Organic Polyelectrolytes Research Articles

Interactions between graphene sheets and ionic molecules used for the shear-assisted exfoliation of natural graphite

Water-soluble graphene suspensions have been prepared directly from natural graphite powder. Graphite is mechanically ground with small ionic organic molecules or polyelectrolytes, followed by sonication. The grinding produces a mechanical shearing force, which is supposed to expose new surface and help the molecules to adsorb on it and intercalate into the graphite lattice. The graphene composites, their aqueous suspensions and, especially, the interactions between the adsorbates and the graphene sheets, were characterized using UV–vis and luminescence spectroscopy, X-ray photoelectron spectroscopy, Raman spectroscopy, particle size distribution and zeta potential measurements, and atomic force microscopy. The sign of the zeta potential of the colloidal graphene sheets was determined by the charge of the adsorbate. Highest zeta potentials were obtained with polyelectrolytes and taurodeoxycholic acid but the stability of the pyrene and naphthalene based suspensions was also good or even excellent. Changes in the aggregation of the molecules upon adsorption were observed and a specific donor/acceptor interaction between the hydroxy group of the naphthalene derivative and graphene was evidenced by the fluorescence spectra. In most cases the suspensions contained significant amounts of single or few-layer graphene.

Influence of sewage sludge treatment on pyrolysis and combustion of dry sludge

The influence of sewage sludge treatment on its pyrolysis and combustion and the N, S and Cl emissions was studied by thermogravimetry-mass spectrometry in the range 25–800 °C. Two types of sludge were used (L and F). L underwent anaerobic digestion and was treated with organic polyelectrolyte, while F was treated with FeCl3 and lime. The treatment with inorganic additives had a notable influence on the pyrolysis and combustion processes. During F pyrolysis, the most significant effects of CaO/CaCO3 from lime and Fe2O3 from FeCl3 were: 1) Fe2O3 promoted oxidation reactions, and char gasification at around 600 °C; 2) CaO promoted H2 formation at around 480 °C due to its action on water–shift reaction, and the partial SO2 retention by forming CaSO4. During combustion, Fe2O3 exhibited a high catalytic activity on oxidation reactions. Thus, an intense devolatilisation was produced in the range 200–377 °C, this being accompanied by a high formation of CO2, NO2 and Cl2. Also, the formation of SO2/SO3 was promoted, which were retained by CaCO3/CaO at temperatures higher than 377 °C. The nth-order reaction model describes adequately the global reaction that occurs in each stage, except for the second stage of L combustion that was described by the geometrical contraction model.

Modification of oxygen transfer rates in activated sludge with its characteristic changes by the addition of organic polyelectrolyte

The present study focused on the influence of the apparent viscosity of activated sludge on mixed liquor oxygen transfer rates, and examined whether both could be modified by the addition of an organic polyelectrolyte. Batch experiments carried out using mixed liquor samples in a stirred tank reactor revealed that α-factors, which incorporate any difference in oxygen mass transfer coefficient values between clean water and mixed liquor samples, showed exponential relationships when plotted against increases in mixed liquor apparent viscosities and sludge mixed liquid suspended solids values. Furthermore, oxygen mass transfer coefficients increased exponentially with increases in the Reynolds number, a parameter which reflects liquid turbulence levels. Oxygen mass transfer rates of five sludge samples collected from four full scale wastewater treatment plants (WWTPs) also increased by about 10% after flocculation, while with a sludge sample collected from the lab scale reactor, it decreased by about 5%. One likely explanation is that the apparent viscosities of the WWTPs and the lab-reactor sludges decreased and increased respectively after flocculation. Such changes probably reflect changes in the volume fraction of mixed liquor suspended solids as indicated by changes in sludge volume indices, particle size values and endogenous respiration rates before and after flocculation. These findings assist in developing an understanding of how oxygen mass transfer characteristics may be affected by activated sludge suspensions, and hence assist in reducing the operational costs of WWTPs.

Derivation of the stress-strain behavior of the constituents of bio-inspired layered TiO2/PE-nanocomposites by inverse modeling based on FE-simulations of nanoindentation test.

Owing to the apparent simple morphology and peculiar properties, nacre, an iridescent layer, coating of the inner part of mollusk shells, has attracted considerable attention of biologists, material scientists and engineers. The basic structural motif in nacre is the assembly of oriented plate-like aragonite crystals with a 'brick' (CaCO3 crystals) and 'mortar' (macromolecular components like proteins) organization. Many scientific researchers recognize that such structures are associated with the excellent mechanical properties of nacre and biomimetic strategies have been proposed to produce new layered nanocomposites. During the past years, increasing efforts have been devoted towards exploiting nacre's structural design principle in the synthesis of novel nanocomposites. However, the direct transfer of nacre's architecture to an artificial inorganic material has not been achieved yet. In the present contribution we report on laminated architecture, composed of the inorganic oxide (TiO2) and organic polyelectrolyte (PE) layers which fulfill this task. To get a better insight and understanding concerning the mechanical behaviour of bio-inspired layered materials consisting of oxide ceramics and organic layers, the elastic-plastic properties of titanium dioxide and organic polyelectrolyte phase are determined via FE-modelling of the nanoindentation process. With the use of inverse modeling and based on numerical models which are applied on the microscopic scale, the material properties of the constituents are derived.

A Coagulant Survey for Chemically Enhanced Primary Treatment of Synthetic CSOs

Combined sewer overflow (CSO) wastewaters tend to be highly variable in composition, presenting a challenge to effective treatment. The robustness of various coagulants and flocculants was studied in terms of their ability to bring about efficient contaminant removal under variable conditions. To accomplish this, the effects of total suspended solids (TSS) and dissolved organic carbon (DOC) concentrations on chemically enhanced settling of synthetic CSO wastewater were evaluated using various inorganic salt and organic polyelectrolyte products. The evaluated products varied in their responses to changes in solids and organics concentrations, particularly in terms of sensitivity to DOC concentration and ability to bring about its removal. The required dosages of the coagulants (both inorganic and organic) were quite sensitive to DOC concentration, but good to excellent TSS and DOC removals were obtained. In comparison, the polymer flocculants displayed good TSS removal but poor reduction of DOC under all conditions, in spite of sensitivity to initial DOC concentration. The coagulants and flocculants studied also varied in tendency to overdosing and effect on pH. While no coagulant or flocculant is universally applicable, understanding the trends in treatment efficiency can help in choosing the type of product that is most suitable for treatment under given wastewater quality conditions.

Effect of organic polyelectrolytes on H*-aggregation of meso-methyl-substituted thiacarbocyanine dyes

H*-Aggregation of anionic meso-methyl-substituted thiacarbocyanines of different structures has been studied in dilute aqueous solutions and in the presence of cationic organic polyelectrolytes. The thermodynamic parameters of the H*-aggregation from the trans-dimers have been determined. The thermodynamic equilibrium between two forms of the H*-aggregates in the presence of poly-N,N-dimethyl-N,N-diallylammonium chloride has been observed for the first time, and these forms have been assigned to H* cis and H* trans forms.

Effect of Electrical Characteristics Modification on Viscosity of Kaolin Suspension

Modifications of the interfacial electrical characteristics of kaolin were investigated through reversing particles surface charges induced by organic cationic polyelectrolyte and natural anionic organic substance. Zeta potential and rheology tests indicated that polymeric OH-Al reversed the edge charges and reached a saturation adsorption on kaolin surface at dosage of 45μmol/g, corresponding to a lower viscosity of kaolin suspension, as a result of the combined action of OH-Al modified positive particle surface and negative charges from sodium hexametaphosphate dispersant. A significant reduction in viscosity of kaolin modified by gallic acid was also observed in either dilute or concentrated suspension. The strong interaction of OH-Al ions with clay greatly increased the gallic acid adsorption, and resulted in the lowest viscosity for modified kaolin, indicating the bound of gallic acid to the reactive surface sites induced by OH-Al. It can be concluded in this experiments that the highly charged organic coating play a role in the dispersion of kaolin particles.

Monolayers and Langmuir–Blodgett films of Fe 2+-mediated polyelectrolyte with viologen derivatives as linkers at the air–water interface

Monolayer behaviors of newly synthesized viologens (Vs) containing tolunitrile substituents have been investigated at the air–water interfaces. Surface pressure–area isotherms indicated that these viologens could not form stable monolayers on the surfaces of the subphases of pure water, Fe(BF 4) 2 and anionic polyelectrolyte of PSS (PSS: poly(styrenesulfonic acid- o-maleic) acid), while they could form insoluble monolayers on the surface of the subphase containing mixtures of Fe(BF 4) 2 and PSS, which was attributed to the formation of Fe–V metal–organic polyelectrolytes based on an interfacial coordinative reaction between the Fe 2+ ions and viologen derivatives. With the use of Langmuir–Blodgett (LB) method, monolayers of Fe–V polyelectrolytes were transferred on the substrate surfaces. X-ray photoelectron spectra indicated that the LB film was composed of the elements of S, C, N, O and Fe, suggesting the formation of Fe–V/PSS hybrid multilayers. Cyclic voltammograms of the viologens revealed two reversible redox couples in the solutions, corresponding to two electron transfers of V 2+ ↔ V + and V + ↔ V 0, respectively. For the indium tin oxide electrode covered by the LB films of Fe–V/PSS, only one broad redox couple was recorded in the potential range of 0 and −1.0 V vs Ag/AgCl, which was attributed to the first redox couple of V 2+ ↔ V + . The charger transfer process of viologens in the solutions and Fe–V/PSS multilayers was investigated by the potential chronocoulometry method.

Effects of cationic polyelectrolyte on filterability and fouling reduction of submerged membrane bioreactor (MBR)

Organic and inorganic polyelectrolytes are commonly used as coagulants or flocculants in membrane bioreactor to enhance the filtration properties of membranes. The main objective of this study was to determine the effectiveness of organic cationic polyelectrolyte (CPE) addition on filterability of various membranes and to investigate the influences on fouling of membranes. First, batch tests were performed to determine the optimum polyelectrolyte concentration at which the highest soluble microbial products (SMPs) removal was observed. Then, short-term filtration test were conducted. Cellulose acetate, polyethersulfone, mixed ester, polycarbonate (CA, PES, ME, PC) membranes with two different pore sizes (0.45–0.40 and 0.22–0.20 μm) were used in submerged MBR experiments. Permeate flux decline at constant vacuum was observed with time. Protein and carbohydrate analysis were performed in the permeate samples. Filtration resistances were determined for each membrane. Cake resistance was observed to be the most significant fouling mechanism for all membranes. Polyelectrolyte addition decreased the cake resistance. The effect of polyelectrolyte on pore resistance was relatively insignificant. The results showed that addition of polyelectrolyte had significant impact on sustainable filtration time.

Pretreatment of Palm Oil Mill Effluent (POME) Using Magnetic Chitosan

Chitosan is a natural organic polyelectrolyte of high molecular weight and charge density; obtained from deacetylation of chitin. This study explored the potential and effectiveness of applying chitosan‐magnetite nanocomposite particles as a primary coagulant and flocculent, in comparison with chitosan for pre‐treatment of palm oil mill effluent (POME). A series of batch coagulation processes with chitosan‐magnetite nanocomposite particles and chitosan under different conditions, i.e. dosage and pH were conducted, in order to determine their optimum conditions. The performance was assessed in terms of turbidity, total suspended solids (TSS) and chemical oxygen demand (COD) reductions. Chitosan‐magnetite particles showed better parameter reductions with much lower dosage consumption, compared to chitosan, even at the original pH of POME, i.e. 4.5. At pH 6, the optimum chitosan‐magnetite dosage of 250 mg/L was able to reduce turbidity, TSS and COD levels by 98.8%, 97.6% and 62.5% respectively. At this pH, the coagulation of POME by chitosan‐magnetite was brought by the combination of charge neutralization and polymer bridging mechanism. On the other hand, chitosan seems to require much higher dosage, i.e. 370 mg/L to achieve the best turbidity, TSS and COD reductions, which were 97.7%, 91.7% and 42.70%, respectively. The synergistic effect of cationic character of both the chitosan amino group and the magnetite ion in the pre‐treatment process for POME brings about enhanced performance for effective agglomeration, adsorption and coagulation.

Design of silica microparticles with oligopeptide brushes and their interaction with proteins

Synthesis of small oligopeptide brushes (oligo(S-benzyl-l-cysteine)) onto polyelectrolyte functionalized silica microparticles was developed. Poly(vinyl amine) (PVAm) adsorbed from salt-free and KCl 10−1 mol L−1 aqueous solution onto silica microparticles was chemically and naturally cross-linked by epichlorohydrin and CO2, respectively. After the adsorption of PVAm onto microporous silica particles and stabilization by cross-linking, five repeated coupling reactions of Boc-S-benzyl-l-cysteine were performed. To test the protein interactions with the newly designed surface, human serum albumin (HSA) has been selected as a model protein. X-ray photoelectron spectroscopy, total organic carbon, potentiometric and polyelectrolyte titrations, and electrokinetic analysis were employed to obtain information about the polyelectrolyte adsorption and the amount of the amino acid S-benzyl-l-cysteine that was covalently bound to the solid surface and for determination of the protein amount adsorbed onto functionalized surface. The amount of HSA adsorbed onto modified silica microparticles decreased in order: silica/PVAm-cross-linked (silica/PVAm-C) (8.00 mg g−1) > silica/PVAm-C/S-benzyl-l-cysteine (6.34 mg g−1) > silica (4.86 mg g−1) > silica/PVAm-C/(S-benzyl-l-cysteine)5 (1.86 mg g−1).

Polyelectrolyte determination in drinking water

Chemical contaminants that occur in drinking water are not usually associated with acute health effects when compared to microbial contaminants and are usually given a lower priority. Those that are of concern have cumulative toxic properties such as metals and substances that are carcinogenic. Some of these potentially hazardous chemical contaminants are a consequence of the treatment chemicals themselves e.g. organic polyelectrolytes used as coagulant aids in water treatment. The presence of residues of the un-reacted monomer in these polyelectrolyte products is a cause for concern. Historically, inorganic coagulants such as aluminium sulphate and ferric chloride have been used as coagulants/flocculants in the treatment of drinking water. The residual amounts of these chemicals were easy to detect and to control using readily available standard methods. The increasing use of polyelectrolytes has created a problem for the potable water industry as there are no readily available methods for the determination of residual polyelectrolyte concentration. This study aims at extending existing analytical techniques and comparing them to determine results that are most accurate and reliable to the quantification of residual polyelectrolytes.

The Control of Solution Composition on Ligand-Promoted Dissolution: DTPA−Barite Interactions

The mechanism and kinetics of barite (BaSO4) dissolution in the presence of diethylenetriaminepentaacetic acid (DTPA) has been investigated as a function of solution composition. The dependence of the reaction rate on the background electrolyte present in solution (NaCl or KCl) and on the concentration of the chelating agent (DTPA) is explained by considering chemical speciation and conformational changes of DTPA in the aqueous phase. A mechanism for the promotion of the dissolution reaction by dissociated ionic species is proposed for an organic polyelectrolyte with a strong affinity to Ba2+ ions (DTPA) and for simple inorganic electrolytes. The mobilization of ions from the crystal structure is suggested to be induced mainly by water molecules and not by specific additive−surface interactions. Recognition of the correlation between solution composition, ion−water interactions (hydration phenomena), and the dissolution process enables an explanation of the faster dissolution kinetics of barite in the aqueous solution of a simple inorganic salt (NaCl) compared to in the solution of a strong chelating agent (DTPA). Our findings imply that because the mechanisms of complexation in solution and mobilization of ions from the solid surface are different, the sequestering capacity of the ligand toward dissolved ions cannot be used to predict the dissolution rate.

Internal Treatment of Process Waters in Paper Production by Dissolved Air Flotation with Newly Developed Chemicals. 2. Field Trials

New chemicals, based on the synergistic effect between inorganic polyaluminium salts and organic cationic polyelectrolytes, have been tested previously at laboratory-scale, and the most efficient product has been selected for an industrial trial for a dissolved air flotation unit of a paper mill based on 100% recovered paper (part 1 of this work). A polyaluminium nitrate sulfate salt combined with a quaternary polyamine has been evaluated in a long-term industrial trial for assessing its potential benefits. Results indicate that this new chemical is able to improve the removal of contaminants by dissolved air flotation, especially when the contamination load of the waters is high, allowing a further closure of the water circuits.

Internal Treatment of Process Waters in Paper Production by Dissolved Air Flotation with Newly Developed Chemicals. 1. Laboratory Tests

New chemicals, based on the synergistic effect between inorganic polyaluminium salts and organic cationic polyelectrolytes, have been tested for the chemical optimization of a dissolved air flotation (DAF) unit, used as internal treatment of process waters in a paper mill based on 100% recovered paper. Laboratory tests have demonstrated that polyamine modifications of the aluminum salts are the most efficient in the removal of contaminants, the combination of a polyaluminium nitrate sulfate salt and a polyamine being the most efficient. This chemical has been studied under different conditions, such as different dosages or in combination with a flocculant for the treatment of waters from different paper grades production, and the results have demonstrated a good performance at laboratory scale. Therefore, a field trial has been recommended for assessing its potential benefits at mill scale, which will be described in a future paper.

Designing Nano-Hydroxyapatite in the Polyelectrolyte Complex Macroporous Scaffold Based on Chitosan and Hyaluronic Acid

Owing to the unique characters of the hybrid scaffold components, a novel biodegradable porous composite scaffold was prepared. The nano hydroxyapatite (HAP) (73~136 nm) was crystallized in situ on the organic polyelectrolyte complex matrix through a biomimetic method. The polyelectrolyte complex composed of chitosan and hyaluronic acid had strong impacts on the formation of the nano HAP and directed in situ crystallization of the nano HAP as template. The in situ nano HAP reduced the interfacial energy and presented nano intensifier to the nano hybrid scaffold. Meanwhile, the scaffold kept high porosity.

Catanionic surfactant vesicles for electrostatic molecular sequestration and separation

Mixtures of oppositely charged surfactants, commonly called catanionic mixtures, are one of the most interesting and promising areas of colloidal chemistry. In this paper we review our previous work and report new results on electrostatic adsorption of organic solutes and DNA to the exterior surfaces of catanionic, unilamellar vesicles which form spontaneously in mixtures of sodium dodecylbenzenesulfonate (SDBS) and cetyltrimethylammonium tosylate (CTAT). Our group, along with others, has shown that organic ions and polyelectrolytes will bind to the exterior surface of oppositely charged catanionic vesicles through interactions with unpaired ionic surfactants present in the vesicle bilayer. The electrostatic sequestration of organic ions with catanionic vesicles is extremely efficient with excellent long-term stability and can be used to perform separations on mixtures of charged organic solutes. Using regular solution theory extended to vesicle-forming surfactant mixtures, we can understand how the composition of the bilayer changes with surfactant dilution, and we study this effect using fluorescence correlation spectroscopy (FCS). We employ FCS to make sensitive measurements of bilayer adsorption and compare the adsorption of a small molecular probe with that of a single-stranded, dye-labeled DNA molecule. From these FCS studies, adsorption isotherms can be obtained that report on the relative binding strengths of the two systems. The results show that DNA binds much more strongly to the exterior surface of positively charged catanionic vesicles, and can even stabilize vesicles at very low surfactant concentrations near the critical aggregation concentration (cac).

Biomimetic organic–inorganic nanocomposite coatings for titanium implants

A new class of organic-inorganic nanocomposites, to be used as coatings for surface enhancement of metal implants for bone replacement and repair, has been prepared by a biomimetic three-step procedure: (1) embedding amorphous calcium phosphate (ACP) particles between organic polyelectrolyte multilayers (PE MLs), (2) in situ transformation of ACP to octacalcium phospate (OCP) and/or poorly crystalline apatite nanocrystals by immersion of the material into a metastable calcifying solution (MCS) and (3) deposition of a final PE ML. The organic polyelectrolytes used were poly-L-glutamic acid and poly-L-lysine. The nanocomposites obtained by each successive step were characterized by scanning electron microscopy, energy dispersive X-ray analysis (EDS), and XRD, and their suitability as coatings for metal implants was examined by mechanical and in vitro biological tests. Coatings obtained by the first deposition step are mechanically unstable and therefore not suitable. During the second step, upon immersion into MCS, ACP particles were transformed into crystalline calcium phosphate, with large platelike OCP crystals as the top layer. After phase transformation, the nanocomposite was strongly attached to the titanium, but the top layer did not promote cell proliferation. However, when the coating was topped with an additional PE ML (step 3), smoother surfaces were obtained, which facilitated cell adhesion and proliferation as shown by in vitro biological tests using primary human osteoblasts (HO) directly seeded onto the nanocomposites. In fact, cell proliferation on nanocomposites with top PE MLs was far superior than on any of the individual components and was equivalent to proliferation on the golden standard (plastic).

Phosphorus Recovery from Poultry Litter

Land application of large amounts of poultry litter is an environmental concern often associated to excess phosphorus (P) in soils and potential pollution of water resources. Recovery of P from poultry litter waste is an attractive approach when on-farm application of poultry litter is not an option. A treatment process, called quick wash, was developed for extraction and recovery of P from poultry litter and animal manure solids. The quick wash process consists of three consecutive steps: (1) P extraction, (2) P recovery, and (3) P recovery enhancement. In step 1, organically bound P is converted to soluble P by rapid hydrolysis reactions using selected mineral or organic acids. This step also releases P from insoluble inorganic phosphate complexes. The washed litter residue is subsequently separated from the liquid extract and dewatered; unnecessary carbon (C) and nitrogen (N) transformations are prevented by dewatering the residue. In step 2, P is precipitated by addition of lime to the liquid extract to form an alkaline earth metal-containing P product. In step 3, an organic poly-electrolyte is added to enhance the P grade of the product. This approach of extracting and recovering P from poultry litter using the quick wash process produces a final P product that can be reused as fertilizer. In addition, the remaining washed solid residue has a more balanced N to P (N:P) ratio that is more environmentally safe for land application and use by crops. As an alternative, washed poultry litter residue can be used for energy production or reutilized as bedding, especially in areas where bedding material is in short supply.

Does water swell the ordered domains in polyelectrolyte/clay multilayers?

AbstractX-ray diffraction has been used to study the sorption of water by multilayer films containing ordered stacks of alternating layers of an organic polyelectrolyte and individual platelets of a smectite. The position and shape of the 001 reflections due to the ordered polyelectrolyte/platelet stacks were essentially the same when in air at low relative humidity (23–25% RH) and under water. These data indicate that swelling occurs exclusively in X-ray amorphous regions within the film, and that the ordered polyelectrolyte/clay domains themselves are not ‘swellable’ by water.