Synthetic Cationic Polyelectrolytes Research Articles

Polyelectrolyte‐controlled visible light catalytic reduction of nitrobenzene

To study the effect of cationic polyelectrolytes on the photoreduction of nitrobenzene over TiO2, a sequence of synthetic cationic polyelectrolytes (SCPs) containing acrylamide (AAm) and 2‐(dimethylamino)ethyl acrylate methochloride (DAEA) using various AAm:DAEA molar ratios (50:50, 55:45, 60:40, 70:30, and 85:15) were synthesized and named as PEA, PEB, PEC, PED, and PEE, respectively. According to the obtained monomer reactivity ratios, the SCPs with a range from medium to high molecular weights (2.11×105 ≤ Mv ≤ 1.22 ×106 g/mol) were obtained. Then the influence of the SCPs and the other polyelectrolytes such as Zetag 7563 (a commercial grade of cationic polyelectrolyte) and poly(vinylsulfate) potassium salt (PVSK) as an anionic polyelectrolyte on the photoreduction of nitrobenzene over TiO2 under 400 nm LED irradiation was investigated. Zetag 7563 was not an appropriate polyelectrolyte to enhance the photoreduction of nitrobenzene due to its high Mv, and having high entanglement of polymer chains. By the addition of PVSK anionic polyelectrolyte, the conversion of nitrobenzene to aniline decreased; the PVSK has a probably greater tendency than nitrobenzene to be absorbed on the surface of TiO2 (PVSK reduces the adsorption of nitrobenzene on the surfaces of TiO2 due to the electrostatic interactions with TiO2). Simultaneous use of TiO2 with 0.01 g of PEB (with medium Mv and 4.4 meq/g charge density), led to an increase in the nitrobenzene photoreduction (95% conversion) in comparison with application of bare TiO2 (53% conversion). It supposes that the selection of appropriate SCPs can facilitate the access of reactants to each other and enhance the nitrobenzene photoreduction.

Highly Porous Cationic Polyelectrolytes via Oil-in-Water Concentrated Emulsions: Synthesis and Adsorption Kinetic Study.

This work merges the fields of highly porous polymers (polymerized high internal phase emulsions, polyHIPEs) and synthetic cationic polyelectrolytes and introduces a new approach toward the synthesis of highly porous cationic polyelectrolytes. Cationic polyelectrolytes based on (3-acrylamidopropyl)-trimethylammonium chloride (AMPTMA) were synthesized directly through the oil-in-water HIPEs. The resulting polyelectrolyte-based polyHIPEs are distinguished by the highly porous morphology as well as high concentration and accessibility of the cationic N-quaternized functional groups. The most efficient AMPTMA-based polyelectrolyte polyHIPE exhibits the total ion-exchange capacity of 3.53 mmol of AgNO3 per gram of dry resin and the water uptake of up to 95 g·g-1, which is a great improvement as compared to the state-of-the-art of polyHIPE absorbents bearing cationic moieties. Results of erythrosine dye adsorption show that chemisorption is a rate-determining step because adsorption follows the pseudo-second-order kinetic model. Multilinearity of the Weber and Morris plots assumes that more than one regime is involved in the diffusion of the erythrosine dye molecules into the polyHIPE structure with the diffusion in between the swollen polymer chains as a rate-limiting step.

Polycomplexes of Bovine Serum Albumin with Poly[2-Methacryloyloxy) Ethyl]Trimethyl Ammonium Chloride

Complex formation between bovine serum albumin and water-soluble synthetic cationic polyelectrolyte poly[2-methacryloyloxy)ethyl]trimethyl ammonium chloride has been studied in aqueous solutions by turbidimetric and viscometric methods. It was found that the structure of polycomplex is compact and its stability strongly depends on the environment. Formation of insoluble polycomplexes is observed in solutions with low ionic strength and pH, higher than 5.0. This pH value corresponds to the isoelectric point of the protein, so at lower pH the biopolymer macromolecules gain the positive charge and not able to be bound by the positively charged macromolecules of poly[2-methacryloyloxy)ethyl]trimethyl ammonium chloride. An increase of pH within 5.0-11.0 leads to further stabilization of polycomplex because of appearance of additional negative charges on biomacromolecules, caused by ionization of acidic groups. It was found that the main forces, which are responsible for the complexation, are electrostatic interactions.<br />The intensity of the complexation is dependent on the solution concentration, pH and ionic strength. In solutions with high ionic strength (I=0.2, 1.0) the mixing of the reagents does not lead to the formation of insoluble polycomplexes. The observed dependence is connected with the screening of electrostatic interactions between macromolecules of the biopolymer and synthetic polyelectrolyte by small ions present in solution.

Chitosan use in chemical conditioning for dewatering municipal-activated sludge.

This work aims to evaluate the potential use of chitosan as an eco-friendly flocculant in chemical conditioning of municipal-activated sludge. Chitosan effectiveness was compared with synthetic cationic polyelectrolyte Sedipur CF802 (Sed CF802) and ferric chloride (FeCl₃). In this context, raw sludge samples from Beni-Messous wastewater treatment plant (WWTP) were tested. The classic jar test method was used to condition sludge samples. Capillary suction time (CST), specific resistance to filtration (SRF), cakes dry solid content and filtrate turbidity were analyzed to determine filterability, dewatering capacity of conditioned sludge and the optimum dose of each conditioner. Data exhibit that chitosan, FeCl₃and Sed CF802 improve sludge dewatering. Optimum dosages of chitosan, Sed CF802 and FeCl₃allowing CST values of 6, 5 and 9 s, were found, respectively, between 2-3, 1.5-3 and 6 kg/t ds. Both polymers have shown faster water removal with more permeable sludge. SRF values were 0.634 × 10¹², 0.932 × 10¹² and 2 × 10¹² m/kg for Sed CF802, chitosan and FeCl₃respectively. A reduction of 94.68 and 87.85% of the filtrate turbidity was obtained with optimal dosage of chitosan and Sed CF802, respectively. In contrast, 54.18% of turbidity abatement has been obtained using optimal dosage of FeCl₃.

Salt- and pH-induced desorption: Comparison between non-aggregated and aggregated mussel adhesive protein, Mefp-1, and a synthetic cationic polyelectrolyte

Mussel adhesive proteins are of great interest in many applications due to their ability to bind strongly to many types of surfaces under water. Effective use such proteins, for instance the Mytilus edulis foot protein – Mefp-1, for surface modification requires achievement of a large adsorbed amount and formation of a layer that is resistant towards desorption under changing conditions. In this work we compare the adsorbed amount and layer properties obtained by using a sample containing small Mefp-1 aggregates with that obtained by using a non-aggregated sample. We find that the use of the sample containing small aggregates leads to higher adsorbed amount, larger layer thickness and similar water content compared to what can be achieved with a non-aggregated sample. The layer formed by the aggregated Mefp-1 was, after removal of the protein from bulk solution, exposed to aqueous solutions with high ionic strength (up to 1M NaCl) and to solutions with low pH in order to reduce the electrostatic surface affinity. It was found that the preadsorbed Mefp-1 layer under all conditions explored was significantly more resistant towards desorption than a layer built by a synthetic cationic polyelectrolyte with similar charge density. These results suggest that the non-electrostatic surface affinity for Mefp-1 is larger than for the cationic polyelectrolyte.

Formation of zinc sulfide and hydroxylapatite nanoparticles in polyelectrolyte-modified microemulsions

The paper is focused on the formation of nanoparticles, i.e., zinc sulfide (ZnS) and hydroxylapatite, in a microemulsion template phase consisting of heptanol, water, and a surfactant with a sulfobetaine head group in the absence and presence of an added polyelectrolyte. In the absence of a polyelectrolyte, beside larger particles, spherical ZnS nanoparticles with a diameter below 10 nm can be redispersed after solvent evaporation. In the presence of the synthetic cationic polyelectrolyte poly(diallyldimethylammonium chloride), a reloading of the particle surface is observed, and cationic charged ZnS nanoparticles, of about 5 nm in size, can be redispersed as a main fraction. When hydroxylapatite is formed in the presence of the more stiff biopolymer chitosan hydroxylapatite, hybrid structures were formed. Transmission electron micrographs show fiber-like aggregate structures, consisting of individual small nanoparticles ordered along the polymer chain.

Organic Removals from Highly Proteinous Wastewater from Soya Milk and Tofu Manufacturing Plant

Combined wastewater from soya milk and tofu manufacturing industry was treated by physico-chemical method using conventional coagulants such as lime, alum, ferric chloride, and ferrous sulphate in combination with synthetic cationic polyelectrolyte. The wastewater samples were analyzed as per the Standard Methods and the experiments were carried out using Jar test apparatus (Phipps & Birds). The ferric chloride in combination with synthetic cationic polymer (Oxyfloc-FL-11) in the ratio of 250:20 mg L−1 resulted in very good removals of COD, BOD, and SS of 75.4, 79.8, and 96.0% respectively with complete removal of odor, color and turbidity.

The interaction of humic substances with cationic polyelectrolytes

The anionic charge carried by aquatic humic substances plays a major part in their interaction with metal ions and other cationic species. Removal of such substances by coagulation and flocculation can be, at least partly, determined by charge neutralisation. In this work, the charge densities of a commercial humic acid and an aquatic humic extract have been investigated by studying their interactions with a series of synthetic cationic polyelectrolytes. These covered a range of charge densities and molecular weights. The techniques used were colloid titration by spectrophotometry and streaming current detection, and flocculation determined by colour removal and by an optical monitoring method. For a given cationic polyelectrolyte, all four methods gave charge densities for humic substances which were in good agreement. However, systematic differences in the apparent humic charge density were found, depending on the charge density of the cationic polyelectrolyte used. With low charge density polyelectrolytes, the apparent anionic charge of the humic substances was found to be low. With higher polyelectrolyte charge densities, the apparent humic substance charge density increases and reaches a limiting value when the polyelectrolyte charge is greater than about 3 meq/g. This indicates a non-stoichiometric interaction between the anionic sites of the humic substances and the cationic charges of the low-charge polyelectrolytes. Optimum flocculation of humics occurred with less cationic charge in the case of low-charge polyelectrolytes than those with higher charge density. However, the degree of removal was considerably better in the latter case. In all cases, the molecular weight of the cationic polyelectrolytes (over a range from about 50,000 to 15 million) appeared to have no effect on the results.

Charge determination of synthetic cationic polyelectrolytes by colloid titration

The stoichiometric interaction between oppositely charged polyelectrolytes forms the basis of the technique of colloid titration. This can be used, for instance, to determine the charge density of a cationic polyelectrolyte, using an anionic polyelectrolyte of known charge density, such as potassium polyvinyl sulphate (PPVS). The technique requires a suitable method of end-point detection and there are several possibilities. In this work three methods have been investigated: visual observation of the colour change of a cationic dye ( o-toluidine blue), spectrophotometric determination of the colour change of the same dye, and electrokinetic detection of charge neutralisation, using a streaming current detector. These have been applied to a range of cationic polyelectrolytes, with different charge densities and molecular weights. In all cases, the cationic charge was due to quaternary nitrogen groups. In the case of the cationic dye, it was shown that the sharpness of the colour change depends on the charge density of the cationic polyelectrolyte. With lower charge density materials the binding to PPVS is weaker and binding of the dye to PPVS can occur before all of the polyelectrolyte charge has been neutralised. However, by carrying out titrations at several polyelectrolyte concentrations, good linear relationships were found, from which reliable charge density values could be derived. The streaming current method avoids the problem of competitive interaction of PPVS with o-toluidine blue and gives quite sharp transitions at the isoelectric point, although there was some dependence on polyelectrolyte charge density. This method gave good agreement with charge densities derived from the spectrophotometric technique. Effects of pH and ionic strength were also briefly investigated. For most of the cationic polyelectrolytes, there was some loss of charge at higher pH values, probably as a result of hydrolysis. Increasing ionic strength causes a less distinct colour change of o-toluidine blue, as a result of weaker electrostatic interactions.

Macromolecular design of cationic polyelectrolytes on the chitosan basis for achievement of high antimutagenic efficiency at gamma‐irradiation

AbstractA new approach to the problem of construction of efficient antimutagenic (at γ‐irradiation) systems has been developed on the basis of the models‐ synthetic cationic polyelectrolytes‐ polyquaternary salts of diallyldimethyl‐ammonium type.

The interaction of methyl orange and other azo-dyes with polyelectrolytes and with colloidal electrolytes in dilute aqueous solution

A detailed uv spectral investigation of the interaction of methyl orange (and other similar anionic azo-dyes) with four different synthetic cationic polyelectrolytes, with colloidal electrolytes, as well as with two proteins in dilute aqueous solutions, has been carried out. Under appropriate conditions, binding of methyl orange, ethyl orange, and butyl orange to poly( l-ornithine, poly- l-lysine), poly ( N-methylvinyl pyridinium chloride), and trimethyldodecylammonium chloride, gives rise to marked changes in the spectrum of each of the three dyes (but not of other dyes examined). These spectral changes are quite different from those which result from the binding of the azo-dyes on to the strongly ionized poly(vinylbenzyltrimethyl ammonium chloride) chains. The effects observed with the four synthetic polyelectrolytes mentioned above and with the colloidal electrolytes, are postulated to be connected with a conformational change of bound dye molecules. Interaction of methyl orange with bovine serum albumin and with lysozyme would mainly result in a partial solubilization of the dye in the hydrophobic regions of the proteins.

Playa Water Quality Changes with Time and Effects on Clarification

An estimated 2 to 5 million acre‐feet of runoff water accumulates annually in playas on the semiarid southern high plains; however, development of this large potential water source has been impeded by lack of water quality data. Most of the water is lost by evaporation, and timely utilization is essential. Therefore, a particular need exists for quality data on freshly impounded water. Water from five playas was sampled and analyzed at intervals for 24 days following runoff from a single storm. Chemical analyses showed playa waters were excellent for irrigation; however, adequate economical clarification is probably needed for such projects as direct aquifer injection. With aging, less synthetic cationic polyelectrolyte and more alum was required for water clarification. Initially low nitrate and chemical oxygen demand values decreased with time.