive strength, autogenous shrinkage, drying shrinkage, and pore structure of cement mortar were investigated. Results clearly showed that the three synthesized SRAs with a water-reducing function reduced the surface tension of pore solution, with the water-reducing SRA with butyl exerting the most significant effect due to its lower molecular mass. They enhanced the flowability of cement paste because of their adsorption on cement grains. The water-reducing SRA with dimethyl amino exhibited higher adsorption amounts on cement grains due to higher charge density, resulting in higher initial flowability of cement paste and more significant hydration retardation. Their presence decreased the autogenous shrinkage of cement mortar by reducing the surface tension of pore solution, delaying the cement hydration, and decreasing the capillary pore volume. Their addition also mitigated the drying shrinkage due to the synergistic effect of surface tension reduction, pore structure coarsening, and porosity (2.5–50 nm) reduction. Among the three, the water-reducing SRA with butyl demonstrated a higher capability of reducing the drying shrinkage and had a favorable effect on the compressive strength of mortar at later ages.

Influence of Anion Species on Liquid-Liquid Phase Separation in [EMIm+][X-]/Benzene Mixtures.

When a molar excess of benzene is mixed with an ionic liquid (IL), liquid-liquid phase separation may appear with a pure liquid phase almost composed of only benzene molecules separated from a liquid clathrate phase with benzene molecules dissolved in the IL. Our previous study (J. Phys. Chem. B, 124, 7929, 2020) on long-chain IL/benzene systems has concluded that benzene molecules, as planar nonpolar ones, majorly dissolve in the IL nonpolar domains consisting of cationic alkyl side chains. Nevertheless, the above mechanism is inadequate for explaining the experimental observations that benzene can also dissolve in IL systems with very short alkyl side chains. In this study, by molecular dynamics simulation of the [EMIm+][X-]/benzene mixtures with X- being Cl-, NO3-, PF6-, or Tf2N-, we still observe liquid-liquid phase separation of the pure benzene phase from a liquid clathrate (mixed IL/benzene) phase where benzene molecules are almost equally distributed near imidazolium rings through π-stacking or near alkyl side chains. The anion species strongly influences the solubility of benzene and the ratio of the two liquid phases via the alteration of anionic charge density, which tunes the strength of the electrostatic interaction among ions and thus the probability of benzene molecules interacting with both imidazolium rings and alkyl side chains: a larger anionic charge density corresponds to a lower solubility of benzene.

Accumulation mechanisms for contaminants on weak-base hybrid ion exchange resins

Mechanism of hexavalent chromium removal (Cr(VI) as CrO42-) by the weak-base ion exchange (IX) resin ResinTech® SIR-700-HP (SIR-700) from simulated groundwater is assessed in the presence of radioactive contaminants iodine-129 (as IO3-), uranium (U as uranyl UO22+), and technetium-99 (as TcO4-), and common environmental anions sulfate (SO42-) and chloride (Cl-). Batch tests using the acid sulfate form of SIR-700 demonstrated Cr(VI) and U(VI) removal exceeded 97%, except in the presence of high SO42- concentrations (536 mg/L) where Cr(VI) and U(VI) removal decreased to ≥ 80%. However, Cr(VI) removal notably improved with co-mingled U(VI) that complexes with SO42- at the protonated amine sites. These U–SO42- complexes are integral to U(VI) removal, as confirmed by the decrease in U(VI) removal (<40%) when the acid chloride form of SIR-700 was used instead. Solid phase characterization revealed that CrO42- is removed by IX with SO42- complexes and/or reduced to amorphous Cr(III)(OH)3 at secondary alcohol sites. Tc(VII)O4- and I(V)O3- also undergo chemical reduction, following a similar removal mechanism. Oxyanion removal preference is determined by the anion reduction potential (CrO42->TcO4->IO3-), geometry, and charge density. For these reasons, 39% and 69% of TcO4- and 17% and 39% of IO3- are removed in the presence and absence of Cr(VI), respectively.

Optimizing flocculation of digestate to increase circularity in manure treatment

The flocculation of (co-)digested cattle and pig manure has rarely been investigated, leading to a rather intuitive use of flocculants in manure treatment processes, resulting in overdosing and increasing costs. Here, we investigate the effect of molecular weight, charge density and branching of reference and commercially available flocculants by establishing the optimal flocculant dosage and the corresponding maximum organic matter removal. Higher molecular weight flocculants show increased turbidity removal as result of their long chains corresponding to a higher amount adsorption sites. Results presented show that polymers with an increased cationic charge density give moderate and unstable flocculation due to the low amounts of non-charged parts essential for the hydrophobic interactions and hydrogen bonding. Further, the results show that a linear high molecular weight flocculant with a nonionic or a low anionic charge density is the most effective as it reached the highest organic matter removal at a low dosage.

Quantitative Composition and Mesoscale Ion Distribution in p-Type Organic Mixed Ionic-Electronic Conductors.

Understanding the ionic composition and distribution in organic mixed ionic-electronic conductors (OMIECs) is crucial for understanding their structure-property relationships. Despite this, direct measurements of OMIEC ionic composition and distribution are not common. In this work, we investigated the ionic composition and mesoscopic structure of three typical p-type OMIEC materials: an ethylene glycol-treated crosslinked OMIEC with a large excess fixed anionic charge (EG/GOPS-PEDOT:PSS), an acid-treated OMIEC with a tunable fixed anionic charge (crys-PEDOT:PSS), and a single-component OMIEC without any fixed anionic charge (pg2T-TT). A combination of X-ray fluorescence (XRF) and X-ray photoelectron spectroscopies, gravimetry, coulometry, and grazing incidence small-angle X-ray scattering (GISAXS) techniques was employed to characterize these OMIECs following electrolyte exposure and electrochemical cycling. In particular, XRF provided quantitative ion-to-monomer compositions for these OMIECs from passive ion uptake following aqueous electrolyte exposure and potential-driven ion uptake/expulsion following electrochemical doping and dedoping. Single-ion (cation) transport in EG/GOPS-PEDOT:PSS due to Donnan exclusion was directly confirmed, while significant fixed anion concentrations in crys-PEDOT:PSS doping and dedoping were shown to occur through mixed anion and cation transport. Controlling the fixed anionic (PSS-) charge density in crys-PEDOT:PSS mapped the strength of Donnan exclusion in OMIEC systems following a Donnan-Gibbs model. Anion transport dominated pg2T-TT doping and dedoping, but a surprising degree of anionic charge trapping (∼1020 cm-3) was observed. GISAXS revealed minimal ion segregation both between PEDOT- and PSS-rich domains in EG/GOPS-PEDOT:PSS and between amorphous and semicrystalline domains in pg2T-TT but showed significant ion segregation in crys-PEDOT:PSS at length scales of tens of nm, ascribed to inter-nanofibril void space. These results bring new clarity to the ionic composition and distribution of OMIECs which are crucial for accurately connecting the structure and properties of these materials.

Encapsulating melittin from animal venom by finely tuned charge compensation with polymer carriers

Due to their wide availability, polypeptide/protein venoms produced by certain insects are of high interest as potential active pharmacological ingredients; however, the number of clinical studies on these venoms remains poor. In this paper, we describe an extremely efficient platform to form polyplexes from cationic amphiphilic animal venoms, such as the hemolytic poison melittin. The idea is based on supramolecular melittin cationic charge compensation with nanoparticles (micelles composed of hydrophobic glassy polystyrene core and hydrophilic poly(meth)acrylic acid corona, PMA and PAA acid homopolymers) with high anion charge density at physiological pH. An instant “mix and go” process and efficient melittin complexation with nanoparticles at concentrations down to micrograms per milliliter of PBS solution was achieved and proven by inhibition of melittin-induced hemolysis. We studied in detail how the structural features of the nanoparticles influence their potency; we found that the most important parameter is the number of carboxylates in the polyanion chain (proportional to the molecular weight and length of the anionic poly(meth)acrylic acid block). The poly(meth)acrylic acid-based polymer nanoparticles may be useful as melittin (and possibly other cationic amphiphilic animal venoms) antidotes but also as models for constructing future delivery systems to apply the venoms therapeutically.

Impact of polyelectrolyte adsorption on the rheology of concentrated poly(N-isopropylacrylamide) microgel suspensions.

We explore the impact of three water-soluble polyelectrolytes (PEs) on the flow of concentrated suspensions of poly(N-isopropylacrylamide) (PNIPAm) microgels with thermoresponsive anionic charge density. By progressively adding the PEs to a jammed suspension of swollen microgels, we show that the rheology of the mixtures is remarkably influenced by the sign of the PE charge, PE concentration and hydrophobicity only when the temperature is increased above the microgel volume phase transition temperature Tc, namely when microgels collapse, they are partially hydrophobic and form a volume-spanning colloidal gel. We find that the original gel is strengthened close to the isoelectric point, attained when microgels are mixed with cationic PEs, while PE hydrophobicity rules the gel strengthening at very high PE concentrations. Surprisingly, we find that polyelectrolyte adsorption or partial embedding of PE chains inside the microgel periphery occurs also when anionic polymers of polystyrene sulfonate with a high degree of sulfonation are added. This gives rise to colloidal stabilization and to the melting of the original gel network above Tc. Contrastingly, the presence of polyelectrolytes in suspensions of swollen, jammed microgels results in a weak softening of the original repulsive glass, even when an apparent isoelectric condition is met. Our study puts forward the crucial role of electrostatics in thermosensitive microgels, unveiling an exciting new way to tailor the flow of these soft colloids and highlighting a largely unexplored path to engineer soft colloidal mixtures.

Preparation of nanodelivery systems for oral administration of low molecular weight heparin

Low molecular weight heparins (LMWHs) are only used parenterally. They have low oral absorption and bioavailability due to their high anionic charge density, exposure to enzymatic degradation and first-pass effect. The aim of this study was the development and evaluation of nanodelivery systems to increase the oral bioavailability of enoxaparin (low molecular weight heparin). In line with this goal, three nanosystems, such as three-layered nanofiber membrane (NF), enoxaparin loaded nanoparticles (NP) and three-layered nanofiber membrane loaded with enoxaparin nanoparticles (NP/NF) were prepared. As a result of the SEM images of nanofiber membranes, the surfaces of the fibers were found to be smooth and the fiber diameters were between 300 and 500 nm. Enoxaparin amount was found to be 390–400 μg/cm2 for nanofiber membranes. Porosity, specific surface area, contact angle, and work of mucoadhesion values were found to be 53.78%, 9.46 m2/g, 113.39°, 0.19 mJ/cm2 for NF formulation and 50.52%, 3.04 m2/g, 104.96°, 2.65 mJ/cm2 for NP/NF formulation, respectively. In vitro dissolution studies showed that less than 20% of the drug was released from the nanofibers at the end of 2 h in acidic pH. MTT studies showed that cell viability was more than 80%. Stability studies showed that there was no significant changes at three different storage conditions. In conclusion, nanodelivery systems were successfully prepared to increase the oral bioavailability of enoxaparin and to protect it from the acid pH of the stomach.

(Invited) Concentrated Hydrogen Bonded Electrolytes: Definition and Bulk & Interfacial Properties

We broadly refer to deep eutectic solvents (DESs) as concentrated H-bonded electrolytes (CoHBEs) where a composition specific to the “deep eutectic temperature” does not have to be met as long as the electrolyte possesses high salt concentration of the salt or the redox active specie and suppressed volatility are desired in energy storage, electrocatalysis, and electrodeposition processes. Liquid heterogeneity owing to H-bonding, similar to ionic liquids and DESs, CoHBEs present distinct electrode-electrolyte interfacial behavior.As a way to probe the electrode-electrolyte behavior of CoHBEs as a function of composition, we have performed electrochemical impedance spectroscopy and surface enhanced Raman spectroscopy (SERS). The potential dependent differential capacitance of choline chloride and ethylene glycol (1:2, 1:4, 1:6 molar ratio) mixtures do not present camel shaped curves as in the case of more extreme examples of concentrated electrolytes such as ionic liquids. The interfacial behavior is more similar to dilute systems, however, the H-bonding network presents a less mobile diffuse layer. While on glassy carbon, there is no specific ion adsorption, on metal electrodes chloride adsorption is observed. In chloride-free systems that are based choline oxalate mixed with ethylene glycol, capacitance is measured to be almost independent of the applied voltage on glassy carbon and gold. This is attributed to the strong binding energy of the solvation structure, as determined from theory, that hinders voltage-induced reorientations. Consistent to this behavior, the oxalate system also presents a very high viscosity. In addition, the voltage sweep range is limited in the case of oxalate system as it has narrower electrochemical window. On the other hand, choline acetate, which has a very similar chemical structure to the oxalate, undergoes specific ion adsorption particularly on gold electrode at a positive applied potential as confirmed by SERS. This is believed to be due to the reduced binding energy as calculated by density functional theory with -1 charge of the acetate in comparison to -2 charge in oxalate that leads to the desolvation and then the surface adsorption of the acetate. In the case of the choline bis(trifluorosulfonyl)imide and ethylene glycol mixture, a wider electrochemical window accompanied by a dampened u-shaped capacitance was observed with no specific ion adsorption.This study presents tuning of DESs and more broadly CoHBEs in terms of the bulk physical properties, the interfacial behavior near an electrode, and the coupled structuring effects through the variation in anion charge density and the extent of H-bonding.

“Cation/anion with co-solvation” type high-voltage aqueous electrolyte enabled by strong hydrogen bonding

Aqueous electrolytes are important charge transport media in various electrochemical applications. However, the water splitting seriously limits the operation voltage of aqueous electrolytes. Thus, further widening the electrochemical stability window (ESW) of aqueous electrolytes is great of importance. Here, based on the high charge density and high electro-negativity of halogen anions (F-), we proposed a “cation/anion with co-solvation” type 16 m KF aqueous electrolyte that can achieve a high conductivity of 196 mS cm−1, a record 3.4 V ESW based on stainless steel mesh and even 6.72 V ESW based on Al metal electrode that is much higher than the highest value currently reported. Such excellent feature is attributed to the strong hydrogen bonds between the F- anions and the water molecules at high concentrations. This work is helpful to provide a new path for design of ideal high-voltage aqueous electrolytes and to understand the important role of anions in aqueous electrolytes at the molecular level.

Endocytosis Involved d-Oligopeptide of Tryptophan and Arginine Displays Ordered Nanostructures and Cancer Cell Stereoselective Toxicity by Autophagy.

Owing to their self-aggregation propensity and selective interaction with the anionic membranes, the peptides rich in tryptophan (Trp) and arginine (Arg) are considered for the development of novel anticancer therapeutics. However, the structural insights from the perspective of backbone chirality and spatial orientation of side chains into the selective toxicity of peptides are limited. Here, we investigated the selectivity and cellular uptake of HHC36, a Trp/Arg-rich nonapeptide, and its d-enantiomer (allDHHC36) and a retroinverso analogue in the lung A549 and breast MDA-MB-231 cancer cells. We realized that the d-peptides can specifically induce autophagy at nontoxic concentrations only in the A549 cells supported from the LC 3-II immunostaining expression in the vicinity of the nucleus and the ultrastructural analysis revealing the autophagosome formation. The autophagic flux was also remarkable in the cells exposed to d-peptides at a far lower concentration in synergism with doxorubicin (DOX). In marked contrast, nonselective cell death was observed only if a high amount of HHC36 was applied. HHC36 tended to irregular collagen-like fibrils relative to allDHHC36 that distinctly formed higher-order coiled nanostructures. Interestingly, the short d-peptide fragments were generated in a harsh oxidative condition. Compared with the direct membrane transduction of HHC36, the entry of d-peptides into the lung cancer cells was controlled by endocytosis through the contribution of heparan sulfate proteoglycans (HSPGs) and cholesterol (CHO). However, both l- and d-peptides feasibly crossed the membrane and localized inside the S-phase-arrested cell nucleus. This suggested the likelihood of peptide intercalation with DNA that might differently appear in selective and/or nonselective deaths. These results unraveled the d-handedness-selective toxicity of a self-assembling Trp/Arg-rich sequence that is dependent on the cell type from the aspects of the density of anionic charges and CHO in the outer leaflet of the plasma membrane, as well as the intracellular redox imbalance that may drive the formation of toxic peptide nanostructure fragments.

Reversible Adsorption of Polycarboxylates on Silica Fume in High pH, High Ionic Strength Environments for Control of Concrete Fluidity.

Polycarboxylate-based superplasticizers are essential for production of ultrahigh-performance concrete (UHPC), facilitating particle dispersion through electrostatic repulsion and steric hindrance. This study examines for the first time the effect of changes in pH, ionic strength, and charge on the adsorption/desorption behavior of a polycarboxylate-based superplasticizer on silica fume in aqueous chemistries common in low-CO2 UHPC. Data from total organic carbon measurements, Fourier transform infrared and nuclear magnetic resonance spectroscopy, and zeta potential measurements reveal the silica surface chemistry and electrokinetic properties in simulated UHPC. Addition of divalent cations (Ca2+) results in polycarboxylate adsorption on silica fume via (i) adsorption of Ca2+ ions on the silica surface and a negative zeta potential of lower magnitude on the silica surface and (ii) reduction of polycarboxylate anionic charge density due to complexation with Ca2+ ions and counter-ion condensation. Addition of OH– ions results in polycarboxylate desorption via deprotonation of silanol groups and a negative zeta potential of greater magnitude on the silica surface. Simultaneous addition of both Ca2+ and OH– results in rapid polycarboxylate desorption via (i) formation of an electric double layer and negative zeta potential on the silica surface and (ii) an increase in polycarboxylate anionic charge density due to deprotonation of the carboxylate groups in the polymer backbone, complexation with Ca2+ ions, and counter-ion condensation. This provides an explanation for the remarkable fluidizing effect observed upon addition of small amounts (1.0 wt %) of a solid, powdered Ca source to fresh, low-CO2, UHPC, which exhibits significantly higher fresh state pH (>13) than those based on Portland cement (pH 11).

Insight into the aqueous Laponite® nanodispersions for self-assembled poly(itaconic acid) nanocomposite hydrogels: The effect of multivalent phosphate dispersants

HypothesisWe hypothesize, that physical network between Laponite® nanoparticles and high molecular weight polyelectrolyte formed by mixing of Laponite® nanodispersion (containing multivalent phosphate dispersant) and polyelectrolyte solution is strongly influenced by the type and content of dispersant, which forms electric double layer (EDL) closely to the Laponite® edges. Thus, optimum dispersant concentration is necessary to overcome clay-clay interactions (excellent clay delamination), but should not be exceeded, what would result in the EDL compression and weakening of attractions forming clay-polyelectrolyte network. Thus, deeper investigation of Laponite® nanodispersions is highly demanded since it would enable to better design the self-assembled clay-polyelectrolyte hydrogels. ExperimentsTo study clay interparticle interactions in the presence of various multivalent phosphates, complementary methods providing wide nanodispersion characterization have been applied: zeta potential measurement and SAXS technique (electrostatic interactions), oscillatory rheology (nanodispersion physical state) and NMR experiments (ion immobilization degree). FindingsIt was found that multivalent phosphates induce and tune strength of clay-polyelectrolyte interactions forming hydrogel network in terms of varying EDL on the Laponite® edges. Moreover, phosphate dispersing efficiency depends on the molecular size, chemical structure, and valence of the anion; its potential as efficient dispersant for hydrogel preparation can be evaluated by estimation of anion charge density.

Effects of the Surface Charge Density of Clay Minerals on Surface-Fixation Induced Emission of Acridinium Derivatives.

Surface-fixation induced emission is a fluorescence enhancement phenomenon, which is expressed when dye molecules satisfy a specific adsorption condition on the anionic clay surface. The photophysical behaviors of two types of cationic acridinium derivatives [10-methylacridinium perchlorate (Acr+) and 10-methyl-9-phenylacridinium perchlorate (PhAcr+)] on the synthetic saponites with different anionic charge densities were investigated. Under the suitable conditions, the fluorescence quantum yield (Φf) of PhAcr+ was enhanced 22.3 times by the complex formation with saponite compared to that in water without saponite. As the inter-negative charge distance of saponite increased from 1.04 to 1.54 nm, the Φf of PhAcr+ increased 1.25 times. In addition, the increase in the negative charge distance caused the increase in the integral value of the extinction coefficient and the radiative deactivation rate constant (kf) and the decrease in the nonradiative deactivation rate constant. It should be noted that the 2.3 times increase in kf is the highest among the reported values for the effect of clay. From these results, it was concluded that the photophysical properties of dyes can be modulated by changing the charge density of clay minerals.

How Teichoic Acids Could Support a Periplasm in Gram-Positive Bacteria, and Let Cell Division Cheat Turgor Pressure.

The cytoplasm of bacteria is maintained at a higher osmolality than the growth medium, which generates a turgor pressure. The cell membrane (CM) cannot support a large turgor, so there are two possibilities for transferring the pressure to the peptidoglycan cell wall (PGW): (1) the CM could be pressed directly against the PGW, or (2) the CM could be separated from the PGW by a periplasmic space that is isoosmotic with the cytoplasm. There is strong evidence for gram-negative bacteria that a periplasm exists and is isoosmotic with the cytoplasm. No comparable studies have been done for gram-positive bacteria. Here I suggest that a periplasmic space is probably essential in order for the periplasmic proteins to function, including especially the PBPs that remodel the peptidoglycan wall. I then present a semi-quantitative analysis of how teichoic acids could support a periplasm that is isoosmotic with the cytoplasm. The fixed anionic charge density of teichoic acids in the periplasm is ∼0.5 M, which would bring in ∼0.5 M Na+ neutralizing ions. This approximately balances the excess osmolality of the cytoplasm that would produce a turgor pressure of 19 atm. The 0.5 M fixed charge density is similar to that of proteoglycans in articular cartilage, suggesting a comparability ability to support pressure. An isoosmotic periplasm would be especially important for cell division, since it would allow CM constriction and PGW synthesis to avoid turgor pressure.

Anionic Tuning of Zeolite Crystallization

Zeolites are of great industrial relevance as catalysts, adsorbents, and ion-exchangers and typically synthesized under hydrothermal conditions. Rational regulation of their crystallization process...

Synthesis and performance of a series of novel low-molecular-weight superplasticisers with star-shaped phosphate frame

A new type of small-molecule phosphate superplasticiser (SP) was synthesised in one pot by the phosphorylation reaction of star-polyether with phosphoric acid. By varying the structure of the initiator polyamines, star-shaped small-molecule phosphate SPs with different molecular weights and anionic charge densities were prepared. The synthesised SPs were characterised by means of proton nuclear magnetic resonance, high-performance liquid chromatography, Fourier transform infrared spectroscopy and gel permeation chromatography. Their dispersion ability, adsorption behaviour and retardation effect on cement hydration were investigated. It was proved that the star-shaped small-molecule phosphate compounds with longer polyether chains and more phosphate groups could be successfully applied as anti-clay SPs. The findings provide useful information for optimising the performance of phosphated small-molecule chemical admixtures in the future.

Polyhydroxamic acid as an efficient metal chelator and flocculant for wastewater treatment

Hydroxamic acid containing organic polymeric flocculants were synthesized from three different commercially available polymeric flocculants, such as WAS590, Zetag 4100, and Zetag 4110. These three polymers are acrylamide and acrylic acid‐based copolymers with different molecular weights and anionic charge density. The conversion of the amide groups to hydroxamic acid groups in the polymers was carried out by the reaction with hydroxylamine at pH 14. The modified polymers were characterized for structure and composition by elemental analysis, FTIR, and NMR. The chelation activity of the modified polymers was determined toward iron (Fe3+) and copper (Cu2+). The flocculation activity of the non‐modified and modified polymers was evaluated toward produced water and scrubber water. The results showed that all the modified flocculants exhibit better chelation with Fe3+ and Cu2+. In addition, the modified polymers display improved flocculation effect on tested wastewater.

Generation and Use of Lignin-g-AMPS in Extended DLVO Theory for Evaluating the Flocculation of Colloidal Particles.

In this work, Kraft lignin (KL) was polymerized with 2-acrylamido-2-methylpropane sulfonic acid (AMPS) to generate an anionic water-soluble KL-g-AMPS polymer. The effects of reaction conditions on the charge density of polymers were evaluated to induce lignin-based polymers with the highest anionic charge density. The optimal process conditions were 2.5 mol/mol AMPS/lignin, 0.6 g/g solid/water ratio, 2.0 initiator/lignin weight ratio, 80 °C, 120 min, and pH 1.5, which yielded KL-g-AMPS with the anionic charge density of 4.28 mequiv/g and the grafting ratio of 285%. The chemical structure and compositions of the polymers were confirmed by 1H NMR and elemental analysis. The flocculation performance of the polymer was evaluated in an aluminum oxide suspension, and its performance was compared with that of a homopolymer of AMPS produced under the same conditions. In addition, the extended Derjaguin–Landau–Verwey–Overbeek (XDLVO) theory was applied to study the flocculation mechanism of the polymers and alumina particles. The results revealed that electrostatic interaction was found to be the dominant force in this flocculation process.