Anionic Poly Styrene Sulfonate Research Articles

Polyelectrolyte Additive-Modulated Interfacial Microenvironment Boosting CO2 Electrolysis in Acid.

Acidic CO2 electrolysis offers a promising strategy to achieve high carbon utilization and high energy efficiency. However, challenges remain in suppressing the competitive hydrogen evolution reaction (HER) and improving product selectivity. High concentrations of potassium ions (K+) can suppress HER and accelerate CO2 reduction, but they still inevitably suffer from salt precipitation problems. In this study, we demonstrate that the sulfonate-based polyelectrolyte, polystyrene sulfonate (PSS), enables to reconstruct the electrode-electrolyte interface to significantly enhance the acidic CO2 electrolysis. Mechanistic studies reveal that PSS induces high local K+ concentrations through electrostatic interaction between PSS anions and K+. In situ spectroscopy reveals that PSS reshapes the interfacial hydrogen-bond (H-bond) network, which is attributed to the H-bonds between PSS anions and hydrated proton as well as the steric hindrance of the additive molecules. This greatly weakens proton transfer kinetics and leads to the suppression of undesirable HER. As a result, a Faradaic efficiency of 93.9% for CO can be achieved at 250 mA cm-2, simultaneous with a high single-pass carbon efficiency of 72.2% on commercial Ag catalysts in acid. This study highlights the important role of the electrode-electrolyte interface induced by polyelectrolyte additives in promoting electrocatalytic reactions.

Polyelectrolyte Additive‐Modulated Interfacial Microenvironment Boosting CO2 Electrolysis in Acid

Acidic CO2 electrolysis offers a promising strategy to achieve high carbon utilization and high energy efficiency. However, challenges remain in suppressing the competitive hydrogen evolution reaction (HER) and improving product selectivity. High concentrations of potassium ions (K+) can suppress HER and accelerate CO2 reduction, but they still inevitably suffer from salt precipitation problems. In this study, we demonstrate that the sulfonate‐based polyelectrolyte, polystyrene sulfonate (PSS), enables to reconstruct the electrode‐electrolyte interface to significantly enhance the acidic CO2 electrolysis. Mechanistic studies reveal that PSS induces high local K+ concentrations through electrostatic interaction between PSS anions and K+. In situ spectroscopy reveals that PSS reshapes the interfacial hydrogen–bond (H–bond) network, which is attributed to the H–bonds between PSS anions and hydrated proton as well as the steric hindrance of the additive molecules. This greatly weakens proton transfer kinetics and leads to the suppression of undesirable HER. As a result, a Faradaic efficiency of 93.9% for CO can be achieved at 250 mA cm–2, simultaneous with a high single‐pass carbon efficiency of 72.2% on commercial Ag catalysts in acid. This study highlights the important role of the electrode‐electrolyte interface induced by polyelectrolyte additives in promoting electrocatalytic reactions.

Abstract 994: Chiroptical detection and mutation analysis of cancer-associated extracellular vesicles in microfluidic devices with oriented chiral nanoparticles

Abstract Small extracellular vesicles, often termed as “exosomes” carry informative cargo containing proteins and lipids, reflective of their cellular origin. Thus, they are promising biomarkers for early diagnosis of cancer. However, conventional profiling methods like quantitative polymerase chain reaction (qPCR) require complex procedures, thereby limiting the analytical sensitivity of exosomes for liquid biopsies. Here, we demonstrate a sensitive microfluidic device (CDEXO) that isolates and profiles cancer-associated exosomes directly from blood plasma using assembled chiral gold nanoparticles (AuNPs). The unique changes in chiral signals are associated with specific biomolecules on the exosomes’ membranes. Thus, we can distinguish exosomes of lung cancer patients from those of healthy individuals and detect mutated EGFR proteins on the membrane. Hence, this low-cost microfluidic device is an attractive technique for rapid, sensitive, and versatile profiling of various extracellular vesicles. Methods: The top layer of CDEXO devices were fabricated by soft lithography using polydimethylsiloxane (PDMS). The bottom glass slide was functionalized with a layer-by-layer assembly of cationic poly(dimethyl diallyl ammonium chloride) and anionic polystyrene sulfonate. AuNPs were prepared by adding gold nanoplates to a growth solution. Next, AuNPs were conjugated with biotinylated Annexin-V, using Neutravidin-biotin chemistry. Exosomes were harvested from lung cancer cell lines (A549, H1650, H3255) and lung fibroblasts (MRC5) and spiked into the CDEXO chip. EDTA was used to release the captured exosomes and quantified using nanoparticle tracking analysis (NTA). CD spectra were measured by spectrometry. Imaging of AuNPs and exosomes were done using scanning electron microscope (SEM). Results: CDEXO captures cancer-associated exosomes with an efficiency of 81.1±1.5%. H3255 derived exosomes that exhibited EGFR point mutation showed the greatest change in spectral signals from the baseline, followed by A549 (wild type), H1650, (EGFR exon19 deletion) and MRC5 (healthy). The CD responses were measurable at exosome numbers as low as 100. Further validation with 19 lung cancer patients showed an average 40% change in chiral signals from isolated exosomes that were 5.6 times higher in patients than healthy donors. Conclusions: A microfluidic device with chiral AuNPs allows sensitive and accurate detection of lung cancer-associated exosomes by conjugation with Annexin V. The resulting strong CD peaks that arise from specific interactions between exosomal surface proteins and chiral AuNPs facilitate in-depth profiling of target exosomes, including EGFR mutation expression. Citation Format: Yoon-Tae Kang, Ji-Young Kim, Emine Sumeyra Turali-Emre, Hee-Jeong Jang, Minjeong Cha, Abha Kumari, Colin Palacios-Rolston, Chitra Subramanian, Emma Purcell, Sarah Owen, Chung-Man Lim, Rishindra Reddy, Shruthi Jolly, Nithya Ramnath, Nicholas A. Kotov, Sunitha Nagrath. Chiroptical detection and mutation analysis of cancer-associated extracellular vesicles in microfluidic devices with oriented chiral nanoparticles [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 994.

Composites of nickel(II) polystyrene sulfonates: Where solution chemistry meets nanomaterials

Novel polymers of polystyrene sulfonate (PSS) with nickel(II) and its ethylenediamine (En) complexes, [NiEnx]2+ (x = 1–3), were synthesized by an exchange reaction of aqueous solutions of sodium polystyrene sulfonate (Na(PSS)) and nickel(II) chloride or its corresponding complexes. The absence of an effect of the anionic polymer on the equilibria of the formation of [NiEnx]2+ complexes in solutions was established by UV–visible spectroscopy and NMR relaxation. Nickel(II) polystyrene sulfonate (Ni(PSS)2) and [NiEn]PSS2 are highly soluble in water, while [NiEn2]PSS2 and [NiEn3]PSS2 have spontaneously formed gels after mixing of precursor solutions, and their solid samples were obtained after air drying. Ni(PSS)2 was obtained in solid form only by evaporating water from its aqueous solution. All the samples of new polymers were characterized by ATR FT-IR spectroscopy, laser confocal microscopy and scanning electron microscopy; their composition was confirmed by EDS analysis data. The hydration of the cation governs its binding with the polystyrene sulfonate anion. For Ni(PSS)2 both methods reveal existence of a large number of individual objects with an average diameter of 12–17 µm scattered over the surface. According to SEM these objects are isolated layered agglomerates of nanoparticles with mean diameter of 152 ± 34 nm. The EDS analysis confirmed that agglomerates contain pure NaCl nanoparticles while nickel polystyrene sulfonate forms a uniform substrate film. The conclusion is made that nickel polystyrene sulfonate film may be used as a substrate for the preparation of NaCl nanoparticles simply by drying a salt solution on it.

A near infra-red emitting supramolecular dye-polymer assembly as promising platform for protamine sensing

Detection and quantification of bioanalytes using near infra-red (NIR) probes provide several advantages, viz, negligible scattering of light, minimum interference from the background matrices, deep sample penetration, etc. Herein, we report a supramolecular dye-polymer complex, comprising of mono-cationic LDS-798 dye and multi-anionic polystyrene sulfonate (PSS), as a promising NIR emitting turn-on probe for protamine (Pr) sensing. The supramolecular complex displays moderate fluorescence enhancement for LDS-798 due to its binding onto PSS surface. Strikingly, in the presence of Pr, this complex displays further enhancement in its emission intensity, which is also substantiated by a significant increase in the excited-state lifetime of LDS-798 dye. This turn-on response is found to be highly selective towards Pr, which is attributed to the structural change taking place for the anionic PSS on its interaction with highly cationic Pr molecule. Such a conformational change creates several cavities into the modified PSS structure, which can suitably encapsulate LDS-798 dye via strong hydrophobic interaction. Accordingly, there is large decrease in the radiationless decay processes for the excited dye molecules, making them strongly emissive in nature. Furthermore, LDS-798−PSS complex is found to be quite robust against changing temperature and ionic strength of the medium, indicating its possible use as a fluorescent probe over a wide range of temperature and salinity.

Micellar and sub-micellar chromatography with a cocamidopropyl betaine surfactant

We have coated a typical C18 column with the pH cationic charge controllable zwitterionic synthetic surfactant, cocamidopropyl betaine (CAPB), in order to generate a mixed mode reversed phase weak ion exchange column. As determined by the Thomas model, the column has an adsorbed surfactant capacity of 0.557 mmoles. The addition of 8.8 × 10–4 M CAPB to the totally aqueous mobile phase ensured stability of the surfactant on the column and permitted separation of the four component sulfonamide mixture with micellar liquid chromatography (MLC) in under 11 min. Comparatively, with a dilute H2SO4 mobile phase with no CAPB, the separation time for the sulfonamide mixture reached an excessive run time of an hour on the bare C18 chains. With CAPB in the mobile phase (no organic solvent present), a seven component sulfonamide mixture could be separated in less than 45 min. A five component short chain carboxylic acid mixture, separated in 20 min, was used to examine the ion exchange character of the column in pH environments of 2.3 and 4.6. Three phase MLC equilibrium analysis was also done in these pH environments with the sulfa drug and carboxylic acid mixtures to determine partition coefficients. Finally, a quite high molecular weight (70,000) anionic polystyrene sulfonate polymer was characterized by MLC with only CAPB and variable pH mobile phases; the optimal pH was determined to be 5.6. A totally aqueous mobile phase without CAPB was not suitable for profiling this polymer.

Organic cation – polystyrene sulfonate polyelectrolytes as hole transporting interfacial layers in perovskite solar cells

Interfacial layers are important tools that can be used to control the band structure and performance of perovskite solar cells, however, relatively few p-type materials are known compared to n-type interfacial materials. In this work, we demonstrate that anionic polystyrene sulfonate (PSS) polyelectrolytes, with organic cations as counter ions, are able to function as p-type interfacial layers in methylammonium lead triiodide (MAPbI3) perovskite solar cells. These polyelectrolytes show interfacial dipole formation resulting in a significant increase in the work function of poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) and decrease in the Fermi energy of the CH3NH3PbI3 layer (band bending) as evident from x-ray photoelectron spectra (XPS) and ultraviolet photoelectron spectra (UPS) analysis. These effects result in superior electron blocking and hole extracting characteristics at the anode. We show that open circuit voltage, power conversion efficiency and other device parameters can be increased compared to the devices without interfacial layers using these convenient polyelectrolytes.

Light‐Powered Ion Pumping in a Cation‐Selective Conducting Polymer Membrane

AbstractThe simulation of the ion pumping against a proton gradient energized by light in photosynthesis is of significant importance for the energy conversion in a non‐biological environment. Herein, we report light‐powered ion pumping in a polystyrene sulfonate anion (PSS) doped polypyrrole (PPy) conducting polymer membrane (PSS‐PPy) with a symmetric geometry. This PSS‐PPy conducting polymer membrane exhibits a cationic selectivity and a light‐responsive surface‐charge‐governed ion transport attributed to the negatively charged PSS groups. An asymmetric visible irradiation on one side of the PSS‐PPy membrane induces a built‐in electric field across the membrane due to the intrinsic photoelectronic property of PPy, which drives the cationic transport against the concentration gradient, demonstrating an ion‐pumping effect. This work is a prototype that uses a geometry‐symmetric conducting polymer membrane as a light‐powered artificial ion pump for active ion transport, which exhibits potential applications in nanofluidic energy conversion.

Light-Powered Ion Pumping in a Cation-Selective Conducting Polymer Membrane.

The simulation of the ion pumping against a proton gradient energized by light in photosynthesis is of significant importance for the energy conversion in a non-biological environment. Herein, we report light-powered ion pumping in a polystyrene sulfonate anion (PSS) doped polypyrrole (PPy) conducting polymer membrane (PSS-PPy) with a symmetric geometry. This PSS-PPy conducting polymer membrane exhibits a cationic selectivity and a light-responsive surface-charge-governed ion transport attributed to the negatively charged PSS groups. An asymmetric visible irradiation on one side of the PSS-PPy membrane induces a built-in electric field across the membrane due to the intrinsic photoelectronic property of PPy, which drives the cationic transport against the concentration gradient, demonstrating an ion-pumping effect. This work is a prototype that uses a geometry-symmetric conducting polymer membrane as a light-powered artificial ion pump for active ion transport, which exhibits potential applications in nanofluidic energy conversion.

Effect of Counterion Binding to Swelling of Polyelectrolyte Brushes.

The effect of binding strength of counterions with the polyelectrolyte chain to the swelling of polyelectrolyte brushes is studied, by investigating the swelling of both the polycation and polyanion in response to the variation of the salt concentration under the change of counterion's identity. Two polyelectrolyte brushes grafted on solid substrates are adopted: the cationic poly [2-(methacryloyloxy)ethyltrimethyl ammonium] (PMETA-X, X = F, Cl, Br, and I) and the anionic polystyrene sulfonate (M-PSS, M = Li, Na, K, and Cs). The swelling change with the salt concentration is investigated by ellipsometry, quartz crystal microbalance with dissipation, and dielectric spectroscopy. It is discovered that although the thickness of PMETA-X brushes is larger than that of M-PSS brushes of similar grafting density, the former has much less solvent incorporated than the latter. Such a difference is attributed to the weaker interaction between the PMETA+ chain and its halide counterions than that between the PSS- chain and its alkali counterions, discovered by dielectric spectroscopy. This makes the original charges on the PMETA-X chain less neutralized and therefore have a higher charge density, compared with the M-PSS chain. The results demonstrate that the stronger binding of the counterions to the polyelectrolytes makes the main chains less charged, resulting in the weaker inter-chain electrostatic repulsion and less swelling of the brushes. Investigations into the effect of ion identity show the following order of binding strength: for the cationic PMETA+ chain, F- < Cl- < Br- < I- and for the anionic PSS- chain, Li+ < Na+ < K+ < Cs+.

Construction and characterization of sandwich-type laccase electrode based on functionalized conducting polymers

Laccase (Lac) is a multi-active-center glycoprotein. Its heterogeneous electron transfer efficiency depends on the distance between the substrate binding site and the electrode surface. Laccase encapsulation by conducting polymers should be favorable for the direct electron transfer (DET) process, thus improving the electrocatalytic efficiency of the laccase electrode. Here, a sandwich-type laccase electrode based on functionalized conducting polymers was developed. First, porous poly (3-aminophenylboronic acid) (PAPBA) conductive film was electrodeposited on a glassy carbon electrode (GCE), and on which laccase was then immobilized via the specific binding of the boronic acid group from PAPBA and the glycosyl group on laccase. In addition to higher laccase loading, the present Lac/PAPBA/GCE electrode is more robust than that prepared by physical adsorption of laccase on conducting polymer. For laccase to be wired better, a poly (3,4-ethylenedioxythiophene) (PEDOT) conductive film with polystyrenesulfonate anion (PSS−) as dopant was electrochemically covered on the Lac/PAPBA/GCE. In addition to the compatibility among the stability of the cyclic boronic acid ester, the biological activity of the laccase, and the polymer conductivity, the sandwich-type laccase electrode was demonstrated to be more efficient than the counterpart without the second layer for the electroreduction of O2 probably due to a so-called “cage effect”. The "cage effect" of the sandwich-type conducting polymers reduces the requirement for laccase orientation and greatly improves the electrocatalytic performance of the laccase electrode.

Supramolecular Porous Organic Nanocomposites for Heterogeneous Photocatalysis of a Sulfur Mustard Simulant.

Efficient heterogeneous photosensitizing materials require both large accessible surface areas and excitons of suitable energies and with well-defined spin structures. Confinement of the tetracationic cyclophane (ExBox4+ ) within a nonporous anionic polystyrene sulfonate (PSS) matrix leads to a surface area increase of up to 225 m2 g-1 in ExBox•PSS. Efficient intersystem crossing is achieved by combining the spin-orbit coupling associated to Br heavy atoms in 1,3,5,8-tetrabromopyrene (TBP), and the photoinduced electron transfer in a TBP⊂ExBox4+ supramolecular dyad. The TBP⊂ExBox4+ complex displays a charge transfer band at 450 nm and an exciplex emission at 520 nm, indicating the formation of new mixed-electronic states. The lowest triplet state (T1 , 1.89 eV) is localized on the TBP and is close in energy with the charge separated state (CT, 2.14 eV). The homogeneous and heterogeneous photocatalytic activities of the TBP⊂ExBox4+ , for the elimination of a sulfur mustard simulant, has proved to be significantly more efficient than TBP and ExBox+4 , confirming the importance of the newly formed excited-state manifold in TBP⊂ExBox4+ for the population of the low-lying T1 state. The high stability, facile preparation, and high performance of the TBP⊂ExBox•PSS nanocomposites augur well for the future development of new supramolecular heterogeneous photosensitizers using host-guest chemistry.

Cellulose Nanocrystal-Polyelectrolyte Hybrids for Bentonite Water-Based Drilling Fluids.

Cellulose nanocrystals (CNCs), with their rodlike shape and nanoscale dimensions, greatly improve the filtration performance of bentonite-containing, water-based drilling fluids (BT-WDFs) through interactions with the BT platelets. When these WDFs are exposed to high salt concentrations, though, their fluid retention properties are greatly diminished due to reduced CNC-BT interaction and BT aggregation/flocculation. Consequently, we reduce BT-BT interaction at high salt by grafting polyelectrolytes (PE) to CNC particles (CNC-PE) to enhance CNC-BT interactions when incorporating these hybrid particles with BT-WDFs. The particles sterically and electrostatically screen BT platelets from associating, thus improving fluid filtration performance at high salt. Three types of CNC modifications were carried out: grafting from direct surface initiation, modification with vinyl-terminated glycidyl methacrylate (GMA) before grafting, and physical mixing of CNC with a polymer. These modifications were performed using three polyelectrolyte materials: anionic polystyrene sulfonate (PSS), cationic polyacrylamide (PAM), and a random copolymer of PSS and PAM (PSS-co-PAM). Formulations containing CNC-PEs prepared by covalent grafting exhibited superior filtration properties compared to those in which CNCs and PEs were physically mixed. The higher graft loading achieved with the GMA method resulted in poorer filtration results compared to the direct grafting method due to CNC-PE interparticle cross-linking. PSS-modified CNC-PEs appeared to attach to BT edges, while PAM-modified CNC-PEs attached to the BT faces. These interactions disrupted BT aggregation, with the PSS-co-PAM CNC hybrid displaying the most desired filtration properties. The results highlight the importance of steric and charge stabilization of the BT particle edges and faces to achieve high-performance WDFs for well excavation.

Conductive poly(3,4-ethylenedioxythiophene) is effectively degradable by hydrogen peroxide with iron (II) chloride

The water soluble conductive poly(3,4-ethylenedioxythiophene) often uses the anionic polystyrene sulfonate as the template to form PEDOT(PSS), which is estimated to have a huge market value due to the wide variety of applications derived from its promising physical and electrochemical properties. To meet the green chemistry principles, we have previously investigated and optimized the synthesis of PEDOT(PSS) catalyzed by horseradish peroxidase. In this study, we have accidently found this PEDOT(PSS) could be degraded by hydrogen peroxide at a high concentration with a long period of time, we then searched for the possibility to improve the degradation efficiency with a moderate condition. Our results have demonstrated the degradation of PEDOT(PSS) could be significantly promoted by heating, in particular by employing iron (II) chloride as a Fenton's agent. Since hydrogen peroxide is easily available and environmentally compatible, the degradation process proposed for PEDOT(PSS) is eco-friendly and sustainable.

Green chemical process for the synthesis of conductive poly(3,4‐ethylenedioxythiophene) by nonthermal plasma‐activated hydrogen peroxide

AbstractPoly(3,4‐ethylenedioxythiophene) or PEDOT is a promising conductive polymer, which generally uses anionic polystyrene sulfonate (PSS) as the template to become water soluble. Besides the chemical and enzymatic approaches, we are presenting a novel method by employing nonthermal plasma‐activated hydrogen peroxide (PAH) to promote the synthesis of water‐soluble PEDOT(PSS), which is a more environment‐friendly technology. The reaction did not utilize any other chemical solvents, except for a monomer, template as well as hydrogen peroxide, and was initiated in a neutral aqueous solution. We have found that a heating procedure under 60°C was necessary for the effective synthesis of PEDOT(PSS). The final product was further characterized by UV–Vis spectrum, Fourier‐transform infrared spectroscopy, and conductivity measurements.

99mTc-radiolabeled composites enabling in vivo imaging of arterial dispersal and retention of microspheres in the vascular network of rabbit lungs, liver, and liver tumors.

PurposeSelective internal radiation therapy (SIRT) is an effective treatment option for liver tumors, using Y-90-loaded polymer microspheres that are delivered via catheterization of the hepatic artery. Since Y-90 is a beta emitter and not conveniently imaged by standard clinical instrumentation, dosimetry is currently evaluated in each patient using a surrogate particle, 99mTechnetium-labeled macroaggregated albumin (99mTc-MAA). We report a new composite consisting of 99mTc-labeled nanoparticles attached to the same polymer microspheres as used for SIRT, which can be imaged with standard SPECT.MethodsCarbon nanoparticles with an encapsulated core of 99mTc were coated with the polycation protamine sulfate to provide electrostatic attachment to anionic polystyrene sulfonate microspheres of different sizes (30, 12, and 8 µm). The in vivo stability of these composites was determined via intravenous injection and entrapment in the capillary network of normal rabbit lungs for up to 3 hours. Furthermore, we evaluated their biodistribution in normal rabbit livers, and livers implanted with VX2 tumors, following intrahepatic artery instillation.ResultsWe report distribution tests for three different sizes of radiolabeled microspheres and compare the results with those obtained using 99mTc-MAA. Lung retention of the radiolabeled microspheres ranged from 72.8% to 92.9%, with the smaller diameter microspheres showing the lowest retention. Liver retention of the microspheres was higher, with retention in normal livers ranging from 99.2% to 99.8%, and in livers with VX2 tumors from 98.2% to 99.2%. The radiolabeled microspheres clearly demonstrated preferential uptake at tumor sites due to the increased arterial perfusion produced by angiogenesis.ConclusionWe describe a novel use of radiolabeled carbon nanoparticles to generate an imageable microsphere that is stable in vivo under the shear stress conditions of arterial networks. Following intra-arterial instillation in the normal rabbit liver, they distribute in a distinct segmented pattern, with the smaller microspheres extending throughout the organ in finer detail, while still being well retained within the liver. Furthermore, in livers hosting an implanted VX2 tumor, they reveal the increased arterial perfusion of tumor tissue resulting from angiogenesis. These novel composites may have potential as a more representative mimic of the vascular distribution of therapeutic microspheres in patients undergoing SIRT.

Effect of Concentration on the Ionic Interaction between Polystyrene Sulfonate and Cationic Surfactant in Aqueous Solution

Polystyrene sulfonate (PSS) were prepared by sulfonation method of polystyrene using sulfuric acid. Abundant amount of polystyrene waste can be reused as a coagulant, membrane for polymer fuel cell and anionic-cationic polymer interactions. The characterization of PSS was carried out by using UV-Vis, Fourier transform infrared spectroscopy (FTIR), nuclear magnetic resonance (NMR) spectra, molecular weight and analysis of sulfonation degree. The degree of sulfonation was obtained at 94,18%. Ionic interaction between anionic polymer PSS and cetyltrimethylammonium bromide (CTAB) as cationic compound in aqueous solution were analyzed by using dynamic light scattering (DLS), conductometry and fluorimetry. Behavior of conductivity have been calculated the critical micelle concentration (cmc). The FTIR and 1H-NMR spectra showed the ionic interaction between PSS and CTAB. This ionic interaction can be controlled by changing the polymer concentration.

Cadmium Removal from Contaminated Water Using Polyelectrolyte-Coated Industrial Waste Fly Ash.

Fly ash (FA) is a major industrial waste generated from power stations that add extra cost for proper disposal. Recent research efforts have consequently focused on developing ways to make use of FA in environmentally sound applications. This study, therefore, investigates the potential ability of raw fly ash (RFA) and polyelectrolyte-coated fly ash (PEFA) to remove cadmium (Cd) from polluted water. Using layer-by-layer approach, functionalized fly ash was coated with 20 layers from 0.03% (v/v) of cationic poly(diallyldimethylammonium chloride) (PDADMAC) and anionic polystyrene sulfonate (PSS) solutions. Both surface morphology and chemical composition of the adsorbent (PEFA) were characterized using Field-Emission Scanning Electron Microscope (FE-SEM), X-Ray Diffraction (XRD), Fourier-Transform Infrared (FTIR), and X-Ray Fluorescence (XRF) techniques. The effects of pH, adsorbent dosage, contact time, initial contaminant concentration, and mixing rate of the adsorption of Cd were also studied in batch mode experiments. Results of the study revealed that a 4.0 g/L dosage of PEFA removed around 99% of 2.0 mg/L of Cd in 15 min at 150 rpm compared to only 27% Cd removal achieved by RFA under the same conditions. Results also showed that adsorption by PEFA followed both Langmuir and Freundlich models with correlation coefficients of 98% and 99%, respectively.

The effect of cation type, ionic strength and temperature on the complexation between polyallylammonium cation and polystyrenesulfonate anion

The reaction between polyallylammonium cation and polystyrenesulfonate anion was investigated in alkali-metal chloride (MCl, M=Li, Na, K, Rb, Cs), sodium perchlorate and tetraethylammonium chloride solutions by means of microcalorimetry, potentiometry, DLS and spectrophotometry. The influence of ionic strength, temperature and addition order on the course of interpolyelectrolyte neutralisation was examined. At lower molar ratios of positively to negatively charged monomers and at 25°C primary polyelectrolyte complexes were formed. Close to equivalence their flocculation occurred. The complexation was predominantly entropically driven, however a correlation between obtained reaction and cation hydration enthalpies was noticed. The composition of the precipitates at equimolar monomer ratio in chloride salt solutions did not significantly depend on the addition order up to 1.0moldm−3 salt concentration. In contrast, the ratio of oppositely charged monomers in precipitates prepared in NaClO4 (c/moldm−3≥0.5) was affected by the addition order in a wide temperature range. The increase in electrolyte concentration and the decrease in temperature led to more pronounced asymmetric neutralisation. The equilibrium establishment in NaClO4(aq) proceeded extremely slowly. Even at high perchlorate concentrations the final reaction product was virtually insoluble polysalt.

Sonication-Assisted Layer-by-Layer Assembly for Low Solubility Drug Nanoformulation.

Sonication-assisted layer-by-layer (LbL) self-assembly is a nanoencapsulation technique based on the alternate adsorption of oppositely charged polyelectrolytes, enabling the encapsulation of low solubility drugs. In this work, a top-down LbL technique was performed using a washless approach and ibuprofen (IBF) as a model class II drug. For each saturated layer deposition, polyelectrolyte concentration was determined by titration curves. The first layer was constituted by cationic poly(allylamine hydrochloride) (PAH), given the IBF negative surface charge, followed by anionic polystyrenesulfonate (PSS). This polyelectrolyte sequence was made up with 2.5, 5.5, and 7.5 bilayer nanoshells. IBF nanoparticles (NPs) coated with 7.5 bilayers of PAH/PSS showed 127.5 ± 38.0 nm of particle size, a PDI of 0.24, and a high zeta potential (+32.7 ± 0.6 mV), allowing for a stable aqueous nanocolloid of the drug. IBF entrapment efficiency of 72.1 ± 5.8% was determined by HPLC quantification. In vitro MTT assay showed that LbL NPs were biocompatible. According to the number of coating layers, a controlled release of IBF from LbL NPs was achieved under simulated intestinal conditions (from 5 h up to 7 days). PAH/PSS-LbL NPs constitute a potential delivery system to improve biopharmaceutical parameters of water low solubility drugs.