Commercial Polyelectrolyte Research Articles

Structuring liquids through solvent-assisted interfacial association of oppositely charged polyelectrolytes and amphiphiles

HypothesisSculpting liquids into different shapes is usually based on the interfacial interactions of functionalized nanoparticles or polymers with specific ligands, leading to exciting material properties due to the combination of the mobility of liquid components with the solid-like characteristic of the arrested liquid/liquid interface. There is an intense interest in novel structured liquids produced from simple compounds with versatile application potentials. Complexes of oppositely charged commercial polyelectrolytes and traditional aliphatic surfactants are good candidates for this goal since they reveal rich structural features and could adsorb at various interfaces. However, they have not been applied yet for structuring liquids. ExperimentsThe interfacial interactions and film formation between aqueous sodium poly(styrene) sulfonate solutions (NaPSS) and hexadecylamine (HDA) solutions in various alkanols were investigated by surface tension measurements and ATR-IR spectroscopy. 3D printing experiments also assessed the robustness of the formed films. FindingsArrested fatty alcohol/water interfaces were formed due to the interfacial association of NaPSS, HDA, and alkanol molecules, which also act as cosurfactants in the surface region. These solid films enable the synthesis of temperature-sensitive all-in-liquid constructs and offer alternatives to bulk polyion/mixed surfactant assemblies prepared earlier through numerous synthesis steps.

A new simpler and reliable method for determining mineral oil in sewage sludge: Influence of biogenic compounds for the quantitative analysis of C10–C40 hydrocarbons

The characterization of organic contaminants in sewage sludge is a fundamental step to address the relevant most appropriate management practice. In this perspective, C10–C40 hydrocarbon content was considered in Italy a crucial parameter to be considered, in spite of its irrelevance in the literature. The very complex mixture of organic substances of both biogenic and anthropogenic origin the sludge is made up of makes sewage sludge a matrix of uniqueness nature, and the analytic determination of hydrocarbon content through conventional procedures may be subjected to overestimation. In this work, optimization of two conventional protocols for the determination of mineral oil (EN14039 and IRSA CNR gravimetric method) were run with attention to anthropogenic compounds potentially affecting the C10–C40 mineral hydrocarbons determination. Effects from the first manipulations of sewage sludge samples to extraction procedure and clean-up operations were investigated.A new simple procedure was set up and tested on 30 samples from different wastewater treatment plants (WWTPs). Through a simple extraction with hexane (12 mL per 2 g of dried sludge, acidified with HCl conc.) at room temperature for 2 h, followed by a clean-up on Florisil column (10 mL–2 g) a confident determination of C10–C40 were obtained with respect to conventional optimized procedures. Variability within the range 0.06–9.49% was calculated with respect to the average value determined using three different methods, with an average value of 2.48 ± 2.37%, demonstrating the robustness of the determination. Up to 3% of the total hydrocarbons were identified as naturally occurring, namely terpenes, squalenes and deoxygenized sterols, passed through the clean-up Florisil column. A significant incidence (up to 75%) of the final overall C10–C40 content was found to be related to the C10–C20 component, originally present in the commercial polyelectrolytes in emulsion, widely used for conditioning before mechanical dewatering.

Diallyldimethylammonium Chloride (DADMAC) in Water Treated with Poly-Diallyldimethylammonium Chloride (PDADMAC) by Reversed-Phase Ion-Pair Chromatography—Electrospray Ionization Mass Spectrometry

Poly-diallyldimethylammonium (PDADMAC) chloride is a flocculant agent extensively used in water clarification treatments. Commercial polyelectrolyte formulations often contain residual monomer (DADMAC), reaction by-products and other reactants as contaminants that could potentially affect human health. In the present study, we optimized an analytical method based on reversed-phase ion-pair chromatography coupled with mass spectrometry for quantifying ultra-trace levels of DADMAC, without preliminary treatments, in drinking water distributed by the Palermo aqueduct. The method was validated in terms of accuracy (recovery between 80 to 120%), precision (RSD < 10%), linearity range (from 0.5 to 15 µg/L), limit of quantification and limit of detection (LOQ 0.42 µg/L and LOD 0.12 µg/L). DADMAC was detected in all analysed water samples and the concentration ranged from 1.2 to 3.8 µg/L whit a mean value of 1.7 µg/L. To the best of our knowledge, this paper represents the first study concerning DADMAC concentration in water samples collected in Italy and, in this context, this paper can be considered very interesting when comparing future data on DADMAC monitoring in water. Moreover, this is one of a few cases where DADMAC was found in drinking water.

Dealcoholization of Unfiltered and Filtered Lager Beer by Hollow Fiber Polyelectrolyte Multilayer Nanofiltration Membranes-The Effect of Ion Rejection.

Membrane-based beverage dealcoholization is a successful process for producing low- and non-alcoholic beer and represents a fast-growing industry. Polyamide NF and RO membranes are commonly applied for this process. Polyelectrolyte multilayer (PEM) NF membranes are emerging as industrially relevant species, and their unique properties (usually hollow fiber geometry, high and tunable selectivity, low fouling) underlines the importance of testing them in the food industry as well. To test PEM NF membranes for beer dealcoholization at a small pilot scale, we dealcoholized filtered and unfiltered lager beer with the tightest available commercial polyelectrolyte multilayer NF membrane (NX Filtration dNF40), which has a MWCO = 400 Da, which is quite high for these purposes. Dealcoholization is possible with a reasonable flux (10 L/m2h) at low pressures (5-8.6 bar) with a real extract loss of 15-18% and an alcohol passage of ~100%. Inorganic salt passage is high (which is typical for PEM NF membranes), which greatly affected beer flavor. During the dealcoholization process, the membrane underwent changes which substantially increased its salt rejection values (MgSO4 passage decreased fourfold) while permeance loss was minimal (less than 10%). According to our sensory evaluation, the process yielded an acceptable tasting beer which could be greatly enhanced by the addition of the lost salts and glycerol.

Application of New Polymer Flocculants in Industrial Wastewater Treatment

Polymer flocculants are used in wastewater treatment processes, and the necessity and universality of their use result from changes in production technologies, also causing variability in the parameters of treated wastewater. Industrial wastewater contains a substrate that is difficult to biodegrade (BOD5/COD < 0.02), and the presence of toxic compounds makes it necessary to treat them in many stages before discharging them to the receiver or reusing. The study aimed to assess the possibility of using a new generation flocculent to support coagulation. The research was conducted on mine water originating from hard coal mines and on treated coke wastewater from the biological sewage treatment plant. The synthesis of copolymers of acrylamide with acrylic acid and acrylamide with acrylonitrile allowed the extraction of effective products – flocculents with specific properties, supporting the coagulation process and reducing the parameters of contaminants in treated industrial wastewater. Compared to commercial polyelectrolyte Praestol, copolymers of acrylamide with acrylic acid removed turbidity more effectively than acrylamide-acrylonitrile copolymers.

Rational Design of a Zr-MOF@Curli-Polyelectrolyte Hybrid Membrane toward Efficient Chemical Protection, Moisture Permeation, and Catalytic Detoxification.

Developing high-performance protective materials is important for soldiers and civilians who are exposed to the atmosphere of highly toxic chemical warfare agents (CWAs). Polyelectrolyte membranes are promising candidates with excellent chemical resistance and moisture permeability, but they cannot efficiently degrade CWAs. Here, we design and prepare a hybrid membrane through in situ growth of catalytically active zirconium-based metal-organic frameworks (Zr-MOFs) on a polyelectrolyte membrane mediated by biofilm-inspired curli nanofibers (CNFs). Superior to the bare polyelectrolyte membrane, the prepared MOF-808@CNF-PQ hybrid membrane exhibits improved rejection of the nerve agent simulant dimethyl methyl phosphonate (DMMP) vapor and permeation of the water vapor by 113 and 45%, respectively. The water/DMMP selectivity of the hybrid membrane reaches 498.6, approximately 13 times that of the commercial polyelectrolyte membrane Nafion 117. In addition, the hybrid membrane possesses appreciable catalytic activity for the hydrolysis of the nerve agent simulant dimethyl 4-nitrophenyl phosphate (DMNP) with a half-life of ∼38 min. Nanomechanical characterization results based on atomic force microscopy (AFM) techniques demonstrate the critical role of CNFs in mediating Zr-MOF nucleation and the dominant effect of electrostatic interactions on self-assembly of CNFs on polyelectrolyte base. It is also confirmed that the Zr-MOF toppings serve as the key components in physically adsorbing and chemically degrading the DMNP molecules through multiple strong intermolecular interactions. Our work offers a rational strategy to develop advanced membranes toward efficient chemical protection, moisture permeation, and catalytic detoxification against CWAs.

Buffering Volume Change in Solid-State Battery Composite Cathodes with CO2-Derived Block Polycarbonate Ethers.

Polymers designed with a specific combination of electrochemical, mechanical, and chemical properties could help overcome challenges limiting practical all-solid-state batteries for high-performance next-generation energy storage devices. In composite cathodes, comprising active cathode material, inorganic solid electrolyte, and carbon, battery longevity is limited by active particle volume changes occurring on charge/discharge. To overcome this, impractical high pressures are applied to maintain interfacial contact. Herein, block polymers designed to address these issues combine ionic conductivity, electrochemical stability, and suitable elastomeric mechanical properties, including adhesion. The block polymers have “hard-soft-hard”, ABA, block structures, where the soft “B” block is poly(ethylene oxide) (PEO), known to promote ionic conductivity, and the hard “A” block is a CO2-derived polycarbonate, poly(4-vinyl cyclohexene oxide carbonate), which provides mechanical rigidity and enhances oxidative stability. ABA block polymers featuring controllable PEO and polycarbonate lengths are straightforwardly prepared using hydroxyl telechelic PEO as a macroinitiator for CO2/epoxide ring-opening copolymerization and a well-controlled Mg(II)Co(II) catalyst. The influence of block polymer composition upon electrochemical and mechanical properties is investigated, with phosphonic acid functionalities being installed in the polycarbonate domains for adhesive properties. Three lead polymer materials are identified; these materials show an ambient ionic conductivity of 10 –4 S cm–1, lithium-ion transport (tLi+ 0.3–0.62), oxidative stability (>4 V vs Li+/Li), and elastomeric or plastomer properties (G′ 0.1–67 MPa). The best block polymers are used in composite cathodes with LiNi0.8Mn0.1Co0.1O2 active material and Li6PS5Cl solid electrolyte–the resulting solid-state batteries demonstrate greater capacity retention than equivalent cells featuring no polymer or commercial polyelectrolytes.

Highly Conductive Polyelectrolyte Membranes Poly(vinyl alcohol)/Poly(2-acrylamido-2-methyl propane sulfonic acid) (PVA/PAMPS) for Fuel Cell Application.

In this study, chemically cross-linked PVA/PAMPS membranes have been prepared to be used in direct methanol fuel cells (DMFCs). The structural properties of the resultant membrane were characterized by use FTIR and SEM. Additionally, their thermal stability was assessed using TGA. Moreover, the mechanical properties and methanol and water uptake of membrane was studied. The obtained FTIR of PVA/PAMPS membranes revealed a noticeable increase in the intensity of adsorption peaks appearing at 1062 and 1220 cm−1, which correspond to sulfonic groups with the increasing proportion of PAMPS. The thermograms of these polyelectrolyte membranes showed that their thermal stability was lower than that of PVA membrane, and total weight loss gradually decreased with increasing the PAMPS. Additionally, the functional properties and efficiency of these polyelectrolyte membranes were significantly improved with increasing PAMPS proportion in these blends. The IEC of polymer blend membrane prepared using PVA/PAMPS ratio of 1:1 was 2.64 meq/g. The same membrane recorded also a methanol permeability coefficient of 2.5 × 10−8 cm2/s and thus, its efficiency factor was 4 × 105 greater than that previously reported for the commercial polyelectrolyte membrane, Nafion® (2.6 × 105). No significant increase in this efficiency factor was observed with a further amount of PAMPS. These results proved that the PVA:PAMPS ratio of 1:1 represents the optimum mass ratio to develop the cost-effective and efficient PVA/PAMPS blend membranes for DMFCs applications.

Effect of external salt addition on the structural, morphological and electrochemical properties of flexible PEDOT:PSS based LbL multilayered films

This article concerns with the effect of external salt addition on the structural, morphological and electrochemical properties of linear poly(ethylene imine) (LPEI) and poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS) based LbL assembled films that is a cathodic color changing electrode for electrochromic device. For this purpose, cationic and anionic commercial polyelectrolytes (PEs) with/without 0.3 M NaCl were deposited on PET-ITO with automatized dip coating system. From QCM-D, it was found that the multilayer deposition became larger for LbL assembled films obtained from salt-free PEs. While the dissipation change (ΔD) of (LPEI/PEDOT:PSS)10/NaCl (150 × 10−6) exhibited relatively soft/flexible structure compared to the (LPEI/PEDOT:PSS)10 (110 × 10−6), ΔD changes became more obvious during PEDOT:PSS adsorption. Furthermore, it was determined that the film thickness and surface roughness values were highly dependent on the number of deposited bilayers whereas they dropped with the addition of salt to LPEI. The root mean square roughness (Rq) of (LPEI/PEDOT:PSS)10, (LPEI/PEDOT:PSS)20 and (LPEI/ PEDOT:PSS)40 were found to be 28 nm, 41.7 nm and 61.5 nm, respectively, while Rq of (LPEI/PEDOT:PSS)20/NaCl was 14.2 nm. All LbL mutilayered films had hydrophilic character and the average contact angle value of (LPEI/PEDOT:PSS)20/NaCl was found to be 66° due to the presence of salt within the multilayers. In addition, ion transport rate increased if the external salt was added to PE. Concerning the salt effect on colorancy of LbL multilayers, all films showed reversible color changes between blue and transparent/pale blue and (LPEI/PEDOT:PSS)20 exhibited darker blue in the colored state whereas (LPEI/PEDOT:PSS)20/NaCl had more translucent in the bleached state.

Sewage Sludge Conditioning using Opuntia Ficus Indica Juice

This work aimed to study the possibility of using plant matter, Opuntia ficus indica juice (OFIJ), for conditioning the Beni-Messous (Algiers) wastewater treatment plant sludge. The optimum dosage of OFIJ was found to be 0.4 g⋅kg‑1 of dry matter, for which the residual turbidity, the dryness of the filtration cake, and the specific resistance of filtration were found to be 2.5 NTU, 24% and 0.13⋅1012m⋅kg‑1, respectively. The results obtained with OFIJ are also compared with those of commercial polyelectrolytes such as Chimfloc C4346, a cationic polymer, Sedipur NF 400, a non-ionic polymer, and Sedipur AF 102, an anionic polymer, and inorganic conditioners such as FeCl3 and Al2(SO4)3. OFIJ proved to be the most efficient because the optimum dosage was found to be 0.4 g⋅kg‑1 of dry matter for OFIJ whereas for Chimfloc C4346, FeCl3 and Al2(SO4)3 the optimum doses were be found to be 0.8, 80 and 60 g⋅kg‑1. Based on the obtained results, OFIJ could be used as a natural conditioner in sewage sludge treatment.

Network Structure and Inhomogeneities of Model and Commercial Polyelectrolyte Hydrogels as Investigated by Low-Field Proton NMR Techniques

This work presents an experimental study of the network structure of swollen, charged hydrogels. We provide an in-depth comparison of two proton low-field NMR methods, i.e., transverse relaxation and double-quantum spectroscopy, that are both sensitive to residual orientation correlations of the network chain segments. The results are in both cases analyzed by help of integral inversion techniques, and both methods are demonstrated to provide comparable results despite the more qualitative nature of the transverse relaxation. We investigate model samples that are similar to commercial superabsorber materials based on partly neutralized and chemically cross-linked poly(acrylic acid) as prepared by free radical polymerization. The degree of cross-linking and the monomer concentration are varied during synthesis. Both parameters are found to affect the network structure and the amount of elastically inactive defects in a systematic way, and a comparison with commercial samples with homogeneous or purposely inhomogeneous core–shell structures proves that the cross-linking bimodality of the latter is readily revealed despite the rather large intrinsic inhomogeneity of the swollen gels.

Self-Assembly of Stiff, Adhesive and Self-Healing Gels from Common Polyelectrolytes

Underwater adhesion has numerous potential medical, household, and industrial applications. It is typically achieved through covalent polymerization and cross-linking reactions and/or the use of highly specialized biological or biomimetic polymers. As a simpler alternative to these covalent and biomimetic strategies, this article shows that stiff, gel-like complexes that adhere to various substrates under water can also be prepared through the ionic cross-linking of common, commercial polyelectrolytes. The gels form spontaneously when synthetic polycations, such as poly(allylamine) (PAH), are mixed with strongly binding multivalent anions, pyrophosphate (PPi) and tripolyphosphate (TPP). The PAH/PPi and PAH/TPP gels exhibit very high storage moduli (G∞′ ≈ 400 kPa), self-heal when torn, and adhere to both hydrophilic and hydrophobic substrates under water (with short-term tensile adhesion strengths of 350–450 kPa). Furthermore, these gels can be dissolved on demand (if adhesion needs to be reversed) by changing the ambient pH, which controls the ionization state of the polyelectrolyte and ionic cross-linker. These properties suggest that synthetic polycations cross-linked with PPi and TPP ions could provide a simple, inexpensive, and scalable platform for underwater adhesion.

Improving the Efficiency of a Coagulation-Flocculation Wastewater Treatment of the Semiconductor Industry through Zeta Potential Measurements

Efficiency of coagulation-flocculation process used for semiconductor wastewater treatment was improved by selecting suitable conditions (pH, polyelectrolyte type, and concentration) through zeta potential measurements. Under this scenario the zeta potential,ζ, is the right parameter that allows studying and predicting the interactions at the molecular level between the contaminants in the wastewater and polyelectrolytes used for coagulation-flocculation. Additionally, this parameter is a key factor for assessing the efficiency of coagulation-flocculation processes based on the optimum dosages and windows for polyelectrolytes coagulation-flocculation effectiveness. In this paper, strategic pH variations allowed the prediction of the dosage of polyelectrolyte on wastewater from real electroplating baths, including the isoelectric point (IEP) of the dispersions of water and commercial polyelectrolytes used in typical semiconductor industries. The results showed that there is a difference between polyelectrolyte demand required for the removal of suspended solids, turbidity, and organic matter from wastewater (23.4 mg/L and 67 mg/L, resp.). It was also concluded that the dose of polyelectrolytes and coagulation-flocculation window to achieve compliance with national and international regulations as EPA in USA and SEMARNAT in Mexico is influenced by the physicochemical characteristics of the dispersions and treatment conditions (pH and polyelectrolyte dosing strategy).

Alumina/MWCNTs composites by aqueous slip casting and pressureless sintering

Abstract Slip casting of stabilized aqueous suspensions followed by pressureless sintering was used for preparation of dense Al 2 O 3 /MWCNTs composites. The suspensions were stabilized by commercial polyelectrolyte dispersant Darvan C–N. In order to increase the stability, the pH value of the suspension was adjusted to ∼10. At this pH the highest ζ-potential values of the alumina powder and of the MWCNTs functionalised in boiling nitric acid were achieved. Two different agents, namely ammonium hydroxide and sodium hydroxide, were used for the pH adjustment. Their influence on the viscosity of suspensions and on consolidation and densification behaviour of the Al 2 O 3 /MWCNT composites was evaluated. The effect of ammonium hydroxide was more pronounced, as confirmed by lower viscosity of the suspension, higher sintered density, and fine-grained microstructure of the sintered composites. The Al 2 O 3 /t-MWCNTs composites with 0.1 wt% of the MWCNTs, with 99.9% relative density, the mean size of alumina grains ∼1 μm, and homogeneously distributed carbon nanotubes were prepared by the pressureless sintering at 1500 °C.

Ultrathin tunable ion conducting nanomembranes for encapsulation of sulfur cathodes

Membranes are of interest for a wide variety of applications such as gas separation, water desalination, fuel cells and batteries. Because the flux across a membrane scales inversely with the membrane thickness, a thick membrane is required to achieve high selectivity, at the expense of permeability. New ultrathin membranes which promise to offer high selectivity and high permeability are highly desirable. Elemental sulfur can provide five times higher capacity than existing Li-ion cathode materials based on transition metal oxides or phosphates. Various problems have hindered the practical use of this highly attractive cathode including the insulating nature of sulfur which retards its reduction and poor electrode stability resulting in an irreversible capacity loss due to polysulfide migration from the cathode to the anode. Here we show the proof of concept for a 5 nm multilayer membrane self-assembled from commercial polyelectrolytes to encapsulate a carbon/sulfur composite and maintain the performance even at discharge rates five times more rapid than its non-encapsulated counterpart.

Flocculation efficiency of modified water soluble chitosan versus commonly used commercial polyelectrolytes

Abstract Aim of this work was to evaluate the flocculation efficiency of a modified, water soluble chitosan versus various commercial products such as: chitosan, PolyDADMAC and positively charged polyacrylamide. The flocculation properties were investigated in dispersions of the clay type “Blauton” by means of turbidity measurements, colloid titration and measurements of the floc size. It was found that flocculation occurs even before the Blauton surface charge neutralization is achieved. The modified chitosan was more effective than the commercial one in Blauton's settling. Modified chitosan in comparison to the commercial products demonstrated not only a wider flocculation window, but also a higher efficiency since lower amounts of polymer were required for the flocculation of Blauton. Finally, the use of modified chitosan resulted in an increase of the critical polymer concentration above which restabilization of Blauton occurs.

Performance optimization of coagulation/flocculation in the treatment of wastewater from a polyvinyl chloride plant

This paper presents results of an experimental study of coagulation/flocculation process of wastewater generated from a polyvinyl chloride (PVC) plant. The wastewater contains fine chlorine-based solid materials (i.e. latex). Experiments were carried out using a model wastewater which is chemically identical to the actual plant but is more consistent. Inorganic ions (Al 2(SO 4) 3, FeCl 3 and CaCl 2) and a water soluble commercial polyelectrolyte (PE) were added to the wastewater sample. Coagulation efficiency was determined by measuring both the turbidity of the supernatants and the relative settlement of the flocs in the jar test. It was found that aluminum and ferric ions were more efficient than calcium ions as coagulants. The addition of polyelectrolyte was found to improve substantially the coagulation/flocculation process. It was found that the (Al 2(SO 4) 3) combined with the polyelectrolyte at certain pH and agitation speed gave the best results compared to calcium chloride or ferric chloride when combined with the same concentration of polyelectrolyte. Only 0.0375 g of a solution of (0.5% Al 2(SO 4) 3) was required to coagulate the model wastewater. Ferric chloride (2.5% FeCl 3) combined with the polyelectrolyte, on the other hand, required 0.1 g while the optimum turbidity is almost the same. As for calcium chloride (2.5% CaCl 2) it was found to be the least effective. The coagulation/flocculation process was found to be dependent on both pH and the agitation speed.

Treatment of olive mill effluents by coagulation–flocculation–hydrogen peroxide oxidation and effect on phytotoxicity

The pre-treatment of olive mill effluents (OME) by means of coagulation–flocculation coupling various inorganic materials and organic poly-electrolytes was investigated. Tests were conducted with two different OME with chemical oxygen demand (COD) contents of 61.1 and 29.3 g/L, total suspended solids (TSS) of 36.7 and 52.7 g/L and total phenolic contents (TP) of 3.5 and 2.5 g/L, respectively. Inorganic materials such as lime, iron, magnesium and aluminum as well as four cationic and two anionic commercial poly-electrolytes were employed either alone or in various combinations and screened with respect to their efficiency in terms of TSS, TP and COD removal, the amount of sludge produced and the phytotoxicity of the resulting liquid to lettuce seeds. Coupling lime or ferrous sulphate (in the range of several g/L) with cationic poly-electrolytes (in the range of 200–300 mg/L) led to quantitative TSS removal, while COD and TP removal varied between about 10–40% and 30–80%, respectively, depending on the materials and the effluent in question; separation efficiency generally decreased with decreasing coagulant and/or flocculant concentration. To enhance organic matter degradation, iron-based coagulation was coupled with H 2O 2, thus simulating a Fenton reaction and this increased COD reduction to about 60%. The original, untreated OME was strongly phytotoxic to lettuce seeds even after several dilutions with water; however, phytotoxicity decreased considerably following treatment with lime and cationic poly-electrolytes; this was attributed to the removal of phenols and other phytotoxic species from the liquid phase.

Studies on flocculation of clay suspension by polyacrylamide

Abstract The flocculation of dilute pottery clay suspension using polyacrylamide (PAM) was investigated. Different molecular weight PAMs were synthesized by free-radical polymerization initiated with the persulfate-bisulfate redox pair. The synthesized polyelectrolytes (PAM1, PAM2 and PAM3, from low to high molecular weight) and a commercial one (C-492) were used for flocculation studies. The flocculating performance of polyelectrolytes was measured on 3% w/v pottery clay suspension using settling tests and turbidity measurements. PAM2 at pH 5.0 showed the maximum settling rate, which is nearly three times that of C-492, and it also showed a better turbidity reduction. Molecular weight is the key factor in influencing settling and turbidity reduction. In the present study, increasing molecular weight enhanced settling rate and turbidity reduction to a certain level beyond which there is a decrease, suggesting an optimum molecular weight for the given application. PAM2, a medium molecular weight polyelectrolyte (2.0·105 g/mol) has shown better performance than PAM1 (1.3·105 g/mol), PAM3 (6.0·105 g/mol) and the commercial polyelectrolyte C-492 (molecular weight of order 106).

An Algal Removal Using a Combination Of Flocculation and Flotation Processes

The paper describes certain facets of the removal of the algae (Scenedesmus quadricauda) from water, using a froth flotation separation method, in conjunction with two types of surfactants, (cetyltrimethylammonium bromide) CTAB and (sodium dodecylsulfate) SDS. A 90% algal removal efficiency was achieved when 100 mg l-1 of CTAB was used whereas for the SDS solutions, the same concentration gave, by comparison, a very poor algal removal efficiency. An addition of 1 mg l–1 of a commercial cationic polyelectrolyte, which was the optimal concentration as was evident from the zeta potential and the particle size distribution measurements, prior to the SDS addition resulted in a formation of algal flocs and consequently a substantial improvement in the extent of the algal removal. A 50 mg l-1 solution of SDS was found to be the optimal concentration to completely remove these algal flocs from water. The amount of water removed along with the algal flocs, produced using 1 mg l-1 of the commercial polyelectrolyte and subsequently removed using SDS, was comparatively lower than that removed with the algal cells when CTAB was used as the 'collector'. It was generally found, in this study, that an addition of the polyelectrolyte improved the removal efficiencies and the rate of separation and also decreased the amount of the associated water removed along with the algal sludge.